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

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.

Photo Credit: Lee Ann Shay/Aviation Week

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.

Photo Credit: Lee Ann Shay/Aviation Week

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.

Photo Credit: Lee Ann Shay/Aviation Week

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.

Photo Credit: Lee Ann Shay/Aviation Week

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

Photo Credit: Lee Ann Shay/Aviation Week

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.

Photo Credit: Lee Ann Shay/Aviation Week

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.

Photo Credit: Lee Ann Shay/Aviation Week

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.

Photo Credit: Lee Ann Shay/Aviation Week

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

Photo Credit: Lee Ann Shay/Aviation Week

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

Photo Credit: Lee Ann Shay/Aviation Week

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…

Photo Credit: Lee Ann Shay/Aviation Week

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

Photo Credit: Lee Ann Shay/Aviation Week

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.

Photo Credit: Lee Ann Shay/Aviation Week

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