Saturday, October 27, 2012

X's and O's and OH-NO's!

Before starting on the lengthy acceptance tests, I thought I'd work on a couple of little things that turned up during the engine start. First was the situation of the right side cylinder heat temperature which was showing a big red X on top of the Dynon indication. Second was the lack of an O. The O in question is the red circle that is supposed to light up when the stall warning vane is lifted on the wing.

I started with the stall warning. I figured the little micro-switch inside the wing just needed adjusting, so I removed the little access panel, stuffed a little flashlight up in there to provide some light, retrieved my little side-ratchet screw driver, and loosened the two set screws. A little pressure on the switch and it swung into place. A test of the switch showed not only the red O on the Dynon but also sent a loud warning horn into the headsets. Problem solved, I replaced the panel and went to look at the CHT wire.

Now where did that flashlight get to? I just had it, right there in the....

I glanced over at the stall vane and could see the bright illumination coming from inside the wing.

Rats. Now the access panel would have to come off again so I could extract the flashlight.

I didn't get much done on the CHT problem other than verifying that the problem is with the wire. I'll have to remove the avionics bay cover (a royal pain) and dig around in the wires looking for the problem. For now I will live with the X problem, but it will have to be fixed before the airworthiness inspection.

Before removing the cover, I thought I'd so something else that I would have to do with the cover on. I need to check the engine RPM when running at WOT (wide open throttle).  I pulled the plane out to the taxiway, out some chocks about eight inches in front of the wheels (figuring that I might as well test the brakes too), and started her up. As I was waiting for the oil temp to get high enough to throttle up, I thought I saw wisps of white/gray smoke out the right side of the canopy. Wondering what that could be, I glanced at the Dynon only to see the oil pressure starting to fluctuate. That didn't seem right so I started the shut-down process. Just before killing the engine, the dulcet tones of the HDC (Hot Dynon Chick) pointed out that my oil pressure was getting low, and had in fact just dipped down into the yellow. I've heard about people struggling with wiring/sensor issues that cause strange behavior in the oil and fuel pressure, so I sighed with disgust, wondering how long it would take to track down this problem.

As it turns out, not long at all!


Oil was gushing out of the #3 valve cover!  Odd, that, or so I thought until I touched the single allen-head bolt that holds it on. Hmmm. So I checked #1: also loose. And it is at that very instant I remembered the patriarch of The Jackson Two telling me to make sure I check the torque on those bolts before running the engine again. Which.... I had failed to do.

It looks like I lost about a quart of oil and the engine never ran anywhere near dry, but it was a close call nonetheless. My new rule is now nothing gets screwed or bolted onto the airplane at anything other than final torque. It's too easy to miss something important otherwise.

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