Low oil pressure, or instrument failure? Help needed.
Posted: Mon Jul 06, 2020 8:32 am
2002 MXT-7 180-A, 1,200 hours.
Headed out for an aerial recon of Mt. St. Helens with the girlfriend to show her the north side of the mountain from the air. We climbed it two weeks ago and thought she'd love the perspective.
Did normal preflight. 6.5 quarts of oil; just where it should be.
I monitor the engine instruments obsessively, and it turns out Saturday that was a good idea.
Half way there, 35 minutes into the flight at 8,000'...
The oil pressure usually stays 3/4 of the way to the top of the green. Next scan I look to see its just barely in the green, the left side of the needle touching the yellow. It's never been there while running before. The needle occasionally jumps into the green, but spends most of its time borderline yellow.
I reduce power and head for home, cognizant of airports and places to land along the way. The engine continues to run perfectly well and the oil temp is exactly where it should be. I have two oil temp gauges. The OEM one and also a probe for the JPI engine monitor. They agree, all is well. All 4 CHT's are normal.
We land uneventfully back home at RLD. No oil on the engine and no oil on the belly. The correct amount is on the dipstick.
I think this is a faulty sending unit or instrument. I don't picture it being the engine but the plane is grounded. I gave the keys to my AI and he is backed up may be some time before he gets to it. What do you all think is going on?
FWIW the annual was completed 10 hours ago. My lowest compression was 78, the filter looked fine and there were no (known) squalks.
Thanks in advance,
Bill
Headed out for an aerial recon of Mt. St. Helens with the girlfriend to show her the north side of the mountain from the air. We climbed it two weeks ago and thought she'd love the perspective.
Did normal preflight. 6.5 quarts of oil; just where it should be.
I monitor the engine instruments obsessively, and it turns out Saturday that was a good idea.
Half way there, 35 minutes into the flight at 8,000'...
The oil pressure usually stays 3/4 of the way to the top of the green. Next scan I look to see its just barely in the green, the left side of the needle touching the yellow. It's never been there while running before. The needle occasionally jumps into the green, but spends most of its time borderline yellow.
I reduce power and head for home, cognizant of airports and places to land along the way. The engine continues to run perfectly well and the oil temp is exactly where it should be. I have two oil temp gauges. The OEM one and also a probe for the JPI engine monitor. They agree, all is well. All 4 CHT's are normal.
We land uneventfully back home at RLD. No oil on the engine and no oil on the belly. The correct amount is on the dipstick.
I think this is a faulty sending unit or instrument. I don't picture it being the engine but the plane is grounded. I gave the keys to my AI and he is backed up may be some time before he gets to it. What do you all think is going on?
FWIW the annual was completed 10 hours ago. My lowest compression was 78, the filter looked fine and there were no (known) squalks.
Thanks in advance,
Bill