## 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 INFOR- MATION SERVICE (D-ATIS) [ICAO]- The provision of ATIS via data link. 

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 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 minima are 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 minima a DH. 

## D 

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. 

DECODER- The device used to decipher signals received from ATCRBS transponders to effect their display as select codes. 

DEFENSE AREA– Any airspace of the contiguous United States that is not an ADIZ in which the control of aircraft is required for reasons of national security. 

DEFENSE VISUAL FLIGHT RULES- Rules applicable to flights within an ADIZ conducted under the visual flight rules in 14 CFR Part 91. 

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 Traffic Flow Management System (TFMS) . 

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 

(See ICAO term DECISION ALTITUDE/DECISION HEIGHT.) 

(See CODES.) 

(See RADAR.) 

(See AIR DEFENSE IDENTIFICATION ZONE.) 

(Refer to 14 CFR Part 91.) 

(Refer to 14 CFR Part 99.) 

