Reference
Aviation glossary
Concise definitions for aviation terminology — from METAR and NOTAM to aerodynamics and airline operations. Search directly or scan alphabetically.
D
DatumA fixed reference point from which all horizontal distances are measured in aircraft weight and balance calculations. Every arm, moment, and center of gravity determination starts from the datum. De-Ice SystemsDe-ice systems remove ice accumulation that has already formed on aircraft surfaces. Unlike anti-ice systems that prevent ice formation, de-ice systems use pneumatic boots or heating elements to crack and shed existing ice buildup. De-icingDe-icing is the process of removing ice, snow, or frost from an aircraft's surfaces before flight to restore aerodynamic safety. Crews typically apply heated de-icing fluid followed by thicker anti-icing fluid to prevent new ice from forming... Decision AltitudeDecision Altitude (DA) is the lowest height during a precision instrument approach at which a pilot must see the runway environment or immediately execute a go-around. It is expressed as altitude above mean sea level (MSL). Demonstrated CrosswindThe maximum crosswind component tested by a manufacturer during flight testing and published in the aircraft's operating handbook, not a certified regulatory limit. Density altitudeDensity altitude is pressure altitude corrected for temperature deviation from standard atmosphere. It indicates the altitude at which air density, and thus aircraft performance, actually exists. DepressurizationDepressurization is the loss of pressurized cabin air in an aircraft at altitude, either suddenly or gradually. When cabin pressure drops below safe levels, occupants cannot breathe without supplemental oxygen. Destination Coded VehicleA Destination Coded Vehicle (DCV) is a small automated cart that transports individual bags through an airport baggage system along a track network, routing each bag to the correct outbound chute based on barcode data. Dew PointThe dew point is the temperature at which air becomes fully saturated with water vapor and condensation begins to form. In aviation, dew point is critical for predicting fog, low clouds, and icing hazards. DewpointDewpoint is the temperature at which air becomes fully saturated with water vapor and condensation begins to form. When air cools to its dewpoint, moisture turns into liquid water, creating fog, dew, or clouds. Differential PressureThe difference in pressure between two points in a system. In aviation, differential pressure is measured to determine airspeed, monitor system health, and detect component failures. DownwashDownwash is the downward deflection of air behind a wing as it generates lift. This moving air continues past the trailing edge at an angle and creates induced drag while affecting tail effectiveness. DragDrag is the aerodynamic force that opposes an aircraft's motion through the air, acting parallel to the relative wind. It increases with speed and consists of parasite drag (from shape and friction) and induced drag (from lift generation). Drag coefficientA dimensionless number that quantifies how much aerodynamic drag an object generates relative to its size and airspeed, expressed as CD in the drag equation. DriftDrift is the sideways displacement of an aircraft from its intended ground track, caused by wind pushing the aircraft laterally while it flies. Pilots correct for drift by applying a wind correction angle, pointing the nose into the wind to...
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