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In aviation, V-speeds are standard terms used to define important or useful to the operation of all aircraft. These speeds are derived from data obtained by aircraft designers and manufacturers during flight testing for aircraft Type certificate. Using them is considered a best practice to maximize aviation safety, aircraft performance, or both.
The actual speeds represented by these designators are specific to a particular model of aircraft. They are expressed by the aircraft's indicated airspeed (and not by, for example, the ground speed), so that pilots may use them directly, without having to apply correction factors, as aircraft instruments also show indicated airspeed.
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 white arc and the green arc are the stalling speed with wing flaps in landing configuration, and stalling speed with wing flaps retracted, respectively. These are the stalling speeds for the aircraft at its maximum weight. The yellow band is the range in which the aircraft may be operated in smooth air, and then only with caution to avoid abrupt control movement. The red line is the VNE, the never-exceed speed.
Proper display of V-speeds is an airworthiness requirement for type-certificated aircraft in most countries.
| V1 | The speed beyond which takeoff should no longer be Rejected takeoff (or "the point of no return") .Peppler, I.L.: From The Ground Up, page 327. Aviation Publishers Co. Limited, Ottawa Ontario, Twenty Seventh Revised Edition, 1996. |
| V2 | Takeoff safety speed. The speed at which the aircraft may safely climb with one engine inoperative. |
| V2min | Minimum takeoff safety speed. |
| V3 | Flap retraction speed. |
| 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 . |
| VA | Design maneuvering speed. 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. FAA Advisory Circular 23-19A Airframe Guide for Certification of Part 23 Airplanes, Section 48 (p.27) Retrieved 2012-01-06 |
| Vat | Indicated airspeed at threshold, which is usually 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, though some manufacturers apply different criteria. If both VS0 and VS1g are available, the higher resulting Vat shall be applied.PANS-OPS, Volume I, Part I, Section 4, Chapter 1, 1.3.3 Also called "approach speed"
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Davies defines Vat and Vref as equivalent. |
| VB | Design speed for maximum wind gust intensity. |
| VC | Design cruise, also known as the optimum cruise speed, is the most efficient speed in terms of distance, speed and fuel usage. |
| Vcef | See V1; generally used in documentation of military aircraft performance. Denotes "critical engine failure" speed as the speed during takeoff where the same distance would be required to either continue the takeoff or abort to a stop. MIL-STD-3013A Department of Defense Standard Practice: Glossary of definitions, ground rules, and mission profiles to define air vehicle performance capability. 9 September 2008. Page 21. |
| VD | Design diving speed, the highest speed planned to be achieved in testing. |
| VDF | Demonstrated flight diving speed, the highest actual speed achieved in testing. |
| 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 a retractable gear aircraft should be flown with the landing gear extended. |
| VLO | Maximum landing gear operating speed. This is the maximum speed at which the landing gear on a retractable gear aircraft should be extended or retracted. |
| VLOF | Lift-off speed. |
| VMC | Minimum control speed. The minimum speed at which the aircraft is still controllable with the critical engine inoperative. Like the stall speed, there are several important variables that are used in this determination. Refer to the minimum control speed article for a thorough explanation. VMC is sometimes further refined into more discrete V-speeds e.g. VMCA,VMCG. |
| VMCA | Minimum control speed air. The minimum speed that the aircraft is still controllable with the critical engine inoperative while the aircraft is airborne. VMCA is sometimes simply referred to as VMC. |
| VMCG | Minimum control speed ground. The minimum speed that the aircraft is still controllable with the critical engine inoperative while the aircraft is on the ground. |
| VMCL | Minimum control speed in the landing configuration with one engine inoperative. |
| VMO | Maximum operating limit speed. Exceeding VMO may trigger an overspeed alarm. |
| VMU | Minimum unstick speed. |
| VNE | Never exceed speed.Bell Helicopter Textron: Bell Model 212 Rotorcraft Flight Manual, page II. Bell Helicopters Textron Publishers, Fort Worth, Texas, Revision 3, 1 May 1998. BHT-212IFR-FM-1 In a helicopter, this is chosen to prevent retreating blade stall and prevent the advancing blade from going supersonic. |
| VNO | Maximum structural cruising speed or maximum speed for normal operations. Speed at which exceeding the limit load factor may cause permanent deformation of the aircraft structure. |
| VO | Maximum operating maneuvering speed. USA 14 CFR §23.1507 Retrieved 2012-01-06 |
| VR | Rotation speed. The speed at which the pilot begins to apply control inputs to cause the aircraft nose to pitch up, after which it will leave the ground. |
| 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). |
| VRef | Landing reference speed or threshold crossing speed. Must be at least 1.3 VS0. Must be at least VMC for reciprocating-engine aircraft, or 1.05 VMC for commuter category aircraft. 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. Incorrectly, or as an abbreviation, some documentation refers to Vref and/or Vrot speeds as "Vr." TPUB INTERMEDIATE FLIGHT PREPARATION WORKBOOK APPENDIX A |
| VS | Stall speed or minimum steady flight speed for which the aircraft is still controllable. |
| 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 safety speed. |
| VX | Speed that will allow for best angle of climb. |
| VY | Speed that will allow for the best rate of climb. |
| VAPP | Approach speed. Speed used during final approach with landing flap set. VREF plus safety increment, typically minimum 5 knots, and maximum 15 knots to avoid exceeding flap limiting speeds. Typically it is calculated as half the headwind component plus the gust factor. The purpose is to ensure that turbulence or gusts will not result in the airplane flying below VREF at any point on the approach. Also known as VFLY. |
| VBE | Best endurance speed – the speed that gives the greatest airborne time for fuel consumed. |
| VBG | Best Gliding flight speed – the speed that provides maximum lift-to-drag ratio and thus the greatest gliding distance available. |
| VBR | Best range speed – the speed that gives the greatest range for fuel consumed – often identical to Vmd. |
| VFS | Final segment of a departure with one powerplant failed. |
| Vimd | Minimum drag |
| Vimp | Minimum power |
| VLLO | Maximum landing light operating speed – for aircraft with retractable landing lights. |
| VLS | Lowest selectable speed |
| Vmbe | Maximum brake energy speed |
| Vmd | Minimum drag (per lift) – often identical to VBE. (alternatively same as Vimd) |
| Vmin | Minimum speed for instrument flight (IFR) for helicopters |
| Vmp | Minimum power |
| Vms | Minimum sink speed at median wing loading – the speed at which the minimum descent rate is obtained. In modern gliders, Vms and Vmc have evolved to the same value. |
| Vp | Aquaplaning speed |
| VPD | Maximum speed at which whole-aircraft parachute deployment has been demonstrated |
| Vra | Rough air speed (turbulence penetration speed). |
| VSL | Stall speed in a specific configuration |
| Vs1g | Stall speed at 1g load factor
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| Vsse | Safe single-engine speed |
| Vt | Threshold speed |
| VTD | Touchdown speedE.G. Tulapurkara, Chapter 10 Performance analysis VI – Take-off and landing, retrieved 18 November 2015 |
| VTGT | Target speed |
| VTO | Take-off speed. (see also VLOF) |
| Vtocs | Take-off climbout speed (helicopters) |
| Vtos | Minimum speed for a positive rate of climb with one engine inoperative |
| Vtmax | Max threshold speed |
| Vwo | Maximum window or canopy open operating speed |
| VXSE | Best angle of climb speed with one engine inoperative (OEI) in a light, twin-engine aircraft – the speed that provides the most altitude gain per unit of horizontal distance following an engine failure, while maintaining a small bank angle that should be presented with the engine-out climb performance data. |
| VYSE | Best rate of climb speed with one engine inoperative (OEI) in a light, twin-engine aircraft – the speed that provides the most altitude gain per unit of time following an engine failure, while maintaining a small bank angle that should be presented with the engine-out climb performance data. |
| VZF | Minimum zero flaps speed |
| VZRC | Zero rate of climb speed. The aircraft is at sufficiently low speed on the "back of the drag curve" that it cannot climb, accelerate, or turn, so must reduce drag. The aircraft cannot be recovered without loss of height. |
V1 is defined differently in different jurisdictions, and definitions change over time as aircraft regulations are amended.
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