Spitfire Combat Radius (range) evolution, limitations?

[Geoffrey Sinclair]

Ya'll have to excuse my ignorance here but, I'm using G Geoffrey Sinclair post, but have seen reference elsewhere re:
"while the 66 gallon tanks for "rear view" fuselages "they must not be used in any circumstances"."

I would start with the probability the pilot's notes are a post war edition, with increased safety margins, rather like the way post war Mosquitoes never flew at the weights routinely used in wartime. The P-47 and P-51 needed extra tail area to compensate for the cutting down of the fuselage, so it is logical the Spitfire would as well, but that modification did not happen to the mark IX and XVI. Leading to post war the old style fuselages were considered safe enough to use the rear fuselage tanks if the mission was considered worth it, the cut down fuselages were not.

Fuel management, the notes say take off was using the main tank, then at 2,000 feet
a) no drop tank but rear tanks filled, switch to the rear fuselage tanks until empty.
b) drop tank, no rear tanks, switch to the drop tank until empty
c) drop and rear fuselage tanks filled, change to rear tanks until only 30 gallons left in them, then switch to drop tank until empty then back to rear tanks.

 

[Milosh]

The P-47 and P-51 needed extra tail area to compensate for the cutting down of the fuselage, so it is logical the Spitfire would as well, but that modification did not happen to the mark IX and XVI.

Spitfires got larger rudders on those MKs.

 

[GregP]

With 42G in the rear tank, 96G in the main tank and 26G in the leading edge tanks, should get him home shouldn't it?

I was talking about Spitfire fighters, not about PR Spitfires taking pictures. PR aircraft didn't win the skirmish, the battle, or the war. They took useful pictures that helped other people win the war. A bomber escort of PR Spitfires would be mostly useless. Yes, SOME PR Spitfires retained some guns, but they weren't exactly optimized for fighter duty and weren't used for it.

Out of 20,367 Spitfires built, the PR variety accounted for a whopping 241 or 1.2%. So they weren't exactly plentiful.

You can do the math as well as I can, I'm sure.

Cheers.

 

[Shortround6]

c) drop and rear fuselage tanks filled, change to rear tanks until only 30 gallons left in them, then switch to drop tank until empty then back to rear tanks.

So basically the pair of rear tanks was a codge (get around) of not having an appropriate sized drop tank?
The 170 gal was too big and the 90 gal tank too small to reach the "drop point" without using more internal fuel than wanted?

A bit like the Mustang not really having 269 gal (US) of use to use from internal tanks (and taking out the warm up-takeoff)

So the Spitfire really was using about 30-40imp gallons plus the 90 imp gallon drop tank on the way out and the 30-35imp gallons plus forward fuselage tank/s plus wing tanks for combat and the trip back. ?

 

[Geoffrey Sinclair]

I was talking about Spitfire fighters, not about PR Spitfires taking pictures. PR aircraft didn't win the skirmish, the battle, or the war. They took useful pictures that helped other people win the war. A bomber escort of PR Spitfires would be mostly useless. Yes, SOME PR Spitfires retained some guns, but they weren't exactly optimized for fighter duty and weren't used for it.

Out of 20,367 Spitfires built, variety accounted for a whopping 241 or 1.2%. So they weren't exactly plentiful.

The total Spitfires from the British production reports is 20,349 including the following PR types, 32 III, 229 IV, 16 X (with guns), 471 XI, 200 XIX, total 973 PR types, 4.8% of production. Then there were the conversions.

So basically the pair of rear tanks was a codge (get around) of not having an appropriate sized drop tank?

No, the pair was to minimise the problems when fuel shifted in the tank as the Spitfire flew. Like the P-51 the rear fuel caused stability problems, so again like the P-51 some of the capacity was used before switching to the drop tanks.

The 170 gal was too big and the 90 gal tank too small to reach the "drop point" without using more internal fuel than wanted?

How does drop tank capacity affect internal fuel usage? For most of the fuel tank arrangements on the IX the 90 gallon tank was too big. The RAF did not see the point of a 170 gallon combat tank, given internal fuel loads of 124 gallons in the VIII and 85 in the IX and from all accounts the tank had a lot of drag. So the biggest combat tank was the 90 gallon one. Add 75 gallons of rear fuselage fuel to the IX but drop that to 30 gallons on the way out leaves 85+30 = 115 gallons, less 55 gallons or so combat and reserves, leaves 60 gallons which becomes the range limit, by burning 40 or so gallons of internal fuel outbound you would be turning back with a still partly filled 90 gallon external tank, even after the deductions for warm up and climb. To take full advantage of the 90 gallon tank capacity the 36 gallons of wing tanks would need to be added, joining the rear fuselage tanks. Or else you can go the other way, reduce the external fuel so the tank is empty around maximum radius, in a hand waving approximation, the 45 gallons internal used outbound means the external fuel load drops to 45 or so gallons from 90.

So the Spitfire really was using about 30-40imp gallons plus the 90 imp gallon drop tank on the way out and the 30-35imp gallons plus forward fuselage tank/s plus wing tanks for combat and the trip back. ?

If the rear tanks were fitted then yes, burn off around half of more of the fuel from the rear tanks, then switch to the drop tank, then drop the tank if entering combat, and unless there was enough internal tankage, use a smaller external tank or even a partially filled 90 gallon one.

Spitfires got larger rudders on those MKs.

(VIII and IX) Yes, but that already had them before the cut down fuselages versions were built. Using the pilot's notes the broad chord rudder was judged to be not enough for the cut down fuselage aircraft to safely use the rear fuselage fuel tanks, probably in peace time anyway.

 

[GregP]

My production numbers for PR types don' match yours, Geoffrey, but the point is still that there weren't very many and they weren't all that useful for fighter vs. fighter combat.

So, any missions of the type contemplated above would be in Spitfires that did NOT have leading edge tanks. Therefore, that fuel will not be there in a Spitfire on a combat mission.

And that was the point. Finding a few airframes with extra fuel doesn't make your mission really practical, even on paper, in a Spitfire and it also didn't in the real world of WWII aerial games. Spitfires were among the world's BEST at what they did, but they didn't fly ALL mission and really couldn't as a general rule.

Sure, you could cobble together a "Speed Spitfire," but you were not going to cobble together 500 of them and then go destroy Berlin. It wasn't exactly realistic approach to the end of the war.

 

[Zipper730]

Repeating from "Wasn't the P-51 the best escort fighter of the war?" Page 32, message 623, 6 February. As of January 1944 external tanks for Spitfires being made were 30 gallon (Metal, wood, fibre) and 45, 90 and 170 gallon metal. "relevant Spitfire VIII figures from the original sources quoting maximum weak-mixture power setting as 320 mph at 20,000 ft, consuming about 1.1 gallon per minute. This corresponds with an engine setting of 2,400 rpm, +4 lbs boost (66 gallons per hour). So this seems similar. From the same source, the RAF were allocating 23 gallons for take-off and climb to 20,000 ft, and 36 gallons for 15 minutes of combat, leaving 63 gallons for cruise. This gives an endurance of 57 minutes, or a range of 304 miles, for an escort radius of 152 miles." (no reserves)

What cruise speed was needed for escort missions? Typically the P-51's flew around 300-305 mph and it's turning radius was wider than the Spitfire (a function of having a higher stall speed)...

I remember the USAAF had modified a Spitfire IXc, is this the internal fuel figures they are talking about, or was that another arrangement?

The third edition of the Spitfire mark IX, XI and XVI pilot's notes has the pair of rear fuselage tanks with 75 gallons (66 for "rear view" fuselages), permission from the Area Commander is needed to fill the 75 gallon tanks for special operations, while the 66 gallon tanks for "rear view" fuselages "they must not be used in any circumstances". One reason for a pair of rear fuselage tanks was to reduce fuel movement, my understanding for the 66 gallon option = 2x33 is it was safe to enter combat after one tank was emptied but the improved elevators designed by Westland were needed to carry the rear fuselage fuel.

What's a "rear view" fuselage? Is that a design with a Malcolm hood?

I assume the "rear-view" fuselage designs didn't have the redesigned elevator?

Off the shelf in 1943 is mark VIII with 90 gallon drop tank, 23 gallons lost to warm up and climb, leaving 67 external, add the distance covered in the climb puts the Spitfire around 300 miles from base when the tank is emptied so a radius of around 300 miles.

The more fuel you stuff in the plane, you'll take longer to climb, so that will have to be factored in.

I would also assume that if you were going to use the aft-tanks you'd want to burn those down first to cover at least part of the climb to adjust the CG to within tolerable limits for combat; then switch to drop-tanks for the rest of the climb and flight until combat starts.

BTW: I remember some of the early PR variants had a tank under the pilot that was added: I don't know why that was removed from later aircraft, if there was a good reason.

Official doctrine was not allowing. Charles Portal's opinon (he was the Marshal of the Royal Air Force back then) was that escort fighters don't work.

Ironically, night-fighters were often used to cover bomber-formations.

 

[GregP]

What cruise speed was needed for escort missions? Typically the P-51's flew around 300-305 mph and it's turning radius was wider than the Spitfire (a function of having a higher stall speed)...
The Mareng bag was in lieu of the normal wing-tanks, so it would add 8 gallons versus 36 gallons for a grand total (internal) of 150 gallons for the Mk.VIII and 158 gallons for the Mk.IX.

I remember the USAAF had modified a Spitfire IXc, is this the internal fuel figures they are talking about, or was that another arrangement?
What's a "rear view" fuselage? Is that a design with a Malcolm hood?

I assume the "rear-view" fuselage designs didn't have the redesigned elevator?
The more fuel you stuff in the plane, you'll take longer to climb, so that will have to be factored in.

I would also assume that if you were going to use the aft-tanks you'd want to burn those down first to cover at least part of the climb to adjust the CG to within tolerable limits for combat; then switch to drop-tanks for the rest of the climb and flight until combat starts.

BTW: I remember some of the early PR variants had a tank under the pilot that was added: I don't know why that was removed from later aircraft, if there was a good reason.


Ironically, night-fighters were often used to cover bomber-formations.

The 1-g stall speed doesn't have a lot to do with turning radius. A Spitfire in a level turn at 200 knots (or any OTHER speed) pulling 3-g has exactly the same turn radius as any OTHER airplane at 200 knots pulling 3-g. A lower stall speed simply means that the Spitfire can get just a bit slower before stalling. The thing is, NOBODY who flew a fighter wanted to be in aerial combat anywhere NEAR the 1-g stall speed. What they wanted in a fight was to be near the stall speed for your current g-load, so their turn rate was at its best. It's all in the maneuvering envelope.

All these folks wanting to stuff more fuel into Spitfire are thinking like WWII mission planners. But in the war, they had real Spitfires to plan with, so the long-range missions went to the airplanes that could handle long-range missions. Except for a few times after some fuel managed to get stuffed in (rather late in the war), those missions just didn't involve Spitfires. Spits were reserved for what they did best, be a dogfighter.

Long range was generally the purview of the P-38 with drop tanks, the P-47 with two P-38 drop tanks (PTO, 368th FG), and the P-51 Mustang we all know about. Spitfires were tasked with short to medium-range defense and fighter attack / patrol, usually attacking enemy fighters and bombers, but sometimes getting other tasking. The PR units flew high, fast, and took great pics, but weren't used much on fighter sweeps. No use in risking them when dedicated fighter Spits were available. Also, the PR birds were mostly all assigned to PR units, not fighter units.

 

[wuzak]

What's a "rear view" fuselage? Is that a design with a Malcolm hood?

It's a bubble canopy with cut down rear fuselage.

 

[Zipper730]

The 1-g stall speed doesn't have a lot to do with turning radius. A Spitfire in a level turn at 200 knots (or any OTEHER speed) pulling 3-g has exactly the same turn radius as any OTHER airplane at 200 knots pulling 3-g. A lower stall speed simply means that the Spitfire can get just a bit slower before stalling.

Generally an airplane's corner velocity is the square root of the g-load x stall speed. The stall speed of the Spitfire was lower than the P-51 so it would be able to pull its rated g-load down to lower speeds than the P-51 would.

The P-51 also had a higher g-load so even if they were the same, the P-51 would technically be higher.

The thing is, NOBODY who flew a fighter wanted to be in aerial combat anywhere NEAR the 1-g stall speed. What they wanted in a fight was to be near the stall speed for your current g-load, so their turn rate was at its best.

And the tightest turn rate happened to be where the rated load-factor hit the minimum speed to do it at. The turn rate would tighten down to that point; then widen out below that since you don't have enough speed to produce the lift to pull the load-factor needed.

 

[PAT303]

I was talking about Spitfire fighters, not about PR Spitfires taking pictures. PR aircraft didn't win the skirmish, the battle, or the war. They took useful pictures that helped other people win the war. A bomber escort of PR Spitfires would be mostly useless. Yes, SOME PR Spitfires retained some guns, but they weren't exactly optimized for fighter duty and weren't used for it.

I'm not talking about PR Spitfires

 

[PAT303]

Why does the Spitfire have to do the Mustangs role?. Spits could have been ranging out to 400 miles over the Med, Europe the Pacific contributing far more than what they did if the RAF had the same thinking as the USAF who where at that time fitting ferry tanks to P47's to at least try and get into the fight. Spitfire VIII's and IX's flying escort to the German border from early '43 would have achieved far more than the pointless sweeps they did actually do over the channel because the RAF refused to fit aux tanks.

 

[PAT303]

drop and rear fuselage tanks filled, change to rear tanks until only 30 gallons left in them, then switch to drop tank until empty then back to rear tanks.

Same as the 'stang, it was forbidden for pilots to do any maneuvers with drop tanks fitted or with more than 30-40G of fuel still in the rear tanks, the only exception was the MkXIV, it could fight with the 90G combat tank fitted.

 

[GregP]

Generally an airplane's corner velocity is the square root of the g-load x stall speed. The stall speed of the Spitfire was lower than the P-51 so it would be able to pull its rated g-load down to lower speeds than the P-51 would.

The P-51 also had a higher g-load so even if they were the same, the P-51 would technically be higher.
And the tightest turn rate happened to be where the rated load-factor hit the minimum speed to do it at. The turn rate would tighten down to that point; then widen out below that since you don't have enough speed to produce the lift to pull the load-factor needed.

I agree about the corner velocity, which was not a thing in WWII.

But, you didn't SAY corner velocity. You said turning radius, which has nothing to do with the corner velocity. The turning radius is only related to the velocity squared and the g-fore / bank angle. Recall the level turn g-force is 1/ cos (bank angle). I don't care if you are in a Spitfire, a Bf 109, or a Boei8ng 727, if you are at 300 mph and pulling 3-gs, the turning radius is 2,127 feet. Minimum turn radius will intersect the stall speed, for sure. But nobody in WWII or any other war was trying to engage in aerial combat as slowly as possible. If they get that slow, they are in some trouble and are likely losing the fight or at LEAST are very afraid. There isn't a lot of excess power in a WWII fighter for sustained hard turning. They were in fights that ended rather quickly and, if they WERE turning hard, the fight was descending all the time.

R = V^2 / g * tan (bank angle).

So, which one are you interested in, Zipper, corner velocity which was not once used in WWII or turning radius? Or maybe some other variable? Had you led off with corner velocity, I would have agreed, though it was NOT a number used in WWII. That came after jets, with their higher speeds, made finding the minimum turning radius in a fight a thing to be investigated. The corner velocity of an F-16 is about 450 knots, but it has an afterburner to keep the energy up to that speed. No WWII fighter will sustain much of a turn at 450 knots. Not enough power to stay level in much of a turn at that speed.

It's all good. Cheers.

Hi Pat303.

I didn't suggest the Spitfire perform the Mustang's role, IIRC, it was suggested that the Spitfire would have been a decent long-range fighter. The Mustang WAS a long-range fighter and the Spitfire wasn't, though it got better near the end of the war. It was a superb dogfighter, just not very good at doing it a long way from home.

 

[GregP]

Why does the Spitfire have to do the Mustangs role?. Spits could have been ranging out to 400 miles over the Med, Europe the Pacific contributing far more than what they did if the RAF had the same thinking as the USAF who where at that time fitting ferry tanks to P47's to at least try and get into the fight. Spitfire VIII's and IX's flying escort to the German border from early '43 would have achieved far more than the pointless sweeps they did actually do over the channel because the RAF refused to fit aux tanks.

Yes, perhaps. The thing is, they weren't doing that.

 

[Zipper730]

I agree about the corner velocity, which was not a thing in WWII.

There were charts that talked about turning radius vs g-load which effectively produce the same concept, even if the term wasn't used. Airplanes generally flew at a speed that was tactically usable.

For escort that might be slower than for interception, where the goal is to get out there and destroy the bomber before he can drop bombs on target (which very well might be a city). For escort, the idea would be to be going fast enough that, if jumped by fighters, you were either going fast enough that, in the event of combat, you could either start maneuvering right away, or get up to an optimum speed quickly enough to do you good.

I'm not sure if the 320 mph speed cited for the spitfire was based on escort, general fighter sweeps, or intercept. I do recall that the P-51 usually flew a little slower on escorts, and it seemed to give a good account of itself. I'm not sure how the acceleration rate of the P-51 compared with the Spitfire at 300 or 320 mph (level flight), but I remember hearing it'd dive faster.

The corner velocity of an F-16 is about 450 knots

I didn't know the F-16's was that high to be honest. I believe you however, since I know little about the capabilities of the F-16, but I'm surprised the number was so high.

 

[BiffF15]

There were charts that talked about turning radius vs g-load which effectively produce the same concept, even if the term wasn't used. Airplanes generally flew at a speed that was tactically usable.

For escort that might be slower than for interception, where the goal is to get out there and destroy the bomber before he can drop bombs on target (which very well might be a city). For escort, the idea would be to be going fast enough that, if jumped by fighters, you were either going fast enough that, in the event of combat, you could either start maneuvering right away, or get up to an optimum speed quickly enough to do you good.

I'm not sure if the 320 mph speed cited for the spitfire was based on escort, general fighter sweeps, or intercept. I do recall that the P-51 usually flew a little slower on escorts, and it seemed to give a good account of itself. I'm not sure how the acceleration rate of the P-51 compared with the Spitfire at 300 or 320 mph (level flight), but I remember hearing it'd dive faster.
I didn't know the F-16's was that high to be honest. I believe you however, since I know little about the capabilities of the F-16, but I'm surprised the number was so high.

Zipper / Greg,

The number isn't far off, but it's not a hard window due to its FBW. It's more of a band and, "that's all I'm going to say about that."

Cheers,
Biff

 

[GregP]

Below is a v-n diagram.

The so-called "corner velocity" is located where the 1-g stall speed meets the positive limit load, right where it shows "maneuvering speed" or "corner speed" above. Each v-n diagram is different for different altitudes and weights. The 1-g stall speed changes with weight: Vs new = Vs known * square root (New Weight / Known Weight). It changes with g-load as the square root of the g-load, that is: Vx new = Vs known * square root (g-load). You can calculate the max g-load at any airspeed as: n = (airspeed / stall speed)^2. If your 1-g stall speed is 95 mph and you want to pull 8g's, then the airplane will stall at 268.7 mph, or 95 * sqrt(8).

While this is all known and is built into FBW systems today, it was NOT in WWII and they didn't train WWII fighter pilots in "energy maneuvering'. WWII fighter pilots were not performing high yo-yo and low yo-yo maneuvers, unless it was by accident. They trained by flying against combat veterans who had a decent grasp of what a WWII fighter would do, but didn't exactly understand the v-n diagram above.

The turning radius question is answered by the positive load limit line, and the radius is as I described above. R = (V^2) / (g tan (bank angle)). The minimum radius is where the load limit is reached right at stall speed. Most WWII fighter pilots didn't want the minimum turn radius and didn't even know how to find it. They just wanted to beat the guy behind them right now without stalling. So, they'd pull until the airplane gave a stall warning or got to the g-limit (usually +8) and then back off a bit.

 

[PAT303]

Spitfires got larger rudders on those MKs.

They also got reprofiled ailerons, different bob weights and the aileron hinges were redesigned and moved to give better high speed authority from the MkII through to the MkVIII and IX, testing done on a MkIX showed it was suitable for combat with the bottom 33G tank full.

 

[Geoffrey Sinclair]

Imperial gallons for British types, US gallons for US types. I am sure others can refine the dates, fuel loads and ranges. What would be good to see is an 8th Air Force P-51 fuel load planning document compared to the official fuel consumption performance figures. This is of course all assuming despite every theatre insisting on some Spitfire VIII and/or IX and official doctrine at the time the decision is taken to retain the mark VIII in Britain as then long range escorts, that is assuming the western German fighter defences will be strengthened and be very effective against unescorted heavy bombers, in part by withdrawing fighters from the southern front, making the tasks of the allied Mediterranean units easier, before the events actually happen.

Starting with the imaginary longest range Spitfire fighter version, 96 Gallons in front of the pilot, 36 in the wings, 75 behind the pilot internal. Burn 45 gallons of the rear fuselage fuel outbound. That leaves 96+36+30 = 162 gallons on board entering combat at maximum radius, allowing 35 gallons for combat and 22 gallons for reserves leaves 105 gallons, enough for 509 miles at 320 mph at 20,000 feet, the outbound fuel is 90 gallons external + 45 gallons rear fuselage = 135 gallons, less 23 for warm up and climb leaving 112 gallons. Call it 500 miles radius to allow for 10% more fuel consumption outbound due to the extra drag, assume 320 mph cruise all the way back to base then going vertical to the runway to account for the formation flying fuel penalty of the junior pilots at the rear of the formation.

The 2 points I take from the above is with the historical Spitfire fuel arrangements there is no point in going beyond 90 gallons external and if you were to drop the radius to 400 miles, so around 40 gallons less carried, the weight savings come to around 325 pounds (fuel and smaller self sealing tanks), which is small compared to the overall weights.

The first mark VIII to be fitted with a 75 gallon rear fuselage tank was MT818 (built in June 1944, no date for fuel trials), tests showed 37 gallons needed to be burnt off to make the aircraft properly stable. It would appear the extra weight of the mark VIII forward fuel tanks helped the stability situation.

Meantime the US modified Spitfire IX MK210 to have 43 gallons of fuel in the rear fuselage (more an under cockpit tank), 33 gallons in the wings (2x16.5) in addition to the usual 85 gallons, so 161 gallons internally, plus a pair of 62.5 gallon drop tanks. It was flown from Maine to Newfoundland to Iceland to Britain in July 1944. Weight was 10,150 pounds, still air range 1,600 miles. MK317 was similarly modified and crossed the Atlantic in September 1944. The RAF decided the wings had lost too much strength as a result of the changes. Anyway look at the dates.

The brief I assume is a Spitfire escort fighter for the 8th Air Force from mid 1943 to at the latest May 1944, after that the acute need for longer range high altitude fighters goes, while the RAF then had Mustangs with longer ranges even without a rear fuselage tank, the USAAF had many more fighters and from September the continental airfields are open. The advantage for the Spitfire changes then is any extra weight carrying ability improves the effectiveness at other operations, like fighter bomber.

The P-47 saw plenty of air combat July 1943 to May 1944 so the idea is to keep the Spitfire radius comparable to the P-47, the medium range escort by P-51 standards. The off the shelf Spitfire VIII with a 90 gallon external tank radius was about 300 miles. Add the ahistorical assumption a 33 rear fuselage tank is added sometime later and the radius becomes 380 miles.

Some limitations on 8th Air Force operations. Roger Freeman states the early B-17F, 55,000 pounds, 1,760 gallons of fuel, had a combat radius of 320 miles under 8th Air Force operational conditions, climb high quickly, fly in large, tight formations. To go further meant carrying fuel in the bomb bay. The long range "Tokyo" tanks made that radius 700 miles.

B-17 with extra tanks, first loss, plus the last combat loss of the previous, non Tokyo tank, block.
B-17F-55-BO, production from December 1942, first 8th Air Force loss 7 May 1943, last B-17F-50-BO combat loss 30 January 1944.
B-17F-25-DL, production from January 1943, first 8th Air Force loss 14 May 1943, last B-17F-20-DL combat loss 21 February 1944.
B-17F-30-VE, production from February 1943, first 8th Air Force loss 21 May 1943, last B-17F-25-VE combat loss 22 February 1944.

The 6 September 1943 raids saw 22 B-17 officially lost to lack of fuel, though only 8 were the shorter range variants.

Due to the detachments to the Mediterranean the 8th Air Force flew no B-24 operations late June to early September 1943 while as of end October 1943 the 8th had 16 B-17 and 4 B-24 groups operational, by end December it was 18 and 7. So in mid 1943 the 8th was primarily a short range B-17 force. In addition to the early B-17 range issue in mid 1943 the USAAF was waiting to build the numbers to being able to send 300 sorties on a raid. The self defending bomber required a degree of herd immunity to saturate the defences. For example on 6 March 1944 the 8th lost or wrote off to all causes 81 B-17 and B-24, but that was from 730 sorties, compared to 69 B-17 from 320 sorties on 14 October 1943.

Also remembering 1943 escort tactics were to remain in sight of the bombers, so either the fighters are slowing down to around 240 mph, or they are weaving.

The idea is then as of mid 1943 the RAF puts together 2 wings of Spitfire VIII, rising to 3 or 4 by end of year, for escorting 8th Air Force heavy bombers, each wing the equivalent of an under strength US fighter group. This is quite possible given the historical mark VIII production. These are replaced by Mustangs in the first half of 1944 and/or the USAAF has enough fighters available the RAF can stop doing the missions.

According to Roger Freeman P-47 radius with relevant external fuel, nominal tank capacity / actual capacity
75/84 280 miles. In use August 1943
200/205 275 miles. (part filled) In use July 1943.
108/108 325 miles. In use September 1943.
150/165 375 miles. In use March 1944
2x150/165 550 miles. This arrangement "made handling difficult"
200/215 480 miles. In use November? 1944, project initiated in October, took 34 days to deliver the first tanks.

Number of 8th Air force fighter groups flying combat sorties as of end of month 3 in July 1943, 4 in August, 6 in September, 8 in October, 11 in December. The 9th Air Force had one fighter group operational in December. An extra 3 groups of P-47 equivalents would be useful until end 1943 at least.

My production numbers for PR types don' match yours, Geoffrey, but the point is still that there weren't very many and they weren't all that useful for fighter vs. fighter combat.

While the PR types were not that useful as escorts it would be good to know which web site has the very wrong Spitfire production numbers, managing to report only a quarter of the actual PR versions. Also the figures I posted are not mine, they come from the Vickers company archives, Ministry of Aircraft Production, Ministry of Supply, Air Ministry and RAF and cross checked.

So, any missions of the type contemplated above would be in Spitfires that did NOT have leading edge tanks. Therefore, that fuel will not be there in a Spitfire on a combat mission.

Technically the mark VIII wing tanks were leading edge as far as I know. The 66.5 gallon leading edge tank in the PR versions I understand was not self sealing. The VIII already had 14 gallons in the wing, you would need to go to a pair of 20mm cannons or fit the E wing to free up the outer wing leading edge and the extra wing tanks would start somewhere outboard of the armament, not sure how much volume is there forward of the spar, also the fuel lines have to be threaded through the armament area and while good for CoG purposes, when filled the tanks would not help the roll rate.

Sure, you could cobble together a "Speed Spitfire," but you were not going to cobble together 500 of them and then go destroy Berlin.

No fighter was going to destroy Berlin. Is it possible to redo the radius map with the different cruise speeds and combat allowance?

What cruise speed was needed for escort missions? Typically the P-51's flew around 300-305 mph
What's a "rear view" fuselage? Is that a design with a Malcolm hood?
I assume the "rear-view" fuselage designs didn't have the redesigned elevator?
The more fuel you stuff in the plane, you'll take longer to climb, so that will have to be factored in.
BTW: I remember some of the early PR variants had a tank under the pilot that was added: I don't know why that was removed from later aircraft, if there was a good reason.

Cruise speed is one of those it depends, whether the tactic is to stay with the bomber or to be moving faster for self protection and better ability to intercept. The rear view fuselage was the "bubble" canopy and being a late production type it tended to have the bigger tail/elevator. Agreed the extra fuel weight will add to consumption, particularly on climb. Not sure about an under the pilot tank, but the early PR types had all sorts of camera and fuel combinations.

I'm not sure if the 320 mph speed cited for the spitfire was based on escort, general fighter sweeps, or intercept.

The 320 mph speed was based on Spitfire VIII operations in the Mediterranean. The reason for the 320 mph cruise is speed = safety, it made it much harder to bounce the formation, based on things like the Fw190 evaluation. As well it gave better opportunities to set up an attack. As is well known few normally flew at economic cruise in European contested airspace, while the units in the Pacific knew the chances for combat were minimal except near the target, so economic cruise almost all the way, in a loose association of aircraft that only tightened up near the target.