How superior climb rate is used in air combat ?. (1 Viewer)

[Engineman]

In this case, as i said, I believe both pilots were aces, both aircraft were considered friendly allied types, though I think the Aussies as a Commonwealth nation were hoping the Spitfire would be better - also as the Kittyhawk had known limitations e.g. in particular at altitude and also rate of climb. Not to mention everyone assumed that the Spitfire was better. So I think the report overview in the written paper has a bit of a bias for the Spitfire though it looks like they conducted to test fairly honestly and accurately because they really wanted to know.

As for what qualifies as a 'kill', I don't know if that was really necessary. I think they wanted to get a sense of relative advantages and disadvantages, and to just give the (new to them) Spit V an honest assessment and not just a cakewalk.

As for the period data being unsatisfying, well, I think in history we never get truly definitive answers. It's a journey without a final destination .

As a rough guide, being able to just follow manoeuvres is not enough. This is where WW2 Trials are not conclusive. Guns tracking requires additional performance to pull lead and track. A modern-ish parameter would be a minimum 0.5 sec trigger-pressed steady tracking valid aiming solution on the cockpit of the enemy, given a lethal firepower gun weapon fit.

Eng

 

[Holtzauge]

Thanks for posting those excerpts and documents S Steamed_Banana . They seem very interesting and I will read them through when I get the time.

Regarding the P-40 roll performance, in addition to anecdotal evidence you mentioned, this is also borne out in testing and measurement: Because in the roll speed versus stick forces and flight speed charts I've seen, it looks like the P-40 together with the Fw 190 are in a class of their own.

I happen be be aquainted to the current owner of the P-40N "Little Jeanne" (se attached picture) and he absolutely lauds it when it comes to roll performance. He always likes to point out to me that it can turn tight as well, and according to him better than its reputation. And he has flown a lot of different Warbirds so he knows what he is talking about I think.

Not surprisingly, he also knows others in the P-40 owners community, and he's forwarded the paper I've written in which I compare the P-40E and A6M2 Zero on a theoretical level, theorizing on their weak and strong points and how I believe they could be flown to their advantage from this perspective, and they seem to agree anyway.

But with all of that having been said, I still think individual pilot quotes always need to be taken with a pinch of salt: Clostermann's and Leykauf's claims that the Bf 109 outturned Spitfires are prime examples. Not saying pilot's quotes are useless, because if you do a meta analysis this will undoubtedly give you a reliable result. And taking an example (but with the caveat of not actually having done such a study!) I'm sure such a analysis based on multiple pilot quotes would say that the Spitfire handily out-turned the Bf 109, and you would find Clostermann and Leykauf as outliers in the tails of the normal distribution. But alas, as we know from this forum, Closterman's famous quote still keeps popping up again and again, thus "proving" that the Bf 109 and Fw 190 out-turned the Spitfire.....

So while I find all these tests when different aircraft are flow against each other interesting, I still believe we need more than one to be sure. Just to take an example: In the test you mentioned when a Spitfire was pitted against a P-40, were both pilots of equal skill and did they fly their aircraft to their strengths? Not saying there was an issue here, but we simply don't know do we? We need more corroborating anecdotes to be sure. Not saying numbers are perfect either, since these may also contain errors. However, they do remove much of the subjectivity inherent in anecdotes.

Connected to this, I posted a slide from a video I'm working here in this forum, and based on what Wing Commander Stainforth says here about how he flew the Bf 109, what value can we place in his test report comparing the turn performance of the Spitfire, Hurricane and Bf 109? Unfortunately, I will have to be blunt and say very little.

 

[Steamed_Banana]

As a rough guide, being able to just follow manoeuvres is not enough. This is where WW2 Trials are not conclusive. Guns tracking requires additional performance to pull lead and track. A modern-ish parameter would be a minimum 0.5 sec trigger-pressed steady tracking valid aiming solution on the cockpit of the enemy, given a lethal firepower gun weapon fit.

Eng

I don't think, even if they had laser designators etc., you would ever have a definitive / conclusive answer to that type of question. At best you can get to probabilities in the range of 'somewhat likely' or 'somewhat unlikely'.

 

[Engineman]

I don't think, even if they had laser designators etc., you would ever have a definitive / conclusive answer to that type of question. At best you can get to probabilities in the range of 'somewhat likely' or 'somewhat unlikely'.

No, you easily assess camera-gun film.

Eng

 

[Steamed_Banana]

No, you easily assess camera-gun film.

Eng

Can you now? Where is the big mega stash of it? It seems like I've seen the same two dozen WW2 gun camera clips over and over and over again. I'd love to see the mother lode. I'd also note that a lot of the clips I do see almost invariably seem to mix up Theaters, units, even which side of the war being depicted. Battle of Britain showing Pacific aircraft or Fw 190s etc or B-17s etc. It doesn't inspire confidence!

If you know of this giant mother lode of gun camera footage please link it!

And even when we do have a few seconds of gun camera film, is this really conclusive proof? Does those three feet of cine cam film tell us if anyone else shot the target? It wasn't unusual for a given aircraft to be shot at by multiple fighters, maybe also defensive gunners from bombers or AAA. Either all at once, or before or after. In fact we don't even always know even if the fighter filming / shooting is the one that caused the damage.

Do we always know from 2-6 seconds of cine cam that the aircraft that looks like it's getting wrecked under gunfire even still has a living pilot in it? Planes were apparently shot at after a pilot had bailed out. Do we know if the aircraft was already damaged before it was attacked (by friendly fighters, by AAA, by bomber defensive gunners)? Damaged fighters seem to have been hit on multiple occasions by different enemy systems and sometimes kept flying after a pilot bailed out (or died) continuing to draw attacks.

Does it tell us if the damaged target made it back to base? I think out of those two or three dozen gun camera clips I've seen, maybe a half dozen show convincing destruction - o - target; i.e. wing blown off, stabilizer blown off, pilot bailed out, disintegration... most of them show what looks like some hits on a target, but it's usually not exactly clear if the target was destroyed. It's rare to see gun camera film that follows a target down to the ground (usually only if they are already at more or less sea-level).

Aircraft with quite serious damage: big holes, missing chunks of wing, shattered wind screens, missing control surfaces etc., did often make it back to base. We celebrate it when Allied aircraft pulled this off, but this happened with Axis fighters too, quite often.

Even if you see a fire, fires went out surprisingly often.

In some cases gun camera footage will conclusively tell us that one enemy aircraft was destroyed in one case, but I'm highly dubious that gun camera footage alone would tell us say, which was a better fighter aircraft between two types.

 

[Steamed_Banana]

Thanks for posting those excerpts and documents S Steamed_Banana . They seem very interesting and I will read them through when I get the time.

Regarding the P-40 roll performance, in addition to anecdotal evidence you mentioned, this is also borne out in testing and measurement: Because in the roll speed versus stick forces and flight speed charts I've seen, it looks like the P-40 together with the Fw 190 are in a class of their own.

Clipped wing and / or metal aileron Spits seem to be pretty good too, but yeah

I happen be be aquainted to the current owner of the P-40N "Little Jeanne" (se attached picture) and he absolutely lauds it when it comes to roll performance. He always likes to point out to me that it can turn tight as well, and according to him better than its reputation. And he has flown a lot of different Warbirds so he knows what he is talking about I think.

Again, totally agree. Dozens of wartime pilots pointed this out, but today weirdly nerfed Video Game flight models tell a different story and that has a greater influence (notice where AI pulls data from half the time when you run Google search on WW2 aircraft performance related data.

Not surprisingly, he also knows others in the P-40 owners community, and he's forwarded the paper I've written in which I compare the P-40E and A6M2 Zero on a theoretical level, theorizing on their weak and strong points and how I believe they could be flown to their advantage from this perspective, and they seem to agree anyway.

I have no reason to doubt it.

But with all of that having been said, I still think individual pilot quotes always need to be taken with a pinch of salt: Clostermann's and Leykauf's claims that the Bf 109 outturned Spitfires are prime examples. Not saying pilot's quotes are useless, because if you do a meta analysis this will undoubtedly give you a reliable result. And taking an example (but with the caveat of not actually having done such a study!) I'm sure such a analysis based on multiple pilot quotes would say that the Spitfire handily out-turned the Bf 109, and you would find Clostermann and Leykauf as outliers in the tails of the normal distribution. But alas, as we know from this forum, Closterman's famous quote still keeps popping up again and again, thus "proving" that the Bf 109 and Fw 190 out-turned the Spitfire.....

Yes we can definitely see it. And Clostermann may well be describing something real, like you said an instantaneous turn from a higher E state, riding stalls with the slats etc. who knows, but I totally agree with you that he is an outlier.

So while I find all these tests when different aircraft are flow against each other interesting, I still believe we need more than one to be sure. Just to take an example: In the test you mentioned when a Spitfire was pitted against a P-40, were both pilots of equal skill and did they fly their aircraft to their strengths? Not saying there was an issue here, but we simply don't know do we?

The evidence is that they were, they were both aces and were apparently told to fly as if in a serious fight. However there are some caveats on the aircraft.

We need more corroborating anecdotes to be sure. Not saying numbers are perfect either, since these may also contain errors. However, they do remove much of the subjectivity inherent in anecdotes.

It's definitely just one data point, albeit a very interesting one. The caveat I mentioned is A) the Vokes filter, B) some doubt as to which engine the Spitfire had (maybe Merlin 46) and that the Spitfire was limited to +9 boost which the Aussies were doing with all their 'Capstans' at the time due to trouble running in Theater, either due to the heat or dust or both. So it's quite possible that a Spit Vc vs Kittyhawk fight over an airfield in England or say, Buffalo may have had different outcomes.

Of course we also don't know what manifold pressure the Kitty was running at, that could make a big difference too especially below 10,000 ft

Connected to this, I posted a slide from a video I'm working here in this forum, and based on what Wing Commander Stainforth says here about how he flew the Bf 109, what value can we place in his test report comparing the turn performance of the Spitfire, Hurricane and Bf 109? Unfortunately, I will have to be blunt and say very little.


View attachment 884310

Totally agree with all of your points, anecdotes while valuable data do not conclusively prove anything any more than theoretical gun camera footage (or lack thereof) does. It's just another small part of a very big picture.

And speaking of pictures, that's a gorgeous P-40N, love to see them in period markings. What unit is that meant to be? SW Pacific?

 

[SaparotRob]

As for what qualifies as a 'kill', …

Gun camera footage?

 

[BiffF15]

I'm not that well read up on AVG history, but AFAIK General Chennault's lectures at Toungoo about how to combat Japanese aircraft were held already in August to December 1941. Surely word got around and isn't a bit of a stretch to say they had no idea about how to combat Zero's until 1942 to 1943?



Now why wouldn't they risk this in a P-40E? Again: Over much of the altitude band up to and above 20,000 ft the P-40E would climb with about 400-600 fpm at the Zero's top speed (see my paper here). So all you have to do is keep your altitude and climb, and check that the Zero is not gaining on you, and you will gradually build up an altitude advantage. And aircraft are flown at IAS, and in a high speed climb like this you would be at about 270 mph IAS at these altitudes and I can tell you that there is nothing "mushy" when flying at such IAS. I've flown both the Spitfire and Mustang at these speeds (250-300 mph IAS) and the response is crisp and immediate if you are in this IAS range in a WW2 Warbird.



Interesting, but perhaps not unexpected, since the Spitfire Mk V is a much better aircraft than the Zero. And on top of being an excellent turner, couples that with good speed performance. I don't have the specs for the Vokes Spit Mk V, but I would guess it would be a much more dangerous opponent to the P-40E than the A6M2 Zero.



Absolutely: If you are above and have an energy advantage, you can translate that into instantaneous turn performance, and make life very difficult even for an aircraft that has a better sustained turn capability. I'm sure many Spitfire Mk I pilots were shot down during BoB by Bf 109 E's that came down from above and briefly turned inside them and finished them off with a deflection shot, and then zoomed right back up again.

Your analysis / paper of the P40 versus A6M2 is excellent.

 

[Shortround6]

The high speed climb option (including a gentle high-speed climbing turn) is something I've seen described by P-38 pilots several times,

The climbing turn was also used by some Spitfires.

A high-speed turning climb involves 3 things (or more?) that is not reflected in either just high speed or in climb numbers.
High speed turn is at less than max speed.

at 10-20% less than max speed how much excess power is there to climb with?
One the Spitfire or P-38 or? starts to do a turning climb and accepts the loss in power and lift of the bank it is forcing the opponent to into the same situation. Some planes may be able to match in straight line or at least stay in gun range (firing solution?) long enough but with the target also turning out of the firing arc forcing the pursuer to turn may exceed the pursuer's capability. The Pursuer may not have the power to turn and climb at the same time without losing speed.
The Spitfire and the P-38 may have had this ability for different reasons. The Spitfire had a low wing loading and decent power (talking about 1940 to 1942) while the P-38 had the lowest power to weight ratio of any US fighter (in general, some rare models may cross over).
Now at 20-30% less than max speed how much power do the fighters have to turn with and how much is still left for even a shallow climb?
It sounds like a simple maneuver, but the pilot is dividing his available power three ways. The turn has to shallow enough to not take too much power but enough to keep out of the firing arc of the pursing fighter. The evading fighter has to keep enough speed so that he is not overtaken and he has to gain altitude while doing this in order to build in enough altitude advantage to make the pursuer give up.

 

[Steamed_Banana]

The climbing turn was also used by some Spitfires.

A high-speed turning climb involves 3 things (or more?) that is not reflected in either just high speed or in climb numbers.
High speed turn is at less than max speed.
View attachment 884354
at 10-20% less than max speed how much excess power is there to climb with?
One the Spitfire or P-38 or? starts to do a turning climb and accepts the loss in power and lift of the bank it is forcing the opponent to into the same situation. Some planes may be able to match in straight line or at least stay in gun range (firing solution?) long enough but with the target also turning out of the firing arc forcing the pursuer to turn may exceed the pursuer's capability. The Pursuer may not have the power to turn and climb at the same time without losing speed.
The Spitfire and the P-38 may have had this ability for different reasons. The Spitfire had a low wing loading and decent power (talking about 1940 to 1942) while the P-38 had the lowest power to weight ratio of any US fighter (in general, some rare models may cross over).
Now at 20-30% less than max speed how much power do the fighters have to turn with and how much is still left for even a shallow climb?
It sounds like a simple maneuver, but the pilot is dividing his available power three ways. The turn has to shallow enough to not take too much power but enough to keep out of the firing arc of the pursing fighter. The evading fighter has to keep enough speed so that he is not overtaken and he has to gain altitude while doing this in order to build in enough altitude advantage to make the pursuer give up.

I think a lot of these 'Devices' or gambits people made up to survive air combat were all pretty tricky to do successfully in a real fight - Thach Weave, all the escape maneuvers, scissors, low-yo-yo, Hinero Komi etc. etc. even just basic energy fighting. All take good flying skills, self discipline, excellent situational awareness and timing.

A lot of times it comes down to a few experts - like Bong and McGuire with the P-38, Gabby Gabreski with the P-47, Marseilles with the 109F-4 in North Africa, the various other German experten on the Russian front, Nishizawa, Sakai, Iwamoto, Sugita, Okumura with the A6M, Johnny Johnson and Sailor Malan and Buzz Beurling etc. etc. with the Spitfire, Greg Boyington and Hanson and Walsh and Kepford with the F4U, James Edwards and Clive Caldwell with the Kittyhawk, Kozhedub with the La-5 and Gulaev, Pokryshkin, and Rehkalov with the Kobra, these people really dialed it in. The average pilot didn't necessarily get there so easily.

 

[Engineman]

No, you easily assess camera-gun film.

Eng

Perhaps it is better to say that combat Trials using gun-camera film could have given more accurate assessment results. Unfortunately, most of the trials I have seen are lacking in such details. There is evidence that many pilots were unwilling to operate the WW2 aircraft close to the aircraft limits and this was partly due to limited information the pilot had about how close they were to the stall and the risk of high speed stall/spin.

In the '70's I had the opportunity to view 100's of reels of original RAF operational gun-camera film. The films were mostly multiple short clips showing only the firing burst. Against enemy fighters (Bf 109 and Fw 190) the shooting was mostly fly-through or snap shots, with very few tracked bursts. The films against larger aircraft were mostly longer bursts at relatively long range, but some closing-up. The films had been assessed and the enemy aircraft type was identified with a header before each clip. Very noticeable in several films were fratricide shots on several Spitfires and a P-47. These were still identified on the header as Bf 109!

Eng

 

[Holtzauge]

I think a lot of these 'Devices' or gambits people made up to survive air combat were all pretty tricky to do successfully in a real fight - Thach Weave, all the escape maneuvers, scissors, low-yo-yo, Hinero Komi etc. etc. even just basic energy fighting. All take good flying skills, self discipline, excellent situational awareness and timing.

A lot of times it comes down to a few experts - like Bong and McGuire with the P-38, Gabby Gabreski with the P-47, Marseilles with the 109F-4 in North Africa, the various other German experten on the Russian front, Nishizawa, Sakai, Iwamoto, Sugita, Okumura with the A6M, Johnny Johnson and Sailor Malan and Buzz Beurling etc. etc. with the Spitfire, Greg Boyington and Hanson and Walsh and Kepford with the F4U, James Edwards and Clive Caldwell with the Kittyhawk, Kozhedub with the La-5 and Gulaev, Pokryshkin, and Rehkalov with the Kobra, these people really dialed it in. The average pilot didn't necessarily get there so easily.

I think this is a good point: We hear all these stories about the exploits of the aces. But how representative are these to form a picture of how the average pilots flew?

Outliers when it comes to turn performance were mentioned earlier. But most pilot memoirs are of course written by exceptional people who by definition are outliers. That's why they get published and we read them.

I mentioned the books "The German aces speak" earlier, and while many of them stress that their fellow aces were exceptional in many ways: Good pilots, great leaders, good SA and good shots etc., many of them also actually mention luck: It was not enough to be a hot shot pilot. You needed luck as well to survive.

And the reverse is probably true as well: Probably a lot of exceptionally gifted pilots who did everything right but still succumbed to that one in a million "golden BB" from a high angles deflection shot at an "impossible" range anyway.

 

[PAT303]

Holtzauge This is a summary of the RAAF test I mentioned, and I've also attached a scan of the original document, where the Spitfire V is referred to as "Capstan"

The scan is pretty crappy, but I messed around with the contrast etc. to try to make it easier to read. This isn't the only document though, there is another one which gets into more detail of each of the mock combats. Maybe somebody else has it?

This is a transcription someone posted previously in this forum:

"5. Results:
a) Spitfire had the greater rate of climb at all heights - the difference becoming greater as height increased above 13,000ft.

b) Spitfire is far more manoeuvrable at all heights.

c) Kittyhawk is faster in level speed from 0 to 16,000ft. Above 16,000ft Spitfire is faster and again the difference becomes greater as height increases. Estimated speed advantage of Kittyhawk up to 16,000ft: 0ft - 15mph; 12,000ft - 20 to 25mph; 16,000ft - 5 to 10mph.

d) Kittyhawk accelerates, both in dive and on increase of throttle on the level, far more quickly than the Spitfire.

6) Combat 1 - commenced at 13,000ft (equal height) and lasted for 5 to 7 minutes, in which time the fight was practically a stalemate. At the end of this period height was reduced to 4,000ft when the Kittyhawk pilots decided he had nothing to gain by staying and so broke off by diving away. Thus, in combat up to 16,000ft, the Kittyhawk has the distinct advantage in that the pilot can commence the fight and discontinue it at will. In such a combat the Kittyhawks tactics are to hit and run, and then come again.

7) Combat 2 - commenced at 20,000ft (equal height) and lasted less than 2 minutes. Spitfire quickly gained dominant position on the tail of the Kittyhawk and couldn't be shaken. Kittyhawk pilot broke off by diving away.

8) Combat 3 - Commenced at 16,000ft (height advantage to Kittyhawk) an lasted 14 minutes. Kittyhawk made repeated dive and zoom attacks with the Spitfire alternatively breaking hard to avoid and climbing for advantage where possible. Fight reduced to 9,000ft with neither pilot gaining a decisive advantage.

9) Combat 4 - Commence at 16,000ft (height advantage to Spitfire) and lasted 11 minutes. Spitfire pounced on Kittyhawk and attempted to gain a position on tail. Kittyhawk used speed advantage in first level flight and then shallow dive to gain separation and then climb for advantage. Spitfire countered by climbing hard. Gaining advantage Spitfire used climb and dive tactics to force the Kittyhawk to make repeated diving breaks to avoid. At 7,000ft Kittyhawk used superior roll rate to scissor behind the Spitfire, who countered with steep climb. Kittyhawk then used speed advantage to again gain separation and fight was broken off.

10) Visions - the vision in the Spitfire with the hood closed is better than the Kittyhawk, but it is a definite disadvantage that the hood cannot be opened at speeds above 160mph particularly when searching up-sun.

11) The flying characteristics of the Spitfire make it more suitable for Operations:

a) it is easier to fly.

b) Take-off run is much shorter and so could be operated from smaller landing grounds. Note – the Spitfire does not handle hard dirt strips as well as the Kittyhawk.

c) Mixture and boost are automatically controlled.

d) It is not necessary, as it is in the Kittyhawk, to alter rudder and elevator trims over great speed changes.

All these facts greatly reduce the pilot's problems and so increase his fighting efficiency. The report concluded by recommending that as the large Volkes air filter on the Spitfire cost 20-30mph in top speed, it should be removed in operational service - or at least an alternative found. Also mentioned was the effect of the Spitfires rough paint finish on performance but the general feeling of the report was that the Spitfire was perhaps the better fighter, especially at altitude."

I thought the part about " At 7,000ft Kittyhawk used superior roll rate to scissor behind the Spitfire" was particularly interesting in light of this conversation (and the comparison between Kittyhawk and A6M).

I believe this Kittyhawk pilot however was a very experienced ace, as was the Spitfire pilot. Not all Allied pilots were that clever.

The issue with the Spitfire as its low boost, they were limited to 9PSI at the time of the test when both the Merlin 45 and 46 engines were approved for 16PSI by RR, the MkV struggled to loop against the A6M when they were tested the engine as so sluggish and the top speed of them maxed out at 350mph which is almost 20mph slower than a Mk1.

 

[bada]

Clipped wing and / or metal aileron Spits seem to be pretty good too, but yeah

still got an issue with this sentence.
This seems to be part of the myth surrounding the spitfire.
The Raf following report seems to be constantly ignored when talking about the spit roll rate
see post:

"Johnnie" Johnson-August 19th, 1942 Combat-Dieppe

Well yes and no...the clipped wings weren't the miracle solution and even with clipped wings, the spit was still far off the würger in the roll rate area and was loosing precious turn rate. It isn't until the appearance of the universal wing that clipped wings became more frequent, but at that...

ww2aircraft.net

 

[Steamed_Banana]

The issue with the Spitfire as its low boost, they were limited to 9PSI at the time of the test when both the Merlin 45 and 46 engines were approved for 16PSI by RR, the MkV struggled to loop against the A6M when they were tested the engine as so sluggish and the top speed of them maxed out at 350mph which is almost 20mph slower than a Mk1.

As I already noted, the Australians were imposing an official limit of +9 boost on Spitfires in Theater because they were having so many problems with overheating and engine life in the torrid environment. I believe this was gradually increased (certainly by the time the Spit VIIIs arrived) though I don't have a precise timeline on it.

However, it's also worth noting that at the time of the test, officially the Kittyhawk Ia / P-40E was also limited to military power at 42"-44" Hg boost, (which I think is like +8 lb boost?) (which is incidentally the power used in most or all of the British Kittyhawk testing recorded at Boscombe down), whereas by 1943 onward this increased in the manuals to allow up to 57" Hg (+16 lb) for WEP for P-40E, and 60" for P-40K.

We don't actually know what limits either aircraft were being flown at in the test, though we do know that Australian Kittyhawk units increased boost against orders by that time (per the famous Allison memo on overboosting) as early as mid-1942.

 

[Steamed_Banana]

still got an issue with this sentence.
This seems to be part of the myth surrounding the spitfire.
The Raf following report seems to be constantly ignored when talking about the spit roll rate
see post:

"Johnnie" Johnson-August 19th, 1942 Combat-Dieppe

Well yes and no...the clipped wings weren't the miracle solution and even with clipped wings, the spit was still far off the würger in the roll rate area and was loosing precious turn rate. It isn't until the appearance of the universal wing that clipped wings became more frequent, but at that...

ww2aircraft.net

Oh yeah, this keeps coming up.

There is an ongoing debate as to what caused the vast improvement in roll-rate, either the clipped wings or the metal ailerons, or some combination of both. There seems to have been considerable range of quality in the Spit Vs that were being produced by various factories, and specifically with the fabric covered ailerons, some appearing to be very 'loose' and some 'tight', and possibly some rigged differently. The memo you are referring to notes that one of the aircraft (N.221) had 'bad' ailerons, which clearly affected the test:

and nevertheless the pilot seemed to note that clipping the wings did improve roll rate on the second aircraft.

I don't know if the difference was the 'clipped' wings or the ailerons or both, (which is why I wrote "Clipped wing and / or metal aileron" in the post you replied to) but something clearly improved later production Spit Vs and subsequent Merlin marks, which did get the metal ailerons, and it's notable that clipping the wings became common practice at least from what I understand.

The famous NACA 868 chart shows two different roll rates for the Spitfire as you can see, both peaking at about 200 mph and falling off fairly sharply after that, but early Spit V (indicated as 'normal wing' on the chart, correctly or otherwise) peaked at about 105 degrees per second (quite good), fell to about 85 by 280 mph (average), and dropped to 45 by 380 mph (poor), indicating a relatively low roll rate in a dive. The later Spitfire (indicated as 'clipped wing' on the chart, probably later Mk V with clipped wings and metal ailerons) peaks at a superb 150 degrees per second, drops to a still superb 130 at 280 mph, and is still a respectable 85 at 380 mph. That's a huge difference.


It's notable that aside from the rather epic roll rate of the Fw 190, the next best are the P-40F and the P-51B. Other tests of P-40s show higher roll rate than indicated here, while early P-51 (P-51A, NA 73 etc.) had a quite sluggish roll rate. The difference for the P-51 seems to be related to how the ailerons were rigged and mounted. Spitfire roll rates improved dramatically between 1940-43, and P-40 roll rates also seem to have improved in most tests. Later model P-40s had lengthened tails which improved handling, I don't know if any changes were made to ailerons or aileron rigging.

In this early (1941 I believe) test, P-36 peaks at 90 degrees roll at about 180 mph, (probably early Hawk 81 / Tomahawk type) P-40 peaks at 110 at 290 mph, while (probably Mk I) Hurricane and (early Mk I or II) Spitfire peak similarly at around 60 degrees.

On this 1944 test for example, (late model) Spit V peaks at 150 degrees per second at 200 mph, drops to 115 at 300 mph, and hits 70 at 400 mph, while the (late model) P-40 peaks at 135 degrees per second at 360 mph, then drops rapidly to 80 by 450 mph (which is close to it's dive speed limit). The P-51B peaks at 95 degrees per second at 300 mph and drops off more slowly. Fw 190 peaks at 160 degrees per second at 260 mph, drops to a still quite brisk 105 degrees at 350 mph, and drops to 65 at 450.

Worth pointing out that in this test that the (certainly clipped and / or metal aileron) Spit V can out roll the Fw 190 at low speed, while only the P-40 can out-roll it above ~320 mph, i.e. in a dive of any significance, something which was noted by some USAAF P-40 pilots flying over Sardinia, Sicily, and Italy in 1943-44.

 

[Steamed_Banana]

Perhaps it is better to say that combat Trials using gun-camera film could have given more accurate assessment results. Unfortunately, most of the trials I have seen are lacking in such details. There is evidence that many pilots were unwilling to operate the WW2 aircraft close to the aircraft limits and this was partly due to limited information the pilot had about how close they were to the stall and the risk of high speed stall/spin.

Again, this test was in late (Dec) 1942 with two very experienced pilots, apparently, who had survived combat against the enemy. So while what you have noted was generally true, there isn't any reason to assume it's the case here.

In the '70's I had the opportunity to view 100's of reels of original RAF operational gun-camera film. The films were mostly multiple short clips showing only the firing burst. Against enemy fighters (Bf 109 and Fw 190) the shooting was mostly fly-through or snap shots, with very few tracked bursts. The films against larger aircraft were mostly longer bursts at relatively long range, but some closing-up. The films had been assessed and the enemy aircraft type was identified with a header before each clip. Very noticeable in several films were fratricide shots on several Spitfires and a P-47. These were still identified on the header as Bf 109!

Eng

I wonder why these clips aren't online yet, it seems like they'd be a hit. I'd love to see more of them personally.

but yeah this "short clips showing only the firing burst" is part of the problem with gun camera footage as a data point. The aircraft only carry so much film (which is heavy and takes up space, since we are in the pre-digital era), and the cameras are (usually? always?) only on while the guns are actually firing, so you don't get to see a lot of precursor or followup. It's really hard to know what the effect was in many if not most cases.

 

[Steamed_Banana]

A couple of other points on roll rate:

• Roll varied not just by stick force and speed, but also by altitude. Some aircraft like the P-47 seem to have rolled better at higher altitude. I don't know the full breakdown of this for aircraft in general, maybe someone who knows the physics / aerodynamics / engineering very well (I know y'all are in here) can chime in.
• Weight in the wings could affect roll rate, which is one of the reasons why Soviet designed fighters rarely had wing guns.
• The Soviets often (not always) removed one or more pairs of wing guns from many Lend Lease aircraft including Hawker Hurricane, Spitfire, P-39, and P-40s. Many Tomahawk type P-40s had all wing guns removed, leaving only the two 12.7mm machine guns in the nose.
• Italian units often removed the 7.7mm wing guns from MC. 202 fighters, leaving only the two 12.7mm machine guns in the nose. In part this was to improve roll rate.
• Some RAF and USAAF units fighting in the early days in the Pacific War (Burma / Malaya / Java / Philippines) removed some wing guns from their Buffalo, Hurricane, and P-40 fighters.
• USAAF units in North Africa so routinely removed a pair of wing guns from their P-40Fs that the next model, P-40L, came with four guns instead of six (though two more could easily be put back in by field mechanics, and they often did when doing mostly strafing / fighter bomber missions). The early P-40N also had four guns.
• The (four gun) P-51B/C apparently had a bit better roll rate than the (six gun) P-51D.
• The two-cannon Fw 190A-5, which had the outer pair of wing cannon removed to help carry the weight of bombs, apparently had a better roll rate than the (four cannon) A4 and A8 etc. variants. Though the A-5 was designed as a fighter-bomber type some very high scoring pilots (Otto Kittel - 267 victories, Josef Wurmheller -102 victories, notably in the West, Hermann Graf 212 victories) preferred the A-5 due to in part to slightly better handling and roll rate.
• Apparently one whole gruppe, JG 54, stuck with Fw 190 A-5 when the A-8 came out because they preferred the agility of the A-5.
• The HF (high altitude) Spitfire variants with extended wingtips apparently had significantly inferior roll rate, to the point that they were often disliked by pilots (though this wasn't the only reason)
• The Japanese clipped the wings of the A6M "Zero" fighter, which went from 39' 4" / 12m in the A6M2, to a 36' 1" / 11m on the A6M3 and A6M5. This was in part to improve rate of roll, as well as to improve acceleration and dive speed.
• Generally speaking, later war fighters tended to improve in rate of roll, while remaining the same or sometimes declining in rate of turn.

 

[Engineman]

Again, this test was in late (Dec) 1942 with two very experienced pilots, apparently, who had survived combat against the enemy. So while what you have noted was generally true, there isn't any reason to assume it's the case here.



I wonder why these clips aren't online yet, it seems like they'd be a hit. I'd love to see more of them personally.

but yeah this "short clips showing only the firing burst" is part of the problem with gun camera footage as a data point. The aircraft only carry so much film (which is heavy and takes up space, since we are in the pre-digital era), and the cameras are (usually? always?) only on while the guns are actually firing, so you don't get to see a lot of precursor or followup. It's really hard to know what the effect was in many if not most cases.

The film was original negative B/W and was on reels for wartime recce training. I doubt that it was ever released for general viewing and I was not in a position to do that.

The point is that it was possible for combat trials aircraft to film engagements in an accurate way that could have better defined the combat abilities of different aircraft. I would still say that much of the British trials performance data is of mixed value. OTOH, some original manufacturers' aircraft performance data is quite detailed but it is not always the performance used in combat, before the BoB there was little or no mention of the serious Merlin negative-G cut problem, despite all the performance trials. Furthermore, the format and scope of British tactical trials with enemy aircraft was very variable. Precise definitions or the quantifying of combat performance were often loose, how about this British tactical trials quote, "if the "X aircraft" flicked over into a diving turn in the opposite direction the "Y aircraft" had great difficulty in following this manoeuvre". Did it manage to follow , why was it difficult, what was the implication in combat? Who can tell? From my POV, following any other aircraft in combat is difficult! The point of tactical trials briefs is to quantify the difficulties and promote the understanding. What was unsaid in this quote is that aircraft Y could not use aileron rolls to shake aircraft X off his tail!

Eng

 

[Holtzauge]

A minor point: When roll rates are discussed, remember that roll rate is basically not affected by moment of inertia, i.e. if there are guns and ammunition in the wings or not.

The aircraft will still reach basically the same roll rate in the end but it will take longer to get there. This point is often missed in these discussions. And it's important to remember that the end roll rate attained is basically only determined by aerodynamic factors, not by moment of inertia.

However, what is affected is the roll acceleration. This is why for example the P-38 with boosted ailerons may have a very good roll rate at higher speeds. However, the roll acceleration will always suffer due to the horrendous moment of inertia the engines out on the wings cause.

And of course roll rate is important: But what really counts is how fast you can attain a certain bank angle: As an example, a P-38 chasing a Bf 109 jinxing left and right by rolling, will always have a harder time due to roll acceleration than a single engined fighter which as the same roll rate performance.