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4 Answers

Low oil pressure

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Aircraft Systems

Oil pressure at startup, runup, climb, and cruise was in the green range.  After flying for about 20 minutes, tried some power reductions to descend.  Oil pressures dropped below green once below 1800 rpm and were nearly at the redline when at 1000 rpm.  Oil temperatures had increased as the oil warmed up throughout the flight but remained steady during the pressure drops at the lower rpms.  Increasing power above 1800 rpm brings oil pressure back in green arc.  Mechanic says the oil pressure relief valve needs to be adjusted. What are your opinions on whether the aircraft is safe to fly and whether it show be flown before this adjustment is properly made?

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4 Answers

  1. Steve Butler on Jul 19, 2013

    One of the items required for day VFR flight is an operable oil pressure gauge. It would appear that either the gauge is inoperative or it is giving accurate readings and the engine is not getting proper lubrication under some circumstances. While I might not be too concerned about flying it across town to reposition it for repair, I think it is time to ground it.

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  2. Hans Mathews on Jul 20, 2013

    I agree with Steve, I would ground the plane until I had this resolved. This could be especially bad if your craft has a CS prop. Loose the oil and you loose prop control. Single engine will fail to low pitch, but a twin could fail feathered, so this is an important item, more so than just bearing lube.

    As to the mechanics speculation, it seems plausible. Relief valves don’t usually “un adjust” themselves, but they do get bits of debris that keep them from reacting and sealing properly.

    You didn’t say where your flying, but I would also consider if your oil is correct for your environment, there are usually choices based on local ambients in the POH. If you have a thin oil meant for a cool climate and are running around down here in the south you could have the symptoms you are reporting.


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  3. Mr NineThreeKilo on Jul 21, 2013

    CHT temp?

    We have a similar issue on a IO550, on a good pitch down she will ready 0 oil pressure, good oil temp and CHTs, its a CS prop and the prop wont wonder (lack of oil pressure will cause a CS prop to increase in RPM on a single engine), so we know its the sender, gauge or something.

    How much oil did you have in the plane pre and post flight

    In our case the plane was fine

    You REALLY want to get to the bottom if this issue (or perhaps non-issue) before you fly much more, if you really do have a oil pressure issue, no oil pressure = no engine in rather short order

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  4. Jh on Oct 05, 2013

    Excessive oil pressure may indicate a blocked filter, blocked oil gallery or the wrong grade of oil. Low oil pressure indicates worn bearings on the crank shaft or a broken oil pump.

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