Description

Aerodynamic (low speed) stall at high altitude is sometimes referred to as a high incidence stall.

The term high incidence stall is used to differentiate a high altitude, low speed stall from a high altitude, Mach stall. The Mach stall occurs due to shock waves which form when the aircraft exceeds its critical Mach number. At high altitudes, the speeds at which the two types of stall occur become closer and closer culminating at a point on the Flight Envelope diagram referred to as coffin corner.