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It was much worse than a lack of training. Prior to the first crash in Indonesia, MCAS was not mentioned in the formation to the pilots. Boeing has asked the F
by idoubtit 7y ago
It was much worse than a lack of training.
Prior to the first crash in Indonesia, MCAS was not mentioned in the formation to the pilots. Boeing has asked the FAA to remove it from the documentation. The FAA did not know that the MCAS was totally different from what Boeing had initially planed, so they agreed.
After the crash, Boeing published new instructions that mentioned MCAS. But they were of no use for the Ethiopian crash. As you wrote, turning off MCAS also turned off stabilisation, and manual control was not possible because of the excessive speed. The pilots did understand that, so they enabled the electric trim again. Unfortunately, this activated the MCAS which send the plane downside 10 seconds later. They had no way out.
- phire 7y agoI have a personal theory (based on the graphs from the reports from both crashes) that once the stabilisers go far enough out of trim at high enough speeds, that the even electric trim motor isn't powerful enough to move the stabiliser. In both crashes, after repeated activations of MCAS has pushed the stabiliser almost fully down, we see the pilots do two quick presses of the trim up button. The graph shows the stabiliser barely moving (much less than a press of the same length earlier in the flight). I suspect the pilots pressed the trim up button, heard a loud noise from the electric motor straining, or a fuse popping, or something? So they stopped pressing trim up. Even worse, only trim up was failing, MCAS was still able to command more trim down.