On 5 April 1996 a significant loss of separation occurred in daylight when a BOEING 747-400 (international, winglets) being operated by British Airways and having just taken off from runway 27R at London Heathrow came into conflict to the west of the Airport with an AIRBUS A-300-600 being operated by Emirates which had just, upon ATC instruction, commenced a missed approach from the parallel runway 27L.
An Investigation was carried out by the UK AAIB which established by reference to the ATC Separation Monitoring Function(SMF) equipment which monitors aircraft separation but is not contemporaneously displayed to controllers, that "at their closest proximity the two aircraft were between 600 and 700 feet apart vertically and between 0·71 and 0·82 nm horizontally.
The event happened shortly after a third aircraft had burst a tyre during a landing on runway 27L some 3 minutes earlier. The response to this circumstance led to an expected temporary increase in controller workload in circumstances where the two runways were under the control of separate TWR ATCOs and with one runway designated for landings and one for take offs.
It was found that prior to the loss of separation, both aircraft had been correctly following their ATC clearances and that both had then received and correctly followed TCAS RAs, the B744 to descend and the A306 to adjust vertical speed. Simultaneously to the TCAS RA activation, corrective ATC clearances had been issued.
The Investigation concluded that "by adhering to the TCAS instructions, the crews of both aircraft prevented a possible collision" and noted that the specific procedures established for ATC response in the event of a missed approach occurring which required the Departures and Arrivals Controllers to co-ordinate with each other to maintain separation were "not complied with in this incident".
No Safety Recommendations were made.
The full AAIB Final Report of the Investigation was published on 4 July 1996. Note that the 'Figure 1' referred to in the Report is not available online at the original source.
Nearly two years later, a question for written answer was asked in the UK Parliament about the ATC follow up actions as a result of this event:
Extract from the Official Record of` Written Answers to UK Parliamentary Questions for the Minister for Environment, Transport and the Regions given in the House of Commons on Monday 9 February 1998:
“NATS have supplied the following details about measures taken in response to their internal review of the Airprox incident in question:
- Controller simulation training was modified--additional "go-around" 1 events were added to simulator training and a specific video on go-arounds in a parallel runway situation was included in classroom training
- Controller competency requirements were modified to require controllers to practice regularly calls to the Terminal Control facility in the event of a go-around"