D

D‐ATIS-(See DIGITAL‐AUTOMATIC TERMINAL INFORMATION SERVICE.)
DA [ICAO]-
(See ICAO Term DECISION
ALTITUDE/DECISION HEIGHT.)

DAIR-
(See DIRECT ALTITUDE AND IDENTITY
READOUT.)

DANGER AREA [ICAO]- An airspace of defined dimensions within which activities dangerous to the flight of aircraft may exist at specified times.
Note: The term “Danger Area” is not used in reference to areas within the United States or any of its possessions or territories.
DAS-(See DELAY ASSIGNMENT.)
DATA BLOCK-
(See ALPHANUMERIC DISPLAY.)
DEAD RECKONING- Dead reckoning, as applied to flying, is the navigation of an airplane solely by means of computations based on airspeed, course, heading, wind direction, and speed, groundspeed, and elapsed time.
DECISION ALTITUDE/DECISION HEIGHT [ICAO]-A specified altitude or height (A/H) 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.
Note 1: Decision altitude [DA] is referenced to mean sea level [MSL] and decision height [DH] is referenced to the threshold elevation.
Note 2: The required visual reference means that section of the visual aids or of the approach area which should have been in view for sufficient time for the pilot to have made an assessment of the aircraft position and rate of change of position, in relation to the desired flight path.
DECISION HEIGHT- With respect to the operation of aircraft, means the height at which a decision must be made during an ILS, MLS, or PAR instrument approach to either continue the approach or to execute a missed approach.
(See ICAO term DECISION
ALTITUDE/DECISION HEIGHT.)

DECODER- The device used to decipher signals received from ATCRBS transponders to effect their display as select codes.
(See CODES.)
(See RADAR.)
DEFENSE VISUAL FLIGHT RULES-Rules applicable to flights within an ADIZ conducted under the visual flight rules in 14 CFR Part 91.
(See AIR DEFENSE IDENTIFICATION ZONE.)
(Refer to 14 CFR Part 91.)
(Refer to 14 CFR Part 99.)
DELAY ASSIGNMENT (DAS)- Delays are distrib-uted to aircraft based on the traffic management program parameters. The delay assignment is calculated in 15-minute increments and appears as a table in Enhanced Traffic Management System (ETMS).
DELAY INDEFINITE (REASON IF KNOWN) EXPECT FURTHER CLEARANCE (TIME)- Used by ATC to inform a pilot when an accurate estimate of the delay time and the reason for the delay cannot immediately be determined; e.g., a disabled aircraft on the runway, terminal or center area saturation, weather below landing minimums, etc.