3 ms·

For reference, here is the runaway stabilizer memory item (the "checklist") for 737: 1. Control column ............................. Hold firmly 2. Autopilot

by twtw 8y ago

For reference, here is the runaway stabilizer memory item (the "checklist") for 737: 1. Control column ............................. Hold firmly 2. Autopilot (if engaged) ..................... Disengage 3. IF the runaway stops: ------------------------ [done] 4. IF the runaway continues: STAB TRIM CUTOUT switches (both) ...... CUTOUT IF the runaway continues: Stabilizer trim wheel ............ Grasp and hold EDIT: It's #4 that's of interest here. People saying that the interface changed are saying that it's fine if pilots stop after #1, even when dealing with runaway stabilizer for 12 minutes.

Someone1234 8y ago
Accurate but irrelevant. This assumes the pilots knew they were dealing with a runaway stabilizer, and considering M.C.A.S. wasn't behaving similar to their previous training/experience/simulations with Runaway Stabilizers, it isn't clear they'd know they should follow this checklist. Now had they been actually trained on M.C.A.S. inc. faults, they may have known to do exactly this and we wouldn't even be discussing it. This has been discussed in great detail on other flight forums.
- twtw 8y ago
  It's not really possible to not know that you are dealing with a runaway stabilizer. MCAS (and every other automatic system to adjust trim) causes large physical wheels at the side of the pilot's knee to spin.
  - sokoloff 8y ago
    And these large wheels have small bell/clackers on them so you get a distinctly audible signal in addition to the large black wheels with white stripes on them.
    - sokoloff 8y ago
      Here's a video of the wheels in motion: https://vimeo.com/34501723 https://vimeo.com/34501723 Disregard the text on the video description as it's blatantly wrong (describing that the trim tabs still move without the wheels moving; wrong on two accounts: the trim doesn't move without the wheels moving and the 737 uses a jackscrew for horizontal stabilizer trim rather than trim tabs [which is why the pilot can't simply override the aerodynamic force as they could with a trim tab]) Jackscrew operation: https://www.youtube.com/watch?v=rxPa9A-k2xY https://www.youtube.com/watch?v=rxPa9A-k2xY The 7-3 has balance tabs to make the control forces lighter in the event of a hydraulics failure, but these are not trim tabs in any sense of the word.
rocqua 8y ago
As I read the article, it seemed like before, step 1 would suffice before. If this is not the case with MCAS, it could at the very least throw the pilot's diagnostics. "Is it runaway stabilizers? Well, no response from holding the control column firmly so I guess not. Lets check other things". Sure, the correct response is to follow the checklist, but should we really rely on pilots always knowing the correct response? Especially when that goes against their previous experience? Not that I am defending these pilots not knowing the checklists, instead I am arguing we should take into account learning from experience rather than theory.

by twtw 8y ago

Someone1234 8y ago

Accurate but irrelevant. This assumes the pilots knew they were dealing with a runaway stabilizer, and considering M.C.A.S. wasn't behaving similar to their previous training/experience/simulations with Runaway Stabilizers, it isn't clear they'd know they should follow this checklist. Now had they been actually trained on M.C.A.S. inc. faults, they may have known to do exactly this and we wouldn't even be discussing it. This has been discussed in great detail on other flight forums.

twtw 8y ago
It's not really possible to not know that you are dealing with a runaway stabilizer. MCAS (and every other automatic system to adjust trim) causes large physical wheels at the side of the pilot's knee to spin.
- sokoloff 8y ago
  And these large wheels have small bell/clackers on them so you get a distinctly audible signal in addition to the large black wheels with white stripes on them.
  - sokoloff 8y ago
    Here's a video of the wheels in motion: https://vimeo.com/34501723 https://vimeo.com/34501723 Disregard the text on the video description as it's blatantly wrong (describing that the trim tabs still move without the wheels moving; wrong on two accounts: the trim doesn't move without the wheels moving and the 737 uses a jackscrew for horizontal stabilizer trim rather than trim tabs [which is why the pilot can't simply override the aerodynamic force as they could with a trim tab]) Jackscrew operation: https://www.youtube.com/watch?v=rxPa9A-k2xY https://www.youtube.com/watch?v=rxPa9A-k2xY The 7-3 has balance tabs to make the control forces lighter in the event of a hydraulics failure, but these are not trim tabs in any sense of the word.

rocqua 8y ago

As I read the article, it seemed like before, step 1 would suffice before. If this is not the case with MCAS, it could at the very least throw the pilot's diagnostics. "Is it runaway stabilizers? Well, no response from holding the control column firmly so I guess not. Lets check other things". Sure, the correct response is to follow the checklist, but should we really rely on pilots always knowing the correct response? Especially when that goes against their previous experience? Not that I am defending these pilots not knowing the checklists, instead I am arguing we should take into account learning from experience rather than theory.