Spitfire mk VB/Seafire vs Zero

[Soren]

The A6M2 climbed at around 3,250 to 3500 ft/min, which is higher than any Allied fighter of the period.

As for turn performance, the Zero, throughout its versions easily outturns any Allied fighter.

Now a highly boosted Spitfire V should be able to follow the Hap through a sustained turn at high speed, no problem, there are other a/c capable of that as-well, but all the Hap pilot has to do is pull in tighter the stick and he's away, the Spitfire simply can't hope to follow.

The Zero turns a LOT tighter than any Spitfire, which is what the Japanese pilots took advantage of when fighting it, pulling such tight turns that the Spitfire pilots were forced to utilize energy tactics if they were to survive. Now unfortunately the British hadn't developed efficient tactics against a fighter like the Zero when they came to fight it in the pacific, and were forced to learn it the hard way just like the US years before.

 

[HoHun]

Hi Renrich,

>The early F4F3s had an initial rate of climb of more than 3000 fpm.

According to my calculation, it arrives at 3000 rpm almost spot-on, almost matching the A6M2 ... but this favourable comparison is due to the power peak the R-1830-86 provides at low altitude with the supercharger in "neutral" gear.

Still, the F4F-3 due to its lighter weight (I used the 7065 lbs from the table accompanying Kohn's article) has more of an advantage over the heavy F4F-4 than one might think at first ... here are the graphs.

Regards,

Henning (HoHun)

 

[John Davies]

The A6M2 climbed at around 3,250 to 3500 ft/min, which is higher than any Allied fighter of the period.

As for turn performance, the Zero, throughout its versions easily outturns any Allied fighter.

Now a highly boosted Spitfire V should be able to follow the Hap through a sustained turn at high speed, no problem, there are other a/c capable of that as-well, but all the Hap pilot has to do is pull in tighter the stick and he's away, the Spitfire simply can't hope to follow.

The Zero turns a LOT tighter than any Spitfire, which is what the Japanese pilots took advantage of when fighting it, pulling such tight turns that the Spitfire pilots were forced to utilize energy tactics if they were to survive. Now unfortunately the British hadn't developed efficient tactics against a fighter like the Zero when they came to fight it in the pacific, and were forced to learn it the hard way just like the US years before.

I'm very sorry, but that's quite simply incorrect. Brown in "The Seafire", (Ian Allen, London, 1973), quotes the rate of climb figures for the Seafire LIII (the main variant used in the Pacific) as 4,160 fpm at sea level and 4,310 fpm at 6,000 feet, this powered by a Merlin 55M with its boost sytem optimised for low to medium levels. The FIII, the other version used in the Pacific, climbed at 3,650 fpm at sea level. Climb for 6,000 feet is not given. But anyway, the FIII slightly outperforms the climb figures for the Zero you give, and the LIII well outperforms them. The Seafire was remarkable not only for its high rate of climb, but its steep angle of climb, and was one of the very few allied fighters to nullify one of the Zero's main advantages; the Japanese pilots could no longer out-climb an opponent.

To add a little context to those figures, the Seafire LIIC, which as far as I know was only used in the European theatre, had a maximum rate of climb of 4,600 fpm, using a Merlin 32 with +18 lbs boost, which suggests a short life and a merry one for the engine!

The Zero did NOT out-turn the Seafire, easily or otherwise. What FAA pilots found was that the Zero had a tighter radius of turn, but the Seafire had a much higher rate of turn; i.e it was going around a larger circle, but going round it sufficiently faster to keep safely ahead of the Zero. In a full 360 degree circle, the Seafire would get all the way around first, but the Zero would travel a shorter distance, going around a smaller circle; but going around it more slowly.

Of course, this was not ideal. The Seafire pilot's aim was to get behind the Zero, to acheive a firing position, not hurtle merrily along in front. So the FAA used the tactic of alternate climbing and diving turns, in efect a series of near-stall turns, to get behind the Zero. These tactics worked from the first, so I am not sure why you suggest the British forces "had not developed efficient tactics".

Also, the Zero's best fighting speed was found to be about 180 knots. The Seafire's was anywhere between 220 and 280, which was a nice broad range giving lots of room for manoevre. FAA doctrine was to keep speed up into their own range. If the Zero pilot attempted to match this, his own manoeverability would degrade, and again give the Seafire the edge. The Zero was only really a very manoeverable aircraft at its best fighting speed. Controls, and especially ailerons, became much heavier at higher speeds. This greatly increased the effort needed to horse the aircraft about, and reduced rate of roll, vital in combat. In contrast, the Seafire excelled in the rolling plane. I'm sorry I do not have degree per second figures, but Brown does comment that it was exceptional in its ability to enter a hard roll sharply and positively, and reverse its turn quickly. The only enemy fighter which had an advantage was the Fw190, and even there, the advantage was not a large one.

"Proof of the pudding"? FAA Seafires shot down either 15 or 16 Zeroes for the loss of one of their own. The loss was because the pilot, Sub-Lt Hockley, suffered a radio failure, and was not aware of the need to break until it was too late. He had the appalling bad luck to be killed on the last day of the war.

BTW I know those kill figures are based on pilots combat reports. Brown's Appendix Three lists every Seafire combat individually, so I suspect when he was doing his research he simply went down to the Public Record Office and got the original squadron documents out. And I know everyone over-claimed, which does NOT imply dishonesty. In the heat and confusion of battle, it is impossible to be completely accurate, and all fighter pilots were optimists. If they weren't, they would never have been fighter pilots in the first place. But even allowing for a bit of over-claiming, it is clear that the variants of Seafire deployed in the Pacific enjoyed a decisive superiority over the Zero.

It has been suggested that a kill should only be regarded as authentic if it is confirmed by the documents of BOTH sides; one side's combat reports, and the other side's loss records. I'm sorry, but I am not going to go there. Even assuming that everyone's records are complete, accurate and available (a VERY large assumption), if we applied that consistently, we'd have to revise the combat totals for everyone; Hartmann, Kojedub, Bong, Johnson, Boyington, the lot. Safer, I think, to simply say that all combat reports overclaim a bit, and leave it at that.

Seafires did have some real weakenesses. They were a poor deck-landing aircraft, and short of range. Both these disdavatages were because the design was an adaptation of a land-based design. But by early 1945, FAA squadrons in the Pacific had to some extent overcome both problems. Deck-landing accidents were down to well under 2% of sorties, and by scrounging some 89 gallon drop tanks designed for P-40s, they had got the strike radius up to over 200 nautical miles, and patrol endurance on station up to over three hours; respectable figures by any standards.

The Seafire's reputation had been crucified by the fiasco at Salerno, where they were badly misused, resulting in a casualty rate of 10% of aircraft written off per sortie in deck-landing accidents, plus many more minor accidents. Understandably, it took a long time to recover.

As for what the RAF and RAAF's experience was with their Spitfires against the Zero; sorry, I haven't a clue! I'd suspect a lot had to do with the Mark (the Mark VIII, deployed late in the Pacific war, had a much higher performance than the Mark V), and the tactics used. I think the title of this thread can lead to some confusion, as it is about comparing both the Spitfire Mk V and the Seafire with the Zero. The fact is, the Sptifire Mk V and the Seafire LIII/FIII were very different aircraft; different performance, different tactical enviroments, different services, and very probably different tactics too. So comparisons which are valid for one will not be valid for the other.

The Seafire LIII and FIII were specifically optimised for performance at low to medium levels. They were very effective aircraft. Also, the FAA learned very fast, and as a "poor relation" service, was usually very good indeed at improvisation. It had to be; but in a war where the ability to learn and adapt fast often made the difference between life and death, this was no bad thing.

 

[Glider]

Interesting post, I knew that they used P40 tanks but didn't know how much difference it made.
Thanks

 

[HoHun]

Hi John,

>The Zero did NOT out-turn the Seafire, easily or otherwise. What FAA pilots found was that the Zero had a tighter radius of turn, but the Seafire had a much higher rate of turn; i.e it was going around a larger circle, but going round it sufficiently faster to keep safely ahead of the Zero.

Hm, I guess this is a bit like the turn rate comparison I posted earlier in the thread ... a bit difficult to interpret. I have prepared a new turn rate comparison for the A6M2 and the Seafire LIII - it doesn't seem to leave much room for the Seafire LIII out-turning the Zero by turn rate if both go for the optimum rate turn.

>The Seafire LIII and FIII were specifically optimised for performance at low to medium levels.

The Seafire LIII certainly was a pure low-altitude aircraft. The A6M2 would seem to have an advantage above 4000 m altitude in all of the main performance criteria, though the medium-altitude FIII would compare more favourably at these altitudes.

I guess it would be more meaningful to see a comparison against the heavier but more powerful A6M3 and A6M5 variants, but I'm afraid I have no good engine data on these aircraft as the TAIC data seems a bit suspect ...

Regards,

Henning (HoHun)

 

[John Davies]

Interesting post, I knew that they used P40 tanks but didn't know how much difference it made.
Thanks

Thanks. I'm glad you found it informative. A few more points; and please note I'm away from home tonight, and writing without access to my reference books, completely from memory (so please check and correct as necessary!)

1) Tanks; there were already extra tanks available for the Seafire/Spitfire series. They came in three sizes; 45 gals, 90 gals, and a huge 180 gal ferry tank. They were "slipper" tanks, i.e the upper surface of the tank fitted flush to the lower centre section of the aircraft. They were not quite the best thing ever to come out of the Supermarine design office. Actualy, they were pretty horrible. Because the connection to the aircraft's fuel system was not accessible when the tank was in place, it was impossible to inspect it and make sure it was properly connected. So sometimes they did not feed properly. Also, sometimes they hung up and would not jettison. FAA Seafire wings in the Pacific were issued with 45 gal slipper tanks, which did not extend their range enough. One wing scrounged some 90 gal slipper tanks from the RAF. Because of the inherent faults of these tanks, they were restricted to flying CAPs close to the fleet. The other wing scrounged 89 gal P40 tanks from the RAAF. These worked very well, (they were hung on the central bomb carrier, and the fuel connection was visible and positive) and Seafires so equipped ranged far and wide, sometimes to the far side of Honshu.

2) The rate of climb figures I quoted for the Seafire in my last post are at full combat boost, which was sustainable for five minutes. I don't know what happened in the sixth minute. Maybe the conrods came out through the sides of the crankcase. However, if a Seafire pilot was fighting a Zero, he'd use combat boost, so these seemed to be the figures to quote. Climb figures at maximum sustainable boost are less, but still very respectable. I'll dig the figures out of Brown, if anyone wants them, when I get home.

3) "The Seafire" by David Brown, seems to be the only standard work on the aircraft. Yes, I know it is not best practice to rely too much on one source, but there doesn't seem to be much else. If anyone can recommend another source, please let me know. I'd be interested. Brown seems to have done his research well, and to use his data with care. It is long out of print, but it still seems to be available from THE SEAFIRE - BROWN, DAVID. There also seems to be a paperback edition available at Amazon.ca: The Seafire: David Brown: Books. I don't know about this one. My copy is the hardback.

4) The Seafire LIII and FIII used versions of the Merlin 55. Now if my memory serves me right, this was the engine fitted to the Spitfire Mk VIII, which was designed as the ultimate Merlin Spitfire. Note, the Seafire LIII/FIII was NOT a hooked Spitfire VIII. The Spitfire VIII had various aerodynamic improvements, which the Seafire LIII/FIII did not. If you think of a Spitfire VIII powerplant in a navalised Spitfire Mk V airframe, you'll not be too far off. Navalisation included a hook (of course), some longitudinal strengthening, so the aircraft did not come apart as the hook engaged, catapult attachment points, and most importantly of all folding wings. The previous mark, the Seafire LIIC, had quite startling performance, but did not have folding wings, so its usefulness was severely limited.

5) Bearing in mind the foregoing, comparisons with the Zero which treat the Seafire LIII/FIII as very approximately equivalent to the Spitfire Mk VIII will not be too far out. Same powerplant, similar (but not identical) airframe. Comparisons with the Zero which treat the Seafire LIII/FIII as equivalent to the Spitfire Mk V will be very misleading. Early Seafires had been basically hooked Spitfire Mk Vs, but by the time the Seafire FIII/LIII series arrived (which were the marks used against the Japanese) a good deal of development had taken place. Add to this the fact that many RAAF Spitfire Mk Vs seem to have used the horrible deep tropical filter (good for a performance penalty of 30 mph any day) and you can see that to throw them in with the marks of Seafire used against the Japanese is really not comparing like with like, and bound to lead to confusion.

6) Keeping track of the development of any WW2 combat aircraft is difficult, as modifications and tweaking were constant. But the Spitfire/Seafire series is one of the more difficult. There were well over thirty marks, most of which were in service during WW2. This is not counting sub-types within marks, which were legion, let alone field modifications. Offhand, I cannot think of another major combat aircraft whose development history is quite so complex. Keeping track of it is a bit of a nightmare. This is NOT helped by some sources who are downright sloppy with their use of data. For instance, I can think of one online source which quotes a range for the Spitfire Mk V which makes it obvious that one of the slipper tanks was in use; but they don't say which size. That's only one example of many. There are many others.

7) One of the beauties of this sort of forum is that it provides a venue where these details can be sorted out. And, as a newcomer, may I say how much I have been impressed by the standards of courtesy shown by the vast majority of posters? Compared with some online environments, it is really very pleasant. It is nice to be debating with people who know how to disagree (sometimes quite strongly), while still remaining completely courteous about it.

 

[Glider]

I know its digressing a little but on Malta they didn't have any long range tanks for the Spitfire so they used two 45 gallon drop tanks from Hurricanes and put them under the fuselage, not the wings. It did look a bit odd but obviously worked and they could be dropped.
Presumably they had a similar improvement on the range of the Spitfire.

 

[kool kitty89]

Did they ever use the 108 US Gal (90 imp) cylinderical paper tank on the belly of the Spit/Seafire? (tank used for Hurricane ferry flights on the Hurricane's wing pylons, and sometimes used by P-51's)

I'd immagine it would have been easier than the 2x 45 gal Hurri tanks. (assuming there was enough ground clearance)

And didn't some Spits have pylons for wing tanks?

 

[HoHun]

Hi John,

>If anyone can recommend another source, please let me know. I'd be interested.

At least with regard to performance data, WWII Aircraft Performance is quite interesting as it reproduces tests for various Seafire models with Merlin 46, Merlin 32, Merlin 50, Merlin 55 and Merlin 55M.

>4) The Seafire LIII and FIII used versions of the Merlin 55. Now if my memory serves me right, this was the engine fitted to the Spitfire Mk VIII, which was designed as the ultimate Merlin Spitfire.

The Spitfire VIII (Like the Spitfire IX) actually had a 60 series Merlin engine, which had a two-speed, two-stage supercharger with intercooler so that it was more of a high-altitude engine. The Merlin variants used on the Seafire all had a single-speed, single-stage supercharger, in the case of the Merlin 55M even with a "cropped" supercharger impeller to further boost low-altitude power.

Here is a good overview of Merlin engines:

Rolls-Royce V1650 Merlin Engine

Accordlingy, the Seafire really was much like a Spitfire V in its performance characteristics, with the additional weight and drag of the carrier equipment leaving it without the excellent high-altitude performance the Spitfire IX and VIII were famous for. I'm not sure why the Merlin 60 series was not used for the Seafire - the rearward centre-of-gravity position Crosley describes would probably have been improved by the fitting of the two-stage engine, just as it was later improved by mouting the Griffon. Maybe the extra weight that did not result in any extra low-altitude power for take-off was the reason to stay with the single-stage Merlins?

>Add to this the fact that many RAAF Spitfire Mk Vs seem to have used the horrible deep tropical filter (good for a performance penalty of 30 mph any day) [...]

Hm, I believe there were different tropical filter versions and I'm not sure which one AB320 used, but the penalty doesn't seem to have been quite that heavy: "This aircraft was fully tropicalised; this included an air cleaner installation whose fairing produced an external bulge beneath the nose, and tropical radiator and oil cooler installations."

Spitfire Mk.VB (Tropical) AB.320 Report

I have extended my comparison to include a Spitfire Vb running at +9 lbs/sqin that is equivalent to AB320. As you can see, the Seafire LIII with its cropped supercharger easily outperforms the tropicalized Spitfire Vb below 3 km, but at 4 km and above, the Spitfire Vb really is superior.

Regards,

Henning (HoHun)

 

[parsifal]

But even allowing for a bit of over-claiming, it is clear that the variants of Seafire deployed in the Pacific enjoyed a decisive superiority over the Zero.


I have to respond to that by saying that the large kill advantage enjoyed by the seafire over the Zeke, was mainly because of poor pilot qulaty, rasther than the inherent weaknesses of the zeke design. in the hands of a skilled pilot, a zeke was still a formidable opponent. The evidence of this is harder to find, as the war progresses but its there. The performance of the Phil Sea survivors, against the US counterattack, where just 35 zekes gave good account against more than 200 attackers, with a heavy Hellcat presence. This at least suggests, that inthe hands of an experienced pilot, the zeke was an adversary desrving of respect. One wonders how the seafires would have performed if they had been up against decnt pilots in 1942. in 1943, the land based equivalents of the sefire, at Darwin apparently did not do that well at all. This, i believe was because the pilots that flew them tried to employ dogfight tactics against the Zeke, which was a dogfight machine perfecto.

 

[John Davies]

Thanks all of you. Of course the Spitfire Mk VIII had a Merlin 60! (That'll teach me not to post late at night and tired and from memory without any books handy!) And I even know a group of people who are in the early stages of restoring a Mk VIII. I really ought not to have dropped that, and I hope none of them are reading this! My apologies, anyway. I very much stand corrected, and am perfectly happy to.

The Merlin 55M had a cropped supercharger impeller precisely because it was designed for use at low to medium level. If the air is dense enough, there is less point in using up engine horsepower to motor a supercharger. This meant that almost the full power of the engine was available for climb, or acceleration, or takeoff (Seafires were not usually catapulted, they usually wound up and went). Obviously, at higher altitudes, where the air is thinner, a supercharger is needed to pack a full charge of fuel/air mix into the engine to get a decent performance, even a two-stage supercharger with intercooler.

The RN saw the Seafire as being primarily tasked with the defence of the fleet. They saw this, logically enough, as taking place at low to medium level, so optimised performance for those levels. The Seafire would out-perform most carrier fighters up to about 10-12,000 feet. Brown has some figures on pounds-per-horsepower, which makes it plain that the Seafire's power-to-weight ratio was higher than the Hellcat or Corsair; in its best range. But at higher altitude, the big American aircraft came into their own because their engines were better supercharged. Going from memory, again, but I'm pretty sure they had two-stage set-ups.

Drop tanks; the problem was indeed ground clearance. A circular section tank of any useful capacity would foul the ground in the three-point attitude. The tanks designed for the P-40s had an oval, flattened section, for the same reason. They fitted the Seafire's central bomb rack very well. I confess I hadn't heard of what the Malta Spitfires used.

This meant that the Seafire's usefulness as a strike aircraft was restricted. If you carried a drop tank, you couldn't carry a bomb. If you carried a bomb, you were restricted to limited range on internal fuel. And in any case, it was difficult for the Seafire to deliver a bomb with any accuracy. A good deal of guesswork was involved.

Some RAF Spitfires were equipped to carry a 250 lb bomb under each wing. Apparently this sometimes caused structural problems. Seafires were not. Rockets were not fitted to Seafires until after the war. So if a Seafire was used for ground attack, its weapon was mostly its cannon, which did lay down a useful path of splinter damage each side of the direct impact area; but then just think of all that vulnerable liquid-cooling pipework waiting for a round from light AA. I'm surprised the FAA didn't lose any in this sort of mission. Mostly, they were tasked as escort/cover to proper strike aircraft, or as interceptors in a defensive role. This they did very well, hardly surprising, as that was what the basic airframe had originally been developed for.

I can understand why RAF/RAAF pilots might have tried to dogfight the Zero in their Spitfires. Until it met the Zero, the Spitfire had been the dogfighter supreme, exploiting its ability to to turn inside its opponents. So using tactics that had been successful against other opponents must have been tempting. But fighting the Zero in a turning battle around the Zero's best fighting speed would have been simply asking for trouble.

I've already covered FAA doctrine; keep your speed up into your best range, fight on your terms, not his, never try to match the Zero's radius of turn, exploit your higher rate of turn. Most fighter vs fighter combat is about playing to your aircraft's strengths and to your opponents weaknesses, so it seems that the FAA had it well worked out, possibly better than the RAF.

Poor Japanese pilot quality in the closing stages of the war: I must confess, I had wondered about that. Brown gives an account of a Seafire pilot who did fight a Zero, on the Zero's terms (a turning battle around 180 knots), and won. He should not have done. He should have died. Unless, of course, the Japanese pilot was not very good. It's an intangible factor, unpredictable, impossible to quantify, and likely to be as important as everything else put together.

Comparisons/equivalency between the Seafire LIII and the Spitfire Mk V? I'm still not happy about this, because of one factor; the Seafire's startling rate of climb at full combat boost. I haven't seen figures which suggest that the Spit Mk V matched the Seafire in this respect (although figures I have seen are infuriatingly vague, and don't make plain if they are referring to continuous maximum or to five minute combat power for the Spit, so thanks very much for the detailed info on the various marks of Merlin!).... but anyway, a rapid and steep climb was especially useful against the Zero, and FAA tactics obviously exploited it to the full.

Henning thanks VERY much for the graphs on rate of climb. Loads of good info there, and I confess I haven't absorbed it all in detail yet, but they really do fill in a lot of the gaps. The comparison with the Spit Mk V is especially interesting. It seems to confirm what Brown suggests, the Seafire LIII had an edge up to about 10-12,000 feet, and rather runs out of steam higher up. In other words, it was good at what it was designed for; the defence of the fleet at low to medium altitudes.

Tropical filters; there were two main kinds, the Vokes and the Aboukir. One was quite small and discreet. The other one was huge, and hung below the nose looking rather like a pelican's beak. Trouble is, I can't remember which was which. (Help, someone?). But anyway, I have seen a performance penalty of 30 mph quoted for the big one, and I have seen pictures of RAAF Spitfire Mk Vs fitted with it. It cannot have helped.

 

[John Davies]

Henning thanks again for the graphs. Having had some time to absorb them, they really do show just what a highly specialised aircraft the Seafire LIII was; also just what a substantial edge it had within its area of specialisation, and just how comparatively useless it was outside it. Fortunately the RN used it within its area of specialisation, which doubtless is a major reason for its success.

I'd got roughly the same picture from a close reading of Brown. But a good visual presentation is much more striking. It can also convey much more information. So I am very grateful indeed.

One of the things I have already come to love about this forum is the amount of good hard info that is available from it. I get so TIRED of some of the stuff that is around in published sources; rates of climb quoted without making it clear if this is at normal max or full combat boost, a best rate of climb quoted without saying at what altitude the aircraft achieved it (good one, that, and far too common); I've even seen one source say the Seafire was deployed on CAP "because it was an efficient high-altitude fighter", the one thing which by any reasonable standard it was not. So this forum is a welcome breath of fresh air, and I tell you it is a complete education for me!

 

[Wildcat]

Tropical filters; there were two main kinds, the Vokes and the Aboukir. One was quite small and discreet. The other one was huge, and hung below the nose looking rather like a pelican's beak. Trouble is, I can't remember which was which. (Help, someone?). But anyway, I have seen a performance penalty of 30 mph quoted for the big one, and I have seen pictures of RAAF Spitfire Mk Vs fitted with it. It cannot have helped.

All the MkVc spitfires which defended Darwin were fitted with the bulky Vokes filter. I'm not very knowledgable in this field, but it's worth mentioning the fact that the RAAF did trial a locally built air filter to replace the vokes in the hope to improve its performance at high altitude. IIRC the improvement was hardly worthwhile and not adopted. Someone else might be more clued up on this then me.

Pic I took of a RAAF MkVc with Vokes filter as fitted to spitfires of 79sqnRAAF in the Pacific.

 

[HoHun]

Hi John,

>Henning thanks again for the graphs. Having had some time to absorb them, they really do show just what a highly specialised aircraft the Seafire LIII was; also just what a substantial edge it had within its area of specialisation, and just how comparatively useless it was outside it.

You're welcome, and I fully agree with your assessment

Not a Seafire story, but I believe Pierre Clostermann in his book mentions a mission with 'clipped and cropped' Spitfires excorting Hurribombers, describing how nervous they were because they knew they were flying at the top of their "good" altitude band. If they had met Luftwaffe aircraft, they'd have had a hard time climbing above them to start the fight with an advantage.

>I get so TIRED of some of the stuff that is around in published sources; rates of climb quoted without making it clear if this is at normal max or full combat boost, a best rate of climb quoted without saying at what altitude the aircraft achieved it (good one, that, and far too common)

Absolutely! I have to say that members of the community have done much more to address this shortcoming than the authors of the books that fill our shelves. Mike William's site (WWII Aircraft Performance) is a regular treasure for example, but many other people have contributed valuable data as well - improving our understanding of WW2 aviation far beyond what one might learn from the books

Regards,

Henning (HoHun)

 

[HoHun]

Hi Wildcat,

>Pic I took of a RAAF MkVc with Vokes filter as fitted to spitfires of 79sqnRAAF in the Pacific.

Thanks a lot for the great pictures! The one with the reflection on the starboard glazing of the canopy is most intersting - seldom does the bulged look show so clearly in a photograph!

I have to admit that the looks of the Vokes filter are slightly shocking indeed. In addition to the drag penalty it applied, it also reduced the useful ram effect to insignifant proportions. In my analysis, I had to reduce it to 15 % ram efficiency to match the historical figures, while normally I'd use 60 to 70 %. You can see from the graphs that, unlike for the Seafire LIII, there is hardly a difference in full throttle height between the speed and the climb graphs of the Spitfire Vb trop. Looking at that gigantic filter, I'm ready to believe that this is perfectly realistic

Regards,

Henning (HoHun)

 

[John Davies]

Henning,

Looking at your excellent graphs a bit more, it seems possible to move towards some fairly definite conclusions.

1)The Seafire LIII enjoyed a decisive performance advantage over the Zero, in both speed and rate of climb, provided it stayed within its best fighting height, i.e below about 12,000 feet.

2) FAA tactics for fighting the Zero in a series of alternating climbing and diving turns, (as I've described in previous posts) exploited this intelligently, and worked well, despite the Zero's tighter radius of turn.

3) Without this performance advantage, the tactic would not have worked. If the Zero had been able to out-climb the Seafire in the climb phase of the manoevre, it could have bounced it in the dive phase of the manoevre, and shot it out of the sky. In reality, of course, it was the other way around, and it was almost always the Seafire which shot the Zero down, which is exactly what you would expect from your data.

4) Turning to the Spitfire Vb trop, the picture is very different, and rather dismaying. It is not nearly so clear what the Spitfire Vb trop could do against the Zero. The Zero can out-turn it at any level. Up to about 15,000 feet the Zero can also out-climb it. Above that height the Spitfire's climb advantage is too small to be decisive. So the tactics the Seafire LIII used would not have worked for the Spitfire Vb trop, because the aircraft's characteristics did not allow them. Traditional Spitfire tactics of relying on the aircraft's ability to turn inside most things would not have worked either, because the Zero was the great exception. In fact, the Spitfire Vb trop's only decisive advantage appears to be that it was faster than the Zero at all altitudes. That suggests that ambush tactics might have worked; one fast pass, then get out as fast as possible. Staying around to fight would probably have been a very bad idea. All things considered, I am not at all surprised they had a rough time of it.

5) The story from Closterman is very interesting. Possibly a comparison between the performance of the Seafire LIII and the Spitfire Mk V LF (i.e cropped and clipped) might reveal quite close similarities.

 

[slaterat]

I don't know why the volkes filter on the Spit V was so large. It is much larger than the volkes filter on the Hurricane. The Spit V loses 16 mph in top speed from 370 to 354. The Hurricane II loses 5 mph from 340 to 335.
The loss in climb is greater too, although because of the different superchargers I'm not sure if they can be fairly compared. ie the Hurricanes best climb is its initial climb ,while the spit V is at 14-15,000 ft.

Although the volkes filters are often criticized in many books, the arguement for their installation is that without them , in dusty conditions , the merlins would of worn out very rapidly, leaving the planes with an even greater performance handicap.

Slaterat

 

[parsifal]

Although the volkes filters are often criticized in many books, the arguement for their installation is that without them , in dusty conditions , the merlins would of worn out very rapidly, leaving the planes with an even greater performance handicap.

Slaterat

But the issue is how much less efficient were these filters in comparison to the opposition. I have seen MC202s fitted with a sand filter, for desert operations, with nowhere near the drag and weight penalties that the Vokes filter appear to impose. So, if the italians could produce a more efficient filter, what went wrong for the allies to produce something like this thing?

 

[Parmigiano]

Totally different technology, i.e. the DB601 of the MC202 (and of the Bf109 Trop) had fuel injection, the Merlin had carburettors.
Probably the DB needed a much smaller 'box' at equal air volume.

 

[John Davies]

I think the reason for the Vokes filter was plain bad design. The Supermarine design office must have been incredibly busy during WW2, and was possibly a bit over-stretched. The Spitfire was developed through nineteen marks during WW2. They got up to the Spitfire 21 before the war ended, but numbers XV and XVII were Griffon-engined Seafires. Earlier, Merlin-engined marks of Seafire had their own numbering system outside the Spitfire series. Confusing, isn't it? Now add the development of sub-types within marks, the whole Seafire series, and a good deal more besides. I can't think of another basic airframe that was subjected to such intense and continuous development over such a long period.

Britain was short of everything in WW2; not just materials, but also skilled labour. The Vokes monstrosity looks to me as if it was designed by the junior draftsman on a bad day. Later, (by 1944) it was replaced by something much better. The Spitfire Mk VIII mostly served overseas, and most (or perhaps all, I'm not sure) were fitted with a neat little "Aero-Vee" filter which looked like a slight forward extension of the carburettor air intake, and was such a tidy installation that you had to look twice to see it was there. It was also fitted to all Seafire FIIIs and LIIIIs

Interestingly, the Vokes monstrosity was briefly fitted to some Seafires; and to the worst-performing Seafires at that. (The Mk IIC) The result was an aircraft that could be out-performed by the Wildcat Mk IV. The recipe? Take one Spitfire Mk Vc. Now add a hook, reinforced slinging points, catapult attachment points ("catapult spools"), and longitudinal strengthening so the aircraft does not separate into two pieces as the hook engages. All this adds a bit over 10% extra weight and some drag. Now, if you are serving in the Mediterranean, add the horrible Vokes filter, which according to Brown meant a further performance penalty of up to 25 mph speed and 300 fpm climb. Unsurprisingly, the FAA decided they would rather accept the risk of rapid engine wear.

The Admiralty pretty rapidly concluded that this was not what they needed. Since the majority of over-water interceptions took place at low to medium level, and certainly below 20,000 feet, Supermarine rapidly developed the Seafire LIIC with the Merlin 32, which had a very useful performance at low to medium level. It did quite well against Bf 109s, held its own against the Fw190, and could just about catch the Ju88, which not all Spitfires could. However, it did not have folding wings, which restricted its usefulness.

The LIIC was followed by the FIII, which did have folding wings, and was a capable medium level fighter. It was produced in quite small numbers, (103 in all) as the FAA relied on its Hellcats and Corsairs at medium to high level, where they excelled.

The real successor to the LIIC was the LIII. Like the FIII, it had folding wings. At low level (up to about 12,000 feet), the Seafire LIII was an excellent aircraft.

As far as I know, in this (admittedly specialised) area, the Seafire LIII was unmatched by any other carrier-based fighter of its time, (except possibly another Seafire, the LIIC) and had the edge over a good many land-based fighters too. It might have been designed as a specialised low-level Zero-killer. Both Henning's graphs and the data in Brown make that very clear. It was produced in larger numbers than any other mark of Seafire. (Over 1100).

Also, as we've seen, (thanks for those graphs, again!) the Seafire LIII's characteristics were quite different from the basic Spitfire V. This means that trying to reach conclusions based on treating the two aircraft as alike will be highly misleading. Quite posssibly the Spitfire Mk V LF (cropped and clipped) that the RAF used in Europe had a similar performance to the Seafire LIII. I haven't seen the figures, but they were both specialised low-level variants. But that's not the variant of Spitfire the RAAF had at Darwin.

As for how the FAA Seafire squadrons might have done if they had gone up aginst the Zero before 1944, that's an interesting question. Because of course they would not have had the LIII. It did not reach the squadrons until February 1944.

If they had had the Seafire 1B, which first went to sea in the autumn of 1942, they might have had the same problems as the RAAF had with their Spitfire Mk Vs, because the Seafire 1B was a very similar aircraft. If they had had the Seafire IIC, which was available shortly afterwards, they would probably have done a good deal worse, because this was basically a hooked Spitfire Mk V plus quite a lot of extra naval gubbins, which of course reduced its performance. (The 1B had been a very basic conversion, which did not receive the full kit of naval bits and pieces) But if they had had the Seafire LIIC, which was at sea from May 1943, the Zeroes would have had quite an ugly shock, because this was the fastest-climbing mark of Merlin Seafire of them all, at least at low to medium level. It was even better in the climb than the LIII, reaching 4,600 fpm at full combat boost at 6,000 feet, an extraordinary figure. And as we have seen, the FAA's successful tactics against the Zero exploited the LIII's high rate of climb to the full, so with the LIIC they might have worked even better.