MAX Effort: Returning the Embattled B-737 MAX to Service

MAX Effort: Returning the Embattled B-737 MAX to Service

MAX Effort: Returning the Embattled B-737 MAX to Service

Photo Courtesy of Boeing


Airlines have always been a cyclical industry. And despite assertions several years ago that they would “never lose money again,” several unpredictable events resulted in a downturn that is causing a potentially E.L.E. (Extinction Level Event) among some part 121 carriers: The worldwide grounding of the B-737 MAX followed by a cataclysmic drop in load factors due to COVID-19. 

These events precipitated massive airline furloughs, personal financial hardships, a huge drop in shareholder value, loss of scheduled air service to domestic and international destinations and collateral damage to related travel/leisure business and industry. Even if (this article was written in late September) another economic relief package arrives, airline employee protections will once again expire – this time in March. And it’s anyone’s guess if or when business and leisure travel will return to profitable levels post-COVID. The MAX, however, will be slowly returning from its exile as the world’s recovery from COVID also slowly unfolds. 

What Could Possibly Go Wrong!
Perhaps, similar to NASA’s previous cultural, project management issues, several high visibility events at Boeing (B-737 MAX flight control and B-787 quality and “tool control”) sent Boeing into an inverted flat spin. When engineers observed a tendency for the 737 MAX nose to pitch upward during a specific extreme maneuver, and after other efforts to fix the problem failed, the solution was a piece of software – the Maneuvering Characteristics Augmentation System (MCAS). MCAS adjusts the horizontal stabilizer trim to push the nose down when the aircraft is operating in manual flight, with flaps up, at an elevated AOA. 

Boeing originally designed the MCAS as a simple solution with a narrow scope, then altered it late in development to expand its power. Engineers had allowed MCAS to trigger on the input of a single sensor instead of two, as considered in the original design. And pulling back on the control yoke would not override MCAS activation. Boeing calculated the probability of a “hazardous” MCAS malfunction to be very unlikely and that there would be little risk in a runaway MCAS “event” in part because they believed pilots would respond to an unexpected activation as they had been trained for years – with the runaway trim procedure.

What’s A Mother (or Airline) To Do
In summary, the following steps had to be taken before any 737 MAX will be allowed to operate revenue flights:

  • Installation/Verification of Flight Control Computer (FCC) Operational Program Software (OPS)

Note: Boeing updated the FCC software to eliminate MCAS reliance on a single AOA sensor signal by using both AOA sensor inputs and changing flight control laws to safeguard against MCAS activation due to a failed or erroneous AOA sensor.

  • Airplane Flight Manual (AFM) Revisions
  • Minimum Equipment List (MEL) Provisions for Inoperative Flight Control System Functions
  • Installation/Verification of MAX Display System (MDS) Software

Note: Boeing has revised the AOA DISAGREE alert message implementation to achieve the original design intent to be standard on all 737 MAX aircraft.

  • Horizontal Stabilizer Trim Wire Bundle Routing Change
  • AOA Sensor System Test
  • Operational Readiness Flight
  • Pilot Ground School and Simulator Training

Returning Pilots to the MAX
As of the 6th of October, the following is a summarized list of pilot training requirements from a NPRM (Notice of Proposed Rule Making – emphasis added by this author):

Multiple flight deck alerts during non-normal conditions, Automatic landings, Enhanced Digital Flight Control System (EDFCS), 737 MAX flight control system: The Elevator Jam Landing Assist system and the Landing Attitude Modifier (LAM), MAX FCC/MCAS ground training,HUD, the 737 MAX gear handle. This training can occur in either a full flight simulator (FFS) or airplane. Flight training must ensure appropriate AFM limitations are addressed and complied with. 

Stabilizer trim must emphasize the following throughout the airspeed range during manual and electric trim operations:

a) Manufacturer recommended procedures for the proper use of main electric and manual stabilizer trim during normal and non-normal conditions;

b) The different manual trimtechniques recommended by the manufacturer; and

c) The effects of theair loadson the stabilizer and the resulting trim forces in both the nose-up and nose-down directions.

Electric and manual stabilizer trim operation during non-normal conditions training.

Runaway stabilizer.Training must emphasize runaway stabilizer recognition and timely pilot actions required by the Runaway Stabilizer NNC (Non-Normal Checklist). Demonstrate control column functionality and its effect on a runaway stabilizer condition. Emphasize the need to trim out forces on the columnprior to selecting STAB TRIM cutout. Training must include scenario-based training where a single malfunction results in multiple flight deck alerts that requiretimely pilot actionto include recognition and interpretation of the non-normal condition and prioritization of the required pilot actions.

Lord Forgive Me and Knock on Wood 
My final “R-9” recurrent training this past September was accomplished in one of my carrier’s MAX sims and in one of CAE’s, both in DFW. Prior to this training event, I had never been in the cockpit of the MAX aircraft or simulator. We accomplished all of the traditional dial-a-disaster events – most at night, some in ice, strong winds, low visibility and many with system malfunctions or failures. And I’ve struggled with a way to describe the MAX runaway trim and MCAS scenarios, checklist procedure and aircraft recovery process to our T &T readers without disparaging the reactions, or slow reactions, of the crews’ that resulted in two fatal crashes. 

For over 45 years, I have experienced or trained in GA, fighters and airliners for approach to a stall, full stalls, spins, flight control malfunctions (like split flaps and rudder hard-overs), low altitude wind shear and high-altitude unusual attitude recoveries and deep stalls in the F-16. And Lord forgive me for saying, and knock on wood, but of all the aircraft-control training events, the B-737 MAX MCAS failure mode is benign. It’s a relatively subtle event, which could make it difficult to recognize in the first three to five seconds, but it progresses slowly, is simple to control once recognized, and the checklist procedure is effective. I will acknowledge, however, if recognized late or the checklist procedure is delayed, executed improperly or out of order, the aircraft can become extremely (I say again, extremely) difficult to handle, even for two pilots.

Return to Service Schedule
Boeing expects a return to service date in the fourth quarter of 2020. Once the aircraft is recertified, the plane maker is planning to deliver its 400-plus stored 737 MAX aircraft within a year. It’s estimated that total 737 MAX deliveries for the 2020 to 2023 period will be at least 1,700 aircraft lower than expected at the beginning of 2019. This is a reduction of about 50 percent as compared to previous expectations due to the grounding and the pandemic’s effect on the global airline industry as well as world economies. Carriers will bring already-delivered aircraft on-line in the early months of 2021. 

Despite the news that my carrier is delaying pilot training in the MAX, they have begun the FAA mandated process of re-training crews via e-mails, crew bulletins and using MAX simulators for recurrent training. They are also scheduling our 1,700 or so B-737 pilots for an extra two-day MAX-specific training event consisting of several hours of ground school and a two-hour simulator session. This training event, originally scheduled to start in November, will now occur over December, January and February. Currently, my carrier will use the one MAX sim it owns and several from CAE in order to complete this training. The jet is expected to appear on our February 2021 schedule for revenue service.

“I do not think that there is any other quality so essential to success of any kind as the quality of perseverance. It overcomes almost everything, even nature.”

                 – John D. Rockefeller

Airlines and airplane manufacturers, hotels, the leisure industry, restaurants, bars, gyms, hair salons, schools, municipalities, theme parks and a myriad of both related and unrelated businesses are all suffering. Perhaps the return of the MAX and a vaccine for COVID, both potentially occurring in Q1 of 2021, will be the impetus to give us the hope to persevere in order to overcome and recover from everything, even nature. Mr. Rockefeller thought so. 

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