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Aeronautical Information Manual (AIM), page 638

Pilot/Controller Glossary 5/26/16


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
12/10/15

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.
DIRECT- Straight line flight between two naviga-
tional aids, fixes, points, or any combination thereof.
When used by pilots in describing off-airway routes,
points defining direct route segments become
compulsory reporting points unless the aircraft is
under radar contact.
DIRECTLY BEHIND- An aircraft is considered to
be operating directly behind when it is following the

PCG D-2

Page 638 of the Aeronautical Information Manual (AIM.pdf)
AIM: Official Guide to Basic Flight Information and ATC Procedures

Index   637 -- Page 638 -- 639