Ground delay program
Encyclopedia
An Air Traffic Control
Ground delay program or FAA Flow Control is a traffic flow initiative that is instituted by the Federal Aviation Administration
in the United States Air Space System.
This program is usually instituted when the following events occur at an airport:
Inclement weather
(i.e. reduced visibility
, thunderstorms, snow
),
a large volume of aircraft
going to an airport or en route to another airport
in the same line of flight,
an aircraft incident, closed runway
(s),
a condition that requires increased spacing between aircraft
, such as ILS (Instrument Landing System
) approaches vs. VFR
approaches.
The main factor for determining if a ground delay program is needed is a number called Airport Arrival Rate or AAR. This number is set by the controlling air traffic
facility. When the AAR is reduced by the supporting ATC facility, the ATCSCC, or Air Traffic Control System Command Center, in Herndon
, Virginia
institutes a Ground Delay Program.
Ground delay programs (GDP) can affect various sections of the United States
' airspace, as well as airports in Canada
. That is because NavCanada inherited the agreement between the FAA and Transport Canada
that the Ground Delay Program would be implemented for departures from Canadian airports. GDPs are always assigned a "scope" and to a specific "center" or tier. For instance, if Atlanta was affected by a ground delay program, Air traffic control
could institute delays for just ZTL (Atlanta Center) or each center touching ZTL. It is possible that the delay may affect centers on the second Tier; that is, each center touching the first tier. Sometimes the scope of the ground delay programs is set by mileage; that is, all departures that are less than 1,500 miles from the affected center can be included.
These programs usually last for several hours and average delay minutes can vary as conditions change at the said ATC controlled area.
Each aircraft en route to a particular area is assigned an EDCT (Expect Departure Clearance Time). There are various ways that the FAA computes these delays. To streamline traffic demand the FAA utilizes a computer system called ETMS (Enhanced Traffic Management System) ATRCC ETMS FAA Website which is used by Traffic Management Personnel to predict, on national and local scales, traffic surges, gaps, and volume based on current and anticipated airborne aircraft. Traffic Management Personnel evaluate the projected flow of traffic into airports and sectors, then implement the least restrictive action necessary to ensure that traffic demand does not exceed system capacity. This is also called a "wheels up time" and is when the FAA expects to give takeoff
clearance. Aircraft have +/- 5 minutes on either side of their EDCT to depart or they will be assigned a new
EDCT and expect further delays.
When conditions improve, or when demand decreases, the ATCSCC begins running compressions. This is when the ATC facility can accept more traffic or users; that is, airlines cancel flight plans, thus causing openings. This causes other EDCT times to change and decrease delays.
It is to the flight planner's advantage to file a plan as early as possible to get the earliest EDCT time possible. Once the AAR has been met, planes that filed later in the day will be pushed into the next time block while those that filed early will be assigned an EDCT closer to the time they filed (first come, first served).
Air Traffic Control System Command Center
ATRCC Operational Info System
Air traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
Ground delay program or FAA Flow Control is a traffic flow initiative that is instituted by the Federal Aviation Administration
Federal Aviation Administration
The Federal Aviation Administration is the national aviation authority of the United States. An agency of the United States Department of Transportation, it has authority to regulate and oversee all aspects of civil aviation in the U.S...
in the United States Air Space System.
This program is usually instituted when the following events occur at an airport:
Inclement weather
Weather
Weather is the state of the atmosphere, to the degree that it is hot or cold, wet or dry, calm or stormy, clear or cloudy. Most weather phenomena occur in the troposphere, just below the stratosphere. Weather refers, generally, to day-to-day temperature and precipitation activity, whereas climate...
(i.e. reduced visibility
Visibility
In meteorology, visibility is a measure of the distance at which an object or light can be clearly discerned. It is reported within surface weather observations and METAR code either in meters or statute miles, depending upon the country. Visibility affects all forms of traffic: roads, sailing...
, thunderstorms, snow
Snow
Snow is a form of precipitation within the Earth's atmosphere in the form of crystalline water ice, consisting of a multitude of snowflakes that fall from clouds. Since snow is composed of small ice particles, it is a granular material. It has an open and therefore soft structure, unless packed by...
),
a large volume of aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
going to an airport or en route to another airport
Airport
An airport is a location where aircraft such as fixed-wing aircraft, helicopters, and blimps take off and land. Aircraft may be stored or maintained at an airport...
in the same line of flight,
an aircraft incident, closed runway
Runway
According to ICAO a runway is a "defined rectangular area on a land aerodrome prepared for the landing and take-off of aircraft." Runways may be a man-made surface or a natural surface .- Orientation and dimensions :Runways are named by a number between 01 and 36, which is generally one tenth...
(s),
a condition that requires increased spacing between aircraft
Aircraft
An aircraft is a vehicle that is able to fly by gaining support from the air, or, in general, the atmosphere of a planet. An aircraft counters the force of gravity by using either static lift or by using the dynamic lift of an airfoil, or in a few cases the downward thrust from jet engines.Although...
, such as ILS (Instrument Landing System
Instrument Landing System
An instrument landing system is a ground-based instrument approach system that provides precision guidance to an aircraft approaching and landing on a runway, using a combination of radio signals and, in many cases, high-intensity lighting arrays to enable a safe landing during instrument...
) approaches vs. VFR
Visual flight rules
Visual flight rules are a set of regulations which allow a pilot to operate an aircraft in weather conditions generally clear enough to allow the pilot to see where the aircraft is going. Specifically, the weather must be better than basic VFR weather minimums, as specified in the rules of the...
approaches.
The main factor for determining if a ground delay program is needed is a number called Airport Arrival Rate or AAR. This number is set by the controlling air traffic
Air Traffic
Air Traffic was a British alternative rock band from Bournemouth. Formed in 2003, the band consists of Chris Wall , David Ryan Jordan , Tom Pritchard and Jim Maddock ....
facility. When the AAR is reduced by the supporting ATC facility, the ATCSCC, or Air Traffic Control System Command Center, in Herndon
Herndon
-Places:In the United States:*Herndon, California*Herndon, Kansas*Herndon, Pennsylvania*Herndon, Virginia-People:*Alonzo Herndon , African-American businessman*Angelo Herndon , African-American communist organizer...
, Virginia
Virginia
The Commonwealth of Virginia , is a U.S. state on the Atlantic Coast of the Southern United States. Virginia is nicknamed the "Old Dominion" and sometimes the "Mother of Presidents" after the eight U.S. presidents born there...
institutes a Ground Delay Program.
Ground delay programs (GDP) can affect various sections of the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
' airspace, as well as airports in Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. That is because NavCanada inherited the agreement between the FAA and Transport Canada
Transport Canada
Transport Canada is the department within the government of Canada which is responsible for developing regulations, policies and services of transportation in Canada. It is part of the Transportation, Infrastructure and Communities portfolio...
that the Ground Delay Program would be implemented for departures from Canadian airports. GDPs are always assigned a "scope" and to a specific "center" or tier. For instance, if Atlanta was affected by a ground delay program, Air traffic control
Air traffic control
Air traffic control is a service provided by ground-based controllers who direct aircraft on the ground and in the air. The primary purpose of ATC systems worldwide is to separate aircraft to prevent collisions, to organize and expedite the flow of traffic, and to provide information and other...
could institute delays for just ZTL (Atlanta Center) or each center touching ZTL. It is possible that the delay may affect centers on the second Tier; that is, each center touching the first tier. Sometimes the scope of the ground delay programs is set by mileage; that is, all departures that are less than 1,500 miles from the affected center can be included.
These programs usually last for several hours and average delay minutes can vary as conditions change at the said ATC controlled area.
Each aircraft en route to a particular area is assigned an EDCT (Expect Departure Clearance Time). There are various ways that the FAA computes these delays. To streamline traffic demand the FAA utilizes a computer system called ETMS (Enhanced Traffic Management System) ATRCC ETMS FAA Website which is used by Traffic Management Personnel to predict, on national and local scales, traffic surges, gaps, and volume based on current and anticipated airborne aircraft. Traffic Management Personnel evaluate the projected flow of traffic into airports and sectors, then implement the least restrictive action necessary to ensure that traffic demand does not exceed system capacity. This is also called a "wheels up time" and is when the FAA expects to give takeoff
Takeoff
Takeoff is the phase of flight in which an aerospace vehicle goes from the ground to flying in the air.For horizontal takeoff aircraft this usually involves starting with a transition from moving along the ground on a runway. For balloons, helicopters and some specialized fixed-wing aircraft , no...
clearance. Aircraft have +/- 5 minutes on either side of their EDCT to depart or they will be assigned a new
EDCT and expect further delays.
When conditions improve, or when demand decreases, the ATCSCC begins running compressions. This is when the ATC facility can accept more traffic or users; that is, airlines cancel flight plans, thus causing openings. This causes other EDCT times to change and decrease delays.
It is to the flight planner's advantage to file a plan as early as possible to get the earliest EDCT time possible. Once the AAR has been met, planes that filed later in the day will be pushed into the next time block while those that filed early will be assigned an EDCT closer to the time they filed (first come, first served).
Air Traffic Control System Command Center
ATRCC Operational Info System