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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.^[1] 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 type-certification testing. Using them is considered a best practice to maximize aviation safety, aircraft performance or both.^[2]

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.^[3][4]

Having V speeds properly displayed is an airworthiness requirement for type-certificated aircraft in most parts of the world.^[4][5]

Contents 1 Regulation 2 Regulatory V-speeds 3 Other V-speeds 4 References

[edit] Regulation

The most common V-speeds are often defined by a particular government's aviation regulations. In the United States, these are defined in title 14 of the United States Code of Federal Regulations, known as the Federal Aviation Regulations or FARs.^[6] In Canada, the regulatory body, Transport Canada, defines 26 commonly-used V-speeds in their Aeronautical Information Manual (AIM).^[7]

[edit] Regulatory V-speeds

These V-speeds are defined by government regulations.

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).[6][7][8]
V2	Takeoff safety speed.[6][7][8]
V2min	Minimum takeoff safety speed.[6][7][8]
V3	Flap retraction speed.[7][8]
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.[6][7][9][8]
VB	Design speed for maximum gust intensity.[6][7][8]
VC	Design cruising speed, also known as the optimum cruise speed, is the most efficient speed in terms of distance, speed and fuel usage.[6][7][9][8]
VD	Design diving speed.[6][7][8]
VDF	Demonstrated flight diving speed.[6][7][8]
VEF	The speed at which the critical engine is assumed to fail during takeoff.[6]
VF	Designed flap speed.[6][7][8]
VFC	Maximum speed for stability characteristics.[6][8]
VFE	Maximum flap extended speed.[6][7][8]
VFTO	Final takeoff speed.[6]
VH	Maximum speed in level flight at maximum continuous power.[6][7][8]
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.[6][7][8][10]
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.[6][7][8][10]
VLOF	Lift-off speed.[6][8]
VMC	Minimum control speed with Critical engine inoperative.[6][7][8]
Vmcg	Minimum control speed on the ground - the minimum airspeed at which the aircraft is directionally controllable during acceleration along the runway with one engine inoperative, takeoff power on the operative engine(s), and with nose wheel steering assumed inoperative.[8][11]
VMO	Maximum operating limit speed.[6][7][8]
VMU	Minimum unstick speed.[6][7][8]
VNE	Never exceed speed.[6][7][8][12]
VNO	Maximum structural cruising speed or maximum speed for normal operations.[6][7][8]
VR	Rotation speed. The speed at which the airplane's nosewheel leaves the ground.[6][7][8]
VRef	Landing reference speed or threshold crossing speed.[6][7][8]
VS	Stall speed or minimum steady flight speed for which the aircraft is still controllable.[6][7][8]
VS0	Stall speed or minimum flight speed in landing configuration.[6][7][8]
VS1	Stall speed or minimum steady flight speed for which the aircraft is still controllable in a specific configuration.[6][7]
VSR	Reference stall speed.[6]
VSR0	Reference stall speed in landing configuration.[6]
VSR1	Reference stall speed in a specific configuration.[6]
VSW	Speed at which the stall warning will occur.[6]
VTOSS	Category A rotorcraft takeoff safety speed.[6][12]
VX	Speed that will allow for best angle of climb.[6][7]
VY	Speed that will allow for the best rate of climb.[6][7]

[edit] 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.[9]
VBG	Best power-off glide speed – the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available.[9]
VBR	Best range speed – the speed that gives the greatest range for fuel consumed - identical to Vmd.[13]
VFS	Final segment of a departure with one powerplant failed.[14]
Vimd	Minimum drag[15]
Vimp	Minimum power[15]
VLLO	Maximum landing light operating speed – for aircraft with retractable landing lights.[8]
Vmbe	Maximum brake energy speed[16][15]
Vmd	Minimum drag- identical to VBR.[13][16]
Vmca	Minimum control speed in the air – the minimum airspeed at which the aircraft is directionally controllable in flight with one engine inoperative and takeoff power on the operative engine(s). Aircraft certification standards specify the most critical engine becoming inoperative and its propeller windmilling (propeller unfeathered), not more than a 5 degree bank towards the operative engine, takeoff power on the operative engine(s), landing gear up, flaps in the takeoff position, and center of gravity in the most unfavorable position. In the USA Vmca is defined at FAR Part 23.149 for normal category and commuter category airplanes; and Part 25.149 for transport category airplanes.[8]
Vmcl	Minimum control speed in the air in an approach or landing configuration with one engine inoperative.[8]
Vmin	Minimum speed for instrument flight (IFR) for helicopters[12]
Vmp	Minimum power[16]
Vp	Aquaplaning speed[17]
VPD	Maximum speed at which whole-aircraft parachute deployment has been demonstrated[18]
Vra	Rough air speed (turbulence penetration speed).[8]
VSL	stall speed in a specific configuration[8][16]
Vs1g	stall speed at maximum lift coefficient[16]
Vsse	Safe single engine speed[19]
Vt	Threshold speed[16]
Vtocs	Take-off climbout speed (helicopters)[12]
Vtos	Minimum speed for a positive rate of climb with one engine inoperative[16]
Vtmax	Max threshold speed[20][16]
Vwo	Maximum window or canopy open operating speed[21]
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.[19]
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.[10][19]
VZRC	Zero rate of climb speed in a twin-engine aircraft[16]

[edit] References

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