V1 - 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.

V2 - Takeoff safety speed.

V2min - Minimum takeoff safety speed.

VA - Maneuvering Speed (max. structural speed allowed for full control deflection).

VB - Design speed for maximum gust intensity.

VC - Design cruising speed.

VD - Maximum Dive Speed (for certification only).

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.

VFE - Maximum Flaps Extended Speed.

VFTO - Final takeoff speed.

VH - Maximum speed in level flight with maximum continuous power.

VLE - Maximum Landing Gear Extended Speed.

VLO - Maximum Landing Gear Operation Speed.

VLOF - Lift-off speed.

VMC - Minimum controllable speed with the critical engine inoperative.

VMO/MMO - Maximum operating limit speed.

VMU - Minimum unstick speed.

VNE - Never-Exceed Speed.

VNO - Maximum Structural Cruising Speed.

VR - Rotation Speed.

VREF - Reference landing speed.

VS - The stalling speed or the minimum steady flight speed at which the airplane is controllable.

VSO - Stalling Speed Landing Configuration.

VS1 - Stalling speed or the minimum steady flight speed obtained in a specific configuration.

VSR - means reference stall speed.

VSRO - means reference stall speed in the landing configuration.

VSR1 - means reference stall speed in a specific configuration.

VSSE - Minimum Safe Single Engine Speed.

V SW - Speed at which onset of natural or artificial stall warning occurs.

VTOSS - Takeoff safety speed for Category A rotorcraft.

VX - Best Angle of Climb Speed.

VXSE - Best Angle of Climb Speed, 1 engine inoperative.

VY - Best Rate of Climb Speed.

VYSE - Best Rate of Climb Speed, 1 engine inoperative.

VENTURI TUBE - A small, hourglass-shaped metal tube, usually set laterally on a fuselage in the slipstream to create suction for gyroscopic panel instruments.

VFR OVER-THE-TOP - With respect to the operation of aircraft, means the operation of an aircraft over-the-top under VFR when it is not being operated on an IFR flight plan.

VSI - Vertical Speed Indicator. A panel instrument that gauges rate of climb or descent in feet-per-minute.

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