Glossary - Letter W

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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W |abbreviation| west


WAAS |noun| a US navigation system which processes and improves data from GPS satellites to provide location information. Full form: Wide Area Augmentation System (NOTE: The European equivalent is EGNOS.)


wake turbulence |noun| the disturbance of the air remaining after the passage of an aircraft. For this reason, ATC usually provides additional horizontal separation after the passage of particularly large aircraft. Also called: wake vortex

walk-around inspection |noun| an external check for damage of the aircraft made by the first officer at the stand between two flights

wall |noun| the side / There is a film of oil between the piston and cylinder wall. /

wander |verb| to move or enter unintentionally / The crew was unfamiliar with the airport and wandered onto the active runway. /

warm front |noun| an advancing mass of warm air moving over a mass of cooler air


warn |verb| to give notice of possible danger / A light illuminates to warn the crew. /


warning |noun| notice of possible danger - |adjective| giving notice of possible danger / The main power plant fire detection system should contain an audible warning device to supplement the visual indication. /


warning indicator |noun| an indicator which gives notice of a possible problem which may require some action.


warning light |noun| a small light, often red, which informs of a possible danger by lighting up / At 5 knots above stalling speed, a warning light on the instrument panel will flash. /


washroom |noun| same as toilet


waste |noun| something which can no longer be used / A smouldering fire in a toilet waste container or waste disposal bin could become very active due to pressure changes during descent. /

water service vehicle |noun| a truck for replenishing aircraft’s potable water supply

water-tight |adjective| that does not leak water or other fluid


watt |noun| the SI unit of measurement of electrical power / The work done by an electrical circuit or the power consumed is measured in watts. /


wave |noun|  1. the motion by which heat, light, sound or electric current is spread / The speed of propagation of radio waves is faster over sea than over land. /  2. a mass of water moving across the surface of a lake or the sea, rising higher than the surrounding water as it moves / Wind speeds increase with height, the speed of the wind at the crest of a wave being the greatest. /


waveform |noun| the shape of a repetitive wave / A cycle is one complete sequence of the waveform, from any point, to the same value 360° later. /


wavelength |noun| the distance from the highest point of one wave to the highest point of the next / Short wavelength permits sharper beams for direction finding and more efficient reflections. /


wave-off |noun| a signal or instruction to an aircraft that it should not land


way-point |noun| a predetermined position on a route, used for monitoring flight progress or for navigating around controlled airspace. Abbreviation: WP


weak |adjective|  1. not strong / a weak radio signal /  2. over-diluted with water or air - weak mixture > a fuel/air mixture in which there is more air than usual / Excessive cylinder head temperatures could be caused by prolonged use of a weak mixture, especially at high altitude. / - weak solution > a mixture of water and some other substance in which the amount of water is more than usual


weaken |verb| to make weak / Inflation of the deicer boot weakens the bond between the ice and deicer boot surfaces. /


wear |noun| damage or loss of quality by use / Mishandling of aero-engines during operation can cause considerable damage and wear which can shorten the life of the engine. / - |verb|  1. to become damaged or to lose quality because of use / The more the brakes are used, the more they wear. /  2. to have on the body / The nature of modern jet transport does not require the pilot to wear an oxygen mask. /


weather |noun| the conditions of atmospheric temperature, pressure, wind, moisture, cloudiness, precipitation and visibility / Generally speaking, weather conditions can be described as light, moderate or severe depending on the intensity of the conditions. / - forecast weather > predicted weather, not actual weather

weather bureau |noun| a station gathering and distributing updated weather reports and forecasts. Also called: met office.

weathercock |verb| to tend to turn in the direction of the wind

weather radar returns |noun| the colored patterns or outlines from the weather radar antenna displayed on the cockpit ND. Aircraft are fitted with weather radar systems using a radar antenna in the radome covering a range of up to several hundred miles. Crews use the color-coded displays provided by this system to detect the presence of weather systems (cumulonimbus clouds, thunderstorms and resulting turbulence) in order to request a change of flight path if necessary.

weather report |noun| an official account of weather conditions


web |noun| the main vertical member of a beam / The web connecting the upper and lower flanges of the beams must be rigid enough to withstand direct compressive loads without buckling. /


weigh |verb| to measure how heavy something is / A given quantity of lead weighs more than the same quantity of aluminum. /


weight |noun| the force with which a body is drawn towards the center of the Earth / Carry-on baggage is limited by regulations as to size and weight and items in excess of this should be stowed in the hold. /

weight and balance print-out |noun| a document recording distribution of weight and CG (center of gravity) at take-off; also referred to as the weight and balance sheet

weight and balance sheet |noun| a document recording and allowing the checking of the aircraft weight, load distribution and center of gravity

west |noun|  1. a compass point on the mariner’s compass 270° clockwise from due north and directly opposite east / In Europe, snow occurs more frequently in the east than in the west. /  2. the direction of the setting sun - |adjective|  1. referring to areas or regions lying in the west  2. the western part of a country / West Africa / - |adverb| towards the west / The aircraft was flying west. /


westbound |adjective| traveling towards the west / a westbound flight /


westerly |adjective|  1. situated towards the west  2. blowing or coming from the west / A westerly wind is blowing. /  3. moving to the west or towards the west / He should fly in a westerly direction. / - |noun| a wind which blows or comes from the west / Temperate westerlies occur on the side of the sub-tropical anti-cyclonic belts which is remote from the equator. /


western |adjective| situated in the west / Western Europe /


westward |adjective| going towards the west - |adverb| US same as westwards


westwards |adverb| towards the west / Flying eastwards or westwards for long periods of time affects sleep patterns. /


west wind |noun| a wind blowing from or coming from the west (NOTE: A wind is named after the direction it comes from.)


wheel |noun| a circular, rotating, load-carrying part between the tire and axle, or the whole wheel and tire assembly on which a vehicle rolls


wheel bay |noun| a space in the fuselage or wing structure in which the wheel is housed after retraction / To avoid damage to the wheel bay, the nose wheel must be aligned in a fore and aft direction during retraction. /


wheel bearing |noun| a device which allows the wheel to rotate freely around the axle

wheelchair |noun| a light chair with wheels for invalids

wheel fairing |noun| same as spat


wheels up |adjective| airborne after having taken off from a runway


whereas |conjunction| but in contrast, on the other hand / In the piston engine, the cycle is intermittent, whereas in the gas turbine, each process is continuous. Kerosene has a low vapor pressure and boils only at very high altitudes or high temperatures, whereas a wide-cut fuel will boil at a much lower altitude. /


whereby |adverb| according to which / Compression heating relies on the principle whereby the air temperature is increased by compression. In ram air supply systems, the cooling method is of the simplest type, whereby the cold air can be directly admitted to the cabin via adjustable louvres. /


whereupon |adverb| at that point, or after which / Pitch changes are achieved using the throttle lever, which is usually taken up and back through a gate in the quadrant whereupon fuel is added to increase power. /


wherever |adverb| - wherever possible > in places where it is possible - wherever possible, thunderstorms should be avoided by a wide margin > thunderstorms should be avoided by a wide margin in situations or places where it is possible to avoid them


while |conjunction|  1. during the time that / The pilot is trained to scan an instrument panel, while at the same time listening to the aircraft radio and flying the aircraft. /  2. in spite of the fact that / While metal fatigue is not a modern phenomenon, it is only in recent years that much emphasis has been placed upon determining its causes. / (NOTE: Whilst is sometimes used in place of while.)


whip-stall |noun| a maneuver in a small aircraft in which it goes into a vertical climb, pauses briefly, and then drops towards the earth, front first

whiteout |noun| the phenomenon of spatial disorientation caused by the intense glare of a snowy landscape

whole |adjective| complete / The whole aircraft should be inspected to ensure that it is free from deposits of ice, snow and frost. / - whole number > an undivided number, a number which is not a fraction

wick |noun| a static discharger located on trailing edges to discharge electrical charges built up in the airframe

wide |adjective|  1. referring to the distance of something measured from side to side / The localiser antenna array is normally about 80 feet wide and 12 feet high. /  2. - a wide range of temperatures > a large difference between the lowest and the highest temperature - a wide variety of information > a lot of different information. 


Wide Area Augmentation System |noun| full form of WAAS


wide-bodied |adjective| US same as wide-body


wide-body |noun| a jet aircraft with a body wide enough to accommodate three rows of seats across the width of the plane, with spaces on each side of the middle set


wide-body |adjective| referring to a jet aircraft with a body wide enough to have three sets of passenger seats in a row across the width of the plane, with spaces on each side of the middle set


wide-cut fuel |noun| a general term for aviation turbine fuels made up of a wider variety of petroleum products than kerosene-type fuels / Kerosene has a low vapor pressure and boils only at very high altitudes or high temperatures, whereas a wide-cut fuel will boil at a much lower altitude. /


widespread |adjective| found or distributed across a large area / The storm caused widespread damage. / - widespread precipitation > rainfall or snowfall covering a large area


width |noun| the distance of something measured from side to side, compared to length / The polar front jet stream may have a width of up to 200nm (nautical miles). /


wind (1) |noun| horizontal movement of air in relation to the Earth’s surface


wind (2) |verb| to move in a curving or twisting manner / If a wire is wound as a coil, the field will be like that of a bar magnet. / (NOTE: winding – wound)


wind-blast |noun| the harmful effect of air flow on a pilot who has ejected from an aircraft traveling at high speed


wind cone |noun| same as windsock


wind currents |plural noun| the movement of air in a particular direction through a mass of air which is not moving so much


wind direction |noun| a description of where the wind is blowing from, given as north, south, east, west, etc., or a number of degrees, e.g. a wind coming from the west would be a wind direction of 270° / Wind direction and speed only affect the movement of the aircraft over the ground. /


wind gradient |noun| the rate of increase of wind strength with unit increase in height above ground level /After take-off, as the aircraft gains altitude, the ground speed may be affected by the wind gradient./


winding |noun| a series of 360° turns of wire / The voltage in each winding is directly proportional to the number of turns in each winding. /


windmill |verb| to turn round by wind force only without engine power

window heat |noun| the electrical resistances in the windshield and side cockpit window panels which prevent the formation of ice and condensation

windscreen |noun| the front window of an aircraft through which the pilot has forward vision / The windscreen is a glass laminated construction with an electrical element, made of gold film, sandwiched between the layers. /


wind-shear |noun| a change in wind direction and speed between slightly different altitudes / Wind-shear, if strong enough, can produce clear air turbulence. Fly-by-wire technology can be very useful in wind-shear situations. /


windshield |noun| US same as windscreen


windsock |noun| a pole at the top of which is a fabric tube through which the wind blows, showing the wind direction


wind-speed |noun| the speed of the wind which, if combined with a direction, is called velocity. It is usually measured in knots. / Wind direction is given in degrees true rounded to the nearest 10°, followed by the mean wind-speed. /


wind tunnel |noun| a tunnel-shaped chamber through which air can be passed at a known speed in order to test the aerodynamic properties of an object such as an aircraft placed inside it


wind velocity |noun| wind speed and direction


windward |adjective|, |adverb| facing the direction from which the wind blows. Opposite: lee - windward of a range of hills > upwind of the range of hills / If precipitation occurs, water will have been removed from the atmosphere thus causing the air on the lee side to be drier than that on the windward side. /


wing |noun| the main horizontal airfoil or main-plane / The wing supports the weight of the aircraft in flight. /


winglet |noun| an upturned wing tip or small additional vertical airfoil on a wing tip / The attachment of winglets improved the handling characteristics of the airplane. /


wing loading |noun| the weight of an aircraft per unit wing area


wing-man |noun| a pilot who flies in a position behind and to the side of the leader of a group of flying aircraft


wing-over |noun| a maneuver to turn a flying aircraft in which the pilot puts the aircraft into a steep turning climb until it almost stalls and then allows the nose to fall


wing panel |noun| a rectangular aluminum section of the aircraft skin of a wing / Wing panels of light aircraft are normally riveted together. /


wing root |noun| the part of the wing where it meets with the fuselage


wingspan |noun| a measurement from the tip of one wing to the tip of the other wing / The wingspan of the aircraft is 7 meters. /


wing tip |noun| the outer-most part of the wing / As an aircraft takes off, the forces on the wing tip and wing surfaces start reversing direction and instead of being only downward forces of weight, they become upward forces of lift. /


wipe |verb| to clean or to dry by using a cloth / In the event of hydraulic fluid spillage on paintwork, the affected area should be wiped clean immediately. /


wiper |noun| a device with a rubber blade which clears rain, snow, etc., from a windscreen / In some circumstances, such as heavy rainstorms, the windscreen wipers may not be able to cope and pilot’s visibility is impaired. /


wire |noun| metal drawn out into the form of a thread or string / While the shunt coil is made of fine wire which gives a high resistance and small current flow, the series coil is made of thick wire, which gives a low resistance and large current flow. /


wire mesh |noun| metal sheeting made of crisscrossed wiring


withdraw |verb| to pull back, to draw back / Instructions are given to the cabin crew to arm the escape devices immediately the boarding steps or air-bridges are withdrawn. / (NOTE: withdrew – withdrawn)


within |preposition| in or inside / Great care must be taken to ensure that the aircraft operates within regulated or permissible weight limits. / - within two hours > in about two hours or less, but not more


withstand |verb| to resist or bear / Wings must be capable of not only withstanding the aircraft weight, but also the stresses and strains which are imposed during flight. /


WMO |abbreviation| World Meteorological Organization


work |noun|  1. the operation of a force to produce movement or some other physical change / 1 horsepower is defined as 33,000 foot-pounds of work accomplished in one minute (a foot-pound being the ability to lift a one pound weight a distance of one foot). /  2. something which has to be done, e.g. maintenance / Work is being carried out on the auxiliary power unit (APU). /  3. something done to earn a living / She enjoys her work as an airport security officer. / - |verb|  1. to operate, to function - the computer doesn’t work > the computer doesn’t operate as it should do because there is something wrong with it  2. to do something such as maintenance / Engineers worked on the aircraft all night. /  3. to do something to earn a living / She works for a large airline. /  4. - to work out > to calculate, to solve a mathematical problem / Aircraft performance is a function of weight and therefore it is important that you can work out weight from volume and vice-versa. /


working conditions |plural noun| those aspects of working lives which affect the way people feel about their work


work load |noun| the share of work done by a person, system or device

WP |abbreviation| way-point

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