control rod scrapes the fuel pump

[GatorsR1]

I assume a rod end could be adjusted (outward) if a push/pull rod is too short?
The right side push/pull rod "kisses" the top of fuel pump on my 12 (flaps up, full deflection).
I notice it during preflight (with pump running) the pump sound changes when the rod touches it at full flap deflection.

[Tacco]

Originally Posted by rvbuilder2002

This is usually caused by the flapperon push/pull tubes being not quite the proper length when the flapperon torque tubes were originally drilled (if they are just a bit short the horns on the torque tubes will be angled fwd a bit too much which will cause contact when it pivots fully fwd.

Scott, I believe you are partly correct. It has to do with pushrod length but not torque tube drilling. The drilling process only determines the position of control surface (although they may not measure to the dimensions in the PAP). Contact with the fuel pump is caused by the either flaperon pushrod being too short or the the flap handle to mixer bellcrank being too long. Or both. Ask me how I know.

[amekler]

my right Flaperon tube only hits with no flap setting
Alan

[DaleB]

Originally Posted by amekler

my right Flaperon tube only hits with no flap setting
Alan

That’s how mine was. I think I figured out the mistake the builder made, but it’s been a while and I don’t remember exactly what it was. Either the flap handle was in the wrong position, or the AN3 bolt used to hold everything in one place was in the wrong location. Anyway, the only fix in our case was to replace the right side flaperon torque tube. Don’t have the part number handy, I’m away from home. Everything worked, but the right side pushrod would bump the corner of the fuel pump with full right stick and no flaps. You could only feel it on the ground, and it was just barely noticeable. With flaps it didn’t happen at all.

[piperpilot]

This is a great thread, and as I`m getting ready for final inspection, it had me wondering about clearances on my controls. I also found the sound of the rudder cables to be a bit concerning so I was thinking mine could have been accidently crossed or rubbing somewhere (they turned out to be fine, just the sound of the cable on the plastic bushings in the rear bulkhead).

So with this in mind I purchased a borescope on Amazon for $35 CAN (that's like $2 for you US guys ). For a unit this cheap I cannot believe how clear and valuable of a tool it is. Its got a very small head (maybe 3/8") and about 10 ft long. I was able to "chase" all my control cables and and control rods and watch them move back and forth while my son operated the flap handle and control stick. I see my flaperon tube clears the fuel pump by about 1/4" max.

I think every RV12 owner should have one.

You can search Amazon US for;

"Waterproof Flexible Wireless Endoscope WiFi Borescope Inspection Camera 2.0 Megapixels for Android and iOS Smartphone, iPhone, Samsung, iPad"

[rvbuilder2002]

Originally Posted by Tacco

Scott, I believe you are partly correct. It has to do with pushrod length but not torque tube drilling. The drilling process only determines the position of control surface (although they may not measure to the dimensions in the PAP). Contact with the fuel pump is caused by the either flaperon pushrod being too short or the the flap handle to mixer bellcrank being too long. Or both. Ask me how I know.

Same thing I was saying; with my mention of "drilling" being that you can't just lengthen the push/pull rods to correct it. You would have to at the same time, do the rigging process and drill new outer torque tubes to have the system configured correctly.

Said in a different way, the problem is caused by the flaperon torque tube arms not being in the proper position when the torque tubes were drilled (which locks in the relative positions of the entire system).

[Tacco]

Got it. Agree. My concern was that people would re-drill the torque tubes thinking that was the root cause of the issue. What they really need to do is to make absolutely certain of the length of the pushrods...then re-drill the t-tubes because if drilled when the pushrods were the wrong length, they’ll need to be re-drilled to achieve the correct flaperon position.

[amekler]

so today I measured the flap control rod I got 11 7/8. The specs say 11 25/32
both flaperon control rods were 38 7/8 the specs say 38 3/4
these measurements were in the plane with a tape measure so I'm sure they could be slightly off
Should I remove the rods and remeasure?
Is this slight difference enough to cause the lack of clearance of the right flaperon control rod?
Alan

[rvbuilder2002]

Originally Posted by amekler

so today I measured the flap control rod I got 11 7/8. The specs say 11 25/32
both flaperon control rods were 38 7/8 the specs say 38 3/4
these measurements were in the plane with a tape measure so I'm sure they could be slightly off
Should I remove the rods and remeasure?
Is this slight difference enough to cause the lack of clearance of the right flaperon control rod?
Alan

If the issue was caused by a dimensional issue with the push/pull rods it would be because they were slightly too short.
If your measurements are correct, it would mean yours are slightly too long.
If that is the case, then they shouldn't be able to contact the fuel pump unless the flap handle wasn't in the fully retracted position when the torque tubes were drilled.

[amekler]

I remember the flaps were fully retracted when drilling the torque tubes
my plane is to remove the control rods and remeasure
Alan