One off Curtiss P-40 prototype fitted with two stage supercharger version of the Twin Wasp

[fortrena]

I seem to recall that an early example of the P-40 was experimentally fitted with a two stage supercharger version of the R-1830 Twin Wasp.

Would anyone know when that one off machine first flew and what speed it eventually achieved, a few weeks or months later?

 

[Hardrada55]

I seem to recall that an early example of the P-40 was experimentally fitted with a two stage supercharger version of the R-1830 Twin Wasp.

Would anyone know when that one off machine first flew and what speed it eventually achieved, a few weeks or months later?

I gleaned this info from other sites on the web and my own files. In 1940, Pratt & Whitney purchased from Curtiss one of the first 199 P-40 (H81A-1) fighters, without an engine. The intention was to use this plane to test Pratt & Whitney's R-1830-SSC7-G Twin Wasp. R-1830-SSC7-G was an engine with a two stage supercharger. Figures for the P-40 airframe with the R-1830-SSC7-G engine, tested in September of 1942 showed a speed of 389 mph at 22,700 ft. I also saw reference to 389 mph at 19,000 ft. It climbed to 15,000ft in 5.5 minutes and to 20,000ft in 7,7 minutes using military power for the entire climb. In November of 1942 Pratt & Whitney reported that this plane performed much better than P-40F. The Pratt & Whitney engine sheet says the plane was a Hawk 81A and the photo doesn't seems to show guns in the wings or fuselage. The equipment and armament fitted is not known, but the P-40 (H81A-1) didn't have armor and self-sealing tanks.

 

[Justo Miranda]

The H75 inadequate performance at high altitude was a constant source of concern for the Curtiss Airplane Division staff.

In 1938 one H75 A-1 was modified as the H75 R high-altitude prototype, powered by one R-1830-SC2-G radial engine driving two centrifugal turbochargers, with ventral intercooler. During flight tests conducted in January 1939 the H75R reached a top speed of 330 mph flying at 15,000 ft. The USAAC considered insufficient the increase of performance and the H75 R unsuitable for operational service, due the complexity of the new propulsion system.

Curtiss continuing to perfect the concept, in 1943 the NX 28990 airframe of a H81A was powered by one R-1830-SSC7-G radial engine driving two centrifugal compressors housed in a new streamlined cowling. During flight tests conducted between July and October 1943, the high-altitude prototype reached a top speed of 389 mph and 25,000 ft of ceiling.

 

[jcf]

Justo, the R-1830 powered P-40 was not a Curtiss project, it was entirely a Pratt & Whitney development
and NX28990 was simply the civil registration assigned by the CAA on September 29, 1940.

The Curtiss serial number was 17816 which puts it directly in front of the final batch of Tomahawk IIB for the
RAF (c/n 17817 - 18116), it was not one of the first "199 P-40 (H81A-1)". The constructor numbers for the first
200 P-40s were 13033 through 13232.