Flight envelope

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Two flight envelopes in the altitude-speed diagram. Green shows a fictional supersonic aircraft, black a subsonic aircraft

The flight envelope (engl. Flight envelope ) or flight range limit is the envelope of the possible performance of a missile in a height-velocity diagram, or multiples load-speed diagram. Sometimes these diagrams are also combined in one picture.

Flight envelopes indicate the permissible operating range of a missile. It is determined by a matrix of mutually influencing parameters, which in turn are only allowed to assume certain values. All conceivable combinations of speed, altitude, angle of attack , sideslip angle , weight, center of gravity and aircraft configuration (landing gear, flaps , slats , afterburner ) are examined in order to determine the limits of an aircraft when these variables change. The maneuverability, structural loading and behavior of the engines must remain within acceptable limits. Engines also have envelope curves for their permissible power range.

Direct comparisons of the performance of two aircraft can be drawn from flight envelopes . It also reveals where the aircraft's coffin corners are. If the aircraft is outside of the flight envelope, flight parameters take on unacceptable values, which can damage or even crash the aircraft.

The only criterion for determining the flight envelope is the safety of the aircraft, not its efficient operation. It is determined by extensive tests of hardware and software on the ground (e.g. in the wind tunnel) and in the air.

source

H. Walgemoed, Fokker Aircraft BV 1117 ZJ Schiphol-Oost THE NETHERLANDS Introduction to Flight Test Engineering , Chapter 12 - FLIGHT ENVELOPE RTO-AG-300-V14 ISBN 92-837-1126-2