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ACRO E-mail Archive Thread: [Acro] rpm surge on IO-360?

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ACRO E-mail Archive Thread: [Acro] rpm surge on IO-360?


Thread: [Acro] rpm surge on IO-360?

Message: [Acro] rpm surge on IO-360?

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From: Jamie Monberg <jmonberg at>

Date: Mon, 12 Aug 2002 06:49:35 UTC


  I've got a persistent problem with engine surging on my Eagle2 (AEIO-360-A1D
w/hartzell constant speed)

The problem manifests itself almost immediately after I reduce power from
takeoff. The rpm will surge +-100rpm with a period of maybe 2 seconds from
low to high. The surge will reduce in amplitude over the next 4-5 cycles and
then settle down to a consistent rpm. After a few minutes the "wobble" will
re-appear. I notice slight oil pressure fluctuation during (not preceding)
the surging behavior that is consistent with what might happen were one to
quickly change the pitch of the prop. Engine temp does not seem to be a
factor. The problem seems worse when the crankcase is filled closer to eight
quarts than when it is filled closer to 6 quarts. The problem also seems to
be slightly less extreme when I increase the pitch of the prop for a really
low cruise setting (i.e. 20 square)
Oil consumption has not changed -- there is about 630 hrs on the engine and

My mechanic seems a little mystified and recommends a governor and prop
rebuild. Just in the spirit of better understanding the problem I thought I
would put this to the list. For all I know it is entirely typical for what
happens when a governor starts going south.

Thanks in advance for any help!



© Dr. Günther Eichhorn
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