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Takeoff Safety Speed

VA design manoeuvring speed (stalling speed at the maximum legal G-force, and hence the maximum speed at which abrupt control movements will not cause the aircraft to exceed its G-force limit)
VFE maximum flap extended speed (a different maximum speed may be specified for partial flap extension)
VLE maximum landing gear extended speed
VLO maximum landing gear operating speed
VMC minimum control speed with the critical engine inoperative
VNE never-exceed speed
VR rotation speed
VNO maximum structural cruising speed (the maximum speed to be used in turbulent conditions)
VREF reference landing approach speed; speed (in calm air) at the landing screen height of 50 ft.Often used by pilots as a base from which to calculate speeds to be used during landing, and calculated as 1.3×VS0
VS the stalling speed or the minimum steady flight speed at which the airplane is controllable Usually synonymous with VS1
VS0 the stalling speed or the minimum steady flight speed in the landing configuration
VS1 the stalling speed or the minimum steady flight speed obtained in a specific configuration (usually a “clean” configuration of flaps, landing gear and other sources of drag)
VX speed for best angle of climb. This provides the best altitude gain per unit of horizontal distance, and is usually used for clearing obstacles during takeoff
VY speed for best rate of climb. This provides the best altitude gain per unit of time, and is used for normal climbout, and for en-route climb under instrument flight rules (IFR), or to climb above icing

Speeds used in high performance aircraft and other reference speeds

VB design speed for maximum gust intensity
VC design cruising speed
VD design diving speed. Usually 1.4×VNO
VDF/MDF demonstrated flight diving speed
VEF the speed at which the critical engine is assumed to fail during takeoff
VF design flap speed
VFC/MFC maximum speed for stability characteristics
VFTO final takeoff speed
VH maximum speed in level flight with maximum continuous power
VLOF lift-off speed
VMO/MMO maximum operating limit speed
VMU minimum unstick speed
VSR reference stall speed
VSR0 reference stall speed in the landing configuration
VSR1 reference stall speed in a specific configuration
VSW speed at which onset of natural or artificial stall warning occurs
VTOSS takeoff safety speed for Category A rotorcraft
V1 the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance. Any problems after V1 are treated as inflight emergencies
V2 takeoff safety speed. Also called takeoff screen speed, the minimum speed in the second segment of a climb following an engine failure
V2min minimum takeoff safety speed

Non-regulatory speeds

VBE best endurance speed; the speed that gives the greatest airborne time for fuel consumed. This may be used when there is reason to remain aloft for an extended period, such as waiting for a forecast improvement in weather on the ground
VBG best power-off glide speed; the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available
VXSE speed for best angle climb with the critical engine inoperative
VYSE speed for best rate of climb with the critical engine inoperative


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