## High altitude flight Re, new airfoil KS415/14.3

The Reynolds number at very high altitude is very low. Here is an article about airfoil study for 60000 ft altitude flight. My previous airfoils are not very suitable in a small aircraft at 60000 ft, they require longer chord to be efficient. I made series of new airfoils for short chord and high altitude and ended up with the KS415/14.3.

Example:

altitude = 20000 m

velocity = 80 m/s

wing chord = 0.8 m (80 cm)

=>

Re = 396331.94

M = 0.2711

Therefore it is beneficial that the airfoil used in this kind of aircraft is such that provides maximum L/D at low Re, here around 400000.

Here are some simulations:

Then some airfoils that I created:

http://www.katix.org/karoliina/airfoils/KS414.dat

http://www.katix.org/karoliina/airfoils/KS415%2014.3.dat

http://www.katix.org/karoliina/airfoils/KS416%2014.20.dat

KS416:

More simulation at low Re, two conditions: 80 m/s at 600000 ft and 111 m/s (400 km/h) at 60000 ft:

Added case 154 m/2 (300 kts) at 60000 ft:

Of these, the KS415 exhibits the lowest drag. Here is the geometry of the KS415:

Here is a smoothed version of KS415/14.3:

http://www.katix.org/karoliina/airfoils/KS415_14_3sm.dat