1937-45: Doubling down on the 2-engined 'day fighters' (5 Viewers)

Everyone and his brother knows that I'm not a fan of 2-engined day fighters for the period of interest (mostly because their advantages were often short-lived - if not dubious - while representing a big drain on the resources), so this is me playing the devil's advocate: making the case for the beligerents to make even more of them. Whether by making a lot more of historical examples, or producing the alternative designs (these can be either the designs that became eventually stillborn, or something else that is plausible for a nation/company to make).
I have no quarrels that twins later make a name for themselves as recons, NFs, ground attakc aircraft etc, but the 1st rand foremost role is that of the day fighter.
Note that something else will need to be axed, with the benefit of hindsight.

For example, Gloster makes the F.9/37 around the Merlins (note that I'm not talking about the later 'Rapier' design) from the get go, for the role of the heavily armed bomber-buster; being halfway house between the Whirly (fine, but without much of the 'stretch') and Beaufighter (good in many roles, but lets keep it away from the enemy's best fighters), it might do well as a day fighter. I'm willing to sacrifice the Defiant and the whole turret fighter idea in order to get the ball started.

If we swapped out all (or some) the Spitfires and Hurricanes in 1939-40 with something equal to the P-38G of 1943, then sure. There's nothing inherently wrong with twin-engined fighters, provided they keep or exceed the power-to-weight ratio, high wing loading, top speed and rate of climb of the opposing single-engined fighters. Any deficits in low speed agility should be made up with advantages in top speed and heavier armament.



The Mk.2 Spitfire of 1939-40 had a 1,175 horsepower Merlin XII engine. So, let's put two of these into a single-seat P-38 equivalent, with the best British superchargers then available. As it was, we did not see the British put two Merlins into an operational single-seat fighter until the postwar DH Hornet. I'd stay away from the Westland Welkin high altitude interceptor concept - we need the ability to mix with Bf 109s and Fw 190s. Maybe we should start here:


View: https://www.youtube.com/watch?v=F2tOq0qmNXI

Yes, actually when we count then P-38, Whirlwind, Fw 189V1 and F5F are the only pure (one crew) fighters, either interceptors or long range.

The Bf 110 is a Zerstörer, a concept in which Willy 'cheated' because he did not include a bomb bay, so instead of a multirole, he became a fighter, but I would say at least 1/4 too big for that role. Its successor, the Me 210, was supposed to be a replacement for a long-range fighter, but also for a Ju 87, so it certainly wasn't a pure fighter (but at least it had a bomb bay like a real Zerstörer)
All the others - and I will include the French Potez 630, the Polish Wilk, the American F5F, the Yugoslav Zmaj R-1, the Dutch Fokker DXXI, the Russian Moskalev, and I'm sure I've forgotten some of them, were with (too) weak engines. I would say that instead of a premium engine, they went for a number (to be competitive with single engines fighters powers). And here I agree with Admiral Beez. The problem is that with two smaller (weaker) engines, you can't get a small and light enough construction to compete with premium single engined fighters (especially if you add another crew member). Although the British almost succeeded with the Whirlwind (and maybe the FW 189 would have if it had not become a two-seater and had received a DB 601 or at least a Jumo 211). Only with the first engine league do we get to the F7F, P-61 and Hornet.

You mean Fokker D.XXIII - it was a push pull.

Admiral Beez said:

If we swapped out all (or some) the Spitfires and Hurricanes in 1939-40 with something equal to the P-38G of 1943, then sure. There's nothing inherently wrong with twin-engined fighters, provided they keep or exceed the power-to-weight ratio, high wing loading, top speed and rate of climb of the opposing single-engined fighters. Any deficits in low speed agility should be made up with advantages in top speed and heavier armament.

View attachment 796230

The Mk.2 Spitfire of 1939-40 had a 1,175 horsepower Merlin XII engine. So, let's put two of these into a single-seat P-38 equivalent, with the best British superchargers then available. As it was, we did not see the British put two Merlins into an operational single-seat fighter until the postwar DH Hornet. I'd stay away from the Westland Welkin high altitude interceptor concept - we need the ability to mix with Bf 109s and Fw 190s. Maybe we should start here:


View: https://www.youtube.com/watch?v=F2tOq0qmNXI%5B/URL

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twice as many engines required with associated maintenance necessary for what benefits?

Uh, clumsy fingers, yes of course push-pull D XIII.

Benefits of a pure twin-engine fighter - well, for the class with the currently strongest available engines (Merlin, DB 601/5, Allison V-1710 ect) heavier weapons (and more ammunition) as a rule at a significantly larger operating radius is certainly a justified reason. Not that, say, benefits of the FW 189 wasn't discussed in several threads.

And let's not get into the discussion now about the P-51B/D and P-47N we know when they appeared (late) and there weren't enough strong engines for them earlier anyway.

Another solution is the "type" Whirlwind, i.e. a very small airframe just enough for second class of engine. Benefits - for practically the same area of the wing, approx. 40% hp more you have approximately the same performance ( vs Spitfire I) and significantly stronger armament 4x20 vs 8x7.7, and the use of engines that are not needed elsewhere.
This type would be interesting for the big players to take advantage of the production capacity of engines that are not in the first league. (the problem with Whirlwind was that there was no well-established production, although RR could have transferred the tools or even the production line of the older kestrel to a smaller manufacturer?). The F5F/P-50 had a problem with the R-1535 (which Pratt & Whitney is putting out of production).
This type of small two-engined aircraft could also be interesting for small players, but they all went for "multirole" two-seaters, and for that, as a rule, they were equipped with rather weak engines or oversized constructions (like the Fokker G I).
Admittedly, it would be nice to see what performance the refined single-seat variants of the PZL.48 Lampart or Bre 690 would have.

The Westland Whirlwind gives a good model for the high power twin single seat fighter. With the Peregrine you were using a better Kestrel which was a known success already. With the Merlin, at the time of design, you were looking at a private venture engine of unknown quality. With the Peregrine you got a 1,00bhp fighter in 1940, with a developed Peregrine you would be getting a 2,000bhp fighter in 1942, with early Merlin's the same but in 1941 and with later Merlins 3,000bhp in 1943 and 4,000 in 1945. Compared to the OTL big engines you use no more cylinders and less complexity. With the economies of scale of Merlin production and the AH production and design resources used IOTL for the Vulture and Sabre it would probably be cheaper and easier to use twin Merlins and certainly easier to maintain and familiar to more mechanics.

There is a whole deep well appointed and centrally heated/air conditioned rabbit hole to be gone down in the whole Whirlwind 'what if' which I am not going down in this post.

tomo pauk said:

I'm willing to sacrifice the Defiant and the whole turret fighter idea in order to get the ball started.

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But you can't get rid of the turret fighter!!!
Without Defiants you have no replacement for the
HAWKER DEMON


Obviously a 182mph two seat fighter is vastly superior to a 220mph single seat fighter using the same engine so the formula should be repeated with the new 1000hp engine.

Back on point. the twin engine single seat fighter has a rather narrow niche or perhaps two paths. 2 small engines to keep cost down (but still more expensive than a single engine fighter) or using two full size engines for an expensive but very capable airplane. But if you can only afford say 60% of them compared to single engine fighters using the same engines?

British used somewhat crappy accounting on the Whirlwind. They should not have been comparing it to the Spitfire but rather to the Hawker Tornado/Typhoon. Granted there were overlaps or differences in timing, much like the Americans with the F5F program and the F4U program.

The small twin works (?) when compared to the next generation big engine, not the current generation big engine. And it you are bit too small then the whole thing falls apart.

Beaufighter is another side track. Not quite what was wanted but rather what they thought they could get fast. And the promised performance was thwarted by faulty wind tunnel data, the promised 370mph speed would have needed rockets. But it could be built using some Beaufort tooling for early delivery.................except the promised Hercules engines weren't showing up in time.

re

yulzari said:

There is a whole deep well appointed and centrally heated/air conditioned rabbit hole to be gone down in the whole Whirlwind 'what if' which I am not going down in this post.

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Good one! I am going to (unashamedly) steal this phrase and figure out how to occasionally intersperse it among my explanations to my friends as to why I am researching certain seemingly strange (to them) subjects that somehow allows tracing of important information to some other subject that they have an interest in.