The Final Descent of AI 171

THERE WAS NO HINT OF ANY DEPARTURE FROM routine when Air India’s flight AI 423 from Delhi landed in Ahmedabad shortly after 11AM on June 12. A minor fault reported by the flight crew was rectified and the 787-8 Boe­ing Dreamliner with registration VT-ANB, a part of the Air India fleet since 2014, was soon ready for the long haul to London’s Gatwick airport. The new crew was at the board­ing gate at 12.35PM and in a little over an hour, with the experienced duo of Captain Sumeet Sabharwal and First Officer Clive Kunder at the helm, AI 171 uneventfully com­pleted pre-flight clearances and began to taxi for take-off.

The acceleration as the aircraft raced down runway 23 was swift and normal and AI 171 achieved liftoff at 39 seconds past 1.38PM, the precise timing confirmed by aircraft air and ground sensors. In less than five seconds, disaster struck with fatal consequences for all except one of the 242 crew and passengers on board. Four seconds after liftoff, just as AI 171 achieved its maximum recorded airspeed of 180 knots and appeared to be climbing safely into the skies above Ahmedabad, the two General Electric engines pow­ering the Dreamliner shut down one after the other. The aircraft lost power and altitude even before it cleared the airport boundary and 23 seconds later, one of the pilots urgently transmit­ted the distress “MAYDAY” call. Even as the air traffic controller on duty sought a response, the officer saw the aircraft crashing a short distance beyond the airport perimeter. Minutes later, fire and rescue vehicles present at the airport rushed to the crash site less than 2km away.

The tragic crash of AI 171 killed all on board—except one passenger who miraculously sur­vived—and 19 others on ground. As it came down, the aircraft scraped some trees, struck a chim­ney and fragmented with its tail, wings, engines and flight deck breaking up over a distance of 765 feet. The plane became a massive fireball as 54,200kg of fuel went up in flames. Later, accident investigators would be able to retrieve very little of the fuel from the aircraft valves and relied on samples from tanks and browsers used to refuel the plane. The flight deck and windshield came to rest about 650 feet southwest from the initial contact with the first of five buildings the aircraft hit as it broke up section-by-section over a crash area that measured 1,000 feet x 400 feet.

The 15-page interim report of the Aircraft Accident Investigation Bureau (AAIB) released on July 12 meticulously records a second-by-second sequence of events from take-off till the Enhanced Airborne Flight Recorders (EAFR) on the plane stopped recording at 11 seconds past 1.39PM. But in doing so, the report sets out an intriguing timeline. Seconds after liftoff, AI 17I’s fuel cut-off switches for the two engines “transitioned” from “run” to “cut-off” within one second of each other. “Engine N1 and N2 began to decrease from their take-off values as fuel supply to the engines was cut off,” the AAIB reports states. The report then makes an observation that is at the centre of intense speculation and vary­ing interpretations. “In the cockpit voice recording, one of the pilots is heard asking the other why did he cut-off [the fuel]. The other pilot responded that he did not do so,” the report states. AAIB does not offer an opinion on the exchange and nor does it provide any other detail even though the recovered audio is two hour-long and, according to the AAIB report, captures the event. “Initial analysis of the recorded au­dio and flight data has been done,” it says.

In the paragraphs dealing with the sudden loss of power in both engines and the cryptic exchange between the pilots who are not identified lie a puzzle that has deepened since the interim report was released. What did the cabin microphone record be­fore and after this conversation? The engine failure resulted in the emergency Ram Air Turbine (RAT) that powers a hydraulic pump to supply power to ensure flight controls and instrumentation function being deployed. CCTV footage shows the RAT popping out on the underside of the aircraft immediately after liftoff. It has been argued that the engines may have failed even before the plane was airborne, but such a scenario seems unlikely. If the engines had begun to bleed power before take-off, the aircraft would have been quite unlikely to gain any height and travel the distance it did before crashing. The deploy­ment of the RAT seems consistent with the AAIB report stating the fuel switches in cut-off mode seconds after liftoff. Based on the EAFR record and CCTV footage, the report concludes the RAT deployed in the initial climb immediately after liftoff. About 10 seconds after the engines shut down, the fuel switches moved to the “run” position. It was too late. A senior pilot said it takes at least 35-40 seconds for the engines to respool or regain thrust. Typically, pilots “spool up” the engines prior to take-off by slowly increasing thrust to generate the required lift. AI 171’s engines began to recover but the aircraft was too low and too slow. The engines did relight, one of them even began reversing the decel­eration, but the plane weighing 2,13,401kg with its complement of passengers, crew, luggage, cargo and fuel, fell to the ground within the next 20 seconds.

THE AIRLINE PILOTS’ Association of India criticised the AAIB report, with its President Captain Sam Thomas say­ing the pilots were being placed in the line of fire. “We feel the investigation is being driven in a direction presuming the guilt of the pilots and we strongly object to this line of thought,” Thomas said. The association said that suitably qualified per­sonnel have not been taken on board in the inquiry. The state­ment also alluded to a report published in the Wall Street Journal on July 10 that referred to the movement of the fuel switches. The ‘leak’ in the US media has led to allegations that the AAIB’s findings were ‘shared’ with foreign publications. The report in WSJ suggests that the inquiry did not find any problem with the Boeing Dreamliner and states the engines lost thrust due to the fuel switches being turned off. The report suggests the pilots were responsible for the switches being turned off. “Pilots use the switches to start the jet’s engines, shut them down, or reset them in certain emergencies. The switches would normally be on during flight, and it is unclear how or why they were turned off…it was unclear whether the move was accidental or inten­tional, or whether there was an attempt to turn them back on.” The report relies on unnamed sources but states the early assess­ments of US officials did not point to any hitch with the aircraft or its engines. As the US National Transportation Safety Board, the Federal Aviation Administration, Boeing and GE Aerospace were assisting the probe, any of the entities—the NTSB, in par­ticular—could have had access to the fuel-switch data. What the WSJ report does not state and where AAIB casts more light is that the switches did indeed move back to the “run” position. The switches can move to off position due to a malfunction, even if this is regarded as a rare possibility.

Civil Aviation Minister Ram Mohan Naidu said AAIB had done a commendable, transparent and professional job in re­trieving the black boxes and interpreting the data at the AAIB laboratory in Delhi. “This is a preliminary report. The ministry is analysing the report. The report says there are multiple things to look at and let us wait for the final report,” Naidu said. Asked about speculation into the actions of the pilots, he said, “I don’t think we should jump into any conclusions. It will be immature to do so.” The carefully timed leak in the US media meant AAIB needed to address the fuel-switch question. In any case, said a pi­lot, the report could not have avoided the mention. On the one hand, the report could be interpreted to mean that the question of the switch being turned off was raised by one pilot and refuted by the other. It would be next to impossible to appreciate the tension in the cockpit and the brief remark need not amount to an indict­ment. The references to the conversation can be over-emphasised and some experts point out the switches would move to the cut-off position even without manipulation by the pilots. They also raise the question whether there is any reason to believe the pilots would have operated the fuel switches when they would be focused on take-off, monitoring the instrumentation panel to check if the aircraft was generating the required thrust.

The stakes are high for all concerned. Tata Sons is battling to ensure its decision to acquire the government-owned airline works out. This has required cutting costs, increasing efficiency of operations, getting employees accustomed to new corporate-style management and accounting for challenges like closure of airspace over Pakistan and parts of the Middle East. Any suggestion that aircraft mechanisms were at fault will be a serious setback for Boeing that has been battling questions over safety and quality, some of which have been raised by former employees. Boeing and Airbus are major players in the commercial aircraft market and the latter has made gains with its A320 range out­pacing Boeing’s 737 in global sales. While more information is awaited, there is convergence between the AAIB report and the accounts in the US media.

THE AAIB REPORT refutes allegations that pilots with requisite experience were not involved in the probe, noting experienced commanders, engineers, aviation medicine specialists and psychologists and flight recorder specialists were on board. The details revealed by the interim report are significant when seen in the context of its conclusion, even if preliminary, that there were no maintenance issues and there was no reason to recommend actions for the Dreamliner 787-8 aircraft or the GE en­gine operators and manufacturers. This finding is reflected in the US media reports prior to the release of the July 12 interim report. The next major check on the VT-ANB was due in December and the engines had been serviced on time. “All applicable airworthi­ness directives and alert service bulletins were complied with on the aircraft as well as the engines,” the report states. It does note that inspections suggested by a Federal Aviation Administration (FAA) December 2018 bulletin in the US regarding potential disen­gagement of the fuel control switch locking mechanism were not carried out by Air India as these were advisory in nature, and not mandatory. It remains open to question if Air India should have carried out the inspections even if they were not mandatory in the interest of flight safety. The FAA bulletin had been issued based on reports from operators of Boeing 737s that the control switches were installed with the locking feature disengaged. In checks carried out on its fleet after the Ahmedabad accident, Air India reported that the fuel switches were glitch-free. The Directorate General of Civil Aviation issued a direction after Etihad and Korean Air carried out simi­lar checks. Though this was too late for the ill-fated aircraft, the AAIB report does note the plane had reported no defect pertaining to fuel control switches since 2023. A full report may be as much as a year away, but AAIB does not seem to have found any faults, mechanical or otherwise, in the aircraft.

The initial clean bill of health to the aircraft and the snatches of cockpit conversation relating to fuel switches has given rise to the theory of “pilot suicide”, suggesting an error on part of at least one of the flight crew. Air India Chief Executive Officer Campbell Wilson, in an internal memo after the AAIB report was released, said the preliminary report found no mechanical or maintenance faults and that all required main­tenance had been carried out even as he cautioned against prema­ture conclusions. There has been a strong pushback from pilots and their associations who argue the partial reporting defames Sabharwal and Kunder and is unfair to their families. The fate of the pilots is a poignant tale as Sabharwal was living with his aged father and was reportedly considering retirement, while Kunder was single and his parents were in Australia at the time of the crash. “The report seems tilted against the pilots,” said a se­nior pilot. The AAIB report does not offer any view on culpability and more details will need to surface to exactly map why AI 171 suffered a very rare mishap with both engines shutting down moments after take-off. Pilots familiar with Dreamliners say the aircraft needed patient handling after they were first inducted in 2013-14. Even though Air India under government ownership suf­fered from poor management, its flight crew and engineers were known for their diligence and skills that helped integrate the new aircraft. There have been instances of decompression and, on occasion, sluggish handling but all that did not seem to add up to serious deficiencies. A GE service bulletin issued in 2021 recommends a change of a mi­croprocessor related to engine fuel and control but it is unclear whether this pertains to aircraft already in service. A former US Department of Transporta­tion official Mary Schiavo has claimed that investigation into an All Nippon Airways flight in 2019 that experienced a dual engine flameout revealed a software problem where the fuel switch transitioned without any intervention from the pilots. While Dreamliners, until the Ahmedabad crash, had not been involved in major ac­cidents, the 737 Max aircraft were in the news for fatal crashes in 2018 and 2019 caused by a malfunctioning flight control system that pushed the planes into nosedives.

The crash is expected to give rise to significant insurance claims with reports that Air India had increased the cover for the aircraft to `850 crore. The initial compensation to relatives is being paid out but there are bound to be more claims, both indi­vidual and corporate. Compensation is due to people who died on the ground and those who were injured at the site of the crash. The AAIB report provides some relief to both Air India and Boeing in the context of the probe not finding any fault with maintenance or the aircraft. But the suspense will remain till the cause of the crash is identified. It is possible the investigators have formed an initial opinion and are awaiting more analysis and evidence. Till they firm up an opinion, there will no closure for the families of Sabharwal and Kunder or for the survivors and next of kin of others who died in the tragedy.

AhmedabadAI171Air IndiaBoeing 787 DreamlinerClive Kunderinterim reportinvestigationplane crashSumeet Sabharwal