Erik Shilling
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HI Corey: Thought you may be interested int the following information on the Allison engines as supplied to the AVG. Some of this information was obtained from Dan Whitney an engineer that has done extensive research on the Allison engine. His 800 page book devotes a whole chapter on the AVG's Allison engine. He also feels, as I do, that the AVG was critical to the outcome of the war. Especially the fact that we kept China in the war at a most crucial time of the war. In June 1941 production was completed on 150 V-1710 engines that were used in the American Volunteer Group's fighter planes. Allison had received a request from China in January 1941 for engines to power their batch of Tomahawks for the planned AVG. Initially no production capacity was available. The British had previously reserved all available production. However the British traded 100 Tomahawks without engines, in exchange for a larger number of Kittyhawk, but the Chinese had to had to supply their own engines. Someone at Allison remembered that they had a warehouse of "off-dimension " parts, that didn't meet either US Army or British contract spec. but were otherwise sound. The proposal was that by hand fitting and matching and repairing these parts, suitably engines for the order could be provided. This involved fitting steel inserts that were plated to fit oversized tapped holes, con rod bearings altered to fit slightly undersized crankshafts, and dozens of other similar fixes were made. When tested these engines developed more horse power and used less fuel than the standard US military , or British engines. This supplied needed 100 engines and the balance came from a later production run. A flollow up on these engines that were made out of hand fitted matched parts were later found to have a better field record than the standard engines. These engines were built to Allison Specifications 145A, rather than Spec 120D and identified as the V-1710-C15A. There were no military designation for these engines. They were were assembled on a separate "Chinese" assembly line in Indianapolis to insure that none of the previously rejected parts would accidently be installed in US or British airplanes. The horse power ratings for V-1710-C15A for the AVG's Curtiss H81A-2 Tomahawks were the same as for the British V-1710-C15 and the Army's V-1710-33's. It is estimated that in the heat of the battle or disengaging from enemy fighters, some engines had drawn between 1600 and 1700 Horse power. (This would give a power to weight ration of better than even the vaunted Zero had.) At one time on a photo recon flight, while circling my objective, apparently I had run into my own prop wash, but at the moment thought it was A A fire. I pushed the throttle forward but when I settled down I saw that I pulling 50 in Hg, and quickly reduced it to 40 inches. According to the Horse power chart was 1380 HP. Although one revisionist reports that after the planes were built for the British, they were transferred to China for the AVG's use, this is not true. It was the contract that was transferred, not the finished Curtiss fighter. There is some confusion that has developed regarding the actual model Curtiss fighter we in the AVG flew. One area of confusion lay in the numbering system of two different Models. Their similarity in numbering cause the confusion, one was the H81A-2 which was the model flwon by the AVG, and similar to the US Army's P-40B. The other model's number was the H81-A2, a very subtle change, but this was the model similar to the US Army's P-40C. Which Ford insisted that the AVG had even though we have tried to explain the difference between the P=40 and C models. The difference between these two models was that the H81-A2 had fuel tanks internally sealed instead of external, it had shackles that could carry a 500 pound bomb, and was plumbed for a 52 gallon belly tank for longer range, and armor plate was installed between the two forward firing syn chronized fifties. Unfortunately on the later P-40C, had a big draw back in that it was that the slowest of all of the P-40 built. The AVG's H81A-2 was 355/360 mph at 14,500 feet compared to the H81-A2's speed of 340 mph. Since the Allison 's on the AVG's airplane developed higher HP than the Standard Allison, it is quite likely that the AVG's fighter had a top speed in the 370 mph range. Regards, Erik Shilling
