Gallery: American Airlines' Modified 737MAX Before Return To Service

Lee Ann Shay December 10, 2020
American Airlines Boeing 737 MAX at Tulsa base

American Airlines Boeing 737 MAX at Tulsa Base

Since the FAA’s grounding mandate in March 2019, American Airlines’ 24 Boeing 737MAX aircraft underwent 64,000 labor hours as part of a storage plan that would allow the airline to reactive the aircraft fairly quickly. American’s maintenance base in Tulsa, Oklahoma, has led the effort.

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CFM Leap-1B Engine on MAX

As part of the intermediate storage plan, the airline maintains 737 MAX aircraft every 10 days, which includes running the CFM Leap-1B engines. A checks were completed every 60 days.

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Resume Scheduled Service Dec. 29

American will be able to resume scheduled MAX service on Dec. 29, less than six weeks since the FAA issued the airworthiness directive outlining steps needed for return to service.

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MCAS Software Update

An FAA airworthiness directive dated Nov. 18 mandates updating flight control computer (FCC) software to modify the MAX’s maneuvering characteristics augmentation system (MCAS) and updating MAX display system (MDS) software.

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Software Update Process Like Computer Reboot

American says the update takes about six hours—four hours for the software to upload and two hours to perform functional tests.

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Data Transfer Unit Port

The software runs through a laptop in the cockpit and uploads through the data transfer unit port. American hopes to complete the software updates in January 2021.

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Next 10 MAXs

For the 10 new MAXs that American plans to take in December, Boeing will have already updated the software and it will be AD modification compliant, says Erik Olund, the airline’s managing director base maintenance.

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Wiring Mods

Wiring modifications involved changing parts of the flight control system wire routing so there is space between the horizontal stabilizer trim arm wiring and the horizontal stabilizer trim control wiring. They originally were either routed in the same bundle or in different bundles that were co-clamped.

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Wire Bundles

These are modified wire bundles inside the electrical and electronics compartment…

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Electrical and Electronics Bay

...and systems such as the Teledyne Control digital flight data acquisition unit in the electronics compartment.

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Two AOA, Captain's Side

All of American’s 737 MAX aircraft are equipped with dual angle of attacks (AOA). EASA requires two AOAs for certification but the FAA only requires one. Here is the one on the captain’s side…

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AOA, First Officer's Side

..and here is the one on the first officer’s side.

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Operational Readiness Flights

After the maintenance staff has completed the modifications at American’s Tulsa base, each aircraft undergoes six hours of ground test and four to five hours of flight tests.

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MAX in Flight

Onboard a non-revenue MAX flight from Tulsa to Dallas Ft. Worth on Dec. 2. When asked why American kept the MAX in what it dubbed “flyable storage,” Olund said the airline never thought the aircraft would be grounded for 20 months.

Photo Credit: Lee Ann Shay/Aviation Week

Aviation Week toured American Airlines' maintenance base in Tulsa, Oklahoma, on Dec. 2 to see how the airline was modifying and preparing its Boeing 737MAX aircraft for return to service, after about 20 months of grounding following FAA's order.

Lee Ann Shay

As executive editor of MRO and business aviation, Lee Ann Shay directs Aviation Week's coverage of maintenance, repair and overhaul (MRO), including Inside MRO, and business aviation, including BCA.