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I recently had the opportunity to try a 737 simulator and one thing that struck me was the placement of the trim wheels. They are located dangerously close to the seats and, man, do they spin fast. I can only imagine the pain if you accidentally leave the manual trimming handle retracted or if you get some hair stuck in there.

Why are they placed this way? I would assume that a less prominent placement would still allow easy access for manual trimming.

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  • $\begingroup$ Here is a video I found. $\endgroup$ – Daniel R Nov 3 '15 at 18:33
  • $\begingroup$ To remind pilots to follow their checklists and stow the trim handle when not using it? $\endgroup$ – voretaq7 Nov 3 '15 at 18:59
  • $\begingroup$ Here's another view of the trim wheels in action so you can see where the pilot's leg is in relation to the wheel. (Hair shouldn't be an issue, and it's safe with the handle stowed, but it can catch you in the knee if someone uses the electric trim with the handle extended.) $\endgroup$ – voretaq7 Nov 3 '15 at 19:03
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    $\begingroup$ Instructional video, but not for a NG, showing the full chain from the trim wheel to the horizontal plan. $\endgroup$ – mins Nov 3 '15 at 19:09
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My guess is that the manual trim wheel handle (when not motor driven) to adjust it manually needs to be:

  • easily accessible from the seat.
  • generate a sufficient amount of torque by moment arm.

Which leaves this as one of the few spots where it could be conveniently placed. You can find the same thing in older aircraft cockpits including the L1011, B727 and B747-100/200. The 737 design remains very unchanged from when it first flew.

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    $\begingroup$ It is a good position in terms of motion efficiency: On the pedestal next to throttle/slats/flaps (all things which would require you to re-trim, and if the electric trim fails you're doing it with the wheel, so your hand is right there). The location (and noise the trim wheel makes) also provide audio and visual cues to the crew that the trim is running. $\endgroup$ – voretaq7 Nov 3 '15 at 19:06
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    $\begingroup$ The noise is also perfect for waking up sleeping jumpseaters to let them know you are starting descent :) $\endgroup$ – TomMcW Nov 4 '15 at 3:26

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