P-40L

Bretoal2 said:

Sorry, I don't agree at all.
The file "USAF model engines" indicated above clearly specifies "two speed supercharger" and gives the two mechanical gear ratios. This is totally independent from the contribution of a possible external tubocharger.

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In this case I strongly believe that the USAF model engines file is incorrect in relation to the -57 engines being fitted to the F-4/F-5/P-38 aircraft.

To quote TO 01-75F-1:



Furthermore to quote USAF model engines in relation to the engines listed above in TO 01-75F-1 it also lists that these engines were fitted to those aircraft. Maybe there was a project to fit -57 engines but if so there would also have been a corresponding F11L left hand rotation engine (because the P-38 REQUIRED both left and right rotation engines) and that is not shown anywhere in the chart. I therefore think this was just a error that was missed in proofreading.
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MiTasol said:

In this case I strongly believe that the USAF model engines file is incorrect in relation to the -57 engines being fitted to the F-4/F-5/P-38 aircraft.

To quote TO 01-75F-1:
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Furthermore to quote USAF model engines in relation to the engines listed above in TO 01-75F-1 it also lists that these engines were fitted to those aircraft. Maybe there was a project to fit -57 engines but if so there would also have been a corresponding F11L left hand rotation engine (because the P-38 REQUIRED both left and right rotation engines) and that is not shown anywhere in the chart. I therefore think this was just a error that was missed in proofreading.
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For the specific F-5D, the correct designation in these lists is "XF-5D," which indicates a project or prototype. One might think that the P-38's propeller rotation direction was changed during testing (supra-divergent then supra-convergent), and that it would be possible to have a P-38 model tested with engines in the same direction.

But this is impossible: Dan Whitney says that the V-1710-57 (F11R) was built in ONE unit, so it couldn't have been used on a twin-engined aircraft ! (Vee for Victory, p. 431).

We also see that there is a real error (typo?) in the list "USAF model engines ": according to Whitney, the V-1710-131 is a V-1710-G3R, not a C3 (ibid., p. 432). This model was built in eight units.

Conclusion: with 9 examples built, the V-1710s with dual-speed superchargers are totally marginal and never saw real service.

From Dan Whitney, op.cit. - words between [ ] are mine :

(page 269) F-11R : This engine was intended for the Curtiss P-53 airplane [a P-40 improvement, drawn after the XP-46 failure], and represented an effort to dramatically improve the efficiency of the Allison-designed [single] engine-stage supercharger then being used on all V-1710s. The V-1710-57 (F11R) was the first to use a two-speed supercharger, having th ability to shift between 6,44:1 and 8,80:1 drives. Contract ... was issued for one of these engines in October 1941, the engine was to be delivered the following March... The model test engine ... was actually completed on April,2,1942, and was unusual [carburetor change]... Particularly unique was the supercharger impeller, wich was an entirely new "lixed-flow" unit known as the "Birmann" supercharger... The impeller was of 10 1/4 inches in diameter and involved aspects of both centrifugal and axial flow in its design. The engine was otherwise similar to the F-10 ... Evidently the improvements shown were marginal and did not justify introduction into production at the time.

(page 280) G-3R : eight of these engines, were military versions of the proposed commercial G-2 model [a F-30 with a new two-speed supercharger], were built as V-1710-131 to power the Douglas XC-114 (a C54E derivative with lengthened fuselage) and YC-116 (similar but with thermal de-icing). Both were contempraries of the DC-4M "Merlinized" C-54..... The first engine went to test in December 1946.