Pilot/Controller Glossary

D-ATIS-
(See DIGITAL-AUTOMATIC TERMINAL INFORMATION SERVICE.)

D-ATIS [ICAO]-
(See ICAO Term DATA LINK 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.)

DATA LINK AUTOMATIC TERMINAL INFORMATION SERVICE (D-ATIS) [ICAO]- The provision of
ATIS via data link.
DCT-
(See DELAY COUNTDOWN TIMER.)

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.
DEBRIS RESPONSE AREA (DRA)- Used by ATC. Areas of airspace that may be activated in response to
unplanned falling debris in the NAS.
DECISION ALTITUDE/DECISION HEIGHT [ICAO Annex 6]- 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.
1. Decision altitude (DA) is referenced to mean sea level and decision height (DH) is referenced to the threshold
elevation.
2. Category II and III minimre expressed as a DH and not a DA. Minima is assessed by reference to a radio
altimeter and not a barometric altimeter, which makes the minim DH.
3. 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 ALTITUDE (DA)- A specified altitude (mean sea level (MSL)) on an instrument approach
procedure (ILS, GLS, vertically guided RNAV) at which the pilot must decide whether to continue the approach
or initiate an immediate missed approach if the pilot does not see the required visual references.
DECISION HEIGHT (DH)- With respect to the operation of aircraft, means the height at which a decision must
be made during an ILS or PAR instrument approach to either continue the approach or to execute a missed
approach.
(See ICAO term DECISION ALTITUDE/DECISION HEIGHT.)