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Rudder trim control on your aircraft?

Started by Hardy Heinlin, Fri, 1 Jun 2012 03:07

farrokh747

Some earlier discussions on the forum

http://aerowinx.com/board/index.php?topic=704.msg12027#msg12027

http://aerowinx.com/board/index.php?topic=738.msg7132#msg7132

QuoteQi169="PedStrg"; Mode=ECON; Min=0; Max=1;

1 = Tiller connected (pedal steering)

Ill try and make a video of the mechanism in action  ...   

cheers

fc

emerydc8

Just a follow-up on steering with the rudder trim. I tried this a few hours ago on the 767 and moving the rudder trim moves the rudder pedals, which move the nosewheel. But like I said earlier, there is such little nosewheel deflection possible with the rudders (7 degrees) that it is virtually impossible to steer it with the trim due to the lag time of the electric trim motor. By the time you have full rudder trim in and you start moving off the centerline, moving the trim to the other side is not enough to keep it from going off the taxiway.

As Peter confirmed above, pushing on the rudder pedals will move the tiller, but not very much.

emerydc8

Quote from: farrokh747 on Wed, 21 Mar 2018 02:55
QuoteAs far as I've learned it, on the 747 the rudder trim actuator is driven by a DC motor. The trim actuator varies the rudder's neutral angle; the rudder is at this neutral angle when the rudder hydraulics are relaxed or symmetric.

morning - i dont think the rudder trim actuator will 'hold' the rudder/s at a new neutral position if there is no hyd psi... as far as the rudder power control actuators are concerned, they cannot tell the diff between an input from the pedals or the trim actuator - all rudder inputs are summed up in the aft quadrant and  feel and centering unit, which passes it on to the actuators (via i guess the rudder ratio unit)  - of course, with any hyd psi present, i guess the rudder would be at the trimmed position..... 

However, since the trim actuator backdrives the pedals, they would now be stuck in the off center position without elec power

https://image.slidesharecdn.com/fc744flightcontrol-090325224309-phpapp02/95/fc744-flightcontrol-11-728.jpg?cb=1238021025

fc

I agree. I moved the rudder trim to full scale deflection with the hydraulic power off. It did move the rudder pedals to the new neutral position. I didn't check the position of the rudder but, like you mention, I doubt the actual rudder will move without hydraulic power.

Jon