Air Traffic Flow Management (usually seen abbreviated as ATFM) is the regulation of air traffic in order to avoid exceeding airport or air traffic control capacity in handling traffic, and to ensure that available capacity is used efficiently. Air Traffic Control Towers (ATCTs) at Schiphol Airport Air Traffic Control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and in the air. ...

Reason for use

Because only one aircraft can land or depart from a runway at the same time, and because aircraft must be separated by a certain time to avoid collisions, every airport has a finite capacity; it can only safely handle so many aircraft per hour. This capacity depends on many factors, such as the number of runways available, layout of taxi tracks, availability of air traffic control, but also on current or anticipated weather. Especially the weather can cause large variations in capacity because strong winds may limit the number of runways available, and poor visibility may necessitate increases in separation between aircraft. Air traffic control can also be limiting, there are only so many aircraft an air traffic control unit can safely handle. Staff shortages, radar maintenance or equipment faults can lower the capacity of a unit. This can affect both airport air traffic control as well as en-route air traffic control centers. Runway 13R/31L of El Dorado International Airport, Bogotá, D.C. Aerial picture of a runway of Chennai International Airport, Tamil Nadu A runway is a strip of land on an airport, on which aircraft can take off and land. ... Weather is an all-encompassing term used to describe all of the many and varied phenomena that can occur in the atmosphere of a planet. ... This temporary flight restriction map from the Federal Aviation Administration shows the boundaries of the regions controlled by the Area Control Centers within and adjoining the continental United States, as well as the IATA airport code of each such Center operated by the United States. ...

When an air traffic control unit that will control a flight reaches capacity, arriving aircraft are direct towards holding patterns where they circle until it is their turn to land. Because aircraft flying in circles is an inefficient and costly way of delaying aircraft, it is preferable to keep them on the ground at their place of departure. This way, the delay can be waited out on the ground with engines off, saving considerable amounts of fuel (a large jet aircraft can use dozens of gallons of fuel per minute in the air). Obviously, careful calculation of enroute time for each flight (and the effect of current wind upon it) and traffic flow as a whole is needed, which is highly dependent on computers. Dozen is another word for the number twelve. ... The gallon (abbreviation: gal) is an English unit of volume. ... A Lego RCX Computer is an example of an embedded computer used to control mechanical devices. ...

Operation

All IFR flight plans are tracked by a CFMU (Central Flow Management Unit). Each airport and air traffic control sector has a published maximum capacity (also called rate). When capacity is exceeded, measures are taken to reduce the traffic. This is termed regulation. The aim is to keep the average delay as low as possible, while ensuring capacity is not exceeded. in-flight refueling Instrument flight rules Interface Repository Integral Fast Reactor This page concerning a three-letter acronym or abbreviation is a disambiguation page — a navigational aid which lists other pages that might otherwise share the same title. ... Flight plans are plans filed by pilots with the local Aviation Authority (e. ...

As a (highly simplified) example, if two flights are scheduled to arrive at an airport at exactly the same time, and the airport can handle one aircraft every 5 minutes, the aircraft may be assigned delays to ensure that the second aircraft arrives 5 minutes after the first. Similarly, the first aircraft will be required to depart on schedule and not allowed to depart late. This way, the second aircraft will not need to wait in the air.

In practice, the process is much more complex and highly computerized. One aircraft may be subject to several regulations at the same time. For example, a flight from Amsterdam to Paris may be regulated both by limited capacity at Paris as well as by limited capacity in Belgian airspace. Amsterdam Location Flag Country Netherlands Province North Holland Population 743,905 (1 April 2006) Demonym Amsterdammer Coordinates Website www. ... Part of the Paris and La Défense skylines with from left to right: Montparnasse Tower, Eiffel Tower, and La Défense towers. ...

In some cases, it may be possible to avoid delay by taking a different route. For instance, if Belgian airspace was the only regulation for the flight in the previous example, changing the route to avoid Belgium and going via Germany instead might allow a flight to depart without delay, although the route might be a bit longer. In many cases, airlines authorize the CFMU to make changes in a flight's route to avoid delay. An airline is an organization providing aviation services to passengers and/or cargo. ...

Certain flights are exempt from regulation, for instance time-critical flights carrying human organs for organ transplantation. If such flights are scheduled, regular traffic will be delayed instead. Trinomial name Homo sapiens sapiens Linnaeus, 1758 Humans, or human beings, are bipedal primates belonging to the mammalian species Homo sapiens (Latin for wise man or knowing man) under the family Hominidae (known as the great apes). ... In biology, an organ (Latin: organum, instrument, tool) is a group of tissues that perform a specific function or group of functions. ... An organ transplant is the transplantation of a whole or partial organ from one body to another (or from a donor site on the patients own body), for the purpose of replacing the recipients damaged or failing organ with a working one from the donor site. ...

If an airport is completely closed unexpectedly (for instance, because the only runway is blocked), a zero rate may be set for a certain time period (e.g. until the runway is expected to be reopened), which will cause all inbound flights to be issued a delay that will cause them to arrive after the reopening time. Flights already enroute would either enter the holding or divert to an alternate airport.

Slot & Calculated Take-Off Time

The CFMU issues delays by means of a CTOT (Calculated Take-Off Time), also known as slot time or simply slot. The slot is actually a period of time within which take-off has to take place - in Europe (Eurocontrol) is defined between -5 and + 10 minutes from CTOT. The aircraft is required to be at the runway, ready for departure at it's CTOT, the leeway is for air traffic control to integrate the aircraft into the other traffic. EUROCONTROL is the European Organisation for the Safety of Air Navigation, an international organisation whose primary objective is the development of a seamless, pan-European Air Traffic Management (ATM) system. ... Air Traffic Control Towers (ATCTs) at Schiphol Airport Air Traffic Control (ATC) is a service provided by ground-based controllers who direct aircraft on the ground and in the air. ...

If a slot is missed (or if it is already certain in advance that it will be missed), CFMU assigns a new one. A different aircraft which has a slot because of the same regulation may be issued an improvement on its slot to make use of the newly available capacity. The slot and any revisions are communicated to the aircraft operator as well as the air traffic control unit at the departure airport via a special network called AFTN. AFTN (Aeronautical Fixed Telecommunication Network) is a worldwide system of aeronautical fixed circuits provided, as part of the aeronautical fixed service, for the exchange of messages and/or digital data between aeronautical fixed stations having the same or compatible communications characteristics. ...

It is perhaps surprising to some, that a delay in Los Angeles may be incurred because inclement weather is expected at the destination in London, 10 hours later, even though the weather in Los Angeles is good and there is no congestion. Blaming a delay on the departure airport or the airline is often not correct. Capacity limitations of the airspace between the two aerodromes, in the en-route segment, can also be a reason for delays.

External links / sources

1. http://www.cfmu.eurocontrol.be/cfmu/public/subsite_homepage/homepage.html Eurocontrol CFMU Website

2. http://www.fly.faa.gov FAA Air Traffic Control System Command Center home page