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Aviation Dictionary

Reference:

1 Airplane Flying Handbook
2 Pilot's Handbook of Aeronautical Knowledge
3 Instrument Procedures Handbook
4 Risk Management Handbook
5 Aviation Instructor Handbook
6 Seaplane Handbook
7 Balloon Handbook
8 Aeronautical Information Manual
9 Airplane Flying Handbook
10 Pilot Controller Glossary
11 Glider Handbook

D

DA

2 See decision altitude.

5 See decision altitude.

Database Columns

4 The spaces for data entry on each record. One column can accommodate one character.

Database Field.

4 The collection of characters needed to define one item of information.

Database Identifier

4 A specific geographic point in space identified on an aeronautical chart and in a naviation database, officially designated by the controlling state authority or derived by Jeppesen. It has no ATC function and should not be used in filing flight plans nor used when communicating with ATC.

Database Record

4 A single line of computer data made up of the fields necessary to define fully a single useful piece of data.

Datum (reference datum)

1 An imaginary vertical plane or line from which all measurements of moment arm are taken. The datum is established by the manufacturer. Once the datum has been selected, all moment arms and the location of CG range are measured from this point.

2 An imaginary vertical plane or line from which all measurements of arm are taken. The datum is established by the manufacturer. Once the datum has been selected, all moment arms and the location of CG range are measured from this point.

Dark adaptation

2 Physical and chemical adjustments of the eye that make vision possible in relative darkness.

5 Physical and chemical adjustments of the eye that make vision possible in relative darkness.

D.C.

2 Direct current.

5 Direct current.

Dead reckoning

2 Navigation of an airplane solely by means of computations based on airspeed, course, heading, wind direction and speed, groundspeed, and elapsed time.

12 Navigation by computing a heading from true airspeed and wind, then estimating time needed to fly to a destination.

Deceleration error

2 A magnetic compass error that occurs when the aircraft decelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward South.

5 A magnetic compass error that occurs when the aircraft decelerates while flying on an easterly or westerly heading, causing the compass card to rotate toward South.

Decision altitude (DA)

2 A specified altitude in the precision approach, charted in feet MSL, at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.

4 A specified altitude in the precision approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been established. The term “Decision Altitude (DA)” is referenced to mean sea level and the term “Decision Height (DH)” is referenced to the threshold elevation. Even though DH is charted as an altitude above MSL, the U.S. has adopted the term “DA” as a step toward harmonization of the United States and international terminology. At some po

5 A specified altitude in the precision approach, charted in feet MSL, at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.

12 Pressure altitude corrected for nonstandard temperature variations. Performance charts for many older gliders are based on this value.

Decision height (DH)

2 A specified altitude in the precision approach, charted in height above threshold elevation, at which a decision must be made either to continue the approach or to execute a missed approach.

4 See Decision Altitude.

5 A specified altitude in the precision approach, charted in height above threshold elevation, at which a decision must be made either to continue the approach or to execute a missed approach.

Decompression sickness

1 A condition where the low pressure at high altitudes allows bubbles of nitrogen to form in the blood and joints causing severe pain. Also known as the bends.

Defense mechanisms

7 Subconscious ego-protecting reactions to unpleasant situations.

Deice

2 The act of removing ice accumulation from an aircraft structure.

5 The act of removing ice accumulation from an aircraft structure.

Deicer boots

1 Inflatable rubber boots attached to the leading edge of an airfoil. They can be sequentially inflated and deflated to break away ice that has formed over their surface.

Deicing

1 Removing ice after it has formed.

Delamination

1 The separation of layers.

Delta

2 A Greek letter expressed by the symbol Δ to indicate a change of values. As an example, ΔCG indicates a change (or movement) of the CG.

Demonstration-performance method

7 An educational presentation where an instructor first shows the learner the correct way to perform an activity and then has the learner attempt the same activity.

Density altitude

1 This altitude is pressure altitude corrected for variations from standard temperature. When conditions are standard, pressure altitude and density altitude are the same. If the temperature is above standard, the density altitude is higher than pressu

2 Pressure altitude corrected for nonstandard temperature. Density altitude is used in computing the performance of an aircraft and its engines.

5 Pressure altitude corrected for nonstandard temperature. Density altitude is used in computing the performance of an aircraft and its engines.

Departure End of Runway (DER)

4 The end of runway available for the ground run of an aircraft departure. The end of the runway that is opposite the landing threshold, sometimes referred to as the stop end of the runway. Altitude, velocity vector, and direction to all other aircraft and air traffic control facilities within a specific area. Automatic dependent surveillance-broadcast (ADS-B) information is displayed in the flight deck via a cockpit display of traffic information (CDTI) unit, providing the pilot with greater situ

Departure procedure (DP)

2 Preplanned IFR A TC departure, published for pilot use, in textual and graphic format.

5 Preplanned IFR A TC departure, published for pilot use, in textual and graphic format.

Deposition

2 The direct transformation of a gas to a solid state, in which the liquid state is bypassed. Some sources use sublimation to describe this process instead of deposition.

Descend Via

4 A descend via clearance instructs you to follow the altitudes published on a STAR. You are not authorized to leave your last assigned altitude unless specifically cleared to do so. If ATC amends the altitude or route to one that is different from the published procedure, the rest of the charted descent procedure is canceled. ATC will assign you any further route, altitude, or airspeed clearances, as necessary.

Description of the skill or behavior

7 The first part of a performance-based objective which explains the desired outcome of instruction in concrete terms that can be measured.

Designated pilot examiner (DPE)

1 An individual designated by the FAA to administer practical tests to pilot applicants.

Determiners

7 In test items, words which give a clue to the answer. Words such as “always” and “never” are determiners in true-false questions. Since absolutes are rare, such words usually make the statement false.

Detonation

1 The sudden release of heat energy from fuel in an aircraft engine caused by the fuel-air mixture reaching its critica pressure and temperature. Detonation occurs as a violent explosion rather than a smooth burning process.

2 The sudden release of heat energy from fuel in an aircraft engine caused by the fuel-air mixture reaching its critical pressure and temperature. Detonation occurs as a violent explosion rather than a smooth burning process.

Deviation

2 A magnetic compass error caused by local magnetic fields within the aircraft. Deviation error is different on each heading.

5 A magnetic compass error caused by local magnetic fields within the aircraft. Deviation error is different on each heading.

Dew

2 Moisture that has condensed from water vapor. Usually found on cooler objects near the ground, such as grass, as the near-surface layer of air cools faster than the layers of air above it.

Dewpoint (or dewpoint temperature)

1 The temperature at which air can hold no more water.

2 The temperature at which air reaches a state where it can hold no more water.

12 The temperature to which a sample of air must be cooled, while the amount of water vapor and barometric pressure remain constant, in order to attain saturation with respect to water.

DGPS

2 Differential global positioning system.

5 Differential global positioning system.

DH

2 See decision height.

5 See decision height.

Digital ATIS (D-ATIS)

4 An alternative method of receiving ATIS reports by aircraft equipped with datalink services capable of receiving information in the flight deck over their Aircraft Communications Addressing and Reporting System (ACARS) unit.

Digital Elevation Model (DEM)

4 A digital representation of ground surface topography or terrain.

Dihedral

12 The angle at which the wings are slanted upward from the root to the tip.

Differential ailerons

1 Control surface rigged such that the aileron moving up moves a greater distance than the aileron moving down. The up aileron produces extra parasite drag to compensate for the additional induced drag caused by the down aileron. This balancing of the

2 Control surface rigged such that the aileron moving up moves a greater distance than the aileron moving down. The up aileron produces extra parasite drag to compensate for the additional induced drag caused by the down aileron. This balancing of the

Differential Global Positioning System (DGPS)

2 A system that improves the accuracy of Global Navigation Satellite Systems (GNSS) by measuring changes in variables to provide satellite positioning corrections.

5 A system that improves the accuracy of Global Navigation Satellite Systems (GNSS) by measuring changes in variables to provide satellite positioning corrections.

Differential pressure

2 A difference between two pressures. The measurement of airspeed is an example of the use of differential pressure.

Dihedral

2 The positive acute angle between the lateral axis of an airplane and a line through the center of a wing or horizontal stabilizer. Dihedral contributes to the lateral stability of an airplane.

Diffusion

1 Reducing the velocity of air causing the pressure to increase.

Diluter-demand oxygen system

2 An oxygen system that delivers oxygen mixed or diluted with air in order to maintain a constant oxygen partial pressure as the altitude changes.

Direct indication

2 The true and instantaneous reflection of aircraft pitch-and-bank attitude by the miniature aircraft, relative to the horizon bar of the attitude indicator.

5 The true and instantaneous reflection of aircraft pitch-and-bank attitude by the miniature aircraft, relative to the horizon bar of the attitude indicator.

Direct question

7 A question used for follow-up purposes, but directed at a specific individual.

Directional stability

1 Stability about the vertical axis of an aircraft, whereby an aircraft tends to return, on its own, to flight aligned with the relative wind when disturbed from that equilibrium state. The vertical tail is the primary contributor to directional stabil

2 Stability about the vertical axis of an aircraft, whereby an aircraft tends to return, on its own, to flight aligned with the relative wind when disturbed from that equilibrium state. The vertical tail is the primary contributor to directional stabil

Direct User Access Terminal System (DUATS)

2 A system that provides current FAA weather and flight plan filing services to certified civil pilots, via personal computer, modem, or telephone access to the system. Pilots can request specific types of weather briefings and other pertinent data for

5 A system that provides current F A A weather and flight plan filing services to certified civil pilots, via personal computer, modem, or telephone access to the system. Pilots can request specific types of weather briefings and other pertinent data for planned flights.

Discrimination

7 The degree to which a test distinguishes the differences between learners.

Distance circle

2 See reference circle.

5 See reference circle.

Distance measuring equipment (DME)

2 A pulse-type electronic navigation system that shows the pilot, by an instrument-panel indication, the number of nautical miles between the aircraft and a ground station or waypoint.

5 A pulse-type electronic navigation system that shows the pilot, by an instrument-panel indication, the number of nautical miles between the aircraft and a ground station or waypoint.

Distractors

7 Incorrect responses to a multiple-choice test item.

Disuse

7 A theory of forgetting that suggests a person forgets those things that are not used.

DME

2 See distance measuring equipment.

5 See distance measuring equipment.

DME arc

2 A flight track that is a constant distance from the station or waypoint.

5 A flight track that is a constant distance from the station or waypoint.

Ditching

1 Emergency landing in water.

Diurnal effects

12 A variation (may be in temperature, moisture, wind, cloud cover, etc.) that recurs every 24 hours.

Diverse Vector Area (DVA)

4 An airport may establish a diverse vector area if it is necessary to vector aircraft below the minimum vectoring altitude to assist in the efficient flow of departing traffic. DVA design requirements are outlined in FAA Order 8260.3 and allow for the vectoring of aircraft immediately off the departure end of the runway below the MVA.

DOD.

2 Department of Defense.

5 Department of Defense.

Doghouse

2 A turn-and-slip indicator dial mark in the shape of a doghouse.

5 A turn-and-slip indicator dial mark in the shape of a doghouse.

Domestic Reduced Vertical Separation Minimum (DRVSM)

2 Additional flight levels between FL 290 and FL 410 to provide operational, traffic, and airspace efficiency.

5 Additional flight levels between FL 290 and FL 410 to provide operational, traffic, and airspace efficiency.

Double gimbal

2 A type of mount used for the gyro in an attitude instrument. The axes of the two gimbals are at right angles to the spin axis of the gyro, allowing free motion in two planes around the gyro.

5 A type of mount used for the gyro in an attitude instrument. The axes of the two gimbals are at right angles to the spin axis of the gyro, allowing free motion in two planes around the gyro.

Downburst

12 A strong, concentrated downdraft, often associated with a thunderstorm. When these reach the ground, they spread out, leading to strong and even damaging surface winds.

Downwash

1 Air deflected perpendicular to the motion of the airfoil.

DP

2 See departure procedure.

5 See departure procedure.

Drag curve

1 A visual representation of the amount of drag of an aircraft at various airspeeds.

2 The curve created when plotting induced drag and parasite drag.

5 The curve created when plotting induced drag and parasite drag.

Drift angle

1 Angle between heading and track.

2 Angle between heading and track.

Drill and practice method

7 A time-honored training delivery method based on the learning principle that connections are strengthened with practice.

Dry adiabat

12 A line on a thermodynamic chart representing a rate of temperature change at the dry adiabatic lapse rate.

Dry adiabatic lapse rate (DALR)

12 The rate of decrease of temperature with height of unsaturated air lifted adiabatically (not heat exchange). Numerically the value is 3 °C or 5.4 °F per 1,000 feet.

DUATS

2 See direct user access terminal system.

5 See direct user access terminal system.

Duplex

2 Transmitting on one frequency and receiving on a separate frequency.

5 Transmitting on one frequency and receiving on a separate frequency.

Ducted-fan engine

1 An engine-propeller combination that has the propeller enclosed in a radial shroud. Enclosing the propeller improves the efficiency of the propeller.

Dutch roll

1 A combination of rolling and yawing oscillations that normally occurs when the dihedral effects of an aircraft are more powerful than the directional stability. Usually dynamically stable but objectionable in an airplane because of the oscillatory na

2 A combination of rolling and yawing oscillations that normally occurs when the dihedral effects of an aircraft are more powerful than the directional stability. Usually dynamically stable but objectionable in an airplane because of the oscillatory na

Dust devil

12 A small vigorous circulation that can pick up dust or other debris near the surface to form a column hundreds or even thousands of feet deep. At the ground, winds can be strong enough to flip an unattended glider over on its back. Dust devils mark the location where a thermal is leaving the ground.

Dynamic hydroplaning

1 A condition that exists when landing on a surface with standing water deeper than the tread depth of the tires. When the brakes are applied, there is a possibility that the brake will lock up and the tire will ride on the surface of the water, much l

2 A condition that exists when landing on a surface with standing water deeper than the tread depth of the tires. When the brakes are applied, there is a possibility that the brake will lock up and the tire will ride on the surface of the water, much l

Dynamic stability

1 The property of an aircraft that causes it, when disturbed from straight-and-level flight, to develop forces or moments that restore the original condition of straight and level.

2 The property of an aircraft that causes it, when disturbed from straight-and-level flight, to develop forces or moments that restore the original condition of straight and level.

12 A glider’s motion and time required for a response to static stability.