What is "coffin corner"

Coffin corner may refer to:

• Coffin corner (aviation), an unstable combination of speed and altitude
• A position in a bomber formation combat box
• A strategy used in American football by a punter
• The Coffin Corner, a magazine published by the Professional Football Researchers Association

Coffin corner (also known as the aerodynamic ceiling or Q corner) is the altitude at or near which a fast fixed-wing aircraft's stall speed is equal to the critical Mach number, at a given gross weight and G-force loading. At this altitude it is very difficult to keep the airplane in stable flight. Because the stall speed is the minimum speed required to maintain level flight, any reduction in speed will cause the airplane to stall and lose altitude. Because the critical Mach number is the maximum speed at which air can travel over the wings without losing lift due to flow separation and shock waves, any increase in speed will cause the airplane to lose lift, or to pitch heavily nose-down, and lose altitude. The "corner" refers to the triangular shape at the top of a flight envelope chart where the stall speed and critical Mach number lines come together.