Ok guys, you almost have it right....
AVG Tomahawks were NOT Tomahawk IIBs, nor P-40Bs, or even P-40Cs. They were unique in that they were built to the Chinese contract.
British serial numbers were assigned to the Chinese fighters, but the serial numbers existed on paper only as the aircraft were not yet in production. When production did get underway, the Chinese aircraft would be different than those being made on the same line for the Brits.
Curtiss assigned these Tomahawks the different factory designation H81-A3. British Tomahawk IIBs were designated H81-A2. The reason for this is that these fighters were manufactured using a mix of components from P-40B and Tomahawk IIA spares as well as newer components. In addition, the Chinese aircraft had completely different fuel systems, virtually identical to the P-40B. Speculation is that Curtiss saw an opportunity to use the stockpiled spares, which had already been paid for at lower rates.
All 100 Tomahawks were delivered without normal "Government supplied equipment". That means that they were devoid of armament, radios and gunsights. It was up to Chennault's people to locate and procure these items, which is why some Tomahawks were armed with .30 and some with .303 caliber MGs. Two or three were armed with 7.92mm guns (standard Chinese rifle caliber).
Engines were built by Allison on a seperate assembly line. Since all of Allison's production was already earmarked and bound to existing contracts, Allison used a unique method to provide the 100 engines required. Each engine was assembled using parts rejected for the main assembly line due to tolerance issues. To do this it required hand fitting of components. Essentially, these engines would be built to tighter producton tolerances than the engines coming off of the main production line. When tested on the factory dyno, these engines proved to produce substantially more horsepower than the standard engine, roughly 200 hp more on average. Erik Shilling and Dick Rossi have both confirmed that the Tomahawks, even with tired engines, were marginally faster than the P-40Es received in the Spring of 1942. Shilling's stripped down, photo-recce bird was reported as being able to edge above 370 mph TAS. Shilling filled seams with auto-body filler and sanded joints smooth. Finally, the aircraft was waxed to a high gloss. This combination of added power, lower drag and weight gave the recce Tomahawk outstanding performance for its day. Standard AVG Tomahawks, in good tune, were reported to be able to commonly edge up to 360 mph TAS.
There was a major drawback to the extra horsepower. Despite that fact that the dyno tests revealed that these engines produced as much as 220 hp more than the production line V-1710-33s, Allison didn't beef up the reduction gearbox. This leads to a fact not picked up on as significant by historians. The AVG suffered a very high rate of reduction gear failures. This is better understood when you realize that the older style reduction gear (used weaker spiral type gears) was rated for no more than 1,100 hp. With as much as 1,220 hp on tap, the reduction gearbox was over-stressed and frequently stripped gears. Later models, with 1,200 hp engines were fitted with a much stronger spur gear design that could handle up to 1,600 hp. This is the major reason that the nose is shorter from the P-40D onward.
Our P-40B more closely represents the AVG fighter than it does a Tomahawk IIB. However, there are serious issues with its horsepower as the AH2 P-40B is at least 20 mph slower than a real P-40B, and probably 30 mph slower than the AVG's fighters. The AH2 P-40B can do no better than 332 mph at its best altitude.
Both Dan Ford and I have researched this to death. With help from Shilling and Rossi, we were able to track down the facts. Dan and I are in agreement as to the fact that the AVG flew unique aircraft, different from both RAF and USAAF versions of the H81.
By the way, Britain named the H81 series Tomahawks and the H87 series were named Kittyhawks. US P-40s, beginning with the P-40E were called Warhawks, but this name was almost never used by American pilots and ground crews, who would generally just call them P-40s.
My regards,
Widewing
