Flying on a MAX8 for the 1st time

My recent trip to the States and back involved connections in Auckland (NZ) and Houston (TX). This time I flew United on the Houston-Atlanta sectors. Outbound it was a good old B737NG workhorse, but the real surprise came when I learnt that I have to fly on a B737 MAX8 on my way back home. Over the years, I have been a passenger/crew member on more commercial models that you can poke a finger at, but never on a MAX. And I have to admit, as a former B737 chief engineer, I was a bit uneasy about the prospect.

Background

If you are not familiar with the ongoing debacle at Boeing, let me sum it up very briefly:

1. On 29 Oct 2018, a MAX8 operated by Lion Air crashed into the Java Sea shortly after takeoff, killing all crew and passengers on board the flight.

2. In less than five months, on 10 Mar 2019, a MAX8 operated by Ethiopian Airlines crashed into the ground near Bishoftu (a town in central Ethiopia) only 6 minutes after takeoff. Tragically, all passengers and crew members lost their lives.

The two fatal crashes were the result of a new addition to the B737 flight control system: the Maneuvering Characteristics Augmentation System (MCAS). The original MCAS design depended on angle-of-attack (AOA) data from a single AOA sensor that had no backup. The critical AOA sensor failed during both accident flights, giving false AOA input data to the MCAS system which, in turn, commanded a series of forceful nose-down inputs. The accident pilots were fighting MCAS but could not recover their airplane.

Designing a safety-critical system on a Part 25 transport category airplane - with a known catastrophic failure scenario and no built-in redundancy - is unheard of in modern aerospace engineering and violates fundamental system safety principles. To make matters worse, Boeing management decided to remove the relevant sections from the Flight Crew Training Manuals, essentially hiding the existence of MCAS from airline pilots. As a former Boeing principal engineer, it is hard to imagine what corporate safety culture (or lack thereof) would make a person propose such an idea, let alone approve and certify the design with such a critical single point-of-failure.

Is the MAX safe now?

After those two crashes, Boeing initially blamed the pilots who operated the accident flights. Needless to say, I was less than impressed with that misguided approach. Five years later, Boeing promised to reinvent itself as a company that values it’s engineering excellence, having lost two CEOs in the meantime. In line with industry standard practices, design changes were rolled out by Boeing and the FAA made them mandatory for all airlines operating B737 MAX models. It is beyond the scope of this blog entry to go into the details of the relevant design changes that were incorporated to fix the flawed MCAS system architecture. Let me provide a link instead, for your reference:

➜ Bjorn Fehrm (Leeham News) released a series of MCAS-related articles, here is a good summary from 2020: Why is the 737 MAX safe now

Based on what information is available in the public domain, I agree with Bjorn’s assessment that the MCAS fix is effective and the basic B737 flight control system design has a relatively good in-service record. ¹

In summary, I walked the talk when I boarded the MAX8 in Houston a few days ago. I only came to realise after the flight that my apprehension had more to do with the quality of workmanship that goes into building Boeing airplanes these days, but that is probably a topic for another blog post, not this one.