D
D-ATIS-
(See DIGITAL-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.)
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 ASSIGNMENT (DAS)-
Delays are distributed 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 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.)
DIGITAL-AUTOMATIC TERMINAL
INFORMATION 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 Airport/Facility Directory.
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
performance 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 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.)
DIRECTLY BEHIND- An
aircraft is considered to be operating directly behind when it is following the
actual flight path of the lead aircraft over the surface of the earth except
when applying wake turbulence separation criteria.
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.)
DTAS-
(See DIGITAL TERMINAL
AUTOMATION SYSTEM.)
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 JO 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.)
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.
DVRSN-
(See DIVERSION.)
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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