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.