Inverted P-51 question.....

[Wolf14]

How long was a P-51 able to maintain inverted flight before engine damaged occured?

[Airscrew]

http://www.courtesyaircraft.com/P51_prof.htm

PERFORMANCE
The maximum speed is 437 MPH at 25,000’. Normal cruise is 240 Knots at 65 GPH at 8000'. The aircraft is stressed for aerobatics and is capable of most all maneuvers with the exception of sustained inverted flight, snap rolls, outside loops, and inverted spins.

Ok so why is sustained inverted flight bad? this is not from a P-51 but perhaps is a clue?

http://www.mikeeynon.com/index.php?action=MJOURNAL&n=10

Next came the inverted flight. Ugh. I now realize why you spend $250 on harnesses in a plane. Normally when I have spent time inverted (loops and rolls), I have still had positive Gs holding me in the seat… going inverted sustained is a whole other story. My harnesses are pretty worthless, so pretty much the only thing holding me in the seat was my lap-belt which is nearly identical to the on in my M3. The net result is something akin to tying yourself to the seat with a piece of rope. VERY uncomfortable! As well, with that skinny lap-belt being the only thing holding you in… it dawns on you that if the belt were to break, you would fall right through the window in the roof! And then you have the negative Gs to contend with. When you are right-side-up, you barely notice a half G in either direction… inverted… you notice. Basically, if when you are right-side-up, you are experiencing 1G of force on your body, going inverted and exerting -1G on your body means that blood traveling to your brain is working with a 2G differential (1G - (-1G) = 2G). Add in another half a G of force, and it feels like you are gonna start bleeding from your ears pretty soon. I have been told that negative Gs are like positive Gs in that the more you do them, the more you get used to them… I have a long ways to go. After about 15 to 20 seconds… I had enough inverted flight for a while. Not to mention… the Citabria does not have an inverted fuel and oil system, so the engine completely dies, and oil starts spraying all over your plane.

So maybe the answer is the P-51 does not have an inverted fuel and oil system?  With the oil and coolant raditors on the bottom maybe inverted flight doesnt allow the oil and coolant to flow properly?

and now I re-read your question, duh.  I didnt see anything that gave a time limit

[nirvana]

If I recall it was a matter of seconds due to oil starvation but that was from an unreliable source, History or Military channel.

[Airscrew]

I cant say if its a good source, but...

The Mustang was an extremely well-made and excellent plane, although its coolant system could be shut down by a single bullet that pierced an external feed. Pilots joked that "A kid with a rifle could bring it down." In addition, according to the manual, the engine would become starved for oil if the plane was flown inverted for more than a few seconds.

http://en.allexperts.com/e/p/p/p-51_mustang.htm

[nirvana]

Depending on where the oil pickup is, I think most engines could only go inverted for a few seconds.  If the pick up resembles an automotive engine then it sits ~.5 inch above the bottom of the pan so it'd be toasted just that fast, 15-20 seconds absolute max.

[Airscrew]

nothing about how long but neat write up about flying a P-51

http://www.warbirdalley.com/articles/p51pr.htm

more good stuff

http://www.cebudanderson.com/mousetrap.htm

[Airscrew]

Originally posted by nirvana
Depending on where the oil pickup is, I think most engines could only go inverted for a few seconds.  If the pick up resembles an automotive engine then it sits ~.5 inch above the bottom of the pan so it'd be toasted just that fast, 15-20 seconds absolute max.

I dont have a Mustang manual but I would guess the oil is in a seperate tank like coolant and gas and is "pumped" or gravity fed to the engine?

[Airscrew]

check it out

http://www.p51.wjackparker.com/

there are some scans of the Mustang manual there

$30 for the CD with pics and manuals for a P-51

[Captain Virgil Hilts]

Good aircraft engines are dry sump, not wet sump like your average car engine. Dry sump means that an external pump scavenges oil from various points in the engine. However, they still scavenge MOST of the oil from the crankcase, by design. So, if the scavenge pickup(s) in the crankcase remain uncovered for too long, the engine will lose oil pressure, and eventually fail. In this regard, the Merlin is MUCH weaker than an Allison, because the oil system in the Merlin is already marginal.

[Airscrew]

just in case anybody wanted to read up on the Rolls Royce V1650 Merlin.
after reading it for a few minutes I'm guessing this might be for race modified Merlins so it might not apply to WW2

http://www.unlimitedexcitement.com/Pride%20of%20Pay%20n%20Pak/Rolls-Royce%20Merlin%20V-1650%20Engine.htm

The lower crankcase serves as an oil sump, and also carries an oil pressure pump and three scavenge pumps, with provisions for an optional hydraulic pump.   Baffles in he lower crankcase help reduce oil surge and improve oil control, particularly at unusual attitudes which can occur in flight.  Each of the two primary scavenge pumps is equipped with removable oil screens; one scavenge pump collects oil via an extension pipe to a pickup at the propeller end of the engine, the other scavenges oil from the sump at the supercharger end of the engine.  The third scavenge pump is the auxiliary scavenge pump used to collect oil from the supercharger impeller bearings -- it is located directly below the pressure pump.

[Wolf14]

Thanks for the reply guys. I was having some coffe and breakfast tacos at the local Kettle with a few friends and the topic came up. We did discuss oil flow and dry-sump oil systems, and then the question of "How Long? " came into play. I want to say at one point somebody in many threads back had said something in the neighborhood of :20- :30.

Since knowing the plane does go inverted during split "S's" , loops, and various other manuvers we all figured it was rated to be inverted to some extent, but the for how long was the 64 million kajillion dollar question.

[Ball]

if it is inverted but pulling positive G it doesnt matter?

[gripen]

Corky Meyer flew inverted figures eights with the Seafire in the Joint fighter conference so apparently the Merlin did pretty well inverted (assuming that it takes around thirty seconds to complete one figure eight).

[Treize69]

[AquaShrimp]

I was at an airshow where Chuck Yeager was the announcer, and he said that inverted flight should be no longer than 7 seconds.