Jabberwocky
Staff Sergeant
Forgive the Wall-O-Text, but: The RAF had a viable design for a long-range escort fighter: the Spitfire.
Sounds odd I know, but it's not actually that unbelievable. Hear me out.
During 1937-1940, the RAF significantly developed the Spitfire Mk I for PR work, with a range of different fuel options. The PR Mk IB had a 29 gal fuel tank behind the pilot. It was unstable when the fuel tank was full, but once most of the fuel had burned off, the handling of the aircraft was almost as good as a regular Spitfire.
There was also the PR Mk ID, which had an extra 66 gal in the wings, replacing the armament and giving a total 218 imperial gallons. No rear tank was fitted though, as the aircraft balance was affected. It also had a larger oil tank, somewhat marring the wonderful lines of the nose.
Spitfire Mk Vs shuttled to Malta were successfully flown off aircraft carriers with 29 gal and 33 gal rear fuselage tanks, although they were removed once the aircraft got to Malta. The Mk Vs also flew with 29 gal rear tanks AND the 90 or 170 gal ferry tank (for a total of 284 imperial gallons).
Later in the war (late 1944) the RAF began fitting some Spitfire XVIs and Spitfire IXs with rear fuselage tanks of 41 gal total capacity. Versions with bubbletops had 33 gal.
There was also the PR Mk ID, which had an extra 66 gal in the wings, replacing the armament and giving a total 218 imperial gallons. No rear tank was fitted though, as the aircraft balance was affected. It also had a larger oil tank, somewhat marring the wonderful lines of the nose.
When time came to improve the Spitfire in 1939-1940, Joseph Smith came up with a couple of proposals for the Mk III. One of the main ones, which was eventually rolled into the Mk VII/VIII airframe was the enlarged front tanks, increasing standard fuel capacity from 85 to 95 imperial gallons. The Mk VII/VIII airframe also had two 12.5 gallon fuel tanks, in the leading edge of the wings, near the wing root.
If the airships in the Air Ministry, Portal in particular, hadn't been so opposed to the idea of a long range, single seat, single engine fighter in the late 1930s and early 1940s, then a Spitfire with double the range was practical, even in 1940/1941.
I believe that the rear-fuel tank is practical in the post-1940 period for the Spitfire, with a bit or re-arranging of some of the rear fuselage accessories:
A regular Mk V had 85 imperial gallons, and a standard range of 480-500 miles at best cruising conditions. With warm up, climb, fast cruise, combat and reserve allowances, the practical combat radius is about 170-80 miles. Rough rule of thumb is that RAF combat radii were between 35% and 37.5% of cruising range, perhaps a little more as range gets longer.
If we go with two concepts available and flying in Spitfires in 1940 – the enlarged nose tank and the rear fuselage tank – then internal fuel goes from 85 imp gal to 124 imp gal, an increase of about 45%.
Still air cruising range goes up to about 700-730 miles, and combat radius goes up to nearly 250 miles.
However, the big boost comes once you start adding external tankage. Drop tanks were fitted to Spitfire Mk Vbs about half-way through 1941. They came in many flavours, but the standard sizes in 1941 and 1942 were 30 imp gal and then 45 imp gal.
With a 45 imp gal slipper tank, total tankage goes to 169 imperial gallons, or just under double the fuel of a Mk I or Mk II.
So my theoretical 1941 long-range Spitfire Mk V would behave like this.
Allowances:
Warm-up/taxi/take-off (90 gph): 10 gal, no distance, 159 gallons left
20 minutes climb to 20,000 ft @160 mph (32 gph): 13 gal, 50 miles, 146 gallons left
Combat:
5 minutes at full throttle (90 gph): 7.5 gal, 30 miles, 138.5 gal left
15 minutes at fast cruise @ 315 mph: (67 gph): 17 gal, 80 miles, 121.5 gal left
Reserve:
30 minutes reserve @ 220 mph (32 gph): 16 gal, no distance [as its reserve], 105.5 gal left
Range cruise:
3 hours 20 minutes at range cruise @ 220 mph (32 gph): 105.5 gal, 730 miles, 0 gal left.
Total distance:
Climb – 50 miles
Combat – 100 miles
Cruise: - 730 miles
Total: ~880 miles
Combat radius: ~310 to 330 miles.
For every 5 minutes at full power, you can cut about 60-65 miles off the total range. For every five minutes at fast cruise, you can cut about 30-40 miles off the total range.
880 miles range is not too far off Mk VII/VIII performance (it might actually be understating the range a little). With 120 gal internal, the Mk VIII had still air cruise range of 660-740 miles and with a 45 gal slipper tank it had range of 885-940 miles, depending on whether it dumped or retained the slipper tank. The Merlin 66 also consumed a LOT more fuel at full boost of +18 than the Merlin 45 did at +9/+12. In 1944 Mk VIIs did bomber escort trips of 690 miles (round trip) to La Pallice and Mk IXs and Mk VIIs over 600 miles to Meerbeck and Emden.
You can probably quibble with some of the fuel consumption and speed figures, but I've used the RAAF Spitfire Mk Vc figures for 1943 as my baseline. The RAF might have flown at higher boost settings and thus got less range out of their Spitfires.
Sounds odd I know, but it's not actually that unbelievable. Hear me out.
During 1937-1940, the RAF significantly developed the Spitfire Mk I for PR work, with a range of different fuel options. The PR Mk IB had a 29 gal fuel tank behind the pilot. It was unstable when the fuel tank was full, but once most of the fuel had burned off, the handling of the aircraft was almost as good as a regular Spitfire.
There was also the PR Mk ID, which had an extra 66 gal in the wings, replacing the armament and giving a total 218 imperial gallons. No rear tank was fitted though, as the aircraft balance was affected. It also had a larger oil tank, somewhat marring the wonderful lines of the nose.
Spitfire Mk Vs shuttled to Malta were successfully flown off aircraft carriers with 29 gal and 33 gal rear fuselage tanks, although they were removed once the aircraft got to Malta. The Mk Vs also flew with 29 gal rear tanks AND the 90 or 170 gal ferry tank (for a total of 284 imperial gallons).
Later in the war (late 1944) the RAF began fitting some Spitfire XVIs and Spitfire IXs with rear fuselage tanks of 41 gal total capacity. Versions with bubbletops had 33 gal.
There was also the PR Mk ID, which had an extra 66 gal in the wings, replacing the armament and giving a total 218 imperial gallons. No rear tank was fitted though, as the aircraft balance was affected. It also had a larger oil tank, somewhat marring the wonderful lines of the nose.
When time came to improve the Spitfire in 1939-1940, Joseph Smith came up with a couple of proposals for the Mk III. One of the main ones, which was eventually rolled into the Mk VII/VIII airframe was the enlarged front tanks, increasing standard fuel capacity from 85 to 95 imperial gallons. The Mk VII/VIII airframe also had two 12.5 gallon fuel tanks, in the leading edge of the wings, near the wing root.
If the airships in the Air Ministry, Portal in particular, hadn't been so opposed to the idea of a long range, single seat, single engine fighter in the late 1930s and early 1940s, then a Spitfire with double the range was practical, even in 1940/1941.
I believe that the rear-fuel tank is practical in the post-1940 period for the Spitfire, with a bit or re-arranging of some of the rear fuselage accessories:
A regular Mk V had 85 imperial gallons, and a standard range of 480-500 miles at best cruising conditions. With warm up, climb, fast cruise, combat and reserve allowances, the practical combat radius is about 170-80 miles. Rough rule of thumb is that RAF combat radii were between 35% and 37.5% of cruising range, perhaps a little more as range gets longer.
If we go with two concepts available and flying in Spitfires in 1940 – the enlarged nose tank and the rear fuselage tank – then internal fuel goes from 85 imp gal to 124 imp gal, an increase of about 45%.
Still air cruising range goes up to about 700-730 miles, and combat radius goes up to nearly 250 miles.
However, the big boost comes once you start adding external tankage. Drop tanks were fitted to Spitfire Mk Vbs about half-way through 1941. They came in many flavours, but the standard sizes in 1941 and 1942 were 30 imp gal and then 45 imp gal.
With a 45 imp gal slipper tank, total tankage goes to 169 imperial gallons, or just under double the fuel of a Mk I or Mk II.
So my theoretical 1941 long-range Spitfire Mk V would behave like this.
Allowances:
Warm-up/taxi/take-off (90 gph): 10 gal, no distance, 159 gallons left
20 minutes climb to 20,000 ft @160 mph (32 gph): 13 gal, 50 miles, 146 gallons left
Combat:
5 minutes at full throttle (90 gph): 7.5 gal, 30 miles, 138.5 gal left
15 minutes at fast cruise @ 315 mph: (67 gph): 17 gal, 80 miles, 121.5 gal left
Reserve:
30 minutes reserve @ 220 mph (32 gph): 16 gal, no distance [as its reserve], 105.5 gal left
Range cruise:
3 hours 20 minutes at range cruise @ 220 mph (32 gph): 105.5 gal, 730 miles, 0 gal left.
Total distance:
Climb – 50 miles
Combat – 100 miles
Cruise: - 730 miles
Total: ~880 miles
Combat radius: ~310 to 330 miles.
For every 5 minutes at full power, you can cut about 60-65 miles off the total range. For every five minutes at fast cruise, you can cut about 30-40 miles off the total range.
880 miles range is not too far off Mk VII/VIII performance (it might actually be understating the range a little). With 120 gal internal, the Mk VIII had still air cruise range of 660-740 miles and with a 45 gal slipper tank it had range of 885-940 miles, depending on whether it dumped or retained the slipper tank. The Merlin 66 also consumed a LOT more fuel at full boost of +18 than the Merlin 45 did at +9/+12. In 1944 Mk VIIs did bomber escort trips of 690 miles (round trip) to La Pallice and Mk IXs and Mk VIIs over 600 miles to Meerbeck and Emden.
You can probably quibble with some of the fuel consumption and speed figures, but I've used the RAAF Spitfire Mk Vc figures for 1943 as my baseline. The RAF might have flown at higher boost settings and thus got less range out of their Spitfires.
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