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Strange black powder

During preflight today I noticed a strange black powder on the inside top of the copilot side engine cover. This powder is heavier on the pilot side of the battery box and tubing below. Anyone know what this is? My wild guess is that it's graphite powder possibly being sprayed out of an alternator? Haven't seen it before and have requested my mechanic take a look. But curious what thoughts are here. Thanks!

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Model: Bonanza G36
Aircraft Serial Number: E3797
Posted 11/30/2023 - 3 months ago
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Air conditioning belt residue would be my guess. If the belt is below specified tension, it can slip at cycle start and create the black bits.

Mike
ABS Technical Advisor

Posted 11/30/2023 - 3 months ago
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And when the belt fails, the mess will be unbelievable. Time to check/replace that belt and properly tighten. I've begun to replace the belt each annual no matter how good it appears. YMMV

Posted 11/30/2023 - 3 months ago
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All, the belt was just a bit loose. Tightening fixed the problem. Thank you!

Posted 12/8/2023 - 2 months ago
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Strange black powder