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[June 3, 2017]


My mind has been completely occupied with where the missing end of the cotter pin was. How long ago did it fall off? I have about 450 hours on my airplane, and shame on me, I have never pulled the EMAG to inspect it. That cotter pin could of been banging around in my engine for almost it's entire life. What damage could it of done? Did it get ground up in the accessory case gears? Ugh, I was sick to my stomach just thinking about all of the possibilities.

I also thought of how this was also a blessing in disguise. The other half of the cotter pin certainly would of eventually fallen off - it was very loosely still attached. The castellated nut was also a little loose on the EMAG shaft. What if that nut fell off and the gear came off? Wow, that would certainly be a catastrophic failure of the engine.

I used my borescope to try to find the other half of the cotter pin in all of the locations I could get access to. Accessory Case, Oil Drail Plug, oil screen. A lot of debris initially looked suspicious, but nothing conclusive. The good news with this inspection is the accessory case gears I could see through the mag hole all seemed to be in good shape. No deformations or abnormal wear marks.

So the only thing left to do is drop the sump. This is no simple feat. Off came the exhaust, intage tube, fuel injection servo, etc.. Finally we dropped the sump and I expected a shiny cotter pin to be staring me in the face. Nope. Shit. I used a magnet and tried to find it in the sludge at the bottom of the sump. Nothing. Crap...where could it be???


I looked up at the underside of the engine and sent the borescope up the accessory case gears looking to see if the missing piece of cotter pin was on one of the shelves on the sides of the accessory case. Nope. Nothing. However, on the plus side, the gears all looked to be in good shape.


I was a little frustrated and decided to leave the hangar. When I got home I reviewed pictures of my previous oil screen findings. Could this piece of metal be the cotter pin? Ugh, looks like it was ground up in the accessory case.


Moving on to something less depressing, I wanted to make sure the black dust I found on the inside of my cowling was coming out of my alternator. Well it only took a few spins over a white towel (dont judge the floral design...hand-me-down from the grandparents!) for a bunch of black chunks to fall out. Glad I found the root cause of that.

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Last Modified: September 4, 2017