What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Flap position sensor error? (VPX)

S

samgaddis

Member
Hi all, on my 14 I'm having some issues with my flaps that I believe is due to a faulty position sensor. I didn't build the airplane so I've researched as much as I can and am about to take it to the mechanic, but he's no RV expert so I'm trying to get as educated as possible.

Here is a list of observations:
  1. The flap indicator in the G3X periodically doesn't correspond to reality. Ex. flaps are all the way up but the indicator shows half down. Then the next time I start the plane it might be showing correctly.
  2. When connected to the VPX unit (via computer using the VPX configurator software), the flap position number moves in unexpected ways. When I move the flaps down, it may initially show the position number going in the opposite direction. Then it'll jump roughly to where it's supposed to be. However the movement is somewhat erratic, unstable, and non-linear.
  3. Setting the correct endpoints is impossible because the resting position of UP or DOWN varies (position number when flaps full up or down can be different cycle to cycle).
Is an appropriate next step to just need to replace the position sensor? With this unit?

Thanks for your help.
 
samgaddis said:
Hi all, on my 14 I'm having some issues with my flaps that I believe is due to a faulty position sensor. I didn't build the airplane so I've researched as much as I can and am about to take it to the mechanic, but he's no RV expert so I'm trying to get as educated as possible.

Here is a list of observations:
  1. The flap indicator in the G3X periodically doesn't correspond to reality. Ex. flaps are all the way up but the indicator shows half down. Then the next time I start the plane it might be showing correctly.
  2. When connected to the VPX unit (via computer using the VPX configurator software), the flap position number moves in unexpected ways. When I move the flaps down, it may initially show the position number going in the opposite direction. Then it'll jump roughly to where it's supposed to be. However the movement is somewhat erratic, unstable, and non-linear.
  3. Setting the correct endpoints is impossible because the resting position of UP or DOWN varies (position number when flaps full up or down can be different cycle to cycle).
Is an appropriate next step to just need to replace the position sensor? With this unit?

Thanks for your help.
Click to expand...
First, this sounds like 'dirty' contacts (the same sort of thing that can sometimes happen to a volume control that is very 'scratchy' whenever you turn it.). Try spraying the sensing unit with contact cleaner (while moving it back and forth if possible). If you do replace it (I have exactly the same unit you have a link to), you may find a bit better performance if you position the sensor between the rotating shaft running left-right, and something fixed (with a hinge) to the airframe. Think about this, and position the Adel clamp on the rotating part so that you maximize the linear movement per angular degree of rotation, when going from full up to in-trail. because that's only 3 deg, that's the most stringent place you need accuracy.
 
You can test the sensor before replacing. The resistance between the orange and blue wire should be fixed at 5K ohms. The resistance between the orange/green and green/blue is variable and should range between 0-5K and 5-0K as the sensor moves through it's range of travel.
 
Last edited:
samgaddis said:
Hi all, on my 14 I'm having some issues with my flaps that I believe is due to a faulty position sensor. I didn't build the airplane so I've researched as much as I can and am about to take it to the mechanic, but he's no RV expert so I'm trying to get as educated as possible.

Here is a list of observations:
  1. The flap indicator in the G3X periodically doesn't correspond to reality. Ex. flaps are all the way up but the indicator shows half down. Then the next time I start the plane it might be showing correctly.
  2. When connected to the VPX unit (via computer using the VPX configurator software), the flap position number moves in unexpected ways. When I move the flaps down, it may initially show the position number going in the opposite direction. Then it'll jump roughly to where it's supposed to be. However the movement is somewhat erratic, unstable, and non-linear.
  3. Setting the correct endpoints is impossible because the resting position of UP or DOWN varies (position number when flaps full up or down can be different cycle to cycle).
Is an appropriate next step to just need to replace the position sensor? With this unit?

Thanks for your help.
Click to expand...
I had the same issue. Turns out the wiring diagram was incorrect. I had to swap around sensor wires until I got the correct action.
 
You must log in or register to reply here.
Back
Top