[tcolvin]

I believe this is the answer to the question asked by Nick Beale on June 20, 2010 (page 4 of the thread 'The RAF and dive-bombing').

Nick asked, “Can I change the question? Why did the USAAF give up on the A-36 in favour of the P-47?”


The short answer is that the order for 500 (only) A-36s was a USAAF subterfuge (or scam?) for keeping the Mustang/Apache (Allison V-1710 engine) in production after Lend-lease funds ran out and the 1942 USAAC budget for Pursuit fighters had been used up.

The USAAC budget for Attack aircraft, however, still had funds, which could be accessed by turning the P-51 into the A-36 (fitting air brakes and cannon).

By the time the 500 A-36s had been delivered, the USAAF had decided that the P-51B (Packard Merlin) was a long-range bomber escort with potential to achieve air superiority over the Reich alongside the P-47 Thunderbolt.

In this environment an act of Congress would have been required to build additional A-36s instead of P-51Bs.

As the A-36s vanished through attrition, the units operating them switched to old P-40s and then to P-47s or P-51s that could not perform dive-bombing.

None of these aircraft had the accuracy of the A-36, but no one in authority in the USAAF gave a monkey so long as the only complaints came from brown jobs.




The long answer:

1. Feb 1940; RAF (British Purchasing Commission) commissioned the North American NA73 fighter ('pursuit') plane concept with high-speed laminar flow wing, with ventral air scoop to eliminate drag through the 'Meredith Effect', and with 4 x 0.3-inch and 4 x 0.5-inch machine-guns. (BPC actually specified 4 x 0.303 mgs with first production a/c to be received by January 1941). The initial request was for NAA to produce the P-40 Tomahawk under licence, but Kindleberger said he could produce a better aircraft in the same time frame.
2. March 1940 – MAP ordered 320 NA-73 Mustangs.
3. May 5, 1940, design drafting began
4. Sept 9, 1940, completion of airframe, less engine
5. Sept 1941, 150 NA91/P-51 Apache/Mustang Mk 1A (4 x 20-mm cannon) ordered under Lend-Lease
6. Oct 26, 1940, first flight of NA73 with Allison V-1710 fitted with single-speed single-stage supercharger (Allison turbocharger wouldn't fit within the narrow Mustang airframe)
7. Sept 1941, first production delivery. MAP ordered another 300 a/c (cumulative 620).
8. Nov 1941, Mustang Mk 1A entered RAF service and 20 were sent to RAF Army Cooperation Squadrons as a low-altitude recce and ground support aircraft. It outperformed the Spitfire VC by 30mph at 5,000-ft, and by 35mph at 15,000-ft despite the Spitfire's more powerful engine. But above 15,000-ft, performance fell off. The RAF asked to see how the Mustang Mk 1A would perform when fitted with the Merlin engine (two-stage supercharger).
9. Of the 150 Mustang 1s built; 93 went to the RAF who fitted one with a Merlin at Loughborough, 55 were diverted to the USAAF for Photo Recce purposes, and 2 had trial installations of the Packard Merlin (XP78)
10. The USAAC wanted to order P-51s, but their 1942 Pursuit plane budget was used up
11. So instead, on April 16, 1942 the USAAC ordered 500 A-36s with funds from the 1942 Attack plane budget. This necessitated redesigned wings to contain A-31 Vengeance dive brakes and 500-lb bomb shackles
12. May 29, 1942, maiden flight of P-51
13. September 1942, first A-36 produced. One was delivered to the RAF as Mustang Mk1 Dive Bomber
14. November 30, 1942, first flight of XP-51B (Packard V-1650-3)
15. Early 1943, production of P-51B began as B-17s and B-24s were being shot out of the European skies. P-51Bs got absolute priority, and no more A-36s could conceivably be built. This was the death sentence for the only USAAC dive-bomber ever used in combat in WWII, and with great success.
16. Without new A-36 production, units operating them had to switch to P-40 Tomahawks, and then to P-47 Thunderbolts or P-51 Mustang fighter-bombers.

Tony