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Also note that the NA-91 in the foreground has the early clamshell style radiator intake..
The borrowed a couple of A-36A's from the USAAF for recon, and provided them with Spitfire escort, but that plan fell through when the Spitfires couldn't keep up with the A36A's cruise speed.
I have the A-36 cruising at 400km/h, the Spitfire Mk.Vc at 518km/h and the Spitfire Mk.IX at 521km/h. Th
But what can the Spitfire V cruise at and get the same range as the A-36A?
Oftentimes the "efficiency curve" around best range airspeed can be rather steep, and the fuel penalties for cruising at a different speed rather high.I was just going with the "couldn't keep up" part
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Below 5,000 ft a Spitfire V and even a Spitfire IX would have difficulty keeping up with an RAF Mustang Mk.I, Mk.IA or Mk.II in level flight as the engines and in particular, the superchargers had been optimised for performance from 0 feet up to around 10,000ft with the best performance below 5,000ft. In the normal maximum throttle, without going to overboost, they could pull away from a Spitfire V or IX. Above 5,000ft the equation started to change, by 10,000ft the Mustang was "getting out of breath" and by 15,000ft, well and truly "running out of puff" and the Spitfires would be pulling away and climbing as well, especially the Spitfire IX.
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The low-level supercharger of the V-1710 as installed on Mustang I to II was more of a bug, rather than a feature. Reason to why Mustang I was able to pull away from Spitfires under 10000 ft was the low drag of the Mustang, not some great power developed by V-1710s (even though it could make it).
The Mustang II, whether in RAF or USAAF service, will not get out of breath by 15000 ft, let alone at 10000 ft.
I beg to differ. The RAF put in place specific modifications to the supercharger and other engine modifications to the Allison V-1710 engines installed in their Mustang Mk.I, Mk.IA and Mk.II aircraft. The RAF through those modifications optimised the engines efficiency for low level work below 10,000 ft with optimum performance below 5,000ft.
Back to back service testing by the RAF of Allison engined Mustangs with the standard engine and the engine with their set of modification to improve its low level performance, showed the increase in power and airspeed attained within the altitude range they were interested in for the low level operations of the Mustangs. It also showed the dramatic drop off in the power developed by the modified engines at 10,000ft and altitudes above that. Having researched this matter, interviewed and corresponded with many RAF and Commonwealth Air Force pilots who flew Allison engined Mustangs on an almost daily basis on operations between 1942 and 1945, and who in some instances were involved in the development and testing of RAF modifications to the Allison engined Mustangs, it was the RAF specific engine modifications, combined with the airframe that gave the low level performance. The RAF also operated their Allison engines at low level with levels of boost that the USAAF on receiving the initial reports from the UK did not accept and were sceptical about. The RAF engine modifications were able to produce and sustain these high levels of boost for relatively long periods, without significant long term impact on the overall service life and maintenance requirements for the engine. It took some time before the USAAF and engineers from Allison were able to accept the performance and service life figures the RAF was getting from the Allison V-1710 engines with the RAF specific set of service modifications.