aviation glossary


V speeds - designations for certain velocities relating to aircraft operation, thus:

  • V1 - decision speed, up to which it should be possible to abort a take-off and stop safely within the remaining runway length. After reaching V1 the take-off must be continued.

  • Va - design manoeuvring speed. The speed below which abrupt and extreme control movements are possible (though not advised) without exceeding the airframe's limiting load factors.

  • Vfe - maximum flap extension speed (top of white arc on ASI).

  • Vmca - minimum control speed (air). The minimum speed at which control of a twin-engined aircraft can be maintained after failure of one engine.

  • Vmo - maximum operating speed. Also Mmo, Mach limit maximum operating speed.

  • Vne - never-exceed speed, 'redline speed' denoted by a red radial on an ASI.

  • Vno - normal operating speed. The maximum structural cruising speed allowable for normal operating conditions (top of green arc on ASI).

  • Vr - rotation speed, at which to raise the nose for take-off. Vso stalling speed at MTWA, in landing configuration with flaps and landing gear down, at sea level,

  • Vx - best angle of climb speed on all engines.

  • Vxse - best engine-out angle of climb speed.

  • Vy - best rate of climb speed on all engines.

  • Vyse - best engine-out rate of climb speed, 'blueline speed' (blue radial on ASIs of light twins)

VAL - design manoeuvring speed. The speed below which abrupt and extreme control movements are possible (though not advised) without exceeding the airframe's limiting load factors.

VAL - visual approach and landing chart.

var - variation (magnetic)

VASIS - visual approach slope indicator system. A coloured light system providing visual guidance to the glidepath of a runway.

VDF - very-high frequency direction-finding, whereby an aircraft's bearing from a ground receiving station may be determined from its RT transmissions.

vdu - visual display unit.

VFR - Visual Flight Rules. Prescribed for the operation of aircraft in visual meteorological  conditions (VMC).VMC is generally defined as five miles visibility or more and 1,000 feet vertical and one nautical mile horizontal clearance from cloud, but variations apply to aircraft operating below 3,000 feet amsl. Special VFR (SVFR) clearances are granted at the discretion of ATC for VFR flight through some controlled airspace where IFR usually apply. Also CVFR, Controlled VFR Flight.

VHF - very high frequency. Radio frequencies in the 30-300 MHz band, used for most civil air-to-ground communication.

vis - visibility.

VLF - very low frequency. Radio frequencies in the 3-30 kHz band

VLF/Omega - worldwide system of long-range navigation using VLF radio transmission.

VMC - Visual Meterorological Conditions. See VFR, above.

Vnav - vertical navigation.

Volmet - continuous recorded broadcasts of weather conditions at selected airfields.

VOR - very high frequency omnidirectional range. A radio navigation aid operating in the 108-118 MHz band. A VOR ground station transmits a two-phase directional signal through 360. the aircraft's VOR receiver enables a pilot to identify his radial or bearing from/to the ground station. VOR is the most commonly used radio navigation aid in private flying. Increased accuracy is available in Doppler VORs (DVOR) which have replaced some VOR is the UK system. Also VORTAC, combined VOR and TACAN, and VOT, VOR test facility.

VP - variable-pitch (propeller), whose blade angle can be altered in flight either automatically
or manually.

VRP - visual reference point. (In the UK) Landmarks used for position reporting by aircraft
operating VFR.

VSI - vertical speed indicator. One of the primary flight instruments showing rate of climb or descent. Also IVSI, instantaneous VSI.