Dead reckoning
reckoning noun navigation using calculations based on airspeed, course, heading, wind direction and speed, ground speed, and time o In the early stages of practical navigation, the student pilot navigates by using dead reckoning. Abbreviation DR (note: The term comes from ‘deduced’ reckoning or ‘ded’ reckoning.)
De-aerate
verb to remove gas, especially carbon dioxide or air, from a liquid such as fuel o The pump helps to de-aerate the fuel before it enters the engine.
de-aeration
noun the process of removing gas from a liquid such as fuel o Partial de-aeration of fuel takes place in the pump.
de-aerator
noun a device to remove gas from a liquid de-aerator tray
noun a device in the lubrication system to remove air bubbles from oil deal
noun □ a great deal a large amount of, a lot of o A great deal of damage was done to the aircraft as a result of the fire. ■ verb to handle or manage o A computer can deal with the constant inputs required to control an unstable aircraft.
debris
noun scattered broken pieces o Before running up the engine, check that the aircraft is on firm ground and that the area is free of stones and other debris. o The aircraft exploded in mid-air, spreading debris over a wide area of the countryside.
decal
noun picture, letters or digits printed on adhesive paper, which is transferred onto a surface and may be peeled away o A red decal with AVGAS 100LL in white letters indicates the type of fuel to be used.
decelerate
‘ verb to slow down o Reverse thrust and brakes help to decelerate the aircraft after landing. Opposite accelerate deceleration
noun slowing down o Anti-skid braking systems units are designed to prevent the brakes locking the wheels during landing, thus reducing the possibility of wheel skid caused by the sudden deceleration of the wheel. Opposite acceleration
decibel
noun a unit for measuring the loudness of a sound.
Abbreviation dB
decimal
noun a decimal fraction ■ adjective □ decimal fraction a fraction as expressed in the decimal system o 0.50 is a decimal fraction that is equal to 1/2. □ correct to three places of decimal or to three decimal places correct to three figures after the decimal point o 2.754 is correct to three decimal places, 2.7 is correct to one decimal place.
decimal notation
noun the method of writing a number in the decimal system o The fraction 3/4 can be written as 0.75 in decimal notation. o Prices and number are normally written using decimal notation. o He finds it difficult to understand how the computer works because it uses binary not decimal notation.
decimal place
noun the position of a number to the right of the decimal point
decimal point
noun the dot (.) used to separate a whole number from a decimal fraction
Comment: The decimal point is used in the USA and Britain. In most European countries a comma (,) is used to show the decimal, so 4,75% in Germany is written 4.75% in Britain.
decimal system
noun system of counting based on the number 10 and using the digits 0 – 9
decision
noun the act of deciding or of making up one’s mind □ to make a decision to choose a course of action o The decision to evacuate the aircraft was made by the captain.
decision height
noun the altitude at which, during an ILS landing approach, a pilot must decide whether to land or carry out a missed approach o The pilot waited until she was at decision height before initiating the missed approach procedure.
Abbreviation DH
Comment: An ILS approach generally has a decision height of 200 ft (60 m) above ground level.
deck
noun the floor of a ship or aircraft decode
verb to change coded information into readable form o Incorrectly spaced information pulses can result in failure by the ground station to decode the aircraft information.
decoder
‘ noun a device used to decode signals from the air traffic control radar beacon system o The aircraft receiver is set to the required frequency and linked to a selective call system decoder which has a 4-letter code.
decrease noun
a lessening or reduction o A decrease in power results in the aircraft descending. ■ verb to become less, to fall o Air density and pressure decrease with an increase in altitude. ► opposite (all senses) increase
deduce
verb to work some thing out in the mind using information provided o Sometimes, it is possible to estimate the depth of the layer of mist or fog from the ground observations and hence to deduce the ground range from any height.
defect
noun a fault or error o Low oil pressure or excessive temperature indicate the development of a possible defect.
defective
adjective faulty or not operating correctly o Loss of supply pressure is caused by either a defective booster pump or lack of fuel.
define
‘ verb 1. to give an exact explanation, as in a dictionary □ it is not easy to define the word it is difficult to say exactly what the word means 2. to set the limits of something o Cloud tops are very difficult to define.
definition
noun an exact explanation of what a word or expression means o The definition of a year is the time taken for a planet to describe one orbit around the sun. □ by definition understood by the use of the word itself o A sphere is, by definition, round.
deflate
verb to allow air to escape from something, so that it becomes smaller or collapses. Opposite inflate □ to deflate a tyre to allow the air to escape from a tyre deflation
noun the act of allowing air to escape from something, so that it becomes smaller or collapses o Deflation of a tyre is done by depressing the valve.
deflect
verb 1. to cause an object to move away from a neutral or central position o During an out-of-bal-ance turn, the ball in the slip indicator will be deflected to the left or right. 2. to move a moving object, gas or liquid away from its intended path o In an open-cockpit aircraft, the windshield deflects the airflow over the pilot’s head.
deflection
noun 1.movement away from a central or neutral position o Full deflection of the ailerons is sometimes needed on takeoff to counteract a crosswind. 2. the movement of a moving object, gas or liquid away from its intended path o In the southern hemisphere the deflection of wind at the equator is to the left.
deformation
noun a change of the correct shape caused by stress o Deformation of wing panels may be an indication of serious structural damage. deg abbreviation degree degradation
noun a decrease in quality o Degradation of the radio signal sometimes makes it impossible to understand the message.
degrade
verb to decrease the quality of something o Interfering signals degrade VOR performance.
degree
noun 1. a level,amount or quantity □ the degree of compression the amount of compression □ a high degree of safety a high level of safety □ to a greater degree more than □ to a lesser degree less than 2. a unit of temperature o twenty degrees Celsius (20°C) o twenty degrees Centigrade (20°C) o seventy degrees Fahrenheit (70°F) 3. a unit of measurement of an angle equal to 1/360th of a circle – each degree is divided into 60 minutes and each minutes into 60 seconds o Make a turn to the right at a bank angle of 30°. □ an angle of 90° a right angle 4. a unit of direction as measured on a compass o east = 090° o west = 270° degrees true
noun degrees of direction measured from true north, not magnetic north. Also called true degrees. Symbol °T dehydration
noun an unwanted and sometimes dangerous loss of water from the body o Dehydration can be avoided by drinking plenty of water.
de-ice
‘ verb to remove ice o
The ground crew de-iced the aircraft prior to take-off.
de-icer
noun a device or substance used to remove ice o De-icer spray should be checked to make sure it is not harmful to light aircraft windscreens.
de-icing
noun the removal of ice ■ adjective referring to the removal of ice o de-icing fluid i> anti-icing, icing
delay
noun a period after the expected time that you have to wait before something happens, the length of time by which something is late o By day, the presence of cloud can cause a delay in clearance of fog. ■ verb 1. to make late, to cause to be late o Take-off was delayed because of fog. 2. to put something off until later o He delayed telling her the news until they had landed.
delayed-action
adjective in which there is an unusual passing of time between stimulus and response o The door is fitted with a delayed-action lock which operates one minute after the power has been switched off.
deliver
verb to provide, to give o The motor will continue to run but will deliver only one-third the rated power. o The pump can deliver fuel at the rate of 2,000 gph.
delivery
noun the act of providing or giving o On some pumps, a depressurising valve is used to block delivery to the system.
delivery pressure
noun the pressure normally expected when fuel is being pumped deluge
noun » fire deluge system
demand
noun 1. a need or use caused by necessity □ high current demand on a generator a situation requiring the generator to produce a lot of electricity 2. a request which is made firmly □ on demand when asked for or ordered o A computer will produce, on demand, a flight plan giving the optimum route, levels and fuel. ■ verb 1. to require as a necessity o Higher operating weights of modern aircraft demand an increase in the number of wheels fitted to the landing gear. 2. to ask firmly o He demanded an explanation.
demonstrate
verb to show by clear example or explanation o Torricelli first demonstrated that the atmosphere has weight. o It will be demonstrated in chapter 12 that turbulence is associated with strong winds.
demonstration
noun a clear, often visual, description or explanation o Your instructor will give a demonstration of the stall-recovery technique.
dense
adjective 1. referring to a substance which is closely compacted □ dense fog thick fog 2. referring to the amount of mass of a substance for a given unit of volume o Air which contains water vapour is less dense than air which does not.
density
noun a quantity of mass for a given unit of volume o air density
density altitude
noun the pressure altitude corrected for non-ISA temperature comment: Density altitude is a very important factor in calculating aircraft performance because of its effect on engine performance, time to reach takeoff speed (and therefore length of take-off run) and rate of climb.
density error
noun a correction to airspeed to give true airspeed
DEP abbreviation
departure message depart
verb to leave o The flight departs at 0200 GMT. Opposite arrive
department
noun a separate part of a complex whole, especially of an organisation departure
‘ noun 1. the act of leaving □ departure time the time when an aircraft becomes airborne 2. the distance between two meridians at any given latitude departure lounge
noun a room at an airport where passengers wait to board their aircraft
departure point
noun a place on the map representing the place from which a flight begins departures
noun the part of an airport that deals with passengers who are leaving depend
verb 1. to be controlled or affected entirely by something o Whether or not an object can be seen by aircrew at a given distance will depend on factors such as size, shape and colour of the object. o If an aircraft ditches in the sea, early rescue depends on rapid location of survivors. 2. to rely on o Pilots depend on air traffic controllers to help them conduct a safe flight.
dependable
adjective reliable, trustworthy o Mercury barometers have largely been replaced by precision aneroid barometers which are smaller, simpler to use, and more dependable.
dependent
adjective relying on or unable to do without something o The height indicated by an altimeter is dependent on the pressure which is set on the sub-scale.
Deploy
verb to come into action, to become ready to be used o Slide rafts are door-mounted and automatically deploy and inflate when the door is opened in the armed position.
