4 ms·

All pilots of Boeing aircraft know that when the autopilot is off, there is no automation between the controls and the control surfaces - until the 737 Max chan

All pilots of Boeing aircraft know that when the autopilot is off, there is no automation between the controls and the control surfaces - until the 737 Max changed that. The MCAS system is only active when autopilot was off, a big change. Imagine the faulty AoA sensor is causing the aircraft to hunt around to different altitudes. The pilot switches off autopilot by just applying force to the controls and suddenly the plane starts pitching down.

lsh123 8y ago
Not a Boeing driver, but in a few GA aircraft I flew, runaway trim can happen regardless of AP on/off status.
- ams6110 8y ago
  Yes it can happen due to a jammed switch, relay, wiring short, etc.
foldr 8y ago
>All pilots of Boeing aircraft know that when the autopilot is off, there is no automation between the controls and the control surfaces This isn't even approximately true. Pretty much all passenger jets since the 50s and 60s have had yaw dampeners, for example.
- asmithmd1 8y ago
  True, but a yaw dampener is sort of like a steady cam, it isn't going to over-rule a pilot's rudder input. Put yourself in the seat of a pilot who has flown an electro-hydraulic 737 for years. Something "funny" seems to be going on with the trim, so you take control and the trim seems to be working perfectly while you manually toggle it, but then the MCAS kicks back in after 5 seconds and tries to push the nose down again. This kind of behavior is coming from a system Boeing did not tell the pilots about.
  - zaroth 8y ago
    > This kind of behavior is coming from a system Boeing did not tell the pilots about. True for the first crash. However, no longer true by the time of the second crash.
    - pishpash 8y ago
      Still an unnecessary cognitive load.
    - myrandomcomment 8y ago
      I cannot agree more. After the 1st crash you would think every pilot would have become familiar with this system and how to override it. The stuff that has come out from the most recent crash shows that the pilot was read through manuals trying to understand what was happening. Given the most recent crash, why would he not think, hey lets disable this new system because my plane is acting in the exact same way. I am not saying that Boeing is not at fault for poor training or documentation but if I was flying the same plane as one that recently crashed I know I would have known everything I could about that crash before I lifted off in that same model.
      - faizmokhtar 8y ago
        Not likely. When the first crash happened Boeing try to shift the blame to Lion Air citing lack of maintenance and what not.
      - jiqiren 8y ago
        As many report have already mentioned: the MCAS is not in the manuals.
      - CaptainZapp 8y ago
        After the first crash Boeing should have pulled that plane out of service, period. It shouldn't be up to pilots to try to find workarounds for rotten engineering. The first crash can be chalked up to engineering errors, corner cutting and the desire not having to retrain and recertify pilots. The second crash is outright criminal by Boeing, for not immediately pulling that plane out of circulation after the Lion Air disaster. Regardless of the cost (which will be much, much more expensive after crash 2). Their cozy relationship with the FAA also didn't help and I hope the people responsible pay dearly for that. Throwing the pilots under the bus is how they tried to handle that PR desaster. Doesn't seem to work well, though.
ekianjo 8y ago
You can however disable the MCAS and it is apparently well documented in the pilot training material. When the trimming wheel acts strangely this is a sign that something may be going wrong and this is part of what pilots need to know when flying this aircraft. Now whether or not such information is widely known among all pilots is another matter altogether.
- raverbashing 8y ago
  MCAS wasn't, runway trim was, however, I don't believe the pilots would expect/recognize a runway trim failure on the occasions that MCAS would fail

lsh123 8y ago

Not a Boeing driver, but in a few GA aircraft I flew, runaway trim can happen regardless of AP on/off status.

ams6110 8y ago
Yes it can happen due to a jammed switch, relay, wiring short, etc.

foldr 8y ago

>All pilots of Boeing aircraft know that when the autopilot is off, there is no automation between the controls and the control surfaces This isn't even approximately true. Pretty much all passenger jets since the 50s and 60s have had yaw dampeners, for example.

asmithmd1 8y ago
True, but a yaw dampener is sort of like a steady cam, it isn't going to over-rule a pilot's rudder input. Put yourself in the seat of a pilot who has flown an electro-hydraulic 737 for years. Something "funny" seems to be going on with the trim, so you take control and the trim seems to be working perfectly while you manually toggle it, but then the MCAS kicks back in after 5 seconds and tries to push the nose down again. This kind of behavior is coming from a system Boeing did not tell the pilots about.
- zaroth 8y ago
  > This kind of behavior is coming from a system Boeing did not tell the pilots about. True for the first crash. However, no longer true by the time of the second crash.
  - pishpash 8y ago
    Still an unnecessary cognitive load.
  - myrandomcomment 8y ago
    I cannot agree more. After the 1st crash you would think every pilot would have become familiar with this system and how to override it. The stuff that has come out from the most recent crash shows that the pilot was read through manuals trying to understand what was happening. Given the most recent crash, why would he not think, hey lets disable this new system because my plane is acting in the exact same way. I am not saying that Boeing is not at fault for poor training or documentation but if I was flying the same plane as one that recently crashed I know I would have known everything I could about that crash before I lifted off in that same model.
    - faizmokhtar 8y ago
      Not likely. When the first crash happened Boeing try to shift the blame to Lion Air citing lack of maintenance and what not.
    - jiqiren 8y ago
      As many report have already mentioned: the MCAS is not in the manuals.
    - CaptainZapp 8y ago
      After the first crash Boeing should have pulled that plane out of service, period. It shouldn't be up to pilots to try to find workarounds for rotten engineering. The first crash can be chalked up to engineering errors, corner cutting and the desire not having to retrain and recertify pilots. The second crash is outright criminal by Boeing, for not immediately pulling that plane out of circulation after the Lion Air disaster. Regardless of the cost (which will be much, much more expensive after crash 2). Their cozy relationship with the FAA also didn't help and I hope the people responsible pay dearly for that. Throwing the pilots under the bus is how they tried to handle that PR desaster. Doesn't seem to work well, though.

ekianjo 8y ago

You can however disable the MCAS and it is apparently well documented in the pilot training material. When the trimming wheel acts strangely this is a sign that something may be going wrong and this is part of what pilots need to know when flying this aircraft. Now whether or not such information is widely known among all pilots is another matter altogether.

raverbashing 8y ago
MCAS wasn't, runway trim was, however, I don't believe the pilots would expect/recognize a runway trim failure on the occasions that MCAS would fail