New Delhi: Was a software glitch responsible for both engines of Air India Boeing 787-8 Dreamliner reverting to ‘idle’ mode on June 12 in Ahmedabad?
Mary Schiavo, former inspector general of the United States Department of Transportation, who is now a veteran aviation attorney with Motley Rice – one of the largest and most prominent plaintiffs’ law firms in the US, told the Sunday Guardian that the AI-171 crash may have been caused due to a malfunction in the Boeing 787’s engine thrust rollback software.
The crash could be a result of a computer-triggered engine thrust rollback, similar to a known software malfunction in a Boeing 787 aircraft previously investigated by the US National Transportation Safety Board (NTSB), Schiavo said. The NTSB is now participating in the probe into AI-171’s crash.
Here are excerpts of the interview:
Q: Can you please elaborate on which Boeing 787 systems are known to rely on computer inputs to determine whether the aircraft is airborne or on the ground, and how a misclassification could affect engine thrust in-flight?
A: There are several systems that rely on these and similar computer inputs, but in this case, I suspect the Thrust Control Malfunction Accommodation (TCMA), which is a Federal Aviation Administration (FAA)-required addition to the 787 aircraft model. The computer senses when the aircraft is on the ground and when the throttles are supposed to be at idle. The TCMA will instruct the Full Authority Digital Engine Control (FADEC), which controls all aspects of an aircraft engine’s performance. The FADEC automatically (and can do so without pilot input) adjusts engine settings to optimise performance.
Q: In the 2019 incident involving Japan’s Air Nippon Airways (ANA) you referenced, what was the root cause of the dual engine rollback, and was it formally acknowledged as a software design flaw by Boeing or regulators?
A: Yes, as described above, there was an investigation by the US NTSB, and corrective action was ordered on 787s.
Q: Based on your review of similar cases, would a computer-triggered thrust reduction event leave distinct signatures in the flight data recorder that investigators should be looking for in the AI-171 Ahmedabad case?
A: Yes, TCMA and/or FADEC commands will be recorded on the flight data recorder.
Q: Do you see parallels in how Boeing handled disclosure and remediation of the Maneuvering Characteristics Augmentation System (MCAS) issue (which the US DOJ found they tried to hide) and how they may have approached software-based risks in the 787 fleet?
A: There may be a parallel. After the 2019 ANA incident, warnings and requirements for inspection and repair were issued. However, the world’s attention was on the 737 MAX 8 MCAS disasters. While that is no excuse, those Boeing inspections and repair protocols should have been thorough and sufficiently robust to eliminate the problem (and most likely under warranty). All 787s should have been inspected and the repair and software updates completed. Inspection and repairs as instructed by Boeing would have been up to each operator and maintenance operation to ensure completion.
Q: As someone who has litigated multiple international crash investigations, what steps should India’s DGCA, and the AI-171 investigation team prioritise to ensure independent verification of potential software failure — especially if Boeing is involved in the probe?
A: The investigators need to carefully review the aircraft maintenance and repair records, thoroughly examine what the NTSB 787 investigation revealed, investigate what data and records they had from Boeing, and equally important, explore what they did not previously receive or review from Boeing. Furthermore, this aircraft model had the ability to send health data to both Boeing and the airline. Did the airline and/or Boeing have any of this data for this aircraft? If so, what was done with it, and did anyone pay attention?
Q: What can the affected family members do as they wait for answers on the official findings of the crash?
A: Families can ask for frequent updates and to be informed about the investigators’ progress. Family pressure helps prevent investigators from relying too much on Boeing, which is a real problem in accident investigations because Boeing is a party to the investigation, but the families are not.
