Boeing 737 Crash Caused By New Safety System Pilots Weren’t Told Existed

Modern aircraft are staggeringly complex. There’s a complex interconnected web of systems controlled by both the pilot and co-pilot and the onboard computers dedicated to keeping the airborne meat-filled-tube-with-wings-attached firmly in the air. When an aircraft is lost, it’s an international tragedy. Modern aircraft typically don’t fall out of the sky without warning, which is why the Lion Air 610 crash on October 29 that killed 189 people was such an unusual event. New information suggests the blame for that event in Indonesia rests squarely on Boeing’s shoulders.

FAA officials and airline pilots are zeroing in on a new anti-stall system as being responsible for the crash, The Wall Street Journal reports. Workers on an oil platform near where the airline slammed into the water report that it struck at a steep, nose-down angle. That’s significant, because a week after the crash, Boeing distributed a warning to airlines worldwide that a new anti-stall system on the 737 MAX 8 and 737 MAX 9 could cause the aircraft’s nose to suddenly drop, resulting in a steep dive. This can occur even when the aircraft is under manual control and when pilots don’t expect the flight computer to override their actions.

It gets worse. According to Indonesian investigators and multiple pilot organizations, this scenario isn’t covered in the 737 MAX 8 or MAX 9 flight manual and was not taught to pilots. Bloomberg reports that none of the documentation for the aircraft explained the existence or function of the system. Boeing has stated that the Lion Air 610 received “erroneous input” from one of its AOA (angle-of-attack) sensors, which was presumably at least partly responsible for the flight computer’s decision to drop the aircraft’s nose and engage the stall prevention system. But without proper training, the flight crew on the aircraft would not have known how to recover the plane. Previous 737s did not push the nose of the aircraft down as part of stall prevention.

Bloomberg notes that “A long-standing procedure taught to pilots could have halted the dive, according to the regulator and the manufacturer. The FAA ordered airlines to add an explanation into flight manuals,” but does not state what the procedure was. In a situation like this, knowing the aircraft inside and out is critical. Lion Air 610 had only been in the air for 13 minutes and had already requested permission to return to Jakarta and land. We can assume, therefore, that the aircraft was well below its target altitude when the steep descent began. An aircraft in emergency descent can drop quickly; this Quora link suggests 6,000 – 7,000 feet per minute is not uncommon. While we don’t know what nose angle the anti-stall system set or the altitude of the aircraft, a little envelope math suggests the pilots had very little time to pull the aircraft out of the dive.

In that kind of scenario, there may only be time to try a single method of recovering the plane, and the Lion Air pilots obviously guessed incorrectly. They shouldn’t have been guessing at all.

The WSJ also states that one of the selling points of the 737 MAX, according to Boeing, was that pilots wouldn’t need any additional simulator time to learn the aircraft, and that the company opted not to disclose additional technical information in the belief that doing so would “inundate” pilots with technical details they neither needed nor could grasp.

Feature image by Wikipedia.

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