Originally Posted by
Fly Aiprt
I wouldn't be surprised if Boeing had failed to actually measure those torques in flight.
The torque must have been measured (or calculated) when the original trim wheel gearing was designed. I assume that when the wheel diameter was reduced they left the rest of the system unaltered, hence the retractable handle to increase leverage.
Whether they calculated the torque required at maximum stabiliser deflection at Vne I don’t know, but what Boeing may not have done is looked at time taken as well as force required. When you are very fast and very low, how fast you can manually re trim is as important as how much force is needed which is why relieving that force by a gearing solution is not a complete solution.
Halve the force required through gearing and you double the time required to move the stabiliser through a set amount. That is why if the force needed is deemed unacceptable, then an electric servo is the only real solution.