V SPEEDS & DESCRIPTIONS | V SPEEDS - DESCRIPTIONS |
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Speeds frequently used in General Aviation
 Cessna CE150L Airspeed Indicator
VA design maneuvering speed (stalling speed at the maximum legal G-force, and hence the maximum speed at which abrupt, full deflection, control inputs will not cause the aircraft to exceed its G-force limit). Maneuvering speed is limited by aircraft structural characteristics. With the Cirrus SR20 and SR22, this speed is also known as VO VFE maximum flap extended speed (a different maximum speed may be specified for partial flap extension). VLE maximum landing gear extended speed. The maximum speed at which the aircraft may be flown with the landing gear extended. VLE is typically higher than VLO VLO maximum landing gear operating speed. The maximum speed at which the aircraft may be flying while raising or lowering the gear. Although VLO is designated as one speed, in most cases it will have both an extention and retraction speed. Many aircraft can extend the gear at VLE, but (because of possible G-loading in climbout)must retract the gear at a lower speed. For example the Piper Seminole can extend the gear at its VLE of 140 but must be below 109 to retract the gear, thus VLO is read as 109,140 instead of a single airspeed. VMC or VMCA minimum control speed with the critical engine inoperative. The speed below which, control will be lost, normally due to roll or yaw divergence. In initial aircraft type testing and certification, this is tested at a safe height above ground and, when established, is factored in to V2 (which see) that by regulation has a set margin over Vmca and also over Vs. VNE The VNE , or the never exceed speed, of an aircraft is the V speed which refers to the velocity that should never be exceeded due to risk of structural failure, due to calculated factors such as wing or tail deformation or due to aeroelastic 'flutter' (unstable airframe or control oscillation). VNE is specified as a red line on many airspeed indicators. This speed is specific to the aircraft model, and represents the edge of its performance envelope in terms of speed. Well below the speed of sound, the VNE is read as Indicated Air Speed (IAS), since the pitot indication is a direct measure of the dynamic pressure for any given airspeed. At altitude, where TAS is higher than IAS, aerodynamic damping is weaker than at lower levels (damping is proportional to IAS) whereas inertia-induced disturbances are stronger (inertia grows with acceleration, which is the time derivative of TAS). This condition, if continued beyond tested limits, pre-disposes to unstable oscillations or 'flutter'. For instance, the TAS/IAS ratio at 40,000 ft on the ICAO ISA is 2:1, that is, TAS is approximately twice IAS. 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. VNO The VNO of an aircraft is known as the 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 upper limit of the 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 a margin over the stall speed - usually 1.3×VS0. VS the stalling speed or the minimum steady flight speed at which the airplane is controllable. Usually synonymous with VS1. This speed is specific to the aircraft model and depends upon the weight and balance of the aircraft. The true stall speed increases as atmospheric pressure decreases. (I.e. as temperature increases and/or as altitude increases.) The indicated stall speed, i.e. the speed indicated by the airspeed indicator, remains essentially unchanged with air pressure. 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 configuration "clean" 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. VB design speed for maximum gust intensity. VC The VC of an aircraft is the V speed which refers to the velocity of cruising. VC is within the green arc on many airspeed indicators. This speed varies is different for each aircraft model. VC is also called the design cruising speed or the optimum cruise speed – the latter being the speed giving the most velocity (i.e greatest distance/time) from a litre of fuel, usually utilising 75% power at Maximum Take-Off Weight (MTOW) and about 1.3 times the maximum lift-to-drag ratio (L/D) speed – Vbr above. The speed and power required decrease as the aircraft weight decreases from MTOW. For normal category aircraft FAR Part 23 specifies a minimum design cruising speed (in knots) based on the wing loading of (weight in pounds divided by wing area in square feet). For the utility category, the minimum design cruising speed is . Many ultralight aeroplanes are unable to comply with the FAR part 23 requirement for a minimum 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. VWW maximum speed for windshield wiper operation. 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 the minimum safe speed in the second segment of a climb following an engine failure. Also called takeoff screen speed and sometimes, takeoff safety speed, although as the second climb segment indicates, V2 is an after takeoff speed frequently achieved shortly after rotate (Vr) as the aircraft accelerates. The engine failure case that is taken in the calculation of V2 is that of the "most adverse engine" because the effects of different engines when failed, differ. The calculation of V2 also includes set margins over the stall and other safety factors are built in as well. V2min minimum safe speed in the second segment of a climb following an engine failure. 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 Air minimum control speed is the minimum flight speed at which the airplane is directionally controllable as determined in accordance with Federal Aviation Regulations. Airplane certification conditions include one engine becoming inoperative and wind milling, not more than a 5 degree bank towards the operative engine, takeoff power on the operative engine, landing gear up, flaps in takeoff position, and most rearward C of G. 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 Vs0 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
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:
bottom of white arc.
bottom of green arc.
top of white arc.
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.
Red line and top of yellow arc.
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