Tests on Boeing’s grounded 737 Max have flagged a new safety risk that while unrelated to the fatal crashes, could cause similar accidents and may cause many an airplane crash.
Crashing twice and killing 364 people since October, the aircraft was grounded from March, with US regulators urging the Dreamliner to make design changes. Now, the discovery of a possible new flaw is likely to push back test flights and the aircraft’s return to service.
The Federal Aviation Administration discovered that data processing by a flight computer on the jetliner could cause the plane to dive in a way that pilots had difficulty recovering from in simulator tests, anonymous sources aware of the development told Bloomberg.
The FAA, as well as an independent Technical Advisory Board, have been reviewing Boeing’s software fix in multiple sessions in a special Boeing simulator that is designed for engineering reviews. Boeing and the FAA are also working with the European, Brazilian and Canadian civil aviation authorities.
What caused the earlier crashes?
Two crashes within five months — Lion Air Flight 610 in October off the coast of Indonesia and Ethiopian Airlines Flight 302 in March outside Addis Ababa — beleaguered the venerable brand first flown in 1967.
Preliminary reports into both accidents have suggested they were triggered by a flight control system deploying at the wrong time, due to a faulty sensor. A new stabilization system pushed both planes into steep nosedives from which the pilots could not recover, known in aviation jargon as runaway stabiliser trim.
The incidents served as demonstrable evidence that our current system of design and certification has failed us. Not only Boeing but the FAA too drew sharp criticism for its lack of oversight and the certification process that cleared the Max to fly.
What’s wrong with Boeing now?
It is safe to assume that the recent flaw does not pertain to the Maneuvering Characteristics Augmentation System, which is linked to the fatal accidents and the global grounding of Boeing’s new fourth generation 737 Max jets.
But the latest issue could still produce an un-commanded dive like those that resulted in the crashes.
“On the most recent issue, the FAA’s process is designed to discover and highlight potential risks,” the agency tweeted Wednesday without providing further specifics. “The FAA recently found a potential risk that Boeing must mitigate,” it added.
Exercises on the simulator revealed that pilots might have difficulty responding to the newly identified failure, which could prompt the tail wing or the horizontal stabiliser to move without pilot commands. The motor on the stabiliser adjusts up and down movements, i.e., trim.
Hardware or software issue?
Examining how trim failures occur has been a central part of safety reviews of the plane because it was central to the accidents.
Reuters, which first reported the new issue, said during an FAA pilot simulation in which the stall-prevention system was activated, it had taken longer than expected to recover the aircraft. One of the anonymous sources told CNN, “if you can’t recover in a matter of seconds, that’s an unreasonable risk.”
A variety of sources have linked the problem to the aircraft’s computing power and argued if the processor possessed enough capacity to keep up. While the FAA will look into whether it is a hardware issue, Boeing is convinced it would find a software fix to limit the potency of the stabilisation system.
If regulators are unsatisfied with the software fix, the microprocessor unit will have to be replaced and the grounding may stretch on for months longer than previously thought.
“The FAA will lift the aircraft’s prohibition order when we deem it is safe to do so,” the FAA said in the statement.
Spokespersons at Boeing agreed with the FAA finding and said it was addressing the issue.
A broader software redesign of Boeing’s top-selling aircraft has also been underway for eight months. The company is upgrading the aircraft’s flight control system, which is the focus of crash investigators. The control system can help prevent a plane from stalling.
“The safety of our airplanes is Boeing’s highest priority,” Gordon Johndroe spoke for the airliner adding, “We are working closely with the FAA to safely return the Max to service.” “Addressing this condition will reduce pilot workload” by making it easier to respond to an uncommanded stabiliser motion, Johndroe added.
There were initial hopes among airlines that the 737 Max would be back in the air during the summer, but that timetable has now been pushed back.
Last month, the FAA indicated that approval of Boeing’s changes to the 737 Max could come in late June. That would have allowed test flights in early July. In the light of the newly identified flaw, the company is unlikely to present its final proposed fix to FAA for approval by then. Before that, it has to go through a final test flight with FAA pilots.
Boeing said “we are working closely with the FAA to safely return the Max to service.” Gregory Martin, an FAA spokesman, said Wednesday the regulator “is following a thorough process, not a prescribed timeline, for returning the Boeing 737 Max to passenger service.”
Prarthana Mitra is a Staff Writer at Qrius
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