Inbound aircraft to London Heathrow Airport typically follow one of a number of Standard Arrival Routes (STARs). The STARs each terminate at one of four different

RNAV Area navigation (RNAV, usually pronounced as "''ar-nav"'') is a method of instrument flight rules (IFR) navigation that allows an aircraft to choose any course within a network of navigation beacons, rather than navigate directly to and from t ...

waypoints (co-located with VOR navigational aids), and these also define four "stacks" where aircraft can be

held Held may refer to: Places * Held Glacier People Arts and media * Adolph Held (1885–1969), U.S. newspaper editor, banker, labor activist *Al Held (1928–2005), U.S. abstract expressionist painter. *Alexander Held (born 1958), German television ...

, if necessary, until they are cleared to begin their approach to land. Stacks are sections of airspace where inbound aircraft will normally use the pattern closest to their arrival route. They can be visualised as invisible helter skelters in the sky. Each stack descends in 1000 ft (300 m) intervals from 16,000 ft (4,000m) down to 8000 ft (2,100m). If these holds become full, aircraft are held at more distant points before being cleared onward to one of the four main holds.

The stacks

Bovingdon

The Bovingdon stack (BNN) is for arrivals from the north west. It extends above the village of

Bovingdon Bovingdon is a village in Hertfordshire, England, southwest of Hemel Hempstead, and it is a civil parish within the local authority area of Dacorum. It forms the largest part of the ward of Bovingdon, Flaunden and Chipperfield, which had a ...

and the town of

Chesham Chesham (, , or ) is a market town and civil parish in Buckinghamshire, England, south-east of the county town of Aylesbury, north-west of central London, and part of the London commuter belt. It is in the Chess Valley, surrounded by farmla ...

, and uses the RNAV waypoint BNN (co-located with the BNN VOR), which is situated on the former

RAF Bovingdon Royal Air Force Bovingdon or more simply RAF Bovingdon is a former Royal Air Force station located near the village of Bovingdon, Hertfordshire, England, about south-west of Hemel Hempstead and south-east of Berkhamsted. During the Second ...

airfield.

Biggin Hill

The Biggin Hill stack (BIG) on the south east edge of Greater London is for arrivals from the south east. It uses the RNAV waypoint BIG (co-located with the BIG VOR), which is situated on London Biggin Hill Airport.

Lambourne

The

Lambourne Lambourne is a civil parish in the Epping Forest district of Essex, England. It is located approximately 4.5 miles (7 km) South of Epping and 5 miles (8 km) northwest of Romford. It covers an area of , and in 2001 its population was 1, ...

stack (LAM) in Essex is for arrivals from the north east. It uses the RNAV waypoint LAM (co-located with the LAM VOR), which is situated adjacent to Stapleford Aerodrome.

Ockham

The Ockham stack (OCK) in Surrey is for arrivals from the south west. It uses the RNAV waypoint OCK (co-located with the OCK VOR), which is situated on the former

Wisley Airfield Wisley Airfield is a former wartime airfield located in the Parish of Ockham near Wisley in Surrey, England. Originally a grass airstrip, the runway was converted to tarmac in 1952 and used to test aircraft built at Weybridge by Vickers. Flying ...

. During typical easterly operations, the proximity of arrival traffic via OCK requires departures from Heathrow's runway 09R towards the Compton VOR (CPT) to follow a non-standard departure procedure.

Developments

The arrival procedures are being revised since 2014 to reduce stacking by introducing variable speed limits and alternative holding procedures.

Incidents

On 1 December 2003 at 6am, a major disaster in the stack was narrowly avoided. An

air traffic controller Air traffic control specialists, abbreviated ATCS, are personnel responsible for the safe, orderly, and expeditious flow of air traffic in the global air traffic control system. Usually stationed in air traffic control centers and control ...

was blamed by a later inquiry for misdirecting traffic when he ordered a

United Airlines United Airlines, Inc. (commonly referred to as United), is a major American airline headquartered at the Willis Tower in Chicago, Illinois.

Boeing 777 The Boeing 777, commonly referred to as the Triple Seven, is an American long-range wide-body airliner developed and manufactured by Boeing Commercial Airplanes. It is the world's largest twinjet. The 777 was designed to bridge the gap betw ...

into a level of the Bovingdon Hold (or stack) already occupied by a similar

British Airways British Airways (BA) is the flag carrier airline of the United Kingdom. It is headquartered in London, England, near its main hub at Heathrow Airport. The airline is the second largest UK-based carrier, based on fleet size and passengers ...

plane. The two planes, carrying 500 passengers, flew within 600 vertical feet (180 m) of each other.

References

External links

*{{cite web, url=http://avsim.com/atco/dayinthelife.htm , title=ATCO: Day in the life (a real life transcript of air traffic control in the area) , accessdate=2004-11-10 , url-status=bot: unknown , archiveurl=https://web.archive.org/web/20080229134124/http://avsim.com/atco/dayinthelife.htm , archivedate=29 February 2008
London 24 - Layers of London air traffic
NATS, 2014 Aviation in London Aviation in England Heathrow Airport