Propeller Surging

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  • #84177

    I am trying to troubleshoot a problem that just started occurring on our late model 421C.

    During take-off I bring the power up to 25″ of MP before pushing the throttles up to take off power. Recently however the right hand RPM lags and then surges back and forth +/-100rpm.

    Once I reduce the power to 32.5″ MP and pull the props back to 1900 rpm the issue goes away and smooths out.

    Any ideas where to start looking. I thought it might be a sticky governor so I lubed it with Mouse Milk but it is still doing it.

    Thanks in advance for you help!

    #98612
    quote MHaakenson1:

    I am trying to troubleshoot a problem that just started occurring on our late model 421C.

    During take-off I bring the power up to 25″ of MP before pushing the throttles up to take off power. Recently however the right hand RPM lags and then surges back and forth +/-100rpm.

    Once I reduce the power to 32.5″ MP and pull the props back to 1900 rpm the issue goes away and smooths out.

    Any ideas where to start looking. I thought it might be a sticky governor so I lubed it with Mouse Milk but it is still doing it.

    Thanks in advance for you help!

    One thing to test is to check and see if it does it on a full power ground test. Do you have engine instruments? You could check and see if your EGT’s are changing with the prop rpm swings (which would point to some mixture issues)

    However, I strongly suspect that if it is still +/-100 rpm in flight it is the governor and it needs to be overhauled. There are a bunch of changes made to flyweights, etc over the years. I would be very relucant to fly it in this condition.

    I had sent my right engine governor to wings west governor exchange and they offered a good price. I recall it was ~ 900 for a basic overhaul, 1600 for exchange, and mine needed about 1300 of labor and parts because of the older style parts in it. Their number is (253) 848-3188. I bet they would offer some better tips and trouble shooting too if you gave them a call.

    The surging is probably not good at all for the counterweights in the crank.

    Eric

    #98614

    I started to get some surging on my left engine prop on my 310 with IO-470 engines. It stopped when I had the props overhauled. They believe it was caused by worn out parts in the prop hub. Springs I believe were the issue.

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