How many different airfoils will be tested on the Apex aircraft, and will the test section airfoil be the same as the rest of the wing?
The entire wing (including the test section) will use the Apex 16 airfoil designed by Mark Drela for initial flights from the balloon. This airfoil has been optimized for the flight conditions of the transition maneuver from vertical to horizontal flight (M = 0.65, Re = 300k). It also has robust, yet benign characteristics over the entire flight envelope. The inevitable upper surface separation at high subsonic Mach numbers affects the lift and drag gradually, not suddenly. After the performance of the Apex 16 has been measured and documented, other candidate airfoils could be evaluated in a similar manner. No candidate airfoils have been identified at this time.
