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Last updated: 3 June 2020
Status:
Date:Monday 8 June 1959
Type:Silhouette image of generic COMT model; specific model in this crash may look slightly different
de Havilland DH-106 Comet 4
Operator:British Overseas Airways Corporation - BOAC
Registration: G-APDA
C/n / msn: 6401
First flight: 1958
Engines: 4 Rolls-Royce Avon 524
Crew:Fatalities: 0 / Occupants: 9
Passengers:Fatalities: 0 / Occupants: 44
Total:Fatalities: 0 / Occupants: 53
Aircraft damage: Substantial
Aircraft fate: Repaired
Location:Calcutta-Dum Dum Airport (CCU) (   India)
Phase: Approach (APR)
Nature:International Scheduled Passenger
Departure airport:Bangkok-Don Muang International Airport (BKK/VTBD), Thailand
Destination airport:Calcutta-Dum Dum Airport (CCU/VECC), India
Flightnumber:931
Narrative:
The aircraft, which was operating the Tokyo-London passenger service Speedbird 931 of BOAC, was attempting to land at Calcutta Airport with the aid of the Instrument Landing System. The earlier stages of the approach to Runway 19L proceeded without incident. Turbulence was encountered necessitating increased power to stabilize the fluctuating air speed at the recommended figure. The increased power was applied too late with the result that sudden sinking of the aircraft and an impact with trees could not be avoided.
Thereafter, partial loss of lateral control was experienced as considerable damage had been caused to the flaps. The missed approach procedure was then successfully carried out. The next approach was made on to runway 01R. The aircraft was then being flown by visual reference. During this approach the aircraft again impacted the trees as due allowance was not made for the higher stalling speed of the damaged aircraft. Missed approach procedure was again initiated and the aircraft responded well. However, further damage had been sustained. A circuit was executed and the landing during the third attempt was successful, but the damaged aircraft failed to pull up within the available length of the wet runway because of the higher speed at which the approach had to be justifiably made.
No injury was sustained by the 44 passengers and nine members of the crew on board. The aircraft was substantially damaged.

Probable Cause:

Accident causes:
The accident is attributed to an error of judgement on the part of flying crew in not applying power when approaching to land under turbulent conditions. The subsequent power increase was applied too late to prevent the aircraft, which was being flown at a speed below the speed recommended for turbulent conditions, from sinking and striking trees.

Sources:
» Flight, 8 June 1961
» Flight, 3 June 1960
» Flight, 3 Feb. 1961


Follow-up / safety actions
Remedial action: Comet 4 flight manual approach speed was increased by 5kt after the incident

Photos

photo of de-Havilland-DH-106-Comet-4-G-APDA
accident date: 08-06-1959
type: de Havilland DH-106 Comet 4
registration: G-APDA
 

Map
This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path.
Distance from Bangkok-Don Muang International Airport to Calcutta-Dum Dum Airport as the crow flies is 1600 km (1000 miles).

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.
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