Originally Posted by
esoterex
What about the 2010 737 crash in Lebanon? Looking at that accident report it does not put ET in a good light.
You can‘t draw conclussions on cherry-picked data. This way you introduce bias to the sample and of course data confirms your bias!
that said, ET409 final report is a fascinating read. I‘m just going over it and what standa out is:
- captains behavior seems to indicate he was somehow incapacitated (eg slow and wrong reactions to bank angle); what‘s more, he complained he could not sleep due to evening meal! It could be he was totally zombied due to insomnia
- twice on cvr recording he‘s asking about „what‘s that“ to which FO doesnt even react... insomnia induced hallucinations? Report offers no explaination
- he hand flew which was against SOP for IMC
now for the interesting part:
- TO trim selection was wrong for unexplained reasons(??)
- period of 3” a trim up which resulted in an increase of pitch trim from 7.9 to 8.8 units and an airspeed of 196 Kts. That manual trim command was the last one commanded by the crew during the flight and resulted in the aircraft computer memorizing that speed as the one the crew wanted to maintain, despite the different speed selected on the MCP19.- AP could not be engaged due to column forces against trim
- toga was selected
- At the same time, as the speed started to increase beyond 195 Kts, the speed trim commanded a nose up trim input increasing the pitch trim from 8.2 to 9.3 units at 00:40:37, resulting in a further increase in the aircraft pitch up tendency. The crew did not take any action to re-trim the aircraft to the desired speed, so, once the nose down pressure was released on the control column, the aircraft pitch started to increase again and became close to 30° up
in essence, possibly very similar to mcas, but in reverse: sts remebered a certain speed and stalled the airplane trying to maintain it. With toga selected sts had to compensate plenty of power with trim.
Wow.
I don‘t know if last manual trim also sets target speed for mcas? In case of ET with full thrust, wouldn’t that set higher target sped with every manual up trim? And as soon as you pull up and reduce speed you’d get hit with more trim to get to the target speed? That certainly would escalate very quickly once speed starts building up and could explain why the crews could not handle the plane. But this could also be nonsense, I don’t know how the systems behave.