I'm certain that's not correct, everything I've read on it has said MCAS was specifically a software modifier put in place to allow the plane to respond substantially the same as a regular 737 without the larger engines, in order to avoid having to have additional training for all 737 pilots worldwide.
Most aircraft, in a "pitch up attitude" will increase their angle of attack as thrust is applied. The issue was that the MAX would do so in a more radical way than the regular 737 did, and so the software was put in place to limit that so it flew like a regular 737 as far as the pilots could see.
Conceptually, MCAS wasn't a bad idea. The execution and using it as a replacement for training and not informing pilots of the flight characteristics changes between the models was stupid.
Although to be fair my summary wasn't entirely accurate - it wasn't that a MAX was outright dynamically unstable with no control input, as I described, but rather not sufficiently stable as to cause a monotonic increase in stick force as AOA increases, which can cause the combined system of pilot + flight dynamics to be unstable since the pilot relies on stick force as an indicator.
> Most aircraft, in a "pitch up attitude" will increase their angle of attack as thrust is applied
This is both incorrect and irrelevant. Most aircraft will climb when power is applied, but will not change their AOA unless the thrust axis is off-center. To a first approximation, power controls climb rate, and stick input changes AOA. Change in behavior under different power settings has little to do with the problem with the MAX. The problem with the MAX is that at high angles of attack - i.e., when the stick is held back, causing the air to meet the wing (and the engines) at a steeper angle - the engines, which are flung forward, start producing lift of their own and produce a pitch-up moment. This means that the further the pilot pulls the stick back, the less hard they have to pull. This is a dangerous inversion that increases the control order of the system, as it breaks the usual assumption that a given stick force will result in a given AOA, more or less.
Right -- it didn't give the exact same feedback to the pilot that the regular 737 did, which was why MCAS was created. The aircraft is no more or less unstable than a regular 737.
The original 737 does exactly the same thing the Max does with respect to producing a pitch-up moment -- as does nearly every other aircraft. It's just not nearly as pronounced as the Max is.
I'm sorry, none of that is correct. Did you read my link? The aircraft doesn't meet FAA regulations without the MCAS.
>The Boeing 737 MAX MCAS system is there ONLY to meet the FAA longitudinal stability requirements as specified in FAR Section 25.173, and in particular part (c) which mandates "stick force vs speed curve:, and also FAR Section 25.203 — "Stall characteristics".
I'm certain that's not correct, everything I've read on it has said MCAS was specifically a software modifier put in place to allow the plane to respond substantially the same as a regular 737 without the larger engines, in order to avoid having to have additional training for all 737 pilots worldwide.
Most aircraft, in a "pitch up attitude" will increase their angle of attack as thrust is applied. The issue was that the MAX would do so in a more radical way than the regular 737 did, and so the software was put in place to limit that so it flew like a regular 737 as far as the pilots could see.
Conceptually, MCAS wasn't a bad idea. The execution and using it as a replacement for training and not informing pilots of the flight characteristics changes between the models was stupid.