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Date:  6-6-2015
Number of Hours:  0.00
Manual Reference:  
Brief Description:  Flywheel Cap Screw Failure (1 of 2)

I have 80 hours on my AeroVee, which first flew last June. I generally cruise with the secondary ignition turned off (take-off and land with it on). I get more charge to the battery that way. The plane was flying great on the primary alone, or the primary and secondary, with no hiccups and no anomalies. But on a go-around on my last flight the tachometer went haywire, bouncing between 2,000 RPM and 6,000+ RPM. The engine was running normally, so I just flew it like I normally do and landed uneventfully. I figured it was a loose wire.

When I landed I opened the cowl to have a look. The fuse between the alternator and the voltage regulator (30 amp) was blown, so I replaced it, but this obviously meant there was a problem with the alternator/ignition. When I turned the prop by hand I heard a lot of grinding. Not good! But I noticed the grinding was coming from the rear of the engine and not inside the case. I then noticed the trigger cap was not turning on center, and one side of it was pretty well scored. A little more looking around and I saw that one of the triggers had it's plastic casing worn away by the off center trigger cap. I took off the stator assembly and there was what looked like a pile of sand inside. I also found a sheared off cap screw head, and a lot of abrasion and heat damage inside.

So I got the plane in a hangar and proceeded to remove the engine. There is no other way to investigate or fix all this.

In a nutshell, everything attached to the crank hub at the rear of the engine (it's part of the whole flywheel assembly) was loose. Very, very loose. As in screws were backed out or so loose I could turn them with my finger. That allowed everything attached to the crank hub to wobble, and become loose themselves. Everything was wobbling so badly that there was a tremendous amount of friction between all those parts, generating a lot of heat and a lot of rubbing. So much heat and rubbing that some of the aluminum parts look like they became molten on the edges and flung off, which scored ot
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New rear oil seal

New rear oil seal

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Cap screws installed with Loctite & Loctite primer

Cap screws installed with Loctite & Loctite primer

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New cap screws on the trigger shaft, being installed.

New cap screws on the trigger shaft, being installed.

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