Alternator coupling failed at 400 hours and I found it during a routine inspection

Laura Knight · 2026-10-02T07:45:05.296516+00:00

So this happened on a King Air 200 that came in for a 200 hour inspection at our shop in Wichita. I was doing the routine checks on the left engine and noticed some fine metallic dust near the alternator drive. Pulled the coupling off and sure enough, the splines were almost gone, maybe 30 percent left. This thing had just under 400 hours on it, way under the usual replacement window. I showed the lead and he said he had seen it once before on a plane that had a rough engine mount issue causing extra vibration. We checked the mounts and found one that was sagging bad. So the vibration was eating the coupling. Replaced the coupling and all four mounts, ran it up, smooth as glass. Has anyone else seen a coupling go that early because of something else going bad?

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Alternator coupling failed at 400 hours and I found it during a routine inspection | Aircraft Mechanics - Librear