British escort fighter--what might it have been like?

[tomo pauk]

But the Germans were not sticking DB 601A engines in 6200lb fighters (Spit 1 & II with normal fuel) , they were sticking them in 5500-5800lb fighters. Being 6% lighter is not much but it does help to level the playing field a bit.

At 20000 ft, Merlin III was making 890 HP. DB 601A was good for 800 PS there (old S/C) or 850 PS (new S/C). So the Merlin III was giving 11% or 4% more at that altitude.
Merlin X was good for 1010 HP at 17750 ft (due to improved impeller vs. Mk.III), where DB 601A was making 840 PS or 920 PS, depending on S/C. Merlin XII was a tad better than the Merlin X due to faster-spinning impeller than the Mk.III (still the same impeller), but was later by about a year?
All values as for no ram effect.

Seems that power to weight ratio is still on the side of Spitfire, especially if the Merlin X or XII is installed. Even the worst case scenario - Mk.III vs. 601A with new S/C, the power to weight ratio of whole fighters is in the ballpark. Spitfire still has the more favorable wing loading.

100 octane doesn't do quite as much for the escort fighters as if they get sucked down to lower altitudes where the 100 octane makes a difference they are no longer protecting the bombers (they are below them and while German fighters they shoot down today cannot attack tomorrow, Spitfires below the bombers are not stopping German fighters attacking form above today. )

Spitfire that is chasing a 109 at 15000 ft is doing it's job - there is one 109 less for the bombers to worry.

British had to change their doctrine in 1936-37. You need different airfields for both bombers and fighters, you need to build another propeller factory (or two). You need more gun turrets, you need at least one different bomber, Hampdens in daylight are not going to work , Whitley was ordered as a night bomber, they knew it could not fly in daylight and survive and that was against biplanes.

They certainly need to change the doctrine early enough.
Propeller are easy: don't make hundreds and thousands of clunkers (aircraft that were either obsolete, or not used in the role they were purchased for, or were complete waste of resources) + Whirlwind; this also frees a lot of RR production so there are many hundreds of Merlin available. Hampdens certainly don't work in daylight when unescorted, as it was the case with German bombers.
Less clunkers of the bombers frees the airbases with long TO strips for escorts.

 

[Engineman]

Hi,
There is no doubt that many parts of RAF Doctrine changed radically during WW2. It might be helpful for those without experience of this process to understand a little of the reality.
In many complex military Command structures, promotion of individual personalities can be enhanced by perceived "effective leadership". This includes success in battle and also success in new thinking and employment of resources and capabilities. Competing Officers will cause huge internal battles to support various doctrines that they see as advantageous to their promotion prospects. Of course, loyalty to the Service and it's declared doctrines is also important so, there is always great competition for being identified with either new doctrine that is adopted or, standing doctrine that works. Funnily enough, there is little to be lost backing new doctrine that is not adopted, as long as you rapidly support another proposal that might be good. However, supporting new doctrine that is adopted but fails, is the kiss of death for an aspiring Air Marshal!
It might seem that things like new aircraft types, weapons and resources give rise to new doctrine, but this is not always so. Often, senior Officers are made aware of possible new technical or scientific advances that may require a new doctrine for effective use. IMO, this is the usual way weaponry and doctrine advances. The Service has to become aware of a possible new "thing" or a way of doing something better for a new doctrine to be formulated and supported at a high level. But, if the old doctrine has not been totally discredited, support for the new doctrine will not be universal and resistance will occur. In this way, really far-sighted improvements are unlikely to get much support. However, even good improvements always have a hard time against change, until it is obvious that change is needed and everything is a bit late!
Unfortunately, some good changes don't get much support and fail, some bad changes get support and the wrong people get promoted!

Eng

 

[drgondog]

So a Spitfire with over 200G of internal fuel plus a 90G drop tank can only get to Paris from say Biggin Hill, about 280 miles???

That load out would go past Paris. So, the question is two fold> 1.) what was loadout for Spit IX tasked by RAF to escort 8th AF in 1942? and 2.) if different, when did the Spit IX go operational with that configuration, for what mission?

 

[tomo pauk]

Spitfire I & IIs could not carry a significant amount (40imp gal ?) of internal fuel without a performance penalty.

Penalty for RoC - not to worry too much, since the escorts are already in a decent altitude and speed, not at zero altitude and speed.
Penalty for speed - how much, Mk.I or II with 80-90 gals vs. the same A/C with 40 gals?

Maybe they could have figured out how hang a droppable 45-60 gal tank for climb and cross over to Holland so they would enter combat with most of their 87 gallons available for combat and the trip home but that is about all.

They would've figured it out to attach drop tanks if it was ordered so from the AM/RAF, just like the other people figured it out years before ww2 started.
No doctrine = no orders.

All the doctrine in the world cannot over come physics. Or physical plant. You need the engines/props/aerodynamics to come together with proper sized airfields (and fuel supplies and training/equipment) to support/enable the doctrine.

Physics was there to be taken advantage of.
Engines - check. Props - check. Aerodynamics - check. Airfileds - check; if not, make them bigger. Fuel - UK is no Germany or Japan.
Training - no doctrine = no check.
All the physics of the world is of no use for a military if there is no push towards it. Again, doctrine mattered.

 

[Shortround6]

Penalty for RoC - not to worry too much, since the escorts are already in a decent altitude and speed, not at zero altitude and speed.
Penalty for speed - how much, Mk.I or II with 80-90 gals vs. the same A/C with 40 gals?

I am not worried about the time to 20,000ft.
What I am worried about is that rate of climb shows surplus power to weight available for not only vertical maneuvering at altitude but horizontal maneuvering.
Spitfire Is and 109Es could not turn at more than 2.5 to 3.0 Gs under best circumstances (best speed, best turn radius, best altitude) without loosing altitude.
Spitfire II with under wing fuel tank took 3 minutes to go from 15,000ft to 20,000ft. Without the tank in it took 2 minutes. That is at best climb speed.
The Spitfire with the extra fuel will turn just about as tight as the one without, it is just going to loose more altitude doing it.

As far as climbing from ground goes, it is about 100-115 miles from the Dutch coast to the German border. Crossing the coast at Belgium is a bit longer. Germans with telephones have at least as much warning time once Germany takes the low countries as Britain had with radar. It is another 20-40 miles from the border to the actual industrial areas.
Counting on the Germans always being at lower altitudes may not work that well.

They would've figured it out to attach drop tanks if it was ordered so from the AM/RAF, just like the other people figured it out years before ww2 started.
No doctrine = no orders.

Let's see

Engines - check.

Engines-check
no check in 1939. You cannot publish a doctrine statement and get Merlins to go from 880hp take-off to 1050-1200hp for take-off just because you want them to.
You need to develop the engines and the fuel that allows them to do it. It took a number of years to do both, at the same time.

Props - check.

Props-check.
A 1/2 check. Britain needed to make the jump to better propellers much earlier than it did. Which means more/different propeller factories. May also mean license fees. May also require concrete for factories you can't use for hard runways. Very few of the really bad British aircraft used the best propellers.

Airfileds - check; if not, make them bigger.

You also need more. Most of the WW I airfields had been sold in the 1920s and at the very least, been used for farmland, at worst they had buildings on them.
And you have competing uses. Historic Fighter command bases to defend London and the mid section from an arc from the north east to south or southwest, they were extending the ends in the late 30s. Then you have local defense, like, but not limited to, Southampton/Portsmouth. and you have the bomber bases. Without bomber bases you have not doctrine.
Jan 1st 1935 the RAF had 15 bomber squadrons (8 with Harts or Fairey Gordons) at 9 bases/airfields.
2 squadrons had these,

as the highest performing heavy bomber the British had and was only part way through it's production run.
Bomber Command would only be officially established in the middle of 1936 and obviously had a lot of work to do.

There were a large bunch of bomber squadrons overseas.
There were also 13 Auxiliary air force bombing squadrons with 10 bases scattered around from Northern Ireland to nearly Scotland and southern England which would keep them out of harms way for training, not very good for mounting a bomber offensive from.

Jan 1st 1938 saw 57 RAF bomber squadrons and 11 Aux Air force bomber squadrons. Buildup was underway, unfortunately for impending combat (Czech crises) 32 of those squadrons had Hawker Harts/Hinds and none had Wellingtons or Hampdens. Bomber Command still needed to grow/develop more.
But they did have the training structure/infrastructure well underway.

Now try to figure out your doctrine with what was possible vs what was desired?

USAAF at this time "wanted" bombers with pressure cabins, turbo-charged engines laying flat inside the wings with just prop-shafts sticking out and either self defending or flying too high for any enemy to intercept and using advanced bomb sights. That was their doctrine. Took until 1944 to even get 1/2 of what they wanted.

Edit, I would note that BC had to develop several sort of overlapping doctrines. If they aimed too far into the future (1942 goal/s in 1936) they would be caught short if a war started in 1938. If they tried to build up for maximum force in 1938 from 1936 they would be stuck with lots and lots of crappy airplanes (and short fields) in 1940.
Now you do NOT have unlimited money/resources no matter which path you take.
Army got short changed enough in the late 30s.

 

[tomo pauk]

Engines-check
no check in 1939. You cannot publish a doctrine statement and get Merlins to go from 880hp take-off to 1050-1200hp for take-off just because you want them to.
You need to develop the engines and the fuel that allows them to do it. It took a number of years to do both, at the same time.

Definitely check. Merlin III paired with a 2-picth prop was powerful enough to propel the 5 ton Battle in the air from the ground, it will be powerful enough to propel a 3.5 ton LR Spitfire.
I don't need to want the Merlin X to make another 200 HP for take off, it was already there, on 87 oct fuel.

Props-check.
A 1/2 check. Britain needed to make the jump to better propellers much earlier than it did. Which means more/different propeller factories. May also mean license fees. May also require concrete for factories you can't use for hard runways. Very few of the really bad British aircraft used the best propellers.

Quick fix is to not make Henleys, this is 200 good props + 200 Merlins to help out here.
Mid-tem fix is to fixate on better bomb trucks - less Battles and Blenheims, more Wellingtons and Hampdens - saves both on propellers and Merlins (and pilots). No Botha = more than 1100 good propellers not needed there. No Defiant = 1000 more of good props and Merlins.

 

[Shortround6]

. Merlin III paired with a 2-picth prop was powerful enough to propel the 5 ton Battle in the air from the ground, it will be powerful enough to propel a 3.5 ton LR Spitfire.

Battle used it's 422 sq ft wing to help get into the air.

Mid-tem fix is to fixate on better bomb trucks - less Battles and Blenheims, more Wellingtons and Hampdens - saves both on propellers and Merlins (and pilots). No Botha = more than 1100 good propellers not needed there. No Defiant = 1000 more of good props and Merlins.

We have to check the props. A lot of those planes used 2 pitch props not constant speed.
And for twin engine planes you really want fully feathering props, not just constant speed. Having the prop go to max pitch with a defect or dead engine is still a big drag and often a plane down in either water or land.
And unfortunately the Botha and Defiant don't help at all in 1939 and not as much as we think in 1940.
Botha Production in 1939 16, Botha production in 1940 was 320. Leaves 244 built in 1941 and 1942.
Defiants were even later in timing.

 

[z42]

To answer the original question that started the thread, the Spitfire except with some modest design changes to accommodate more internal fuel. Britain had her hands full, and designing yet another fighter type would have distracted from other efforts. So if the original Air Ministry specifications that lead to the Spitfire would have otherwise been mostly identical, but specified longer range/endurance on internal fuel, what could have been done? Or if the design team had decided to aim for longer range just because they could and thought it would be useful?

First is where to place the extra fuel. Obviously, for balance reasons they must be placed somewhere relatively close to the CoG. There are already the historical 85 imperial gallon fuel tanks between the cockpit and the engine, so the remaining volume where they could be placed are the wings. The PR Spitfires apparently had a massive extra 132 imp. gallons in the leading edge of the wings, I'm not sure how far outwards these wing tanks reached, but for the fighter version they obviously can't get in the way of the guns, so they would have to be roughly within the prop arc. Another thing taking up a lot of space in the wings are the radiators. So move the radiators into the P-51 location behind the cockpit, giving the additional advantage of having more space for the ducting; not saying this would have been as good as the P-51 radiator, that was a half a decade newer design based on a lot of wind tunnel testing, but still, should be possible to be better than what the Spit had historically. And crucially for this thread, allowing to put additional fuel tanks into the wings reasonably close to the CoG.

So now we have a plane with the historical Spitfire fuselage tanks, plus wing leading edge tanks and "middle wing" tanks. Might not give the range of the P-51 since the wings are much thinner and the airframe is draggier, but still, should be a substantial improvement on the historical Spitfire.

Now, I do wonder what the required runway length for a takeoff with a full fuel load and the fixed pitch prop and early Merlin of the early variants would have been. If this would have been excessive, maybe sacrifice the lower fuselage tank and make the upper one smaller, moving the cockpit forward so the pedals are directly behind the engine firewall, improving forward visibility.

 

[PAT303]

That load out would go past Paris. So, the question is two fold> 1.) what was loadout for Spit IX tasked by RAF to escort 8th AF in 1942? and 2.) if different, when did the Spit IX go operational with that configuration, for what mission?

Been over this countless times, aux and drop tanks were available from before the war, MkV's VII VIII plus late MkIX's and all MkXVI's had them and many others, even the prototype had water tanks for the evaporative cooling in the wings, this is a what if thread, the RAF had all the ingredience for a LR Spitfire once the MkIII arrived.

 

[PAT303]

I'm not sure how far outwards these wing tanks reached, but for the fighter version they obviously can't get in the way of the guns,

People don't read, there's enough room for 60G inboard of the guns, I even posted an image.

 

[z42]

The PR Spitfires apparently had a massive extra 132 imp. gallons in the leading edge of the wings, I'm not sure how far outwards these wing tanks reached, but for the fighter version they obviously can't get in the way of the guns, so they would have to be roughly within the prop arc.

Spelunking on the interwebs, it seems the Spitfire C and E type "universal" wings were fitted with 13 IG leading edge fuel tanks, so 26 IG total. A bit disappointing compared to the massive 132 IG the PR Spits got, but we'll take it. Still a 30% increase over the original fuselage tanks only.

I don't know how big the wing fuel tanks could be after moving the radiator under the fuselage. Certainly not the massive 90 USG the Mustang got, as the wing is thinner and the wheel well takes up space. But even if we ballpark it at 30 IG, that would give a total of 2*(30+13) = 86 IG, which coincidentally is the same as the fuselage tanks. So double the fuel capacity. Not too shabby.

 

[z42]

People don't read, there's enough room for 60G inboard of the guns, I even posted an image.

So why did they add only 13IG leading edge tanks on the C and E wings, if 60IG's would have been possible? Edit: Or did you mean 60IG total, so 30IG per wing? Still, the question stands, why didn't they do it for the C and E wings?

 

[PAT303]

So why did they add only 13IG leading edge tanks on the C and E wings, if 60IG's would have been possible? Edit: Or did you mean 60IG total, so 30IG per wing? Still, the question stands, why didn't they do it for the C and E wings?

This is the whole question, they knew the Spit had everything but range yet did nothing to add internal fuel until late in the war.

 

[EwenS]

I've been looking at the various drawings in "Spitfire the History" by Morgan & Shacklady.

The leading edge tanks in the Spitfire VII ran between wing ribs 4 & 7, with the noses of ribs 5 & 6 removed and the wing skins thickened to compensate. The cannon bay is immediately outboard of rib 7. Those tanks held about 13.5 Imp Gals each side for a total of 27.

Go back to the PR wing fitted from the PR.IV it is noted as having 66 Imp Gal capacity (or 66.5 gal) each side for a total of 132-133 gals. But it runs between ribs 4 & 21 as clearly noted on the drawing on p243 which also clearly shows the main feed connections on the inboard sides of rib 4. This was the same wing tank layout as was used on the PR.X/XI/XIX.

So the space between ribs 1 & 4 was not used for fuel tankage on any Spitfire variant so far as I can see. One thing that does possible intrude into that space is the undercarriage mounting which would attach to the rear of the wing spar.

 

[NevadaK]

This is the whole question, they knew the Spit had everything but range yet did nothing to add internal fuel until late in the war.

Two likely answers:

1) it was deemed not needed by RAF until later in the war.
2) the impact on performance was deemed as unacceptable.

My feeling is a combination of the two.

 

[PAT303]

Two likely answers:

1) it was deemed not needed by RAF until later in the war.
2) the impact on performance was deemed as unacceptable.

My feeling is a combination of the two.

What performance?, no fighter goes to war with full aux and drop tanks, with the drop tank released the Spitfire with full main tank, full lower rear tank flew just like a normal Spitfire.

 

[PAT303]

I've been looking at the various drawings in "Spitfire the History" by Morgan & Shacklady.

The leading edge tanks in the Spitfire VII ran between wing ribs 4 & 7, with the noses of ribs 5 & 6 removed and the wing skins thickened to compensate. The cannon bay is immediately outboard of rib 7. Those tanks held about 13.5 Imp Gals each side for a total of 27.

Go back to the PR wing fitted from the PR.IV it is noted as having 66 Imp Gal capacity (or 66.5 gal) each side for a total of 132-133 gals. But it runs between ribs 4 & 21 as clearly noted on the drawing on p243 which also clearly shows the main feed connections on the inboard sides of rib 4. This was the same wing tank layout as was used on the PR.X/XI/XIX.

So the space between ribs 1 & 4 was not used for fuel tankage on any Spitfire variant so far as I can see. One thing that does possible intrude into that space is the undercarriage mounting which would attach to the rear of the wing spar.

Just because the space wasn't used doesn't mean in couldn't be used, this is a what if thread, they got 18G per side using bladders, look at the drawing, there's more empty space left than what the actual tank takes up.

 

[NevadaK]

What performance?, no fighter goes to war with full aux and drop tanks, with the drop tank released the Spitfire with full main tank, full lower rear tank flew just like a normal Spitfire.

Color me skeptical when every other fighter with added fuel capacity does suffer some degradation in performance. Added weight affects climb and added weight in the wings affects rate of roll.

 

[z42]

Color me skeptical when every other fighter with added fuel capacity does suffer some degradation in performance. Added weight affects climb and added weight in the wings affects rate of roll.

Just because you have capacity for more fuel doesn't mean that you always need to top up all the tanks. I'd imagine for interceptor style missions the wing tanks would be left empty. And for aircraft entirely dedicated to the interceptor mission, like during the BoB, I imagine airfield mechanics could even remove the wing tanks for a small weight reduction. Or even not bothering to install them at the factory, such that wing tank kits could be manufactured later and delivered to the squadrons as the RAF adopts a more offensive posture post-BoB.

Further, with my suggestion above to move the radiators to the centerline, the roll rate should slightly improve compared to the historical Spitfire (as long as the wing tanks are empty, of course).

 

[PAT303]

Color me skeptical when every other fighter with added fuel capacity does suffer some degradation in performance. Added weight affects climb and added weight in the wings affects rate of roll.

Absolutely thats why the loss of performance is a stupid reason not to add tanks because the fuel is gone before the fight starts.