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Pilot/Controller Glossary 

6/17/21 

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. 

PCG D