Boeing's proposed changes to its 737 MAX family flight-control software will undergo "additional work" and may not be in regulators' hands for a final review for another six weeks.
FAA in an April 1 statement said Boeing needs time for more work "as a result of an ongoing review" of the software changes. FAA then plans a "rigorous review" of the proposed changes, which Boeing first detailed publicly March 27.
Boeing said it "continues to work with the U.S. Federal Aviation Administration and other regulatory agencies worldwide on the development and certification of the…software update and training program. We are working to demonstrate that we have identified and appropriately addressed all certification requirements and will be submitting for FAA review once completed in the coming weeks.
"Safety is our first priority, and we will take a thorough and methodical approach to the development and testing of the update to ensure we take the time to get it right," Boeing added.
A source with knowledge of Boeing's thinking said the manufacturer is anticipating four to six more weeks of work.
FAA did not comment beyond its statement.
The 737 MAX fleet has been grounded since March 13, three days after Ethiopian Airlines Flight ET302 crashed near Addis Ababa. It was the second MAX 8 crash in less than five months. Both probes are eyeing the model's maneuvering characteristics augmentation system (MCAS), which helps the MAX handle like its 737NG predecessor in certain flight profiles by pushing its nose down automatically via horizontal stabilizer trim. A system malfunction involving incorrect angle-of-attack data triggering MCAS is believed to have played a role in both accidents.
Boeing reviewed MCAS after the first accident, Lion Air Flight 610 in late October, and determined changes were needed. FAA and the manufacturer were reviewing Boeing's proposed changes when ET302 went down.
Word of the extended timeline marks an abrupt shift. Boeing flight-tested the changes for FAA on March 12. As recently as last week, Boeing was thought to be close to submitting a proposed package to FAA. It held an all-operators' briefing in Seattle, and presented details of the system changes to pilots' groups, all in anticipation of being ready to declare the upgrades ready for regulatory review, a source that participated in the meetings told Aviation Daily.
Aviation Daily understands that a third-party review of the software is behind the revised timeline. FAA has been reviewing the software, but has not provided feedback.
"Upon receipt [of the software], the FAA will subject Boeing's completed submission to a rigorous safety review," the agency's statement said.
The longer software development time likely means an even longer wait for non-U.S. operators looking to get their MAXs back in the air. Several regulators, including the European Aviation Safety Agency, Transport Canada, and the Civil Aviation Administration of China have said they plan their own detailed reviews of the changes, regardless of what FAA decides.
Boeing's proposed changes prevent the updated system from activating based on erroneous data. It also gives pilots ultimate elevator authority by limiting the degree of automatic nose-down stabilizer. Pilots will also receive new training and updated flight manuals. These changes will be part of regulators' demands to lift 737 MAX revenue-service operations bans that have grounded the 376-aircraft fleet.