Like I have already posted, make the tank to the seat profile between members 11 and 12 with a simple pump that feeds to the top tank, done, no COG issue's plus it becomes spaced armor for the pilot once empty.
Spitfire Combat Radius (range) evolution, limitations? (2 Viewers)
- Thread starter IdahoRenegade
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The argument against building fighters that are needed because it causes interruptions in production is lost if the fighters that are needed are delivered after the war has finished, what's even worse was Hawker was still building Hurricanes in 1944.
So did American pilots flying normal run of the mill P51's, later they had to switch between the wing tanks and drop tanks, even later still balance the fuel between the wing tanks, drop tanks and rear tank, the more this thread goes on the more I'm realising just how much better the American pilots were, they just got on with it.
drgondog
Major
The nominal CG is at the front wing spar location, slightly aft of the wing 1/4 chord location. The seat and pilot is aft of the CG. Any weight aft of the main spar will contribute to aft CG. That The reason that more fuel other than the auxiliary 100-gal tank in the P-47 could not be increased - is because it was already the cause of a CG problem on take-off that was already near the aft limit,
yulzari
Tech Sergeant
To cover the shortfall and delays in Typhoon production. And they were used. Last in operational service in Cyprus in1946.
People that allowed that Hurricanes are made after 1942 should've been sent to some cozy place, like the South Georgia weather station.
There was a war fought in 1943, too, when the Merlin Mustangs were but a footnote wrt. the actual fighting, unlike the Spitfire VIIIs. Actual need for the even longer ranged Mk.VIIIs was there - in the ETO, in the Med, in Asia/Pacific - while availability was not.
Shortround6
Lieutenant General
In an ideal world they would have to wait several years while the people that OKed the mass production of the Typhoon in 1941-42 served their tours of duty.
And they would die of old age while the geniuses in charge of British tank development/production did their tours of duty. 30-50 years each.
Hurricane in 1942 and later was often taking the place of the German Ju-87 in terms of duties.
Shortround6
Lieutenant General
This is true but.
The first production Spitfire F VIII (JF.274) was delivered in November 1942. 126 and 145 Squadrons went operational with Spitfire VIIIs in June 1943 while based on Malta.1 Operation Husky, the invasion of Sicily, commenced on 10 July 1943. On this date there were 23 Spitfire fighter squadrons based on Malta flying a mix of Spitfire Vs, VIIIs and IXs which provided cover for the invasion.
Could the British have built more MK VIIIs and less MK IXs in the first 1/2 of 1943, and if they didn't build as many total in those 6 months what would have been the effect?
1943 was a critical year in the war in many places. Having more capable, but fewer, Spitfires of all types is an interesting question. We don't know what the tradeoff would actually of been. 50 less total or 100 less or 200?
There had been only 4 Squadrons of MK IXs at Dieppe in Aug 1942.
We are going around in circles, the rear tank is burnt off first so why is it such a problem to fly hands on for the first 30 minutes?
I'd rather less better quality planes, why was materials and especially Merlin engines and experienced pilots wasted on the Hurricane?, why couldn't Hawker change over to say Spitfire MkVIII production?, yes there would have been a delay in production but what did Hurricanes achieve after the BoB other than get shot down?, they were next to useless against any Axis fighters after 1942.
Shortround6
Lieutenant General
Hurricanes never got two stage engines as fitted to the Spitfire VII, VIII or IX.
Only conflict is using Merlin 45s in MK Vs instead of the 2 speed engines (MK XX and up) used in the Hurricane.
Lighter, lower drag Spitfires didn't need the low altitude boost as bad as the Hurricane did.
After 1942 nobody really thought of the Hurricane as a fighter (except against the Japanese and everybody knew that the Japanese could not build good aircraft).
After 1942 the Hurricane was replacing Blenheim bombers and Beauforts for tactical missions.
There were not enough Marylanders and Baltimore's. Baltimore's never left the mid-east/Med.
By the time you get to Spitfire MK VIII production Hawker was stuck in Typhoon production problem. And Hawker didn't make engines. Putting Merlin XX's into Spitfire MK VIIIs wasn't going to do anything.
Gloster, another company in the Hawker Siddeley Group and a second source of Hurricane production, saw its production facilities turned over to Typhoon production. They built virtually all the the Typhoons.
Hurricane production at Hawker's main factory at Langley continued until July 1944. But then there was Tempest.
In 1941, the Air Ministry approved development of the Typhoon II, aka the Tempest. But there were development delays with the Sabre IV engine intended for the Mk.I and also with the leading edge radiators. So the first production version became the Mk.V using the same engine as the Typhoon.
Tempest V production began at a slow rate in mid-1943 (prototype flew in Sept 1942) alongside continuing Hurricane production at the main Hawker factory at Langley. They reached the first front line squadrons in spring 1944. But the Tempest programme was running late. Add to that the complexities of contracted numbers and Marks being frequently changed and moved between companies (Hawker Langley, Gloster & Bristol were all involved at different times).
The next Tempest version to see production was the Centaurus engined Mk.II. It too suffered development delays even though development had started with the Hawker Tornado. The first prototype of this version flew in June 1943 and the second in Sept. But again development problems continued with that version. The first production aircraft of this version came off a Bristol Aircraft production line in Oct 1944, with production starting at Langley in early 1945 (March IIRC).
So had Tempest development happened as originally envisaged, Langley would have been able to switch production over from Hurricane to Tempest sooner. Keeping the lines open producing Hurricanes at least kept the workforce together pending that aircraft being ready.
And why would you want to build more Spitfire VIII when the Griffon engined Mk.XIV was ready to enter production from late 1943. If you are retooling a factory, better to build the most modern version. Always assuming of course that engines can be made available for whatever you decide to build.
Hurricane production at Hawker's main factory at Langley continued until July 1944. But then there was Tempest.
In 1941, the Air Ministry approved development of the Typhoon II, aka the Tempest. But there were development delays with the Sabre IV engine intended for the Mk.I and also with the leading edge radiators. So the first production version became the Mk.V using the same engine as the Typhoon.
Tempest V production began at a slow rate in mid-1943 (prototype flew in Sept 1942) alongside continuing Hurricane production at the main Hawker factory at Langley. They reached the first front line squadrons in spring 1944. But the Tempest programme was running late. Add to that the complexities of contracted numbers and Marks being frequently changed and moved between companies (Hawker Langley, Gloster & Bristol were all involved at different times).
The next Tempest version to see production was the Centaurus engined Mk.II. It too suffered development delays even though development had started with the Hawker Tornado. The first prototype of this version flew in June 1943 and the second in Sept. But again development problems continued with that version. The first production aircraft of this version came off a Bristol Aircraft production line in Oct 1944, with production starting at Langley in early 1945 (March IIRC).
So had Tempest development happened as originally envisaged, Langley would have been able to switch production over from Hurricane to Tempest sooner. Keeping the lines open producing Hurricanes at least kept the workforce together pending that aircraft being ready.
And why would you want to build more Spitfire VIII when the Griffon engined Mk.XIV was ready to enter production from late 1943. If you are retooling a factory, better to build the most modern version. Always assuming of course that engines can be made available for whatever you decide to build.
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yulzari
Tech Sergeant
And what else would they have been flying? It should have been Typhoons, that was the plan. But they were not in time or in enough numbers.
They had a shed load of already manufactured parts with the parts makers still finishing their contracts on their production lines. Hawker and Canada had a production one still working and no Typhoon production to make so either they made nothing or the used up the capacity in hand. The decision was made in 1943 and production ended six months later. It was make Hurricanes or make nothing. They should have been making Typhoons or Tempests but they could not at the time. Any lend lease US fighters were already earmarked for squadron service. Some went to upgrade units in Burma, others to squadrons in areas where operational use was unlikely. Otherwise they were used in second line roles releasing more modern types for the front line especially as high speed fighter trainers in OTUs where that were a valuable stepping stone from Masters and Harvards towards actual modern operational fighters. The last NW Europe somewhat operational use was by the Polish Air Force No309 squadron in Scotland who used Hurricanes for a very short while when their reconnaissance Mustangs had Merlin engine issues but they went back to Mustangs before moving to the NW Europe campaign. In Burma the RAF ceased using Hurricanes six months before the war ended there with the last squadron going over to the Thunderbolt. The Royal Indian Air Force made good use of their Hurricanes right up to the end of the war when they were transitioning to Spitfires.
Continuing minor Hurricane production into mid 1944 was not a desireable choice but it was a necessary one.
Why make the Hurricane or Merlin XX after 1941, the RAF were better of buying P40's, if they prioritized Spitfire production they wouldn't have needed the intrim models, have Hawker fit Merlin 45's into MkII's and 60 series in MkV and leave Supermarine to make MkVIII's and XIV's.
drgondog
Major
Because sometimes the condition is uncontrollable.
Aft cg could cause an uncontrollable pitch up/stall on take-off for example. Most consider that a 'bad thing'. When a (unspecified qty) tank was placed aft of seat in P-47 it was stated as 'nearly uncontrollable' and constantly on verge of departure - and these were skilled test pilots. I'm sorry, but I can't put my hands on the actual test report. FWIIW, the pilot manual for the P-47 states that the pilot should reduce the 100-gal auxiliary tank from 100 to 20+gallons.
So the POINT is that a severe flight condition occured instantly as lift is generated and flight achieved, so unless you plan on burning off the tank during warm up and taxi you proceed no further on a repetitive basis.
There was rather more operational use of Hurricanes into 1945 than might be imagined.
In the Mediterranean Hurricane IV were used operationally as part of the Balkan Air Force over Yugoslavia right to the end of the European war by 6 and 351 squadrons. 6 squadron didn't finally begin to trade Hurricanes for Tempest VI until late 1946 when in Cyprus. 351 (Yugoslav) squadron operated alongside them until it disbanded in June 1945.
In the Far East Hurricanes were used operationally right to the end of the WW2 campaigns in Burma.
11 squadron was withdrawn from Burma in May 1945 and traded its Hurricane IIc for Spitfire FR.XIV which it flew into Malaya from an escort carrier in Sept as part of Operation Zipper.
20 squadron was withdrawn from Burma to India in mid-May 1945 following the arrival of the monsoon. There it received Spitfire VIII in Sept 1945 which it took to Thailand.
28 squadron, in the tactical recce role, reached Mingaladon outside Rangoon in late May 1945. It received 3 Spitfire XI in late July (first operational use on 11th Aug) to operate alongside its remaining Hurricanes. At the end of July 1945 it only had 6 serviceable Hurricanes on hand, but was told to expect 12 Hurricane IV as soon as the aircraft had been fitted with cameras. Few of these were received however. It continued to fly Hurricanes on short range operations until 29th Aug 1945 when it ceased operations. The plan was for it to receive Spitfire FR.XIV which it finally turned up in Oct 1945 at which point the last of its Hurricanes were retired. It moved to Malaya in Nov.
34 & 113 squadrons traded Hurricanes for Thunderbolts in March & April 1945 respectively while operating in Burma.
42 & 60 squadrons flew Hurricanes in the fighter bomber role in Burma until withdrawn to India in May 1945. There 42 disbanded in June (with the number plate reappearing on an existing Thunderbolt squadron) while 60 re-equipped with Thunderbolts.
Some Royal Indian Air Force squadrons continued to use Hurricanes into 1946. In early 1945 (Feb-May) most of the Hurricane equipped squadrons were withdrawn from Burma to India with the intention of re-equipping them with Spitfire VIII ss they became available from May. Several were redeployed on the NW Frontier.
With the recapture of Rangoon at the beginning of May 1945 and the arrival if the SW monsoon a few weeks earlier than usual, large numbers of squadrons and ground units were withdrawn from Burma to firstly reduce the logistics burden, which was still to a large extent initially reliant on supplies coming down from India plus air supply (The USAAF withdrew its support for XIV Army at the end of May with transport aircraft redeployed on the "Hump" and fighter / bomber units being prepared to move into China), and secondly to allow units to prepare for the invasion of Malaya, and thirdly to allow release of long serving personnel entitled to return to Britain under the Python scheme.
Fighting continued in Burma right to the end as the Japanese tried to withdraw East into Thailand. These operations continued to require RAF support.
In the Mediterranean Hurricane IV were used operationally as part of the Balkan Air Force over Yugoslavia right to the end of the European war by 6 and 351 squadrons. 6 squadron didn't finally begin to trade Hurricanes for Tempest VI until late 1946 when in Cyprus. 351 (Yugoslav) squadron operated alongside them until it disbanded in June 1945.
In the Far East Hurricanes were used operationally right to the end of the WW2 campaigns in Burma.
11 squadron was withdrawn from Burma in May 1945 and traded its Hurricane IIc for Spitfire FR.XIV which it flew into Malaya from an escort carrier in Sept as part of Operation Zipper.
20 squadron was withdrawn from Burma to India in mid-May 1945 following the arrival of the monsoon. There it received Spitfire VIII in Sept 1945 which it took to Thailand.
28 squadron, in the tactical recce role, reached Mingaladon outside Rangoon in late May 1945. It received 3 Spitfire XI in late July (first operational use on 11th Aug) to operate alongside its remaining Hurricanes. At the end of July 1945 it only had 6 serviceable Hurricanes on hand, but was told to expect 12 Hurricane IV as soon as the aircraft had been fitted with cameras. Few of these were received however. It continued to fly Hurricanes on short range operations until 29th Aug 1945 when it ceased operations. The plan was for it to receive Spitfire FR.XIV which it finally turned up in Oct 1945 at which point the last of its Hurricanes were retired. It moved to Malaya in Nov.
34 & 113 squadrons traded Hurricanes for Thunderbolts in March & April 1945 respectively while operating in Burma.
42 & 60 squadrons flew Hurricanes in the fighter bomber role in Burma until withdrawn to India in May 1945. There 42 disbanded in June (with the number plate reappearing on an existing Thunderbolt squadron) while 60 re-equipped with Thunderbolts.
Some Royal Indian Air Force squadrons continued to use Hurricanes into 1946. In early 1945 (Feb-May) most of the Hurricane equipped squadrons were withdrawn from Burma to India with the intention of re-equipping them with Spitfire VIII ss they became available from May. Several were redeployed on the NW Frontier.
With the recapture of Rangoon at the beginning of May 1945 and the arrival if the SW monsoon a few weeks earlier than usual, large numbers of squadrons and ground units were withdrawn from Burma to firstly reduce the logistics burden, which was still to a large extent initially reliant on supplies coming down from India plus air supply (The USAAF withdrew its support for XIV Army at the end of May with transport aircraft redeployed on the "Hump" and fighter / bomber units being prepared to move into China), and secondly to allow units to prepare for the invasion of Malaya, and thirdly to allow release of long serving personnel entitled to return to Britain under the Python scheme.
Fighting continued in Burma right to the end as the Japanese tried to withdraw East into Thailand. These operations continued to require RAF support.
And where are those extra P-40s going to come from in 1942? That type was in high demand everywhere. As it was there were diversions from the first British Lend Lease contract for 1,500 P-40E Kittyhawks to Australia, Canada & New Zealand as well as Brazil & China. The USAAF had a big need for them for its expanding fighter force and there was also the need to meet Soviet Lend Lease requirements.
And in 1941 the RAF was still trying to transition from Hurricane to Spitfire in Fighter Command. If you are converting Mk.II to Mk.V then that process has to slow down as existing airframe are withdrawn for that purpose.
Given that CBAF continued to churn out Mk.V Spitfires until mid-1943, it would suggest that there were not enough Merlin 60 series engines to allow a full changeover of production to the Mk.IX. So where are the additional Merlin 60 series going to come from for your plan? As it was the earliest Mk.IX were conversions of Mk.Vc airframe by Supermarine and by Rolls Royce Hucknall in late summer 1942.
Geoffrey Sinclair
Staff Sergeant
- 1,263
- Sep 30, 2021
Using Morgan and Shacklady, Spitfire forward fuselage fuel,
V 84 gallons
VII 96 gallons
VIII 96 gallons
IX 84 gallons
XIV 84 gallons
XVIII 84 gallons
XIX 84.5 gallons
F.21 85 gallons
The VII and VIII wing had shorter span ailerons.
All up the VII had 121.5 and the VIII had 126 gallons, the biggest wing tanks fitted to IX was 18 gallons, making total fuel 120 gallons. The larger any rear fuselage fuel tank is the heavier it is, the further aft it goes and the greater the problems of fuel moving around in a partially full tank result is more fuel needs to be burned to restore combat flying ability. It is the maximum internal fuel amount allowed before entering combat that determines maximum combat radius. Plenty of space below the wings to carry fuel even though the extra drag means fewer air miles per gallon than internal fuel gives.
Agreement to ship 200 fighters per month to USSR under protocols 1 to 3, 3,317 Hurricanes sent, 399 lost in transit, 117 rejected by USSR plus 378 extra to protocol of which 14 rejected. Total 3,695, the export reports say 3,677 sent, final exports 77 in March and 5 in April 1944. Britain effectively ended Hurricane exports in February 1944, of 10,018 recorded exports from April 1940 onwards, 170 were April 1944 to November 1945. To actually make the 200 per month US built fighters were sent to the USSR "on British Account".
UK production Hurricane requisition dates, 600 in 1936, 1,324 in 1938 (including extras to cover export sales), 2,200 in 1939, 4,088 in 1940, 4,762 in 1941, with the note some later production might have been requisitioned after 1941 and contracts would be signed after requisition. In 1940 Hawker built 1,310 Hurricanes, roughly half each at Brooklands and Langley, Gloster built 1,211.
Wood and Dempster report August 1940 cost Fighter Command 390 Hurricanes and Spitfires, September 395, throw in another 489 over the two months damaged beyond unit repair ability. British planning had to assume even greater losses from May/June 1941 onwards. Hurricane production in Britain 1941 to 1943, 3,169, 3,067, 2,742. In theory 2,400 a year promised to the USSR after June 1941, in reality more like 120 per month sent. Meantime Hurricane fighter bombers had lower loss rates than Blenheims.
Counting Brooklands and Langley separately, British Hurricane production lines, 1 to end September 1939, 3 to end January 1941, 4 to end March 1942, 3 to end September 1942, 2 to end October 1942, then back to 1.
The RAF census indicates Fighter Command and 2nd TAF combat units were about the only operators of Typhoons, few were in training units. In the 12 months March 1943 to February 1944 inclusive Fighter Command War Diaries reports 280 losses, while the aircraft census reports 833 losses which would indicate in round terms 500 or so Typhoons were reduced to spares in the time period. Looking at cumulative production that would give 1 working engine per airframe but would require storage of some airframes to allow a reserve of serviceable engines available for issue to units etc. as required. The obvious Typhoon problems resulted in the Hurricane V prototypes, a dedicated ground attack version but with a 25 to 30% more powerful engine, an order for 384 appears in the June 1943 RAF census, upped to 584 in August, gone in January 1944. Seems in February 1942 the RAF was forced to accept 1,250 Hurricanes in place of plans for 843 Typhoons, given the engine situation. For the WWI equivalent of engine problems see the ABC Dragonfly
Castle Bromwich built 1,474 Vc (ending in August) and 1,598 IX (starting in March) in 1943, any production shortfall from a non historic change would come out of mark V production. Westland finished mark V production in October 1943, it had started Seafire production in December 1942.
End June 1943 there were 242 Spitfire VIII on RAF strength, including 118 in transit, while 2 had been lost overseas, there were 715 IX, of these 156 with Fighter Command, another 210 in transit, 17 Middle East, 96 in North West Africa, after 184 losses at home and 29 overseas.
End December 1943, 746 Spitfire VIII, 166 in transit, 398 in Mediterranean, 84 in India, 11 to USAAF, 27 Australia, 2 lost in Britain, 17 overseas, there were 1,774 IX, 106 with Fighter Command, 774 in the Mediterranean, 46 in transit, 15 to USAAF, 300 lost in Britain, 87 overseas, 1 to instructional.
Minor point English Electric fitted Merlin XX to its Halifax II to end production in October 1943, Rootes was also fitting Merlin XX to Halifax V in 1944. The use of Merlin 22 replacing Merlin XX in Halifax began in early 1943.
V 84 gallons
VII 96 gallons
VIII 96 gallons
IX 84 gallons
XIV 84 gallons
XVIII 84 gallons
XIX 84.5 gallons
F.21 85 gallons
The VII and VIII wing had shorter span ailerons.
All up the VII had 121.5 and the VIII had 126 gallons, the biggest wing tanks fitted to IX was 18 gallons, making total fuel 120 gallons. The larger any rear fuselage fuel tank is the heavier it is, the further aft it goes and the greater the problems of fuel moving around in a partially full tank result is more fuel needs to be burned to restore combat flying ability. It is the maximum internal fuel amount allowed before entering combat that determines maximum combat radius. Plenty of space below the wings to carry fuel even though the extra drag means fewer air miles per gallon than internal fuel gives.
Agreement to ship 200 fighters per month to USSR under protocols 1 to 3, 3,317 Hurricanes sent, 399 lost in transit, 117 rejected by USSR plus 378 extra to protocol of which 14 rejected. Total 3,695, the export reports say 3,677 sent, final exports 77 in March and 5 in April 1944. Britain effectively ended Hurricane exports in February 1944, of 10,018 recorded exports from April 1940 onwards, 170 were April 1944 to November 1945. To actually make the 200 per month US built fighters were sent to the USSR "on British Account".
UK production Hurricane requisition dates, 600 in 1936, 1,324 in 1938 (including extras to cover export sales), 2,200 in 1939, 4,088 in 1940, 4,762 in 1941, with the note some later production might have been requisitioned after 1941 and contracts would be signed after requisition. In 1940 Hawker built 1,310 Hurricanes, roughly half each at Brooklands and Langley, Gloster built 1,211.
Wood and Dempster report August 1940 cost Fighter Command 390 Hurricanes and Spitfires, September 395, throw in another 489 over the two months damaged beyond unit repair ability. British planning had to assume even greater losses from May/June 1941 onwards. Hurricane production in Britain 1941 to 1943, 3,169, 3,067, 2,742. In theory 2,400 a year promised to the USSR after June 1941, in reality more like 120 per month sent. Meantime Hurricane fighter bombers had lower loss rates than Blenheims.
Counting Brooklands and Langley separately, British Hurricane production lines, 1 to end September 1939, 3 to end January 1941, 4 to end March 1942, 3 to end September 1942, 2 to end October 1942, then back to 1.
The RAF census indicates Fighter Command and 2nd TAF combat units were about the only operators of Typhoons, few were in training units. In the 12 months March 1943 to February 1944 inclusive Fighter Command War Diaries reports 280 losses, while the aircraft census reports 833 losses which would indicate in round terms 500 or so Typhoons were reduced to spares in the time period. Looking at cumulative production that would give 1 working engine per airframe but would require storage of some airframes to allow a reserve of serviceable engines available for issue to units etc. as required. The obvious Typhoon problems resulted in the Hurricane V prototypes, a dedicated ground attack version but with a 25 to 30% more powerful engine, an order for 384 appears in the June 1943 RAF census, upped to 584 in August, gone in January 1944. Seems in February 1942 the RAF was forced to accept 1,250 Hurricanes in place of plans for 843 Typhoons, given the engine situation. For the WWI equivalent of engine problems see the ABC Dragonfly
Castle Bromwich built 1,474 Vc (ending in August) and 1,598 IX (starting in March) in 1943, any production shortfall from a non historic change would come out of mark V production. Westland finished mark V production in October 1943, it had started Seafire production in December 1942.
End June 1943 there were 242 Spitfire VIII on RAF strength, including 118 in transit, while 2 had been lost overseas, there were 715 IX, of these 156 with Fighter Command, another 210 in transit, 17 Middle East, 96 in North West Africa, after 184 losses at home and 29 overseas.
End December 1943, 746 Spitfire VIII, 166 in transit, 398 in Mediterranean, 84 in India, 11 to USAAF, 27 Australia, 2 lost in Britain, 17 overseas, there were 1,774 IX, 106 with Fighter Command, 774 in the Mediterranean, 46 in transit, 15 to USAAF, 300 lost in Britain, 87 overseas, 1 to instructional.
Minor point English Electric fitted Merlin XX to its Halifax II to end production in October 1943, Rootes was also fitting Merlin XX to Halifax V in 1944. The use of Merlin 22 replacing Merlin XX in Halifax began in early 1943.
don4331
Senior Airman
Extending the LE tanks to rib 4 is challenging as it gets into the area where the dihedral is set in the wing. As a result, it crosses where the wing flexes in flight/landing. Note rib 5 needs to stay in the wing to properly secure the leading edge sheet metal. Making a sealed tank is challenging; allowing it to flex and maintain liquid tight way more difficult, making it sealed, flex and fit around the rib was judged not worth the effort? Also, moving into the "flat" portion of the wing, it becomes challenging to drain every last gallon out of the tank.
Adding an additional 10 gallon tank (to avoid the flex issue), but only being able to extract a fraction isn't worth the effort.
Is it CG change? Or that the heavier Merlin 2 stage, propeller and structure changes increase the entire aircraft's weight to the point where the 29 gallon rear tank no longer moved the CG so far aft that the Spitfire wasn't "unstable" anymore?
I would think if it was just the CG change, one could just add lead to the engine bearers. (Which would be bad for performance, but allow added range.)
