Released silently online without any fanfare, the 15-page preliminary report by the Aircraft Accident Investigation Bureau (AAIB) on Air India's flight AI-171 crash was perhaps aimed for minimum exposure but created maximum impact.
For one, the report has raised more questions than it answered. It is focused mainly on the fuel control switches, selective sentences spoken by the pilots recovered from the cockpit voice recorders, the Ram Air Turbine (RAT), and the position of the flap. The tone, tenor, and direction of the preliminary report may lead a casual observer to believe that the crash resulted from the “inadvertent or intentional actions of the pilot" to turn the fuel control switches to cut-off mode, starving the engines of fuel.
The investigation, beginning shortly after the crash occurred, had been joined by officials from the US regulatory body National Transportation Safety Board (NTSB), representatives of Boeing and General Electrics (GE), and the Federal Aviation Administration (FAA) along with the AAIB of the UK as observers to the investigation.
Credibility & Confidentiality in Question
The AAIB report reveals the timeline of how the crash unfolded. Here are some key observations:
The AI-171 aircraft carrying 242 passengers and crew had a normal take-off profile for its flight from Ahmedabad and reached Vr (rotation speed) at 180 knots at 08:08 UTC.
The aircraft air/ground sensors transitioned to air mode consistent with lift-off at 08:08:39 UTC.
The engine run cut-off switches transitioned from RUN to CUTOFF position, one after the other, with a gap of one second, at 08:08:42 UTC.
The N1 and N2 engines began to decrease from take-off values as fuel supply to the engines was cut off.
In the Cockpit Voice Recorder (CVR) recordings, one pilot is heard asking the other, 'Why did you cut off?' The other pilot responded that he did NOT do so (no timing given).
A significant issue has been raised with the airport's CCTV footage showing the RAT being deployed during the initial climb immediately upon lift-off (no timestamp on video).
The Enhanced Airborne Flight Recorders (EAFR) data shows the RAT hydraulic pumps began supplying power at 08:08:47 UTC.
As per EAFR data, the N1engine's fuel cut-off switch transitioned from CUTOFF to RUN at 08:08:52 UTC.
The N2 engine's fuel cut-off switch transitioned from CUTOFF to RUN at 08:08:56 UTC.
Thereafter, each engine, FADEC (Full Authority Digital Engine Control), automatically managed a relight and thrust recovery sequence of ignition and fuel introduction.
At 08:09:05 UTC one of the pilots transmitted, “Mayday, Mayday, Mayday”.
The EAFR recording stopped at 08:09:11 UTC.
Incidentally, a news report leaked in a US-based aviation magazine just three days prior to the preliminary report mentioned how the investigations were skirting around the fuel control switches and the improper, incorrect or intentional actions by the pilots.
A day after the report by The Air Current, the hallowed Wall Street Journal posited the same theory, and added a rider that the “situation had got so bad between the NTSB and the AAIB that the NTSB observers were thinking of withdrawing their cooperation from the investigation and returning home”.
Pertinently, both the reports came just days before India's AAIB report was released, and only after the foreign observers from the NTSB, the AAIB-UK, and Boeing and GE had returned home. This has led to questions over the confidentiality and independence of the AAIB and its report, leading detractors of the government-led process to raise objections in the media.
Are Pilots Guilty?
The pilots, Sumeet Sabharwal and Clyde Kunder, together had more than 19,000 hours of flying experience, with a combined experience of almost 9,724 hours on the 787 type of aircraft. Captain Sabharwal was a trainer and a check pilot on the 787.
The conversation between the two pilots in the cockpit, in which one asks the other, “Why did you cut-off?” with the other responding, “I did NOT do so” is also telling.
It clearly indicates that there was a concern in the cockpit over the fuel cut-off, and both pilots seemed unaware as to how the fuel was cut off.
The lack of the CVR transcript in the preliminary report was a huge dampener, as it gives rise to speculation and conjecture as to what happened in the cockpit. The fact that the AAIB selectively released one sentence from the CVR data, regarding the “fuel cut-off" has added to the confusion.
Moreover, from the selective leaks in the US media, it appears that some foreign agencies had leaked details to foreign media. The influence of big corporations cannot be ruled out given the current state of these corporations.
The preliminary report has set off storm clouds among citizens and pilots' organisations alike. Many are demanding answers, some even seeking a judicial probe headed by a sitting High Court judge.
The Airline Pilots' Association (ALPA India) has issued a press release objecting to the selective media leaks without proper attribution. It has also questioned the foreign involvement in the investigation, and the lack of transparency in the organisations involved and objected to the leaking of details related to the crash to overseas newspapers even before the kin of victims in India got to know what happened.
The presumption of pilots' guilt, failure to include the pilots organisations in the probe, or, in fact, any of the 787-rated check pilots on the panel, as observed by various experts including Captain Kishore Chinta, all raise concerns over the AAIB report's credibility.
Glitches, Theories & Past Warnings
While the pilots appear to be getting easy blame, experts have suggested that it is next to impossible for a pilot strapped in and on the take-off climb to pull both guarded fuel control switches one after the other within ONE SECOND of each other to cut off fuel to both engines.
The EAFR data shows the two engines were cut-off within one second of each other, which appears to be humanly impossible, given that it took both pilots four seconds to recycle and transition the engines from cut-off to RUN stage.
The insinuation on social media has been verging on a “Germanwings” type situation, which has further enraged the aviation community and the Indian travelling public, bringing back sad memories of the Lion Air 737-Max crash. A 24-year-old Indian pilot, Chirag Kalra, was among those wrongly blamed for the crash, which later turned out to be the result of Maneuvering Characteristics Augmentation System (MCAS) issues of the Boeing 737 Max.
Some suggest the AAIB and the NTSB know something they haven’t disclosed yet to the public and are trying to break it gently.
The reluctance of the AAIB to keep the process transparent, and failure to include the entire CVR transcript in the preliminary report have only added to the anger and suspicion of the people. The Digital Flight Data Recorder (DFDR) has still not been fully decoded and studied, and its interpretation will take some time longer.
What makes the preliminary report even more curious is the fact that it pauses to refer to a 2018 FAA Special Airworthiness Information Bulletin (SAIB) No. NM-18-33 on 17 December 2018, which was based on reports from 737 Operators that fuel control switches were installed with locks disengaged. This similar part had been installed on 717, 737, 747, 757, 767, 787, MD-11, and the MD-90 aircraft.
That FAA SAIB which warned of vulnerability in fuel control switches, did not make it mandatory for all airlines, but advised all operators to follow the process of “inspect the locking feature of the fuel control switch to ensure its engagement. Airlines were advised to check whether the fuel control switch can be moved between the two positions without lifting up the switch.
FAA requested airline owners and operators to report any failure of the locking feature of the fuel control switch to Boeing, with date of failure occurrence etc.
At the same time, another FAA directive, which was not relied upon by the AAIB but may be relevant, was an FAA Boeing Alert Bulletin dated 2 May 2022, titled “Engine Fire Control Panel – Engine fire shut-off switch”.
The FAA review of this document was prompted by a report that indicated that Foreign Object Debris (FOD) may have been introduced during the maintenance or rework of certain EFSS units. The FOD risks included “uncommanded activation of the engine fuel shut-off”
The 2022 circular, read with the 2018 notice, firmly established a link between dirty engine fire panels and fuel cutoff switches, though Boeing and unnamed parts' suppliers had already notified operators who received affected parts. So much has gone awry with them in recent times, one can never tell.
The preliminary report noted that Air India had not conducted the safety checks on this equipment in line with the 2018 circular as it was not mandatory but was optional and advisory in nature. The report also noted that Air India had replaced the entire throttle control module in 2019 and 2023 without complaint of Fuel Cutoff switches.
Air India for its part, has issued a statement noting the receipt of the preliminary report of the AAIB and offered to continue cooperation with all the authorities whilst continuing to support the families of the passengers and crew of the ill-fated AI-171. Air India CEO has today also told employees that the crash preliminary report found no issues with aircraft, engines, fuel, etc, and that they had completed all mandatory checks.
To quote Captain Amit Singh, a veteran pilot and the founder of Safety Matters Foundation:
“There was no indication of foul play, no sign that either pilot intended to shut down the engines, but something – Manual, Electrical, or Mechanical – caused both fuel switches to CUT OFF Fuel”.
Experts have opined that there is also no certainty whether the Fuel Control Switches were actually moved to cut-off or whether it was just the electronic functions associated with the switches that were recorded as having cut-off fuel supply to the engines, as the report records the words “transitioned” and not “moved”.
That could even be due to a software or electronic glitch, such as a Thrust Control Malfunction Accommodation (TCMA) malfunction in the Electronic Engine Control (EEC) which sends a signal to other software logic gates, that the aircraft has changed its status from air to ground, as TCMA is the only logic gate software, behind pilot controllers that can automatically shut down the engines, as confidentially shared by a 787 check pilot.
The above theory is taken from the Boeing 787 lab notes, which is available only to Boeing and GE engineers, though this angle requires deeper investigation.
Boiling Questions, Cooling Accountability
The most offensive part of the AAIB report, from the Indian aviation industry's point of view, comes in its final sentences. The report states that “at this time there were no safety recommendations for either Boeing or General Electric”, thereby absolving both the US-based corporate giants of any culpability in this episode.
The barrage of negative press seems to have put the Civil Aviation Ministry in India in a tight spot.
On Saturday, 12 July, the Cabinet Minister of Civil Aviation and his Minister of State for Civil Aviation were compelled to make public statements about how the ministry recognised the skills and hard work of the pilots and cabin crew in Indian aviation. They also asserted that this was merely the preliminary report, meant for fact-finding and that the detailed report that would emerge in some months may have a different thesis.
Despite the government's assurance, the preliminary report raises many questions & issues worth noting:
Why did the report not have the full CVR conversation transcript?
What is the significance of the pilots' conversation over the fuel control switches?
If both pilots did not cut-off the fuel, then was there some electronic glitch?
When and how did the RAT deploy? Images indicate that it may have deployed at 60 ft height, suggesting that engine failure may have occurred even before 08:08:42 UTC.
The fuel control off switches were found in 'RUN' position at the crash site.
The throttles were found in maximum position at the crash site.
The flap handle was set at a five degree angle, positioned in take-off attitude.
The landing gear was down, the Emergency Locator Transmitter (ELT) did not activate.
The deployment of the RAT on take-off indicates total power failure.
Has the possibility of a TCMA-EEC malfunction been investigated yet?
Why did the AAIB remark there were "no safety recommendations for Boeing or GE", thus giving them a veritable get-out-of-jail-free card?
The onus is thus left on the two brave men who died in the cockpit that fateful day. Their entire lives will now be scrutinised in a bid to solve the mystery of the crash, most likely by placing the blame squarely on them.
Dead men tell no tales and the secret of AI-171 may go down with its victims.
(The author is is an aviation analyst, lawyer, and author, who has spent 40 years in aviation. He can be reached at @sjlazars. This is an opinion piece. All views expressed are the author’s own. The Quint neither endorses nor is responsible for them.)