I created a wiki page to katix gforge for link collection.
I hope you like it. It is not sorted in any sense, but it contains lots of interesting links. A friend of mine has been sending these to me a quite long time and I thought that I could share the collection with you.
http://gforge.katix.org/gf/project/twinzygger/wiki/?pagename=MiscTechPapers
New idea:
- A body that comprises of a laminar body and wing blended together
- There is a V-tail in a blended boom
- Rear of the center section has suction slot on top side
- The boom contains a electric fan that is used for suction and additional thrust
- There are two turbocharged Rotax 912UL engines in the wings which are hidden in blended pods that continue the airfoil shape of the wing without interruption
- Both engines turn additional turbochargers which drive generators which generate electricity for the rear fan of the aircraft
Items that need to be studied:
- does pressure thrust work with this kind of shape, or does it require axisymmetric body?
- compare the drag of minimum axisymmetric body with non-blended wings to a blended wing body which has larger cross sectional area, but potentially lower wetted area.
- wing incidence relative to the center section – center section has a lower aspect ratio than the wings and what it requires to achieve optimal lift distribution in this combined case
- the achievable gain from the lack of interference drag or very small interference drag
- optimal wing loading for a combined blended wing body compared to a pod+boom+wings solution
- shark fin shape on the outer wing sections, the gain and the issues
I was looking Parson’s high transition length body in a book and thought that maybe if I modify my body shape also so that the nose becomes sharper. By sacrificing some interior space, the flow acceleration can be kept for high transition length according the book I was reading this. My modified body looks like this.
Despite the QFLR5 algorithm is not maybe designed for simulating NLF bodies (it is designed for simulating wings), the pressure distribution looks like the same as the wind tunnel data for the Parson’s body which makes me think that it might not be that much wrong.
Ever wanted a Star Trek’s computer? It is here today:
For starters, try out for example: integrate x+y^2
This service is superb.
I have been thinking this topic for quite a long time and my old conclusion was that it is not feasible. However, there is very little information about pressure suits out there, but looking at the very little there is about the old Mercury suits etc., I have got indications that actually fabrication of a partial pressure suit might be feasible. Buying one might not be feasible because of lack of availability and insane pricing.
I would like to learn more about the topic, but in the Internet at least, there is very little or nothing. If someone has some insight, please leave some comments.
A major portion of aircraft drag (in addition to the wing) is generated by the fuselage. The poor aircraft has to drag the draggy fuselage forwards. It is justified to target for reducing the fuselage drag in addition to the drag of the wings to achieve high L/D ratio and thus high efficiency and exceptional miles per gallon figure.
The idea comprises of the following claims:
- a laminar body with optimal fineness ratio for minimum drag
- a tail boom behind the optimal fineness ratio laminar pod
- electric motor (or couple of electric motors in cascade) turn
one or many ducted fans that are in cascade inside the rear of the fuselage.
The fan(s) take their air intake from the boundary layer of the fuselage.
- the fans are driven with batteries on takeoff.
- the fans are driven in cruise with electricity generated from the exhaust gas of the two gasoline engines which are mounted in wings.
- there is an additional turbine mounted in the exhaust that turns a generator rather than compressing air for the gasoline engine.
- the exhaust for the air is either in the tail boom prior to the tail or after the tail, whichever is found to provide best results.
- the fans provide suction for the fuselage boundary layer and also additional thrust for the aircraft. This configuration however, does not cause additional drag for the aircraft but reduces it.
- additional generators can be mounted to wing tip vortices so that the wing tip vortex turns the turbine blades and thus generates electricity for the fans located in the rear of the fuselage.
- the generators, battery charging and fans are computer controlled.
- the fans utilize all power that can be drawn from the exhaust gas and the wing tip turbines and thus runs at full power available to it continuously. On takeoff batteries are used to ensure high centerline thrust for the hypothetical situation where one of the gasoline engines would fail.
I found these some time ago, but now got reminded about it also on one comment to a previous post. Therefore I decided to open a new topic for it:
Goldschmied drag reduction tech papers:
http://cafefoundation.org/v2/pav_enablingtech_dragreduction.php
Interesting reading for anyone interested in achieving major breakthroughs in the fuselage drag.
New iteration of laminar body fuselage shape:
One interesting aircraft in the historical data:
Lancair Evolution
P/W Power to weight ratio 7.54 kg/kW, 12.28 lbs/hp.
W/S Wing loading 142 kg/m^2, 29.05 lbs/sqft
Stall speed 61 kts
Empty weight to gross weight ratio: 0.55
Fuel to gross weight ratio: 0.2
Aspect ratio: 10.3
Aircraft with 12.28 lbs/hp power loading and 29.05 lbs/sqft wing loading in other words can
be made to climb, and it can also meet FAR 23 in stall speed requirement (61 kts). According to an article, the LC Evolution demonstrated glide ratio of 1:22 which is amazing compared to the competition, especially achieving this with only AR=10.3.
With these parameters, a smaller Rotax powered twin aircraft would be sized as follows:
Engines: 2 x Rotax 912UL, each turbocharged at 100 hp
Gross weight: 1116 kg
Empty weight: 0.55 * 1116 kg = 613 kg
Fuel weight: 0.2 * 1116 kg = 223 kg
Fuel volume: 314 l
Wing area: 1116 kg / 142 kg/m2 = 7.75 m2
Useful load (including fuel): 503 kg
Useful load full fuel: 280 kg
Endurance: 10.4 hours
Challenges:
- achieving the stall speed of 61 kts, requires very high Clmax for the flapped airfoil
- achieving > 20 glide ratio with lower Re, requires higher AR most likely
- achieving positive climb rate with single engine
- achieve the Clmax with wings that carry two engine pods on them (blanketing potentially flap and part of the wing).
- The fuel potentially does not fit inside the wing of this low wing area.
What it shows:
- Still with this high wing loading, it would be possible to fit three adults on the plane with full fuel. The result is not at all bad compared to any production aircraft.
- Empty weight looks realistic taking in account there are two Rotax engines on the craft. It is higher than it would be if it was relatively as lightweight as a Dynaero.
Bottom line: The parameters of the Lancair Evolution are very impressive and inspiring.
Realism hits:
Reduce the wing loading to 120 kg/m2
Wing area becomes: 1116 kg / 120 kg/m2 = 9.3 m2
-> It ends up in the magic 9.3 m2 wing area I have ended up from many directions already several times before.
I have in our svn by the way a OpenOffice.org spreadsheet about historical data about the basic design parameters for aircraft. There are just couple of aircraft currently in the list, but I will add more later and also you can help, you can send me more lines to the sheet, just take the sheet as a template and fill your lines and send it to me karoliina dot t dot salminen at gmail dot com. I will copy-paste your additions to the table. I am particularly interested in fast composite aircraft and not so interested in the parameters of tube and fabric aircraft or metal aircraft (except interesting ones, like RV). All data even for fabric and tube, is welcome of course, but I wanted to let you know what I am interested in the most.
Here is the spreadsheet in OpenOffice.org format:
WeightAndBasicParametersHistoricalStatistics.ods
Here is the current version of the spreadsheet in PDF-format for quick viewing:
WeightAndBasicParametersHistoricalStatistics.pdf
I decided to do svn up for QFLR5 and was delighted that it has progressed further. I decided to try out fuselage shapes this time because it turned out that QFLR5 now allows larger airfoil thicknesses than 20%. Therefore here is a 26% fuselage shape I created today.
Here is how I started it:
1. I took NLF414F airfoil which I know to have very low drag value at 10 million reynolds number.
2. I decambered to it to zero camber
3. I changed thickness to 26%
4. I changed leading edge radius: 30% from leading edge, 0.8 ratio.
The simulation result gives very low Cd-value. The problem in reality is that because of all intersections, and a hatch where one has to enter the craft, the transition point is not that great as predicted by the program most likely.
Here is another simulation, transition forced at 40% chord. The Reynolds number is the same, 41 million with mach 0.29:
I further adjusted the leading edge radius, from the above, I reduced it to 0.8 again.
Here is the result KSNLFFUSELAGE3:
The simulated polar for the NLFFUSELAGE3:
Obviously the fuselage is supposed to be flown at zero angle of attack on cruise flight, but for slight side slip situations it is good to know how the drag rises on the fuselage. It also affects to the stability negatively (for example because the lift slope is not at all linear).
Potential improvement idea for use in non-steady flight: widen the low drag bucket a bit.
The airfoil shape as a axisymmetric fuselage (or as a generic pod, this works also as a engine pod), 3D illustration:
And this is how it looks from inside:
Structurally the pod requires thicker boom than the optimum and unfortunately the drag will be larger than the simulated one for the pod alone.
Malmin ilmailukerho (MIK) jarjestaa Malmilla SIL-luokassa 5.5.2009 aiheena lentokoneen aerodynaaminen suunnittelu. Luennoitsijana Juha Karjalainen TKK:lta. Blogin lukijat ovat lampimasti tervetulleita Malmin Ilmailukerhon jasenten lisaksi. Kieli: suomi. Tilaisuuteen on vapaa paasy.
In English: There is a lecture about aerodynamics arranged at Malmi SIL class 5th May 2009. The language in the lecture is Finnish and the lecturer is going to be Juha Karjalainen from Helsinki University of Technology.
Here is a preview version of a song I started today:
Mechanical Life Form – preview
This is not the final mix or may not have all the elements I might want to add and I may play again some parts which were poorly played. However, here is the preview. All comments are very welcome.
Here is the download link to the file.
This one is a lot louder and more energetic than the original mix. I added couple of new tracks into the mix as well. Enjoy!
Malmin ilmailukerhon luentosarja jatkuu: C210 siirtolento USA->Suomi SIL-luokassa.
Luennoitsijat: Ilari Härkönen ja Matti Suuronen, jotka itse lensivät ko. koneen Grönlannin yli Eurooppaan.
Paikka SIL-luokka, Malmin lentoasema. Klo 17.00-
Tilaisuuteen on vapaa pääsy. Tervetuloa.
Off-topic: This is just for those who read this blog but are not reading my other blogs and are located in Helsinki area Finland. We have a flying club evening event Today at Malmi airport in the SIL class, which is located in the Suomen ilmailuliitto’s building next to the SIL-shop. There will be two presentations – one about flying ultralight aircraft (for PPL-pilots) and another about water flying. The lectures are in Finnish so it may not be too useful for non-Finnish speaking people to come, but if there are Finnish readers who want to join, feel free. The event is free and available to everyone. There are people present from both MIK (Malmin Ilmailukerho) and MILK (Mäntsälän ilmailukerho), so if you want to meet representatives of either clubs, you are very welcome. Lecturers today are Ari Nikkinen / MILK (Mäntsälän ilmailukerho) and Tom Arppe / EUT (Experimental and Ultralight association).
Aihet:
1. Ultralentäminen moottorilentäjille (Ari Nikkinen / MILK)
2. Vesilentäminen (Tom Arppe)
Luentoiltaan on vapaa pääsy. Tervetuloa!
I created new spreadsheet for calculating climb rate at sea level. I created it to investigate single engine situation in a quick way.
You can download it from here:
climbcalc.ods
WARNING! You have to know what input values you enter, otherwise the results will be bogus. For example the value of K depends on aspect ratio and e.
You can download it from here (it is in the katix.org gforge svn):
RangeCalculator.ods
Some calculated results:
Target range = 1500 nm
Fuel consumption = 31.5 liters/h (2 x Rotax 912ULS, with economy cruise power)
[kts] [h] [l] [kg]Speed Endurance required Fuel liters Fuel weight100 15 472.47 335.45110 13.64 429.52 304.96120 12.5 393.73 279.55130 11.54 363.44 258.04140 10.71 337.48 239.61150 10 314.98 223.64160 9.38 295.29 209.66170 8.82 277.92 197.33180 8.33 262.48 186.36190 7.89 248.67 176.56200 7.5 236.24 167.73210 7.14 224.99 159.74220 6.82 214.76 152.48230 6.52 205.42 145.85240 6.25 196.86 139.77250 6 188.99 134.18260 5.77 181.72 129.02270 5.56 174.99 124.24280 5.36 168.74 119.81290 5.17 162.92 115.67
KS20:
Cl – Cd(low reynolds numbers also included, plus also flapped version (+10deg and +20 deg)
L/D vs. alpha:
Cm vs. Alpha:
Cl – alpha:
Printable profile picture of KS20 (black on white background):
QFLR5_v.0001 Calculated polar for: KS20 1 1 Reynolds number fixed Mach number fixed xtrf = 1.000 (top) 1.000 (bottom) Mach = 0.270 Re = 5.000 e 6 Ncrit = 9.000 alpha CL CD CDp CM Top Xtr Bot Xtr Cpmin Chinge XCp ------- -------- --------- --------- -------- ------- ------- -------- --------- --------- -2.500 0.0172 0.00639 0.00156 -0.0630 0.5734 0.1263 -0.9628 0.0000 3.9974 -2.000 0.0779 0.00594 0.00135 -0.0638 0.5687 0.2065 -0.7727 0.0000 1.0832 -1.500 0.1376 0.00529 0.00111 -0.0647 0.5613 0.3515 -0.6885 0.0000 0.7246 -1.000 0.1985 0.00466 0.00091 -0.0657 0.5560 0.4943 -0.7241 0.0000 0.5818 -0.500 0.2604 0.00434 0.00082 -0.0667 0.5474 0.5909 -0.7638 0.0000 0.5048 0.000 0.3235 0.00430 0.00084 -0.0677 0.5380 0.6224 -0.8063 0.0000 0.4565 0.500 0.3863 0.00438 0.00088 -0.0686 0.5260 0.6346 -0.8489 0.0000 0.4238 1.000 0.4491 0.00445 0.00094 -0.0696 0.5127 0.6478 -0.8954 0.0000 0.4002 1.500 0.5115 0.00461 0.00102 -0.0704 0.4945 0.6510 -0.9563 0.0000 0.3823 2.000 0.5732 0.00475 0.00111 -0.0712 0.4723 0.6587 -1.0304 0.0000 0.3682 2.500 0.6344 0.00497 0.00124 -0.0719 0.4472 0.6628 -1.1188 0.0000 0.3567 3.000 0.6941 0.00529 0.00142 -0.0723 0.4114 0.6656 -1.2143 0.0000 0.3470 3.500 0.7516 0.00577 0.00168 -0.0724 0.3616 0.6675 -1.3096 0.0000 0.3385 4.000 0.8098 0.00619 0.00194 -0.0726 0.3230 0.6691 -1.4113 0.0000 0.3313 4.500 0.8664 0.00670 0.00226 -0.0725 0.2804 0.6702 -1.5275 0.0000 0.3247 5.000 0.9229 0.00719 0.00260 -0.0724 0.2437 0.6718 -1.6463 0.0000 0.3189
KS20.dat Airfoil file for QFLR5, XFLR5 or Xfoil
AH-94-145:
AH-95-160:
AH-94-145-vs-95-160:
AH 94-145 simulated ailerons, 70% chord: neutral, -10, +10 deg, mach 0.27 Re 4.5M cruise:
www.aoe.vt.edu/research/groups/bwb/papers/TheBWBAircraft.pdf
http://silentaircraft.org/object/download/1931/doc/AIAA-2006-241-725.pdf”>silentaircraft.org/object/download/1931/doc/AIAA-2006-241-725.pdf
http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050182126_2005180630.pdf”>ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20050182126_2005180630.pdf
http://www.onera.fr/daap/ailes-volantes/aerodynamic-optimization-of-subsonic-flying-wing-configurations.pdf”>www.onera.fr/daap/ailes-volantes/aerodynamic-optimization-of-subsonic-flying-wing-configurations.pdf
silentaircraft.org/object/download/1945/doc/AIAA-2007-453-759.pdf”>silentaircraft.org/object/download/1945/doc/AIAA-2007-453-759.pdf
I have found the XFLR5 X-foil front-end pretty nice as the original X-foil is a bit hard to use. I have been able to run the XFLR5 on Ubuntu with wine, however, it is not without bugs when run under wine. So there is an another alternative – use a native Linux version that does not officially exist yet.
The author of the program has been working on a Qt-version (it is there in the svn). I tried to compile it to Ubuntu. However, because it was using the windows.h min and max, it didn’t compile out of the box today.
I created the following patch (the blogger makes the patch look incorrect, please look at the actual patch file, from here if you want to use it: karoliina-minmaxlinuxpatch.diff ):
karoliina@aurora:~/MyProjects/xflr5/branches/QFLR5$ more karoliina-minmaxlinuxpatch.diffIndex: Objects/Foil.cpp===================================================================--- Objects/Foil.cpp (revision 62)+++ Objects/Foil.cpp (working copy)@@ -32,6 +32,7 @@#include #include #include +#include
//////////////////////////////////////////////////////////////////////// Construction/Destruction@@ -625,7 +626,7 @@{//Returns the foil's length
- return max(m_rpExtrados[m_iExt].x, m_rpExtrados[m_iInt].x);+ return std::max(m_rpExtrados[m_iExt].x, m_rpExtrados[m_iInt].x);}
double CFoil::GetLowerY(double x)@@ -881,8 +882,8 @@
for (i=0; i> m_NXPanels[i];- m_NXPanels[i] = max(1,m_NXPanels[i] );- m_NXPanels[i] = min(MAXCHORDPANELS, m_NXPanels[i]);+ m_NXPanels[i] = std::max(1,m_NXPanels[i] );+ m_NXPanels[i] = std::min(MAXCHORDPANELS, m_NXPanels[i]);}
for (i=0; i> m_NYPanels[i];- m_NYPanels[i] = max(1,m_NYPanels[i] );- m_NYPanels[i] = min(50, m_NYPanels[i]);+ m_NYPanels[i] = std::max(1,m_NYPanels[i] );+ m_NYPanels[i] = std::min(50, m_NYPanels[i]);}int total = 0;for (i=0; i
This patch replaces the min and max to std::min and std::max, ensuring the min and max from are being used. This enables the successful compilation on Ubuntu side.
I have a temporary binary (no debian package yet, I need to agree with the developer when it would be ready for packaging), available for Ubuntu Intrepid:
http://www.katix.org/karoliina/packages/QFLR5-ubuntu-intrepid-bin
Our gforge site can host in addition to software projects, also now open source aircraft projects. If you are interested in open source aircraft idea, feel free to join the forces at:
I have setted up two my open source airplane projects there (they don’t have much yet, but one has to start from somewhere, right?). So if you are interested in joining one of these existing projects, or you have a promising own project which you would like to share with other people, here is your chance. Register yourself and propose a project. I am the admin and approving you and your project proposals.
The motivation to join could be to get some fame. In the software field, open source developers are at the top of the ranking scale. This could be the case in the other fields too. You can make sure that you don’t miss the train by joining and contributing to projects or by creating and sharing your own projects with everybody. Also here is your chance to collaborate and get results. Getting things done with large number of eyes looking after the same thing is more likely than everybody doing their things alone.
The site requires approval from site admins, so please make sure you describe your project in enough detail to get it approved. We do approve potential projects.
Kate setted up gforge on our server, so I decided to put my conceptual design tool to a subversion repository. You can find it here:
http://gforge.katix.org/gf/project/zdesigner/
Contributions to the software is very welcome. You can register to the Katix gforge and join the project if you think you can contribute. I am looking for aeronautical engineers and students to help with the software development. There may be some equations which have errors. You can help with pointing them out. The bug tracker should be used for that purpose.
Also some extra eyes reviewing the code (it is currently quite quickly hacked together) would be helpful, if you are not specialized in aircraft conceptual design, but you are good with C++ and Qt and you have too much time, feel free to join and start filing bugs about bad code. If you have even more time, feel free to write and suggest patches that fixes the issues. I am not looking for comments about indentation (if I see that kind of bugs too often, I will resolve them as invalid) etc., but rather memory leaks, something done really wrong with Qt – real issues in other words.
The code is licensed under GPL version 3 or any later version -license.
Anonymous svn access to the repository (without commit privileges):
svn checkout http://katix.org/svn/zdesigner/trunk zdesigner
My earlier post about the NLF215F simulations with XFLR5, the related parameters for aircraft would be in the use case (one iteration of thinking):
- low altitude cruise:
* altitude = 12000 ft
* W/S = 22 lbs/sqft
* Clcruise = 0.41
* NLF215F flap in the -10 degrees position, gap seals closed
- high altitude cruise:
* altitude = 36000 ft
* W/S = 22 lbs/sqft
* Clcruise = 0.96
* NLF215F flap in the 0 degree position, gap seals closed
- extreme high altitude cruise
* some fuel burned already -> W/S reduced to 21 lbs/sqft
* altitude = 46000 ft
* W/S = 21 lbs/sqft
* Clcruise = 1.48
* NLF215F flap in the 0 degrees position, gap seals closed
- approach
* 1 slot open
* W/S = 15 lbs/sqft
* altitude = 1000 ft
* Cl = 1.1, V = 75 kts (at gross weight, W/S 22 lbs/sqft)
* Cl = 1.1, V = 65 kts (when fuel tanks nearly empty, W/S 15 lbs/sqft)
* NLF215F flap in the +10 degrees position, 1 slot open
- landing
* 2 slots open
I ran some simulations for different airfoils in the same condition:
- cruise at medium low altitude, Cl = 0.4, speed = 0.26 mach, Re = 4000000, wing loading >= 20 lbs/sqft.
I first simulated a large number of different airfoils, but finally only picked the couple of NACAs and the NLF215F with -10 degree negative cruise flap and without.
The NLF215F has a clearly better overall performance all over the Cl range what it comes to Cd. Also the pitching moment of this airfoil becomes low when the cruise flap is at -10 degrees.
The XLFR5 is a easier to use interface built on top of the X-foil engine. The X-foil also features wing and whole airplane analysis functions.
The downside of the program has been that is only available for Windows. However, it can be run nowadays in Linux without porting the program to e.g. Qt (which is a big task), so in the mean time before any cross-platform version appears, you can live with the wine in Linux environment:
- Make sure your wine version is a pretty recent one, version greater than 1.0.
I am using the Ubuntu Intrepid version. apt-cache policy wine reports the following:
wine:
Installed: 1.0.1-0ubuntu2
Candidate: 1.0.1-0ubuntu2
Version table:
*** 1.0.1-0ubuntu2 0
500 http://archive.ubuntu.com intrepid/universe Packages
100 /var/lib/dpkg/status
W: Duplicate sources.list entry http://archive.ubuntu.com intrepid/universe Packages (/var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_intrepid_universe_binary-i386_Packages)
W: Duplicate sources.list entry http://archive.ubuntu.com intrepid/multiverse Packages (/var/lib/apt/lists/archive.ubuntu.com_ubuntu_dists_intrepid_multiverse_binary-i386_Packages)
If you are running the latest stable Ubuntu (Intrepid – 8.10), you can use the Ubuntu supplied one and it will work fine with XFLR5. However, if you are running Ubuntu Hardy or some other distro that does not have the post-1.0 version available, you can install it from winehq repository. For debian based distros like Ubuntu, the instructions can be found from here:
http://www.winehq.org/download/deb
Our living room computer is not yet updated and it is still running the older Hardy. I updated the wine by adding the following line to /etc/apt/sources.list:
deb http://wine.budgetdedicated.com/apt hardy main #WineHQ – Ubuntu 8.04 “Hardy Heron”
Then I did apt-get update and apt-get install wine
The new version of wine got installed and the XFLR5 started working fine.
Download the XFLR5 from here:
http://xflr5.sourceforge.net/xflr5.htm
Go to download page and click download. At the time of writing this, the 4.15 was the latest version.
Download the zip file XFLR5_v415.zip to a new subfolder into your home directory, because the zip file does not contain directories and when you unzip it, if you was in your home directory, you get the package contents directly there which messes up your home with lots of unnecessary files.
Run the XFLR5_Setup.exe by typing on a terminal:
wine ./XFLR5_Setup.exe
The setup runs and finishes.
After this you can notice that a new entry appeared to your Applications menu (in Gnome):
Applications – Wine
Select submenu Programs, and there XFLR5 and on that submenu XFLR5.
XFLR5 should now start successfully.
It works on my computer without problems now.
I created these:
KaroliinaNLF1016.dat
KaroliinaNLF1016F-5.dat
X-foil is predicting for KaroliinaNLF1016F-5 (-5 degrees cruise flap for low altitude) exactly what I was looking for. The KaroliinaNLF1016 is decambered and a bit thickened (16%) version of NASA NLF1015. According to quick analysis, laminar bucket has same shape as NLF1015 has, L/D and minimum Cd is the same, but it has been lowered to a bit lower Cl and also the useful Cl is a bit lower than on NLF1015. However, this way, the unacceptable cruise performance at low altitude theoretically gets acceptable. I need to experiment more and try out with different Re numbers. I was testing at only Re = 1000000 since that is where I was targeting the high altitude cruise. However, the Re is a lot higher at low altitude, gets easily to 5000000, so I will need to try more analysis on the airfoil tomorrow.
Wanna see the current cloud situation?
I accidentally found this, it is pretty cool site, satellite imagery is updated daily and it covers the whole Earth:
The idea of the system comprises of a turbo generator per engine and an additional electric motor behind the tail.
Configuration:
Two gasoline engines, one per wing.
One Brushless DC electric motor, behind the tail, engine size around 15 kW. Does not require any drive shaft because the motor itself is so small and lightweight, that it can be attacted directly to the tail.
Battery that can deliver full power to the electric motor for 3 minutes.
Motor controller for each electric motor.
Possible additions:
Two wing tip turbines, one per each wing tip. Electric motor size ~5 kW.
These can produce power on cruise for the middle pusher motor.
The center pusher motor could drive a unducted fan which would have diameter around 1/3 of the diameter of the fuselage body. See NASA tech paper wake propeller, why. The fan would require adjustable pitch for each blade, so it could be changed from climb condition to cruise condition for the cruise phase (otherwise it would cause drag penalty).
Additional idea:
- the wing tip turbines could be used in case of engine failure for thrust vectoring – one small wing tip engine producing thrust could make the asymmetric thrust condition symmetric without causing drag penalty with deflected rudder.
It seems that X-plane educates aerodynamics, what to expect and think about different things. I was originally saying that I am not so interested in transonic region but rather interested in high altitude. I have been reading about these, but some little things like tinkering with X-plane can cause heureka moments.
And here is what happened:
I have a model of my twin concept in X-plane simulator (obviously, why wouldn’t I). So I set in the latest incarnation the engine critical altitude to 50000 ft (which is feasible with two turbos in cascade plus the mentioned electric turbo compounding). I used 110 hp per side (equivalent of Rotax 912ULS equipped with two turbos doing turbo normalization plus intercooler and after cooler).
I was reading Roskam couple of days ago and noticed that the transonic drag is not a problem if the speed is mach 0.2 or below or not that much above that, e.g. 0.3-0.4 is still quite fine. So I was thinking that maybe it doesn’t get that high that it would become a consideration.
So so obviously, I put the plane model to climb to 55000 ft with autopilot. I had previously added the mach meter to the hud. I came back checking how it flies after couple of tens of minutes. And oops: mach 0.56 when level at 55000 ft. The IAS was barely 100 kts. TAS was a quite a bit higher.
Then, I was thinking what happens to the Reynolds number. Indeed it gets smaller with altitude increasing. But interesting thing is what really happens, to which number it gets. I verified with atmosphere calculator, that indeed, the interesting Re range for this kind of concept with the AR=14 wing, it becomes 600000 – 1600000. That is _very_ low for an aircraft, which is full size and not a RC-model. So the low Re becomes after all a major consideration.
How a plane with AR=14 flies at 55000 ft? It requires _full_ trim aft (meaning nose high) to get the plane keep level – in this model. It became quite apparent that indeed, the tail volume coefficient is a more major concern at high altitude than at low altitude. And the control authority that felt fine at low altitude was not so fine at high altitude.
So this is what we have:
- High performance low Re airfoil is very necessary
- Cd at high lift coefficient is an important design point, the airfoil needs to be designed so that it gives high L/D at high lift coefficient rather than at low lift coefficient like for example NLF414F is targeting.
- A big tail with long enough moment arm
- Propeller with large diameter and possibly more blades than usual, e.g. 5 blades
- And of course, two turbos, intercooler, aftercooler, generator, battery, electric motor and a shaft between the prop and the engine.
Btw, my model is not yet available for download because it is not perfect, and it has couple of problems. It is very hard to get the splines right with straight sections edited by hand, and e.g. engine nacelles look really terrible at the moment. Anyway, it is a fun way for trying out things in practice.
Kate invented one day that why the turbo compounding could not be implemented with electric motors, because that way the usually unfeasible gearbox from normal turbo compounding becomes unnecessary and the gearing is instead implemented with the electric motor and the generator where the generator rotates at higher revolutions than the motor that is used to decrease the load the combustion engine sees.
We were in assumption that this was a new invention, but it seems that it has been used in heavy machinery already, e.g. by Catepillar. This in turn also means that it is feasible.
The challenge would be how to place the generator to the shaft of the turbo. Usually turbos do not have a place where to fit the generator but they are closed packages which are not easily modifiable.
The idea would be to increase fuel efficiency with the compounding and increase the shaft horse power without loading the combustion engine anything more. The electric motor could have an additional lithium polymer batter pack which could increase the power even more on takeoff, so the plane would have on critical take off situation somewhat more power than the combustion engine can output, so in other words, for example getting 80 hp out of a 60 hp HKS700E.
This would result that using impossibly small engine power would become a possibility in a wider variety of airframes. On a twin 2 x 80 hp is a lot more than 2 x 60 hp, single engine performance on 60 hp is very poor in any case without any tricks done to increase the power temporarily.
A quite small lithium polymer battery pack would be enough since assuming 300 fpm climb rate on a single engine, this results 3 minutes to 1000 feet AGL where it should be safe to turn back to the runway and perform landing even with a very low power output of a single engine. So it would be well enough for the extra power from the battery pack last only for 3 minutes. This kind of battery pack would not be that heavy, and the brushless DC electric motor is also pretty lightweight.
Any comments on this?
The ratios for L285, H285, H287 are:
100:50 by volume
100:40 by weight
I am doing some little layup today, so I decided to write the mixing ratio to my blog. I always tend to forget it and have to search from the MGS documentation. Now it is here in my blog. This same ratio applies to my MGS L285/H287.
Why am I interested in pushing the limits instead of doing a known safe solution (meaning thinking more than usual aerodynamics, low weight, low power, low production cost, manufacturing technology, integrated advanced avionics)?
This could be asked with a counter question: why not? What would be the motivation of replicating some existing aircraft with existing technology with learning nothing new?
Someone might say that because of business, to sell these things. But to be sincere, I believe that this business scene is already congested, and it there is anecdotal evidence that the profitability of this business is questionable at times. And there are already number of manufacturers which are doing this and their planes are just fine. If one wants an average plane which is not supposed to push any limits, there is plenty of selection with all kinds of colors, at least one can choose if the plane is white or white or maybe metallic gray, and gluing red or blue tape stripes is optional.
If we look back 50 years and think what has been happening in general aviation. We can conclude that we are entering yet another year with virtually a very little or no progress. Engine technology is still the same, aerodynamics have only moderately improved (laminar flow wings are nowadays somewhat utilized (Cirrus and Cessna 400), but not laminar flow fuselages) but not much, and avionics are still the same (but only gradually improved) rather than inventing a question for the answer that this is always been done that way and answering to it before it is asked.
One could ask, what is there to improve? Why to change anything. If one has nothing better to offer, then the whole venture is worthless. The easiest way to copy and not learn anything new is not to design own aircraft, but buy an existing one. If time spent for engineering is counted with any kind of monetary value, then purchasing an existing aircraft is potentially also the cheapest way to get flying. It is also the safest way, and the chances of big disappointment is small. You get what you pay and it is potentially a good compromise and biggest bugs are already fixed.
But one thing is that for some, pushing the limits is the meaning of life.
I see that the future of general aviation is not very bright without radical new designs which are better performing than the current aircraft, a lot more economical than current models, and essentially less expensive to buy and operate than the current aircraft.
This requires couple of breakthroughs to happen. I am not interested in solving all of them, I do not have unlimited time and can not have solution for everything.
I rather prefer to think everything through a filter which is the compromise I have found best suitable during the couple of years I have been thinking what do I want and now I am finding reasons why I want it. As the answer to the question can not be seen as a singularity, to make the others with a different experience base and collection of individual goals to understand the questions and the answers in this specific case in a give time fragment, can be seen as a challenging endeavor which leads to a setup where all the sides of the multidimensional coin are not fully seen.
When I know what do I want, I can more easily tackle down, what is the minimum resemblance to what I want which still is an acceptable compromise but is feasible technologically and economically and evidently this is a moving target which evolves in the flow of time.
The limits being pushed also evolve but the end result is a snapshot of the broken limits of that time and the frozen design parameters of the evolving concept and today’s limits no longer exist as limits but are by then generally accepted known solutions. If this did not take place, the eventual outdatedness of the design would outweight the thought benefits of the whole reason of doing it in the first place and the understanding of the question of why to do it would be remaining essentially unanswered in a light of the evolving circumstances where the answers are integrating variables rather than constants.
The only sensible way to follow the flow of things is to ensure being a step further than the current state of the art, otherwise the train left the station before it was built and one arrived there to travel to a place which no longer exists. This way the coin has a chance to drop the right side up in a place where the relative up is defined by the eye of the beholder, which by definition, defines the answer to the questions who I am and what do I want.
In the mean time, on the back of my head, I have also been thinking the twin concept. What is the minimum power feasible for the twin for being safe in single engine situation, and what can be the maximum weight and maximum wing loading of a plane which is equipped with two HKS700E engines (only 60 hp each).
Known thing is that Diamond DA42 climbs still at 22 lbs/sqft wing loading and 24 lbs/hp power loading on single engine. However, there is quite a bit more excess power on 135 hp Thielert than on a 60 hp engine. I am feeling that I am getting too optimistic results from the sizing equations with either Raymer or Anderson method.
I have estimated that the plane should not weight more than 700 kg (according to the equations) to still be able to take off and climb with single engine. This may be too optimistic figure, I have been thinking that the limit might be rather near 650 kg or maybe even a bit less.
Thinking pessimistic: the plane can have positive climb rate with 60 hp single engine mode if the gross weight is 600 kg. That gives:
600 – 55 kg – 10 kg – 55 kg – 10 kg = 470 kg for the airframe + useful load excluding engines.
For useful load, minimally needed is:
- Two big adults, 95 kg including heavy clothes per each
- 5 kg baggage per each
- 120 liters of gasoline = 85 kg
This becomes:
95 kg * 2 + 10 kg + 85 kg = 285 kg.
For the plane to be minimally useful, it must be able to carry 285 kg in addition to its own weight. There are two engines and to have useful endurance the amount of fuel has to be double the size of a single engine plane.
The airframe + systems maximum weight excluding engines then becomes:
470 kg -285 kg = 185 kg
This means that the airframe + systems excluding engine can only weight 185 kg. This is a very hard goal to achieve.
The aircraft empty weight then becomes:
185 kg + 65 kg + 65 kg = 315 kg
The empty weight to gross weight ratio becomes:
315 kg / 600 kg = 0.52
This ratio is very challenging to achieve for a twin where the airframe must be carrying in addition to the occupants instead of one engine, two engines, and their fuel.
If we could still take off at 650 kg, then this becomes:
Airframe weight can be increased with 50 kg: 185 kg + 50 kg = 235 kg
235 kg + 65 kg + 65 kg = 365 kg
Looks like now we are talkin. This looks like a figure which might be theoretically possible, even though this is still very hard goal. As seen on ultralight planes, achieving empty weight under 300 kg is very hard. Adding extra engine on top that requires aircraft that is as lightweight than best ultralights equipped, plus can still take the additional engine.
But this is just theoretical thinking and whether or not it may be feasible, the discussion can continue:
The empty weight to gross weight ratio then becomes:
365 kg / 650 kg = 0.56
Historical data shows that at least on a bit larger aircraft, the 0.56 value is pretty well achievable.
Lets consider now the performance for the 650 kg case:
Single engine produces only 60 hp power. Only the excess power can be used for climb. This means that in a side slip of asymmetric thrust and climb angle of attack, the total drag (drag due to lift + fuselage drag) must be less than the thrust of 60 hp at best climb speed with a propeller that has efficiency of 0.7 (for pessimistic evaluation, I prefer to not use 0.85) by a large margin, and then the climb rate pretty much becomes from the weight to be lifted and how much excess power is still left.
The power loading for single case would be: 23.8 lbs/hp. This would be about the same as Diamond DA42. The drag must be low in order to ensure that the power needed for level flight is small, and there is excess power for climb, even with very low power.
Then comes the disaster of increasing wing area, this increases drag, but on the other hand, increases also lift. However, to get good cruise performance on the low power, wing size should be as small as possible. So some compromise is needed here. Increase in wing loading has to be accounted with increase in aspect ratio to keep the induced drag the same. Increase of aspect ratio may increase weight, but does not necessarily always do so. For example the earlier mentioned LH10 has very light wings, despite of aspect ratio of 14. So it worths researching on this area. A good design is a synergetic design which combines couple of good things into one good compromise.
I maybe need to redo the calculation yet another time again.
Why I am thinking this?
- For a plane that I would design for myself, I could choose Rotax 912ULS, and get two used engines with about half the price of a new Rotax 912ULS. This would be roughly the cost of a pair of new HKS700E.
- However, if we think a kit-builder who wants to have a twin with shoestring budget. Many aviators are limited with budget (aviators are always rich simply does not seem to be true, and if they originally were, they no longer are after starting spending to flying). So we have been thinking of a concept of a light plane with two engines with good performance. Any twin out there, even used ones, cost many many times more than it would cost to build a plastic one with two little HKS700E engines.
- I think that twin engine aircraft are not so popular, not because they require the additional license, but because people do not opt for the additional license, because the cost of the twin is prohibitive. There is absolutely no twin out there where one could log twin engine time and which would not cost a fortune of a millionaire to own or cost a fortune of of a normal people to maintain and operate.
- It is often explained that twins are more dangerous than singles. However, the context seems to be forgotten. Single engine limits the use of the plane and with two engines, people may often go to more dangerous situations.
- And it is not only a bad thing, consider this: You live in Finland and want to visit for example Greenland. What do you do if you want to fly there by yourself and not to sit as a passenger on an Airbus? You go and start your C172 and head towards Greenland. If the one old-fashioned engine that is almost approaching car engines in reliability, that is there, quits, then you are in biiig trouble. Wouldn’t it be great if there was a second engine and you could still fly even if the one failed. Even if the climb rate with single engine is poor, you could still maybe get out of there alive. Your speed would get slow, but also your fuel consumption becomes half because only one engine is drinking the fuel. You actually might make it and your relatives don’t need to arrange funerals.
Any comments on this?
I was thinking which could be a suitable configuration if target would be to the microlight category (Finnish ultralight will be aligned with European microlight), or to EASA LSA category. The US-LSA category is stupid since it has some severe limitations which removes the reason to try to optimize anything – the speed limitation and also the stall speed limitation as clean -> with these limitations, it does not worth optimizing the aerodynamic performance or flap configuration, for US-LSA, the best solution probably would to design a plane, which is as lightweight as possible and which would not have any kind of flaps and which would achieve the stall speed only with the wing area (because that is what the limitation implies anyhow), so the utilized Clmax becomes close to 1.0, which is poor.
The main criteria in this more sane European category is the weight and the second main criteria is the stall speed. These are the most important features, other features are secondary. The performance can not be optimal, but it can be optimized to the constraints given by the weight and stall speed limitations. It would be also necessary to cut the part count to minimum, an inexpensive plane will be for sure more popular than the more expensive one, in the category where the buyers are not the richest people out there (who would anyhow order a Cirrus-Jet), but normal hobbyists who are not swimming in money.
So consider this:
- Plane structure would be based on carbon fiber rods (pultrusion rods).
- The fuselage would not be a structural member of the plane, but rather a baggage pod located below the spars. The twin booms would be a pultrusion rod each. The engine would be mounted to the wing spar rather than to the fuselage. These rods could have aerodynamic fairings on top of them (which also allow space for control cables etc.).
- high aspect ratio wing, which enables good climb rate with low power
- HKS700E engine in pusher configuration
- Fixed pitch pusher propeller behind the pod (but thrust line to the wing spar).
- inverted V-tail in the ends of the two booms, and the tail would connect the
two booms with the help of a pultrusion rod which functions as spar.
- Main landing gear connected to wing spar
- Nose gear located under the pod.
- Wing structure would be solid blue styrofoam, and in wing root there would be a large fairing which contains fuel (on both sides). The wing skin could be either carbon fiber or fiberglass (fiberglass to reduce cost obviously)
Think how many parts this requires compared to how many parts and layup schedules is usually needed. The pod type cockpit could be almost a complete monococue. There would be need for only instrument panel and some structure where one can assemble the pedals. Also the instrument panel, as we know it, does not need to be like it is, a panel. There are other ways arranging instruments in the plane than having a straight panel where everything is put with tiny screws. None of the modern cars use that old-fashioned way anymore. With modern avionics, you don’t need a big panel with lots of switches, knobs, circular gauges etc. You can have just two screens which display and control everything.
The only strength needed in the fuselage is for crashworthiness, it does not need to carry any loads, and it does not need to be shaped unoptimally to avoid flutter tendency for example, all structural members are straight lines and separate from the fuselage.
The idea comes from some NASA PAV concepts, but as modified. It also has some influences from the Sunseeker.
The concept could have idea of being as lightweight as possible (the lower power engine also supports this mission) and still being as highly performing as possible (that can be achieved with the light weight and aerodynamics, not so much trust is needed).
So the performance target setting for conceptual design could be:
- beat 100 hp Dynaero MCR-ULC in empty weight with large margin
- be on par with 100 hp Dynaero MCR-ULC in speed (with only 60% of the power available)
- and the rest comes from the category limitations
- be a lot cheaper than most other same category plane on the market
- climb rate 800 fpm (remember that because of the low climb speed, the climb gradient is high despite of the not so high number compared to high performance aircraft)
Compromise:
- beat 100 hp Dynaero MCR-ULC in empty weight
- cruise speed compromised to between 80 hp WT9 Dynamic and 80 hp MCR.
- climb rate 600 fpm
Failure:
- heavier than MCR-ULC
- slower than 100 kts in cruise
- climb rate less than 500 fpm
Anyone interested in a such thing or having ideas (for or against) for a such thing?
Here is an illustration about the idea (15 minutes of Rhino magic):
I became interested about aerodynamics through a experimental project I started building with Kate. It was Cozy MKIV. We have not been building that plane for quite a long time, but we got couple of parts done, for example the canard foams were cut with help from Rauno Viljanen and I managed to do quite poor quality chapter 4 bulkheads with zero understanding what I was doing structurally or otherwise.
Back then there was a concept of “speed modifications” very popular on canard forums, and I think it still is happening there, I haven’t followed for a while. They are being invented most frequently by people that don’t have even pilot’s license yet or don’t have flown any aircraft to the date, and they don’t necessarily have much understanding on the aerodynamics either.
Back then I was really interested in them, and it felt like magic, you bolt on this and that improvement, and it becomes this and that much faster and more efficient. There were all kinds of concepts like cutting lower winglets, shortening wings, or even placing vortex generators to a laminar flow airfoil. I did not see back then what was wrong and why they wouldn’t work as expected. Now I know. They were very entertaining reading, and actually inspired me to start thinking these things in more detail. And I am still on that road. They are not essentially bad but they may not work as the builders expect them to work because they don’t understand why they are doing them, but are relying on non-scientific reasons to bolt them in.
Couple of years have passed and I have been reading about aerodynamics and trying to find out how it all works. It occurred to me at one point, that it is not a bolt-on feature you can add to existing design, but aerodynamics is all about the flow. And understanding it as a whole.
Someone might say that “by adding vortex generators, you get 5% fuel savings”, that can be true only in a case where the flow otherwise preliminary separates. Good aerodynamics, is not fixing this and that with little this and that, but trying to get it all right and if still a problems persist, try to fix them then with some additional fix.
What happens if you consider adding vortex generators to Cozy MKIV front wing, in other words, the canard? The canard has Roncz RMS1145 airfoil which is about 45% laminar. Depending on where you put the vortex generators, you can vary between 0% laminar and 45% laminar. You can’t get more than 45% laminar with that shape.
However, what else can happen is that, the turbulent flow attaches to a higher angle of attack on the airfoil which was designed to maintain its lift even if the laminar flow is disturbed by bugs or rain? You may get some more Cl out of the airfoil with the added vortex generators, and may be able to delay the stall angle of attack some.
But think the whole picture: the main wing-canard relationship was tuned so that the canard always stalls before the main wing. If this does not happen, the plane can enter into deep stall which is not recoverable on the particular type in question. If you delay the stall of the canard to a higher angle of attack, you are trying your luck with the main wing’s Clmax and maximum angle of attack before it stalls. And it might be that you can achieve higher angle of attack with the canard than the main wing can function without stalling, and the result is pretty severe, everyone on board most likely die as a result, unless you are super-lucky like some that have survived from a deep stall crash. But wait, there was someone who also dropped from a passenger jet without parachute and survived. I would not try my luck based on the few exceptions.
Same thing what happens if you shorten a wing. Jet fighters have shorter wings and they are faasstt. Right? In case of subsonic aircraft you actually increase induced drag if you shorten the wing. You also increase wing loading, which also increases induced drag, although it reduces the wing wetted area which is desirable for lower drag. But in this case, the increase in induced drag can be such high that the plane actually becomes slower. There was one manufacturer that was doing light aircraft, and they were thinking how to convert their aircraft to LSA. The LSA version had longer wings, and instead of limiting the maximum IAS to 120 kts, the supposed to be LSA version became in fact faster than the plane with the shorter wing.
One could think also that a plane which would have smoothly rounded shape in the wing tip instead of a maybe less elegant looking cut shape would be faster. And surprise might be great when the person would notice that instead of making a faster plane, the plane actually got slower because of the modification. Here is also the thing: what you are trying to achieve – looks or relying someone’s claims, or are you thinking what you are going to achieve in terms of flow and how it affects the wing tip turbulence and is what you are trying to achieve beneficial or not. The sharp cut hoerner shape in the wing tip might be there for a reason, it resists the flow from the bottom side to the upper side because of the sharp corner there. Rounding this shape makes the wing tip potentially worse. Only potentially, because you have to consider what is going on, and what you are going to achieve. There is no “yes this is right” and “no this is wrong”, because everything affects to everything. But you always should know why you are going to do something. Because it is faster that way is a wrong answer. Right answer is the understanding of why. Would be better to first understand why before doing it rather than understanding why you did it and why you shouldn’t have done that.
The point is, that the optimization of aerodynamics requires thinking as a whole. Improving something somewhere may not help if something else is really bad, and it can get worse by uninformed improvement somewhere. Only by knowing what you are doing, as a whole, you can do aerodynamic design which results better performance unless you are very lucky. In some cases, you might be lucky, but you could ruin your results by doing something additional uninformed where the whole picture what is going on is not taken into account.
If you want to do a optimized aerodynamic design, you have to begin with that basis, you can’t bolt it on after. Cleaning up a existing aircraft is possible to some extent, but only to some extent, which is very small. An optimum design is a in balance from the aerodynamic and structural standpoint and everything is taken into account in every detail and they are understood as a whole with the whole thing. It is not a puzzle with small pieces you just put together, but a puzzle where the little pieces change every time you change something little.
If you want to clean up an existing airplane, what you need to do is that you have to understand what you are doing, in other words, what you are trying to achieve what you are changing. You have to consider all sides of the change, what it does. Things are not so simple as they might at first seem. And some things are simpler than believed. Impossible – there is no such word. You just can’t bend what is possible with pure luck, it does not work in the long run. Understanding what you are trying to achieve and what are the potential consequences in good and bad for every detail helps doing less not so good decisions.
AERADE Reports Archive, search keyword slotted
http://aerade.cranfield.ac.uk/ara/dl.php?filename=1947/naca-tn-1395.pdf
http://aerade.cranfield.ac.uk/ara/dl.php?filename=1947/naca-tn-1463.pdf
http://aerade.cranfield.ac.uk/ara/dl.php?filename=1950/naca-tn-2149.pdf
http://aerade.cranfield.ac.uk/ara/dl.php?filename=1949/naca-report-942.pdf
Fundamentals of Aerodynamics, by John Anderson Jr.
Aircraft Performance & Design, by John Anderson Jr.
Aircraft Design: Conceptual Approach, by Daniel Raymer
Jan Roskam: Aircraft Design parts 1-7
Jan Roskam: Airplane Flight Dynamics and Automated Flight Controls
Jan Roskam: Airplane Aerodynamics and Performance
Aerodynamics for Engineering Students
MODERN AIRCRAFT DESIGN, Volume 1 5th Edition, by Martin Hollmann.
MODERN AIRCRAFT DESIGN, Volume 2 4th Edition, by Martin Hollmann.
COMPOSITE AIRCRAFT DESIGN. REVISED 2003. By Dr. Hal Loken and Martin Hollmann.
MODERN AIRCRAFT DRAFTING by Eric and Martin Hollmann.
ADVANCED AIRCRAFT DESIGN by Martin Hollmann.
BRUCE CARMICHAEL’S PERSONAL AIRCRAFT DRAG REDUCTION
Theory of Flight
Aerodynamics for Engineers
Model aircraft aerodynamics
Smith: Illustrated guide to aerodynamics
Ron Wanttaja: Kit airplane construction
Bingelis: Sportplane construction techniques
Performance of Light Aircraft
Synthesis of Subsonic Aircraft Design
Theoretical Aerodynamics
Hoerner: Fluid Dynamic Drag
Flight Performance of Aircraft
Design of the Airplane
Burt Rutan: Moldless composite sandwitch aircraft consrtuction
The length-diameter ratio 3.33 was found ideal for laminar pods which are intended to the fuselage where the length Reynolds number tends to get high. The laminar flow can not sustained for very high length Reynolds number, therefore the need of relatively short pod when compared to a wing airfoil shape. That sounds like a rule of thumb, in other words, a generalization that applies to one example, but is not necessarily applicable to everything.
However, in case of engine pods, it would require some investigation to determine the optimum length/diameter ratio. On the wings, the length Reynolds number for a laminar engine pod would be similar than that of the wing. Logic says that if the wing can sustain 60% laminar flow with its chord length, then the pod with similar length diameter ratio should be able to do that as well.
Therefore, what is the ideal length diameter ratio for a engine pod if the engine pod comprises of NACA 66-series laminar symmetrical airfoil (which provides zero lift at zero degrees angle of attack)? Is it still 3.33 or something else?
I was yesterday evening also reading some documents I have got links from a Internet friend of mine (a aerodynamics-guru) and was comparing that to what was told in Bruce H. Carmichael’s Personal Aircraft Drag Reduction Book. The fuselage-wing intersection optimization is described as a rule of thumb in the book, with the premise that the designer does not have access to CFD software, optimizing the streamlines of the fuselage to be similar than the streamlines of the wing, to avoid adverse pressure gradient.
However, today the CFD software does not need very expensive, in fact, OpenFoam is free software, and the situation might prove nowadays different than it used to be (still haven’t had enough time to learn how to use the OpenFoam, but I will find out sooner or later, because I must). It would be enlightening to try out the wing-body intersection optimization. One thing I also learned is that the fairing between the wing and body has to be turbulent airfoil which has very late separation, because the flow at the wing intersection on the fuselage is turbulent anyway, the laminar flow can not be sustained that far without active boundary layer control. I am not planning active boundary layer control for step 1, to get things done.
Laminar pods need to have low length/diameter ratio to get the benefits of laminar flow. Bruce Carmichael recommends length/diameter ratio of 3.33 in his book. I accidentally found also a pdf format article from web which talks about the same thing. You can get if from here:
www.aerorag.com/resource/aircraft/aerodynamics/carmichael/min_fus_drag_carmichael.pdf
Here is another document about the matter:
ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19860014381_1986014381.pdf
I was one day looking for information about Rutan’s Grizzly, a three surface STOL bush plane which doesn’t look at all like the Piper Cub. Today, I found a related patent, how Burt Rutan managed to implement fowler flaps without external supports which create drag on cruise.
You can read it here: http://www.freepatentsonline.com/4614320.html?query=PN%2F4614320+OR+4614320&stemming=on
Here is an article which includes some text about Burt Rutan’s Raptor UAV.
www.flightglobal.com/pdfarchive/view/1993/1993%20-%202623.html
Just accidentally when searching about Raptor UAV (this is off-topic to this posting, but anyhow contains interesting information including patent numbers), I found this: Burt Rutan’s CV. Needless to say “Burt Rutan is my hero”, but here is the CV of Mr. Rutan:
http://www.roycecarlton.com/speaker/Burt-Rutan-Curriculum-Vitae/
I was thinking about over 25000 feet cruise altitude for non-pressurized version of my concept, but I was yesterday Googling about death zone and effects of high altitude to human physiology, and it became quite apparent that it is not healthy to fly at 25000-30000 feet, it is too high altitude for humans to bear even with supplemental oxygen. Even with pressure masks like those on fighter pilots, it might not be very comfortable and safe. It is therefore not a surprise after all, why some non-pressurized GA planes are limited to 17500 feet (like Cirrus SR20 and SR22).
So the need for pressurization comes a lot earlier than I was thinking, and apparently even cruising over 20000 feet would pretty much require it.
Some articles about supplemental oxygen use:
http://www.dr-amy.com/rich/oxygen/
The highest altitude non-pressurized aircraft have been certified usually are 25000 feet according to quick searches to Internet. Columbia 400 (Cessna 400) is non-pressurized and certified to 25000 feet. Flight at that altitude require oxygen mask and it is just above the “death zone” which was mentioned in one Mt. Everest page I was looking yesterday.
According to one UAV report I have (SR22 was compared to a UAV airframe), Cirrus SR22 technical service ceiling is at about 33000 feet. SR20 on the other hand with a lot less excess power does not most likely reach its limit altitude of 17500 feet most likely unless it is very lightly loaded. On our trip to Mojave it barely made it to 11000 feet at gross weight and non-standard atmospheric temperature conditions (it was hotter than on standard atmosphere).
I have been looking quite a while how to get the aerodynamic design optimal and how to save there some drag, or a lot of drag, but a good design has also other parts taken into consideration. One of them which should not be underestimated is the structural and thus weight.
If we look for example EM-11 Orka, what is the problem with it when it is actually slower than aerodynamically less efficient and lower power Tecnam P2006T. It is pretty obvious what is the problem: it is not the aerodynamics of the plane (which is good) but the weight. The gross weight of Orka is very high, even higher than on DA42 that some people consider to be a lead-angel (lyijyenkeli). This has implications obviously to the empty weight too. That is very high as well. The empty weight-gross weight ratio is not actually bad in Orka, it is actually better than average. However, because of the gross weight being so high, the empty weight has to follow too. With the high weight, aerodynamic efficiency goes out of the door.
So it is very important that aircraft has minimum possible empty weight and as high as possible empty weight to gross weight ratio.
From the lighter end of the scale, Dynaero MCR01 is a good example. It is very lightweight, a lot lighter than its competitors. And it really shows positively in the performance. The wings in the ULC-model don’t even incorporate a NLF-airfoil and the fuselage is all-turbulent behind the propeller. Still it is damn fast compared to all competition in its class with the same engine and propeller. The Dynaero’s empty weight-cross weight ratio is not actually much better than on Orka, but because Orka is so much heavier and it is designed to carry so much more, the end result is very heavy (and it requires higher power engines than the Orka prototype originally had).
So this leads to a conclusion:
Previously mentioned gross weight of 818 kg for the twin concept is not unfounded. It represents ratio of 0.55 which is worse than on Orka or Dynaero MCR01. The goal has to be drawn somewhere. If the empty weight has to be more, e.g. 500 kg, that means 900 kg MTOW with ratio 0.55, and already a bit worse performance (speed (because the plane has to fly at higher Cl to maintain level flight on cruise and it is no good especially if the airfoil was designed to give its lowest drag at low Cl value) and climb performance).
Someone might be wondering why I don’t talk about aerobatics much at all – Aerobatic planes require higher empty weight – gross weight ratios more than 0.55, and because of that I am not even thinking about a aerobatic plane which is intended for cross country flying. Efficient cross country machine has to be separate from aerobatic plane unfortunately because of restrictions what is achievable with even the best materials out there. Strength in airplane is not a place where a compromise can be made, it must be strong enough for the intended use or it is a deathtrap, and this leads to that the empty weight – gross weight ratio may not go much lower than 0.53 very easily on a small aircraft, especially without compromising something else like aerodynamics.
I have been thinking the ways to achieve a design and implementation of a dream aircraft, and have concluded that it has to go in more than one step, so I was thinking the following milestones:
1. Unpressurized version, with a single turbo and fuel injection kit per engine. Possibly with a cabin similar to seen in Orka, avoid the manufacture of the doors. Woodcomp CS propellers. Target cruise altitude = 25000-30000 ft with supplemental oxygen. Corners cut where necessary to just get it done. No active boundary layer control, no wing tip propellers etc., rely on natural laminar flow to achieve efficiency. Unstable release of plans, calculations etc. Version A.
2. Open source plans stable release for the version A (CNC code, 3D models, 2D drawings, construction plans, layup schedules). Flight testing gives the final specifications for version B and ideas what to change to version B. Version A prototype is in use.
3. Optimized version of the above, version B. Modifications to version A prototype, version A becomes version B.
4. Stable release of version B plans (CNC code, 3D models, 2D drawings, construction plans, layup schedules). Version B might be alternative for a basis of a kit.
5. Pressurized version with doors, twin turbos per engine, intercooler and aftercooler per engine, computer controlled waste gates, and hybrid turbo compounding with two electric motors where one is functioning as generator and the the other runs the compounding. Possibly longer wings for high altitude flight. MT propeller or other higher end propellers. Possibly aerodynamic design changes, based on issues found in versions A and B and other improvements. Version C.
6. Open source plans stable release for the version C (CNC code, 3D models, 2D drawings, construction plans, layup schedules). Version C is a completely new aircraft and thus version B and version C coexists.
There are at least two milestones before 1.
-1 = concepting and collecting information, and creating needed softwares (present)
0 = initial concepting freezes, and version control repository (e.g. svn) exists for all data and there is a web page for the project.
I have been flying all kinds of planes and been kind of figuring slowly out what is the optimum for power loading. It turns out like 9 lbs/hp produces the “fun” experience. That is the “RV-grin” I would say.
So what comes together is:
- Optimum aircraft would consist of 2 x 100 hp engine
- Very low drag fuselage
- Very low drag wings
- High aspect ratio
- High wing loading, 22 lbs/sqft.
- Double slotted flaps
- Power loading 9 lbs/hp
-> mtow 1800 lbs = 818 kg
Empty weight should be under 450 kg to have enough useful load (368 kg, includes fuel).
=> wing area = 81 sqft.
For more general purpose use, it could be written:
- for high performance use, mtow limited to 818 kg.
- for long range use, mtow limited to 950 kg.
This becomes:
- the wing loading limit of 24 lbs/sqft can not be exceeded for the 950 kg because otherwise the stall speed gets too high
=> this becomes:
- 2090 lbs / 24 lbs/sqft
The wing area can be then assumed to be 87 sqft. 7 sqft more than on the case of high performance case.
- Wing loading calculation for the high performance case becomes:
87*22 = 1914 lbs MTOW.
1800/87.0 = 20.6 lbs / sqft
This would cause the airframe to gross weight ratio to be 0.47. This is very low and may not be realistic without special structure. A more realistic figure would be 0.55 ratio. This becomes: 450.0/0.55. Guess what, we get the 818 kg = 1800 lbs gross weight from that. So structurally the 450 kg empty weight and 818 kg gross weight should be feasible. Dynaero MCR-01 is 0.53; 260 kg / 490 kg = 0.53). The LH-Aviation LH10 is 260 kg/500 kg = 0.52. Both of these are carbon fiber structures. With lower cost materials, this may not be even nearly feasible.
If we take a pessimistic value for airframe to gross weight ratio – 0.6 and we have set the gross weight to 830 kg (based on optimizing the power loading), this gives 498 kg empty weight. This should be easily feasible if turbos and pressurization is not taken into account.
A flying club friend (Samuli Pänttäjä) kindly offered a familiarization flight on his Dynaero MCR01. I flew with Pertti Husa (a flight instructor and friend).
The short story is that the plane is very interesting, it is very different from any other same category plane.
It is close to the maximum performance one can get out of Rotax 912 in tractor configuration without utilizing laminar flow over the fuselage (I don’t mean only speed, but overall performance) – the climb rate, takeoff distance, climb speed, minimum speed, stall behavior and cruise speed at low altitude (IAS) and landing distance. This plane really rocks, it surely blows average Cessna-pilot away. Despite of the low horse power in the engine, this is maybe even more high performance aircraft than turbo Cirrus SR22 is with over 300 hp. This plane has 100 hp Rotax 912 with MT propeller hydraulic constant speed propeller. With Rotax 914 this…
The takeoff is very similar than on Cirrus SR22. Everything happens maybe even faster than with the Cirrus. The plane accelerates like a rocket, is airborne almost at the same moment, time to switch flap ups, trim the plane, reduce power and propeller speed all come very quickly.
The economy cruise speed (manifold pressure at 26, rpm at 4600) settled to about 250 km/h (135 kts IAS). We didn’t try flying at altitude, I don’t yet know how much TAS the plane collects at high altitude. At low altitude the cruise speed is anyhow about the same as on Cirrus SR20 leaned to best power setting. It really moves compared to Cessnas etc.
It also became apparent that the plane would cruise, with little more power, a lot faster. With a little pitch down causes the IAS to go over 300 km/h and it happens effortlessly and quickly. Watch out when pitching down or you will go over the VNe very quickly!
The plane takes of and lands to a very short distance. The approach speed is very low. The double slotted flaps are very effective and the plane can be flown insanely slowly. We did one approach at 80 km/h. On the other hand, in take off, the after the plane gets airborne and out of ground effect, the speed very quickly rises to 170 km/h (91 kts). Very comparable to Cirrus SR20. The big difference to Cirrus is that, on Dynaero, the climb angle is steep. It is going up like an elevator. Takeoff from very short runway is possible and it finely clears the obstacle with ease.
Feelings on landing pattern are quite similar than on SR22, one has to act quickly and not fall behind the aircraft. Pitch down, even on landing pattern, easily makes to plane go 300 km/h. If you are trying to be behind a Cessna that flies the pattern about 130 km/h, you are going to take over it, and very fast.
The “secret” of the plane is:
- very low empty weight
- very low cross sectional area
- small wetted area
- low cooling drag
- double slotted flaps (high Clmax)
- relatively high wing loading
Everything in the plane is made out of carbon fiber. Even rudder pedals are carbon fiber.
It is beneficial to have as low as possible empty weight, high Clmax, high wing loading and as great as possible power to weight ratio. This plane has those in better balance than other types I have flown to the date.
Some pictures:
Video of landing to EFHF at Youtube:
A flying club friend (Samuli Pänttäjä) kindly offered a familiarization flight on his Dynaero MCR01. I flew with Pertti Husa (a flight instructor and friend).
The short story is that the plane is very interesting, it is very different from any other same category plane.
It is close to the maximum performance one can get out of Rotax 912 in tractor configuration without utilizing laminar flow over the fuselage (I don’t mean only speed, but overall performance) – the climb rate, takeoff distance, climb speed, minimum speed, stall behavior and cruise speed at low altitude (IAS) and landing distance. This plane really rocks, it surely blows average Cessna-pilot away. Despite of the low horse power in the engine, this is maybe even more high performance aircraft than turbo Cirrus SR22 is with over 300 hp. This plane has 100 hp Rotax 912 with MT propeller hydraulic constant speed propeller. With Rotax 914 this…
The takeoff is very similar than on Cirrus SR22. Everything happens maybe even faster than with the Cirrus. The plane accelerates like a rocket, is airborne almost at the same moment, time to switch flap ups, trim the plane, reduce power and propeller speed all come very quickly.
The economy cruise speed (manifold pressure at 26, rpm at 4600) settled to about 250 km/h (135 kts IAS). We didn’t try flying at altitude, I don’t yet know how much TAS the plane collects at high altitude. At low altitude the cruise speed is anyhow about the same as on Cirrus SR20 leaned to best power setting. It really moves compared to Cessnas etc.
It also became apparent that the plane would cruise, with little more power, a lot faster. With a little pitch down causes the IAS to go over 300 km/h and it happens effortlessly and quickly. Watch out when pitching down or you will go over the VNe very quickly!
The plane takes of and lands to a very short distance. The approach speed is very low. The double slotted flaps are very effective and the plane can be flown insanely slowly. We did one approach at 80 km/h. On the other hand, in take off, the after the plane gets airborne and out of ground effect, the speed very quickly rises to 170 km/h (91 kts). Very comparable to Cirrus SR20. The big difference to Cirrus is that, on Dynaero, the climb angle is steep. It is going up like an elevator. Takeoff from very short runway is possible and it finely clears the obstacle with ease.
Feelings on landing pattern are quite similar than on SR22, one has to act quickly and not fall behind the aircraft. Pitch down, even on landing pattern, easily makes to plane go 300 km/h. If you are trying to be behind a Cessna that flies the pattern about 130 km/h, you are going to take over it, and very fast.
The “secret” of the plane is:
- very low empty weight
- very low cross sectional area
- small wetted area
- low cooling drag
- double slotted flaps (high Clmax)
- relatively high wing loading
Everything in the plane is made out of carbon fiber. Even rudder pedals are carbon fiber.
It is beneficial to have as low as possible empty weight, high Clmax, high wing loading and as great as possible power to weight ratio. This plane has those in better balance than other types I have flown to the date.
Some pictures:
I created Qt-based UI for the aircraft design program I am writing. The initial version is available from here:
http://www.katix.org/karoliina/packages/zdesigner-current.tar.gz
ChangeLog
COPYING
zdesigner – Ubuntu Intrepid Binary
You need to have Qt 4.5 installed to run the binary.
I have been thinking what are the advantages and disadvantages of push-pull configuration. Everyone knows that push-pull has both disadvantages of pusher and tractor configuration but also implements a simple to control center line thrust operation for a critical single engine situation. However, there is more than that to it.
If you think one-of-a-kind aircraft, e.g. what Burt Rutan used to do during the early years. You want to build a twin on a shoestring budget. Then you realize that you have to buy two of everything. What if you have two engines already hanging around but they are not exactly the same make, model and horse power.
In case of center line thrust, no problem. Nothing requires the two engines to be the same. Not even weight and balance. Burt Rutan’s Voyager is an example. You can find that the front engine is different from the rear engine.
It might not be because of the reason described above, but if you are into auto conversions and designing a twin, how you plan to get two identical engines for not much cost at all (from totalled cars for example). Might prove to be a challenge, especially in a country like Finland where the population and the availability of engines might be poor. With center line thrust you can use different engines in the front and rear.
By the way: Merry Christmas and Happy New Year!
I found a quite interesting site:
http://www.nextcraft.com/
There was for example a 1/3 scale Berkut/Long-Ez project. 1/3 scale RC-model is said to be minimum sufficient for modeling the full scale aircraft, so I find this example quite educational. As can be seen though, the airfoils are different than on the full size plane. This is necessary because of the very low Re of the model. It does not thus model it very accurately, so there might be still surprises on the full scale version when scaling up, but I think it would still be good to do 1/3 models of new aircraft designs.
The direct link to the 1/3 scale Berkut can be found here: http://www.nextcraft.com/berkut01.html
Here is a interesting specification chart which illustrates the differences between different aircraft types:
http://www.flypas.com/images/DA40_comparison_feb_2008_rev_2_022408.pdf
I knew that information already, but this is a chart you can look at if you don’t happen to know which is the difference between Diamond DA40, Cessna C182, Cirrus SR20 and Piper Archer. Needless to mention (but I mention anyway), the models utilizing composite high aspect ratio wings with super-accurate surface and laminar flow airfoils are the winners on this chart, namely the Diamond DA40 and Cirrus SR20. On this chart, the DA40 wins also SR20. Indeed, the DA40 is pretty good compromise, but the SR20 is not so bad compromise either. It has for example larger cockpit for larger people. However, bigger size does not come without a penalty and it is evident in the specs, SR20 takes more power to go as fast as the DA40 with 20 hp smaller engine (75% power = 135 hp whereas on Cirrus 75% power = 150 hp). The biggest losers on the chart, obviously, are made of metal (with protruding pop-rivets), and have turbulent flow over the low aspect ratio wing.
The same page also has a comparison made between trainer type aircrafts:
http://www.flypas.com/images/comare_da20.pdf
The comparison chart contains Diamond DA20-C1 Eclipse, Cessna C172, Piper Warrior and Cirrus SRV.
This is not completely fair because some of the planes are 4 seaters and some two seaters, but isn’t still too hard to see the difference between the laminar flow planes compared to turbulent flow planes. Both Diamond DA20-C1 Eclipse and Cirrus SRV use laminar flow airfoil, slotted flaps and a high aspect ratio wing. Both are made of composite materials. I have flown myself the Diamond DA20-C1 Eclipse and the SR20 (the IFR version though, but it is no different from the SRV other than in terms of certification and equipment), both are really nice aircraft to fly and they perform pretty well when comparing to the competition. Of these, the DA20 is most pleasant although quite a bit slower in the reality than the Cirrus.
The page also has a performance vs. altitude chart for three aircraft types – 2 Mooney and Cirrus SR22 (normally aspirated version). From this chart, the effect of the turbo is quite evident on the turbo-version of the Mooney. At high altitudes it is the fastest of the compared aircraft. The comparison would get tougher if the SR22 was the turbo-model which cruises well over 200 kts at high altitude.
http://www.flypas.com/images/comparison1.pdf
The comparison chart has some things which I am not in full agreement with. For example the front hinged canopy superiority. It gives good view from the cockpit yes, but it is stating that it makes it easy to get into the cockpit. That is very far from the truth. It is a lot easier to climb to a Cirrus through the door than to a Diamond. Getting into the Diamond is like getting to a sports car. It is not that difficult and I would not consider it personally a problem, but saying that it is superior in easiness compared to the side doors of Cirrus, that is bullsh*t. Cirrus is a lot bigger and easier to get into. Diamond excels elsewhere than on this. And there are other things too on this list, so please have your filter set to on when reading it. In a sense, the comparison chart in the plastic planes is better.
Here is the comparison from plastic airplanes:
http://philip.greenspun.com/flying/plastic-airplanes
And here is a Cirrus SR20 review:
http://philip.greenspun.com/flying/cirrus-sr20
And here is a Diamond DA40 review:
http://philip.greenspun.com/flying/diamond-da40
Here is the Honda’s tech paper about the SHM-1 airfoil (which was designed for the Honda-Jet). The airfoil includes features which are not important on low speed low Reynolds number flight but it also has features which makes it ideal for lower speed concepts:
http://hondajet.honda.com/pdf/tech_papers/Journal_of_Aircraft_Vol40_No4_P609_P615_SHM_1_NLF.pdf
SHM-1 could be a good starting point for an airfoil for GA-use. The Re area for the SHM-1 is a lot higher than needed by GA, so it may not be directly applicable, but the ideology in the SHM-1 seems just what would be needed for also high speed high efficiency, long endurance GA aircraft, which in addition to having low drag and high Clmax also exhibits good behavior.
Axial Flow Propulsor for Small Aircraft
Computational Fluid Dynamic Simulation (CFD) and Experimental Study on Wing-external Store Aerodynamic Interference
Design of Carbon Composite Driveshaft for Ultralight Aircraft Propulsion System
Flying Wings. A New Paradigm for Civil Aviation?
Rapid Prediction of Configuration Aerodynamics in the ConceptualDesign Phase
Design of a Three Surfaces R/C Aircraft Model
Response of a Light Aircraft Under Gust Loads
FEM MODELLING OF COMPOSITE STRUCTURES AND EXPERIMENTAL COMPARISON
www.vgtu.lt/english/editions/aviation/dokumentai/Nr_01.pdf
I found interesting paper which tells some details about some ultralight aircraft, the better, even about the TL-96 Star we previously owned. I find it quite interesting.
http://ctn.cvut.cz/ap/download.php?id=77
I have stated here previously that the boundary layer suction maybe requires jet engine for having enough power to be wasted for the suction. However, a knowledgeable friend just sent me couple of (more) links as he has used to do now for quite some time. (Thanks by the way). Interestingly enough on this ppt: www.aoe.vt.edu/~mason/Mason_f/LaminarFlowS04.ppt on page 17 it has been stated that the example case of Piper Super Cub only required 2.0 hp for suction. Another example was Cessna L-19 with 17 hp used for suction.
This is very interesting since taking 2-17 hp out of e.g. 200 total hp (=2 x Rotax 914) is quite doable. With smaller engine power as the previously discussed 2 x HKS700E, the available excess horse power for suction would be obviously smaller and taking 7 hp out of the available thrust would be unwelcome whereas taking only 2 hp out of it would be clearly still within limits of potentially feasible and that benefit outweights the loss.
The achieved Clmax increase with boundary layer suction is significant. If on the Cessna example the Clmax increased from 2.5 to 5.0, that makes a whole lot of difference in wing sizing and in turn this affects drag and efficiency significantly.
The downside is that if the wing sizing is done with the expectation of Clmax of 5.0, and then because of mechanical failure, the suction is not available, the stall speed in such emergency would be high. Also potential failure modes are that the suction disappears on final approach or shortly after takeoff.
How to mitigate this potential problem? The suction mechanism would need to be very reliable and most likely it should be doubled. In other words, in twin engine aircraft, either engine should alone be able to supply enough suction so that in case of engine failure of one suction pump failure, the aircraft would not crash but could still safely land on the airport (with the remaining engine and remaining suction pump).
Another way to mitigate the problem could be to not count on the achieved Clmax but only take the benefit of the drag reduction caused by the suction. There comes the question then of the justification of the added complexity. One of the unknown issue to me is that how water ingesting through the perforated skin would be dealt with – it would be pretty severe condition to have whole suction slot full of water. In addition to the suction not functioning properly, the wing would weight significantly more.
What the complexity adds to the manufacturing cost? For small commercial general aviation aircraft (which is targeted to masses and which does not try to achieve anything special but be good all-arounder) it could add more than is justified for the benefits gained from market – simplicity and low cost manufacturing drive these rather than the last decimals in the efficiency. However, for experimental prototype aircraft which is built on basis that price of a work hour is not counted, at least then this might be a feasible idea to incorporate. This would require more investigation, and it could depend quite much on the aircraft configuration, how much gains this could add and what kind of tradeoffs there are to be expected in turn.
Here is the latest version of this (currently command line based but later planned to have a Qt UI) utility. The binary is for MacOSX Leopard (Intel binary). You should run it from terminal.
Karoliina’s airplane design utility 0.1
How to use (shows couple of iterations for a small two place twin engine aircraft using two HKS700E engines):
Changes:
http://www.katix.org/karoliina/packages/ChangeLog_head.txt
The program compiles without modifications under Ubuntu Intrepid. Windows version is not available or planned at this time. No support for the usage for the program will be given at this time.
jcoxon77’s photostream, Flicr:
http://www.flickr.com/photos/jcoxon77/
They look pretty cool, don’t they?
But 76500 ft looks even cooler:
http://www.flickr.com/photos/nebarnix/sets/72157607393699828/
Interestingly though, 42000 ft still looks pretty amazing:
Seems like, yes it did 
Created with the latest iRhino alpha.
Changes:
* Placeholder engine nacelles added.
* Rudder added
I was reading today the book “Fluid dynamic drag” a bit and got kind of inspired: canopies and wind shield discontinuity contributes very much to the drag coefficient of the fuselage. Not only the laminar nose seems important, but all kinds of places where something ends and something else continues are sources of waste of engery.
So if the plane is completely faired with no discontinuity of any kind, theoretically the drag coefficient should be very low.
In this picture, the engine nacelle placeholders are just placeholders, because they are not yet accurate airfoil, and it has not been taken into account that in Rotax engines the propeller shaft is not in the middle of the engine, but almost on the top of the engine, this creates a fairing that has the lower side turned up a bit and is therefore not completely symmetrical.
The engine nacelles may need to be moved outwards, otherwise there is not enough clearance between the fuselage and the propeller arc.
I was also reading one day some NASA tech paper about wing tip mounted propellers. I have not drawn such things to this picture, but I may add it later – small brushless DC motor on each wing tip lowers the induced drag quite a bit according to the tech paper (although on high aspect ratio wing the effect is not that radical as on with a low aspect ratio wing that would otherwise be poor).
Potential issues for placing engine nacelles on wings (which seems pretty necessary for a twin, after all, may be the least bad compromise) and blending are the followings:
* the wings take a lot room to build (because they are very long)
* making the mold is difficult, because it has to be done from CNC cut pieces and glued together
* moving the center section to airport or transporting it in a container may be challenging, because if the area up to engine nacelles is continuous part of the center section and not separatable, it means that this is basically wider than the width of the container, shipping the plane to another continent might be a challenge (it seems that it would need to be flown like the design point has been set)
I recently created a new song ( these can be found from my music blog from http://karoliinamusic.blogspot.com ) and here is a shortened version of it which I tried to make useful as use as a ring tone for mobile devices. It is a bit more equalized and bit more compressed also than the hifi-version of the song. By all means, you can use also the actual song as a ring tone, but this has been cut to start from the middle to be more useful – ring tones usually play only a short time and long intro part is not very useful on them then.
I have this on my N810 and also in my N95 and I think it works pretty well. You can in principle use it with any mobile device which understands mp3 format and allows you to assign these files as ring tones.
I am planning to do a measurement of the frequency response of the tiny speakers to equalize this better for them (now this has too much mid frequencies maybe for the tiny speakers, because this mix is still “almost hifi”). I haven’t done that yet, I should dig my measurement microphone from storage to be able to do that (the Internet tablet / phone mix would be counter-equalized with that). However, this version already works on your device, so feel free to use it.
Download it from here:
Sky Party – ring tone version 1
The file bitrate is 128 kbit/s and the file size is 2188433 bytes which is around 2MB. You can install it by for example reading this with the N810, saving the file and then assigning it as a ring tone for the internet call. Alternatively you can download it with your computer, use the USB cable to connect the computer to the device and then copy the file to the device’s file system.
If you are using Mac to download the file (instead of the mentioned Internet tablet for example), you may need to right click the file with CTRL + mouse button or otherwise the Quicktime starts to play it instead of downloading the file.
All feedback is welcome.
Hey watch this out:
http://www.youtube.com/watch?v=bU2elPTJyqA
Pretty interesting system built around the Subaru.
I have been thinking one idea for better utilizing the HALE concept (HALE = high altitude, long endurance).
Usually nobody flies higher than about 40000 ft. If you look out from a commercial passenger aircraft’s window, what you see is blue. You can don’t even see clouds very well since you are too high to see them closely and you are too low to see the curvature of the Earth and blackness of space. And the publicly available photography from that altitude is very limited, you don’t really get to see even virtually how it looks like up there.
There are some interesting videos about balloon flights to high altitude in Youtube. The balloons go to about 80-100 kilofeets. According to videos, that looks already almost like space. Couple of examples:
Long Trail School High Altitude Balloon at Youtube
The view is so amazing that I feel it odd that nobody has started to carry people to near space experience with high altitude aircraft. Someone offers MIG-flights, but that is just a ballistic jump there from supersonic flight. Aircraft that can loiter in that altitude would give a whole different experience, it could stay there longer than just minutes.
That kind of aircraft would be impossible someone might say? Not so black and white. There are couple of HALE UAVs around which can go this high. And if you for example look Scaled Composites Proteus which can reach 70000 ft, if you’d replace the telecommunications load from the center section with space grade pressurized passenger cabin, the plane could lift several people at one time to the abovementioned altitude.
According to material I have been seeing from high altitude balloons, it seems like the sky is starting to look like space from about 60000 ft upwards. You need afterburning jet engines to go that high? Not necessarily. Look at for example Burt Rutan’s UAV that had twin turbocharged modified Rotax 914 (with fuel injection). It was designed to have positive climb rate at 63000 ft. Seems feasible with piston engines in other words. The company that did the Rotax-conversion for the Scaled Composites UAV, have done triple turbocharged and twin turbocharged versions of the Rotax. The triple turbocharged Rotax is usable to over 80 kft, however, the installation looks really complicated (and the biggest turbo is so huge that must be from a truck).
Here is a design paper about Tecnam P2006T. I find it quite interesting.
www.aidaa.it/3-2008/P2006_corr.pdf
Interesting detail with the used Rotax 912S is that it provides actually better thrust at takeoff and climb than same horse power with a Lycoming engine (because the engine nacelle has smaller frontal area and the propeller rotation speed is lower).
A workmate asked what my xorg.conf contains. So here it comes:
karoliina@aurora:~$ more /etc/X11/xorg.conf
# nvidia-settings: X configuration file generated by nvidia-settings
# nvidia-settings: version 1.0 (buildd@rothera) Mon Oct 13 14:53:48 UTC 2008
# nvidia-xconfig: X configuration file generated by nvidia-xconfig
# nvidia-xconfig: version 1.0 (buildmeister@builder63) Wed Oct 1 15:09:35 PDT 2008
Section “ServerLayout”
Identifier “Layout0″
Screen 0 “Screen0″ 0 0
InputDevice “Keyboard0″ “CoreKeyboard”
InputDevice “Mouse0″ “CorePointer”
EndSection
Section “Files”
EndSection
Section “Module”
Load “dbe”
Load “extmod”
Load “type1″
Load “freetype”
Load “glx”
Load “dri”
EndSection
Section “ServerFlags”
Option “Xinerama” “0″
EndSection
Section “InputDevice”
# generated from default
Identifier “Mouse0″
Driver “mouse”
Option “Protocol” “auto”
Option “Device” “/dev/psaux”
Option “Emulate3Buttons” “no”
Option “ZAxisMapping” “4 5″
EndSection
Section “InputDevice”
# generated from default
Identifier “Keyboard0″
Driver “kbd”
EndSection
Section “Monitor”
Identifier “Monitor0″
VendorName “Unknown”
ModelName “IBM”
HorizSync 53.2 – 63.9
VertRefresh 50.0 – 60.0
Option “DPMS”
EndSection
Section “Device”
Identifier “Device0″
Driver “nvidia”
VendorName “NVIDIA Corporation”
BoardName “Quadro FX 570M”
EndSection
Section “Screen”
Identifier “Screen0″
Device “Device0″
Monitor “Monitor0″
DefaultDepth 24
Option “TwinView” “1″
Option “metamodes” “DFP-0: nvidia-auto-select +0+0, DFP-1: nvidia-auto-select +1680+0″
SubSection “Display”
Depth 24
EndSubSection
EndSection
I last night transformed the Sky Party concept I presented here earlier into a full length song. I am suffering from some sleep deprivation now, but I think it came up pretty nicely together. Here is the link to the mp3:
Sky Party in San Francisco.mp3
The song deserves to be played with a subwoofer and loud. You can imagine me playing this on the Borel Hill next to Silicon Valley (that was the idea I had when I was composing, the source of inspiration so to speak). Enjoy!
You can place this song to your profile in Facebook by searching the song in the iLike Facebook app.
My iLike page can be found from here:
http://www.ilike.com/artist/Karoliina+Salminen/
Song page is here:
http://www.ilike.com/artist/Karoliina+Salminen/track/Sky+Party+in+San+Francisco
Every song has a some kind of story. Here comes the story of this song:
“Close your eyes. Take a deep breath and drift away, drift away for couple of minutes. Imagine a trance party in top of the Borel Hill (next to Skyline Boulevard), near to Silicon Valley and San Francisco.
You arrive at the party in a hybrid car Toyota Prius. There are couple of electric cars and hybrid cars parked on the parking place. You drive via the Skyline Boulevard and you see the altitude getting higher and higher. Pine trees go by on the sides of the road. You find a parking place with a superb view to Silicon Valley. You cross the road, follow the trail and climb up to the hill and join the party.
You see to both Silicon Valley and to the Pacific ocean at the same time. It almost sunset and there are status clouds on top of Half Moon Bay (and Pacific Ocean). You can see these clouds from the top side and the red and orange colors of the sun setting down. The view is awesome. You look at the another direction. You can see the lights of San Francisco coming up, planes taking off and landing on San Francisco International airport, small planes landing on Palo Alto and San Carlos. You can see also the enormous Moffett field building. Lights are coming up as the day darkens. Palo Alto and Mountain View are directly on front of you down when you look to the San Francisco Bay side.
The grass-filled hill looks really beautiful in the sunset as the day is about to turn to night. You can see the marvellous colors and enjoy the view and enjoy the party. It is called a Sky Party!”
Here is my today’s result from iRhino:
The idea is that the fuselage center section blends into wings like on blended wing body, but it only forms a minor portion of the shape, high aspect ratio wings continue from the blended part and there is a tail in the rear. I have not drawn this as I was thinking because I have been thinking either V-tail or T-tail. This picture doesn’t yet have a rudder.
Now the difficulty is that I have hard time on getting the Rhino do what I think. The loft is challenging, because it follows airfoil shape, it follows the configuration and contour from the top I was thinking, but the problem is to vary the airfoil shape in the center section so that the transition from the right side to the left side is smooth and more circular than in this thing where it is pretty sharp (the sharpness there is completely unintentional and will go away as soon as I figure how to loft this thing properly).
The wing tips did not loft as I planned, and also the elevator has wrong airfoil shape in the tip, the scale2D produced results I was not planning to get. There is still something to learn in Rhino. I need to ask from maybe Jani tomorrow how to do this right.
I spent the weekend in Nummela. Jarmo Hakala was teaching composite fabrication there. We learned for example vacuum bagging and infusion molding techniques.
The infusion molding is surprisingly easy and doable. And it is not that expensive after all, all the materials needed (almost all) can be obtained from Etola. The only more expensive special thing wasted each time in the process is the sealing tape. That is available from the composite resellers only to my understanding (for example from Kevra in Finland). Of course the vacuum pump is needed and it needs to be very strong (not a lo-vac pump, but quite high vacuum to be powerful enough to make the resin to move in the molded part being wet out).
The infusion molding is especially handy when there are multiple layers on the part, and laying up them by hand would take lots of time. The infusion process is a lot more convenient, everything is placed when the part is dry etc. No sticky stuff involved. And everything happens by itself inside the bag. Biggest time goes to the preparation, e.g. making the bag completely sealed. It can not have any leaks, if it has, the part will fail.
I will try this out with the RC model(s) I am going to fabricate next. We have two vacuum pumps and one venturi tube (that creates vacuum from ordinary compressor) to try this out. Lets see how it works out at home. At the course it felt easy at least. With this process, providing that the bag is completely sealed and the resin is injected from proper places in, the quality of the end product can be very high, virtually almost eliminating sanding process.
I found an article about high altitude UAVs, and the Rotax 912 modification for Raptor UAV is mentioned here:
http://www.cre8tivenergy.com/uav.htm
(Quite interesting two stage turbo installation)
If you feel sad and don’t have enough energy, here is the cure. Sky-party in San Francisco (preview, unfinished):
These lyrics play in my head: “I am moving to San Francisco, where I am going to play in a disco…”
Hmm…
Here are some memories from the San Francisco Bay area as still images:
 |
| San Francisco Bay Area |
As with the aerodynamics, I am also in a continuous learning mode with composite fabrication and also metalwork. We just purchased a TIG welding machine. That seems like a welding machine that have courage to try out, it is almost like using gas-welding but with a little arc. Hmm. like a little tesla-coil? How the arc behaves seems to be adjustable and e.g. it seems possible to avoid the crater when stopping weld by adjusting the time how long it takes for the arc to diminish. There are many adjustments in the machine and there is lot to learn. And we tried yesterday. Welding aluminum is tricky, it suddenly melts without prior warning. And even after that, it continues to melt more, if I didn’t pay attention how long I heated it up. Anyway, seems like a fun challenge to master TIG-welding of aluminum. These things may be obvious for professional welders, but you know, they don’t teach welding to engineers. One must start from somewhere. I will use the TIG-welding machine for construction of the big CNC machine that we have been planning with Kate for quite some time by now. A big CNC is needed for creating fuselage and wing plugs. Doing it inaccurately manually seems like great waste of time (have been trying and have found that it does not pay off, a better method is worth to be investigated – I don’t take any “facts” for granted, unless I agree with the results and have compared the method to alternatives and found it to be the best for that purpose (by the way, different parts may require different kind of construction method, optimal is not always only one method)).
I have been researching also alternative materials since I obtained the Cozy MKIV plans (which I am not building right now). So I have pretty unused 20 kg can of MGS L285. Nothing wrong with the epoxy, but I just found out a better epoxy: The Hybtonite obviously – the carbon nanotube epoxy. The price seems competitive with the MGS (read: the MGS is overpriced because of shipping costs from Germany) and with about the same amount of money I could as well use this “breakthrough material”. It does not change the world by itself, but it can add some welcome stiffness to pieces that might be otherwise too flexible. If I hadn’t have this 20 kg unused can of MGS, I would be screaming and ordering a 20 kg can of Hybtonite right now. But having this unused epoxy in the garage a kind of slows the process down since I have lots of money invested in that can and the epoxy has limited shelf life. The Amroy representative is saying that the carbon nanotube material should be as safe as any other composite material (read: not more hazardous than epoxy is already, which is hazardous by definition).
I have been discussing off-line with one UAV/RC-plane designer. He has given me lots of valuable links. I may publish some of them sometime later on this blog, so stay tuned. I am not mentioning his name now, because I am not sure if he wants to be mentioned, but anyway, I find the information found this way quite interesting and helpful. As I have been reading these documents, it has also occurred to me sometimes, that what if the configuration layout would have looks and styling as one major parameter. In my opinion, B2 way the coolest publicly known aircraft out there. So I kind of love flying wings. But I have many reasons to not be thinking of designing a flying wing, for aerodynamic and stability standpoint. But one of the configurations (that I have known before of course, but these documents were kind of reminding me about those, that some find them actually useful over the conventional configuration) – the joint wing. What if you take a B2, use no twist – ie. make a normal main wing, and put a inverted V-tail into it in a box wing configuration so that the inverted V-tail starts from the wing tips, and it avoids yet another intersection by not connecting to the fuselage anywhere. This might make the controls a bit tricky, would mean wire in mechanical control rather than push-rods. Or maybe it could be a hybrid of fly-by-wire and manual control: aileron control could be manual and the elevator and rudder (and the mixing of the two) could be handled with electronics and servo motors would drive these surfaces. Would require very powerful servo motors though (needs to be very fast and very strong). But I have been sometimes kind of thinking this kind of fly-by-wire. Before someone screams that fly-by-wire takes hundreds of years to develop, I would like to remind that it is simple RC-plane technology that people are using all the time in the simplest form – fly-by-wire does not need to mean computerized flight controls and a aerodynamically unstable aircraft by definition. A electric wire weights less than a push-rod anyway when the length is very long (e.g. high aspect ratio wing, and in this case, something that starts from the wing tip). This configuration would make the cockpit very wide and not very tall. The looks would be compromised quite quickly if the cockpit part would protrude significantly from the wing. Obviously the cockpit section would be seamlessly blended into the wing. The interesting challenge here would be: how to make that work okay and minimize associated penalties rather than the motivation to choose this would be some parameter obtained from this configuration. At least it is that way until it is proven that this unorthodox configuration could be any good. At least it could be fun to make a RC-plane like that. And I would paint it to black. Full size plane would be trickier with the color, but there is high Tg Hybtonite available too. A realistic process could be infusion moulding with the hybtonite epoxy (I will investigate this at some point in the future, investing in process can pay back in construction phase significantly, instead of spending 20 years for sanding, I rather think first couple of years and try to optimize the actual construction work to not take 20 years). This would be a kind of alternative for carbon/glass prepregs.
You may find out that Xfoil is not in the Ubuntu repositories. For compiling the source package, you need g77 compiler, but that is not included to Ubuntu Intrepid repositories right now and getting it to work from the source seems to be a lot of trouble. Here is what I found, after some digging, a ready made package which installed on Ubuntu Intrepid fine:
http://giuschet.altervista.org/Ubuntu/
Download the file and install with
sudo dpkg -i xfoil_6.97-1_i386.deb
If some of the dependending libraries are missing, just install those from Intrepid repository and it works fine without problems. Have fun!
For more reading about XFoil, please see:
Xfoil manual
Xfoil tutorial with illustrations
Terrabreak.org XFoil tutorial
More on Xfoil at mh-aerotools
I described earlier on one blog entry how to make fuselage cross sections with iRhino easily. Here is the illustration of the lofted object cut to cross sections:
Cross sections, perspective:
Cross sections from front (simplified):
The source model:
The lofting capabilities of iRhino are awesome, it is easy to create shapes that would be impossible to come up with 2D cad models. I continue to be amazed with the quality of Rhino and I am also more and more convinced that there is no need for a 2D drawing program, I can do everything with Rhino. We are going to model our house next (which will not be discussed on this blog because it is not on-topic), while it is excellent for uniform 3D-shapes, it works so nicely with 2D shapes as well that it would be quite lame to spend all the time for nothing with AutoCAD (I am still getting shivers about the bad user interface, how simple things could take enormous amount of time to do and how innovation could get killed by the tool, we used to use that program when I was doing my studies, it is like completely from different planet than Rhino, and it is not a compliment for AutoCAD) where the work can be completed in matter of minutes in the Rhino..
I, like many others, have been thinking the state of the current air travel system. With all the security checks and check-ins, the travel time becomes long. And easily using car, train or bus wins the passenger plane in the spent time for traveling from place A to B.
In other words, if you fly from Helsinki to Tampere, you can expect the check-in etc. to take at least 1.5 hours prior to the flight and then the flight takes maybe 0.5 hours. It might be also late, cancelled etc., and if this is a connecting flight, you may need to wait for your flight for another 5 hours sitting at the airport. On the other side you are waiting for your luggage to come, and it may take easily 0.5 hours.
So the shortest time with check-in luggage to travel from Helsinki to Tampere is maybe 1.5+0.5+0.5 hours = 2.5 hours. You may have also spent 60-70 euros for taxi from home to the airport, and on the other side the same amount of money to taxi. This makes moving from Helsinki to Tampere to be 180/2.5 = 72 km/h.
What about if this was a connecting flight that you waited for 5 hours and which was one hour late. That makes 5+1+0.5+0.5 = 7 hours. This makes the speed 180/7.0 = 25 km/h. You could beat the plane with a bicycle!
How about if you used a light aircraft to fly by yourself:
- Getting to the airport takes the same time, although it is easier to get to the Malmi airport than to Helsinki-Vantaa with public transportation without paying the large Taxi fee.
- Doing pre-flight check for the plane takes 0.5 hours. If you are quick, you have filed flight plan etc. during this time too. You may be able to speed this up if you are not flying alone.
- If the plane flies 222 km/h on average (includes takeoff and landing), taxi tie down etc. time is accounted with +0.5 hours (includes both airports), the total time to fly to Tampere would be: 0.5 + 0.5 + 180/222.0 = 1.81 hours. This is 99 km/h.
So the slow light general aviation plane is faster than the airliner on this trip. It doesn’t win use of car though, getting to the airport and from the another airport takes time. But it wins train, because in case of train, you would have to get to the train station, and get from the train station to your destination with public transportation, which adds easily 0.5 hours on both ends, even Pendolino is therefore slower than the private car on this distance, so it is not better than using the personal aircraft.
How about if the light plane was a bit faster. It would travel 300 km/h. The travel time would become 1.6 hours. This is 112.5 km/h. Actually you can save fuel on Toyota Prius if you travel 112.5 km/h. And you are sooner directly at your destination. Not bad though for the plane. Wins the airliner hands down even in the best case.
If the distance was a bit longer, it would change the other way. The private plane would be a lot faster way to travel than car. And the airline would still have the overhead associated with security checks, package check-ins, package claims etc. For example, already if you would be going to Kuopio or Jyväskylä, the personal aircraft would be faster than the private car. And still the airliner would be the loser in the speed.
If you would go to e.g. Tallinn, Estonia, then the private plane would be excellent choice. That is because you can’t go there by car, you have to use some transportation in between (e.g. boat). Even fastest boats are slow compared to even small ultralight aircraft. You could take the airliner, but it would take very long to get to the destination because of the overhead taking place at the airport. Instead if you took off with private plane, the overhead can be made smaller.
This of course requires that the plane could be flown in all weather and it would be simple to operate, with no need to do complicated tasks prior to flight in the pre-flight check. Something that would be for personal travel like a family car rather than for “flying sport”. And the plane should be very low drag and very high efficiency design to make it compete in the fuel burn with the car (competing with e.g. Toyota Prius with a plane is very tough – the fuel budget for 100 km would be about 5 liters to be equal). Many current aircraft are not like that. But I feel that there would be use for that kind of planes, and this would not be impossible.
Here is by the way a video I recorded last May in the California trip. This video is about flight from Mojave Space Port to Palo Alto.
Cirrus SR20 flight from Mojave to Palo Alto (raw footage) from Karoliina Salminen on Vimeo.
Here is Gizmag’s article about Eclipse EJC:
http://www.gizmag.com/go/7668/
Pictures on Airliners.net:
I got an idea how to achieve suction to the read of the engine pod.
* The prop is located just after the laminar-turbulent transition to the pod and the remainings of the pod is a very large spinner which is open from the center.
* The air tunnel inside the pod has venturi-shape.
* There are tunnels that connect the venturi tube and the ring that is supposed to have suction.
* Airflow (which is used to engine cooling) inside the venturi (helped with the propeller part that is inside the pod) causes suction to the rear of the pod. The air exits at the end of the venturi tube, which happens to be the center of the spinner.
* The exhaust in the center makes the cut aft end of the spinner to still maintain low drag, it functions in the same way as the rear cut fuselages in jets
I have not tested this idea and don’t know it it would work, but I think it would be pretty easy to try out in the model scale, even with an electric motor. This interests me enough that I think I am going to try it out of someone doesn’t tell me (with better knowledge, as a fact that has been proven and tested) that it is not gonna work.
I hereby license this invention under the terms and conditions of GNU General Public License, version 3, or any later version. (C) 2008 Karoliina Salminen. All rights reserved. By reading this text, you aknowledge this and agree with the terms and conditions of the GPL license.
Today a colleague (Jani Ylinen, a graphics designer who knows everything about Rhino and Maya) from Nokia helped me out with Rhino a bit. So here is what I learned today.
If there is need to make 2D cross sections of for example of the fuselage, it can be done as follows:
1. Create a rectangular surface.
2. Make rectangular array of it. Adjust proper step to proper direction and use appropriate number of copies. E.g. 100 cross sections, one per each 5 cm for example.
3. Then choose Object intersection. Select all items (the rectangles plus the 3D model that you are going to cut apart)
4. Hit enter and wait that iRhino does the processing. It is slow in the current alpha-version.
5. Move the cross sections to another layer
6. Hide the 3D object layer
7. And you have cross sections. You can export these to in dxf format to for example to Qcad and process them further there. E.g. you can plot them to paper. Printing from Rhino is possible as well, but it prints the zoom level of a view that is currently present, and the scale you get can be about anything (not something that you can repeat for each model and do exactly the same scale drawings on paper each time, does not succeed with Rhino printing capabilities).
Jani also showed how to do radius. Select radius tool, select surfaces and type the radius and hit enter. Magically the radius appears to the piece with amazing accuracy.
There is also a silhouette function that makes a 2D projection out of the wireframe. You can propably utilize that in a 2D Cad, e.g. QCad (or Autocad if you are wealthy enough to have the overpriced licence to that outdated software).
I learned today that actually Rhino can be used for technical drawing without using more traditional technical drawing programs. You need to keep your model history with layers manually (if you change some cross section for example, you need to loft again), but with some work, it seems to be all you need. Also measurements can be handled, but you need to maintain them manually too, if you change some shape, you may need to update your dimension as well. With cutaways with the cross sections and the silhouette function, it seems that all sorts of technical drawing can be done with Rhino. It is different and some things are very manual, but on the other hand, as a bonus, the 3D side is so blazingly good that there is nothing that compares with it in user friendliness and expressivity. You can really create with this tool and about everything is there, you just need to discover all the functions.
Seems like the price-value ratio of Rhino is exceptionally good. With one thousand you can get so nice tool that it actually is better and especially a lot easier to use than overpriced Autodesk tools. This is how the design is done in the future for sure.
I am also downloading the Maya personal edition for Mac now. I plan to try it out for rendering models modeled in iRhino.
Many thanks to Jani for guidance with graphics software. It is very much fun to learn new things.
Carlos from RCAdvisor commented my one post and I decided to check out his site. I created user account there etc. I was really amazed the RC Calculator, it not only has quite amazing features for model makers, but it also seems to have quite interesting animated UI, I didn’t know that this kind of stuff can be nowadays done with Java (or is it flash?). I haven’t had time to yet surf what all is on this site, but it looks quite comprehensive and promising and I will for sure look further into it. Indeed, maybe I find some tips for the twin concept RC-scale model I am going to do. Thanks Carlos for your link!
the link to the RCAdvisor
I decided to post here a snapshot of one of my Rhino-models. It has now struts which hold the engines out of the wing surface. The canopy was also replaced with windows.
Just a quick experiment on the ambient side. Ambient soundscape.
Try it out if you wish:
FallingIntoJupiter.mp3
The script goes like this:
- you are far away from Jupiter, approaching it on a trajectory which does not end up to a Jupiter orbit. Instead you are falling. There is nothing between you and the planet, and your speed is increasing and you can do nothing about it. And your headset pick the radiation interference as audio and you hear this thing. You fall between the clouds. Endless clouds in the huge atmosphere which feels like it never ends to a ground. Scary? Feel free to listen and have some ambient fun this time. This is very unusual to me, so please bear with me if it is not too perfect.
I am back, with a blog on another service. I attended the Akademy 2008 and Maemo Summit 2008 conferences. I have created a video of both of them. These are no presentation videos but rather attempt to record the spirit of the time and place to a collection of video clips which are presented in a sequence on these short movies. Both conferences were quite interesting and a success. It was great to meet new people, especially on the Akademy conference, I have been participating many years in the Guadec conferences, but this was my first Akademy.
Here is the Akademy video. Nokia gave devices for KDE developers and I have quite many faces who received one on the video. Have a look if you are interested:
Akademy 2008 KDE conference – Nokia gave out N810 devices for free from Karoliina Salminen on Vimeo.
Kate Alhola had linked to my Maemo summit video on her earlier post. Because of technical issue on her blog software, she embedded the Youtube link. The Youtube offers poor quality, especially the audio quality is severely degraded since Youtube only supports mono sound. Here is the same video in 720p HD quality and stereo in the Vimeo-service (by the way it is the best video service I have found to the date):
Maemo Summit 2008 from Karoliina Salminen on Vimeo.
If you go to the vimeo page, you can watch these videos in 720p HD when you click the full screen button.
There are interesting similarities in the old Luftwaffe aircraft concepts to the modern aircraft flying now:
For example:
Similar to Rutan Boomerang
Similar to Adam A700 (Originally designed by Burt Rutan)
Similar to NASA Oblique wing (which was by the way done by Scaled Composites / Burt Rutan)
Almost like the Rutan SpaceShipOne
Some features of Rutan WhiteKnight 1
Wing dihedral and anhedral similar to Rutan Proteus
From up, this could be mistaken to Rutan Long-Ez
Hey I can find similarities to Rutan Vari-Viggen here
Here is the WhiteKnight 2 configuration obviously
Almost like Adam A500 (originally designed by Burt Rutan)
Ok, then what about these:
RAM-jet, back in 1946
First commercial jet aircraft was DeHaviland Comet. But was it invented there? Doesn’t this have quite recognizable look. The airliners still have this configuration and look.
And finally, but not least, this one:
Governments are still flying people into orbit with less modern hardware than this, and the idea to this one was from 1929 originally!. Think of it – first flights to space were super-ancient designs (non-aerodynamic rockets) instead of what was thought tens of years earlier already. Even Space Shuttle is quite clumsy compared to what this could have been. I would not be surprised to see someday a rendering on a page of a science magazine, which would look exactly like this and have for example the Northrop-Grumman -logo on it. The sad part was that this was only considered as a bomber, everything was some sort of warplane, it somehow didn’t occur to people back then that they could have done the first human space flight earlier than it was done. I wonder why wasn’t Dr. Säger utilized in the space programs which followed couple of tens of years later. I am thinking what could be done if the rocket monorail-train was replaced with a MAGLEV-train (and the track would slope upwards inside a mountain to the altitude of couple of kilometers in a tunnel). Wow. If my hair was short, it would be most likely pointing to the ceiling now.
Seems like to design a novel plane, there are examples of about every possible configuration layout, which have been long forgotten already and nobody has maybe utilized it, it just is waiting for someone to find it. The history of unfinished aircraft concepts seems to be an interesting source for inspiration.
So, if there could have been a orbital space plane already in 1930s or so, and ramjets were thought about already back in the 1940s, how much then air travel has advanced in something like 70 years? Not at all, it seems. With modern materials and tools, the feasibility of these designs have increased, but the idea still is very old. And most modern designs are just copies of each other without anything new and creative.
I created a music video for the Symphonic Dream song. It features Kate flying Diamond DA42 Twin Star.
Enjoy, it is in HD in Vimeo:
If you have wondered why Cirrus has the discontinuity on the wings. This may answer to that to some extent. I have not found any factual information about the airfoil section used on the Cirrus other than that it is a natural laminar flow section. Cirrus VK-30 used the Jeff Viken NLF414F airfoil. I don’t know if the SR20/SR22 uses the same airfoil or a different NLF section.
Anyway in this NASA tech paper it is explained how the stall resistance can be made better with the wing droop. The wing droop on the NASA test C210 actually indeed resembles the discontinuity on the Cirrus SR20/SR22 wing. Please have a look:
Wind tunnel results of the low-speed NLF(1)-0414F airfoil
Notable thing is that the Vmax-probe did not have this wing droop or any other means to prevent tip stall. And it crashed on landing possibly according to NTSB report and Bruce Carmichael’s book, because of unfavorable stalling charasteristics at low Re of the airfoil caused a hard landing (which the pilot did not survive). NLF414F is not to be used without some means to prevent tip stall and to soften the otherwise very sharp stall at low Re.
I find this quite interesting:
http://www.wipo.int/pctdb/en/wo.jsp?IA=US2005047133&wo=2006073954&DISPLAY=DESC
Here is another:
Here are set of requirements I have combined for an aircraft suitable for my use case. I have been collecting these things for quite long time now, and have changed them back and forth. However, it seems like they are becoming more stable now:
- Two engines. Rotax 914 (preferably fuel injected) or similar (912 turbo conversion). Alternate engines: HKS700T (the speed may not be achieved with the HKS option). (low power engines which run on autogas are mandatory requirement)
- Range 1000 nm with three on board (mandatory requirement)
- at least 3 places (mandatory requirement, long range flights, third seat is needed for baggage and rescue equipment)
- Designed for IFR flying (mandatory requirement)
- statically stable, dynamically stable behavior (mandatory requirement)
- gentle stall (mandatory requirement (for safety))
- Cruise speed > 200 kts @ 80% power (mandatory requirement for both range and usefulness)
- Stall speed max 55 kts (mandatory requirement, for safety)
- High altitude capable (cruise at 24000 feet) (optional requirement)
- Pressurization as an option (optional requirement)
- Lightning strike protection (mandatory requirement)
- Positive climb rate with one engine out (mandatory requirement)
- Spin recovery possible (mandatory requirement)
- Very high glide ratio and long glide range when both engines out (mandatory requirement)
- BRS system (mandatory requirement, for safety)
- Spin recovery parachute (mandatory requirement, for testing safety)
- Tri-gear possibly with RG, at least the nosegear with RG mechanism (Trigear mandatory, RG optional)
- At least normal category (mandatory requirement)
- Utility category (optional requirement)
- Reasonable cost to build a prototype
Means how to achieve this:
- Selection of efficient NLF airfoils
- By minimizing fuselage and engine pod wetted area
- By minimizing skin friction drag (smooth surface, gelcoat on top of laminate and polyurethane paint on top of gelcoat)
- By utilizing laminar flow over wings and fuselage as much as possible
- By using wing geometry that has higher effective aspect ratio than actual AR
- Turbocharged engines
- Lightweight molded composite structure manufactured from carbon fiber prepregs, foam.
- By minimizing intersections and protruding elements. As clean fuselage and wing as possible. Known limitations – double slotted flaps do require external mechanism.
- By use of double slotted flaps for high Clmax.
- By use of either T-tail or V-tail for good spin recovery.
- Large fuel tanks in engine pods
- For cost effectivity, a pair of midtime Rotax 912ULs equipped with e.g. VEMS fuel injection and Garrett turbocharger is more reasonable cost than pair of stock Rotax 914s. Downside: ease of installation is lost when the engine requires more work than usual for Rotax installations. However, fuel injection is essential for safety.
- Negative sweep on main wings
- Glass cockpit (IFR requirement)
Possible configurations to achieve this:
- Twin with tractor propellers on each wing (known limitation: the propeller causes turbulent flow behind it which increases drag over the engine pod and the wing behind the propeller arc)
- Twin with pusher propellers on each wing (known limitation: the pod on front of propeller decreases the propeller efficiency)
- Push-pull configuration with twin boom tail (known limitation: front propeller disturbs the airflow to the rear propeller and the efficiency of the rear propeller decreases)
How to verify the effectiveness of each parameter:
- Calculate basic parameters for each combination where only one parameter is altered in each.
- This concept generates several different designs and each parameter is justified if it produces verifiable benefit.
- The design points that are proven to produce positive results with large enough margin are incorporated into the design if it does not overly complicate the manufacturing.
Low hanging fruits (design points known to have been succesfull in other designs):
- Double slotted flaps with a mechanism similar to Dynaero. Proven on Dynaero MCR.
- NLF-airfoils. Proven on Cirrus, Lancair and Columbia (Cessna 350 and Cessna 400 nowadays) high performance aircraft.
- Molded composite structures. Industry standard nowadays in most new aircraft designs.
- Tractor twin. Proven on most twins around.
- Pusher twin. Proven on a Polish design called Orca.
- V-tail. Proven on Beech Bonanza and later Cirrus Jet and Eclipse Jet.
- T-tail. Proven on many aircraft designs to date
- High aspect ratio on twin engine propeller driven aircraft. Proven on Diamond DA42.
- Negative sweep (moderate) found on many dual seat gliders. Small amount of negative sweep can also be found from Diamond aircraft.
- Trapezoid on wings. Easy to manufacture from composite materials, the shape is not limited by manufacturing process.
- Prepreg composites. Proven on Cirrus, Lancair, Diamond and Columbia aircraft.
- Rotax 912 series engines. Proven to be highly reliable and simple workhorse on almost all new ultralight and LSA aircraft. HKS is slowly gaining some share, but Rotax rules so far. From personal experience I also know that the Rotax engines meet their TBO, our flying club frequently runs Rotax engines to their TBO without problem without major overhauls. Claims that TBO of Rotax is just marketing and that overhaul is required well before 1000 hours to that is simply not true, this has been proven by experience, the aircraft we used to own has flown about 1000 hours, and the Rotax is the original one and runs nicely without problems and it has been in hard use because the plane was used for the first 683 hours to train student pilots. Rotax can also run on autogas (actually the preferred fuel is autogas, not 100LL).
- Glass cockpit can be made a lot simpler than tradtional gauges. Wiring behind traditional gauges is a mess and takes a lots of handwork to accomplish. Glass cockpit wiring can be made very simple and it can be highly integrated where most of the tasks are done in software rather than mechanics.
Criteria for defining success and failure
- Minimum acceptable range is 800 nm.
- Minimum acceptable payload with full fuel is three persons with no baggage.
- Minimum acceptable cruise speed at 80% is 160…170 kts on Rotax 912/100 hp. However, when comparing to Rotax 912 twins (coming and existing), the speed is no longer in the “top class”, but rather below the top.
- Minimum acceptable glide ratio is 1:15. Target is more than that.
- Maximum acceptable stall speed is 55 kts. Design requires changes, if it is more than that.
It is not obvious and not clearly described in the qmake help, therefore I am typing what you need to do to here:
qmake -project
qmake -spec macx-g++ yourprojectname.pro
after that you can run:
qmake
make
(And your program is compiled)
You can now edit the pro -file as suits you best. To make it effect again, run qmake without parameters. If you encounter weird errors after changing the .pro -file, it might be because you have not run make clean. So after doing this, always run make clean before attempting to compile, otherwise you may get some headaches about issues that actually do not exist.
A funny idea came into my mind. There are couple of Petrel Amphibians in Finland. It looks like a plane of Donald Duck.
Here is one discussion thread in Finnish about it:
Nyt on suomen kolmas akuankkakone valmis
It has staggered wings (two wings, one on top of each other). What if it was completely different. Not exactly completely, but quite completely. Now on this latest Super Petrel, the engine pod is integrated to the upper wing. How if the upper wing was the only wing on the plane, the lower wing would not exist, the upper wing would be twice as long. The tail would not be angled upwards from the bottom of the fuselage, but it would be rather connected with two booms to the wing, in similar manner than it has been done on Adam A500. And finally, but not least, what if the fuselage was not a traditional fuselage, but a pod in the end of a strut, that fits the occupants, and nothing more. It would end before the prop arc. This would allow moving the propeller a bit downwards.
So the result:
- no aerodynamic penalty normally associated with the amphibian planes.
- center of thrust is at the same level as is the lift (high wing)
- because of the boom tail, the tail does not hit the water unless the plane flips.
- because you would not need to fit the tail to the fuselage, the fuselage-pod could be made a better boat shape
I could not resist, but name this idea as Podrel. Actually this is not a new idea entirely, it is partially borrowed from a NASA tech paper, but the application to amphibian use could be new twist for the configuration.
What do you think about this?
I had a chance to see the Dynaero MCR-01 yesterday at Malmi airport. Here are some interesting pictures about it:
Front:
Dynaero smile:
Back:
Double slotted flaps:
Flap mechanism:
Canopy:
Interesting finding: the upper slot is rigid part of the flap. It does not move by itself, and the mechanism is as simple as on plain flap or the single slotted flap found on Cirrus or Diamond. When the flap is retracted, the slot hides under the wing. Very clever design.
The SHM-1 airfoil seems quite interesting. It was designed for Honda Jet. There is a patent about it. I need to investigate that further it seems.
Everyone knows that there is the wget command in the Ubuntu. But by default its behavior is not very nice if you want to get for example backup of your home directory on the web server only. If you don’t have wget, you can install it by going to shell and typing:
sudo apt-get install wget
Example case: You have lots of pictures on your home page, in images folder. You want to get them all to your Linux desktop, ie. you want to make a backup. But you want only the images, not the other files that are in that folder, what do you do? Or what if you want to download all my music without needing to click download for provided links for each file separately?
I was asking around from the Linux gurus around me, but I could not get a simple answer other than read the man pages. Ok, I went and read the man pages. There were some examples, and they did not do what they promised to do until I combined them to the following:
This does to my music folder on our server a mirror to your hard disk, but it has adverse side effect, it keeps the web server directory stucture:
wget -r -l1 –no-parent -L -A.mp3 http://www.katix.org/karoliina/music/
I just wanted to have the mp3-files from one folder. So I searched further the man page.
Here is the line what did for me what I wanted:
wget -r -l1 –no-parent -L -A.mp3 -p –convert-links -nH -nd -P./ http://www.katix.org/karoliina/music/
It still downloads the robots.txt. But you can go and delete the unnecessary file. And if you want all my music, here is what you can do. In shell (terminal), go to your desired folder and then copy-paste this command line to the shell. And you’ll be done as quickly as the network allows.
I created new music video. It features Maemo Summit 2008 (Berlin, C-base) and the Catdroid song on the background.
Here is the link to Vimeo:
Here is a video about Maemo Summit 2008. It features people attending the conference, C-base and Berlin and has my song “Big cat” as background music.
Maemo Summit 2008 from Karoliina Salminen on Vimeo.
Link:
There is link to the NLF215F airfoil tech paper. It was particularly interesting. Now I understood the philosophy of the profile – I was always wondering, why this profile has the low drag bucket at so high Cl (around 0.5) rather than what is realized in cruise with small aircraft (up to 0.2). But, it seems, that this airfoil is designed to be used with -10 degrees flaps. With those, the low drag bucket gets into the cruise area. Heureka.
Here is a direct link to the paper:
http://www.n91cz.com/Interesting_Technical_Reports/NASA-81-tp1865.pdf
I just downloaded the iPod touch version of the X-plane 9. I am quite impressed about it. It is by far the best mobile game I have ever tried. The controls are done with the accelerometers and throttle and flaps are controlled with two simple finger usable sliders on the screen. The landing gear and brakes have translucent buttons on the bottom of the screen. Everything is fully finger usable as it should.
The aircraft selection consists of Cirrus Vision Jet, Piaggio Avanti, Columbia 400 (that was a positive surprise since it wasn’t included with X-plane before), and the C172SP. Needless to say that the Cirrus Jet is the most fun of these to fly.
It is possible to set the weather to IMC, but because the instrument panel does not fit into the tiny screen, it is not included with the sim. Therefore flying IFR approaches with the iPod version is not possible. You can keep the attitude though inside a cloud because of the HUD that includes attitude indicator.
Anyway, this is the best iPod touch app you can find from the App store. It only costs 7.99 eur and is worth every cent. You can find it under games category.
What could be cooler than fly virtual Cirrus Jet in bus when going to work tomorrow?!
Now I have everything setted up again and usable. Here is a picture:
Here is what I lofted today in the iRhino:
To make reasonable place for the rear seat/seats, the wing position had to be moved lowish position. The feet of the rear passengers are below the wing spar of the wing.
The rear window is not necessarily in the best place, it might be too much forward. The idea is that the rear seat ends before the prop arc.
The single engine idea in the previous post had apparent CG issues, how to get CG to correct position other than moving the prop completely on top of the fuselage, which moved the engine pod very high. This twin engine version which places the engine pods to the wings, solves this issue obviously.
Here is how it was drawn (in the case someone is interested in learning iRhino):
- The engine pod is NACA 66-025. It is lofted from couple of cross sections which were set along a helper-line which had the airfoil contour.
- The Fuselage is lofted from 5 elliptical cross sections
- The wings are lofted from two airfoil cross sections each
- The tail surfaces are lofted from two airfoil cross sections each
- The canopy and window utilize the Project to Surface -function of the iRhino
- The picture is drawn with correct dimensions. I used measurement -lines to make the parts correct size. The grid was set to 10 cm spacing.
The fuselage height is 86 cm, length is 6.6 meters. I have not yet measured if one can fit inside or not. But basically it resembles a sail plane fuselage. The fuselage may require some scaling up to fit more than two persons inside.
Here is yet another concept illustration. The engine pod would contain HKS700T, Rotax 914 or UlPower 260i with pusher propeller.
The idea of the concept is simplicity, low drag and placing the propeller so that the arc does not get under the plane and thus is not vulnerable to flying dirt etc. like it is usually on pusher designs. The high wing is selected just because that way the center of thrust gets closer to the center of lift and the high thrust line does not cause that high nose down pitching moment. The engine pod fits between the V-tail, which makes the concept similar than the Cirrus Jet.
The major idea in this is that the part count is minimal. There are only two tail surfaces, two wing surfaces, and a single fuselage + pod.
I have done an X-plane model like this. In the model, the control sensitivity is low and the plane maneuvers slowly. It is difficult to make the ailerons and elevators effective enough.
I have been thinking how the efficiency of a tandem wing aircraft could be improved. In tandem wing aircraft the front wing determines pretty much how high total Clmax the aircraft is going to have which translates then to the required wing area. To maximize the efficiency, because flaps can not be used in the rear wing, the Clmax of the front wing is desirable to be as high as possible. Usually on tandem wing and canard aircraft the Clmax of the front wing is around 2.0 and the elevator is a single slotted flap.
It may not be mechanically very practical, but theoretically it could be possible to increase the Clmax of the front wing by adding more high lift devices into it. There could be a fowler flap implemented so that it increases the wing area substantially while the single slotted elevator flap remains working as usual in the trailing edge. The problem is that how you do that when the whole elevator system moves as consequence when the flaps are lowered or raised (the fowler is either inside the wing or protruded out of the trailing edge). But if this was practical with any other means than using servo motors for the elevator too, it could increase the available lift from the front wing somewhat. A challenging thing in this obviously is that the shear web that connects the spar caps goes through the front wing, and the flap system can not break the integrity of the shear web. More limiting factor also is that the chord length of a tandem wing aircraft front wing is low and there is not that much space for the high lift device.
Anyway, it would be interesting to try this out with a radio controlled model.
I hereby license this invention under the terms and conditions of GNU General Public License, version 3, or any later version. (C) 2008 Karoliina Salminen. All rights reserved. By reading this text, you aknowledge this and agree with the terms and conditions of the GPL license.
I have been thinking how the efficiency of a tandem wing aircraft could be improved. In tandem wing aircraft the front wing determines pretty much how high total Clmax the aircraft is going to have which translates then to the required wing area. To maximize the efficiency, because flaps can not be used in the rear wing, the Clmax of the front wing is desirable to be as high as possible. Usually on tandem wing and canard aircraft the Clmax of the front wing is around 2.0 and the elevator is a single slotted flap.
It may not be mechanically very practical, but theoretically it could be possible to increase the Clmax of the front wing by adding more high lift devices into it. There could be a fowler flap implemented so that it increases the wing area substantially while the single slotted elevator flap remains working as usual in the trailing edge. The problem is that how you do that when the whole elevator system moves as consequence when the flaps are lowered or raised (the fowler is either inside the wing or protruded out of the trailing edge). But if this was practical with any other means than using servo motors for the elevator too, it could increase the available lift from the front wing somewhat. A challenging thing in this obviously is that the shear web that connects the spar caps goes through the front wing, and the flap system can not break the integrity of the shear web. More limiting factor also is that the chord length of a tandem wing aircraft front wing is low and there is not that much space for the high lift device.
Anyway, it would be interesting to try this out with a radio controlled model.
I have been searching the web for such airfoil, and it seems like there is no such thing in the public domain. At least I have not found one.
For a canard/tandem configured aircraft, the main wing should have very low pitching moment, preferably zero if possible. The flying wing airfoils generally don’t have very extensive laminar flow and they are not that interesting except for some exceptions (found one Wortmann airfoil which has quite high L/D but does not really compare to the drag coefficient of the NLF414F at high reynolds number).
So what I would be looking for would be:
- a thick (16-20%) low reynolds number natural laminar airfoil which has low or zero pitching moment, has design cruise Cl of 0.1-0.2 and which would have comparable drag charasteristics than the NLF414F or not very much higher drag than the NLF414F and which would have design cruise reynolds number around 5 million (not 10 million like the 414F) and which would achieve unflapped Cl of 1.2…1.3 at reynolds number 0.8 million.
So am I looking for an impossible airfoil? If you know that someone has designed and tested in wind tunnel this kind of airfoil, please let me know!
Here is the link for the design paper about NLF-414F
Read by yourself from here:
http://www.lib.ncsu.edu/theses/available/etd-09042003-113959/unrestricted/etd.pdf
I created this today. Couple of hours of tinkering and this just happened. This is not ready, the melody is supposed sustain the two simultaneous melodies full length of the part B, but I haven’t fixed yet just yet and wanted to share you an early preview what might be coming. What do you think? Feel free to give comments.
I have been wondering how the Dynaero wing is constructed specifically. It has aluminum skin and composite structure inside. What kind of structure is pretty nicely described in the following document:
Tätä kirjoitettaessa olen lentänyt DA42:lla vasta alle 10 tuntia, mutta tässä kuitenkin hieman ensikokemuksia koneesta:
- Kone on hyvin ohjattavissa yhden moottorin ollessa käynnissä. Rudder trimmiä tarvitaan (muutoin jalka saisi olla melkein pohjassa), mutta se koneesta löytyy ja se riittää trimmaamaan koneen lentämään eteenpäin. Ohjaintuntuma on kahdella moottorilla yksi parhaista kokeilemistani ja yhdelläkin moottorilla lennettäessä ihan kelpo. DA42:sta on melkeimpä helpompi lentää kuin vaikkapa Cirrus SR22:sta. Mutta koneella on lennettävä yksimoottoritilanteessa varovaisesti tai saattaa menettää korkeutta, ks. edellä seuraava pointsi:
- Yhdellä moottorilla kone nousee aika vaivaisesti, joten proseduuri oli Palo Altosta lähtiessä että jos tulee moottorihäiriö lentoonlähdössä, lennetään suoraan eteenpäin San Carlokseen (edessä) eikä yritetä ajaa takaisin Palo Alton laskukierrokseen. Joten ohjattavuutta on, mutta nousussa tapahtuva moottorihäiriö on aika kriittinen juttu vajaan nousukyvyn vuoksi.
- Koska moottoreissa on turbot, yksimoottoritilanne ei juuri huonone korkeuden kasvaessa. SR20 oli suorastaan pelottavan huonotehoinen Mojaven autiomaasta lentoonlähdettäessä, missä Twin Star nousisi sieltäkin yhtä hyvin kuin meren pinnan tasolta.
- Tähän liittyen, tästä aiheesta on ollut paljon juttua ja itse asiassa DA42 yllätti positiivisesti ohjaustuntumaltaan ja yksimoottorikäyttäytymiseltään. Kaikista puheista mitä on ollut, kuvittelin että kone olisi jotenkin hankala kun yksi moottori on pois pelistä, mutta se oli kyllä minulle yllätys että kone on melkein kuin ei mitään olisi tapahtunut sen jälkeen kun rudder trimmi on kohdallaan, ja sitä ennenkin siitä selviää rudderia painamalla. Ultrissa olen tottunut siihen että sitä rudderia tarvitsee muutenkin voimakkaasti polkea, joten tuo ei tuntunut edes kummalliselta tai hankalalta.
Muuta koneen käyttäytymisestä:
- Koneessa molemmat moottorit pyörivät samaan suuntaan ja ne ovat aika raskaat massat siivissä lähes CG:n tuntumassa, ja siitä aiheutuu hyrrävoimia. Tässä suhteessa lentäminen poikkeaa totutusta, esimerkiksi pitää antaa eri jalkaa kuin tavallisesti yllättävissä tilanteissa – esim. hidaslennossa pitää painaa rudderia ankarasti. Tästä johtuen käyttäytyminen on vähemmän eleganttia kuin yksimoottorisella DA40:llä, jonka ohjaintuntumasta en keksi mitään valitettavaa (siinä on kone joka on suunniteltu niin että sillä on hyvä lentää).
- Kone on vakaampi kuin Cirrus tai Cessna jyrkissä kaarroksissa. Pituustabiilisuus on parempi kuin yksimoottori-Cessnoissa taikka Cirruksessa, mutta ei kuitenkaan yksimoottorisen DA40:n veroinen.
- Trimmi on samanlainen kuin DA40:ssä, ja sillä kone on helppo trimmata tarkasti
- Kone käyttäytyy hyvin minimilentonopeudella (Suomessa ei yleensä minimilentonopeudella lentämistä paljon harjoitella, mutta USA:ssa se on pakollinen jo peruskurssilla, eli pitää ajaa juuri ja juuri sakkauksen yläpuolella, kuitenkaan sakkaamatta konetta, lentosuunta ja korkeus tarkalleen säilyttäen). DA42:lla voi ajaa tällaista nokka pystyssä hidaslentoa niin että suunta ei muutu yhtään ja korkeus pysyy vakiona. Jalkaa joutuu muistaakseni painamaan aika reilusti.
- Laskussa DA42 käyttäytyy aika saman tyyppisesti kuin DA40, eli on hyvin kesy ja helppo laskea, helpompi kuin esim. yksimoottori-Cessnat tai Cirrus. DA42 ei kuitenkaan ole ihan yhtä tunnokas laskussa kuin DA40, vaan suurempi massa ja koko tuntuu, DA42:ssa on enemmän ison koneen tuntu, kone on aavistuksen vähemmän miellyttävä laskutilanteessa kuin DA40.
- Laskuproseduuri tehdään niin että laskeutuminen aloitetaan ottamalla telineet ulos. Ilman telineiden ulosottamista kone ei edes tuppaa hidastua laippanopeuteen kovin helposti, joten telineet ovat loistavat ilmajarrut. Täydet laipat otetaan vasta aivan kiitotien jatkeella. Ilmeisesti sen vuoksi että yksimoottoritilanteessa ylösveto täysillä laipoilla ei ehkä onnistuisi, koska Diamondin laipoista tulee paljon vastusta (laipat ovat split-tyyppiset, ja sen vuoksi niitä ei käytetä lentoonlähdössä, tässä on eroa DA40:een ja Cirrukseen, joissa molemmilla tehdään lentoonlähtö aina ykköslaipoilla).
- Kaikenlainen kaasunkäyttö yms. on koneessa hirveän helppoa FADECista johtuen. Ei laihennuksia, potkurin säätöjä jne., kaikki on automaagista ja kätevää. Platallakin on rullauksessa kätevää ohjailla konetta kaasuvivuilla.
- Toisin kuin DA40:ssä, DA42:ssa on nokkapyöräohjaus. DA42:n nokkapyöräohjaus on melko jähmeä ja tunnoton, ehkä olisin enemmän tykännyt jarruohjauksesta, johon olen Cirruksella tottunut (myös DA40:ssä on jarruohjaus ja vapaasti kääntyvä nokkapyörä).
- Ihan kaikki ei toki ole täydellistä – esim. toisin kuin Cirruksessa, DA42:ssa ei ole säädettäviä penkkejä, mutta polkimet ovat säädettävät. Polkimien säätövaijeri on yllättävän ohutta ja heikkoa tekoa – se jäi kerran käteen – kuin polkupyörän jarruvaijeri. Samaten ohjaamossa on vähemmän tilaa kuin Cirruksen luksussohvalla.
- Niin ja koneen laskutelineet ovat kuulemma sellaiset että niitä ei juuri hajalle saa lentämällä. Rähmäkäpäläkin saa tämän koneen ehjänä alas (eli siinä aika samanlainen kuin DA40). Siipikuormitus on suurempi kuin DA40:ssä, itse asiassa aika samaa luokkaa kuin Cirruksessa. Tästä johtuen kone on tunnottomampi tuulelle kuin DA40, ja sillä voi Cirruksen tavoin tulla kovassa turbulenssissa ja sivutuulessa laskuun ilman että sitä juuri edes huomaa. Lasku on teknisesti kuitenkin helpompi ja vähemmän tarkkaa ajoitusta vaativa kuin Cirruksessa (jonka voi pompotella tyynelläkin kelillä jos ei osaa vetää oikealla hetkellä tasan oikeaa määrää, mutta koneella laskeutuminen ei juuri vaikeudu vaikka tähän lisättäisiin kova turbulenssi ja täysin poikittainen 20kts sivutuuli).
Nythän Diamondilla on tarkoituksena kaiketi tuoda DA42:sta Austro-dieselillä varustettu malli. Kone austro-dieselillä varustettuna on melkein kaikki se mitä lentokoneelta toivoisin, eli melkoinen unelmakone. Ohjaustuntumaltaan ei ihan yhtä hieno fiilistelykone kuin DA40, mutta hyvä kuitenkin, suurin osa lentokoneista on tuntumaltaan tätä konetta huonompia. Jo Thielertillä kone on ihan kelpo, ja ei kyllä Lycosaurus-myllyjä ole ikävä.
Volumes may still need some adjustment and there are playing glitches there and there.
So not final version just yet. Any comments about the current progress?
This is a longer version of the song. I may still add something. But it is here available for download:
Have fun!
New song. This is a beta-version, work in progress. So it is quite short. But you get the idea:
I am quite proud how it sounds together! It utilizes some instruments from symphonic orchestra in addition to pure synthetic sounds.
I used this song also for a video about a cathedral in Mechelen, Belgium (that I recorder when I was there at the Akademy 2008 conference). You can view it here:
Tämä video on kuvattu lokakuussa 2007 Palo Altossa. Tämä oli Katen ensimmäinen lento Cirrus SR20:llä:
Linkki youtubeen
Huomaa: Youtube-videon laatu ei ole yhtä hyvä kuin Vimeo-videossa.
Some numbers from Javafoil using the Drela approximation method (Xfoil after 1991):
NACA 66-020
Parameters: Length 6 meters, diameter from thickest point 1.2 meters:
α Re Cl Cd Cm 0.25 TU TL SU SL L/D A.C.
[°] [-] [-] [-] [-] [-] [-] [-] [-] [-] [-]
0.0 11.60E6 0.000 0.00709 -0.000 0.623 0.623 1.000 1.000 0.000 0.380
So estimated Cd for the fuselage is 0.00709. Doors, antennas, landing gear door, etc. will make it worse.
Bugs and dirt on the fuselage surface and the results becomes:
NACA 66-020
α Re Cl Cd Cm 0.25 TU TL SU SL L/D A.C.
[°] [-] [-] [-] [-] [-] [-] [-] [-] [-] [-]
0.0 11.60E6 0.000 0.01212 -0.000 0.625 0.625 1.000 1.000 0.000 0.380
NACA 66-030 (engine nacelle variant of the laminar body)
m/S = 1
α Re Cl Cd Cm 0.25 TU TL SU SL L/D A.C.
[°] [-] [-] [-] [-] [-] [-] [-] [-] [-] [-]
0.0 11.60E6 0.000 0.00775 -0.000 0.605 0.603 1.000 1.000 0.000 0.456
Cd = 0.00775
With NACA 66-025 the fuselage pod length drops to 4.8 meters.
NACA 66-025
m/S = 1
α Re Cl Cd Cm 0.25 TU TL SU SL L/D A.C.
[°] [-] [-] [-] [-] [-] [-] [-] [-] [-] [-]
0.0 9.28E6 0.000 0.00812 -0.000 0.612 0.612 1.000 1.000 0.000 0.417
Cd = 0.00818
Conclusion: All of these pods provide (according to simulation), a low drag coefficient.
Equivalent drag area for NACA 66-025 assuming body diameter of 1.2 meters:
0.00818*(0.6m*0.6m*3.14159) = 0.00925 m^2 (=0.0823 sq ft)
Hmm. did I calculate correctly? Somehow looks quite small.
This blog contains all my blogs in one.
Why I created this blog? Because I got treated badly in the Blogger service. My aircraft review blog was considered to be contain spam and obviously it was a false positive. I requested review to the blog, but no review has been so far done and my aircraft review blog remains locked. I am really unhappy to the very bad service of Google and hereby created this new blog, which also works as a backup to my postings, so Google don’t get them destroyed.
This is the message I got from the Blogger:
Hello,
Your blog at: http://lentokone.blogspot.com/ has been identified as a potential spam blog. To correct this, please request a review by filling out the form at ….
Your blog will be deleted within 20 days if it isn’t reviewed, and you’ll be unable to publish posts during this time. After we receive your request, we’ll review your blog and unlock it within two business days. If this blog doesn’t belong to you, you don’t have to do anything, and any other blogs you may have won’t be affected.
We find spam by using an automated classifier. Automatic spam detection is inherently fuzzy, and occasionally a blog like yours is flagged incorrectly. We sincerely apologize for this error. By using this kind of system, however, we can dedicate more storage, bandwidth, and engineering resources to bloggers like you instead of to spammers. For more information, please see Blogger Help: http://help.blogger.com/bin/answer.py?answer=42577
Thank you for your understanding and for your help with our spam-fighting efforts.
Sincerely,
The Blogger Team
Bad Google, bad!
I have a bit evolved set of requirements for an aircraft concept to present. They are now as follows:
- safe
* 2 engines
* 2 fuel systems
* 2 propellers
* non-stallable
* non-spinnable
* double avionics
* two batteries
* two electrical systems
* moderate stall speed (<=55 kts)
* good brakes
* good tires and landing gear that does not break from few bounces
- economical
* very low fuel consumption
* must run on autogas or diesel oil
- at least 2 places with side by side seating, in comfort (enough space in cockpit, a lot more than in a Cessna)
- very long endurance
- capable to high altitude flight
- best glide ratio speed as high as feasible (enabling cruising at L/D max).
- very high best L/D ratio (>=1:25)
- low minimum sink rate
- relatively low power required to keep in level flight
- low drag utilizing extensive laminar flow in the fuselage and wings
- lightning strike protection (copper mesh installed to the whole aircraft)
- utility category (+4.4/-2.2G)
- positively stable in all flight conditions (suitable for IFR flight)
- speed brakes / spoilers
- ballistic recovery chute
- strong roll cage around the cockpit, exceeding the current FAR23 requirement at least with factor of two
- keeping aircraft CG on correct place do not require using ballast (no matter if there are two or one person sitting on front seats)
- aircraft can be parked without anyone sitting on it on its normal upright position
- aircraft shall look stylish and out-of-this-worldish
- surface finish has to be smooth
- large enough control panel for fitting IFR instruments (Large EFIS screen + analog backup instruments)
- good visibility outside
- rudder trim
- aileron trim
- elevator trim
- using aircraft systems has to be simple and all procedures has to be very simple and easy to memorize (aircraft shall not be a checklist-machine)
Summary: Different-looking composite aircraft that incorporates extensive laminar flow, does not stall or spin and that you can fly from Europe to Oskosh and back with ease and with peace of mind. Complies or exceeds with FAR23.
Tulipa tuossa käytyä tyyppilennolla Zephyrilläkin. Aiemmin foorumissa suosittelin Zephyriä eikä ennakko-odotus koneesta juurikaan muuttunut.
Melkeimpä yhä voisin toistaa itseäni ja sanoa että se on hyvä kone aloittelijalle, helppo lentää, vakaa, mukavan tuntuinen jämäkkä sauvatuntuma,
ei liian äkäinen, ja kohtuu nopeakin ultraksi, ainakin tuolla 100 hp Rotax 912ULS -moottorilla.
Lentoonlähtö oli rivakka ollakseen kiintopotkurikone ja nousunopeus oli ultralle tyypillinen “kyllä lähtee” eikä mikään maantijyrä jossa on siivet.
Zephyrin niinikään saa niin tarkkaan trimmiin että kädet voi irrottaa ohjaimilta ja kone menee suoraan ja
kuvitella saattaa että matkalennolla jatkuvan kepittämisen tarpeen puuttuminen on varmasti mukava ominaisuus.
Dynonin EFIS oli kanssa ihan kätevä, siihen tottui tosi äkkiä ja
moottorilennosta keinohorisonttiin tottuneena se on horisonttiviivan piirtävänä oikein kätevä laite jyrkissä kaarroksissa ja trimmatessa kone vaakalentoon.
Väitteet EFIS-laitteen hankaluudesta ja sen pitkäaikaisesta oppimiskynnyksessä eivät kyllä pidä ihan paikkaansa, sanotaanko nyt että se on “ihan kuin
lentosimussa”. Hieman isommat numerot tosin saisi olla sekä korkeus että nopeusnäytössä, jotta näkyvyys etenkin repsikan paikallekin olisi kohtuullisen hyvä,
näkyvyys ohjaajalle on riittävä joskaan ei juhlallinen. Perinteisessä keinohorisontissa on kuitenkin kaikki niin pientä ja miniatyyrista että Dynonin ei niin hirveän
isot numerot ovat kuitenkin aika kohtuullisen kokoisia noin suhteessa, joten ei siitä nyt kuitenkaan liiaksi pitäne valittaa.
Näkyvyys ohjaamosta on hyvä eteenpäin, ei ihan yhtä hyvä kuin Starissa, mutta erinomainen verrattuna moottorikoneisiin tai Dynamicciin.
Kone pysyi hyvin hallinnassa myös hidaslennossa ja ohjaustuntuma säilyi hyvänä sakkaukseen saakka.
Termiikissä kone pompotti ehkäpä enemmän kuin Dynamic, mutta ei niin paljoa kuin Star. Korkeutta joutuu paimentamaan tinttikelillä koska
nostot nostavat tätäkin konetta samaan tyyliin kuin Staria, siis eri tuntuinen kuin vaikka Dynamic tässä mielessä.
Koneen laskuasuun saattaminen on yksinkertaista, tehoja pois ja nokkaa ylös myötätuulessa, ja sitten vaan odottelee että nopeus putoaa laippa-alueelle.
Aika helposti se oli sinne pudotettavissa, aika saman tyyppinen kuin muut nykyultrat. Ykköslaipat ulos laippanopeus säilyttäen perus ja finaali.
Kone tuli kiltisti moottorilla vedätettynä sopivassa kulmassa kohti kenttää valorivistön pysyessä melkein loppuun saakka oikein; kaksi punaista ja
kaksi valkoista. Kosketus kenttään tapahtui pehmeästi päätelineille ensimmäisellä yrittämällä ja koneen asento ja nopeus säilyi finaalissa aika hyvin
ilman vatkaamista. Kone siis ei ole suttunuijaohjattava Smiley. Ensimmäinen kone jota olen kokeillut jonka kanssa pääsi sinuiksi jo ekalla laskulla. Tietysti kumuloitunut
tyyppikokoelma lienee osallisena asiaan myös. Rullailu hallille ja kone halliin. Käsijarru mallia polkupyörä/mopo on ehkä varvasjarruun tottuneelle
ekat pari minuuttia outo, mutta ennen kuin on Malmilla asematasolta 18:n odotuksessa, se tuntuu jo ihan luontevalta.
Nopeusmittarin virheestä ei ole allekirjoittaneella parempaa tietoa, mutta keskimäärin mittari lupasi yli 200 km/h ilmanopeuslukemia maanopeuden vaihdellessa suunnasta
riippuen 140 ja 230 km/h välillä joten mistään hitaan pään ultrakevytkoneesta ei ole kysymys, kone houkuttelee matkalentämiseen tällä kuin muillakin ominaisuuksillaan.
Kone ei ole tyyliltään raaseri vaan pikemminkin muistuttaa Diamond DA-40:n eleganttia fiilistä ja luksuskruisailua. Täydellinen tietenkään kone ei voi olla,
ultrien tyypilliseen tapaan siitä löytyi hieman nipottamista kuomumekanismista missä verrokki DA-40:n osat sopivat keskenään just,
eikä niin että vähän sovitetaan ja asetellaan ja sitten vasta menee linksut paikalleen. Turvallisuusmielessä kuomumekanismin lukitus on todennäköisesti
yksi parhaista näkemistäni tähän mennessä ja tuskin pystyy aukeamaan lennolla vaikka löisi pään kovastikin tintissä kuomuun tai vaikka laskusta ei niin
kesysti käyttäytyvällä koneella sitten tulisikaan niin täydellinen.
Istuma-asento koneessa on erinomainen ja toisin kuin ultrissa yleensä, penkin takana on kattoon asti ylettyvä laipio joka toimii niskatukena jos tulee
kolarissa äkkipysäys (esim. pakkolasku). Yleensä ultrakoneissa tyypillisesti ei ole mitään tukea niskan takana ja kolariturvallisuus on tältäosin vielä
siellä 50-60-luvulla vaikka penkki olisi muuten parempi kuin tyypillisen vanhan moottorikoneen Trabant/Lada-laatua oleva penkki jonka suunnittelukriteereihin
ei lienyt kuulunut termit kuten 26g turvaohjaamo (jo varmaan 0.5 g riittää siihen että penkki luiskahtaa kiskoilla asetuskohdalta taka-asentoon mikä on
lähinnä surkuhupaisaa puhuttaessa samaan aikaan tyyppihyväksyttyjen koneiden väitetystä turvallisuudesta (onhan se uusissa koneissa toki huomioitu, kaikissa
Diamondeissa ja Cirruksissa toki on niskatuet ja penkit jotka ei kolistele pitkin kiskoja kuin junat ilman veturinkuljettajaa)…
Koneen huippunopeus on korkeampi kuin koneen VNe, eli koneella pääsee vaakalennossa VNe:n yli täydellä kaasulla. Vihreä kaari loppuu kuitenkin melko aikaisin tässä konetyypissä josta johtuen lähes täyttä kaasua ei voi 100 hp Rotaxilla käyttää ainakaan matalilla lentokorkeuksilla, lentopinnoilla ehkä (kokeilematta vaikea sanoa).
Huomioitava seikka mainospekseistä valmistajan sivulta:
Spekseissä luvattu 220 km/h cruising speed tarkoittaa että ajetaan Rotaxia melko isoilla kierroksilla ja kovalla kulutuksella.
Pilotin valittavana on siten joko pitkä toimintamatka tai suuri nopeus.
Lento-ohjekirja lupaa seuraavaa 60 litran tankeilla varustetusta versiosta:
140 km/h 1070 km toimintamatka
180 km/h 700 km toimintamatka
200 km/h 666 km toimintamatka
220 km/h 515 km toimintamatka
MIK:llä (Malmin Ilmailukerho, http://www.mik.fi) on nyt uusi lentskari, tyyppiä Cessna 172SP. Moottorina on Lycoming IO-360 kunnes se vaihdetaan Thielert Centurion 2.0 -dieseliin. Kokemukset ovat siis tuosta Lycomingista ja 2-lapaisesta kiintopotkurista. Vertailen edelliseen lentämääni moottorikoneeseen, Cirrus SR20:een (edellinen lento ennen OH-SRH -lentoa moottorikoneella (ultralentoja välissä jos ei lasketa), oli koneella N725SB).
Malmin ilmailukerhon Cessna C172SP ennen diesel-konversiota
Kone on vuosimallia 2001 ja hyvässä maalissa ulkoapäin. Peltikoneille tyypillisesti kupukantaiset niitit ovat kohollaan koneen pinnasta. Koneessa ei ole “flush” -niittejä kuten RV-koneissa on tapana vaikka kyseessä on “uusi vuosimalli”.
Nahkasisustus näyttää lentokoneeksi hyvältä vaikka Cirrusmaiseen automaisuuteen on vielä valovuosi matkaa. Mittaripaneelissa on VFR-varustus, kone ei ole IFR-kelpoinen. Mittaritaulun ilme on siisti.
Ohjaamoon kiipeäminen on Cessnamaisen helppoa. Ovi auki ja ei kuin penkille. Säädettävän penkin säätönuppi on ihan samalla paikalla kuin 40 vuotta vanhoissa Cessnoissa, samoin veivi jolla suoritetaan penkin korkeussäätö. Penkin selkänoja on hieman pidempi kuin vanhoissa malleissa ja se näyttää hienommalta ja tuntuukin hieman paremmalta kuin vanhoissa koneissa. Äheltämisestä huolimatta kuitenkin jäi penkin asento säätämättä mukavaksi, istuma-asento on edelleen sama kuin vanhemmissa koneissa ja niissä en ole löytänyt toistaiseksi penkin säätöä jossa penkin etureuna ei painaisi pohkeisiin ja rasittaisi pidemmän päälle. Asiaa ehkä kompensoi aikaisempaa pehmusteiltaan muutoin mukavampi penkki. Bensamoottoriversiossa Cessna-kaasu on edelleen yhtä epäergonominen kuin aina ennekin. Tämä korjaantuu kun koneeseen asennetaan uusi moottori jossa on mukava FADEC-säätö.
Polttoainepumppu ihmetytti, että pitääkö laittaa päälle vai ei. Lopputulos oli että ei laitettu päälle, koska ohjekirjakaan ei sen käyttöä normaalioperoinnissa ohjeistanut käyttämään, ja se siis puuttui check-listan lisäksi ohjekirjasta. Omituisena ominaisuutena oli fuel-shut-off -valve. Eli polttoainevalitsimen lisäksi löytyy nuppi jolla polttoaineen virtaus loppuu. Sen kanssa saa olla varovainen että esim. matkustaja ei vahingossa osu siihen lennon aikana.
Yoke-ohjauksesta johtuen valokatkaisijat jäävät katveeseen Yoken alle, eikä etenkään pimeässä ole helppo tarkistaa mitkä valot ovat päällä muuten kuin käsikopelolla.
Kahden hengen kuormalla ja tankit täynnä bensaa, kone starttasi yllättävän ärhäkästi, moista esitystä en ole ennen Cessnassa havainnut. Nousunopeudeksi vakiintui yli 1000 jalkaa minuutissa, mikä on loistava lukema verrattuna esim. C152:n nousunopeuteen jossa tulee hieman fiilis että nouseekohan tämä nyt tästä ollenkaan. Suorituskyky ainakin mittarilukemana jatkoi yllättämistään, vaakalento saavutettuna mittarissa luki n. 120 kt IAS ja 124 kt TAS. Ihan hyvin Cessnalta. Lienee isompi moottori ja paikallaan olevat muotosuojat vaikuttamassa asiaan. Jotensakin muutenkin oli vähemmän traktorimainen fiilis kuin C172:ssa yleensä. Polkimien tuntuma on luonteva, kuula pysyy keskellä ilman että siihen kiinnittää huomiota.
Koneessa on trimmipyörä edelleen tutussa paikassa josta trimmatakseen täytyy kurottautua. Uutta koneessa kuitenkin on yokessa oleva sähkötrimmi. Cirruksella lentämisen jälkeen siihen oli tottunut ja se tuntui mukavalta nyt myös tässäkin koneessa. Teki trimmaamisesta jopa helppoa.
30 asteen kaarrokset sujuivat ilman pituusakselin suhteen ylös-alas vuoristorataa katsomalla pelkästään mittareita – lento tapahtui pimeässä joten oikean horisontin referenssi oli vajaa tai kokonaan puuttuva. Koneella on varsin helppo tehdä pimeässä 30 asteen kaarroksia (Cirruksessa joutuu paimentamaan jokseenkin enemmän jotta kaarros pysyy halutulla korkeudella). Ohjainten vaste on verkkainen ja Cirruksen energisyys loistaa poissaolollaan. C172 vanhempien veljiensä tapaan on hieman kömpelö kone. Liikehtiminen ei kuitenkaan liene tämän koneen pääasia ja ohjaimet täysin riittävät koneen ohjaamiseen erilaisissa tilanteissa.
Koneen hidastaminen laskukierrosnopeuteen oli varsin helppoa. Laskukierroksessa on vähemmän tekemistä ruiskumoottorin vuoksi (moottorissa luonnollisesti ei ole kaasuttimen esilämmitystä kun siinä ei ole kaasutinta). Nokan ylös trimmaaminen sujui sähkötrimmillä kivasti.
Kaarros finaaliin, nopeudeksi trimmattu 65 kts ja 2 pykälää laippoja ulkona. Toisin kuin Cirruksella, tällä täytyi tehdä tyypillinen Cessna-lasku, eli kentän pinnassa tehot pois ja vetoa yokesta vimmatusti. Matalasta siipikuormituksesta johtuen C172SP on herkkä ilmassa oleville “möykyille”, joten kiitotien alussa oleva “kumpare” aiheutti sivuttaiskeinahtelua kuin isoilla meren aalloilla. Koneen vaste on hieman kömpelö, mutta riittävä asennon korjaamiseen, tosin adrenaliinia erittyy vereen Cirrusta enemmän (Cirrus on ennustettavampi ja siten jokseenkin helpompi laskeutua).
Johtuen laskutelineiden asennosta ja korkeasta ohjauspaneelista, paremman näkyväisyyden koneisiin tottuneena oli taas hieman poistottumista halutusta koneen asennosta loppuvedossa. Cessna näyttä olevan hyvin vedettynä silloin kun se ei ole vielä hyvin vedettynä ja sitä pitää vetää vimmatusti ja melkoisella voimalla, vaikka kone olisikin hyvin trimmattu lähestymisnopeuteen. Koneen vakavuus tulee hieman rauhattomaksi loppuvedon aikana ja polkimia saa käyttää verrokkikonetta enemmän loppuvetoa tehtäessä ja vaatii pilotilta hieman enemmän tarkkaavaisuutta.
Pyöreillä mittareilla varustetussa Cessnassa luonnollisesti erinäiset asiat (kuten polttoaineen määrän tarkistaminen eksaktisti) ei niin hyvin onnistu kuin Avidyne- tai Garmin-lasiohjaamolla. Viisari näyttää jotain epämääräistä ja siitä pitää sitten tulkita että paljonko mahtaa olla jäljellä. Samaten öljynpaine, volttimittari jne. eivät kuulu ergonomisen helppolukuisten mittareiden kastiin. Mukava uutuus nopeusmittarissa on TAS-asteikko.
Audiopaneeli oli helppo käyttää, etenkin kun pidin siitä esitelmän koulutustilaisuudessa. Bendix/Kingin karttanäyttö (samanlainen kuin siinä uudemmassa TL-96 Starissa) on mukava. Näyttö on kirkas ja siinä näkyy maastokartta, ilmatilarajat, kentät, ilmoittautumispisteet ja kaikki. GPS:n omaa pikkunäyttöä ei tullut liiemmin vilkaistua kun tuo isompi näyttö oli mukavampi katsoa. Näytössä oli taustavalon himmennys, mikä oli tarpeen, koska lento tapahtui pimeyden vallitessa.
Kone toimi kaikin puolin moitteettomasti ja suorituskyky yllätti positiivisesti.
Yleisenen fiilis koneesta on että se on mukavampi kuin esim. OH-CTL tai OH-CAU ja selvä parannus vanhoihin kerhon koneisiin.
Jään mielenkiinnolla odottelemaan miltä kone tuntuu lentää uudella dieselmoottorilla. Matkanopeudessa jäädään todennäköisesti häviölle, mutta toisaalta taas Thielert on helpompi operoida, siinä ei ole käsilaihennusta yms. ja sen käynnistämisproseduuri on yksinkertaisempi ja luonnollisesti se tärkein pointti että sillä on selvästi edullisempaa lentää.
Here is the link to information about this very interesting engine:
A solar UAV utilizing Lithium-Sulphur batteries and amorphous silicon solar arrays has made a record flight. Read the BBC NEWS story: BBC: Solar plane makes record flight
Here is a rough illustration about the configuration layout. This picture is not drawn into any scale dimensions, it is just “artistic” illustration of the idea. I did not draw taper to wings etc. because I wanted to draw it quickly. Here is the picture:
The drawing program is by the way the Rhino3D for MacOSX, a pre-beta -version of it, I am privileged to be a beta-tester.
Basic locations I had in mind:
Seats are in front of the canard wing. The fuel and baggage is stored between the canard and main wing. The engine nacelles are more forward than in the Long-Ez derivatives. They protrude from the main wing forward in a similar manner like they would be additional fuselages in midwing configuration. The engine nacelles are not necessarily fat enough to look realistic, but they hopefully deliver the basic idea, as this is not a final drawing but a computerized sketch of the configuration layout. The two horizontal stabilizers are in the propeller stream because that way they are more effective than winglet mounted rudders would be on a canard aircraft, and instead of becoming effective at relatively high speed, these can be made to be effective from almost zero speed, similarly than conventionally configured aircraft.
The idea is influenced by this:
http://www.scaled.com/projects/proteus_specifications.pdf
Here is another mix of the catdroid song. This has some elements changed and some extended. I am particularly happy with the intro section now. It has some ambient elements which fit with each other surprisingly well.
Enjoy!
Comments are welcome also, please give your opinion, which version you like the best.
Canard configuration is usually quite problematic and it has several compromises which decrease the benefits that could be otherwise obtained from the configuration. However, there is one advantage on canard configuration which is better than traditional configuration: stall and spin resistance. If the major design goal is stall and spin resistance, the penalties from the canard configuration can be assumed acceptable. After all very many aircraft accidents are caused by stall/spin.
So how to do a twin engine propeller canard so that the engine pods can be utilized also to other use?
So the idea goes:
1. take a look at Burt Rutan’s Proteus.
2. see the booms for the horizontal stabilizers.
3. Instead of placing jet engines to the fuselage, why not put tractor propellers to the front of the booms.
3. The CG on canard aircraft is between the two wings, the long fuselage solves the problem where to place the fuel in
a canard AC, it can be stored between the wings inside the fuselage.
Any comments/arguments why this would not be a good idea in your opinion?
Eggenfellner seems to be building a new aircraft type:
http://www.eggenfellneraircraft.com/E2B.htm
Interesting design choice – flying wing, no tail. Sounds like no flaps on this machine for increasing Clmax.
Eggenfellner seems to be building a new aircraft type:
http://www.eggenfellneraircraft.com/E2B.htm
Interesting design choice – flying wing, no tail. Sounds like no flaps on this machine for increasing Clmax.
Eggenfellner seems to be building a new aircraft type:
http://www.eggenfellneraircraft.com/E2B.htm
Interesting design choice – flying wing, no tail. Sounds like no flaps on this machine for increasing Clmax.
Eggenfellner seems to be building a new aircraft type:
http://www.eggenfellneraircraft.com/E2B.htm
Interesting design choice – flying wing, no tail. Sounds like no flaps on this machine for increasing Clmax.
Eggenfellner seems to be building a new aircraft type:
http://www.eggenfellneraircraft.com/E2B.htm
Interesting design choice – flying wing, no tail. Sounds like no flaps on this machine for increasing Clmax.
Eggenfellner seems to be building a new aircraft type:
http://www.eggenfellneraircraft.com/E2B.htm
Interesting design choice – flying wing, no tail. Sounds like no flaps on this machine for increasing Clmax.
Eggenfellner seems to be building a new aircraft type:
http://www.eggenfellneraircraft.com/E2B.htm
Interesting design choice – flying wing, no tail. Sounds like no flaps on this machine for increasing Clmax.
It seems that Wikipedia explains drag coefficient quite well. Here are two articles:
http://en.wikipedia.org/wiki/Drag_coefficient
http://en.wikipedia.org/wiki/Drag_equation
Here are NASA’s study materials about drag:
http://www.grc.nasa.gov/WWW/K-12/airplane/drageq.html
In Ubuntu hardy:
Host kernel mmap_min addr value is incompatible with the QEMU version used in scratchbox.
Quick help:
$ sudo su
$ nano /etc/sysctl.conf
edit line which begins ‘vm.mmap_min_addr’ (search it with CTRL-W) to
‘vm.mmap_min_addr = 4096′
CTRL-X for save & quit
$ sysctl -p
Quick help:
$ sudo su
$ nano /etc/sysctl.conf
Add line ‘vm.vdso_enabled = 0′ to the end of file.
Press ctrl-x to exit and save.
Then run ’sysctl -p’ (while remaining as root)
I was changing the parameters in the DesignFoil demo. And got interesting positive change for the NLF-115 airfoil: increasing the thickness to 20%, it does not effect the laminar bucket low Cl area, but it increases the laminar bucket towards higher Cl area. On other airfoils, this change usually moves the low drag bucket upwards to higher Cl, but on this airfoil, the low drag bucket seems to rather extend than move. I was trying it out with Reynolds numbers 2000000, 3000000 and 5000000.
The higher thickness (if the simulation is at all correct) would be favorable for structural reasons. The Burt Rutan’s canards also use thick airfoils in the canard wing, the thickness of the original GU25 is 20%. I don’t know the exact thickness of Roncz R1145MS and haven’t measured (I have the Cozy MKIV plans which have the Roncz airfoil included, so I could measure it if I had time to look at it).
The larger thickness contributes to the strength achieved (only those little glass fiber spar caps are needed instead of very heavy big wing spar or alternatively a wing spar made of carbon fiber).
Here is another mix of the Catdroid. It is now a bit longer and the strings are removed from part A when it plays the first time (This is BABABABB).
Enjoy!
Kate Alhola’s and Antonio Aloisio’s presentation on Akademy 2008 about how to develop Qt Application on Maemo.
Developing Maemo Qt Applications from Karoliina Salminen on Vimeo.
Equipment and software used: Apple iMac, Logic Studio, Novation V-synth, Soundtrack Pro, M-audio Axiom 25 as master keyboard. Track utilizes, as usual, my favorites: Tape delay and Space Designer effects.
The Fairlight samples in the beginning were from Internet, all other sounds are from either Novation or from one of the software synthesizers in the Logic Studio.
Here is alternative version of the song (with heavier compression, which makes it louder):
Here is a link to couple of aerodynamics articles:
http://adg.stanford.edu/aa241/airfoils/
I have been trying out about all demo versions available of airfoil programs. Best of them so far has been Xfoil and the Javafoil. However, neither seems to accurately simulate the laminar bucket.
I was surprised to try the Designfoil from Dreesecode: it simulates the laminar bucket, and the demo version also run on Ubuntu Hardy Linux with wine. Excellent, the first windows aircraft software that actually runs on Linux so far.
The studio gear nowadays fits to a very small space. This setup has Kate’s Macbook, M-audio Axiom keyboard (which is USB powered) and the Mac runs Apple Logic Studio and also Novation V-Synth. At home I am using iMac.
I no longer use the Wavestation or Roland D70 as a sound source very frequently, I rather use them as keyboard controllers. The Access Virus b I have is still quite useful instrument (although the Access Virus Snow costs the same as new now than the b-model costed used when we purchased it). Same applies for the Nord Modular (which I purchased from Fin (Christian Worton)). I have the Fin’s patches still on it. I don’t have the official editor for it for any of my operating systems though, but that is no problem, someone has done a open source editor for the NM and it works great on Mac and Linux. I don’t usually have that much time to tinker with the sounds since I have so wide selection (many thousands) of presets available that I would be stupid to not use some of them – maybe edit a bit to suit my needs, but why to reinvent the wheel if someone has invented it already, I rather concentrate on making music nowadays.
I really love the Logic Studio, it is propably my best software purchase I have ever made to the date. Excellent software with excellent add-ons. Everything is top-notch and as Apple products in usual, everything is also very nice… I would highly recommend Logic Studio if you are serious about producing music. I have tried demo-version of Abbleton Live and, tried Sonar longer time ago etc., but none of them are like the Logic. And now, when the Logic is an Apple product, the user interface has gone through some renewal, it is no longer like it used to be on PC “press middle button of the mouse on top of nowhere and use your nose to push CTRL at the same time while pressing some magic keys with your left hand”. Now all the features are available for ordinary mortals like me.
So how I like the Axiom? I read some praising reviews and some reviews where the reviewer totally disliked the keyboard. Based on my experience on different synth action -type keyboards (Korg, Roland, Nord etc.), the M-Audio Axiom is not at all a bad one. Actually it has propably the best feel of all keyboards I have. It only has 2 octaves on it, but for portability’s sake, it is an acceptable compromise. I really like it. It is semi-weighted and it seems that some people don’t like semi-weighted keyboards, but I like it very much and I can play very accurately with it. The Nord Modular’s keyboard someone said to be good is quite crappy toy compared to this one, the Korg has sticky black keys, the Roland has pretty elegant action, but this one can be really used for serious playing and the semi-weighted feel is in my opinion great. The build quality is good and the price-value ratio is excellent. It does not have a metal case, but who cares, I don’t want any steel case for something I am going to put in a backbag, this already weights quite a bit when combined with the Mac, but the studio is now movable, and usable – instead of studio being lots of gear disconnected in a storage room, this thing works and producing music is fun an easy – no cables, just one USB-cable and the headphone cable.
The studio gear nowadays fits to a very small space. This setup has Kate’s Macbook, M-audio Axiom keyboard (which is USB powered) and the Mac runs Apple Logic Studio and also Novation V-Synth. At home I am using iMac.
I no longer use the Wavestation or Roland D70 as a sound source very frequently, I rather use them as keyboard controllers. The Access Virus b I have is still quite useful instrument (although the Access Virus Snow costs the same as new now than the b-model costed used when we purchased it). Same applies for the Nord Modular (which I purchased from Fin (Christian Worton)). I have the Fin’s patches still on it. I don’t have the official editor for it for any of my operating systems though, but that is no problem, someone has done a open source editor for the NM and it works great on Mac and Linux. I don’t usually have that much time to tinker with the sounds since I have so wide selection (many thousands) of presets available that I would be stupid to not use some of them – maybe edit a bit to suit my needs, but why to reinvent the wheel if someone has invented it already, I rather concentrate on making music nowadays.
I really love the Logic Studio, it is propably my best software purchase I have ever made to the date. Excellent software with excellent add-ons. Everything is top-notch and as Apple products in usual, everything is also very nice… I would highly recommend Logic Studio if you are serious about producing music. I have tried demo-version of Abbleton Live and, tried Sonar longer time ago etc., but none of them are like the Logic. And now, when the Logic is an Apple product, the user interface has gone through some renewal, it is no longer like it used to be on PC “press middle button of the mouse on top of nowhere and use your nose to push CTRL at the same time while pressing some magic keys with your left hand”. Now all the features are available for ordinary mortals like me.
So how I like the Axiom? I read some praising reviews and some reviews where the reviewer totally disliked the keyboard. Based on my experience on different synth action -type keyboards (Korg, Roland, Nord etc.), the M-Audio Axiom is not at all a bad one. Actually it has propably the best feel of all keyboards I have. It only has 2 octaves on it, but for portability’s sake, it is an acceptable compromise. I really like it. It is semi-weighted and it seems that some people don’t like semi-weighted keyboards, but I like it very much and I can play very accurately with it. The Nord Modular’s keyboard someone said to be good is quite crappy toy compared to this one, the Korg has sticky black keys, the Roland has pretty elegant action, but this one can be really used for serious playing and the semi-weighted feel is in my opinion great. The build quality is good and the price-value ratio is excellent. It does not have a metal case, but who cares, I don’t want any steel case for something I am going to put in a backbag, this already weights quite a bit when combined with the Mac, but the studio is now movable, and usable – instead of studio being lots of gear disconnected in a storage room, this thing works and producing music is fun an easy – no cables, just one USB-cable and the headphone cable.
The studio gear nowadays fits to a very small space. This setup has Kate’s Macbook, M-audio Axiom keyboard (which is USB powered) and the Mac runs Apple Logic Studio and also Novation V-Synth. At home I am using iMac.
I no longer use the Wavestation or Roland D70 as a sound source very frequently, I rather use them as keyboard controllers. The Access Virus b I have is still quite useful instrument (although the Access Virus Snow costs the same as new now than the b-model costed used when we purchased it). Same applies for the Nord Modular (which I purchased from Fin (Christian Worton)). I have the Fin’s patches still on it. I don’t have the official editor for it for any of my operating systems though, but that is no problem, someone has done a open source editor for the NM and it works great on Mac and Linux. I don’t usually have that much time to tinker with the sounds since I have so wide selection (many thousands) of presets available that I would be stupid to not use some of them – maybe edit a bit to suit my needs, but why to reinvent the wheel if someone has invented it already, I rather concentrate on making music nowadays.
I really love the Logic Studio, it is propably my best software purchase I have ever made to the date. Excellent software with excellent add-ons. Everything is top-notch and as Apple products in usual, everything is also very nice… I would highly recommend Logic Studio if you are serious about producing music. I have tried demo-version of Abbleton Live and, tried Sonar longer time ago etc., but none of them are like the Logic. And now, when the Logic is an Apple product, the user interface has gone through some renewal, it is no longer like it used to be on PC “press middle button of the mouse on top of nowhere and use your nose to push CTRL at the same time while pressing some magic keys with your left hand”. Now all the features are available for ordinary mortals like me.
So how I like the Axiom? I read some praising reviews and some reviews where the reviewer totally disliked the keyboard. Based on my experience on different synth action -type keyboards (Korg, Roland, Nord etc.), the M-Audio Axiom is not at all a bad one. Actually it has propably the best feel of all keyboards I have. It only has 2 octaves on it, but for portability’s sake, it is an acceptable compromise. I really like it. It is semi-weighted and it seems that some people don’t like semi-weighted keyboards, but I like it very much and I can play very accurately with it. The Nord Modular’s keyboard someone said to be good is quite crappy toy compared to this one, the Korg has sticky black keys, the Roland has pretty elegant action, but this one can be really used for serious playing and the semi-weighted feel is in my opinion great. The build quality is good and the price-value ratio is excellent. It does not have a metal case, but who cares, I don’t want any steel case for something I am going to put in a backbag, this already weights quite a bit when combined with the Mac, but the studio is now movable, and usable – instead of studio being lots of gear disconnected in a storage room, this thing works and producing music is fun an easy – no cables, just one USB-cable and the headphone cable.
The studio gear nowadays fits to a very small space. This setup has Kate’s Macbook, M-audio Axiom keyboard (which is USB powered) and the Mac runs Apple Logic Studio and also Novation V-Synth. At home I am using iMac.
I no longer use the Wavestation or Roland D70 as a sound source very frequently, I rather use them as keyboard controllers. The Access Virus b I have is still quite useful instrument (although the Access Virus Snow costs the same as new now than the b-model costed used when we purchased it). Same applies for the Nord Modular (which I purchased from Fin (Christian Worton)). I have the Fin’s patches still on it. I don’t have the official editor for it for any of my operating systems though, but that is no problem, someone has done a open source editor for the NM and it works great on Mac and Linux. I don’t usually have that much time to tinker with the sounds since I have so wide selection (many thousands) of presets available that I would be stupid to not use some of them – maybe edit a bit to suit my needs, but why to reinvent the wheel if someone has invented it already, I rather concentrate on making music nowadays.
I really love the Logic Studio, it is propably my best software purchase I have ever made to the date. Excellent software with excellent add-ons. Everything is top-notch and as Apple products in usual, everything is also very nice… I would highly recommend Logic Studio if you are serious about producing music. I have tried demo-version of Abbleton Live and, tried Sonar longer time ago etc., but none of them are like the Logic. And now, when the Logic is an Apple product, the user interface has gone through some renewal, it is no longer like it used to be on PC “press middle button of the mouse on top of nowhere and use your nose to push CTRL at the same time while pressing some magic keys with your left hand”. Now all the features are available for ordinary mortals like me.
So how I like the Axiom? I read some praising reviews and some reviews where the reviewer totally disliked the keyboard. Based on my experience on different synth action -type keyboards (Korg, Roland, Nord etc.), the M-Audio Axiom is not at all a bad one. Actually it has propably the best feel of all keyboards I have. It only has 2 octaves on it, but for portability’s sake, it is an acceptable compromise. I really like it. It is semi-weighted and it seems that some people don’t like semi-weighted keyboards, but I like it very much and I can play very accurately with it. The Nord Modular’s keyboard someone said to be good is quite crappy toy compared to this one, the Korg has sticky black keys, the Roland has pretty elegant action, but this one can be really used for serious playing and the semi-weighted feel is in my opinion great. The build quality is good and the price-value ratio is excellent. It does not have a metal case, but who cares, I don’t want any steel case for something I am going to put in a backbag, this already weights quite a bit when combined with the Mac, but the studio is now movable, and usable – instead of studio being lots of gear disconnected in a storage room, this thing works and producing music is fun an easy – no cables, just one USB-cable and the headphone cable.
The studio gear nowadays fits to a very small space. This setup has Kate’s Macbook, M-audio Axiom keyboard (which is USB powered) and the Mac runs Apple Logic Studio and also Novation V-Synth. At home I am using iMac.
I no longer use the Wavestation or Roland D70 as a sound source very frequently, I rather use them as keyboard controllers. The Access Virus b I have is still quite useful instrument (although the Access Virus Snow costs the same as new now than the b-model costed used when we purchased it). Same applies for the Nord Modular (which I purchased from Fin (Christian Worton)). I have the Fin’s patches still on it. I don’t have the official editor for it for any of my operating systems though, but that is no problem, someone has done a open source editor for the NM and it works great on Mac and Linux. I don’t usually have that much time to tinker with the sounds since I have so wide selection (many thousands) of presets available that I would be stupid to not use some of them – maybe edit a bit to suit my needs, but why to reinvent the wheel if someone has invented it already, I rather concentrate on making music nowadays.
I really love the Logic Studio, it is propably my best software purchase I have ever made to the date. Excellent software with excellent add-ons. Everything is top-notch and as Apple products in usual, everything is also very nice… I would highly recommend Logic Studio if you are serious about producing music. I have tried demo-version of Abbleton Live and, tried Sonar longer time ago etc., but none of them are like the Logic. And now, when the Logic is an Apple product, the user interface has gone through some renewal, it is no longer like it used to be on PC “press middle button of the mouse on top of nowhere and use your nose to push CTRL at the same time while pressing some magic keys with your left hand”. Now all the features are available for ordinary mortals like me.
So how I like the Axiom? I read some praising reviews and some reviews where the reviewer totally disliked the keyboard. Based on my experience on different synth action -type keyboards (Korg, Roland, Nord etc.), the M-Audio Axiom is not at all a bad one. Actually it has propably the best feel of all keyboards I have. It only has 2 octaves on it, but for portability’s sake, it is an acceptable compromise. I really like it. It is semi-weighted and it seems that some people don’t like semi-weighted keyboards, but I like it very much and I can play very accurately with it. The Nord Modular’s keyboard someone said to be good is quite crappy toy compared to this one, the Korg has sticky black keys, the Roland has pretty elegant action, but this one can be really used for serious playing and the semi-weighted feel is in my opinion great. The build quality is good and the price-value ratio is excellent. It does not have a metal case, but who cares, I don’t want any steel case for something I am going to put in a backbag, this already weights quite a bit when combined with the Mac, but the studio is now movable, and usable – instead of studio being lots of gear disconnected in a storage room, this thing works and producing music is fun an easy – no cables, just one USB-cable and the headphone cable.
The studio gear nowadays fits to a very small space. This setup has Kate’s Macbook, M-audio Axiom keyboard (which is USB powered) and the Mac runs Apple Logic Studio and also Novation V-Synth. At home I am using iMac.
I no longer use the Wavestation or Roland D70 as a sound source very frequently, I rather use them as keyboard controllers. The Access Virus b I have is still quite useful instrument (although the Access Virus Snow costs the same as new now than the b-model costed used when we purchased it). Same applies for the Nord Modular (which I purchased from Fin (Christian Worton)). I have the Fin’s patches still on it. I don’t have the official editor for it for any of my operating systems though, but that is no problem, someone has done a open source editor for the NM and it works great on Mac and Linux. I don’t usually have that much time to tinker with the sounds since I have so wide selection (many thousands) of presets available that I would be stupid to not use some of them – maybe edit a bit to suit my needs, but why to reinvent the wheel if someone has invented it already, I rather concentrate on making music nowadays.
I really love the Logic Studio, it is propably my best software purchase I have ever made to the date. Excellent software with excellent add-ons. Everything is top-notch and as Apple products in usual, everything is also very nice… I would highly recommend Logic Studio if you are serious about producing music. I have tried demo-version of Abbleton Live and, tried Sonar longer time ago etc., but none of them are like the Logic. And now, when the Logic is an Apple product, the user interface has gone through some renewal, it is no longer like it used to be on PC “press middle button of the mouse on top of nowhere and use your nose to push CTRL at the same time while pressing some magic keys with your left hand”. Now all the features are available for ordinary mortals like me.
So how I like the Axiom? I read some praising reviews and some reviews where the reviewer totally disliked the keyboard. Based on my experience on different synth action -type keyboards (Korg, Roland, Nord etc.), the M-Audio Axiom is not at all a bad one. Actually it has propably the best feel of all keyboards I have. It only has 2 octaves on it, but for portability’s sake, it is an acceptable compromise. I really like it. It is semi-weighted and it seems that some people don’t like semi-weighted keyboards, but I like it very much and I can play very accurately with it. The Nord Modular’s keyboard someone said to be good is quite crappy toy compared to this one, the Korg has sticky black keys, the Roland has pretty elegant action, but this one can be really used for serious playing and the semi-weighted feel is in my opinion great. The build quality is good and the price-value ratio is excellent. It does not have a metal case, but who cares, I don’t want any steel case for something I am going to put in a backbag, this already weights quite a bit when combined with the Mac, but the studio is now movable, and usable – instead of studio being lots of gear disconnected in a storage room, this thing works and producing music is fun an easy – no cables, just one USB-cable and the headphone cable.
The studio gear nowadays fits to a very small space. This setup has Kate’s Macbook, M-audio Axiom keyboard (which is USB powered) and the Mac runs Apple Logic Studio and also Novation V-Synth. At home I am using iMac.
I no longer use the Wavestation or Roland D70 as a sound source very frequently, I rather use them as keyboard controllers. The Access Virus b I have is still quite useful instrument (although the Access Virus Snow costs the same as new now than the b-model costed used when we purchased it). Same applies for the Nord Modular (which I purchased from Fin (Christian Worton)). I have the Fin’s patches still on it. I don’t have the official editor for it for any of my operating systems though, but that is no problem, someone has done a open source editor for the NM and it works great on Mac and Linux. I don’t usually have that much time to tinker with the sounds since I have so wide selection (many thousands) of presets available that I would be stupid to not use some of them – maybe edit a bit to suit my needs, but why to reinvent the wheel if someone has invented it already, I rather concentrate on making music nowadays.
I really love the Logic Studio, it is propably my best software purchase I have ever made to the date. Excellent software with excellent add-ons. Everything is top-notch and as Apple products in usual, everything is also very nice… I would highly recommend Logic Studio if you are serious about producing music. I have tried demo-version of Abbleton Live and, tried Sonar longer time ago etc., but none of them are like the Logic. And now, when the Logic is an Apple product, the user interface has gone through some renewal, it is no longer like it used to be on PC “press middle button of the mouse on top of nowhere and use your nose to push CTRL at the same time while pressing some magic keys with your left hand”. Now all the features are available for ordinary mortals like me.
So how I like the Axiom? I read some praising reviews and some reviews where the reviewer totally disliked the keyboard. Based on my experience on different synth action -type keyboards (Korg, Roland, Nord etc.), the M-Audio Axiom is not at all a bad one. Actually it has propably the best feel of all keyboards I have. It only has 2 octaves on it, but for portability’s sake, it is an acceptable compromise. I really like it. It is semi-weighted and it seems that some people don’t like semi-weighted keyboards, but I like it very much and I can play very accurately with it. The Nord Modular’s keyboard someone said to be good is quite crappy toy compared to this one, the Korg has sticky black keys, the Roland has pretty elegant action, but this one can be really used for serious playing and the semi-weighted feel is in my opinion great. The build quality is good and the price-value ratio is excellent. It does not have a metal case, but who cares, I don’t want any steel case for something I am going to put in a backbag, this already weights quite a bit when combined with the Mac, but the studio is now movable, and usable – instead of studio being lots of gear disconnected in a storage room, this thing works and producing music is fun an easy – no cables, just one USB-cable and the headphone cable.
I was flying today (as a passanger) to Brussels and I wasn’t doing nothing, I had paper, pen and the HP calculator with me. And of course J.D. Anderson’s Aircraft performance & design as a reference.
So I ended up with some numbers, but I know already that they are a bit off – since I calculated AR the other way around and got with the K and e I used AR = 10 even if I had chosen that the AR = 14. Therefore the climb performance may be even quite pessimistic. Besides of that I was reading yet another aerodynamics book which stated that e is as high as 0.9 for clean airplane.
However, numbers are: Trimaran configuration, 2 x HKS 700 turbo, 2 places, fuel 200 liters, S = 99 ft^2, MTOW 1980 lbs (maybe 900 kg would still be within limits, haven’t checked), AR = 14. Slotted flaps and flapped ailerons. Taper 0.5. Low drag laminar airfoil and 60% laminar fuselage shape and the plane will be quite fast. RG is assumed, gear stored in the pusher prop engine pods.
Some information about the new 80 hp turbocharged fuel injected HKS 700 can be found from here:
Tecnam is considering this engine, and it looks very interesting – it is lightweight and runs on diesel. The power output is similar to Rotax 912 and for the turbocharged version (125 hp) even better than any Rotax can do:
Here is the equation for calculating the estimated maximum speed of the aircraft concept:
Estimating e seems to not be so trivial and causes lots of thinking – it does not seem to be directly applicable by the book:
Daniel Raymer says in his book that e (Oswald’s efficiency factor) is normally between 0.7 and 0.85 (the e that is below 1.0 comes from the deviation from the perfect elliptic lift distribution). Jon Anderson Jr. says on his book Aircraft Performance & Design that on general aviation aircraft, the e is normally 0.6. And in one example aircraft design in the book Anderson then goes and uses e that is 0.9. It has quite large impact on the estimation results, so it would be better to estimate it right.
Then there are multiple equations for estimating e, in Raymer’s and Anderson’s books. All produce different results, and as a result, the K will be different. And the K has effect on L/Dmax. Interesting enough – the L/Dmax, if the e is estimated with any of the equations provided or assumed as 0.6 as Anderson recommends, the Diamond DA42 Twin Star should have L/D ratio around 12 instead of 18 it in reality has. It has been said that these estimation equations apply only to “normal” aspect ratios. It would be interesting to know what is “normal” aspect ratio – DA42 has AR=12 and the LH10 has AR=14. Maybe that is “higher than normal” then and maybe I have had the privilege to fly “not so normal airplane” when flying the Twin Star. Normal or abnormal, it is an excellent aircraft which is very much fun to fly.
So if I am estimating the L/Dmax of aircraft that has AR=14, and has tapered wing, it seems that quite high e value needs to be picked up. The estimation equation is a heavy generalization though, it does not take into account that on which CL the low drag laminar bucked is (it rather seems that the equations assume turbulent flow).
Credits: Karoliina Salminen
Equipment used: Apple Logic Studio, Apple Garage Band, Access Virus b
Please notice that the link was changed from karoliinasalminen.com to katix.org since karoliinasalminen.com has been temporarily down.
Credits: Karoliina Salminen
Equipment used: Apple Logic Studio (no hardware synthesizers except for Nord Modular as midi keyboard)
I am on sick leave and typing this from bed, I have two laptops in the bed right now, my work Linux laptop and Kate’s Mac.. I have inner ear inflammation which makes me feel really dizzy if I get up from the bed, so I stay down as much as possible…
I was delighted to notice that there is a MacOSX version of Rhino3D coming. My workmate uses Rhino professionally and he told me about that. I of course straight away went ahead and wanted to become a beta tester. And I got approved as beta tester subsequently. Wow.
Rhino is really interesting piece of software. It took about 30 minutes and I had a NACA 66-018 low drag body modeled.
1. Download the latest nVidia driver from nVidia site. The driver should be 32 bit Linux (assuming you are running 32-bit version and not the AMD-64 -version), Quadro FX570M if you are running IBM T61p laptop. Otherwise (on other machines) select the appropriate display controller from the menu. Save the file to a location that you can easily access when you are in text mode (mandatory step).
2. Boot the Ubuntu (mandatory).
When the password dialog appears, press CTRL+ALT+F1
When text mode appears and asks for login, log in with your username and password.
3. Become root (mandatory):
sudo su
and then give your password
4. Stop the gdm (replace with kdm if you are running Kubuntu or kdm-kde4 if you are running Kubuntu-KDE4 remix)
/etc/init.d/gdm stop
5. If you don’t have compilation environment, you can install it by (optional):
apt-get update
apt-get install gcc g++ glibc
6. Uninstall now the nvidia open source driver (mandatory):
dpkg –purge xserver-xorg-video-all xserver-xorg-video-nvidia
Now you have no display driver installed on your system at all, you can’t start X.
Go to the directory where you have the nVidia driver package located.
It is named something like NVIDIA-something.run.
TYPE (mandatory):
chmod +x NVIDIA*.run
Now execute the package (mandatory):
./NVIDIA…..run (replace …. with the correct filename which depends on which driver version you have).
Accept license agreement.
Answer to the question if the installer wants to download precompiled kernel module from nVidia site that “No”.
It may state that you have already a nVidia driver installed and if you want to uninstall the driver first. Answer yes to that kind of question.
The installer asks also if you want to modify the xorg.conf for the driver. Answer yes to that kind of question.
Your new driver is now successfully installed if you didn’t receive any errors in the process.
You can now restart the gdm to log in the system without rebooting:
/etc/init.d/gdm restart
If you are using external display in addition to the laptop screen, you may need to reboot to get it functioning correctly. You need to have both the external display and laptop display turned on when you boot the computer for the nVidia driver to autoconfigure it properly.
If your display settings still aren’t correct, you can edit them with nvidia-settings (optional):
Open terminal window
sudo nvidia-settings
Change the settings to appropriate and save to xorg.conf. Please note that you may need to run the nvidia-settings from terminal window instead of clicking the icon or menu item which launches nvidia-settings because in order to write to the xorg.conf you need to be root and Ubuntu wasn’t designed to support the nVidia settings application as it has its own (but sometimes not working) installers for binary drivers (the envy package which may work for some, but at least didn’t work for me with IBM T61p and Hardy).
Everything might look very obvious at first, but after digging more and more, it becomes clearer and clearer what kind of compromises all aircraft are made of and why.
A known thing is that the more efficient the airfoil the higher L/D ratio it has and vice versa. So one could go and find that sailplane airfoils produce very high L/D ratios. There is a little but on that though: Sailplane airfoils commonly achieve the best L/D ratio at higher Cl than what is optimal for a powered aircraft with reasonable wing loading where the cruise Cl is between 0.15 and 0.20. E.g. NLF 215F seems to achieve its L/D max at around Cl 0.5 which is unusually low compared to some other airfoils that require Cl being close to 1.0. That is acceptable for a sailplane that is thermalling at close to the stall speed. However, that is not where one wants to cruise with a powered aircraft, there is usually a requirement to get somewhere in a reasonable time, thus speed has some importance.
I have previously mentioned that the wing loading and cruise Cl has direct relation. The higher the wing loading, the higher the cruise Cl vice versa. Then the speed where the best L/D ratio occurs has a relation to the previous and it also tends to have relation to the top speed.
Diamond DA40 uses Wortmann FX 63-137 airfoil. It has best L/D ratio higher than the optimal < 0.2 (for light wing loading). Therefore the best L/D speed is the same as the approach speed on the aircraft. Similarly on Diamond DA42 Twin Star the same airfoil was used but the wing loading is as high as it is on Cirrus SR20. The result is that the best L/D speed is higher than on DA40, the top speed is higher (it is not only because of the two engines, the two engines produce also more drag than one). Because of the substantially heavier wing loading, the DA42 cruises at higher Cl than the DA40 and it gets closer to the airfoil optimum resulting better aerodynamic efficiency.
Cirrus SR20 is very similar to the DA40 but it has a different airfoil and higher wing loading. That results best L/D ratio speed being 96 kts. SR22 has that value even higher, it is over 100 kts, but it can be misleading that the best glide speed mentioned in the operating handbook is lower than on SR20. That is the best glide speed, it is not the best L/D ratio speed of the airfoil, it is a compromise of the airfoil + fuselage + propeller and in the SR22 the propeller is braking a lot more than on SR20, which alone is enough to explain the lower best glide speed – because of the propeller braking, the SR22 sinks faster, but if there was no propeller, SR22 could have higher glide speed than the SR20. But what this has to do with the topic? The interesting thing is that the Cirrus has different airfoil and higher wing loading and the optimum glide speed is higher than on DA40 which results potential to faster cruise speed than DA40 (whereas it is not exactly the airfoil’s best L/D speed because of the mentioned reasons). Providing that there is enough power available, the Cirrus airframe is faster although the larger fuselage cross section and wetted area most likely pretty much diminishes the benefit from the wing, that is also partly a reason why the best cruise speed performance of DA40-180/XL and SR20 is not that much different, SR20 is just slightly faster – the Diamond has better fuselage shape and it simply is a lot smaller aircraft than the Cirrus and size does not tend to come without penalty when it comes to aerodynamic drag.
However, it would be beneficial for efficiency to have an airfoil which could achieve higher L/D ratio at the cruise Cl of the DA40 already. It does not come without penalties of course, the airfoils which have high L/D ratio at low Cl don’t necessarily always produce optimal Clmax (which then has also relation to the required wing area which gets back to the stall speed and wing loading).
And it is not all in that, Daniel Raymer notes in his book that usually only 90% of the theoretical Clmax of the airfoil gets realized in practice. Therefore it is a interesting compromise between the wing sizing, and the best L/D at cruise Cl. Daniel Raymer notes in high book that the Cl is one of the hardest things to estimate without experimental data from test flights, and often test flights result in the need of modifications (e.g. if the Clmax in practise is not as good as was predicted, a larger wing is required to meet the maximum stall speed criteria, which is for single engine aircraft 61 kts).
It would be really interesting if someone would have a batch processing functionality in a airfoil program that would ingest the UIUC airfoil database data and simulate through all airfoils and put them into a correct order for the given specification (cruise Cl below 0.2), as high L/D at cruise Cl for a low wing loading, and at the same time, as high Clmax as possible, and at the same time, gentle stall charasteristics at low Reynolds number. And of course, the pitching moment also has some importance, high pitching moment tends to cause more trim drag which reduces the achievable Clmax (of the total airframe) considerably – if the wing can achieve e.g. Clmax 2.2, the airframe may be left to below 1.5 in total because of the download in the tail that is negative lift.
Hobby wireless – a shop where you can buy FPV stuff
Youtube video about FPV in operation:
Martin Hollman’s book seems to describe structural calculations of wing in a pretty understandable way. Even I can follow how the resulting equation comes from the integration. I may write some software for spar sizing and layup schedule later after I get the aerodynamics part good enough to be useful. Martin Hollman’s book includes Basic language programs for spar sizing etc., but they are not that easy to convert into modern programming languages because they are full of gotos and gosubs and global variables used in a crazy manner (the traditional Basic-spaghetti way). So it seems to be easier to understand the equations first and create the calculation algorithm from scratch by myself.
However, it would be interesting to know how much weight penalty comes from high aspect ratio. I am particularly interested in AR higher than 10 where around 14 would be great, because I am interested in high flight efficiency. However, my structural needs would be for a lot higher speeds than used on gliders, so it would be interesting to know how feasible it is to achieve a structure for AR=14 that can have Va >= 200 mph without adverse effects e.g. like aileron reversal and flutter.
I got type check out for Diamond DA40D yesterday and I wrote an article about it. I was very pleased with the handling qualities of the aircraft, it has the most well defined control feel than any other plane I have ever flown to the date. If you understand Finnish, you can read the full article from here http://lentokone.blogspot.com/2008/06/kokeiltua-diamond-da40d.html.
(Kuvassa OH-FDA, OH-DDS:n edeltäjä)
PIK:ille tuli OH-FDA:lle korvaaja ja vihdoin pääsin tyypittämään myös Diamondin DA40:sen. Olen kerinnyt lentää Cirruksilla (SR20 ja SR22) ja Twin Starilla ennen DA40:stä, ja kiinnosti kovasti päästä kunnolla selvittämään minkälainen kone on lentää. Otinkin siihen sitten Tuukan kanssa tyypit.
Koneeseen kiipeäminen on kohtuullisen helppoa, helpompaa kuin useisiin ultriin. Ei kuitenkaan ehkä yhtä helppoa kuin ovella varustettuun Cirrukseen vaikkakin siiven päälle kiipeäminen lienee Diamondissa aavistuksen helpompaa, koska siipi on matalammalla ja askelma sopivalla paikalla siiven etupuolella. Näkymä ohjaamosta on erinomaista tasoa, selvästi parempi kuin kilpailijoista (Cessnan näkyvyyttä ei voi verrata edes samana päivänä ja Cirruksenkin Diamond pätkii näkyvyydessä melko suvereenisti etenkin näkyvyydessä etuviistoon sivulle missä Diamondilla näkökenttä jatkuu kuomusta johtuen selvästi alemmas kuin mitä henkilöautomaisen Cirruksen ohjaamosta näkee.
Koneessa on jarruohjaus eikä ohjattavaa nokkapyörää ole. Rullailu on suunnilleen yhtä helppoa kuin Cir
