Elevator Trim Indicator

[rfazio1951]

I helped my friend set up his HDX and we got the trim motors tied to the autopilot button control, with sensors tied to the EMS. Everything works right according to me, but he thinks the elevator trim indicator is the wrong way. So the motor and trim move correctly bit the indication on the screen is what he thinks is wrong. When the plane is trimmed down the screen indicator goes below the center line. When the plane is trimmed up the indicator goes above the center line. I think it's right, but the question, can I switch that? It's doesn't look like I can from what I see, If I switch it, the autopilot will move the controls the wrong way.

 

[jdubner]

Richard, FWIW I'm with you -- trim up and the indicator moves upward. But if your friend wants the opposite, I don't see any reason why he can't simply reverse the trim position potentiometer's +5V and ground wires (WHT-ORG and WHT-BLU in the case of my Ray Allen trim servo). That will have no effect on the operation of the trim motor, only the indicator.

Doing so will necessitate another trim indicator calibration to get the proper indication for takeoff trim.

--
Joe

 

[RVDan]

Assuming that you are using the RAC trim servos, the position is measured from the center arm of a potentiometer, and has nothing to do with the motor input. The voltage across the arm when referenced to power or ground is the signal for trim position. If you have the reference backwards, the trim indicator will read backwards.

 

[rfazio1951]

Thanks guys, we will give it a try.