I wonder what the story was there ... looking at the test at :
Seafire Mk. III Trials
Using that as a starting point and moving to photos of BPF Seafires -- it seems like refinements would include:
- individual exhaust stubs instead of triple ejector fishtails and heaters
- small cannon bulges instead of large 'universal wing' bulges
- unused 20-mm stubs faired over instead of hemispherical blanks (I see quite a few examples of both, it seems)
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- Aero-Vee air filter instead of temperate air intake with snow guard ... I'm sure the larger air intake was a downside but I'm assuming there was no snow guard in the Pacific
- how prevalent was the +18 boost upgrade?
All things considered I would expect to see faster than the usual numbers I see quoted. Maybe the climate really knocked the wind out of it?
Only 103 Seafire F.III were built from the earliest aircraft on the Westland production line. By the end of 1944 only 887 squadron on Indefatigable still had them. In Jan 1945 the squadron had 24 (of 40 Seafires on Indefatigable), but that number fell until by July the squadron had 15 F.III and 9 L.III, as replacements were hard to come by. The F.III was fitted with the Merlin 55 rated at 1,470hp at +16lb boost at 9,250 ft.
The first L.III came off the production line in March 1944. That had the Merlin 55M engine with the cropped supercharger impeller & +18lb boost generating 1,585hp at 2,750 ft.
The final version was the FR.III (or LR.III in some references) which was an L.III with the same camera installation as an LR.IIc. Some conversions by Westland and the final 129 from Cunliffe Owen in 1945. Mike Crosley's personal mount while CO of 880 on Implacable in 1945 was FR.III NN621 coded 115/N. That was a Cunliffe Owen built aircraft produced around Feb 1945.
A lot of changes were made during the early Seafire III production days. Some came off the line with fixed wings (incl LR765) on which some later had folding wings substituted. Some early aircraft (incl LR765 the first F.III) had three bladed props although I note that this had been replaced on LR765 with a four bladed one by the time of the test. Individual exhaust stacks added some thrust (and reduced weight), the smaller wing blisters were worth 5mph. The air intake that LR765 came off the line with, was replaced early in production with the Vokes Aero-Vee filter common to later Merlin engined Spitfires as shown here:-
LR765 as originally built
Later production L.III
The outboard cannon stubs were deleted on the production line very early. From late 1944 the shorter & lighter Hispano Mk.V began to be fitted in place of the Mk.II. Very few of these seem to have reached combat before the end of the war however, although Implacable's squadrons do seem to have had a few. Big discussion about this a few years back here.
I have read that later versions of the Seafire lll LF were equipped with the faster firing, lighter weight and shorter barrel Mk V 20mm cannon in place of the heavier long barrel Mk II 20mm cannon. The Mk V cannon was 12 inches shorter than the Mk II cannon, and the cannon fairing covering the ba...
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Zero length rocket launchers became a possible fit but were not cleared for use before the end of the war despite Implacable's squadrons taking them to the Pacific.
There was a quality of finish problem with early Westland built aircraft. LR766, the second F.III built, was examined in detail and photos sent back to the factories to highlight areas for improvement. I've read that such poor finish could cut as much as 20mph from the top speed but whether it had any affect in the case of this test is not recorded. Cunliffe Owen is reputed to have produced the best quality Seafires but only produced 350 Mk.III compared to the c900 produced by Westland. The same effect was seen on aircraft in service, as they got bashed about and panels stopped fitting quite so well etc.