Vs – Stalls speed; speed at which a/c stalls (can no longer support the weight of the a/c)
Vms – minimum speed that can be maintained in the stalling maneuver, speed at which a/c can still fly level.
Vs1– max zero thrust stall speed at given flaps setting.
Vs0 – max zero thrust stall speed at full flaps position.
V1 – Decision speed at which initiation is made either to carry out an rejection/ abort of take off or to continue the take off in the event of critical engine (engine whose failure causes max asymmetric thrust) failure.
Min limits of V1 is Vmcg, max limit is Vr & subject to Vmbe (Brake energy limit).
Vr – rotation speed, speed at which a/c is rotated at a specified rate of rotation (with limitation due to higher rotation causing tail contacting the runway), for a/c to become airborne.
Min limits of Vr are 1.o5 Vmcg & 1.10 of Vs, max limit is V2.
V2min – minimum take off safety speed.
V2 – take off safety speed, minimum speed at which a/c demonstrates positive response to control inputs with specified safety margins, associated with initial climb to a safe altitude after take off following the critical engine failure.
Min limits of V2 are 1.10 of Vmcg & 1.20 of Vs, max limit is subjected to Tyre speed limitation.
V3 – all engines screen speed, speed at which flaps can be retracted, when a/c is assumed to reach the ht of 35 feet at the end of runway or clearway if available (also called Screen height) with all engines operating normal on take off.
V4 – all engines steady initial climb speed, speed that a/c is expected to achieve with all engines operative, for the purpose of first segment in noise abatement procedures.
Vf/Vfri – flap retraction speed, minimum speed that must be achieved before the flaps are retracted at a safe altitude.
Vzf – speed below which the turns are limited to 15* angle of bank, when the flaps are retracted,
This is an important speed for a departure that requires a/c to execute a significant maneuver after take off, or in the earlier stages of climb, in this case, flaps retraction will be delayed until this speed is attained.
Vat – Threshold speed the speed which must be reached at a height of 50 feet above the threshold, with a/c in landing configuration, to meet the manufacturers predicted landing performance.
Vat – same as Threshold speed with max flaps setting.
Vat1 – Threshold speed for one engine out landing.
Vat2 – Threshold speed for two engines out landing.
VT max – Threshold maximum speed, speed above which a/c has potential danger of overrunning the runway.
Vmu – minimum demonstrated unstick speed, minimum speed at which it is possible to leave the ground, & have positive control response with all engines operating in specified a/c configuration.
Vmc – minimum calibrated air speed at which it is possible to control a/c if critical engine fails.
Vmcg – minimum calibrated air speed at which it is possible to maintain directional control of the a/c with safety margins & remain on the runway if critical engine fails on take off run, with the following conditions-
- Using rudder controls only.
- Rudder force upto 150 lbs.
- 7 kts crosswind from inoperative engine side.
- Max power on live engine.
- Landing gear extended.
Vmca – minimum calibrated air speed at which it is possible to lift off the a/c with safety margins if critical engine fails on take off run, with the following conditions-
- Using rudder controls with force upto 150 lbs only.
- Bank angle upto 5°
- Directional change upto 20°
- Max power on live engine.
- A/c airborne & no ground effect.
Vmcl – minimum control speed in the air in an approach or landing configuration, to maintain positive control of the a/c with maximum asymmetric thrust.
Vlo – maximum speed for the operation of the landing gear, either extending or retracting.
Vle – maximum speed at which an a/c can fly with the landing gear extended.
Vno/Mno – maximum operating limited speed for normal operations.
Vne/Mne – never exceed speed, max speed that can be sustained by the a/c, restricted mostly due to airframe stress.
Vmo/Mno – maximum speed for all operations.
Vd – design dive speed. It is the maximum speed that can be attained in a dive.
Vdf/Mdf – maximum demonstrated terminal velocity speed, max speed that can be achieved in a dive.
(Terminal velocity- maximum speed that can be achieved by an a/c in a near vertical dive).
Va/Vman – maneuvering speed, maximum speed at which the controls can be fully deflected, without causing the airframe overstress.
Vra/Mra – rough air penetration speed, a range of speed that can be safely flown with positive control responses and causing no airframe stress when a/c experiences turbulence conditions.
Vb – design speed for maximum Gust intensity/Turbulence penetration.
Vbg – best gradient climb speed.
Vx – best angle of climb speed, speed that gives max gain in height with relation to distance traveled over the ground.
Vy – best rate of climb speed, speed that gives max gain in height with relation to time.
Vxse – best Single Engine Angle of Climb speed, speed that gives max gain in height with relation to distance traveled over the ground, when operating with Critical Engine failed in a Multi Engine Aircraft.
Vyse – (Blue Radial) best Single Engine Rate of Climb speed, speed that gives max gain in height with relation to time, when operating with Critical Engine failed in a Multi Engine Aircraft.
Vc – design cruising speed. This speed should not be exceeded in normal cruising flight conditions, since possible encounter of turbulence above this speed can cause Airframe stress limitation to be exceeded.
Vfe – (End of White Arc) max speed with flaps extended.
Vimd – minimum drag speed.
Vimp – minimum power operations speed.
Vfc/Vmc – maximum speed concerning a/c stability characteristics, All the a/c demonstrates at least neutral static stable characteristics, when flown with in the specified ranges of Vfc/Vmc.
Vh – maximum speed in cruise flight with specified power settings.
Vllo – maximum landing light operation speed, this speed is limited to a/c with landing light located at nose wheel sections.
Vlof – a/c lift off speed, usually more than rotation speed.
Vref – speed at which threshold should be crossed at a height of approx 50 feet, usually 1.30 of Vso (landing configuration)
Vapp – approach speed with safety margins accounted for the existing conditions due to a/c configuration & weather conditions.
Vapp = Vref + Headwind component + Gust (Max of 15 knots).
V18 – Engine Failure speed for Balance Field length, This is the speed at which if a critical engine fails, the distance to continue the Take off to a Screen Height or to reject the Take off and bring the A/c to a complete stop with in the Runway is same under Zero Runway slope and Nil wind conditions.
Vei/Ven – is the maximum speed at which A/c configuration like flaps, landing gear operations can be used.