Archive for the ‘ airspeed ’ Category

Airspeed at sea level

I got interesting airspeed calculator Excel-sheet from Petri Flander. I have been calculating those things with my aircraft design program and by hand before, but it is surprisingly handy to see the effect of various flat plate drag areas and their effect to the airspeed. Great input for my program which I am writing the UI for with Qt right now, I may do also graphical output for these parameters, would be fun to have. This was actually also useful to reverse-engineer the flat plate drag areas of various aircrafts. For example I came up with 4,7 ft2 for Cirrus SR20 where Lancair ES (=same as Columbia 400) is 4,0, so Cirrus is a slightly less efficient than the Columbia (which is evident also from the performance numbers comparing SR22 and Columbia 400). Interesting is that I came up with 9 for C152, which is a terribly bad figure. And Zenair CH701 produced a number around 18 which was reverse-engineered from real performance numbers I have heard from a Zenair pilot. Couldn’t get much worse than that. BD-5 has very low figure of 0,9 and Vmax probe is at 0,3 (these were obtained from elsewhere). A composite BD-5 with rear body laminar flow suction (with more laminar body shape as well) and some high tech airfoil like the NLF414F could be super-efficient. However, the issues with low Reynolds number from Vmax probe apply, it will have seriously dangerous stall charasteristics without modifications to the airfoil or wing.

>Airspeed at sea level

>I got interesting airspeed calculator Excel-sheet from Petri Flander. I have been calculating those things with my aircraft design program and by hand before, but it is surprisingly handy to see the effect of various flat plate drag areas and their effect to the airspeed. Great input for my program which I am writing the UI for with Qt right now, I may do also graphical output for these parameters, would be fun to have. This was actually also useful to reverse-engineer the flat plate drag areas of various aircrafts. For example I came up with 4,7 ft2 for Cirrus SR20 where Lancair ES (=same as Columbia 400) is 4,0, so Cirrus is a slightly less efficient than the Columbia (which is evident also from the performance numbers comparing SR22 and Columbia 400). Interesting is that I came up with 9 for C152, which is a terribly bad figure. And Zenair CH701 produced a number around 18 which was reverse-engineered from real performance numbers I have heard from a Zenair pilot. Couldn’t get much worse than that. BD-5 has very low figure of 0,9 and Vmax probe is at 0,3 (these were obtained from elsewhere). A composite BD-5 with rear body laminar flow suction (with more laminar body shape as well) and some high tech airfoil like the NLF414F could be super-efficient. However, the issues with low Reynolds number from Vmax probe apply, it will have seriously dangerous stall charasteristics without modifications to the airfoil or wing.

Here is a copy paste from the sheet with flat plate drag areas from 0.3 (Vmax probe) to 4 (Lancair ES):


Aircraft speed, km/h Prop eff 0,85 Dens.ratio 1,000 $

Drag area
ft2 25 40 60 80 85 90 100 <- Total hp (Rotax 914)
4 148 173 198 218 223 227 235 127,053 kts
3,00 163 191 218 240 245 250 259 139,840 kts
2,40 176 205 235 259 264 269 279 150,639037908943 kts
2,30 178 208 238 262 268 273 283 152,791314948939 kts
2,20 181 211 242 266 272 277 287 155,07211859505 kts
2,12 183 214 245 270 275 280 290 156,998677308782 kts
2,10 184 215 246 270 276 281 291 157,495511877874 kts
2,00 187 218 250 275 281 286 296 160,077864487362 kts
1,90 190 222 254 280 285 291 301 162,838370152973 kts
1,80 193 226 259 285 291 296 307 165,799714672936 kts
1,70 197 230 264 290 296 302 313 168,988949701208 kts
1,60 201 235 269 296 302 308 319 172,438652178898 kts
1,50 205 240 275 303 309 315 326 176,188487565227 kts
1,40 210 246 281 310 316 322 334 180,28735558483 kts
1,30 215 252 288 317 324 330 342 184,796395706893 kts
1,20 221 259 296 326 333 339 351 189,793294797389 kts
1,10 228 266 305 336 342 349 361 195,378626469698 kts
1,00 235 275 315 346 353 360 373 201,685471089846 kts
0,90 243 285 326 359 366 373 386 208,894550582996 kts
0,88 245 287 328 361 369 376 389 210,46524527855 kts
0,50 296 346 396 436 445 454 470 254,107770484061 kts
0,31 347 406 465 512 522 532 551 298,003054739616 kts