In aviation, V-speeds are standard terms used to define airspeeds
important or useful to the operation of all aircraft. 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.
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 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. The yellow range is the range in which
the aircraft may be operated in smooth air, and then only with caution
to avoid abrupt control movement, and the red line is the VNE, the
never exceed speed.
Proper display of
1 Regulations 2 Regulatory V-speeds 3 Other V-speeds 4 Mach numbers 5 V1 definitions 6 References 7 Further reading
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
V-speed designator Description
V1 The speed beyond which the takeoff should no longer be aborted. (See V1 definitions below)
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 400 ft (120 m).
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.
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. Also called "approach speed".
VB Design speed for maximum gust intensity.
VC Design cruise speed, used to show compliance with gust intensity loading.
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.
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.
Minimum control speed
Minimum control speed
Minimum control speed
VMO Maximum operating limit speed. Exceeding VMO may trigger an overspeed alarm.
VMU Minimum unstick speed.
VNE Never exceed speed.
VNO Maximum structural cruising speed or maximum speed for normal operations.
VO Maximum operating maneuvering speed.
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. (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."
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.
Other V-speeds 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.
VBG Best power-off glide 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.
Vmbe Maximum brake energy speed
Vmd Minimum drag (per lift) – often identical to VBR. (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
Vsse Safe single-engine speed
Vt Threshold speed
VTD Touchdown speed
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 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, while maintaining a small bank angle that should be presented with the engine-out climb performance data.
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, while maintaining a small bank angle that should be presented with the engine-out climb performance data.
VZRC Zero rate of climb speed in a twin-engine aircraft
Mach numbers Whenever a limiting speed is expressed by a Mach number, it is expressed relative to the speed of sound, e.g. VMO: Maximum operating speed, MMO: Maximum operating Mach number. V1 definitions V1 is the critical engine failure recognition speed or takeoff decision speed. It is the speed above which the takeoff will continue even if an engine fails or another problem occurs, such as a blown tire. The speed will vary among aircraft types and varies according to factors such as aircraft weight, runway length, wing flap setting, engine thrust used and runway surface contamination, thus it must be determined by the pilot before takeoff. Aborting a takeoff after V1 is strongly discouraged because the aircraft will by definition not be able to stop before the end of the runway, thus suffering a "runway overrun". V1 is defined differently in different jurisdictions:
The US Federal
^ Love, Michael C. (2005). "2". Better Takeoffs & Landings.
Mc-Graw Hill. pp. 13–15. ISBN 0-07-038805-9. Retrieved
^ Craig, Paul A. (2004). "1". Multiengine Flying (3rd ed.). McGraw
Hill. pp. 3–6. ISBN 0-07-142139-4. Retrieved
Getting to grips with aircraft performance (PDF). Flight Operations Support & Line Assistance. Airbus Customer Services. January 2002.
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