India’s government has set up a high-level committee which intends to disclose findings within three months on the Air India Boeing 787-8 crash in Ahmedabad.
While the 12 June crash is being probed by the Indian Aircraft Accident Investigation Bureau, the committee will be tasked with ascertaining the “root cause” of the accident – and contributing factors – and examining the emergency response, with a view to putting forward recommendations.
“The committee will not be a substitute to other enquiries being conducted by relevant organisations but will focus on formulating [standard operating procedures] for preventing and handling such occurrences in the future,” says the ministry of civil aviation.
While investigators have recovered a flight recorder from the crash site, about 1.7km from the departure end of Ahmedabad airport’s runway 23, few clues have emerged over the reason behind the 787’s loss of lift, some 15s after rotation, as it took off for London Gatwick.
Surveillance camera footage shows the aircraft’s landing-gear remained extended throughout the flight, which lasted around 30s.
Loss of lift would typically indicate the aircraft has insufficient airspeed for the aircraft’s weight, wing configuration, or angle of attack – a situation which might arise from lack of thrust, incorrect flap settings, or excessive attitude.
Generation of lift is particularly sensitive in rarefied air. Ahmedabad is not a high-elevation airport, at just 189ft altitude, but it has a reference temperature of 42.4°C according to the Indian aeronautical information publication.
The aircraft involved (VT-ANB), fitted with 256 seats, was heavily-laden with 230 passengers and 12 crew members on board.
Investigators will explore several aspects of the flight to understand the extent to which technical or operational issues contributed to the 787’s failure to climb away.
Ahmedabad has an 11,500ft (3,505m) runway. The inquiry’s analysis will cover the aircraft’s weight and balance, the accuracy of take-off performance calculations – including the rotation speed – and the status of the autopilot and autothrottle.
Under normal circumstances the aircraft should have been able to continue climbing if one of its GE Aerospace GEnx engines failed.
Uncommanded thrust roll-back of both engines, or a dual failure from birdstrike, fuel starvation or simultaneous technical fault, would be unusual but not inconceivable. Loss of thrust in both GEnx engines of Jetstar 787-8, descending to Kansai in March 2019, was traced to the use of a specific biocide in fuel, subsequently withdrawn.
The Air India inquiry has yet to confirm a loss of thrust capability and whether the ram-air turbine was activated to provide electrical power.
Stall risks associated with an incorrect configuration were illustrated by the Spanair Boeing MD-82 accident at Madrid in August 2008, during which the jet attempted to take off without its flaps extended. The MD-82’s pilots did not complete flap and slat checks during flight preparation, and the configuration warning system on the aircraft was not functioning.
Video of the Air India 787 is inconclusive with regards to the flap setting, but failing to configure the aircraft would involve defeating layers of protection.
Once positive climb has been established, the flying pilot calls for landing-gear retraction – this typically occurs about 10s after lift-off.
There have been instances – at least in some aircraft types – of flap levers being inadvertently moved instead of the landing-gear lever. Premature flap retraction, for whatever reason, would reduce the margin between the airspeed and stall speed. If the aircraft approached a stall, while still close to the ground, the inquiry will want to understand the crew’s response as well as that of angle-of-attack protection systems.
Both the Indian accident investigation bureau and the government’s high-level committee will be given access to various sources, including flight-recorder information, maintenance records, air traffic control communications, interviews and testimonies.
Speaking after recovery personnel retrieved a flight recorder from the wreckage, civil aviation minister Ram Mohan Naidu Kinjarapu said that the investigation bureau believes decoding the recorder will give “in-depth insight into what would have happened during the process of the crash or moments before”.
