investigating Governor oil supply error

[grafspee]

According to P-51 manual P-51 is allowed to 10s of inverted flight, but in DCS after 5s governor stops working despite oil pressure being at optimal level.

I can see two things, governor gave up too early and engine oil pressure is not affected in inverted flight, it will never drop no matter how much time you are in inverted attitude.

So since oil pressure not falling down, why governor quits ? A lot of inconsistent here, i can see.

Oil.trk

Edited September 23, 2022 by grafspee

[Magic Zach]

It also depends on your engine RPM.  Since the oil pumps are mechanically connected to the drive shafts (vertical one, for some engine accessories, including pumps).  Lower RPM should mean you'll be able to fly inverted for longer before your governor goes nuts.
I am surprised that all this doesn't register on the oil pressure gauge though

[grafspee]

@Magic Zach I'm not sure about that, since oil pressure is regulated by pressure valve so flow should be fairly constant. Oil will pump more oil at higher rpm but pressure valve will redirect more oil in to oil pump inlet.

Everything depends on oil pressure if oil pressure will drop at lower rpm then oil flow will decrease and oil tank should allow engine to last longer but if not time inverted should not change a lot.

But still thing is that oil pressure stays fine in inverted flight and despite that governor gives up, as far as i know governor is supplied buy engine oil pump so until oil pressure is indicated governor should work just fine.

Edited September 25, 2022 by grafspee

[Ala13_ManOWar]

In inverted flight the pumps don't stop working, they are just starved of anything to pump since oil is the other way around. Pumps break because they run "dry" for too long, but inverted flight itself has nothing to do with pumps themselves, I believe. I think you're statement is a bit misleading in that.

[grafspee]

31 minutes ago, Ala13_ManOWar said:

In inverted flight the pumps don't stop working, they are just starved of anything to pump since oil is the other way around. Pumps break because they run "dry" for too long, but inverted flight itself has nothing to do with pumps themselves, I believe. I think you're statement is a bit misleading in that.

Nobody is saying here that pumps stops working, P-51's engine contains 2 scavenge pumps and 1 main pump, engine has dry oil sump, and engine oil pump is feeded through oil tank which is reoiled by 2 scavenge pump. When plane enters inverted flight or negative g scavenge pumps will not transfer oil to oil tank, and main oil pump is supplied through oil tank which hold certain oil reservoir , this allow p-51's engine to be able to operate in those conditions. But after some time oil from oil tank runs dry.

P-51 manual claims that this reservoir is enough for 10 second and this is enough to finish every maneuver, but in case DCS governor fails after 5s and on top of it, it fails while oil pressure gauge indicate pressure which is even more inaccurate.

And one thing oil pump can run dry for very very long time, because oil leftovers are enough to provide lubrication for it.

Edited September 25, 2022 by grafspee

[Ala13_ManOWar]

Yeah, but you were mentioning governor, never mind.

I remember in the old days when the module first came out, people tested that and the 10 seconds were there. I guess the update to the engine cooling model was deeper than we can just glimpse.

[grafspee]

14 hours ago, Ala13_ManOWar said:

Yeah, but you were mentioning governor, never mind.

I remember in the old days when the module first came out, people tested that and the 10 seconds were there. I guess the update to the engine cooling model was deeper than we can just glimpse.

I know that, it used to be that P-51 could fly inverted until fuel runs out, fuel tank does not work inverted as well.

Thing is, that governor uses oil from engine, and governor may fail but first what should happen is oil pressure drop first. That is my concern.

Since there is no oil level gauge only thing which tells that oil pump is pumping oil is oil pressure gauge. If pressure is indicated every thing is fine. But not in DCS governor fail way before 10 s mark and before oil pressure drop on gauge.

Edited September 26, 2022 by grafspee

[NineLine]

I will ask about this, there is a current open bug report internally that deals with issues with the oil system so this might be related.