WI: Twin Spitfire?

Premise of the thread: instead of the OTL Type 327, the twin engined fighter, Supermarine tries with a twinned Spitfire. 4 cannons in the inner wing (that is of constant chord), outer wing panels house fuel tanks. U/C is of stronger type than in the Spitfire.
Second crew member acts as radio-man, watches the 6 o'clock position, has the basic pilot training in order to bring the aircraft home in case other pilot is incapacitated through enemy fire.
What does the RAF gain, what is lost in ballance, what kind of capability and performance for initial and developed models can we expect?

dubleSpit.jpg
 
Should have removed the cannon breech bulges from below the outer wings where there ain't no cannon. Since the radio operator doesn't have any better view of the six-o'clock position than the pilot, I suggest installing a 4-gun turret in that location.
 
The manoeuvrability will suffer in roll rate at the least . Performance will not improve by much at all and firepower will not be improved either . Their is no driver to make this happen . The Twin Mustang was introduced to create a long range escort fighter with 2 pilots as easily as possible and by some miracle actually worked .
 
Just a side thought but,

Would such an arraignment have made the Boulton Paul Defiant any better? With the turret on the 'outboard' hull ind of thing?
 
there were several proposals and even some were build
i stick on single seat fighter bolded together who got build
So if that concept worked, why not as Spitfire Twin ?

Bf 109Z "Zwilling"
four variants were proposed
1. Interceptor armed with five 30 mm cannons and one 1,000 kg (2,200 lb) bomb load
2. Fighter-bomber armed with two MK 108 cannons and up to two 2,200 lb. bombs.
those had to be powered by two DB605 engines, the two other were same but with Jumo 213 engines.
all version had one pilot, who flew the aircraft from the left side fuselage
only one prototype was build

F-82 Twin Mustang
designed as a long-range escort fighter in World War II, it was first used in Korea War
they were quite good in there job, until jet fighter were use in Korea.
Two pilots
Guns: 6 × .50 in (12.7 mm) Browning M3 machine guns
Rockets: 25 × 5 in (127 mm) rockets
Bombs: 4,000 lb (1,800 kg)

Here as fighter with Gun pod increase the numbers to 14 guns and also ten rockets under wings
BI25750.jpg
 
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Should have removed the cannon breech bulges from below the outer wings where there ain't no cannon. Since the radio operator doesn't have any better view of the six-o'clock position than the pilot, I suggest installing a 4-gun turret in that location.

Indeed, the bulge is redundant here :)
The premise is that, once pilot is about to engage a target, the other crew member will be looking out so no-one will be sneaking in the rear hemisphere. Hopofully Malcolm hood would've improved the field of vision.
OTOH, the turret idea is cool.

The manoeuvrability will suffer in roll rate at the least . Performance will not improve by much at all and firepower will not be improved either . Their is no driver to make this happen . The Twin Mustang was introduced to create a long range escort fighter with 2 pilots as easily as possible and by some miracle actually worked .

Yes, the ailerons need to be greater in order to keep the rate of roll acceptable.
The Twin Spitfire should be smaller than Mosquito, especially it's wing area (350-370 sq ft? vs 454). with one of the thinnest wings of ww2. Each engine propells two cannons, so the rate of climb should be good.
The Spitfire Mk.VC (4 cannons) was sluggishwhen copared with 2-cannon variant, let alone he 8-Browning variant. The earlier marks won't mix well with 4 cannons either. Basically - 4 cannon firepower + performance even on early Merlins.
Drivers for this to happen: same as for Whirlwind, Typhoon, Beaufighter, Type 327 - excellent firepower, combined with excellent performance. IIRC, Hawker was expecting 460 (!) mph for Typhoon, similar for the Type 327, Bristol expected 370 mph for the Beaufighter.
The Twin Mustang used no miracle in order to work. Usually hard & smart work is/was behind success, like what we saw with Spitfire, Fw 190, Mosquito etc.
 
Yes, the ailerons need to be greater in order to keep the rate of roll acceptable.

The solution to rate of roll, particularly at high speed, wasn't greater ailerons, since the wing structure lent itself to aileron reversal. Fortunately, since the "Twin Spitfire" outer wings don't contain the armament, the specific semi-elliptical wing planform isn't required for use on a twin, and the specific structure required will no longer be required. However, that said, that which made it a Spitfire will no longer be needed, and it won't be a Twin Spitfire at all. Since Mitchell will be dead, Joe Smith will make a botch of the job. Nobody will notice, since the plans and mock-ups will be destroyed by German bombing of the Woolston Works.
 
Despite the naysayers in the Air Ministry, Spermarine beat the Hawker and Bristol in developing a 'new' fighter, the 1st flight taking place on 4th February 1940. With two Merlin III engines, it easily beat the 370 mph mark, in combat trim, while out-climbing the in-service Spitfire I.
With RR mumbling about the cancellation of Peregrine, AM reluctantly awarded the contract to Westland (along with Supermarine) while production of Whirlwind fighters will not be carried on beyond 120 examples.
 
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The handful of Twin Spitfires engaged in the BoB gave impetus to both RAF and LW to do some measures.
RAF went to order the T.S. outfitted with Merlin XX engines, and nobody was surprised that prototype beat 390 mph mark easily. Unfortunately, Merlin XX was earmarked for bombers and Hurricane (to cut the advantage held by Bf 109E), so next in-service Twins were powered by Merlin XII. Little bit of extra power ony covered the extra drag & weight penalties of the bullet proof glass and other protection installed. The ammo loadout was insufficient, belt feed for the cannons was seen as priority; firepower was making short work of any LW aircraft hit.
Luckily, the Merlin 45 was in the pipeline, and the pair of those was quickly installed in the Twin, again the prototype managed to do 390 mph.
The RAF was dissapointed with performance of the Beaufighter prototypes, that barely achieved 320 mph when armed. They liked that another crew member could replace the empty drums with the full ones, while the fuel load was also acclaimed. Typhoon was a far better performer than Beau, while outperforming the Twin with Merlin XX engines. Problem - the mass production of the Typhoon will not be as easy as of the Twin, the Typhoon being a whole new aircraft, with a whole new engine. So the RAF decided to go with both Twin and Typhoon for dalight ops, and the Beaufighter for night fighter job, the cavernous fuselage and generous wing being assets for the bomber buster outfitted with bulky electronics.

Messerschmitt was told to increase the work on the Me 210, so that LW could have a better twin-engined fighter than it was the Bf 110. With the Bf 109F coming in service, and Fw 190 receiveing a lot of priority, LW brass was of the opinion that 1941 will see LW fighter arm achieveing upper hand over anything the RAF will throw in.
 
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Looking at the Twin Spitfire for the 1st time, Petter immediately draw comparisons with Whirlwind. T.S. used engines in volume production, many parts of airframe are of course in volume production of course, the wing was of generous area and of thin profile. Two crew members meant extra pari of eyes on the lookout. The major shortcoming vs. Whirly was the placement of the radiators, Petter mumbled that 'Supermarine regarded the radiators to double as dive brakes'. So he set to install the radiators in front of the main spar of the inner wing, along with a redesigned wing-fuselage fairing. The flight tests revealed 10 mph increase vs. usual Twin Spitfire, but Air Ministry was not in the mood to have series prduction lowered, so Westland proceeded without the successful modification.

dubleSpit2.jpg
 
The generous fuel tankage on the Beaufighter was not lost on the Supermarine staff. Ditto for the experiments with AI radar sets on the tight Defiant. So they set themselves on killing two birds with one stone.
Extra fuel tankage was installed behind the main spar, boosting the total fuel tankage by another 2 x 50 gals. The drop tank facility was installed under both fuselages. While still not beating the Beaufighter, it was felt that such fuel tankage is a best compromise between increase of range and fall of rate of climb and rate of roll.
The AI set should be easier to install & use on the Twin Spitfire than it was on Defiant, and second crew member can use the set while not being distracted by flying the aircraft. Aerials were installed on the starboard fuselage Flame dampers were installed, the NF peculiarities bringing down the speed to just above 350 mph.
 
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