Spitfire Combat Radius (range) evolution, limitations?

IdahoRenegade said:

I understand the Spitfire was more limited in range than some other fighters. I'm curious, year by year, what was the combat radius that could be achieved (with a combat-suitable, drop tank (not a fixed ferry tank)). How much did this harm it's usefulness once past the BOB, when the fighting turned towards offensive war, rather than as a point defense fighter? And how much did the Griffin engine drop the range (I'm assuming the larger, more powerful engine returned poorer fuel efficiency). Wikipedia shows a 470 mile combat radius, but doesn't tell what variant or aux tanks it would be equipped with. I haven't found much else definitive. Specifically, fighter variants, not recon versions.

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A bit late in a thread, sorry. Actually, it's not an answer, I do share your feelings about lack of data. It seems that the question of range or fuel consumption was not considered as very important. For example, on a premium site about Spitfire (WWII Aircraft Performance), there is a big article about direct comparison between Spitfire and Me109 - Spitfire Mk. I versus Me 109 E (Spitfire Mk I versus Me 109 E)

At the very end, there are just few rows under Miscellaneous Particulars





On the other hand, the same report stated maximum power of Merlin III as 1310 HP at 9,000 ft, while DB 601 A was rated as 1036 HP at 5,250 ft... So, basically 25% more power, and 20 % more fuel consumed.....

1310/1036 1,26 so 26% more power ~25%
89/69 1,29 so 29% more fuel ≠ 20%

Looking at the Spitfire pilot manual for the IX, XI, ands XVI, we find that all of these Spitfires had a 48-gallon upper tank in the nose. The manual is British, so the "gallons" are naturally Imperial gallons. Normal Spitfires had an additional 37 gallons under the top tank. Fuselages considered "rear view," had 47 gallons. So, depending on "rear view," they had either 85 or 95 gallons. This translates into 92.4 and 104.4 U.S. gallons, if the added extra tanks are not used, as they normally weren't.

Later Mk. IX and all XVI Spitfires also had two additional tanks behind the pilot that were normally wired shut and were normally unused. On regular Spitfires, these added up to an extra 75 gallons. In "rear view" fuselages, it was another 66 gallons. These were used only for "Special Ops." In U.S. gallons, these added 90 or 79.2 U.S. gallons each.

That makes for a total of 192 or 193.2 U.S. gallons for regular and "rear view" fuselages.

The Merlin burns 130 gph at 3,000 rpm and +15 psi boost for combat. These are Imperial gallons. In U.S. gallons, that is 156.6 gph. At a 2,400 rpm cruise at +4 psi boost, it burns 54.78 U.S. gph.

Assume we have 85 Imp gallons or 92.4 U.S. gallons of fuel to start with and we allow for 5 minutes of combat. That burns 13.05 U.S. gallons. If we cruise for the rest of the time at 2,400 rpm and +4 psi boost, we have about 78 minutes of fuel remaining. Assume we want 20 minutes of reserve, so that leaves about 58 minutes of cruise at 170 – 200 mph. Assume 200 mph cruise. We can cruise outward for 29 minutes and back for 29 minutes. That means the cruise range is 96.7 miles exclusive of combat. If we start with the 95 Imp gallons, that range, or actually radius of action, becomes a whopping 115.0 miles exclusive of combat. If we are at 170 mph, the ranges for 85 and 95 Imp gallons become 82.2 and 97.8 miles.

For special ops, let's assume we have the two normally unused rear tanks full and we have 160 Imp gallons (192 U.S. gallons). Assume the same power settings, fuel consumption, and 20 minutes of reserve. The range at 170 mph suddenly become 249.3 miles and, at 200 mph, we have a range of 293.3 miles.

Recall, these ranges are really radii, not one-way ranges, and DO NOT take into account for startup, taxi, takeoff, and climb to altitude. Real radii will be less.

I have placed these ranges on a WWII map of Europe below, centered over London (have to be centered SOMEWHERE).



The small inner circles are without the "extra" tanks that were not normally used. The large outer circles are with the normally-unused extra tanks. WITHOUT the "extra" tanks, they barely make the continent. WITH the "extra" tanks, they barely make Germany, much less Berlin.

Now, later in the war, when based inside continental Europe, that might be another story. If you take off from Western Germany without extra tanks, you STILL can't make Berlin and back. With the extra tanks, you can.

The manual really doesn't SAY if a Spitfire with fuel in the extra tanks is combat-ready or not. I am assuming mostly not, but it might be they are.

You forgot to add a drop tank, the Spit could carry up to 100G in a torpedo tank which gets you to Berlin, the fighter bases were right on the coast, even the Mustangs were as close to the channel as possible. I doubt any aircraft could make it to Berlin and back on internal fuel only.

PAT303 said:

The biggest problem dive bombing with the Spit was speed, during training they practiced with smoke bombs but when they started operations over Normandy with real 500 pounders they found they would hit 400+ mph within seconds giving the pilots very little time to adjust, also the bombs fuses wouldn't work effectively, they were designed to arm after being dropped horizontally from a bomber not vertically in a dive.

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I wonder what had a bigger effect, the extra 1000lbs or a lack of dive brakes in the increased dive speed? I wonder if the Brits tried adding drag with the gear down and the old tried and true pilot sticking his cupped (more efficient than a flat hand because you are literally catching air in the cup of the hand) hand out the canopy?

I didn't forget to add a drop tank. I posted the basic radius on internal fuel. Drop tanks are another calculation problem that I'll leave to anyone who is interested.

But, just eyeballing it quickly, at cruise the Merlin burns only about 55 gph, so a 100-gallon (Imperial gallons) drop tank is really 120 U.S. gallons and the Spitfire will go very slightly more than another 2 hours. Call it two hours.

So, at 200 mph, the radius is another 200 miles (1 hour out at 200 mph and 1 hour back), which STILL doesn't get it to Berlin and back from London, even with the "extra tanks" full. What is worse is that if the 5 minutes of combat comes at the extreme radius, meaning the drop tanks are dropped, it might not make it back to England, either. So, I'd say long-range escort is not exactly the forte of the Spitfire and, in real life, it wasn't EVER going to be.

London to Berlin is about 580 miles, East Anglia to Berlin is about 510 miles, warm up taxi take off and climb to 25,000ft on the top rear 33G tank, that fixes the handling problem, cruise on the DT as far as you can go which is most of Germany leaving you 42G in the rear, 96G in the main and 26G in the leading edge tanks, if the leading edge tanks are extended inwards to rib 1 like the PR versions you have 50G. Read my post #34, the Spit could have roamed all over Germany from 1943 onwards.

If that is so, I wonder why they mostly didn't?

Surly the people flying them might have been interested. Yes, they participated in a few "Rhubarbs," but most of the strafing was done by long-range escorts returning at low altitude from escort duty when the Luftwaffe was mostly not an issue.

GregP said:

If that is so, I wonder why they mostly didn't?

Surly the people flying them might have been interested. Yes, they participated in a few "Rhubarbs," but most of the strafing was done by long-range escorts returning at low altitude from escort duty when the Luftwaffe was mostly not an issue.

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Did anyone ask in 1943?

There was an actual war on at the time. Had it been a decent bet, they would have flown those missions, don't you think?

It's easy. The fuel they had is the fuel they had to go out and back. Adding a drop tank only gets you outbound for half the drop tank. Then, you'd best be headed home.

So, he flies for 2 hours at 200 mph and drops the drop tanks. He is 400 miles away and he has no fuel in the normally-unused "extra tanks. The internal fuel he has left will get him 2 * 96.7 or 2 * 115 miles back, which will fall well short of home base. If he HAS the extra tanks full, then he has about 2 * 250 or 2 * 293 miles to fly. So, he can go another 50 miles, fly 5 minutes of combat and make it home with 20 minutes reserve OR another almost 100 miles before doing the same.

The normally-unused ":extra" tanks are unused for a reason and, if he doesn't use them, the drop tanks can get him into a LOT of trouble OR they can allow him to fly combat patrol well within the return-home range on internal fuel, which is what they actually did.

PAT303 said:

London to Berlin is about 580 miles, East Anglia to Berlin is about 510 miles, warm up taxi take off and climb to 25,000ft on the top rear 33G tank, that fixes the handling problem, cruise on the DT as far as you can go which is most of Germany leaving you 42G in the rear, 96G in the main and 26G in the leading edge tanks, if the leading edge tanks are extended inwards to rib 1 like the PR versions you have 50G. Read my post #34, the Spit could have roamed all over Germany from 1943 onwards.

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PR Spitfire leading edge tanks were not sealed.

The total fuel that could be fit inside a PR leading edge tank was 66 UKG (each wing), the wing fuel bags for the VIII/XIV was 13,5 UKG (IIRC).

Is 50 UKG the total you expect for wing tanks extended inward? Double (Ish) what was in the VIII.XIV wings?

GregP said:

He is 400 miles away

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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?

wuzak said:

Is 50 UKG the total you expect for wing tanks extended inward? Double (Ish) what was in the VIII.XIV wings?

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Extend the tank inwards to rib one or two using the available space, that would give you 25-6G per side, 50-2G total.

wuzak said:

the wing fuel bags for the VIII/XIV was 13,5 UKG (IIRC).

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The MkXIV could take on all the current models of the 109 and 190 with the 90G slipper fitted giving even more range.

GregP said:

But, just eyeballing it quickly, at cruise the Merlin burns only about 55 gph, so a 100-gallon (Imperial gallons) drop tank is really 120 U.S. gallons and the Spitfire will go very slightly more than another 2 hours.

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I thought you had erred in your calculations, but reading an earlier post you have converted UKG to USG to get the 55 gph figure.

Then you converted 100 UKG to 120 USG to calculate your extra flight time.

Seems like a lot of converting.

PAT303 said:

https://images.squarespace-cdn.com/content/v1/531fdb48e4b0e8fbe6259952/1416114379008-4V3OH4A5TBUCCHD80S7S/image-asset.jpeg

Extend the tank inwards to rib one or two using the available space, that would give you 25-6G per side, 50-2G total.

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I understand now.

Looking at that picture, it wouldn't be so much an extension, but additional tanks.

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)

Now using 122 versus 124 gallons above

The mark VIII was 47+49 = 96 in front of the pilot, a 14 gallon tank in each wing = 124, the early IX 48+37 = 85. Under RAF rules the early mark IX range was 434 miles versus the VIII at 660 miles, or an additional 39 gallons for 226 miles, 5.8 miles per gallon. Interestingly the mark VIII.pilot's notes talk about a 26 gallon rear fuselage tank. Morgan and Shacklady talk about an 18 gallon Mareng bag in each wing for later mark IX. A late model IX with 95 in front of and 33 gallons behind the pilot has 128 gallons, versus the mark VIII with 124. If the IX also had the wing Mareng bags its fuel load would be another 36 gallons.

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.

If we have a mark VIII using 36+22 gallons combat and reserve it leaves 66 gallons of internal fuel, 1 hour, 320 miles, add some distance for economic cruise outside hostile airspace and gains during descent, subtract an allowance for formation flying.

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. Cumulative mark VIII production to end June 1943 was 252, halve that to account for reserves, training and losses and you have 125, around 6 or 7 squadrons, 2 wings, of Spitfires able to reach 300 miles radius under European conditions in a force able to sustain operations.

Turning to what if territory, adding a 33 gallon tank to the read fuselage of the mark VIII adds 160 miles to the range, that would require 140 to 150 gallons of external fuel to reach the new maximum possible radius. Rule of thumb seems to be 1 pound of self sealing fuel tank for 1 imperial gallon of capacity, external metal tanks maybe half of that. So 33+75 pounds of tanks, 183 gallons of 100 octane, over 1,400 pounds with around 270 pounds internal, Spitfires were cleared to carry 1,000 pounds of bombs. Use the lighter paper tanks and cut the external load to 140 gallons and save around 100 pounds.

According to the maps I have Friston England to Isselburg Germany is around 255 miles. (The road trip people say 286 miles but you need to drive to Harwich for a ferry), 610 squadron were using the Griffon engine mark XIV, which the pilots notes say had 111 gallons internal fuel plus the 90 gallon tank and the round trip is said to have used 130 to 140 gallons, allocate 40 gallons for combat and 20 for reserve and that is the fuel load.

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"."

OK, if the Spit had fuselage tanks that were never supposed to be used, wth were they there for? Looks?

I'll assume it's a weight/balance issue then? Or did they just say screw it, we got some room back here let's just slide some unusable fuel tanks in here for giggles?

Peter Gunn said:

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"."

OK, if the Spit had fuselage tanks that were never supposed to be used, wth were they there for? Looks?

I'll assume it's a weight/balance issue then? Or did they just say screw it, we got some room back here let's just slide some unusable fuel tanks in here for giggles?

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I think they were there because they were fitted without really being tested, they had severe effects on stability.

GregP said:

If that is so, I wonder why they mostly didn't?

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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.