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 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 certified aircraft in most parts of the world.[4][5]
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]
| 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] |
| V2 | Takeoff safety speed.[6][7] |
| V2min | Minimum takeoff safety speed.[6][7] |
| V3 | Flap retraction speed.[7] |
| 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][8] |
| VB | Design speed for maximum gust intensity.[6][7] |
| 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][8] |
| VD | Design diving speed.[6][7] |
| VDF | Demonstrated flight diving speed.[6][7] |
| VEF | The speed at which the critical engine is assumed to fail during takeoff.[6] |
| VF | Designed flap speed.[6][7] |
| VFC | Maximum speed for stability characteristics.[6] |
| VFE | Maximum flap extended speed.[6][7] |
| VFTO | Final takeoff speed.[6] |
| VH | Maximum speed in level flight at maximum continuous power.[6][7] |
| 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] |
| 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][9] |
| VLOF | Lift-off speed.[6] |
| VMC | Minimum control speed with Critical engine inoperative.[6][7] |
| VMO | Maximum operating limit speed.[6][7] |
| VMU | Minimum unstick speed.[6][7] |
| VNE | Never exceed speed.[6][7] |
| VNO | Maximum structural cruising speed.[6][7] |
| VR | Rotation speed. The speed at which the airplane's nosewheel leaves the ground.[6][7] |
| VRef | Landing reference speed.[6][7] |
| VS | Stall speed or minimum steady flight speed for which the aircraft is still controllable in the landing configuration.[6][7] |
| VS0 | Stall speed or minimum flight speed in landing configuration.[6] |
| 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 speed.[6] |
| 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] |
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.[8] |
| VBG | Best power-off glide speed – the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available.[8] |
| 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.[10] |
| 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.[9] |
| 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 |
References
- ^ Love, Michael C. (2005). "2", Better Takeoffs & Landings. Mc-Graw Hill, 13-15. ISBN 0070388059. Retrieved on 2008-05-07.
- ^ Craig, Paul A. (2004). "1", Multiengine Flying, 3rd, McGraw Hill, 3-6. ISBN 0071421394. Retrieved on 2008-05-07.
- ^ Federal Aviation Administration (July 2008). "Title 14: Aeronautics and Space PART 23—AIRWORTHINESS STANDARDS: NORMAL, UTILITY, ACROBATIC, AND COMMUTER CATEGORY AIRPLANES Subpart G—Operating Limitations and Information Markings And Placards, Part 23, §23.1545". Retrieved on 2008-08-01.
- ^ a b "Pilot Handbook - Chapters 6 through 9" (PDF). FAA. Retrieved on 2008-05-07.
- ^ Federal Aviation Administration (July 2008). "Title 14: Aeronautics and Space PART 25—AIRWORTHINESS STANDARDS: TRANSPORT CATEGORY AIRPLANES Subpart G—Operating Limitations and Information Airplane Flight Manual, Part 25, §25.1583". Retrieved on 2008-08-01.
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae af ag ah ai "Electronic Code of Federal Regulations - Chapter 14.1". Federal Aviation Administration. Retrieved on 2008-05-07.
- ^ a b c d e f g h i j k l m n o p q r s t u v w x y z Transport Canada (March 2008). "Aeronautical Information Manual GEN - 1.0 GENERAL INFORMATION". Retrieved on 2008-05-12.
- ^ a b c d Brandon, John (2000-2007). "Airspeed and the Properties of Air". Retrieved on 2008-05-08.
- ^ a b c (2007) Pilot's Encyclopedia of Aeronautical Knowledge. Federal Aviation Administration, G-16. ISBN 978-1-60239-034-8. Retrieved on 2008-05-12.
- ^ "Aviation Terms & More - V-speeds".
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