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b777-400 on take off and landing had a normal oil pressure. but in cruising the oil pressure drop below normal. how could this happen?

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1 Answers

  1. Chris Polek on May 30, 2014

    I am not all too familiar with a B777-400 engine. But I have a lot of PT6A experience and what initially comes to mind is temperature. On takeoff the engine has not had too much time to heat up. There would be something to help regulate the temperature of the oil. At a higher power setting there could be something stuck that fixes itself at the lower power settings of landing.

    It would be interesting to see what the oil temperature is doing when the pressure changes. If the temp is going up with pressure drop and temp is going down with pressure increase you have a oil temp problem (something in the oil cooler system). If the Temp does not change with Pressure then you could also have an indication problem at the higher airspeeds of cruise flight moving a wire harness at the pressure sending unit. and the slower speeds of takeoff and landing you don’t have as much airflow in the engine cowling causing the movement of the wires.

    In my experience troubleshooting engine issues one thing rings true. If you have one parameter moving it’s 90% of the time indication issue nothing wrong with the engine. If you have two or more parameters (i.e. oil pressure and oil temperature) moving you have engine issues.

    Hope this helps.

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