British Airways B789 and Thai B773 at Delhi on Oct 7th 2017, simultaneous go around and takeoff result in loss of separation

Last Update: June 12, 2019 / 17:41:09 GMT/Zulu time

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Incident Facts

Date of incident
Oct 7, 2017


Flight number

Delhi, India

Aircraft Registration

ICAO Type Designator

A British Airways Boeing 787-9, registration G-ZBKF performing flight BA-143 from London Heathrow,EN (UK) to Delhi (India) with 216 passengers and 14 crew, was on final ILS approach to Delhi's runway 29 following an arriving A321, ATC did not apply any speed restriction, the aircraft maintained a higher than anticipated speed and the gap of more than 7nm between the two aircraft closed.

A Thai Airways Boeing 777-300, registration HS-TKC performing flight TG-316 from Delhi (India) to Bangkok (Thailand) with 234 passengers and 24 crew, was about to depart. Tower planned to release the aircraft between the arriving A321 and the B789. After the A321 touched down Tower instructed the aircraft to line up runway 29, BA-143 was about 7nm before touchdown after the displaced landing threshold and about 6nm before the threshold of runway 29, and subsequently cleared the flight for takeoff. The crew of TG-316 did not immediately commence takeoff. BA-143 was observed at 4nm before touchdown at 160 KIAS. TG-316 commenced takeoff and was accelerating through 140 KIAS about 1.0nm from the threshold of the runway and 0.2nm past the displaced landing threshold, when BA-143 crossed the threshold of the runway, BA-143 initiated a go around at that point.

Tower provided traffic information about the departing B773 to BA-143, restricted the climb of TG-316 to 2600 feet and instructed BA-143 to climb to 3600 feet expeditiously, in addition tower instructed BA-143 to turn left onto a heading of 180 degrees.

Both aircraft continued their flights without further incident.

India's DGCA reported the minimum separation between the two aircraft reduced to less than 200 feet vertical and less than 1 nautical mile horizontally and on Jun 12th 2019 released their final report concluding the probable cause of the serious incident was:

Non-adherence to the Standard Operating Procedures by the Aerodrome Controller.

Contributory factors

- Failure of approach radar controller to provide adequate inter arrival spacing and to apply speed control methods on the arriving aircraft

- Failure of the crew of TG-316 to adhere to the published departure procedures

- Failure of the crew of BA-143 to adhere to the published speed control norms

The DGCA analysed:

On 07.10.2017, British Airways flight BAW143, B787, from London to New Delhi came in contact with approach final [APST] radar controller at frequency 124.2 MHz and was vectored for ILS approach Rwy 29. The aircraft was changed over to Aerodrome Controller-South at 10 NM from touchdown. At this point of time, BAW143 was number two in the arrival sequence maintaining speed of 185 kts. The number one aircraft Airbus 321 flight AIC014 was 3 miles from touchdown with speed of 140 kts. The inter arrival spacing, with a speed differential of 45 kts between the same type of aircrafts (Heavy/wide body), was less than 8 NM. This inter arrival spacing was continuously reducing and was 6.5 NM when the preceding aircraft was 0.5 NM from touchdown and the succeeding BAW143 was 7NM from touchdown, flying with the speed of 183 kts.

- Approach Radar Controller18 [APST] didn’t apply the speed control restrictions.

- The crew of BAW143 was observed to be reducing speed from 205 Kts at 20 Nm from touch down, 194 kts at 12 Nm from touch down, 185 kts at 10 Nm from touch down ,183 Kts 7.5 Nm from touch down and 176 kts at 5 Nm from touch down but this speed was 20 to 25 kts higher as compared to the speed as laid down in SOP20.

- Tower South Controller gave line up to THA316 for CE2 intersection departure without confirming for immediate departure at time 18:21:57 when the arriving BAW143 was approximately at 7 NM from touchdown with speed of 183 Kts.

- Tower South Controller cleared THA316 for CE2 intersection takeoff at time 18:23:02 when the arriving BAW143 at 4 NM from touchdown with speed of 160 kts.

- The departing THA316 was observed to be taking some time on the runway before starting takeoff roll. Though the Crew of THA316 have stated “After received clearance to line up on runway 29, pilots carried out the standard operation procedure (SOP) as normal. After received takeoff clearance from ATC and Checklist had been completed, pilot took off as normal without delay”, yet the crew of THA316 appears to not followed the standard provisions vide Para 1.5 and 1.6 of ARRIVAL, DEPARTURE PROCEDURE AND RUNWAY CAPACITY ENHANCEMENT MEASURES at Section 5.2 (III) (1) of VIDP AD 2.22 of AIP India at Page AD 2 VIDP-34 and 35.

- The Tower Controller did not take into consideration the developing dynamic situation and didn’t cancel takeoff clearance Thai Airways.. The Tower Controller did not follow the provisions of Para 1.8 of ARRIVAL, DEPARTURE PROCEDURE AND RUNWAY CAPACITY ENHANCEMENT MEASURES at Section 5.2 (III) (1) of VIDP AD 2.22 of AIP India at Page AD 2 VIDP-35.

- The Approach Radar Controller did not follow the provisions of Para and Para of MATS-part 2 Page 29-3 and Page 29-7.

- The speed differential between the preceding and succeeding arrival was high and it was continuously above 30 kts and sometimes more than 50 kts.

- The required standard separation as enunciated by Para of MATS-part1 page 7-15 and depicted vide Figure 4 A: Separation between departing and arriving aircraft was not followed by Tower Controller and crew of BAW 143. In the instant case, the arriving BAW143 had crossed the threshold of RWY29 when the departing THA316 was still rolling on RWY29 abeam Twy Z4. (Figure 8).

- At time 18:24:28, BAW143 reported going around. At this time, BAW143 had crossed threshold of RWY29 (abeam Twy CE2) and the departing/rolling THA316 was still on Rwy29 (abeam Twy Z4)

- The minimum lateral and vertical separation reduced to less than 1 NM and 200 feet respectively.

- The Tower Controller passed the traffic information to BAW143 about departing THA316.

- The Tower Controller restricted the climb of flight THA316 to 2600 feet and asked the flight BAW143 to expeditiously climb to 3600 feet and gave left heading 180 in coordination with Approach Radar Controller. Thereafter the flights were uneventful.

- The Coordination between Tower South Controller and the Approach Radar Controller was affected in non-standard Language.

- Weather was not a contributory factor.
Incident Facts

Date of incident
Oct 7, 2017


Flight number

Delhi, India

Aircraft Registration

ICAO Type Designator

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