Engineering and regulatory complications are expected to delay safety fixes covering hundreds of Boeing Co. 737 MAX jets until at least April, according to industry and government officials familiar with the details.
Boeing is developing revised software for an automated flight-control feature that can forcefully push down the nose of MAX aircraft and was implicated in a high-profile Lion Air crash in Indonesia this past October. But the work has dragged on months longer than initially anticipated following the accident, these officials said.
In addition to engineering challenges, they said, another reason for the delay stems from differences of opinion among some federal and company safety experts over how extensive the changes should be.
Originally, software updates were expected to be fairly straightforward and slated to be announced in early January. But since then, there have been discussions about potentially adding enhanced pilot training and possibly mandatory cockpit alerts to the package, according to one person briefed on the details.
There also has been consideration of more-sweeping design changes that would prevent faulty signals from a single sensor from touching off the automated stall-prevention system, officials said. But at this point, they said, such options appear to be losing favor among regulators.
The 35-day partial government shutdown—during which consideration of the fixes was suspended—also created further delays.
Over the weekend, a Boeing spokesman said the company “continues to evaluate the need for software or other changes as we learn more from the ongoing investigation.” He declined to elaborate on specifics.
Since the accident, the FAA has said it is considering taking action depending on the results of the investigation, and also reviewing certain issues related to its certification of 737 MAX aircraft
The Oct. 29 crash of Lion Air Fight 610 roughly 11 minutes after takeoff from Jakarta, killing all 189 on board, has raised fundamental questions about the limits and potential downsides of cockpit automation. The tragedy has highlighted the hazards when automated flight-control features fail or misfire, and pilots aren’t able to respond properly.
Boeing has faced criticism from some airline officials, aviators and pilot union leaders for omitting details about the new stall-prevention system in the 737 Max’s manuals or training requirements, which were approved by the FAA.
The Chicago-based plane maker has said the process to create its manuals and training for the 737 Max was consistent with developing previous airplanes, and that it provided information needed to safely fly the airplane. Boeing has said the airplane is safe and noted it is in operation around the world.
Boeing favors a relatively simple solution that would primarily reduce the power and under some circumstances, probably the repetitive nature of the suspect flight-control system, called MCAS, according to these government and industry officials tracking the process. That appears to be the most likely outcome, they said, though no final decisions have been made. And the timing for an announcement remains fluid.
The FAA is poised to mandate changes to the 737 MAX once there is a company-government consensus about the overall package.
The stakes in the current debate go beyond skirmishes over arcane engineering judgments or Boeing’s design philosophy. The upshot, according to some industry officials and outside safety experts, could affect future suits filed by lawyers representing families of victims.
The accident probe will take months to complete, as investigators look at factors ranging from maintenance to operations to aircraft design.
The Indonesian-led investigation has tentatively concluded that sensor-calibration issues during maintenance touched off the fatal sequence of events, according to people familiar with the process. Investigators also have said the automated flight-control system was central to the crash, and they have publicly identified a number of pilot slip-ups that appear to have played an important part.
The stall-prevention system was designed just for the 737 MAX, a variant of Boeing’s workhorse single-aisle jet that Boeing debuted in 2015. U.S. operators of the new plane include Southwest Airlines Co., American Airlines Group Inc. and United Continental Holdings Inc.
Among measures the FAA has considered was whether to require all 737 MAX airplanes to be outfitted with indicators that alerts pilot when sensors that feed into the stall-prevention system disagree, the officials said. So-called angle of attack sensors essentially reflect the angle of the plane’s nose versus level flight. Cockpit alerts that show when such sensors disagree are currently optional on the fleet.
Preliminary data released by Indonesian investigators points to the MCAS feature misfiring when incorrect signals from a single angle-of-attack sensor prompted the system to repeatedly push down the plane’s nose.
In the Lion Air crash, investigators have indicated the pilots fought the MCAS system as it strongly and repeatedly pushed down the plane’s nose, but didn’t follow an existing procedure to deactivate it. Indonesian authorities have recovered, and more recently downloaded data from, Lion Air Flight 610’s cockpit-voice recorder. But they haven’t indicated what clues it may provide about the crew’s understanding of the system, and why shortly before the fatal dive the co-pilot apparently eased back on his nose-up commands.