V speeds

From wiki.flightgear.org

In aviation, V-speeds or Velocity-speeds are standard terms used to define airspeeds important or useful to the operation of aircraft, such as airplanes, gliders, autogiros, helicopters, blimps, and dirigibles. These speeds are derived from data obtained by aircraft designers and manufacturers during flight testing and verified in most countries by government flight inspectors during aircraft certification testing. Using them is considered a best practice to maximize aviation safety, aircraft performance or both.

The actual speeds represented by these designators are true airspeeds specific to a particular model of aircraft, and are expressed in terms of the aircraft's indicated airspeed, so that pilots may use them directly, without having to apply correction factors.

In general aviation aircraft, the most commonly-used and most safety-critical airspeeds are displayed as color-coded arcs and lines located on the face of an aircraft's airspeed indicator. The lower ends of the green arc and the white arc are the stalling speed with wing flaps retracted, and stalling speed with wing flaps fully extended, respectively. These are the stalling speeds for the aircraft at its maximum weight.

Having V speeds properly displayed is an airworthiness requirement for certified aircraft in most parts of the world.

V-speed designator	Description
V1	Maximum speed during takeoff at which a pilot can safely stop the aircraft without leaving the runway. This is also the minimum speed that allows the pilot to safely continue (to V2 takeoff) even if a critical engine failure occurs (between V1 and V2).
V2	Takeoff safety speed.
V2min	Minimum takeoff safety speed.
V3	Flap retraction speed.
VA	Design maneuvering speed, also known as the "Speed for maximum control deflection." This is the speed above which it is unwise to make full application of any single flight control (or "pull to the stops") as it may generate a force greater than the aircraft's structural limitations.
VB	Design speed for maximum gust intensity.
VC	Design cruising speed, also known as the optimum cruise speed, is the most efficient speed in terms of distance, speed and fuel usage.
VD	Design diving speed.
VDF	Demonstrated flight diving speed.
VEF	The speed at which the critical engine is assumed to fail during takeoff.
VF	Designed flap speed.
VFC	Maximum speed for stability characteristics.
VFE	Maximum flap extended speed.
VFTO	Final takeoff speed.
VH	Maximum speed in level flight at maximum continuous power.
VLE	Maximum landing gear extended speed. This is the maximum speed at which it is safe to fly a retractable gear aircraft with the landing gear extended.
VLO	Maximum landing gear operating speed. This is the maximum speed at which it is safe to extend or retract the landing gear on a retractable gear aircraft.
VLOF	Lift-off speed.
VMC	Minimum control speed with Critical engine inoperative.
VMO	Maximum operating limit speed.
VMU	Minimum unstick speed.
VNE	Never exceed speed.
VNO	Maximum structural cruising speed.
VR	Rotation speed. The speed at which the airplane's nosewheel leaves the ground.
VRef	Landing reference speed.
VS	Stall speed or minimum steady flight speed for which the aircraft is still controllable in the landing configuration.
VS0	Stall speed or minimum flight speed in landing configuration.
VS1	Stall speed or minimum steady flight speed for which the aircraft is still controllable in a specific configuration.
VSR	Reference stall speed.
VSR0	Reference stall speed in landing configuration.
VSR1	Reference stall speed in a specific configuration.
VSW	Speed at which the stall warning will occur.
VTOSS	Category A rotorcraft takeoff speed.
VX	Speed that will allow for best angle of climb.
VY	Speed that will allow for the best rate of climb.

Other V-speeds

Some of these V-speeds are specific to particular types of aircraft and are not defined by government regulations.

V-speed designator	Description
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	Best angle of climb speed with a single operating engine in a light, twin-engine aircraft – the speed that provides the most altitude gain per unit of horizontal distance following an engine failure.
VYSE	Best rate of climb speed with a single operating engine in a light, twin-engine aircraft – the speed that provides the most altitude gain per unit of time following an engine failure.
Vclmax	Max coefficient of lift speed
Vdmin	Minimum drag
Vfto	Final takeoff speed
Vimd	Minimum drag
Vimp	Minimum power
Vmbe	Maximum brake energy speed
Vmd	Minimum drag
Vmca	Minimum control speed, air – the minimum flight speed at which the aircraft is directionally controllable. Aircraft certification conditions include the most critical engine becoming inoperative and windmilling (propeller unfeathered), not more than a 5 degree bank towards the operative engine, takeoff power on the operative engine, landing gear up, flaps in takeoff position, and most unfavorable center of gravity. Defined by FAR Part 25.149, in the United States.
Vmcg	Minimum control speed, ground, with nose wheel steering assumed inoperative
Vmcl	Minimum control speed, approach and landing
Vme	Max endurance
Vmini	Minimum IFR speed for helicopters
Vmp	Minimum power
Vmr	Max range
Vnd	Max structural cruising speed
Vp	Aquaplaning speed
Vra	Rough air speed
Vs1g	One g stall speed
Vsse	Safe single engine speed
Vt	Threshold speed
Vtmax	Max threshold speed