Pilot/Controller Glossary

DECODER- 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- 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 COUNTDOWN TIMER (DCT)- 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)- 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- 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.
DEPARTURE VIEWER- 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- 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- In Alaska, in addition to
being designated for the purpose of carrying out airport advisory practices while operating to or from an airport