Please....

[Widewing]

Originally posted by Widewing:
[QB]

Most references refer to the AVG planes alternately as P-40Bs or P-40Cs and sometimes Tomahawk IIBs. All small mouth P-40s/Tomahawks carried the factory H81 designation. Where the AVG planes differed was that they carried the unique factory designation of H81-3. Beginning with the P-40D/Kittyhawk I, they were designated as the Curtiss H87.

The AVG aircraft were a curious mix of Tomahawk IIA and IIB parts. For example, they were fitted with externally sealed fuel tanks, giving them the same fuel capacity of the P-40B (slightly greater than the internally sealed tanks of the P-40C and Tomahawk IIB). Unlike all of the Tomahawk IIB aircraft sold to Britain, the Chinese aircraft did not have a provision for an external fuel tank, nor the plumbing and fuel selector valve associated with it. That more closely resembles the P-40B. Because the Chinese contract allowed for a lot of wiggle room in the aircraft specification, Curtiss used excess parts from the USAAF P-40B production run. Because these fighters were so different from the anything else built, they received a special factory designation.

Another factor that has confused many over the years are the serial numbers. Since these aircraft originally came from a British contract, they were assigned numbers from that future production run. So, many historians and writers wrongly assumed that they came directly from that lot of fighters. They did not. The serial mumbers were assigned long before actual production began and before sub-contractors were began producing such items as fuel tanks, engines and the like. Indeed, Allison had to set up a seperate production line to build the Chinese engines, hand fitting previously rejected parts and components. This was due to the lack of production reserve.

AVG pilot Erik Shilling writes:

"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 horsepower and used less fuel than the standard US military, or British engines. This supplied the needed 100 engines and the balance came from a later production run. A follow 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 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 horsepower 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 Horsepower. (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 AA 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 horsepower chart, 50 inches was 1380 HP."

So, it seems that the AVG benefitted from having hand fitted, blueprinted engines that may have made a bit more power than the standard production model.

So, if HTC does model the AVG's H81-3, they should consider the above and consult with Whitney's Allison book as well.

My regards,

Widewing

[john9001]

P40 with a hot-rod engine.....kool