A Critical Analysis of the RAF Air Superiority Campaign in India, Burma and Malaya in 1941-45

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No read that escort document again, it says that the Spitfire airframe is overstressed, but it doesn't say where.
 

I'm replying twice because there's two factors here. You provided a link where it was shown that a Spitfire V was shot down while carrying a 90IG slipper tank:


So we have Spitfire V (Vc Trops BTW) with a 90IG DT and, presumably 2 x 250lb bombs under the wings... This is about the same weight as a non-trop Vc aircraft would carry if it had a 75IG rear tank and twin internal (25IG total) wing tanks, which seems to suggest that a Vc could have been fitted with a 200IG of internal fuel and a 90IG slipper tank for long range escort duty. possibly during the Schweinfurt raids.
 
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Kevin J said:
No read that document again, it she that the Spitfire is overstressed, but it doesn't say where.
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The American test is for a Spit MK 9 not a Spit 8.

If a Mustang gets bounced its going to shed its wing tanks as fast as a Spitfire, many of those tanks were made of paper. We do know that the Hurricane could carry self sealing wing tanks stressed for combat and the Spitfire could carry self sealing slipper tanks stressed for combat. What options does the Mustang have?
 
That it could fly 1,000+ miles on internal fuel, at over 300 mph? So it didn't need to fight with the tanks?

And that it was used as a long range escort in the real world as opposed to in certain peoples imagination?

The idea of fighting with the tanks still on by the way came from RCAFs post. As a reminder, he wrote:

 

With the 170 IG slipper plus 114 IG internal there is 284 IG, armament was reduced to 2 LMG. So why? Is there something adversely affecting the wings with all that fuel in the fuselage?
 
Schweik said:
Remind me where in that passage is says those were 90 gallon tanks?
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The only mention of slipper tanks in that book is for the 90IG type which were supplied to USAAF Spitfires. But we can be certain that it was a 90IG tank because it still had fuel in it, where the 30 and 45IG tanks would have been empty by the time the squadron reached the French coast.
 
Kevin J said:
With the 170 IG slipper plus 114 IG internal there is 284 IG, armament was reduced to 2 LMG. So why? Is there something adversely affecting the wings with all that fuel in the fuselage?
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Yes, and as I stated earlier it was drag. The 170IG tank had 4 times the drag of the 90IG tank. Additionally, these were MkV Trops.
 
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I stated that the slipper tank (and ideally this would a 30 or 45IG slipper) could be retained in combat because it was stressed for combat and was SS. I've stated over and over that the wing tanks would be dropped ASA contact with the enemy occurred.
 


RCAFson,

I realize this is an exercise in "what if" and the trouble shooting/ problem solving associated with that endeavor.

With that in mind I will share a line of thought and ask a question or two. First, thoughts on combat with drop tanks. While I can't verify what the line guys were taught or the expectation was in combat I can make a few assumptions.

My background is mostly F-15A/C model (air to air versions), just shy of 2700 hours in type, Instructor Pilot (IP) with 106 combat sorties over Iraq. The question of when to jettison tanks, which ones, and under what circumstances was openly debated and ebbed / flowed a bit during the 17 years I flew the plane.

When entering the combat arena one must have situational awareness (SA) on the mission (offensive counter air AKA sweeps, defensive counter air or protection of something that isn't moving (air base, city, ship, etc) or escort). Each has its drivers with escort being focused on effective use of time on station. That means cruising at a speed that allows quick acceleration to combat speed, at an effective distance from the asset you are protecting, while minimizing fuel use to prolong time on station or in actual fights.

With that in the open one must know when to jettison tanks and the ramifications for doing so. Do it to early and your time on station drops below what's desired. To late and you have lost the offensive and are going to finish the war in a POW camp or worse, pay for your error with your or someone else's life. The Eagle had two different quality tanks. Ones suitable for training, and others for basically combat or ferrying only.

When entering an engagement with high SA, one has the initial luxury of deciding when to jettison the last of the tanks (assumption is the wing tanks are punched off at power up). With high SA, and superior numbers I would be comfortable fighting with a centerline external tank. If my SA dropped, more enemy aircraft entered the fight, or I perceived there was a chance of going neutral (in other words prior to going defensive) that tank would be gone. I also have the benefit of years of flying fighters that those kids did not. Also I might have a unique point of view but a self sealing jettisonable fuel tank means it will with stand gunfire? Okay, why does a guy still have it on if he is being shot at? The self sealing part is an oxymoron. You did give some excellent examples of guys fighting with external tanks. In a MkXIV with its monster motor and huge performance advantage over just about everything else I can see it. Or in a very benign fight. Otherwise I think it's a performance detriment at least and disaster at worst. Think Tommy McGuire. I also have literally hundreds of engagements experience to fall back on to help me determine MUCH earlier when things are turning against me as well as knowledge / discipline to not do something that rapidly puts me on the defensive. Those kids did not have that. I'm sure there were guys who were quick learners and well above average SA, but the program was pointed towards a guy with more "normal " skills and capabilities.

The long and short of it is please be very leery of thinking a guy will routinely fight with external tanks on.

Okay here are the questions I have.

1. What airspeeds/altitudes were you planning for the outbound leg, the escort leg, and the return leg? If I'm not mistaken the Mustang guys had three different speeds (probably four speeds as the RTB could be with or without drop tanks).

2. Is your outbound / rendezvous leg direct to the rejoin point, or does it vary to make it more difficult to determine (by the enemy) where the rejoin will occur? This obviously eats up range since it's not direct or a straight line. I'm under the impression this is how the US escorts operated.

Lots covered. I apologize if covered things you already understand, I was just attempting to build a level foundation.

Cheers,
Biff
 
RCAFson said:
and it could have been modded to carry wing torpedo DTs, as the USAAF proved
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The "mods" as proved by the USSAF would have required modified landing gear, to a greater or lesser degree. And quite possibly some beefed up structure. Neither are impossible, but the extent of the modifications are unknown.

P-51a routinely took off using, I believe, the left wing tank, switched to the rear tank to use up some of the fuel (post war, we may be comparing postwar P-51 restrictions to wartime Spitfire restrictions?) then switched to one or the other drop tanks (which sometimes had to switched back and forth to maintain lateral balance) when either combat was joined or the drop tanks were empty they were dropped and fuel switched to one of the wing tanks.
On the P-51D (post war) they wanted the pilot to keep some fuel in the rear tank (25 US gallons) until landing. Post war they also placarded the rear 85 gallon tank at 65 gallons.


I am not sure what the dive proves or disproves or why Gs in a pull out count different than Gs in a turn?
The post war manual for the P-51 says

"Combat Maneuvers should never be attempted when the fuselage tank contains more than 25 gallons of fuel, as the tail heavy condition could cause a reversal of control stick forces during any abrupt maneuver approaching 6.75G. At this point, forward pressure is needed to prevent the pull-out or turn from tightening up to the point were structural failure results. With the fuselage tank empty, stick forces are normal with slightly less pull force required above 6 G. However, a positive back pressure is needed up to maximum G load. "

On the next page in the section on diving under a WARNING banner it says that "The anti-G suit should be used with a constant 6 G pull-out."

During WW II the Mustang (before G suits) was being operated at what G rating in most combat turns????? there are always exceptions.

For sticking fuel tanks behind the pilot in the Spitfire please remember that there are 4 (or 4 1/2) different Spitfires.

The single stage Merlin powered ones.

The ones with the two stage Merlin, several hundred pounds more engine and prop let you stick a few more things in the rear of the plane( one weight and loading chart has 72lbs of ballast in the tail of a MK IX before rear tanks are fitted)

The MK XII with the single stage Griffon weight only a bit more than the two stage Merlin and only about 100 built

the MK XIV and later with the two stage Griffon that was hundreds of pounds heavier than the two stage Merlin.

The last of the 2 stage Griffon engines with counter rotating propellers.

While all of these planes need about the same center of gravity the increasing weight (and greater spread of the weights) meant a few more liberties could be taken with the later ones (which often got larger tail surfaces) as regards to weight placement.

We have to be careful as to which planes and in what condition/s we are using for comparisons.

I would also note that a dive bombing mission in which the bombs are released while the plane is pretty much traveling in a straight line (little additional G force) and once the bombs are gone a 4-6 G pull out is done is a bit different than trying to pull a 4-6 G turn in dog fight with external tanks still attached.

I would also note that in my opinion a single encounter proves nothing. If single encounters could be relied on as predictors of future combat performance then the RAF should have stopped production of both the Hurricane and Spitfire after the 1st of June 1940 and built Avro Ansons instead
Deadly Avro Anson

There is little doubt in my mind that the range of the Spitfire could have been improved. The questions seems to be by how much, when, and would it be enough?
Escorting to the Ruhr should have been no problem, escorting past middle Germany may have been a lot harder.
 

Lets state to begin with that there's several assumptions being made. The first is that LR high altitude escort fighters, based on the Spitfire MKVII/VIII are introduced in numbers in time for the Schweinfurt raids in Aug 1943. In August 1943 (and later) the performance of a Spitfire VII/VIII has to be compared to the fighters available to the Luftwaffe in the same time frame. 2ndly, Luftwaffe fighters flying Reich defence were also encumbered with a variety of external tanks and extra ordnance that effected their performance as well, so we can't fall into the trap of always comparing the best performing Luftwaffe fighters against that of a slipper tank encumbered Spitfire. If we look at a SpitV based LR escort fighter we have to bear this in mind as well.

AIUI SS was added to the slipper tank to help it withstand defensive fire from bomber rear gunner LMGs and maybe light shrapnel. WW2 SS tanks were not of much use against anything bigger than that. Additionally it was probably protection from tank leakage induced through stress on the tank seams during manoeuvre or simple defects. Slipper tanks were not considered as expendable as torpedo style tanks and the Pilot's Notes stress returning with them if possible.

We have to remember that in WW2 Allied bombers and fighters were built in the tens of thousands and were considered expendable, but fighters much more so than 4 engine bombers. If your Group draws the short straw and has to make the deepest penetration, you may have little choice but to keep the slipper tank and only drop it as a very last resort.

1) I don't have exact numbers, but as we've discussed the Spitfire had the same engine as a Mustang, so route planning could be essentially the same but with a ~10% reduction in cruise speed and the limitation that outward route planning has to be based upon smaller wing DTs than on the Mustang. This is where retaining the slipper tank, for as long as possible also makes things easier to equate to the historical 1944 route planning. Given the small wing DTs, I suspect that these would never be retained for more than a small portion of the return leg.

Our LR Spitfire starts with 200IG internal fuel, a 45IG slipper tank (ST) and two x 50IG DTs. TO, cruise climb to the French/Dutch coast to use the mandatory 50IG (TO on main, switch to rear Fuselage, burn 35IG for CoG reasons) So we reach the coast with the two DTs full, 150IG in internal fuel and 45IG in the ST. My educated guess is that the 100IG in the DTs is enough fuel for ~1.5 hrs at Max weak mixture, or about 450 miles @300mph TAS at 25-30k ft. 30K ft makes route planning easier because flak is not very effective at that altitude and interception from above is less likely. So the route plan has to intercept the bombers somewhere within a maximum of 450 miles flight distance from the French/Dutch coast. Given that Schweinfurt was about 300 miles from the coast, this provides a fair cushion for deceptive route plans.

2) This is somewhat answered above, and the total miles flown outbound cannot increase the distance to UK coastal airfields beyond the safe minimum fuel remaining after subtracting cruise and combat allowances along the rendezvous point. I suspect that about 100IG would be required to return from a mission to Schweinfurt (IE furthermost rejoin point).
 
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You put those big slipper tanks on it, it handles like an overloaded truck, and even with that great big thing messing up your air flow, you still can't actually make it to the Regensburg and back at a realistic, safe speed - or even for the Pacific or CBI.

It's a pipe dream, and that is why it was never done. Not because "they didn't need an escort fighter" they did, or "their bombers couldn't fly day missions" - they did.

They were desperate for a longer range Spitfire through the whole war but the best they got was the Spit VIII and later equivalents (in terms of reach).
 
Some really good posts here so that's gonna be a tough act to follow but im thinking its not a matter of could the Spitfire be made into a long range escort yes or no but a matter of degree. The range of the Spitfire shurly could have been extended, probably substantially but it's going to be less and less feasible the more fuel is added. Cog issues , possibly just not enough room for internal fuel past a certain point?
So I'm thinking it could have been done. It's just a matter of to what degree.
 
That's a 170IG slipper tank and was never intended for combat. Yes, it had 4 times the drag of the 90IG slipper.
 
Trying to stick much fuel behind the cockpit of the Spitfire MK V seems like a non-starter. The Merlin 45 was about 260lbs lighter than than the Merlins used in the MK VIII and IX. Prop was probably lighter too. granted they used the larger radiators to help balance the two stage planes but unless you start using armoured air intakes or lead weights in the engine compartment putting a lot of fuel behind the cockpit of a MK V is going to get you into trouble a lot faster than the same amount of fuel in MK IX.

The US figured 419 US gallons in/on a Mustang was good for a 700 mile radius with all the standard allowances. That 85 gallon rear tank was good for 225 miles. Without it and using a pair of 75 US gallon tanks the radius was 475 miles with 334 US gallons of fuel.

Distances may be rounded to the nearest 25 miles. Fuel is not exact, while the Mustangs wing tanks held 92 gallons only 90 gallons was actually useable.

The extra 65 gallons they stuck in the P-47 was good for 175 miles of radius. It improved the radius when using a pair of 150 gallon drop tanks from 425 miles to 600 miles.

The chart might have been made to make the P-47 look good or it might be a coincidence. The return flight is figured at 210 mph IAS at 25,000ft and 210 mph IAS is just about the limit for a P-47 running max lean power (105gph)

The extra 65 gallons was only worth about 100 miles of radius (125miles vs 225 miles) with no drop tanks as some of the fuel had to used in other parts of the flight aside from just the return.


getting back to the Spitfire, if it needs 10% more fuel than the Mustang to do the same thing (and this may be an error) then it needs over 2000lbs more fuel than the 96 gallons in the main tanks for a 700 mile radius. adjsut as needed for shorter radius. Yes you burn off quite a bit on the way in but how much does the Spitfire really need to fight and then escape/withdraw at similar speeds and altitudes to the P-51???

A Mustang carrying 419 gallons of fuel was carrying just about 2500lbs of fuel. 2500lbs of fuel (or 2750lbs for the extra 10%) is a bit much for the Spitfire so the question is what was a reasonable amount of fuel and when.
 

The Spitfire V was fitted with a 29IG fuselage tank for ferry purposes but this tank was installed at the top of the rear fuselage and so this was analogous to only having the the upper 40% of the 75IG tank full, which is what led to the CoG problems. I don't think we can rule out a rear fuselage tank, albeit with the same CoG limitations with full fuel.
 
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I think you are arguing for the sake of arguing, I suggest you read the links M Williams put up a page back, theirs evidence a plenty of Spitfires flying long range missions.
 


I agree and that often quoted article does not help, burning up the rear fuselage tank/s on take-off-climb to op altitude is not a good solution. U the drop tanks for climb out and early cruise and save even 1/2 the rear tank for the flight home if it s true it does not degrade flight characteristics.


I was just looking at ATH and we really have to be careful about which version of which airplane we are using for our examples. late model P-51Ds got metal covered elevators (like late model Spits) and this changed high speed handling to the point where they changed the incidence of the horizontal stabilizer from + 1 1/2 degrees to + 1/2 a degree. this also changed the amount of stick pressure needed for some flight maneuvers or trim changes.

I would also like to bring up the British cautions about not flying the Spitfire with the rear tanks on instruments or in close formation. Just what was the weather/cloud cover over europe on many days during the bombing campaign? are we going from a daylight fighter to a only minor clouds fighter? Or the comments about it being tiring to fly? You want worn out pilots entering combat after 2-3 hours in the cockpit? shades of the frozen P-38 pilots.

Edit, everybody opened up formations when flying through cloud so I didn't mean to count that against the Spitfire.
 
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PAT303 said:
I think you are arguing for the sake of arguing, I suggest you read the links M Williams put up a page back, theirs evidence a plenty of Spitfires flying long range missions.
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I looked at them, several of them have Spit XIVs with 90 gallon tanks flying about 2 hours give or take from take-off to landing. While quite useful it is hardly in the same league as flying to Schweinfurt is it?
The first one posted has a victory near the French town of Fleche is roughly the same distance as Paris depending on where in England you take off from.

There is no doubt that the 90 gallon tanks were used on operations, however the 90 gallon tank alone (or better said, in conjunction with standard fuselage tanks) does not give the needed range for missions much past the Rhine.
 
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