Definition

In aerodynamics, the flight envelope, service envelope, or performance envelope of an aircraft refers to the capabilities of a design in terms of airspeed and load factor or altitude. The term is somewhat loosely applied, and can also refer to other measurements such as manoeuvrability. When an aeroplane is pushed, for instance by diving it at high speeds, to the point it exceeds a published limitation, it is said to be flown "outside the envelope", something considered rather dangerous and that could lead to structural damage or Loss of Control.

For further information, see Aerodynamic Stall Awareness and Avoidance.