Glossary - Letter V

If you wish to find a term by name, please click the relevant letter below to be taken to a list.


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V1 speed |noun| the decision speed, i.e. the speed at which the pilot must decide to continue or abandon take-off

vacate |verb| to exit or leave the runway / Speedbird 48G report runway vacated. /

vacuum |noun| a space completely empty of everything including air / If the fuel tank vent pipe is blocked, a vacuum will form in the tank and fuel flow to the engine will be restricted. /


valid |adjective|  1. having official force or effect / All passengers should have valid passports. /  2. worth taking seriously, acceptable because it is true or well-based / Significant weather charts use abbreviations and symbols to illustrate en route weather phenomena and are valid for a specified time. / - a valid assumption > a well-based supposition


validity |noun| the state of being valid / Aerodrome forecasts included in VOLMET should have a validity period of 9 hours. /


valley |noun| an area of low-lying land between mountains or hills / An example of a valley wind is the Mistral. /


value |noun|  1. a quantity shown as a number / Deviation is not a constant value but varies from one aircraft to another. /  2. the quality of being useful or desirable - the value of doing something > the usefulness or worth of doing something


valve |noun| a mechanical device for controlling the flow of a fluid


valve overlap |noun| the period when both the exhaust and inlet valves are open together, with the exhaust valve closing and the inlet valve opening


valve seat |noun| an angled ring in the cylinder head on which the poppet valve sits when closed


vane |noun| a flat surface acted on by the wind or an airflow / A centrifugal compressor consists of a disc on which is formed a number of radially spaced vanes. /


vapor |noun| US same as vapour


vaporize |verb| to turn into vapor / Water vaporizes when heated. /


vapour |noun| the gaseous form of a liquid / Over desert areas, the lack of water vapor in the atmosphere produces cold nights. / (NOTE: It is also written vapor in US English.)


vapor lock |noun| a blockage of fuel flow from a tank caused by a bubble of vapor at a high point in the pipeline


vapor trail |noun| a visible trail of condensed vapor left behind by an aircraft flying at high altitude


variable |adjective| changing or changeable / Winds are more variable in the northern hemisphere than in the southern hemisphere. /


variable geometry |noun| technology which allows the angle between wing and fuselage to be altered to give a more or less swept wing for better high-speed and low-speed flight characteristics


variable-geometry |adjective| referring to an aircraft with hinged wings that can move backwards or forwards during flight (NOTE: The wings are swept back to give low drag in supersonic flight and are moved forwards for takeoff and landing.)


variable pitch propeller |noun| a propeller with a mechanism to change the blade angle, to suit flight conditions


variable-sweep |adjective| same as variable-geometry


variation |noun|  1. a change or the amount of a change  2. the angular difference between magnetic north and true north, which is measured in degrees and is named east or west according to whether the north-seeking end of a freely suspended magnet lies to the east or to the west of the true meridian at that point - variation east, magnetic least: variation west, magnetic best > a mnemonic to help somebody remember whether to add or subtract variation


variety |noun| a lot of different things / Display units provide a wide variety of information relevant to engine and other automated systems operation. /


variometer |noun| an instrument used for measuring the rate of climb of an aircraft such as a glider


vary |verb| to change, to be different / The tropopause over the UK can vary between 25,000 feet and 45,000 feet according to whether the country is covered by a polar or tropical air mass. /


VASI |abbreviation| visual approach slope indicator


vast |adjective| large, immense, huge - the vast majority > most / the vast majority of people /


VCR |abbreviation| visual control room


VDF |abbreviation| very high frequency direction-finding


vector |noun|  1. a quantity with magnitude and direction indicated by a line of a given length, representing magnitude and specific direction / The triangle of velocities is a vector solution of what happens to an aircraft when wind causes drift. /  2. a heading given to a pilot to provide navigational guidance by radar / Wind velocity is indicated by a vector, identified by a single arrow, pointing in the direction the wind is blowing towards. /

vectoring |verb| issuing headings to aircraft to provide navigational guidance

vectoring ILS approach |noun| an approach that involves the controller using radar to instruct the pilot about the headings and altitudes to fly to capture the ILS glide-path.

veer |noun| the shifting of the wind in a clockwise direction in the northern hemisphere / The passing of a weather trough is marked by a sharp veer in the direction of the wind. / - |verb|  1. to change in a clockwise direction in the northern hemisphere / Winds veer and increase with height ahead of a warm front. / Opposite: back  2. to change direction, especially as in an uncontrolled movement / The aircraft veered off the runway into the grass. /


velocity |noun| the rate of change of position in a given direction which is composed of both speed and direction / The anemograph gives a continuous recording of wind velocity which is displayed on a chart and reveals gusts, squalls and lulls. /


vent |noun| a hole serving as an inlet or outlet for a fluid, usually a gas such as air / During the pre-flight inspection, check that the fuel tank vent pipe is not blocked. The vent / pressurization system must allow for the passage of air whenever a fuel tank is refueled or defueled or the aircraft climbs or descends. /


ventilate |verb| to cause air to pass in and out freely /The water separator is installed downstream of the cold air unit to extract a percentage of free moisture from the air, which subsequently ventilates and pressurizes the cabin./


ventilation |noun| free circulation of air in and out / A constant supply of air for ventilation purposes is always available from the air conditioning system. /


venturi, venturi tube |noun| a tube which narrows at the center, a choke tube / When the temperature of the air passing through the carburetor is reduced below O°C (Celsius), any moisture in the air forms into ice and builds up on the venturi and throttle valve. /


verification |noun| an act or instance of establishing the truth or validity of something / The document required verification. /


versus |preposition| against, as compared with / The diagram illustrates typical strength properties by plotting applied stress versus resulting strain. /


vertical |adjective| at right angles to the Earth’s surface or to another line or plane / Beams can be additionally stiffened in a downward direction by vertical and diagonal members. Height is defined as the vertical distance of a level, point or object, considered to be a point, from a specified datum. / - |noun| a vertical line or plane / The hot rod ice detector head consists of an aluminum alloy oblong base on which is mounted a steel tube detector mast, angled back to approximately 30° from the vertical. /


vertical axis |noun|  1. an imaginary line running through the fuselage at the center of gravity from top to bottom, around which the aircraft rotates when it yaws / The rudder is a control surface on the fin which rotates the aircraft about its vertical axis to produce yaw. /  2. a vertical reference line (Y axis ) of a graph / The vertical axis shows engine power available. /


vertically |adverb| in a vertical position / The aircraft pitched up vertically. /

vertical separation |noun| the vertical distance between two aircraft, which is measured in feet, but in meters / kilometers in Russia, China and the CIS

vertical speed indicator |noun| a flight instrument which indicates the rate of climb and descent. Abbreviation: VSI

vertical speed mode |noun| the basic pitch autopilot mode. Abbreviation V/S

vertical stabilizer |noun| same as fin


very high frequency, very high frequency band |noun| the radio frequency range between 30 MHz and 300 MHz. Abbreviation: VHF


very high frequency omni-directional radio range |noun| full form of VOR


vessel |noun| a boat or ship / When flying over the sea you must not fly closer than 500 feet to a vessel. /


VFR |abbreviation| visual flight rules

VFR traffic |noun| a flight following Visual Flight Rules, i.e. in this case, making an approach using visual references rather than flying on the instruments (IFR) making an ILS approach

VHF |abbreviation| very high frequency


via |preposition| by way of / The flight is from Cairo to Paris via Rome. After heating, the air passes into the cabin via a chamber through which cold air also flows. /


vibrate |verb| to move rapidly and continuously backwards and forwards / Turbine blades in the average jet engine vibrate at frequencies of 1 million per minute. /


vibration |noun| a rapid and continuous movement / According to the pilot, engine vibration was detected in engine number one. /


vice versa |adjective| the other way around - when engine demand is high, fuel pressure tends to be low and vice versa > when the engine demand is low, fuel pressure tends to be high


vicinity |noun| the area nearby / After an emergency evacuation, passengers should be directed to move away from the vicinity of the aircraft quickly. / - in the vicinity of the airport > near the airport


view |noun|  1. what you are able to see from a particular place / Cabin crew must have a clear view of the aisles from their stations. /  2. a picture of something presented in a particular way / a cross-sectional view of an airfoil /  3. a personal opinion / He expressed strong views on the subject of airport security. /  4. - with a view to > with the intention of / She wrote the report with a view to improving in-flight services. / - in view of > because of / In view of the poor weather conditions, the flight will be delayed. /


violate |verb|  1. to enter without permission / The aircraft violated a danger area. /  2. to break rules or regulations / By not wearing a cap, the cadet is violating the dress code. /


violent |adjective| with great force / Flying through atmospheric dust causes the airframe to build up a static electrical charge and the associated discharges can be violent. /


VIP |abbreviation| very important person


virtually |adverb| almost / Resistance to alternating current remains virtually constant and is independent of frequency. /


viscosity |noun| a liquid’s internal resistance to flowing / Excessive oil temperatures are dangerous, as the oil viscosity is reduced and inadequate bearing lubrication results. /


visibility |noun| the ability to see unlighted objects by day and lighted objects by night, subject to atmospheric conditions / Measurement of visibility by day is made by direct observation of objects at known distances and is therefore an estimated value. / - poor visibility > a situation in which things cannot be seen clearly, e.g. because of fog, mist or smoke


visibility-by-day values |noun| values which indicate how easily seen an object is in a horizontal line from an observer in daylight conditions


visible |adjective| that can be seen / When the undercarriage is selected down it may be visible from the crew compartment, but it is not usually possible to tell if it is securely locked. If the sun is seen through cumulus cloud it will be clearly visible. /


vision |noun|  1. the power of seeing, the ability to see / Lightning at night may cause temporary loss of vision. /  2. what you are able to see / In low wing aircraft, downward vision may be limited by the airframe. /


visual |adjective| referring to seeing / The instrument landing system is to provide guidance in the horizontal and vertical planes to an aircraft on final approach into a position from which a safe visual landing can be made. /

visual approach |noun| an approach to a given runway where the pilot relies on visual references such as VASI (Visual Approach Slope Indicator), PAPI (Precision Approach Path Indicator) and topography rather than using the Instrument Landing System

visual approach slope indicator |noun| an arrangement of red and white lights on each side of the runway touchdown point to give the pilot information about the plane’s height on final approach. Abbreviation: VASI

visual contact |noun| visual observation; the expression ‘We are visual’ is also used

visual control room |noun| the control room in the tower at an airport. Abbreviation: VCR


visual examination |noun| a close observation or inspection with the eyes. Also called: visual inspection


visual flight rules |plural noun| rules set down by an authority for flight in visual conditions, regarding such things as flight visibility and distance from cloud. Abbreviation: VFR. / special VFR flight / (NOTE: Particular requirements for VFR depend on the type of airspace, time of day, and height above terrain.)


visual indication |noun| something which is seen and which suggests a more serious cause, e.g. a warning lamp / Distorted wing panels are often a visual indication of structural damage to the airframe. /


visual meteorological conditions, visual meteorological conditions criteria |plural noun| all the factors which define the limits of flying in visual meteorological conditions. Abbreviation: VMC

visual references |noun| topographical features, markings and lights which contribute to situational awareness. Also called: visual cues

visual separation |noun| the separation between two aircraft based on the pilots’ visual contact rather than a distance imposed by ATC

visual warning |noun| a warning that can be seen as opposed to a audible warning that can be heard


vital |adjective| extremely important / Verbal commands from the crew are vital at all times but particularly so if smoke restricts cabin visibility. Accurate measurements of atmospheric pressure and the rate of change of pressure are of vital interest to the meteorological forecaster. /


viz |adverb| namely, in other words, that is to say / There are two types of inverter, viz rotary and static. /


VMC |abbreviation| visual meteorological conditions


Vne |abbreviation| never-exceed speed


volatile |adjective| describes a liquid which easily changes into a gas or vapor / To aid starting in cold weather, more volatile fuels can be used /


volatility |noun| the ease with which a liquid changes into a gas or vapor / With kerosene-type fuels, the volatility is controlled by distillation and flash point, but with the wide-cut fuels it is controlled by distillation and the Reid Vapor Pressure test. /


VOLMET |noun| a routine ground-to-air broadcast of meteorological information / The Meteorological Operational Telecommunications Network Europe (MOTNE) is provided for the exchange of meteorological information needed by meteorological offices, VOLMET broadcasting stations, air traffic service units, operators and other aeronautical users. /


vol-plane |noun| a glide towards the ground in an aircraft with the engine turned off - |verb| to glide towards the ground in an airplane with the engine turned off


volt |noun| the SI unit of electrical potential / The system requires a power supply of either 115 volts AC (alternating current), 28 volts DC (direct current), or both. / Abbreviation: V


voltage |noun| electrical force measured in volts / As an installed battery becomes fully charged by the aircraft generator, the battery voltage nears its nominal level and the charging current decreases. /


volume |noun|  1. the amount of space occupied by a solid, a liquid or a gas / If the pressure of a given mass of gas is maintained constant, the volume of gas increases as its temperature is increased. /  2. the loudness of a transmission - turn down the volume > to make the sound less loud by adjusting the volume control


volume control |noun| a knob used to adjust the sound by making it louder or less loud


VOR |noun| a navigational aid based on the ground, to help the pilot establish the bearings of the aircraft. Full form: very high frequency omni-directional radio range (NOTE: The VOR projects 360 radials which can be followed to fly a particular path over the ground. VORs operate on VHF frequencies between 108.0 to 177.95 MHz.)


VOR bearing |noun| the direction of the VOR transmitter relative to the aircraft measured in degrees

VOR calibration |noun| a periodic checking and resetting of VOR transmitters

VOR-DME approach |noun| an approach using a combination of two types of navaid: VHF Omnidirectional Range and Distance Measuring Equipment

VORTAC |noun| a system that combines VOR and Tacan

Vref |noun| the speed or velocity at which the aircraft should be flying in a given configuration

VSI |abbreviation| vertical speed indicator


V/STOL |noun|  1. a system used by some aircraft that allows them to take off and land vertically or on a short runway  2. an aircraft that is able to take off and land vertically or on a short runway. Full form: vertical and short takeoff and landing


VTOL |noun| 1. a system used by some aircraft that allows them to take off and land vertically  2. an aircraft that is able to take off and land vertically. Full form: vertical takeoff and landing

vulnerable |adjective| unprotected and liable to attack or damage / Some engines still retain the centrifugal type of compressor because it is simple, comparatively cheap to manufacture, robust in construction and less vulnerable to damage. /

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