Disadvantagenoun an unwanted situation or condition, or a factor which makes somebody or something less likely to succeed o The disadvantage of a booster pump is that the output is constant so that when engine demand is high, fuel pressure tends to be low and vice versa. Opposite advantage
comment: The word ‘disadvantaged’ may be regarded by some people as a politically correct term for ‘disabled’. With the help of specially-adapted controls, more and more disabled people are learning to fly.
disappearverb 1. to vanish o If air blew at right angles to isobars, the horizontal pressure differences would eventually disappear. 2. to pass out of sight o The aircraft took off, climbed out and soon disappeared from view.
disarmverb 1. to switch off an active or live system o On the ground approaching the terminal, the flight deck will instruct the cabin crew to disarm the escape devices. 2. to forcibly remove a weapon from somebody o The hijacker was disarmed by security forces.
dischargenoun a release of power from a source such as a battery o A lightning flash is a large-scale example of an electrical spark, or discharge. □ battery discharge the loss or release of electrical supply from a battery ■ verb to release electrical supply from a source such as a battery o The battery discharged overnight.
discriminationnoun the ability to know or see the difference between two similar things o Targets on the same bearing which are separated radially by less than half a pulse length distance will appear at the receiver as one echo, so good target discrimination requires short pulses.
dismantleverb to take apart into single components o One type of inspection is able to reveal fatigue cracks, corrosion, internal damage, the presence of loose articles and mercury spillage without the need to dismantle the aircraft. Opposite assemble (note: The verb ‘mantle’ is not used.)
disorientationnoun a state of confusion in which there is loss of understanding of where one is or which direction one is facing, etc. o When the cabin is rapidly and completely filled by smoke and fumes passengers will suffer from disorientation.
dispersalnoun 1. the act of leaving an area and going in different directions □ the dispersal of a crowd the disappearance of a crowd 2. the clearing away of something such as mist, e.g. by the wind o the dispersal of hill fog o Dispersal of cloud takes place when surface heating lifts the cloud base or drier air is adverted.
disperse‘ verb 1. to leave an area going in different directions □ the crowd dispersed the people in the crowd left the area, going in different directions, so that eventually the crowd disappeared 2. to clear away o The fluorescent green dye will disperse slowly in a calm sea but quickly in a moderate to rough sea.
displacementnoun movement away from the normal position o The ILS is a cross-pointer indicator which shows the aircraft horizontal displacement from the localiser and vertical displacement from the glide path.
displaynoun 1. the appearance of information on a monitor screen or on the panel of an instrument or of an indicator o There are three different types of electronic display systems: EFIS, EICAS and ECAM. □ digital display information shown as numbers o The clock uses a digital display to show the time of 12:33. 2. a show or demonstration ■ verb to show, e.g. on a panel or a screen o Alerting and warning information is displayed.
dissimilaradjective refer ring to something which is not the same as, or is unlike, something else o Differential expansion switches operate on the principle that the coefficients of expansion of dissimilar metals are different.
dissipationnoun the process of spreading out and losing power or strength o The rubber used on nose or tail wheels is usually constructed to form a good electrical conductor for the safe dissipation of static electricity.
dissolveverb to become or to cause to become part of a liquid and form a solution o Sugar dissolves in water. o There is a possibility that in some types of accumulator, gas may be dissolved into the fluid and thus introduced into the system.
distancenoun a space between two places or points, or the measurement of such a space o The distance from point A to point B is 100 nm. o The distance from point A to point B on the diagram is 2 cm. o The height of the aircraft is the vertical distance, measured in feet, of the aircraft above the surface of the Earth.
distance measuring equipmentnoun an airborne secondary radar whose signal is converted into distance o It is quite common to find a VOR located together with DME (Distance Measuring Equipment) to give simultaneous range and bearing from the same point on the ground. Abbreviation DME
comment: DME equipment is usually located in a VOR station. Other equipment in the aircraft transmits a signal to the VOR station, which replies. The equipment in the aircraft converts the signal into distance and also calculates ground speed and the time needed to reach the station.
distortverb 1. to put out of shape o Stress could cause the body of the aircraft to distort or change its shape. 2. to produce a bad radio signal o The sound of the transmission is distorted if the volume is set too high. distortionnoun 1. the bending or twisting of something so that it is out of shape o Difficulty in closing a door may be caused by distortion of the airframe. 2. alteration of the electrical signal that makes a transmission unclear o Distortion of the signal made it difficult for the controller to understand what the pilot said.
distributeverb 1. to give or send out o There are two basic configurations which are used to distribute electrical power, the parallel system and the split bus system. 2. to spread over a wide area o Multiple wheel undercarriage units distribute the weight of the aircraft.
distributionnoun 1. the act of giving or sending out o Parallel AC and DC power distribution systems are found on commercial aircraft containing three or more engines. 2. the fact of being spread over an area o There is a high distribution of used and disused airfields in the south of England.
dive/ noun a steep nose-down attitude of an aircraft □ to pull out of or from a dive to return the aircraft to level flight after a nose-down flight path o During manoeuvring of an aircraft, when banking, turning and pulling out from a dive, stresses on the airframe are increased. ■ verb to put the aircraft into a steep nose-down attitude o The aircraft dived to avoid the other aircraft. (note: diving – dived)
ther apart from something else o Air diverges at low levels and converges at high levels, causing a sinking or subsiding effect in the atmosphere. Opposite converge
divergencenoun the act of moving apart o Divergence of air at high levels leads to rising air at low levels with a consequent pressure fall. Opposite convergence divergentadjective referring to something which moves further apart from something else divergent duct
noun a duct which has an inlet area which is smaller than the outlet area diversionnoun a change in route or destination caused by bad weather, technical problem, etc. o The aircraft had to make a diversion to another airport due to fog. divertverb to turn away from a course or a destination o An automatic cut-out valve is fitted to divert pump output to the reservoir when pressure has built up to normal operating pressure. o The aircraft was diverted to Manchester airport because offog.
divideverb 1. to separate into parts o Air masses are divided into two types according to source region and these are known as polar and tropical air masses. 2. to calculate how many times a number is contained in another number o Eight divided by four equals two (8 ^ 4 = 2).
division/ noun 1. separation into parts □ the division of the lower atmosphere the separation of the atmosphere into its component layers 2.the calculation of how may times a number is contained in another number o The division sign is ^. DME abbreviation distance measuring equipment
Dominateverb to have the most effect or influence on o Because the chart time and the departure/arrival times differ, it is necessary to consider the movement of any weather system which will dominate the route.