Many factors will cause a low or high oil pressure indication on TFE731 engines. One of the more common causes is a faulty Breather Pressurizing Valve (BPV). The following are two scenarios that will lead you to this conclusion.
Oil Pressure Rises During Descent
If the crew reports normal oil pressure at altitude but the pressure rises as the aircraft descends, the most probable cause is the BPV is stuck open. At sea level, the valve should be open at least .07 in. A defective bellows will cause the valve to be closed on the ground. With a strong light, visually check the BPV. If it is closed, replace the BPV.
Oil Pressure Drops During Climb
Oil pressure that is normal below 27,000 ft. but drops as the aircraft climbs higher is another indication the BPV is not closing. Remove the BPV and push on the bellows. They should not move. If you are able to move them, replace the BPV. If the bellows feels normal, swap with the opposite engine. If the squawk is still present, contact your TFE731 Service Center.
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