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Coffin corner
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Coffin corner is a term used in three different fields architecture, aircraft operation and sports, primarily American football and Canadian football.
Contents
1 Architecture
2 Football
3 Aircraft operation
3.1 Mach Limit
3.2 Stall Limit
3.3 The Corner
Aircraft operation
Coffin corner is a dangerous portion of the flight envelope that must be carefully approached by high altitude high subsonic speed aircraft, such as the Lockheed U-2 aircraft.
Mach Limit
A subsonic aircraft must not exceed its Mach limit, some fraction of the speed of sound near, but not at 1.0. At the low air densities and lower temperatures encountered at high altitude the speed of sound is lower. Exceeding the Mach limit can cause loss of control and/or structural failure.
Stall Limit
At high altitudes the low density air is less capable of supporting the aircraft and so the stall speed increases (as expressed in true air speed).
The Corner
At some limiting altitude these speeds converge, and the aircraft cannot be flown, as a slight pitch down will cause the Mach limit to be exceeded while a slight pitch up will cause an aircraft stall with a subsequent pitch down.
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