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D
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.
DATA BLOCK-
(See ALPHANUMERIC
DISPLAY.)
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]- 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.
Note 1:
Decision altitude [DA] is referenced to mean sea level [MSL] and
decision height [DH] is referenced to the threshold elevation.
Note 2:
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 HEIGHT- With
respect to the operation of aircraft, means the height at which a
decision must be made during an ILS, MLS, or PAR instrument approach
to either continue the approach or to execute a missed approach.
(See ICAO term
DECISION ALTITUDE/DECISION HEIGHT.)
DECODER- The device used to
decipher signals received from ATCRBS transponders to effect their
display as select codes.
(See CODES.)
(See RADAR.)
DEFENSE
VISUAL FLIGHT RULES- Rules applicable to flights within an ADIZ
conducted under the visual flight rules in 14 CFR Part 91.
(See
AIR DEFENSE IDENTIFICATION ZONE.)
(Refer to
14 CFR Part 91.)
(Refer to
14 CFR Part 99.)
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 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.
DESCENT SPEED
ADJUSTMENTS- Speed deceleration calculations made to determine an
accurate VTA. These calculations start at the transition point and use
arrival speed segments to the vertex.
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.
(Refer to AIM.)
DF-
(See DIRECTION FINDER.)
DF APPROACH
PROCEDURE- Used under emergency conditions where another
instrument approach procedure cannot be executed. DF guidance for an
instrument approach is given by ATC facilities with DF capability.
(See DF GUIDANCE.)
(See DIRECTION FINDER.)
(Refer to AIM.)
DF FIX- The geographical
location of an aircraft obtained by one or more direction finders.
(See DIRECTION FINDER.)
DF GUIDANCE- Headings
provided to aircraft by facilities equipped with direction finding
equipment. These headings, if followed, will lead the aircraft to a
predetermined point such as the DF station or an airport. DF guidance
is given to aircraft in distress or to other aircraft which request
the service. Practice DF guidance is provided when workload permits.
(See DIRECTION FINDER.)
(See DF FIX.)
(Refer to AIM.)
DF STEER-
(See DF GUIDANCE.)
DH-
(See DECISION HEIGHT.)
DH [ICAO]-
(See ICAO Term
DECISION ALTITUDE/ DECISION HEIGHT.)
DIRECT- Straight
line flight between two navigational 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.
DIRECT ALTITUDE AND IDENTITY READOUT- The DAIR System is a
modification to the AN/TPX-42 Interrogator System. The Navy has two
adaptations of the DAIR System-Carrier Air Traffic Control Direct
Altitude and Identification Readout System for Aircraft Carriers and
Radar Air Traffic Control Facility Direct Altitude and Identity
Readout System for land-based terminal operations. The DAIR detects,
tracks, and predicts secondary radar aircraft targets. Targets are
displayed by means of computer-generated symbols and alphanumeric
characters depicting flight identification, altitude, ground speed,
and flight plan data. The DAIR System is capable of interfacing with
ARTCCs.
DIRECTION FINDER- A
radio receiver equipped with a directional sensing antenna used to
take bearings on a radio transmitter. Specialized radio direction
finders are used in aircraft as air navigation aids. Others are
ground-based, primarily to obtain a "fix" on a pilot requesting
orientation assistance or to locate downed aircraft. A location "fix"
is established by the intersection of two or more bearing lines
plotted on a navigational chart using either two separately located
Direction Finders to obtain a fix on an aircraft or by a pilot
plotting the bearing indications of his/her DF on two separately
located ground-based transmitters, both of which can be identified on
his/her chart. UDFs receive signals in the ultra high frequency radio
broadcast band; VDFs in the very high frequency band; and UVDFs in
both bands. ATC provides DF service at those air traffic control
towers and flight service stations listed in the Airport/Facility
Directory and the DOD FLIP IFR En Route Supplement.
(See DF FIX.)
(See DF GUIDANCE.)
DISCRETE BEACON CODE-
(See DISCRETE CODE.)
DISCRETE CODE- As used
in the Air Traffic Control Radar Beacon System (ATCRBS), any one of
the 4096 selectable Mode 3/A aircraft transponder codes except those
ending in zero zero; e.g., discrete codes: 0010, 1201, 2317, 7777;
nondiscrete codes: 0100, 1200, 7700. Nondiscrete codes are normally
reserved for radar facilities that are not equipped with discrete
decoding capability and for other purposes such as emergencies (7700),
VFR aircraft (1200), etc.
(See RADAR.)
(Refer to AIM.)
DISCRETE FREQUENCY-
A separate radio frequency for use in direct pilot-controller
communications in air traffic control which reduces frequency
congestion by controlling the number of aircraft operating on a
particular frequency at one time. Discrete frequencies are normally
designated for each control sector in en route/terminal ATC
facilities. Discrete frequencies are listed in the Airport/Facility
Directory and the DOD FLIP IFR En Route Supplement.
(See CONTROL SECTOR.)
DISPLACED THRESHOLD-
A threshold that is located at a point on the runway other than the
designated beginning of the runway.
(See THRESHOLD.)
(Refer to AIM.)
DISTANCE
MEASURING EQUIPMENT- Equipment (airborne and ground) used to
measure, in nautical miles, the slant range distance of an aircraft
from the DME navigational aid.
(See MICROWAVE
LANDING SYSTEM.)
(See TACAN.)
(See VORTAC.)
DISTRESS- A condition of
being threatened by serious and/or imminent danger and of requiring
immediate assistance.
DIVE BRAKES-
(See SPEED BRAKES.)
DIVERSE VECTOR AREA-
In a radar environment, that area in which a prescribed departure
route is not required as the only suitable route to avoid obstacles.
The area in which random radar vectors below the MVA/MIA, established
in accordance with the TERPS criteria for diverse departures,
obstacles and terrain avoidance, may be issued to departing aircraft.
DIVERSION (DVRSN)-
Flights that are required to land at other than their original
destination for reasons beyond the control of the pilot/company, e.g.
periods of significant weather.
DME-
(See DISTANCE MEASURING
EQUIPMENT.)
DME FIX- A geographical
position determined by reference to a navigational aid which provides
distance and azimuth information. It is defined by a specific distance
in nautical miles and a radial, azimuth, or course (i.e., localizer)
in degrees magnetic from that aid.
(See DISTANCE MEASURING
EQUIPMENT.)
(See FIX.)
(See MICROWAVE
LANDING SYSTEM.)
DME SEPARATION-
Spacing of aircraft in terms of distances (nautical miles) determined
by reference to distance measuring equipment (DME).
(See DISTANCE MEASURING
EQUIPMENT.)
DOD FLIP- Department of
Defense Flight Information Publications used for flight planning, en
route, and terminal operations. FLIP is produced by the National
Imagery and Mapping Agency (NIMA) for world-wide use. United States
Government Flight Information Publications (en route charts and
instrument approach procedure charts) are incorporated in DOD FLIP for
use in the National Airspace System (NAS).
DOMESTIC AIRSPACE-
Airspace which overlies the continental land mass of the United States
plus Hawaii and U.S. possessions. Domestic airspace extends to 12
miles offshore.
DOWNBURST- A strong
downdraft which induces an outburst of damaging winds on or near the
ground. Damaging winds, either straight or curved, are highly
divergent. The sizes of downbursts vary from 1/2 mile or less to more
than 10 miles. An intense downburst often causes widespread damage.
Damaging winds, lasting 5 to 30 minutes, could reach speeds as high as
120 knots.
DOWNWIND LEG-
(See TRAFFIC PATTERN.)
DP-
(See INSTRUMENT DEPARTURE PROCEDURE.)
DRAG CHUTE- A parachute
device installed on certain aircraft which is deployed on landing roll
to assist in deceleration of the aircraft.
DSP-
(See DEPARTURE SEQUENCING
PROGRAM.)
DT-
(See DELAY TIME.)
DUE REGARD- A phase of
flight wherein an aircraft commander of a State-operated aircraft
assumes responsibility to separate his/her aircraft from all other
aircraft.
(See also FAAO
7110.65, Para 1-2-1, WORD MEANINGS.)
DUTY RUNWAY-
(See RUNWAY IN USE/ACTIVE RUNWAY/DUTY RUNWAY.)
DVA-
(See DIVERSE VECTOR AREA.)
DVFR-
(See DEFENSE VISUAL FLIGHT
RULES.)
DVRSN-
(See DIVERSION.)
DVFR FLIGHT PLAN- A
flight plan filed for a VFR aircraft which intends to operate in
airspace within which the ready identification, location, and control
of aircraft are required in the interest of national security.
DYNAMIC- Continuous review,
evaluation, and change to meet demands.
DYNAMIC RESTRICTIONS-
Those restrictions imposed by the local facility on an "as needed"
basis to manage unpredictable fluctuations in traffic demands.
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