Delays in 737 Max return began in simulator
Boeing engineers were nearly done redesigning software on the grounded 737 Max in June when some pilots hopped into a simulator to test a few things. It didn’t go well. A simulated computer glitch caused it to to dive aggressively in a way that resembled the problem that had caused deadly crashes off Indonesia and in Ethiopia months earlier.
That led to an extensive redesign of the plane’s flight computers that has dragged on for months and repeatedly pushed back the date of its return to service, according to people briefed on the work. The company — which initially expressed confidence it could complete its application to recertify the plane with the Federal Aviation Administration within months — now says it hopes to do that before the end of the year.
Changing the architecture of the jet’s twin flight computers, which drive autopilots and critical instruments, has proven far more laborious than patching the system directly involved in 737 Max crashes, said these people, who asked not to be named speaking about the issue.
The redesign has also sparked tensions between aviation regulators and the company. As recently as this week, the FAA and European Aviation Safety Agency asked for more documentation of the changes to the computers, said one of the people, potentially delaying the certification further.
Meanwhile, two leading House Democrats wrote to the FAA on Thursday demanding to know why the agency appeared to overrule its own engineers’ concerns about safety issues related to the Boeing 737 Max and the 787 Dreamliner, ultimately siding with the manufacturer rather than its own staff.
House Transportation Committee Chairman Rep. Peter DeFazio, D-Ore., and Rep. Rick Larsen, D-Wash., who chairs the committee’s aviation panel, asked FAA Administrator Stephen Dickson to provide answers about how the agency “weighs the validity of safety issues raised by its own experts compared to the objections raised by the aircraft manufacturers the FAA is supposed to oversee.”
The congressmen wrote: “The two cases … suggest that the opinions and expert advice of the FAA’s safety and technical experts are being circumvented or sidelined while the interests of Boeing are being elevated by FAA senior management.”
The two additional safety issues are unrelated to an automated software system that has been implicated in both crashes. Investigations into the crashes have faulted both assumptions Boeing made in designing the automated feature and the FAA’s oversight and safety approval process.
According to the letter, the new issues “both appear to involve serious, potentially catastrophic safety concerns raised by FAA technical specialists that FAA management ultimately overruled after Boeing objected.” The first concerns whether rudder cable protection on the Max is adequate. The second involves lightning protection for fuel tanks on the 787 Dreamliner.
Compared with the initial redesign of the software system involved in the crashes — a feature known as Maneuvering Characteristics Augmentation System or MCAS — the work on the flight computers will likely create an exponential increase in the safety tests required before it’s approved, said Peter Lemme, a former Boeing engineer who worked on flight-control systems before leaving the company to become a consultant.
“Where before you may have had 10 scenarios to test, I could see that being 100,” Lemme said.
The work on the plane originally focused on MCAS, which repeatedly pushed down the nose in both accidents as a result of a malfunctioning sensor. Pilots eventually lost control and the crashes killed 346 people, prompting a worldwide grounding of the jet on March 13.
Officials from the FAA and the European safety agency expressed frustration with Boeing at a meeting last summer when company representatives didn’t supply a detailed enough explanation of the changes.
A similar issue arose in early November when an audit describing work on the changes wasn’t complete and the agencies ordered Boeing and Collins to revise it, according to a person familiar with the matter.
Boeing, in a statement, said it provided technical documents to regulators “in a format consistent with past submissions.”