Spitfire Combat Radius (range) evolution, limitations?

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pbehn said:
It is the other way around, there were many aircraft that could fill the other niches but non were as good as the Allison engined Mustang at tactical recon.
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I'm not so sure I buy this, but it's an interesting argument. Allison Mustang was useful in a highly specialized niche, I'm not sure if I'm parsing your statement correctly, but are you saying that it would have been used in other roles (say, escorting low level bombing strikes?) if it hadn't been so badly needed as a PR fighter? There were a few other planes which could do that role, though maybe not precisely in the same niche.
 
From what I understand the Alisson Mustangs were the best at that role, it is a niche role but a very big niche. The British would have taken many more to do the job, others could do the job but not as well. The fact is that although the British would have taken more that wasnt a possibility, production had switched to the Merlin variants, so they ran what they had until they wore out. In the run up to D-Day and after "intel" came a close second to eliminating the LW as far as air operations go and the Alisson engined Mustang was best at it, the mission is only a success when you land back at base with the film.


ColFord made a post about it on this thread, I will try to find it.

It is on a different thread but here Post #21 Effects of converting of all surviving Mustang Is into LR Mustang X?

Which if the RAF goes down the path of converting all their surviving Mustang Mk.I & Mk.IA, what do the poor b****y Tac/R pilots use to fly all the reconnaissance tasks placed upon them in 1943 and 1944?

ACC and then later 2TAF went down this path in trying to identify potential replacement aircraft types looking forward to the point where the remaining numbers of Mustang Mk.I and Mk.IA would be reduced due to losses from all causes and the numbers of aircraft they needed to conduct all the required task was greater than what they had, with no direct replacements coming.

Up to early 1945, repeated RAF studies on the best low level Tactical Reconnaissance aircraft for the role came to the conclusion that what they wanted was more Allison engine Mustangs - essentially equivalent to the P-51A, but with the 4 x 20mm Hispano armament of the Mk.IA, and with a Malcolm Hood. But they couldn't get them so had to resort to major overhauls and major rebuilds of the existing airframes to keep them going as long as they could. Aircraft that would have previously been written off, wherever possible were repaired, rebuilt and put back into service - which leads to some interesting entries and following of aircraft histories on some of the RAF Aircraft Record Cards. Even required massive pressure by the RAF on the USAAF to get a shipment of new build Allison engines to the specification required by the RAF and engine overhaul kits in late 1943 into early 1944 to keep the RAF's Mustang Mk.I and Mk.IA operational until at least the final quarter of 1944 in order to support the Tac/R requirements for the Invasion. As it was, no more Allison engine Mustangs would be forthcoming in the numbers required by the RAF (the 50 Mustang Mk.IIs were a belated backfill for the aircraft taken from the earlier Mustang Mk.IA order) as by the time all this realistically played out the production line at NAA had already been turned over to Merlin engine Mustang production.

As it was, the additional efforts and demands placed on the Tac/R squadrons in providing reconnaissance on the German V weapons sites in northern France from late 1943 into early 1944 on top of all the invasion related reconnaissance demands, accelerated the reduction in available aircraft to the point where they were considering re-equipping front line RAF Tac/R Squadrons with Hurricane IIc aircraft as a stop gap for the invasion period if the numbers dropped too low. When the pilots in the RAF Tac/R Mustangs squadrons heard that, you can barely begin to imagine the reaction and comments made.

The potential and actual replacements for the Mustang Mk.I and Mk.IA in the RAF Tac/R Squadron all came with a reduction in capability (range, low altitude speed, visibility, camera installations, increased risk) that when the replacements did arrive, led to the RAF Reconnaissance Wings having to 'triage' the reconnaissance demands to match the demand to the capability of the available aircraft. As a result, quite a few demands had to be declined and that in turn led to negative comments from some within the Army about the level of reconnaissance support they were receiving - and they made sure those comments were echoed all the way up the chain of command.

So you 'solve' one problem, but create another with potentially dire consequences to getting the required reconnaissance coverage to support the campaign against the German V weapons, the Invasion and support of the Army in the field following the Invasion. The RAF Tac/R squadrons were not called "The Eyes of the Army" for nothing.

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I realize that P-51B etc. is not optimized for super low altitude, (neither is the Allison V-1710 really) but couldn't you still just use P-51B/C for that role? And then later maybe Tempests?

I also wonder if you couldn't add say a pair of guns to a Tac-R Spitfire variant...?

P-38s made fairly good recon birds though not necessarily for low altitude.
 
And that said, I don't personally see a problem with still building some Allison Mustangs through the war if there really was a demand for them, though I can understand why they were making B/C/D etc. instead, since they had more broad applications.
 
Wild_Bill_Kelso said:
Longer ranged Spit VIII also pretty good match for a FW 190 too.
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Any spitfire with a 2-stage Merlin was a good match for the Fw 190. Trick being the Fw 190 still can kill B-17s from east of Saarland, where even Spit VIII as-is was not rangy enough to be there, fight, and reliably return to base.


It would've required a major redesign of the Spitfire in order to make it 30-40 mph faster, if the engine remains the same.
A Spitfire VIII with another 40-50 imp gals of fuel behind the pilot was a road not taken, unfortunately.
 
Well I meant 30-40 mph faster than a Spit V. What I'm saying is, you take the 122 gallons of fuel from a Spit VIII, then add eight or nine items from Geoffrey Sinclair's list of drag improvements (many of which did not require a major redesign, I don't think) for example:

Multi ejectors---------------7.75
Remove Snowguard--------8.5
Internal BP windscreen-----3.75
Fared mirror----------------3.25
Whip antenna -------------.75
Flush chutes----------------1.25
Small cannon bulges ------0.25 (This ads up to 25.5 mph already)

Improved Finish -----------8.5 - (this brings it to +34 mph)

That puts you close to or over 400 mph right there, starting with a Spit Mk V and Merlin 40 or 50 series engine. I think all of these are fairly easy, with the exception of "improved finish". Then you get a Merlin 60 series engine, and you gradually introduce a few more changes, perhaps a bit more of the difficult ones:

All this should be both a speed and efficiency improvement. Maybe a 10-20% better version of a Mk VIII in terms of speed, how much would that translate to in terms of range? I am just guessing here as I don't know how much of the improved performance came from 100-200 more HP, how much from just having HP available at higher altitude, and how much from streamlining. But presumably Merlin 61 or whatever gives you another boost in speed.

That is version one of a longer ranged (and faster) Spitfire.

Then do another round of improvements for a second long range Mark:

Maybe some kind of improved venting from the cooler intake like done in the Mustang
Flush rivets? Did they have those already?
Retractable tail wheel (I think the Mk VIII already had this right? I'm not sure my Eduard model kit of a Spit VIII seems to have a fixed tailwheel)
Fully covered landing gear doors
Possibly a two gun version with more fuel?
Internal antenna?

etc.

I bet all that gives you another 15-20 mph

And then for the third long range mark, add still more fuel, like what you get from the PR marks or some of the later fighter marks.

Perhaps the biggest challenge here would be making something like the Mk VIII earlier and in such a way that it could be manufactured in large numbers. Maybe bring in some NAA people to help reorganize the plant
 
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Wild_Bill_Kelso said:
And that said, I don't personally see a problem with still building some Allison Mustangs through the war if there really was a demand for them, though I can understand why they were making B/C/D etc. instead, since they had more broad applications.
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Well there was a demand for them, but the demand for a long range escort was the top priority. The RAF did receive P-51B/C and D but the same situation existed, being a top class escort others had a call on them. Approx half of Spitfire Mk XIV were fitted with a camera but the Mustang ! and II had more than one.
 

Spitfire VIII was already with internal BP glass, somewhat improved finish (the Spitfire V was the low mark in that regard), small cannon bulges, without snowguard and with multi ejectors. It also had the increased cooling drag due to the radiator set being of greater front area.
Want to make Spitfire VII/VIII/IX really fast? Make the wholesale redesign of the cooling system.


The Spitfire V making 388 mph (after RAE nip and tuck) started as a 358 mph machine.



10-20% increase of speed due to nip & tuck aint gonna happen.
Flush rivets were applied where needed after the tests with split peas. I'm all for retractable tailwheel and fully covered landing gear doors, it took until 1945 to have those on Spitfire (and on Bf 109, for comparison). Internal antenna enclosed within a metallic body will not work well, the Farraday's cage applies. A 2-cannon version was there as-is, though I'm not sure whther the fabric-covered MG muzzles were still a thing by 1943-44.
The major redesign of the cooling system externals might've helped a great deal.


More/better/earlier Spitfires are certainly a matter for the what-if sub-forum. Me, I'd have Boulton-Paul and Westland jump at the bandwagon by 1938 - meaning no Defiant, no Whirlwind.
A Spitfire IX and VIII with a good fuel tank behind pilot would've been a great asset for the Allies by early 1943.
 
So in terms of range, they couldn't extend far enough out to defend their airspace? As for maintenance issues, it had to do with that weird bent spar thing right?
Getting back to the main subject of the OP, looking at Geoffrey Sinclair's post with all the Spitfire drag improvements here Spitfire Combat Radius (range) evolution, limitations?
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Looking at the figures, I'm not sure how 'ideal' differs from 'realistic combat' mods. Needless to say, some of those modifications look pretty useful, though I'm not sure what mods were fitted to the Mk.IX in the 'ideal' configuration. Regardless lower drag generally means longer range, and you'd also have better acceleration and climb-rates.
I do know that the MK VIII had a few of these drag improvements built in, which is part of why it was faster, but there was still room for many more.
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Which ones, if I may ask?
Conceivably, you could fit even more fuel in, given that the range of the PR Spits was so good. There has to be some room between 'no guns' and 'six guns' where you could fit some more petrol instead.
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I'm not sure how much could be fit in the wing but there were two (I think, they could have been the same idea) proposed tanks: One was 16.5 imperial gallons proposed by the USAAF (they reconfigured a Mk.IX), and another was a 17 imperial gallon set-up (I think) the RAF looked into. Not sure why it was rejected.

Shortround6 said:
There are some 3d illustrations of the tail wheel of the Spitfire and the structure around it on the internet. . . . In fact you would probably want to manufacture the retracting tail wheel models on different assembly lines than the non retracts.
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So, the problem was that it was either incompatible with the Mk.IX or was different past a certain frame on the aircraft and would have required some components from a different assembly line to make the modifications?

While I know the production lines for the Mk.VIII ultimately ended up going to other Spitfire variants, were the jigs used for the tail-wheel used as is, or were they destroyed? I figure if they weren't destroyed, it would be possible to just lift them over and fold it into the late Mk.IX line.

If I recall the PR.I Type-D was the bowser-winged design with 2 x 66.5 imperial gallon tanks, correct? Did it have a tank behind the pilot or not?
 
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Incremental speed improvement don't usually "add up." That is, any single change may add the amount shown, but adding ALL of them doesn't just add up to that much speed gain. Many NACA reports and USAAF reports show this to be true. Would be nice of it di, though ...
 

The Spitfires at Darwin is quite a sad and deeply tricky story. I recommend reading a couple of articles about it as it is a classic example of a military institution under pressure, failing to make the most of a good piece of hardware that was desperately needed. The manufacturing issue was with Australian made ammunition, which apparently had a number of serious problems. Off the top of my head, other issues included guns freezing at altitude (apparently due to heaters either not being installed or not being maintained properly) either hydraulic and / or fuel lines freezing or rupturing because they had not been drained properly before shipment, problems with the radios, and a few other things I've forgotten. I think there was an issue with the coolant in the radiators.

There was a tactical aspect too. The commander, an Australian Ace named Clive Caldwell, had learned the hard way fighting in North Africa that the fighters needed to fly in big, tight formations and turn into enemy attacks, lest they be picked off by speedy, fast climbing, high-flying Bf 109s. But in Australia the fight against the A6M and Ki-43 was different and required different tactics. So a lot of fuel was wasted by mostly inexperienced pilots forming up in large formations before the fight.

The big problem was fuel though. They would climb to altitude, form up, and fly around for a while, being vectored toward the incoming Japanese raids, but by the time they got to them (or before) they often ran low on fuel. This was just one of the dismal incidents:

Raid on Darwin (2 May 1943) - Wikipedia

en.wikipedia.org

It's a good example of why flight endurance matters even for interceptors and point defense aircraft.

While I know the PR variants aren't realistic examples of combat aircraft, but it does illustrate examples of what can be added to an aircraft.

Agreed! I mean PR variants are combat aircraft, they just aren't equipped to shoot down other aircraft. But if you can make a PR Spit with a 1500 mile range conceivably there is a way to make a fighter Spit with a 900 mile range or so, even if you have to delete a couple of guns.
 
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I can imagine some cases where this might be the case, in the sense that several things may be causing similar types of drag and until you eliminate all of them, you will still have basically the same amount of drag. There are naturally certain design limitations on airframe and engine power that can't be exceeded by reducing drag. No amount of streamlining is going to make a piper cub go 300 mph (unless the 'streamlining' meant removing the wings, and then it's only going to go that fast once....).

But I also suspect that this factor would depend a great deal on which improvements you are referring to. In this case, according to the post I linked by Geoffrey Sinclair, the effects were cumulative on speed, and it increased the speed of a Spt V from 358 to 388 mph. This is what I was referring to. I believe Tomo mentioned the same thing in his post.

The emphasis here though is not just on top speed, but more specifically on drag. As you reduce drag you will not just improve top speed, it will take less time and energy to get up to speed, you will accelerate more quickly and decelerate more slowly at the same engine power. And all this also means range / flight endurance will improve.

There are many other examples of this of course, Bf 109E to F is a good one. I think the differences from the P-40 to P-51 are also illustrative (I mean beyond the superior low-drag wing design). Things like having a retractable tailwheel, removing sway braces, completely covered main landing gear, (and retractable vs. fixed main landing gear), switching from external to internal bracing, and of course, improving engine exhaust flow all do increase speed. But I've also read about field improvements done by different combat units where multiple smaller things (sanding and waxing, faring over rearview mirrors) also had a cumulative effect. So respectfully, I would say there are exceptions to this rule you are referring to.
 
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Having small improvements add up to a total speed increase is not my experience with warbirds at all, and it also doesn't work very well with civil aircraft, either, say a Mooney 201. I have a good friend who has one. There are lots of mods out there and each has a speed increase associated with it. Adding them all will NOT give you an additive speed increase.

It might if you add something to a wingtip and another thing to the bottom of the fuselage but, if both the things are on the fuselage, they just don't add up because they tend to interact when both are anywhere near the same airflow. Other posts don't trump real life airplanes trying to go faster, and there are a lot of those. Let's see, the Bonanza crowd (though they shouldn't since they are already almost dangerously near redline at cruise), anyone in the Van's RV family (almost dangerously near the flutter limit when painted like a typical homebuilder chooses paint), Mooney M20s, and all the warbirds at Reno, just to name a few. I don't know of anyone in there who has achieved an additive speed increase with more than two mods that were well-separated in the free airflow. These mods were usually gear doors or better wheelpants and wingtips. These two, at least, do not usually interact with one another.
 
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Some of the differences quoted like snow guards are in "reverse" taking a snow guard off the air intake may add 8 MPH but how many Spitfires were fitted with snow guards, same with windscreens the biggest difference is between the conical windscreen and others. Air resistance is exponential, try sitting bolt upright on a motorcycle at 40MPH pleasant breeze on a sunny day, 80MPH tiring on long journeys, 120 MPH very hard work only possible for a short time, 160 MPH like hanging from a metal bar with all your family holding your feet. All these drag saving measures were saving from the same speed zone, to jump up you need to be much more slippery or have much more power. NAA proposed to the British that the speed of the nascent Mustang I could be increased by shortening the wingspan, the British declined or would only accept if it had no negative effects on take off runs and rate of climb. In view of its later use that was a great decision, but wouldnt please those who put top speed above all things.
 
GregP said:
Incremental speed improvement don't usually "add up."
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I had thought the same thing, but considering they posted the change in speed measured, I figured they meant the total contribution.

Wild_Bill_Kelso said:
The Spitfires at Darwin is quite a sad and deeply tricky story.
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Yikes...
What tactics were adopted? I assume hit & run because of the Spitfire's speed advantages (particularly in dives).
if you can make a PR Spit with a 1500 mile range conceivably there is a way to make a fighter Spit with a 900 mile range or so, even if you have to delete a couple of guns.
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Yeah, it basically gives ideas of what you can stuff where.

It seems there's some stuff you can put in various locations which were shown in various Spitfire variants that I've noticed
  • Spitfire PR Type B/PR. Mk.II: 29 imp. gallon tank added behind pilot
  • Spitfire PR Type C/PR. Mk.III: As with PR. Mk.II, plus 30 gallon tank in a streamlined fairing under one of the wings (counterbalanced a camera in the other).
    • Doesn't seem terribly useful owing to the fact that drop tanks can be punched off.
  • Nonspecific PR Variant: Some mention of a 20-30 imp. gallon tank carried directly under the pilot.
  • Spitfire PR (General): D-winged versions, sometimes called the bowser wing, carried 66.5 imp. gallons in each wing, for a total of 133 imperial gallons in addition to the normal 85 gallons carried on all earlier marks.
    • Doesn't seem a practical idea for a fighter because the need for cannons. I suppose one could extend the 13 imp. gallon tank in the later Mk.VII/VIII wing to the point where it reaches the structural member that houses the aircraft's armament. It would appear that 4 x 20mm or 2 x 20mm + 2 x 0.50" are the best armament options which still yields around 53 imp. gallons a wings (total of 106 imp gal) provided the pipework can be worked around the guns in a way the RAF would have accepted (I said that in that way intentionally, there's unorthodox ways to get things done, but not everybody will accept them, lol).
  • Seafire: They mentioned carrying a drop-tank fitted for a P-40 which also improved aerodynamic handling (hey, navies seem to kluge best)
  • Spitfire Mk.VII/VIII: 13 or 13.5 (unsure which, most sources say 13, but W wuzak said 13.5) carried inside the inboard wings.
  • Spitfire Mk.IX: This variant seemed all over the place!
    • Early versions had 85 imp. gallons only
    • Later on they added provision for aft tanks with the upper section carrying either 41 or 42 imp. gallons. (a pilot's manual I've found on avialogs seems to indicate 75 imp gals in the rear tank), the lower carrying 33.
    • Then they increased the fuel capacity in the forward tank for either 95 (48+47 cited in manual) or 96 imp. gallons (48+48 in a diagram, 49+47 in some sources).
    • The bubble-canopy variants have 66 imp. gallons aft. It would appear that, in addition to the traditional slipper-tanks, it was possible to carry a 50 imp.gal torpedo tank under the centerline on some of the Mk.IX's.
    • There was a Mk.IX that was modified in the states: It appeared 16.5 imp. gallon tanks were added in the inboard wing, a 43 imp. gallon aft tank, and a pair of 62.5 imp. gallon external tanks. I'm not sure if the forward tanks carried 95-96 imperial gallons and if the 43 imp. gallon tank was used in lieu of the earlier 41-42 imp. gallon one, but it was said to present problems in the following ways.
      • When the tanks were jettisoned at speeds of 300 mph or greater, it actually struck the wing, denting it.
      • There was allegedly strength problems: I'm not sure if this had to do with the rear tank, or the drop-tanks (62.5 imp gals is around 75 US gallons, or 450 pounds of fuel, which is heavier than the normal 250-lb bomb load the plane was cleared to carry).
    • There appears to have been some Mk.IX that either carried a 17-18 imp. gallon tank (or was proposed to carry them).
Griffon powered variants seem to have some merits as well, though their fuel capacity was shorter, owing to their time-tables
  • Spitfire XII
    • First operational 1943/04/03
    • Notes: Timeline was good, but it had the same fuel capacity as the Mk.I/II
  • Spitfire Mk.XIV
    • First Operational 1944/03/12
    • Notes: It could carry 142 imp. gallons (Forward: 36+49; Wings: 2 x 13; Aft Fuselage: 31) internally with provision for 30, 45, or 90 imp. gallon slipper tanks or a 50 imp. gallon torpedo tank; the time-table definitely was doable (though it wasn't operational during the USAAF's Big Week, it was operational to some extent before April, 1944), but it was initially tied up in operations defending against V-1 attacks, which is kind of more important than escorting bombers.
  • Spitfire Mk.XVIII: Wasn't operational until after the war. It supposedly had more fuel capacity, but I have no idea what it was.
 

Well, I appreciate your insights, and I gather that you know whereof you speak, but in this particular case it seems to have been an actual thing that happened. I'm not just relying on some "other post", the one I referenced upthread (I'm not going to link it again, anyone who wanted to read it has done by now) seems to be well attributed. As in, that is what happened in real life - they took a Spit V and made a bunch of fairly minor changes, and it ended up going 30 mph faster so the changes did have cumulative effects. I take you at your word that aerodynamic improvements are tricky to implement in such a way that it has telling effect, but presumably these engineers were aware of that and knew what they were doing. Either that or they got real lucky, who knows. But whatever they did worked. I think that makes it pretty clear it can be done.

I also know of many other cases where this was actually done during the war with other aircraft, not just in the UK. There are several of these reports on WWiiaircraftperformance.org. I also know for a fact that a wheel door cover, flush riveting, retractable tail wheel, improved engine exhaust etc., WILL reduce drag. Whether that necessarily translates into x number of mph in speed increase, I don't know. How applicable it is to modern aircraft made with modern manufacturing standards, or already improved for racing, i can't say. I'm not an engineer, hell I can barely do simple maintenance on my car. But I am familiar with historical documents, research, and like most of you, I've read plenty of primary sources from WW2.

So you can say what you like, but I'm pretty sure this is 100% real.
 
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Interesting, I thought Spit Mk VIII had two tanks in the wings plus an increased main fuselage tank.
 

Supermarine were the sole producer of the Mk.VIII. Production of that model ended in Dec 1944.

By then Mk.IX/XVI was being produced only by CBAF where it continued until Aug 1945. BUT CBAF was, in Dec 1944, already in the process of changing over to producing the Mk.XXI.

Why would you want to further disrupt production at CBAF to implement change on a run out model? Especially when the change will deliver negligible benefit in the real world. In performance terms there is next to nothing to choose between a Mk.VIII and a Mk.IX.

Added to which some of them could probably be switched to the Mk.XIV already being produced in parallel at Supermarine.
 

Not really. They got the general Spitfire up to 408 mph, but it wasn't the same as a Mk V airframe with modifications. Later Griffon Spitfires were also changed airframes and were longer and sleeker. So, yes, they could make a Spitfire go faster, but no, it wasn't a modified Mk. V airframe anymore.

A MK. V was 29 ft 11 in long and came in at 6,525 pounds loaded. Top speed was 371 mph at 20,000 ft and 350 mph at 5,900 ft. This from either 1,470 or 1,585 hp, depending on whether it has a Merlin 45 or a Merlin 50.

A Spitfire XIV was 32 ft 8 in long and came in at 8,574 pounds loaded. Top speed was 449 mph at 24,500 ft. This from a Griffon 65 of 2,050 hp.

Let's take the 371 mph. Using the standard cube root of the power increase, we'd expect the XIV to go 414 mph just due to the power change. Since it went 449 mph, the difference was a change in drag. They weren't much like the same airframe, with the exception of the wing and, rather naturally, the XIV would not turn or handle like a MK. V since it was a ton and half heavier with essentially the same wing. It DID go faster, largely with a huge does of horsepower, but also with reduced drag. That didn't come from a series of small mods but rather from a general cleanup of the fuselage when the Griffon was fitted with a 5-bladed prop and the new tail and overall streamlining were changed.
 
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