V speeds
Encyclopedia
In aviation
Aviation
Aviation is the design, development, production, operation, and use of aircraft, especially heavier-than-air aircraft. Aviation is derived from avis, the Latin word for bird.-History:...

, V-speeds are standard terms used to define airspeed
Airspeed
Airspeed is the speed of an aircraft relative to the air. Among the common conventions for qualifying airspeed are: indicated airspeed , calibrated airspeed , true airspeed , equivalent airspeed and density airspeed....

s important or useful to the operation of all aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...

 including fixed-wing aircraft
Fixed-wing aircraft
A fixed-wing aircraft is an aircraft capable of flight using wings that generate lift due to the vehicle's forward airspeed. Fixed-wing aircraft are distinct from rotary-wing aircraft in which wings rotate about a fixed mast and ornithopters in which lift is generated by flapping wings.A powered...

, gliders
Glider aircraft
Glider aircraft are heavier-than-air craft that are supported in flight by the dynamic reaction of the air against their lifting surfaces, and whose free flight does not depend on an engine. Mostly these types of aircraft are intended for routine operation without engines, though engine failure can...

, autogiros, helicopter
Helicopter
A helicopter is a type of rotorcraft in which lift and thrust are supplied by one or more engine-driven rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forwards, backwards, and laterally...

s, and dirigibles. 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
Type certificate
A Type Certificate, is awarded by aviation regulating bodies to aerospace manufacturers after it has been established that the particular design of a civil aircraft, engine, or propeller has fulfilled the regulating bodies' current prevailing airworthiness requirements for the safe conduct of...

 testing. Using them is considered a best practice
Best practice
A best practice is a method or technique that has consistently shown results superior to those achieved with other means, and that is used as a benchmark...

 to maximize aviation safety, aircraft performance or both.

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
Indicated airspeed
Indicated airspeed is the airspeed read directly from the airspeed indicator on an aircraft, driven by the pitot-static system. IAS is directly related to calibrated airspeed , which is the IAS corrected for instrument and installation errors....

, 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
Airspeed indicator
The airspeed indicator or airspeed gauge is an instrument used in an aircraft to display the craft's airspeed, typically in knots, to the pilot.- Use :...

. 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.

Proper display of V speeds is an airworthiness requirement for type-certificated aircraft in most countries.

Regulation

The most common V-speeds are often defined by a particular government's aviation regulation
Aviation law
Aviation law is the branch of law that concerns flight, air travel, and associated legal and business concerns. Some of its area of concern overlaps that of admiralty law and in many cases, aviation law is considered a matter of international law due to the nature of air travel. However, the...

s. In the United States, these are defined in title 14 of the United States Code of Federal Regulations
Code of Federal Regulations
The Code of Federal Regulations is the codification of the general and permanent rules and regulations published in the Federal Register by the executive departments and agencies of the Federal Government of the United States.The CFR is published by the Office of the Federal Register, an agency...

, known as the Federal Aviation Regulations
Federal Aviation Regulations
The Federal Aviation Regulations, or FARs, are rules prescribed by the Federal Aviation Administration governing all aviation activities in the United States. The FARs are part of Title 14 of the Code of Federal Regulations...

 or FARs. In Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

, the regulatory body, Transport Canada
Transport Canada
Transport Canada is the department within the government of Canada which is responsible for developing regulations, policies and services of transportation in Canada. It is part of the Transportation, Infrastructure and Communities portfolio...

, defines 26 commonly used V-speeds in their Aeronautical Information Manual (AIM).

Regulatory V-speeds

These V-speeds are defined by regulations.
V-speed designator Description
V1 Critical engine failure recognition speed. (See V1 definitions below)
V2 Takeoff safety speed. The speed at which the aircraft may safely become airborne 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 400 feet.
VA Design maneuvering speed
Maneuvering speed
In aviation, maneuvering speed is the maximum speed where full, abrupt control movement in the pitch axis will result in an aerodynamic stall of the aircraft prior to exceeding the design load limit. It has been widely misunderstood that flight below maneuvering speed will provide total protection...

, 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. 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.
VB Design speed for maximum gust intensity.
VC Design cruising speed, 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.
VD Design diving speed.
VDF Demonstrated flight diving speed.
VEF The speed at which the Critical engine
Critical engine
The critical engine of a multi-engine, fixed-wing aircraft is the one whose failure would result in the most adverse effects on the aircraft's handling and performance.- Description :...

 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 it is safe to fly a retractable gear aircraft with the landing gear extended.
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.
VLOF Lift-off speed.
VMC Minimum control speed with Critical engine
Critical engine
The critical engine of a multi-engine, fixed-wing aircraft is the one whose failure would result in the most adverse effects on the aircraft's handling and performance.- Description :...

 inoperative.
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
Critical engine
The critical engine of a multi-engine, fixed-wing aircraft is the one whose failure would result in the most adverse effects on the aircraft's handling and performance.- Description :...

 failure and takeoff power on the operative engine(s).
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.
Vmcl Minimum control speed in the landing configuration with one engine inoperative.
VMO Maximum operating limit speed.
VMU Minimum unstick speed.
VNE Never exceed speed.
VNO Maximum structural cruising speed or maximum speed for normal operations.
VR Rotation
Takeoff
Takeoff is the phase of flight in which an aerospace vehicle goes from the ground to flying in the air.For horizontal takeoff aircraft this usually involves starting with a transition from moving along the ground on a runway. For balloons, helicopters and some specialized fixed-wing aircraft , no...

 speed. The speed at which the aircraft's nosewheel
Tricycle gear
Tricycle gear describes an aircraft undercarriage, or landing gear, arranged in a tricycle fashion. The tricycle arrangement has one wheel in the front, called the nose wheel, and two or more main wheels slightly aft of the center of gravity...

 leaves the ground. 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).
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
Angle of Climb
In aerodynamics, angle of climb is the ratio between distance travelled over the ground and altitude gained. The angle of climb can be expressed as the angle between a plane horizontal to the Earth's surface and the actual flight path followed by the aircraft during its ascent...

.
VY Speed that will allow for the best rate of climb
Rate of climb
In aeronautics, the rate of climb is an aircraft's vertical speed - the rate of change in altitude. In most ICAO member countries , this is usually expressed in feet per minute and can be abbreviated as ft/min. Elsewhere, it is commonly expressed in metres per second, abbreviated as m/s...

.

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. 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.
VBG Best power-off glide speed – the speed that provides maximum lift-to-drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

 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
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

Vimp Minimum power
VLLO Maximum landing light operating speed – for aircraft with retractable landing lights.
Vmbe Maximum brake energy speed
Vmd Minimum drag
Drag (physics)
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow velocity...

 (per lift
Lift (force)
A fluid flowing past the surface of a body exerts a surface force on it. Lift is the component of this force that is perpendicular to the oncoming flow direction. It contrasts with the drag force, which is the component of the surface force parallel to the flow direction...

) - often identical to VBR. (alternatively same as Vimd)
Vmin Minimum speed for instrument flight (IFR
Instrument flight rules
Instrument flight rules are one of two sets of regulations governing all aspects of civil aviation aircraft operations; the other are visual flight rules ....

) for helicopters
Vmp Minimum power
Vp Aquaplaning speed
VPD Maximum speed at which whole-aircraft parachute
Ballistic Recovery Systems
Ballistic Recovery Systems is a manufacturer of aircraft ballistic parachutes .The company was formed in 1980 by Boris Popov after he survived a fall in a partly collapsed hang glider in 1975...

 deployment has been demonstrated
Vra Rough air speed (turbulence penetration speed).
VSL stall speed in a specific configuration
Vs1g stall speed at maximum lift coefficient
Vsse Safe single engine speed
Vt Threshold speed
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.
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.
VZRC Zero rate of climb speed in a twin-engine aircraft

Mach numbers

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.

V1 definitions

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. The speed will vary between aircraft types and also due to aircraft weight, runway length, wing flap
Flap (aircraft)
Flaps are normally hinged surfaces mounted on the trailing edges of the wings of a fixed-wing aircraft to reduce the speed an aircraft can be safely flown at and to increase the angle of descent for landing without increasing air speed. They shorten takeoff and landing distances as well as...

 setting, engine thrust used, runway surface contamination and other factors.

V1 is defined differently in different jurisdictions:
  • The US Federal Aviation Administration
    Federal Aviation Administration
    The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...

     defines it as: V1 means the maximum speed in the takeoff at which the pilot must take the first action (e.g., apply brakes, reduce thrust, deploy speed brakes) to stop the airplane within the accelerate-stop distance. V1 also means the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff and achieve the required height above the takeoff surface within the takeoff distance.

  • Transport Canada
    Transport Canada
    Transport Canada is the department within the government of Canada which is responsible for developing regulations, policies and services of transportation in Canada. It is part of the Transportation, Infrastructure and Communities portfolio...

    defines it as: Critical engine failure recognition speed and adds: This definition is not restrictive. An operator may adopt any other definition outlined in the aircraft flight manual (AFM) of TC type-approved aircraft as long as such definition does not compromise operational safety of the aircraft.
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