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MCAS was required to keep a linear relationship between the force applied to the flight stick and the pitch-up control moment. There is nothing magical about t
by Obi_Juan_Kenobi 7y ago
MCAS was required to keep a linear relationship between the force applied to the flight stick and the pitch-up control moment.
There is nothing magical about this linear relationship; it is an intuitive configuration for pilots, but many other aircraft do not follow it. The requirement makes sense for single-certification, but we must be clear in understanding what is actually happening with this system.
The system counters the hazard of pilots experienced in 'regular' 737s getting close to stalling without realizing, due to lighter stick inputs not having the intended effect. Any MCAS malfunction would direct their attention to this issue.
Actual anti-stall systems (MCAS is not anti-stall, nevermind some shoddy reporting) would still function if a pilot were to approach this flight envelope. This includes cabin alerts, stick shakers, etc.
The scenario where MCAS cuts out, and it's in the envelope of conditions where it actually functions, and the pilots fail to notice this, and the MCAS inputs were needed to avoid approaching a stall, and the pilots fail to correct and avoid the stall .. it's a contrived hypothetical.
MCAS is not a system that activates on a normal flight. Only in relatively extreme circumstances does it even function, and then it only seeks to make intuitive pilot behavior less likely to approach stall conditions. A good pilot monitoring airspeed, trim angle, AoA, etc. will be able to avoid a stall just as well without the system.
- mzs 7y agoLiterally a take-off where one AOA sensor fails. >The scenario where MCAS cuts out, and it's in the envelope of conditions where it actually functions, and the pilots fail to notice this, and the MCAS inputs were needed to avoid approaching a stall, and the pilots fail to correct and avoid the stall .. it's a contrived hypothetical.
- DuskStar 7y agoBut MCAS is disabled when flaps are extended, such as on takeoff?
- mzs 7y agoOn a 737 they are retracted early in the climb, typically between 1000 and 1250 feet. If the slight stick movement the pilot is accustomed to to bring the elevation down 2-3* fails to do so cause MCAS does not engage, there's not a whole lot of distance to recover from a stall then.
- DuskStar 7y ago> If the slight stick movement the pilot is accustomed to to bring the elevation down 2-3* fails to do so This is completely unrelated to MCAS, though? Since the goal of MCAS wasn't "bring the nose down" but instead "increase the pressure on the stick required to maintain a certain nose-up attitude", I'd be really flabbergasted if it was supposed to operate in a normal takeoff environment.
- linuxftw 7y agoThe goal was always bring the nose down, stick input not required.