aircraft on the runway, terminal or center area saturation, weather below landing minimums, etc. 

(See EXPECT FURTHER CLEARANCE (TIME).) 

DELAY TIME- The amount of time that the arrival must lose to cross the meter fix at the assigned meter fix time. This is the difference between ACLT and VTA. 

DEPARTURE CENTER- The ARTCC having jurisdiction for the airspace that generates a flight to the impacted airport. 

DEPARTURE CONTROL- A function of an approach control facility providing air traffic control service for departing IFR and, under certain conditions, VFR aircraft. 

(See APPROACH CONTROL FACILITY.) (Refer to AIM.) 

DEPARTURE SEQUENCING PROGRAM- A program designed to assist in achieving a specified interval over a common point for departures. 

DEPARTURE TIME- The time an aircraft becomes airborne. 

DESCEND VIA– An abbreviated ATC clearance that requires compliance with a published procedure lateral path and associated speed restrictions and provides a pilot-discretion descent to comply with published altitude restrictions. 

DESCENT SPEED ADJUSTMENTS- Speed decel- eration calculations made to determine an accurate VTA. These calculations start at the transition point and use arrival speed segments to the vertex. 

DESIGNATED COMMON TRAFFIC ADVISORY FREQUENCY (CTAF) AREA- In Alaska, in addition to being designated for the purpose of carrying out airport advisory practices while operating to or from an airport without an operating airport traffic control tower, a CTAF may also be designated for the purpose of carrying out advisory practices for operations in and through areas with a high volume of VFR traffic. 

## DESIRED COURSE- 

a. True- A predetermined desired course direction to be followed (measured in degrees from true north). 

b. Magnetic- A predetermined desired course direction to be followed (measured in degrees from local magnetic north). 

DESIRED TRACK- The planned or intended track between two waypoints. It is measured in degrees from either magnetic or true north. The instantaneous angle may change from point to point along the great circle track between waypoints. 

DETRESFA (DISTRESS PHASE) [ICAO]- The code word used to designate an emergency phase wherein there is reasonable certainty that an aircraft and its occupants are threatened by grave and imminent danger or require immediate assistance. 

## DEVIATIONS- 

a. A departure from a current clearance, such as an off course maneuver to avoid weather or turbulence. 

b. Where specifically authorized in the CFRs and requested by the pilot, ATC may permit pilots to deviate from certain regulations. 

DH- (See DECISION HEIGHT.) 

DH [ICAO]- (See ICAO Term DECISION ALTITUDE/ DECISION HEIGHT.) 

DIGITAL-AUTOMATIC TERMINAL INFORMA- TION SERVICE (D-ATIS)- The service provides text messages to aircraft, airlines, and other users outside the standard reception range of conventional ATIS via landline and data link communications to the cockpit. Also, the service provides a computer- synthesized voice message that can be transmitted to all aircraft within range of existing transmitters. The Terminal Data Link System (TDLS) D-ATIS application uses weather inputs from local automated weather sources or manually entered meteorological data together with preprogrammed menus to provide standard information to users. Airports with D-ATIS capability are listed in the Chart Supplement U.S. 

DIGITAL TARGET- A computer-generated symbol representing an aircraft's position, based on a primary return or radar beacon reply, shown on a digital display. 

DIGITAL TERMINAL AUTOMATION SYSTEM (DTAS)- A system where digital radar and beacon data is presented on digital displays and the operational program monitors the system perfor- mance on a real-time basis. 

DIGITIZED TARGET- A computer-generated indication shown on an analog radar display resulting from a primary radar return or a radar beacon reply. 

