MIflyer
Captain
A book I am reading, Turning the Tide, seems to be a really well researched history of the USAAF in North Africa and Sicily and I have already learned a lot from it even though I am only in 40 pages or so.
But the author made a technical mistake on page 34, discussing the problems with the P-38's sent to the theater. I quote:
"The cooling system for the engines involved circulating air from the radiators into the leading edge of the outer wing. Because the radiator was too small for adequate cooling under desert conditions, and because this system for cooling the air turned out to be inadequate. the problem of engines overheating and failing was a common one for a pilot to deal with in 1942-43 North Africa."
Maybe there were cooling problems with the P-38 in the desert, but what he describes is completely wrong. The V-1710 is a liquid cooled engine and the only air going through the aft boom mounted radiators was that coming in the front and going out the back. Liquid coolant, Glycol, was pumped from the engine case back to the coolant radiators and then back up to the engines.
On the P-38's before the J model the leading edge of the outer wing was used to cool the pressurized air that came out of the turbosuperchargers before it was inducted into the V-1710 mechanical supercharger. The leading edges of the outer wings were used Intercoolers. This was clever and elegant design with very low aerodynamic drag. On B-17's the intercoolers were inside the wing and air had to be taken in through the leading edges of the wing, flowed through the intercooler, and then exhausted back out of the wing. But there were neither external nor internal fins to help with heat transfer in the leading edges of the P-38 wings and adding paint on the outside did not help, either. In the P-38H the engine power was limited by the limited cooling capability of the intercoolers. The P-38J introduced into production air to air intercoolers located in the cowling chin position and this solved the intercooler limitations problem but introduced a new and potentially more serious one, since the air/gasoline vapor charge going into the cylinders could get too cool, especially at high altitudes. So the P-38H engines could not put out all the power they were capable of while the P-38J/L engines occasionally blew up. At the 9th PRS in India they solved the intercooler overcooling problem on their F-5 recon aircraft by blocking off some of the cowling exhaust area, a solution that was possible since recon aircrafa tended to fly high and fast without much in the way of power charges, unlike fighters. In any case, for the P-38F and G models in N Africa the leading edge intercoolers certainly were not causing engines to overheat. The hot air was down low and the turbos really started boosting big time up where it was high and cooler.
Now, as for the engines getting too hot in the desert, the P-38F and G models did not have engine coolant radiators that stuck further out into the airstream as did the later models. For both the P-38 and the P-51 the designers figured out that separating the slow moving boundary layer air next to the fuselage from the faster moving air a few inches further out helped a great deal with improving cooling. This was even a problem with the intakes on the earliest P-80's; they had to add splitter plates.
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But the author made a technical mistake on page 34, discussing the problems with the P-38's sent to the theater. I quote:
"The cooling system for the engines involved circulating air from the radiators into the leading edge of the outer wing. Because the radiator was too small for adequate cooling under desert conditions, and because this system for cooling the air turned out to be inadequate. the problem of engines overheating and failing was a common one for a pilot to deal with in 1942-43 North Africa."
Maybe there were cooling problems with the P-38 in the desert, but what he describes is completely wrong. The V-1710 is a liquid cooled engine and the only air going through the aft boom mounted radiators was that coming in the front and going out the back. Liquid coolant, Glycol, was pumped from the engine case back to the coolant radiators and then back up to the engines.
On the P-38's before the J model the leading edge of the outer wing was used to cool the pressurized air that came out of the turbosuperchargers before it was inducted into the V-1710 mechanical supercharger. The leading edges of the outer wings were used Intercoolers. This was clever and elegant design with very low aerodynamic drag. On B-17's the intercoolers were inside the wing and air had to be taken in through the leading edges of the wing, flowed through the intercooler, and then exhausted back out of the wing. But there were neither external nor internal fins to help with heat transfer in the leading edges of the P-38 wings and adding paint on the outside did not help, either. In the P-38H the engine power was limited by the limited cooling capability of the intercoolers. The P-38J introduced into production air to air intercoolers located in the cowling chin position and this solved the intercooler limitations problem but introduced a new and potentially more serious one, since the air/gasoline vapor charge going into the cylinders could get too cool, especially at high altitudes. So the P-38H engines could not put out all the power they were capable of while the P-38J/L engines occasionally blew up. At the 9th PRS in India they solved the intercooler overcooling problem on their F-5 recon aircraft by blocking off some of the cowling exhaust area, a solution that was possible since recon aircrafa tended to fly high and fast without much in the way of power charges, unlike fighters. In any case, for the P-38F and G models in N Africa the leading edge intercoolers certainly were not causing engines to overheat. The hot air was down low and the turbos really started boosting big time up where it was high and cooler.
Now, as for the engines getting too hot in the desert, the P-38F and G models did not have engine coolant radiators that stuck further out into the airstream as did the later models. For both the P-38 and the P-51 the designers figured out that separating the slow moving boundary layer air next to the fuselage from the faster moving air a few inches further out helped a great deal with improving cooling. This was even a problem with the intakes on the earliest P-80's; they had to add splitter plates.
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