Cabin heater control flap breaks

[Eric Greenwell]

While I was cleaning the some oil leak residue off the lower part of the engine installation, I noticed the cabin heater control flap just lying there, unhinged at this end (right side on the plane). I think this explains the erratic cabin heat control I've had this year.



The hinge rod was still partially in the flap, but it looked like this:



The right end is nearly severed by wear from the engine vibration on the rod against the sharp edges of the hole in thin (0.040" I estimate) stainless "heat box". The right end is flattened to keep it in place. The left end, which I assume also had a flattened end or other means of keeping it in place, has been completely severed, allowing the rod to work it's way out of the hole (note, right and left here refer to the picture; on the engine, the flattened end was on the left).

I repaired it by getting some stainless hinge rod of nearly the same size (0.088" vs 0.095" OEM), bending 1/4" of one end at 90 deg to retain it. The other end is retained by a small collar with a setscrew. On the advice of a mechanic at the field, both ends were smeared with RTV to prevent vibration from causing problems again.

During the next flight, I noticed the heat control worked well, like it used to.

Eric