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NA Aztec engine with hunting RPMs.

Sep 24, 2020
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Wondering if anyone has seen this before or has any ideas regarding cause / cure.

During flight the LH engine is intermittently experiencing a +/- 100rpm oscillation, pilot can feel & hear the variation, MP also moves in conjunction with the rpm, we have Horizon digital tachs in the aircraft so it's not an indication of a sticking tach cable. This can occur at different phases of flight and power settings, I haven't observed it while running on the ground. In flight magneto check while the hunting was occurring had no effect.

So far I've replaced the governor, propeller & fuel servo with no change.



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