Basic Information V-speed Designator Description

V1 Engine failure recognition speed or decision speed. It is the maximum speed in the take-off 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 take-off, following a failure of the critical engine at VEF, at which the pilot can continue the take-off and achieve the required height above the take-off surface within the take-off distance. If an engine failure is detected after V1, the take-off must be continued. This implies that the aircraft must be controllable on ground. Therefore, V1 is always greater than VMCG.

V2 Take-off safety speed. It is the minimum speed that needs to be maintained up to acceleration altitude, in the event of an engine failure after V1. Flight at V2 ensures that the minimum required climb gradient is achieved, and that the aircraft is controllable. V2 speed is always greater than VMCA, and facilitates control of the aircraft in flight. In an all-engines operative take-off, V2+10 provides a better climb performance than V2.

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 manoeuvring 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 equal to the stall speed VS0multiplied 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. Also called "approach speed".

VB Design speed for maximum gust intensity.

VC Design cruise speed, used to show compliance with gust intensity loading.

Vcef generally used in documentation of military aircraft performance as V1

VD Design diving speed.

VDF Demonstrated flight diving speed.

VEF The speed at which the Critical engine is assumed to fail during take-off.

VFDesigned flap speed.

VFC Maximum speed for stability characteristics.

VFE Maximum flap extended speed.

VFTO Final take-off 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. Mostly used as the minimum control speed for the take-off configuration (take-off flaps) in many publications. Several VMC's exist for different flight phases and airplane configurations: VMCG, VMCA, VMCA1, VMCA2, VMCL, VMCL1, VMCL2. Refer to the minimum control speed article for a thorough explanation.

VMCA Minimum control speed in the air (or airborne) for maintaining steady straight flight when an engine fails or is inoperative and with the corresponding opposite engine set to provide maximum thrust, provided a small (3° – ) 5° bank angle is being maintained away from the inoperative engine and the rudder is used up to maximum to maintain straight flight. The exact required bank angle should be provided by the manufacturer with VMC(A) data. Refer to the minimum control speed article for a description of (pilot-induced) factors that have influence on VMCA. VMCA is also presented as VMC in many manuals.

VMCG Minimum control speed on the ground is the lowest speed at which the take-off may be safely continued following an engine failure during the take-off run. Below VMCG, the throttles need to be closed at once when an engine fails, to avoid veering off the runway.

VMCL Minimum control speed in the landing configuration with one engine inoperative.

VMO Maximum operating limit speed.

VMU Minimum unstick speed. It is achieved by pitching the aircraft up to the maximum (tail on the runway, for aircraft that are geometrically-limited) during the take-off roll. The speed at which the aircraft first lifts off is VMU. Therefore, lift-off is not possible prior to VMU.

VNE Never exceed speed.

VNO Maximum structural cruising speed or maximum speed for normal operations.

VO Maximum operating manoeuvring speed.

VR Rotation speed. The speed at which the aircraft's nose wheel leaves the ground during take-off.

Vrot Used instead of VR (in discussions of the take-off performance of military aircraft) to denote rotation speed in conjunction with the term VRef (refusal speed).

VRef Landing reference speed or threshold crossing speed.

VRef stands for refusal speed for military aircraft. Refusal speed is the maximum speed during take-off from which the air vehicle can stop within the available remaining runway length for a specified altitude, weight, and configuration.

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.