In less than 40 seconds.
This is the airborne of Air India Flight 171 in India’s recent memory in one of India’s most confusing aviation disasters.
Now, investigators are facing a grim mission of sifting wreckage and decoding the Boeing 787 Dreamliner’s cockpit sound and flight data logger to piece together catastrophic errors seconds after takeoff. According to international rules formulated by the United Nations aviation agency ICAO, a preliminary investigation report should be issued within 30 days, and the final report is ideally completed within 12 months.
The plane bound to London Gatwick, piloted by Captain Sumeet Sabharwal and co-pilot Clive Kundar, was evacuated from the western Indian city of Ahmedabad on Thursday at 13:39 local time (08:09 GMT), with 242 people and nearly 100 tons of fuel on board. Within a moment, Mayday’s phone was cracked from the cockpit. This will be the last gearbox. Then there was a loss of altitude and a crash in the flames.
Captain Kishore Chinta, a former investigator of the Indian Aircraft Accident Investigation Agency (AAIB), called it the “rare rare” crash – a controlled aircraft just 30 seconds after takeoff. “As far as I know, something like this has never happened.”
Did both engines fail due to bird strikes or fuel pollution? Are the flaps improperly stretched, reducing lift on the heavy-loaded jet in extremely high heat? Are there maintenance errors during engine repairs? Or was it an unintentional crew movement that cut off the fuel from the two engines?
Indian Army Engineers prepare to cancel wreckage of Ahmedabad Air Flight [Reuters]
Investigators will explore all these possibilities, and even more. The investigation of air collapse relies on triangulation and elimination – matching physical evidence in the wreckage with recorded aircraft performance data to create a coherent picture of the problem.
Each hot cable, damaged turbine blade, aircraft maintenance logs, and flight data and signal and sound from the cockpit recorder – the so-called “black box” – will be inspected. The BBC spoke with accident experts to see how the investigation will proceed.
At least three investigators said at least two investigators said the first local clues might have come from wreckage from both engines.
“From the damage, whether the engine produces electricity when spinning at high speeds – there is a difference in the turbine fracture,” said Peter Goelz, former managing director of the National Transportation Safety Board (NTSB). “This is the first clue that something goes wrong.”
Turbines are crucial rotating components that play a key role in extracting energy to generate thrust.
“If the engine does not generate power, there is a serious case in the investigators’ hands – the focus will be drastically shifted to the cockpit.”
The Boeing 787’s enhanced Airborne Flight Recorder (EAFRS) or “Black Box” will reveal what’s going on in the cockpit – which will help tell the story, investigators say. (Indian officials say the recorder has been recovered from the crash site.)
These devices capture a wide range of flight data and cockpit audio – from test radio calls to ambient cockpit sound. Voice recordings come from a single pilot microphone, radio transmission and microphone to pick up background noise in the cockpit.
The data logger tracks the position of gears and flap bars with high accuracy, thrust settings, engine performance, fuel flow, and even fire handle activation.
Boeing 787 crashes into medical student’s hotel outside Ahmedabad airport [Reuters]
“If the flight data logger shows that the engine is achieving full force, then the attention will shift to the flaps and slats. If they are found to expand as needed, then this will become a very difficult investigation.”
Flaps and slats increase lift at lower speeds, helping the aircraft land safely by allowing slow flights without stagnation.
“if [the trail leads] This will attract serious concern for a problem in flight management control systems – not only for Boeing, but for the aviation industry as a whole. ”
The Boeing 787’s flight management control system is a highly automated suite that manages navigation, performance and guidance. It integrates data from many sensors to optimize the aircraft’s flight path and fuel efficiency.
Experts say that since 2011, more than 1,100 Boeing 787 people have flew around the world, and investigators must determine that this is a systematic issue that could affect the global fleet – or is it a one-time failure unique to the flight. “If system issues are pointed out, then regulators have to make some difficult decisions very quickly,” Mr Golds said.
So far, there is no sign of anyone. India’s Civil Aviation Ministry said on Tuesday that it had recently conducted an inspection of Air India’s 787 fleet – 24 of 33 aircraft have been inspected so far – “no significant safety issues were found,” adding that the aircraft and maintenance systems comply with existing standards.
“Boeing will comply with India’s Aircraft Accident Investigation Agency (AAIB) to obtain information on Air India Flight 171 and comply with the UN ICAO agreement,” said Kelly Ortberg, president and CEO of Boeing.
The decoding of the data at the AAIB laboratory in Delhi will be led by Indian investigators, experts from Boeing, engine manufacturer GE, Air India and Indian regulators. Investigators from the NTSB and the UK will also participate.
“In my experience, teams can usually determine what’s happening very quickly,” Golds said. “But it can take longer to understand why it happens.”
The wreckage may generate additional clues. “Every part – wires, nuts, bolts – is carefully collected,” Mr Chinta said.
Usually, wreckage is moved to a nearby hangar or security facility, placed to identify the nose, tail and wings, and then pieced together. In this case, based on flight data and what the voice recorder reveals, investigators say, a comprehensive reconstruction may not be required.
Investigators say the importance of the wreck varies by chance. For Malaysia Airlines flight MH17, which was shot down in eastern Ukraine in July 2014, is crucial – the reconstruction of the nose shows that Russian-made missiles have caused obvious shrapnel damage.
Air India’s landing gear 171 at the crash site of Ahmedabad [Bloomberg via Getty Images]
In the wreckage, investigators will also check fuel filters, lines, valves and residual fuel to check for contamination – easily detectable or eliminated contaminants, preferring to keep the crash investigator who wishes to be named. In addition, he believes that the refueling equipment used before departure “may have been quarantined and inspected.”
That’s not all. Mr Chinta said investigators will collect maintenance and failure history from the airline and Boeing’s ACAR (aircraft communications and reporting system), which is transmitted to Boeing and Air India via radio or satellite.
They will review all flights operated by the aircraft and crew in recent months, as well as technical logs of faults and corrective actions reported by pilots taken before the release of the aircraft service.
Investigators will also check pilot permits, training records, simulator performance and instructor reviews – including solutions like how pilots deal with engine failures in advanced flight simulators. “I think Air India could have provided these records for the investigation team,” Mr Chinta said.
Investigators will review the service history of all components of the aircraft being removed and replaced, check for defects in any duplicate problems reported, or signs of problems that may affect the flight.
“These investigations are very complex. They take time, but there will be early indicators that something might be wrong,” Golds said.
An important reason is how far technology has gone. “One of the first accidents I investigated in 1994 had only one flight data recorder tracking four parameters,” he said.
“Today’s recorders capture hundreds (if not thousands) per second. That’s all that has changed the way we investigate the collapse.”
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