Intermittent Flaps Problem SOLVED

[PandaCub]

Flap deployment on my RV-14A (w/ G3X) is pretty straightforward: one switch click per preset position (10º-20º-32º), continuous up/down when the switch is held, and full up/down if the switch is clicked 3 times.

Recently, flap actuation started to exhibit random position issues, i.e. sometimes not retracting/extending unless clicked multiple times. I suspected everything from a dirty switch to a bad motor to a maverick position sensor. My local A&P and I jumped into the problem and he noticed that the RAC position sensor resistance (a basic rheostat) was jumping around kind of like a bad potentiometer on an old stereo dial.

We replaced the sensor, recalibrated the G3X flap parameters using a digital protractor, and now everything is back to normal. Moral of the story? It seems the position sensor rheostat does have a working life - about 500 hours in my case - but it is just an $80 part which seems relatively cheap on the TACOF scale (Typical Aircraft Cost of Fix).

Blue skies!

 

[rv8ch]

It would be interesting to open up the failing part to see what's up. I suspect some moisture got in there, but just a guess. These are very simple devices.

 

[Dugaru]

Flap deployment on my RV-14A (w/ G3X) is pretty straightforward: one switch click per preset position (10º-20º-32º), continuous up/down when the switch is held, and full up/down if the switch is clicked 3 times.

Recently, flap actuation started to exhibit random position issues, i.e. sometimes not retracting/extending unless clicked multiple times. I suspected everything from a dirty switch to a bad motor to a maverick position sensor. My local A&P and I jumped into the problem and he noticed that the RAC position sensor resistance (a basic rheostat) was jumping around kind of like a bad potentiometer on an old stereo dial.

We replaced the sensor, recalibrated the G3X flap parameters using a digital protractor, and now everything is back to normal. Moral of the story? It seems the position sensor rheostat does have a working life - about 500 hours in my case - but it is just an $80 part which seems relatively cheap on the TACOF scale (Typical Aircraft Cost of Fix).

Blue skies!

View attachment 84891

I mean, it has “POS” right in the name. But I kid. Nothing against Ray Allen based on my experience at least.

 

[Radioflyer]

If you had flipped open the rear panel of the POS12 sensor, you would have noticed a very standard, 5K Ohm, linear potentiometer, that is pressed-fitted in place. It is available, from Digikey for $1.67 plus $5 for shipping.

 

[CF86301]

It seems the position sensor rheostat does have a working life - about 500 hours in my case - but it is just an $80 part which seems relatively cheap on the TACOF scale (Typical Aircraft Cost of Fix).

View attachment 84891

Kind of makes you think a little harder about the tradeoffs of installing this system (with an $80 part) vs. a flap motor with a built-in potential POS. Which I've done.

 

[georgemohr]

Kind of makes you think a little harder about the tradeoffs of installing this system (with an $80 part) vs. a flap motor with a built-in potential POS. Which I've done.

Lets hope the integrated unit is well constructed.

 

[Walt]

This is why I'm still a fan of looking out the window to determine flap position instead of 'fancy gadgets' that have little value.
If it's not there it can't fail (KISS).

 

[JonJay]

99% of the time you need two flap settings on an RV: Up and Down.
You can add in 1/2 if you want to get fancy……

 

[Walt]

99% of the time you need two flap settings on an RV: Up and Down.
You can add in 1/2 if you want to get fancy……

Full flaps with a 3-blade prop at idle, the decent angle is surprisingly steep on my 7, it will get your attention!
I generally use 20-30 myself with power at idle (always practicing for that engine out scenario).

 

[BobTurner]

I’ve been pleasantly surprised by how often problems like this (potentiometers, connectors, rack pins) can be fixed with a squirt of contact cleaner plus exercising the pot or connector. My gut feeling is that this is a temporary fix but in practice it often seems to work for a long time.

 

[BobTurner]

This is why I'm still a fan of looking out the window to determine flap position instead of 'fancy gadgets' that have little value.
If it's not there it can't fail (KISS).

Ever try to determine if the flaps in a -10 or -14 were full up, or in trail, just by looking - in the dark?