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6 Answers

Constant Speed Prop.

Asked by: 2856 views Aircraft Systems, General Aviation

During the prop. cycle governor check that occurs during the "run up" should show a decrease in RPM, decrease in oil pressure, increase in manifold pressure.

My question: What is considered acceptable:  normal oil pressure decrease? Normal RPM decrease? Normal manifold pressure increase?

I cannot find the parameters (limits) in the Piper Arrow information manual.


Thank you for the feedback.



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6 Answers

  1. Lucas on Nov 14, 2013

    There are no acceptable parameters because it all depends on how far back you pull the prop lever. Pull it a little and the change is small, pull it far back and the change is considerably larger. If you are flying a multi, pulling the lever completely back would result in a manifold pressure equal to outside pressure a zero rpm reading and oil pressure reading as the prop would feather and the engine shut down.

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  2. Brian on Nov 14, 2013

    What Lucas said. I only add that some aircraft will list a limitation on how far to pull the props back during this test. You will find this in the POH in section 4 where they mention the run up checks.

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  3. Dan Chitty on Nov 14, 2013

    Thank you Brian and Lucas for the feedback.

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  4. Kris Kortokrax on Nov 17, 2013

    Check the POH for your airplane. Read the amplified procedures. Many times you will see a statement to not allow an RPM drop of more than 500 for the Arrow.

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  5. Mark Kolber on Nov 17, 2013

    It’s important to keep in mind that the goal is simply to make sure the system is working. The three standard checks confirm that, so anything more than the time it takes to do that is unnecessary and could conceivably cause more hard than good; hence the limitations that sometimes appear in the POH, as Chris mentioned. So, for example, when doing the MP part of the test, watch the MP as you pull back the prop, as soon as you can detect a MP rise that part of the check is over and the prop should go back to full forward. And if you don’t get the rise almost immediately, in indicates you may have a problem that needs to be examined further.

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  6. Dan Chitty on Nov 18, 2013

    Thank you Mark and Kris for the additional feedback.

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