Pilot/Controller Glossary 

4/20/23 

DECODER

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 The device used to decipher signals received from ATCRBS transponders to effect their display 

as select codes. 

(See CODES.) 
(See RADAR.) 

DEFENSE AREA– Any airspace of the contiguous United States that is not an ADIZ in which the control of 

aircraft is required for reasons of national security. 
DEFENSE VISUAL FLIGHT RULES

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 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)

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 Delays are distributed to aircraft based on the traffic management program 

parameters. The delay assignment is calculated in 15

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minute increments and appears as a table in Traffic Flow 

Management System (TFMS)

. 

DELAY COUNTDOWN TIMER (DCT)

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 The display of the delay that must be absorbed by a flight prior to 

crossing a Meter Reference Element (MRE) to meet the TBFM Scheduled Time of Arrival (STA). It is calculated 

by taking the difference between the frozen STA and the Estimated Time of Arrival (ETA). 

DELAY INDEFINITE (REASON IF KNOWN) EXPECT FURTHER CLEARANCE (TIME)

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 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).) 

DEPARTURE CENTER

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 The ARTCC having jurisdiction for the airspace that generates a flight to the impacted 

airport. 
DEPARTURE CONTROL

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 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

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 A program designed to assist in achieving a specified interval over 

a common point for departures. 
DEPARTURE TIME

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 The time an aircraft becomes airborne. 

DEPARTURE VIEWER

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A capability within the Traffic Flow Management System (TFMS) that provides 

combined displays for monitoring departure by fixes and departure airports. Traffic management personnel can 

customize the displays by selecting the departure airports and fixes of interest. The information displayed is the 

demand for the resource (fix or departure airport) in time bins with the flight list and a flight history for one flight 

at a time. From the display, flights can be selected for route amendment, one or more at a time, and the Route 

Amendment Dialogue (RAD) screen automatically opens for easy route selection and execution. Reroute 

options are based on Coded Departure Route (CDR) database and Trajectory Options Set (TOS) (when 

available). 
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

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 Speed deceleration 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

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 In Alaska, in addition to 

being designated for the purpose of carrying out airport advisory practices while operating to or from an airport 

PCG D

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