FAA Says Boeing to Revise Its Analysis of 737 Max Software Fix

• Memo may shed light on delay in submitting upgrade to agency
• Boeing had said it would complete the revision months ago

The U.S. Federal Aviation Administration says Boeing Co. will likely have to revise its analysis of the fixes proposed for the grounded 737 Max before the jet can be returned to service.

Boeing has prepared a draft “integrated system safety analysis” for the 737 Max’s fixes, but the FAA expects the planemaker will have to make changes before it will be approved, according to an emailed memo to Congressional staff obtained by Bloomberg News.

Photographer: Patrick T. Fallon/Bloomberg

Grounded American Airlines Boeing 737 Max planes in Tulsa, Oklahoma.

The memo helps shed light on why the fix, which Boeing initially said would be completed months ago, still hasn’t been formally submitted to FAA for approval.

“Based on our initial review, we expect that Boeing will need to revise this document prior to formal FAA submittal,” said the memo written Tuesday by Philip Newman, the agency’s assistant administrator for government and industry affairs.

Testing of new software designed to prevent the two fatal crashes on Boeing’s best-selling jet is also still underway with FAA oversight, the memo said.

The 737 Max family of jetliners was grounded March 13 after the second fatal crash within five months. In both accidents, which killed a combined 346 people, a malfunctioning safety system was repeatedly driving down the plane’s nose and pilots couldn’t respond.

Boeing is redesigning the Maneuvering Characteristics Augmentation System, or MCAS, to prevent it from activating repeatedly and is adding inputs from a second sensor to make it less prone to failure. The manufacturer and FAA will also suggest new pilot training and emergency procedures.

In addition to FAA’s review of the Boeing work on the 737 Max, a separate panel of experts known as the Technical Advisory Board is conducting its own assessment of the fix.