by someguy » Tue Mar 29, 2011 3:32 am
That's correct. The thinner air also cannot provide as much lift, thus the stall speed (in TAS) increases with altitude along with the pitot effect. However, as altitude increases, temperature decreases, which lowers the critical Mach speed, the speed at which the wing goes supersonic and loses its boundary flow. Every plane has an altitude where the stall and supersonic speeds coincide; it's called "coffin corner" because the plane can't go either faster or slower without losing lift dramatically and falling out of the sky. At that altitude, a turn could put one wing into stall and the other above critical Mach. Needless to say, most pilots of non-supersonic aircraft won't want to go there!