[ReGenGen]

Other airliners w/ large turbofans have a pitch-up under climb/thrust characteristics. (like B777) We don't know if 737 MAX's pitch-up stall handling characteristics are really bad -or- just different from older 737's. MCAS was put in place to allow the MAX to be type certified w/ other 737's so 737 pilots could fly the 737 MAX and vice versa. (Airline pilots can only hold 1 type certification at a time.)

[chipsa]

Where'd you get the idea that pilots can only hold one type rating at a time? One pilot managed to acquire 105 at one time (and is in the Guiness Book of World Records for that).

Also, MCAS wasn't put in place to allow the MAX to be type certified w/ other 737s. It was put in place to allow it to be certified at all. It's a hack to ensure the force on the stick continues to increase with increasing angle of attack, which is a certification requirement.

[acqq]

> MCAS was put in place to allow the MAX to be type certified w/ other 737's

But the expected behavior which MCAS was to provide was not something invented only for "other 737's." Whichever plane would behave as the MAX behaves without MCAS turned on would also be rejected from certification.

Only Boeing being silent about MCAS is the effect of the goal of "avoiding re-certification."

> We don't know

I can't agree to that. Based on the above, I think it is obvious that we do know: 737 MAX without any MCAS-like help is dangerous to fly according to the security expectations which weren't specially invented for 737 MAX.

[lmm]

> But the expected behavior which MCAS was to provide was not something invented only for "other 737's." Whichever plane would behave as the MAX behaves without MCAS turned on would also be rejected from certification.

No, it would have been a perfectly certifiable plane with a particular set of handling characteristics (including 777-like pitch-up). It just wouldn't be a 737, and would require its own type certificate. No-one's suggesting that large turbofan aircraft with pitch-up behaviour are inherently unsafe when flown by pilots appropriately trained and certified for them - otherwise the 777 would be grounded.

[acqq]

> No-one's suggesting that large turbofan aircraft with pitch-up behaviour are inherently unsafe

It is as long it keeps 737 MAX body and engines and doesn’t have something like MCAS I.e. Inherently unsafe under conditions under which MCAS was supposed to turn on when properly functioning.

The certification requirements are the result of the clear safety goals not something invented “just so.”

[salawat]

MCAS was a type certificate hack.

The poster you're responding to is right; there isn't anything wrong with the behavior given the right training.

It's just that the investment in that training, and extra certification hoops to jump through would have made WhateveroModelNumberus MAX a non-starter.

It had to be a 737 to work at all.

[acqq]

> there isn't anything wrong with the behavior given the right training.

The behaviour without MCAS on 737 MAX is that minimal movements of pilot’s controls effectively activate what would be considered “amplification” of nose up movement, resulting in an uncontrollable plane and sure crash.

It’s definitely not something that pilots or passengers should be exposed to: being punished for approaching more dangerous position by plane forcing a deadly outcome.

Training pilots to not to move even minimally the controls in the “wrong” direction is maybe technically possible but in practice still totally wrong: It’s comparable to what Boeing told everybody before Ethiopian crash, and their attempts to blame the pilots. In reality, the pilots had almost no chance to rescue themselves and the plane.

In engineering the “positive feedback loops” (amplification of control inputs) are bad the “negative feedback loops” (correction of the input) are good.

The functioning MCAS provides a correction. The plane without MCAS amplification. Badly functioning MCAS also amplification and crash. That's why the wrong behavior was regulated, and that's why it had to be fulfilled for the certification. It’s that easy.

To convince me that 737 MAX without the "properly functioning MCAS" isn't inherently dangerous under higher angles of attack you'd have to provide some explicit proofs.

[salawat]

727 had about the same issue. Interactions with high lift devices would cause major problems on approach to stall.

The FAA certified it anyway. The U.K. gave it conditional certification contingent on the addition of a stick-pusher to be able to operate in U.K. airspace. See the Royal Aeronautics Society D.P. Davies Interview, specifically the 727 one.

There was quite a bit of controversy amongst test pilots at even granting the certification, seeing it as setting a precedent that would lead to a slippery slope that would culminate in less and less airworthy designs.

Nevertheless, the certification authorities accepted the argument that as long as instabilities could be countered by technological means, it would be acceptable.

Let me clarify though, that without MCAS, a responsible pilot would definitely be constrained to a much thinner envelope, but within that thinner envelope, the plane can fly just fine.

The deployment of flaps, also takes the plane out of a regime where MCAS is a factor.

So both legal, and practical precedent for it exists. Given additional training of course.

[caconym_]

> To convince me that 737 MAX without the "properly functioning MCAS" isn't inherently dangerous under higher angles of attack you'd have to provide some explicit proofs.

I am legitimately curious, do you have any explicit proofs of the converse, that (as you say) "the behaviour without MCAS on 737 MAX is that minimal movements of pilot’s controls effectively activate what would be considered “amplification” of nose up movement, resulting in an uncontrollable plane and sure crash"?

The standard should be that a an unimpaired pilot properly trained in flying the aircraft will normally (practically) be in no danger of a "sure crash".