diffraction /d.frk.(.)n/ noun the breaking down of a beam of radiation .
Diffraction produces a surface wave which follows the curvature of the earth.
diffuse /d.fjus/ adjective spread out in every direction . Glare caused by dif-fuse reflection of sunlight from the top of a layer of fog or haze can seriously reduce air-to-ground visibility. . verb to spread out in every direction . Light dif-fuses as it passes through fog.
diffuser /d.fjuz./ noun a device in a jet engine that alters the direction of flow of the air entering the engine as part of the process of compressing it before it reaches the combustion cham-ber
diffusion /d.fju(.)n/ noun the process of spreading out . Gas from the turbine enters the exhaust system at high velocities but, because of high fric-
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tion losses, the speed of flow is decreased by diffusion.
digit /d.d.t/ noun any number from 0 to 9 . Information is provided in a four-digit group.
digital /d.d.t(.)l/ adjective referring to a system or device which uses signals or information in the form of numbers
dihedral /da.hedr(.)l/ noun the angle between an upward sloping air-craft wing and a horizontal line
diluted /da.lut.d/ adjective made
weaker by adding water or some other fluid . Spillage from a lead acid battery may be neutralised by washing with a diluted solution of sodium bicarbonate.
diluter /da.lut./ noun a device for decreasing the strength or concentration of a liquid or gas . Most flight decks use the diluter demand system in which the oxygen is diluted with cabin air.
dimension /da.men..n/ noun a
measurable distance such as height, length, etc., or a measurement of height, length, etc. . Variations of atmospheric pressure produce changes in the dimen-sion of the capsule chamber.
diminish /d.m.n../ verb to decrease or to reduce in size or importance .
Friction is greatest near the ground and diminishes with height. . At higher alti-tudes, ground objects are less easily seen because of diminished size.
diode /da..υd/ noun an electronic component that allows an electrical cur-rent to pass in one direction and not the other
dioxide /da..ksa.d/ noun an oxide containing two atoms of oxygen. . car-bon dioxide
dip to move e.g. the wing or nose of an aircraft so that it points downwards
direct /da.rekt/ adjective 1. in a
straight line; by the shortest route . a direct flight 2. complete . the direct opposite . verb to guide or control the movement of something . Clamshell doors are hydraulically or pneumati-cally opened, and direct the exhaust gases forwards to produce reverse thrust.
direct current /da.rekt kr.nt/
noun an electric current flowing in one direction only . An electric starter is usually a direct current electric motor coupled to the engine, which automati-cally disengages after the engine starts.
Abbreviation DC direction /da.rek..n/ noun the
course taken by somebody or some-thing . The Earth rotates about its own axis in an anticlockwise direction.
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