Flap Position Sensor Installed (2/8/13)

3.0 Hours –

I finally received all the parts I needed to install the flap position sensor, so this became my main goal for the night.  The sensor is the Ray Allen POS-12.  It is just a box with a free-moving arm that can extend 1.2 inches.  The movement of the arm gets converted to a signal that is sent to the avionics.  My challenge is to link the sensor’s arm to the flaps in a way that full movement of the flaps is translated into 1.2 inches of travel on the sensor.

Not wanting to re-invent the wheel, I installed the sensor in a way that seems to be the most common among RV builders.  The sensor itself is attached to the forward side of the back rest brace.  The sensor is then connected to the flap weldment using a cushion clamp, some threaded rod and a couple of clevis ends.

First, I cut the threaded rod down to about 9 inches and then attached the clevis ends.  Both the rods and the clevis ends I used were 4-40, and purchased from a local hobby shop’s aviation section (RC plane parts).  One end attached directly to the sensor, and the other end was attached to the flap weldment using a bracket I made and a cushion clamp.  The cushion clamp was positioned on the flap weldment arm that goes to motor about 1/2 inch forward of where arm meets the main cross member of the weldment.  Once the clamp and sensor were attached to the weldment, I ran the flap motor until it was fully retracted.  I then manually retracted the sensors arm and positioned the sensor on the back rest brace.  With the position of the sensor set, I removed the back rest brace, drilled the sensor to the brace, and attached it with two #4 screws and stop nuts.

It still needs some finishing, but this is the backside of my bracket that will attach the position sensor’s pushrod to the flap weldment. This was a piece of angle, but one side was almost completely removed. Only enough is left to keep the bracket from rotating.

The front side of the bracket.

The complete flap position sensor setup. The clevis ends are RC parts from the local hobby shop, and they fit the sensor’s arm perfectly.

Once fully assembled, I ran the flap motor a couple of times to make sure the sensor could travel freely, and extend/retract fully.  The first run wouldn’t allow the sensor to fully extend, so I had to re-position the cushion clamp further aft and shorten the pushrod slightly.  After a little experimentation, I had everything dialed in.

In the flaps up position, the sensor’s arm is fully extended.

Flaps down, the sensor’s arm is retracted. The picture makes it look like the pushrod is right up against the flap motor, but it is really over an inch away.

Next, I started working on the F-782D angles.  These angles are used to provide additional support to the F-782A cover plates that cover up some of the fuel/vent lines in the cockpit.  The plans make the fabrication of these angles look more difficult than it actually was.  In the end, it didn’t take long to do all the trimming and drilling.

The F-782D brackets are fabricated from some .032″ x 3/4″ x 3/4″ angle. The plans make this part look more complicated than it is.

My F-782D angles after being trimmed and drilled for the holes that will attach the angles to the fuselage. The holes on the other side will get drilled in assembly with the F-782A cover plates.

In order to get an idea of the positioning of the angles, I temporarily installed the F-782A cover plates and marked where they butted up to the sides of the fuselage.  Drilling the angles is going to be a bit of a challenge since access is limited and there is no way to clamp the angles to the fuselage.  Instead, I’m going to try to use some double-sided tape to hold the angles in position while I start drilled.  However, I decided to let this wait until tomorrow.