Plain English Meaning
The speeds the airplane is meant to be flown at when doing maneuvers. Going too fast can overstress the airplane; going too slow can cause it to stall. Manufacturers publish these speeds so pilots stay inside safe limits while practicing.
Full Definition
The specific airspeeds published by the manufacturer for performing flight maneuvers safely, including design maneuvering speed (Va), which is the maximum speed at which abrupt and full control inputs can be made without exceeding the airplane's structural limits. In training contexts, the term also refers more broadly to the recommended speeds for performing training maneuvers such as steep turns, chandelles, lazy eights, and eights on pylons.
Context Anchor
In the , this term appears in discussions of training maneuvers such as eights on pylons, where sets an appropriate speed before beginning the .