Overheated Merlins And What To Do About Them

[Acheron]

All measures to keep a liquid-cooled engine flying require to throttle it down to minimum power, right? So, isn't the aircraft a sitting duck for the rest of the way? Maybe there weren't more cases of it, because flying in such a way in a combat zone was usually just too dangerous.

 

[MIflyer]

Maybe there weren't more cases of it, because flying in such a way in a combat zone was usually just too dangerous.

In the case of the Mustang pilot pumping his primer all the way home, he had a squadron of P-51B's around him. But there were other cases where Spit or Mustang pilots had to bail out when the radiator was hit and they had bunch of friends around, too. Maybe the later Mustangs had an electric primer and the same approach would not work, but you'd think that in other airplanes with the same problem and manual primers would have tried it.

I do not recall P-40's having that problem very much. One pilot who flew P-40's snd P-51's and was shot down when his radiator was hit in Korea said that the great thing about the P-40 for ground attack was that you were far more likely to get hit in the aft fuselage than the nose, so the P-40 was not likely to have the problem.

 

[warbird51]

I do not know if it is true, but I have read that the Merlin relied on oil cooling of the engine to a significantly higher degree than other liquid cooled engines of similar power. Even if this is true, it would not necessarily mean that it would make enough difference to allow the engine to keep on running for a significantly additional amount of time with the liquid cooling system non-functional.

I was told the opposite. The Merlin relied on the glycol cooling to remove most of the heat while the Allison was designed to have more of the heat generated removed by the oil system. The Allison could tolerate a 50% loss of coolant, but a Merlin could only tolerate a 20% loss of coolant. This was told to me by a pilot who has flown both Allison and Merlin aircraft.

 

[special ed]

Reference the rich mixture/prime pump cooling an engine I have had a positive experience if that in my 1948 Plymouth about 50 years ago. In my early teen years I read much of the available WW2 aviation books in the library. I had read of more than one occasion of using the primer to cool the engine and get a little more time from the engine. In the 1960s I was fully engaged in engines and old cars. I had just driven the old Plymouth onto a 24mile bridge and a hose blew. With no place to go and remembering the rich mixture cooling idea, I pulled the choke (manual choke in those days) until it ran rough, then in slightly, and watched the gauge ( analog ) until the needle moved back to half way between normal and Max. Got on across to a gas station. The old beast got an oil change and a new hose. Finally sold it two years ago.

 

[ThomasP]

Hey warbird51,

Now I am wondering which assertion is true, if either is true, or if both are true . . . er, wait now . . ??

 

[warbird51]

Hey warbird51,

Now I am wondering which assertion is true, if either is true, or if both are true . . . er, wait now . . ??

I have worked with a guy who has owned P-40's and flown Mustangs, and he was the one who said about the coolant issues. So for now I will go with his knowlage on this subject.

 

[Bigmerle]

Well, in the P-51H they took the oil cooler out of the radiator airscoop and located it in the engine compartment, which improved engine cooling considerably, eliminating the problem of the engine overheating while idling on the ground. So the oil cooler could not have required much airflow, even with the high powered -9 engine.

The -9 engine in the H used a water cooled heat exchanger mounted in front of the oil tank. Loss of coolant would mean loss of oil cooling so thet theory won't hold water.

 

[Shortround6]

Oil cooler was not tied in the engine coolant.
The oil cooler was tied in with the supercharger intercooler system.