> why it would continue to drive the nose of the plane down even when the pilot is reefing on the stick to pull up
well this other crash was caused by a pilot puling up a plane all the way to its ceiling and stalling it, so there's that, so things can go wrong whether if you do and if you don't allow for easy control overrides.
the trick seems to find the right balance to relinquish control only when appropriate, so it seems that proper documentation, checklists, training and maintenance are crucial.
instead looks like to have had deficiencies in all those elements, one way or another (except the checklist itself which wasn't followed).
The AF 447 crash is one of the reasons MCAS was created. It's the exact scenario MCAS was designed to prevent: High altitude, high-speed, nose-up stall. This was more likely than the NG and dinosaur generations of 737 due to the engine relocation forward and up (causing a pitch-up moment due to thrust).
AF 447 should never have happened. The copilot crashed the plane, and the pilot and pilot on break had no indication or feedback that he was holding the stick back (crashing the plane by causing a stall). There was no feedback, and the controls deferred to his inputs when the pilot was trying the opposite command (which would have saved the flight). On top of this, the stall warning buzzer was turning off when they were so deep into the stall that the airspeed dropped below a certain threshold, and every time the nose was pitched down and airspeed increased, the buzzer came on again.
Airbus has a controls feedback, stall buzzer parameters, and training problem. 447 should never have gone down.
MCAS strikes me as the low airspeed variety of stall risk case. The high airspeed case is rare, and trained for aerobatics and flight instructors. The low airspeed case is taught on day 2 to student pilots, both power on and power off varieties. MCAS is reported to not take airspeed into account, therefore it must apply a one size fits all correction, which if useful for low airspeed approach to stall would seem to be overly aggressive for high airspeed.
AF 447 airspeeds were regularly below 60 kt. That's not a high airspeed stall. The final report is ~223 pages long, it's rather complicated to summarize, BEA blame practically everyone for something including weather, software, simulators, training, and pilots. As a pilot, some of the Airbus system behaviors in this case really piss me off to read, just how aggregiously badly designed it is when it gets confused, papered over by dumping the consequences of failed automation and the ensuing alternate laws onto the pilots. The pilots' job is system admin and troubleshooter. If they fail, they will be partly blaimed no matter what, because that's the job.
From the AF 447 final report: a) Both pilots were shocked by the autopilot disconnect. b) Reconnect of autopilot prior to 30 seconds of stabilized airspeed indication can result in pitch runaway and an unsafe condition. c) stall warning sounded continuously for 54s, neither pilot referenced the warning or stall buffeting. d) absence of any training, at high altitude, in manual aeroplane handling and in the procedure for ”Vol avec IAS douteuse” which you allude to. e) theoretical training for the pilots associated the buffet with stall and overspeed, even though in reality buffet is only encountered with stall. e) when there are no (software) protections left, the aeroplane no longer possesses positive longitudinal static stability even on approach to stall.
It's just crazy, only somehow partly neutralized by the statistical fact air travel is still really safe!
AF 447, last recorded values were a pitch attitude of 16.2 degrees nose-up, roll of 5.3 degrees to the left, a vertical speed of -10,912 ft/min, ground speed of 107 kt, and full power. And for the last 11 seconds "sink rate" and "pull up" warnings sounded. No emergency transmission sent (quite common).
There was both an audio and a visual indication of DUAL INPUT (light on the panel + "dual input" announced verbally). The co-pilot commanded priority take-over (from the pilot, who had just second previously done the same) without announcing it. This would have been clear if they looked at the panel that shows which side has priority, but in that confusion, their attention would've been elsewhere (airspeed and bank angle mostly).
>There was no feedback, and the controls deferred to his inputs when the pilot was trying the opposite command (which would have saved the flight).
I've never seen a reliable source for the claim that the two pilots at the controls were pushing the stick in opposite directions for any extended period of time. What's the primary source for this info?
well this other crash was caused by a pilot puling up a plane all the way to its ceiling and stalling it, so there's that, so things can go wrong whether if you do and if you don't allow for easy control overrides.
https://en.wikipedia.org/wiki/Air_France_Flight_447#Third_in...
the trick seems to find the right balance to relinquish control only when appropriate, so it seems that proper documentation, checklists, training and maintenance are crucial.
instead looks like to have had deficiencies in all those elements, one way or another (except the checklist itself which wasn't followed).