Several pilots warned of problems with the autopilot features on Boeing 737 Max aircraft months before this weekend’s Ethiopian Airlines crash, which killed 157 people.
The pilots noted their concerns on a database known as the Aviation Safety Reporting System, which offers pilots a place to describe their experiences without repercussions. The database contributors aren’t identified by name or airline.
The pilots’ complaints shed light on a subject of growing worldwide interest. Many countries have grounded Boeing’s 737 Max 8 model — one of its newest and most fuel efficient commercial aircraft — including Australia, China, Europe and the United Kingdom.
One pilot reported in November that shortly after a normal takeoff, as he engaged the aircraft’s autopilot feature, the plane began quickly descending and the ground proximity warning system called out “Don’t sink! Don’t sink!”
“I immediately disconnected AP (autopilot) and resumed climb,” the pilot wrote, adding that he and his first officer began talking about what had just happened.
“Now, I would generally assume it was my automation error, i.e., aircraft was trying to acquire a miss-commanded speed/no autothrottles, crossing restriction etc., but frankly neither of us could find an inappropriate setup error (not to say there wasn’t one),” the pilot wrote. “With the concerns with the MAX 8 nose down stuff, we both thought it appropriate to bring it to your attention.”
The United States and Canada are among the small number of countries still allowing the 737 Max 8 to land at their airport. Fort Worth-based American Airlines flies 24 of the 373 Max 8 aircraft, and Dallas-based Southwest Airlines flies 34 of them.
The Fort Worth Star-Telegram searched the NASA database and found three complaints.
The Dallas Morning News, which originally broke the story about the pilots’ complaints, reported finding five complaints about the Max 8.
In another incident in November, a pilot reported a problem that also began just after takeoff, moments after the captain engaged autopilot.
“Within two to three seconds the aircraft pitched nose down bringing the VSI (vertical speed indicator) to approximately 1,200 to 1,500 FPM (feet per minute),” the pilot wrote. “I called ‘descending’ just prior to the GPWS (ground proximity warning system) sounding ‘don’t sink, don’t sink.’ The Captain immediately disconnected the autopilot and pitched into a climb. The remainder of the flight was uneventful.”
Finally, the pilot added, “We discussed the departure at length and I reviewed in my mind our automation setup and flight profile but can’t think of any reason the aircraft would pitch nose down so aggressively.”