| V speeds | |
|---|---|
| A single-engine Cessna 150L's airspeed indicator indicating its V speeds. |
In aviation, V-speeds are standard terms used to define airspeeds important or useful to the operation of all aircraft including fixed-wing aircraft, gliders, autogiros, helicopters, 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 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]
Proper display of V speeds is an airworthiness requirement for type-certificated aircraft in most countries.[5][6]
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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.[7] In Canada, the regulatory body, Transport Canada, defines 26 commonly used V-speeds in their Aeronautical Information Manual (AIM).[8]
These V-speeds are defined by regulations.
| V-speed designator | Description |
|---|---|
| V1 | Critical engine failure recognition speed. (See V1 definitions below)[7][8][9] |
| V2 | Takeoff safety speed. The speed at which the aircraft may safely become airborne with one engine inoperative.[7][8][9] |
| V2min | Minimum takeoff safety speed.[7][8][9] |
| V3 | Flap retraction speed.[8][9] |
| V4 | Steady initial climb speed. The all engines operating take-off climb speed used to the point where acceleration to flap retraction speed is initiated. Should be attained by a gross height of 400 feet.[10] |
| 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.[7][8][11][9] The heavier an aircraft is loaded the faster this speed. |
| Vat | Indicated airspeed at threshold, which is equal to the stall speed VS0 multiplied by 1.3 or stall speed VS1g multiplied by 1.23 in the landing configuration at the maximum certificated landing mass. If both VS0 and VS1g are available, the higher resulting Vat shall be applied.[12] |
| VB | Design speed for maximum gust intensity.[7][8][9] |
| VC | Design cruising speed, also known as the optimum cruise speed, is the most efficient speed in terms of distance, speed and fuel usage.[7][8][11][9] |
| Vcef | See V1; generally used in documentation of military aircraft performance.[13] |
| VD | Design diving speed.[7][8][9] |
| VDF | Demonstrated flight diving speed.[7][8][9] |
| VEF | The speed at which the Critical engine is assumed to fail during takeoff.[7] |
| VF | Designed flap speed.[7][8][9] |
| VFC | Maximum speed for stability characteristics.[7][9] |
| VFE | Maximum flap extended speed.[7][8][9] |
| VFTO | Final takeoff speed.[7] |
| VH | Maximum speed in level flight at maximum continuous power.[7][8][9] |
| 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.[7][8][9][14] |
| 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.[7][8][9][14] |
| VLOF | Lift-off speed.[7][9] |
| VMC | Minimum control speed with Critical engine inoperative.[7][8][9] |
| Vmca | Minimum control speed in the take-off configuration – the minimum calibrated airspeed at which the aircraft is directionally controllable in flight with a sudden Critical engine failure and takeoff power on the operative engine(s).[9] |
| 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.[9][15] |
| Vmcl | Minimum control speed in the landing configuration with one engine inoperative.[9][15] |
| VMO | Maximum operating limit speed.[7][8][9] |
| VMU | Minimum unstick speed.[7][8][9] |
| VNE | Never exceed speed.[7][8][9][16] |
| VNO | Maximum structural cruising speed or maximum speed for normal operations.[7][8][9] |
| VR | Rotation speed. The speed at which the aircraft's nosewheel leaves the ground.[7][8][9] Also see note on Vref below. |
| Vrot | Used instead of VR (in discussions of the takeoff performance of military aircraft) to denote rotation speed in conjunction with the term Vref (refusal speed).[13] |
| VRef | Landing reference speed or threshold crossing speed.[7][8][9]
In discussions of the takeoff performance of military aircraft, the term Vref stands for refusal speed. Refusal speed is the maximum speed during takeoff from which the air vehicle can stop within the available remaining runway length for a specified altitude, weight, and configuration.[13] Incorrectly, or as an abbreviation, some documentation refers to Vref and/or Vrot speeds as "Vr."[17] |
| VS | Stall speed or minimum steady flight speed for which the aircraft is still controllable.[7][8][9] |
| VS0 | Stall speed or minimum flight speed in landing configuration.[7][8][9] |
| VS1 | Stall speed or minimum steady flight speed for which the aircraft is still controllable in a specific configuration.[7][8] |
| VSR | Reference stall speed.[7] |
| VSR0 | Reference stall speed in landing configuration.[7] |
| VSR1 | Reference stall speed in a specific configuration.[7] |
| VSW | Speed at which the stall warning will occur.[7] |
| VTOSS | Category A rotorcraft takeoff safety speed.[7][16] |
| VX | Speed that will allow for best angle of climb.[7][8] |
| VY | Speed that will allow for the best rate of climb.[7][8] |
Some of these V-speeds are specific to particular types of aircraft and are not defined by 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.[11] |
| VBG | Best power-off glide speed – the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available.[11] |
| VBR | Best range speed – the speed that gives the greatest range for fuel consumed - often identical to Vmd.[18] |
| VFS | Final segment of a departure with one powerplant failed.[19] |
| Vimd | Minimum drag[20] |
| Vimp | Minimum power[20] |
| VLLO | Maximum landing light operating speed – for aircraft with retractable landing lights.[9] |
| Vmbe | Maximum brake energy speed[21][20] |
| Vmd | Minimum drag (per lift) - often identical to VBR.[18][21] (alternatively same as Vimd[22]) |
| Vmin | Minimum speed for instrument flight (IFR) for helicopters[16] |
| Vmp | Minimum power[21] |
| Vp | Aquaplaning speed[23] |
| VPD | Maximum speed at which whole-aircraft parachute deployment has been demonstrated[24] |
| Vra | Rough air speed (turbulence penetration speed).[9] |
| VSL | stall speed in a specific configuration[9][21] |
| Vs1g | stall speed at maximum lift coefficient[21] |
| Vsse | Safe single engine speed[25] |
| Vt | Threshold speed[21] |
| Vtocs | Take-off climbout speed (helicopters)[16] |
| Vtos | Minimum speed for a positive rate of climb with one engine inoperative[21] |
| Vtmax | Max threshold speed[26][21] |
| Vwo | Maximum window or canopy open operating speed[27] |
| 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.[25] |
| 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.[14][25] |
| VZRC | Zero rate of climb speed in a twin-engine aircraft[21] |
Whenever a limiting speed is expressed in terms of Mach number, it is expressed as an "M speed", e.g. VMO: Maximum operating limit speed (in knots), MMO: Maximum operating limit Mach.[7][8]
V1 is the critical engine failure recognition speed or takeoff decision speed. It is the decision speed nominated by the pilot which satisfies all safety rules, and above which the takeoff will continue even if an engine fails.[9] The speed will vary between aircraft types and also due to aircraft weight, runway length, wing flap setting, engine thrust used, runway surface contamination and other factors.
V1 is defined differently in different jurisdictions:
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