The first method seems like a match here as oil pressure is reportedly going down slowly over time. Taking apart piloting aspect of it prohibiting takeoffs at pressures outside of green arc, is that really healthy to run the new engine on a pressure that is 20 PSI lower than the end of the scale? How about risks to oil system components described by PDR?
Not sure if I understand you here but there is a subtle difference between starting with the pressure above the green arc and drifting down into it
(scifi) and what should happen which makes use of the drift down as well so I'll cover tht first. The pressure would initially be set to be at the
high end of the green arc and, over time, it may/would drift down. The periodicity for the check could either be "after x hrs, carry out a recheck of oil pressure and reset to (say) middle of the green arc if necessary" or it may even be an "on condition" callup - usually the former as it forces a check as it has already been noted how many pilots are happy to fly aircraft "out of limits"!
Now, the periodicity between checks would be such that, under normal run-in conditions, with the intial point set at Release (of the aircraft from maintenance), say, near the top of the green arc that, by the time the check is called up, it would still be in the green arc, but now at the lower end. If, due to a problem, the rate of pressure decrease was such that it went below the lower limit before the check was called, it would be assumed the a/c would be snagged anyway. If that was the case, a new check at "y hours" would be set up after re-adjustment and, if the pressure had dropped rapidly in the first instance, "y hours" may well be a reduced periodicity so that it could be monitored more closely by the engineers. If it continues to drop rapidly (ie goes below the green arc in under "y hours"), it should be snagged again and now time to do some fault investigation. So, in theory, the oil should never be outside the green arc and, during run in, should drift down at a fairly predictable rate (stats have their uses for design engineers!) from the high end of the green arc to the low end. It should never be planned to go outside the green arc. If it does, snag it!
Turning to the practical realities of running at a consitently low oil pressure? Not good! Things like extra wear as where oil is being forced into bearing journals, piston rings, valve guides etc, etc at a low pressure, it may not penetrate fully or as efficiently thereby providing partial lubrication leading to greater wear, higher operating temps etc, etc. Would your scenario cause an instant "smoking hole" - maybe not. Depends on a lot of things. But you are certainly helping to bring a very expensive bit of kit to an early end of life which no owner would want. Just like your car really. But here speaks an AV. Maybe the grubbers can add to this discourse!
Oh, and my bit about the "set it high and let it drift down" (i.e. initially well above the green arc and then letting it drift down into the green arc) being an "approved method" in my last Post is tongue-in-cheek - just to ensure I'm not mis-quoted!
But, if someone has a formally approved schedule which clears "driftdown" from above the green arc as being OK I'd be happy to upgrade my knowledge!
Cheers,
H 'n' H
PS Sorry such a long Post!!!
