John Davies,
It is simply not true that the Seafire turned at a higher rate than ANY version of the Zero. The A6M2, 3 5(a,b,c) all enjoyed a considerably higher turn rate than the Spitfire Seafire at all speeds up to 275 mph where the elevators would stiffen up to a level where the average pilot would find it hard to achieve full elevator authority.
As for the Seafire's climb rate, it didn't go past 4,100 fpm AFAIK, which is the same as the A6M5.
The A6M5's performance was as follows:
Max SL speed: 485 km/h (WEP)
Top speed: 565 km/h at 6km (WEP)
Climb rate: ~4,200 ft/min
The problem with this sort of performance comparison is the figures are pretty meaningless unless the source also specifies some extra data; like what mark are we talking about, at what height, and at what speed, is the rate of climb or rate of turn obtained, are we talking about normal continuous power or 5 minute emergency power, etc etc? Brown, who is my main source, is better than most, and seems to have done his research well, but even so he is not perfect.
Anyway, for the Seafire LIII, the main mark deployed in the Pacific, he quotes 4160 fpm at sea level, which accords pretty well with your 4,100 fpm, but the higher rate of 4,310 fpm at 6,000 feet, both at full combat boost. These figures are fairly close to Henning's calculated figures, if my reading of his excellent graphs, and conversions from metres per second to feet per minute are anywhere near right. The graphs also show that the Seafire LIII's climb advantage over the A6M2 ran out after about 8,100 feet, making it plain that this version of the Seafire was very much a low-level special.
As for rate of turn, Brown is unequivocal about this. I must admit, this did surprise me a lot, because I was under the impression that nothing turned inside a Zero, but it's all there on page 156 of the hardback edition.
He says that the Seafire's rate of turn (i.e degrees per second around a 360 degree circle) was greater than the Zero's, even though the radius of its turn was also greater; i.e the Seafire was going around a larger circle, but going round much faster; BUT (and it's a vitally important "BUT"), only if the Seafire pilot kept his speed up into his best fighting range, and above the Zero's best fighting speed…. because, as you quite correctly state, the controls of the Zero tended to stiffen up as speed increased. The aim was therefore to keep the speed up into the range where the Zero's manoeverability deteriorated. Pilot reports I've read, as well as Jeff Quill's "Spitfire", (a highly recommended read, BTW) suggest that the Spitfire's elevators remained light and positive at all normal speeds, but the ailerons did tend to stiffen above about 300. I expect the Seafire was much the same, as it was the same basic airframe.
Brown gives the Zero's best fighting speed as 180 mph, and the Seafire's as anything between 220 and 280 mph.
Incidentally, I was a little puzzled by one thing. Brown quotes speeds in mph, but to the best of my knowledge the ASIs of naval aircraft were calibrated in knots. However, his figures seem to check out well enough in mph against other published sources, so they are probably about right. Brown is also quite clear that at the Zero's best fighting speed, which he gives as about 180 mph, both its rate of turn and its radius of turn were quite definitely superior to the Seafire's.
I think I may have quoted Seafire fighting speeds in knots in an earlier post. If so, my mistake.
This was why the FAA's Air Fighting Notes made it clear that when fighting a Zero, it was very important to keep the speed up into the Seafire's best range, and fight in a series of climbing and diving near-stall turns. Being drawn into slowing down to the Zero's best speed was a recipe for disaster, so FAA pilots were strongly briefed not to do it.
Unfortunately, Brown does not give any figures for either radius of turn at different speeds, or rate of turn at different speeds, for either the Seafire or the Zero. It is this sort of thing that so often annoys me about printed sources.
Going back to page 12 of this thread, Parsifal comments that pilot quality may have had more to do with it than anything else. I have to agree. On p128 of the hardback edition, Brown describes a combat where Sub-Lieutenant G.J. Murphy, RNVR, took on not one but two A6M5s, in a turning battle, at their best fighting speed, not his, and shot them both down. (Maybe he hadn't read the FAA's Air Fighting Notes !) By any reasonable standards, he should not have won. He should have been shot out of the sky. This suggests that by this stage, well towards the end of the war, the Japanese pilots the Seafires met were not very good, and this may have as much to do with the Seafire's excellent kill ratio as anything else.
Two final points; firstly, quoted differences of a couple of hundred feet per minute one way or the other probably don't mean very much in practice. Quoted best rate-of-climb figures will have been derived from tests with a new aircraft in top condition, flown by a test pilot. How much service an individual aircraft has seen, what standards of maintenance are like, the way it is rigged, and pilot technique, can all account for at least 5% difference one way or the other, and if we are talking of rates in the 4,000 fpm range, that's 200 fpm, or about the quoted difference between Seafire and A6M5. So perhaps the only really safe conclusion is that both these aircraft had a best rate of climb somewhere over 4,000 fpm, and both were far ahead of any other carrier-based fighters of the period in this respect.
Secondly, the best-climbing Seafire of all was the LIIC, which was capable of 4,600 fpm at 6,000 feet at combat boost. Compared to this, the later-mark LIII, which was capable of the lower rate of 4,310 at the same height, seems like a retrograde step. Or maybe not.
On p22 of the hardback edition, Brown comments that the Merlin 55 and 55M, fitted to the FIII and LIII, had "….an automatic boost control and barometric governing of the full-throttle height. Hitherto these had had to be controlled by the pilot, and only experience could give an individual the ability to make the most of the engine's performance, at its best only under certain conditions of outside air temperature and atmospheric pressure."
Now I confess I don't really know enough about the care and feeding of large supercharged liquid-cooled piston aero-engines to understand exactly what that means in practice. If anyone can educate me, please do.
But I suspect it means that to get the best out of the LIIC's Merlin 32 meant fiddling with fine adjustments on the engine controls, feasible under test but undesirable in combat, whereas the LIII's full power was obtainable just by pushing the lever forward. So while it had a lower theoretical rate of climb than the LIIC, it was more easily attainable in practice.
So, quite possibly, the mark with the less favourable rate of climb according to the numbers might perform better in a practical situation in combat. Quite honestly, the further I get into the data, the more confused I get. It is very clear that there are no simple answers.