V Speeds - List & Defanitions

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V Speeds - List & Defanitions

Post  Admin on Tue Dec 01, 2009 6:47 am

V speeds are speeds that define certain performance and limiting characteristics of an aircraft. They are established by the manufacturer during design and testing, and are specific to the aircraft model. In many cases, they are defined by reference to the standard atmosphere or other specific conditions, and/or at the aircraft's maximum gross weight, and the pilot is responsible for calculating the effective value based on the actual weight and air density..

In the U.S., V speeds are stated in knots or, for older aircraft models, miles per hour. For faster aircraft, some speeds are also defined by Mach number. Typically, V speeds are given for an aircraft at maximum gross weight, and should be adjusted downward if the aircraft is flying lighter.
Speeds frequently used in General Aviation
VA: design maneuvering speed (stalling speed at the maximum legal G-force, and hence the maximum speed at which abrupt control movements will not cause the aircraft to exceed its G-force limit).

;VFE: maximum flap extended speed (a different maximum speed may be specified for partial flap extension).

;VLE: maximum landing gear extended speed.

;VLO: maximum landing gear operating speed.

;VMC: minimum control speed with the critical engine inoperative.

;: never-exceed speed.

;VR: rotation speed. The speed of an aircraft at which the pilot initiates rotation to obtain the scheduled takeoff performance. It must be greater or equal to the V1 speed.

;: maximum structural cruising speed (the maximum speed to be used in turbulent conditions) or can refer to the velocity of normal operation. VNO is specified as the high end of a green arc on many airspeed indicators. This speed is specific to the aircraft model. The range above VNO is marked on the airspeed indicator as a yellow arc from VNO to the VNE.

;VREF: reference landing approach speed; speed (in calm air) at the landing screen height of 50 ft. Often used by pilots as a base from which to calculate speeds to be used during landing, and calculated as 1.3×VS0 ( JAR regulations changed : Class B 1,3 Vso and Class A 1,23Vsro ).

;: the stalling speed or the minimum steady flight speed at which the airplane is controllable. Usually synonymous with VS1.

;VS0: the stalling speed or the minimum steady flight speed in the landing configuration.

;VS1: the stalling speed or the minimum steady flight speed obtained in a specific configuration (usually a "clean" configuration of flaps, landing gear and other sources of drag).

;VX: speed for best angle of climb. This provides the best altitude gain per unit of horizontal distance, and is usually used for clearing obstacles during takeoff.

;VY: speed for best rate of climb. This provides the best altitude gain per unit of time, and is used for normal climbout, and for en-route climb under instrument flight rules (IFR), or to climb above icing.
Speeds used in high performance aircraft and other reference speeds
VB: design speed for maximum gust intensity.

;: design cruising speed.

;VD: design diving speed. Usually 1.4×VNO.

;VDF/MDF: demonstrated flight diving speed.

;VEF: the speed at which the critical engine is assumed to fail during takeoff.

;VF: design flap speed.

;VFC/MFC: maximum speed for stability characteristics.

;VFTO: final takeoff speed.

;VH: maximum speed in level flight with maximum continuous power.

;VLOF: lift-off speed.

;VMO/MMO: maximum operating limit speed.

;VMU: minimum unstick speed.

;VSR: reference stall speed.

;VSR0: reference stall speed in the landing configuration.

;VSR1: reference stall speed in a specific configuration.

;VSW: speed at which onset of natural or artificial stall warning occurs.

;VTOSS: takeoff safety speed for Category A rotorcraft.

;V1: critical engine failure recognition speed. V1 is the minimum speed in the takeoff, following a failure of the critical engine at VEF, at which the pilot can continue the takeoff with only the remaining engines. Any problems after V1 are treated as inflight emergencies. In the case of a balanced field takeoff, V1 is 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 and the minimum speed at which the takeoff can be continued and achieve the required height above the takeoff surface within the takeoff distance. In this context, V1 is the takeoff decision speed.

;V2: takeoff safety speed. Also called takeoff screen speed, the minimum speed in the second segment of a climb following an engine failure.

;V2min: minimum takeoff safety speed.
Non-regulatory speeds
These values are not defined by FAA regulations.

;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 ratio and thus the greatest gliding distance available.

;VXSE: speed for best angle climb with the critical engine inoperative.

;VYSE: speed for best rate of climb with the critical engine inoperative.

;V2: t/o safety speed

;V3: steady initial climb speed with all engines operating

;V4: steady climb speed with all engines operating to be achieved by 400 ft gross height

;Va: design maneuvering speed

;Vc: design cruising speed.

;Vclmax: max coefficient of lift speed.

;Vd: design diving speed

;Vdmin: minimum drag

;Vdf: demonstrated flight diving speed

;Vef: the CAS at which the critical engine is assumed to fail

;Vf: design flap speed

;Vfe: max flap extended speed

;Vfto: final t/o speed

;Vimd: minimum drag

;Vimp: minimum power

;Vh: max speed in level flight with max continuous power.

;Vle: max landing gear extended speed

;Vlo: max landing gear operating speed

;Vlof: lift-off speed

;Vmbe: max brake energy speed

;Vmd: minimum drag

;Vmc: minimum control speed with critical engine inoperative

;Vmca: minimum control speed, air

;Vmcg: minimum control speed, ground

;Vmcl: minimum control speed, approach and landing

;Vme: max endurance

;Vmo: max operating limit speed

;Vmp: minimum power

;Vmr: max range

;Vmu: minimum unstick speed

;Vnd: max structural cruising speed

;Vp: aquaplaning speed.

;Vra: rough air speed

;Vref: reference landing speed

;Vs: V-stall

;Vso: stall speed in landing configuration

;Vs1: stall speed in a specified configuration

;Vs1g: one g stall speed

;Vsr: reference stall speed

;Vsse: safe single engine speed

;Vt: threshold speed

;Vtmax: max threshold speed

;Vx: best angle of climb

;Vxe: best angle of climb, single engine

;Vy: best rate of climb

;Vyse: best rate of climb single engine
Speeds indicated on Airspeed Indicator

Airspeed Indicator

V speeds are nearly always given as Indicated Airspeed (IAS), so that pilots can read them directly off the airspeed indicator (ASI). ASIs carry color-coded markings that give the pilot an immediate reference, as follows:
*VS0: bottom of white arc.
*VS: bottom of green arc.
*VFE: top of white arc.
*VNO: top of green and bottom of yellow arcs. The yellow arc is a caution, as speeds in this region may add dangerous stress to the aircraft, and are only to be used in smooth air when no turbulence or abrupt control inputs are expected.
*VNE: red line and top of yellow arc.
*In addition, on a light multi-engine aircraft, VYSE is indicated by a blue line, and VMC is indicated by a red line near the bottom of the green arc.


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