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The thing about the 737 is that you have massively powerful engines essentially hanging from the underside of the wings, and the wings are in a low-wing configu
by na85 8y ago
The thing about the 737 is that you have massively powerful engines essentially hanging from the underside of the wings, and the wings are in a low-wing configuration (i.e. they sprout from the bottom of the fuselage and not the top like a Cessna).
Imagine you're on final into a busy airport and you have to abort your descent because $reasons. If you slam the throttles forward, the thrust is all below the aerodynamic centre of the aircraft, so you have a net nose-up pitching moment created. In other words, when you slam the throttles forward the aircraft tends to nose up. A 737 pilot told me recently that in a take-off/go-around situation you actually need to push the yoke forward to restrain the aircraft's nose-up tendency until you can re-trim for climb.
MCAS was introduced because the new engines on the MAX, essentially, make the airframe more dangerous at high Angle of Attack than the previous generations of the 737, and so MCAS was intended to automagically keep pilots from entering the dangerous regime.
MCAS was required in order to keep to the "zero training delta" commitment. The solution might be removing MCAS, but that will/would require more pilot training which would essentially render the MAX a completely new aircraft as far as regulation is concerned.
- dingaling 8y ago> the thrust is all below the aerodynamic centre of the aircraft Just like 95% of airliners. In fact the Max engine thrust line is higher and closer to the datum than most. The Max's problem is not thrust line, it is additional lift generated by the forward-mounted engine nacelles at high AoA which reduces stick-load and makes pitch-up to a stall likely. Nothing to do with thrust.
- na85 8y ago>Just like 95% of airliners. In fact the Max engine thrust line is higher and closer to the datum than most. Correct. >The Max's problem is not thrust line, it is additional lift generated by the forward-mounted engine nacelles at high AoA which reduces stick-load and makes pitch-up to a stall likely. Nothing to do with thrust. Nothing you've written here contradicts what I wrote previously, so I'm not sure if you're just aggressively agreeing with me, but I'll assume that this is the case. Yes, the aircraft is dangerous at high AoA, as I wrote in my previous comment.
- rocqua 8y agoIs it the ammount of lift of the nacelles or the forward position of this extra lift?
- usrusr 8y agoBoth: the position changed because the size changed.
- inferiorhuman 8y agoThe Max's problem is not thrust line, it is additional lift generated by the forward-mounted engine nacelles at high AoA which reduces stick-load and makes pitch-up to a stall likely. Nothing to do with thrust. Pitching up on thrust was a problem with the 737 Classic, why wouldn't it be a problem on the MAX?