American Airlines President Robert Isom hosted a meeting separately with pilots and with flight attendants updating employees on the 737 MAX. At the final ‘Crew News’ employee forum of the year they walked through Boeing’s changes to the MCAS system in anticipation of the aircraft’s return to service. They’re confident in the fix to the underlying issue that occurred in both the Lion Air and Ethiopian disasters.
Changes That Have Been Made To MCAS
The story of the 737 MAX’s development is well known at this point. For reasons of cost and speed to market Boeing redesigned the 737 – which dates to 1967 – rather than starting from scratch on a new more fuel efficient narrowbody aircraft.
Boeing relocated the plane’s engines higher up and forward. This caused a tendency for the aircraft to pitch up (the nose of the aircraft would nudge up) which created risk of stall. So Boeing developed software to help pilots trim the stabilizer nose down when the plane’s angle of attack is high, flaps are up, and the plane is turning steeply. This was necessary so that the aircraft would handle in the same manner as previous 737s, and maintain the type rating so that the aircraft would be approved as just another 737 rather than starting ground up.
The flight law was triggered based on data from a single angle of attack sensor. When that sensor generated a faulty reading, the software kicked in and forced the plane’s nose down ultimately with disastrous consequences. As an option airlines could order an airline of attack disagree monitor so pilots would know if one sensor was off.
When MCAS activated it would cause a nose down pitch repetitively unless the pilot trims it out and ultimately overrode the flight law.
- AOA comparison. New software will compare data from both angle of attack sensors, and if there’s a difference of over 5.5 degrees between the sensors MCAS will be inhibited throughout the flgiht.
- Single activation. MCAS will only activate once, unless the pilot lower angle of aircraft and bring it back up (and then it would only activate once in that case). This eliminates the repetitive nose down pitch.
- Pilot maintains elevator authority Takes a snapshot of current trim setting, and won’t allow more trim so that the pilot cannot control the pitch of the aircraft.
The pilot no longer has to use the non-normal checklist for runaway stab in order to override MCAS because it becomes inhibited automatically.
When it is de-activated a caution light comes on the forward glare shield. A light illuminates on the overhead panel that says “speed trim fail” and MCAS is inhibited for the duration of the flight.
American Never Experienced Angle Of Attack Anomalies With 737s
American’s training manager points out that while there’s risk of stall at high angles of attack,
“our line pilots train that in the simulator but we never actually do that with customers.”
The airline analyzed its 7000 flights in the aircraft, before the plane was grounded, and didn’t find any issues with unusual trim or angle of attack sensor disagreements.
Right after the Lion Air accident that occurred, our safety department went back and analyzed all the focal data that they could just for the MAX aircraft and they looked for any anomalies they could find in AOA splits or unusual stab positions and I believe they only found one and that one was associated with a wake turbulence signature they saw on approach for an aircraft,
American then took the step of automating notification of any angle of attack anomaly “that would allow them to stop that aircraft and go ahead and look at it.” They did get one notification a week later and “that was just [an] anomaly”
They also did a study of 700,000 hours of Boeing 737-800 aircraft and “didn’t find any AOA issues” which is telling because it’s the same AOA part on 737s MAX and on earlier 737 Next Generation aircraft. They never had an anomaly from the part that feeds data into the MCAS system.
Where American Airlines 737s Are Now
The airline had 24 MAX planes when the model was grounded in March. Since that time 12 more have been delivered. At the time of the grounding planes were all over the American route map, the farthest away was in Barbados. Planes were brought back into the U.S. and from various cities to disparate locations for storage, and then mid-year they were moved as the grounding continued.
- 8 are in Roswell, New Mexico
- 16 at the airline’s Tulsa maintenance base
- Of the 12 deliveries, the initial 6 were stored at Boeing field, then the next 4 in Eastern Washington at Moses Lake, and the final 2 at a secondary airport in San Antonio
American Airlines Boeing 737 MAX Interior
American has orders for 100 total 737 MAX aircraft. They’re supposed to have 40 by the end of this year, 50 by the end of 2020 and 100 by end of 2026.
Bringing the 737 MAX Back Into Service
The FAA continues to work towards seeing worldwide safety agencies lift their restrictions on the aircraft at the same time. There will be a 30 day window once the FAA re-certifies the aircraft that will be needed to get planes ready and crew trained. While international safety agencies may not re-certify at the same time exactly, that period gives time in which it’s hoped other agencies will act prior to the plane’s return to commercial service.
If that doesn’t happen “there will be airspace restrictions” which suggests to me that the airline will fly the MAX based on the FAA’s evaluation, not whether world agencies sign off, although of course whether they can fly the plane outside the United States will depend on what other countries do.
The minimum equipment list for the 737 MAX is under comment now. American’s line pilots have been through 1302 training with the aircraft. The had both Dallas and Miami-based crew go through it last Tuesday. The final simulator training is the Joint Operation Evaluation Board, and once completed the FAA will reconsider the airworthiness directive for the aircraft.
They’re expecting pilots to go through computer-based training on changes to the MAX (rather than simulator training). The planes themselves will go through the Tulsa maintenance base before going back into service.
American’s President Robert Isom says there will be “no rebranding this aircraft” instead “the most important thing to restoring any kind of confidence is to simply get the aircraft back flying.”
They expect to run Dallas-Fort Worth – Phoenix charters with employees and Isom says “I can guarantee you every single senior executive and their families, including myself, will be on the first flights. ..once the FAA has said it’s ok, and once our pilots are out there flying it and out there advocating for it.. this is something that will be accepted.”
There will me a messaging campaign to customers that Senior Vice President of Flight Service Jill Surdek describes as “customer information, education, visibility, and flexibility.”