Twin Engine Fighters

[GregP]

We have had some interesting discussions about the various twins and I thought I'd start a twin thread to get some discussions going. So here's my candidate for a sleeper, the Mitsibushi Ki-83. In post-war testing in the USA, we got it up to 473 mph at 23,000 feet on US 150-grade fuel.

Looks like general winner to me. Designed by the same fellow who did the very good-looking Ki-46 Dinah, Tomio Kubo. Seems like he had a flair for pretty airplanes. With two 30 mm and two 20 mm cannons, it had about as hard a hitting power as any fighter of the war. But it was in the prototype stage with only four completed when the war ended. It's existence took us completely by surprise as we didn't even know about it. Post-war testing was an eye-opener.

Despite it not being all that successful, I also like the looks of the plucky Westland Whirlwind.

Any other twins you like out there?

 

[Milosh]

Why wasn't the Whirlwind all that successful?

 

[GregP]

I think we covered that already, but if not, it didn't stay in service long and it's combat success seems quite hard to document. Lack of information about it makes me think it didn't do all that well. It is possible it did but, if so, why is it so hard to find out about? It wasn't used by many squadrons because there weren't all that many Whirlwinds built ... 114 or 116 total, including 2 prototypes. That won't go very far equipping an Air Force.

I can find a few writeups of Whirlwind battles with a few probable kills, but not much in the way of a total of aerial victories for the type. I asked in the forum and nobody posted a total for Whirlwinds, probably because it is relatively unknown when compared with other British aircraft.

Everyone can find out about Lancasters, Mosquitoes, Siptfires, and Hurricanes, but data about the Whrlwind are scarce ... or seem that way to me.

If you have some information on it, Milosh, please post it! I, for one, would love to see more information about it. I'm sure others would, too.

I like the looks of the P-38 Lightning, too, but I see one every weekend and so generally look at other twins with more interest since I can satisfy my own curiosity about it anytime. If I want to, I can get up on it and get in the cockpit, with the permission of the owners, of course ... but I can't do that with, say, a Tigercat. We get a few in as visitors but I don't know the owners and don't climb on visiting aircraft. I can get pics, but that's about it.

What's your favorite twin fighter of WWII?

 

[Capt. Vick]

The post-war Hornet was a scorcher!

 

[GregP]

Another great choice. The Hornet certainly was another very good-looking fighter.

I can't help but wonder at how the last generation of piston fighters would have stacked up against one another, had they ever met in combat. Another of my favorite obscure types was the FMA I.Ae.30 Namcu.

Alas, they only built one, and that was in 1950, but it was firmly rooted in WWII design. It used a pair of Merlin 604's. It clocks in at 460 mph and is decidedly better looking than the FMA Calquin that was still flying with the Argentinian Air Force at the time.

Another potentially great idea that never came to pass was the Grokhovsky G-38 with a pair of Gnome-Rhones. It had the same problem as the Whirlwind ... a pair of 900 HP engines,

Can't find any proof they ever made one, but it looks like a neat idea. I think it is a fantasy plane that some modeler dreamed up, but it could have been a design that was simply never built. I like the concept but then reality sets in and I know it wouldn't have had much potential for growth having been designed for a pair of Gnome-Rhones.

 

[kool kitty89]

I believe the Whirlwind was the second smallest (if not lightest) of the twin engine fighters that made their maiden flights prior to the start of WWII and the smallest to see frontline service of any sort. The PZL.38 was smaller but never saw production and development halted with the fall of Poland. The Fw 187 is interesting, but the few A-0 aircraft didn't see significant enough action to really comment on and even then the information is sparse and questionable. (and that would be for the 2-seat 700 ps Jumo 210G powered version which did at least manage to outrun and outclimb the Bf 109E up to the 210's critical altitude around 3600 m)

The roll rates (especially initial roll response/acceleration) would be one of the defining characteristics of a really good twin engine fighter and the one area that it could otherwise fall behind single engine contemporaries. Those outboard engines add a lot of weight, so overcoming that limitation takes strong wings and effective ailerons while minimizing adding yet more weight. The Whirlwind and (with less detailed information) Fw 187 seemed to both have good roll response as did Gloster's F.9/37 (which was noted by test pilots for having all around good handling), but it's the Whirlwind that has more specific remarks on its good initial roll response.

With the Spitfire and (especially) Hurricane having problems with heavy or completely static ailerons at high speeds (or not so high speeds with the early fabric covered ailerons), the Whirlwind's good aileron response was very significant. The same was true for most American fighters which could usually out-roll Spitfires, including the much larger P-47 which was noted for having excellent roll response all around but especially at high speeds. (it couldn't out-turn the spitfire, but it could reverse a turn fast enough to out-maneuver it) The Bf 109 was noted for having sluggish control at high speeds, so it wouldn't be too hard for the Fw 187 to beat it there too.

The P-38 had much more serious problems with roll rate and that was its primary limiting factor in dogfighting early-war (the nose-down pitch in terminal dives was a serious problem but not one generally related to slower maneuvering centric situations). This problem wasn't resolved until hydraulically boosted ailerons were installed on the P-38J. The airframe was strong enough and ailerons aerodynamically capable of pulling off harder rolls, but the flight controls lacked the mechanical advantage to allow it. (using a flight stick instead of a yolk might have helped somewhat, but the better 1930s era technology solution would be using spring tabs or 'boost tabs' on the ailerons -the F4U did that, resulting in very light and effective ailerons) The problematic roll rate might have been a contributing factor for the diving problems on the P-38 as well, as diving would be one of the limited options for escaping or evading an opponent in a dogfight where the P-47 could use its roll rate AND diving effectively. (poor roll control would also limit some dive recovery techniques like rolling sideways to prevent further nose-down pitch and start bleeding off airspeed in a controlled, high speed banked turn -it's notable that the P-38's elevator was still effective at those high speeds, but supersonic flow over some portions of the wing cause a shift in lift forcing nose-down pitch, thus you could potentially still have control on the vertical axis if you rolled onto your side, taking gravity out of the equation for elevator control and putting it on rudder control while also turning, but overstressing the airframe with cross controlling would still be a consideration too -you could also roll inverted and recover upside down, but almost certainly red out in the process from high negative G)



As to favorite, I'm honestly not sure I could pick one. On Aesthetics it might be the P-38 but the Fw 187 has that sleek nose and canopy (especially on the single seat prototypes). The whirlwind is neat, but it's got more angles I don't like the appearance that much. (P-38 wins hands down viewed from above or below)

But as overall aircraft, I think the Whirlwind could have been the best twin-engine dogfighter of the war (and probably was back in 1942) and the P-38 makes a better all-around multi-role fighter, fighter bomber, and even radar equipped night fighter.


There's certainly some others I'm omitting like the Beaufighter, A few Japanese heavy fighters, Fokker G.I, several German prototypes, Bf 110, 210, and 410, Fighter models of the Mosquito, and more, but as far as the real twins capable of acting in the roles of single-engine fighters and were flying at the beginning of the war, it'd be those top 3. (boost the P-38's ailerons and overboost the engines a bit and the P-38E and F would have made good low to medium altitude fighters ... above 20,000 ft in the ETO would be a real problem due to poor cockpit heating and greater problems with diving -cold air has a lower speed of sound and high altitude air is thinner meaning faster dive acceleration so a perfect storm for the P-38) In the 10-15k ft range, with a bit of engine 'abuse' it should have been one of the best performing fighters in the world at the time, fix the aileron problems and it'd be one of the best maneuvering as well. (like most American fighters, it had much better high speed controls than British, German, or Japanese fighters of the time) At USAAF heavy bomber altitudes, it was a poor match for the ETO until the P-38J finally solved cockpit heating and added dive recovery flaps. (P-47C was the best by far at 25-30k ft in 1942) The P-38 might be more useful for escorting RAF and USAAF medium altitude bombers, particularly B-25, B-26, and A-20s in daylight raids. (but those were used mostly in the PTO and MTO, where the P-38 performed best already)

 

[JimX]

Would spoilers instead of ailerons have helped the roll rate?

 

[GrauGeist]

It's probably no surprise that I would say the Ta154, Ar240 or the He219...

However, for the sake of fresh discussion, I would propose an often overlooked twin that held a great deal of promise: the RIKUGUN KI-93. The Ha-214 radials weren't delivering as much power as they had anticipated and this was being corrected. Before the problems could be worked out, the prototypes were destroyed in a B-29 raid.

There was also the Grumman XP-50/XF5F twin that was a real screamer. The XP-50 actually developed more speed than the Navy's version, but still looked like it was a winner.

 

[GrauGeist]

Now that I think about it, perhaps we should add Lockheed's XP-58 and McDonnell's XP-67, too!

 

[Greyman]

Potez 631

 

[GregP]

I really like the 2-seat "Destroyers" but they didn't fare well in combat. So I'm more drawn to the single-seat fighter twins.

But the Potez 631 was probably as good a 2-seater as there was except for being slow. Very similar to the Bf 110 in concept, which was a very pleasant aircraft to fly by all accounts. It did everything well except fly combat against single-seater fighters. The Potez had no excess power to speak of but by all accounts flew well.

Likely the Potez was similarly well-mannered in flight.

 

[kool kitty89]

Greg, that Grokhovsky G-38 looks kind of like a MiG-5 with the wing backwards, rear fuselage removed, and tail booms added behind the engines. The MiG 5 itself (or MiG DIS) is a neat twin engine fighter in its own right too, the cockpit and fuselage look a lot like the single-seat Fw 187 actually, but that wing is very distinctive and the engines obviously much larger. It looks nicer with the AM-37s than those ASh-82s. (I still say it would have made a really nice fighter-bomber with a pair of AM-38s instead)

Would be nicer with ejector exhaust stacks too. (nicer looking and probably a bit faster)

Actually, I think the MiG might be better looking on the whole than the Fw 187

 

[cherry blossom]

As my contribution, I did my research by my normal method of looking mostly at Wikipedia and made a list of aircraft ordered by their wing areas:

Westland Whirlwind 250 ft² (23.2 m²)
Focke-Wulf Fw 187 30.40 m² (327.22 ft²)
Lockheed P-38 327.5 ft² (30.43 m²)
Arado Ar 240 A 31.3 m² (337 sq ft)
Focke-Wulf Ta 154 31.40 m² (333.7 ft2)
Kawasaki Ki-45 32.0 m² (344 ft²)
Mitsubishi Ki-83 33.5 m² (361 ft²)
de Havilland Hornet 361 ft² (33.54 m²)
Arado Ar 440 35,00 m² 376.74 ft²
I.Ae. 30 Ñancú 35.32 m2 (380.2 sq ft)
Messerschmitt Me 410 36.20 m² (390 ft²)
North American F-82 408 ft² (37.90 m²)
Dornier Do 335 38.5 m² (414 ft²)
Messerschmitt Bf 110 38.8 m² (414 ft²)
Nakajima J1N 40 m² (430 sq ft)
de Havilland Mosquito 454 ft² (42.18 m²)
Grumman F7F Tigercat 455 ft² (42.3 m²)
Heinkel He 219 44.4 m² (478 ft²)
Bristol Beaufighter 503 ft² (46,73 m²)
Junkers Ju 88 G-6 54.7 m² (587 ft²)
Yokosuka P1Y Ginga 55 m² (592 ft²)
Northrop P-61 Black Widow 662.36 ft² (61.53 m²)

 

[GregP]

Interesting Kool Kitty. The G-38 DOES look like a MiG-5 modification, but I think the wing would be quite a bit smaller if sized for two Gnome-Rhones.

I always DID like the single-seat Fw 187, but it didn't make production along with some other VERY interesting one-off aircraft. I saw one report years ago that the Ki-83 really surprised us with it's performance when we tested it, but I never did get any hard numbers except for high top speed. I didn't get rate of climb, ceiling, etc. ... just a report of 473 mph at altitude on US fuel. That's the same speed that Wiki quotes, and it a bit surprising to see that speed in Wiki.

Cherry Blossom, I'm wondering where you are headed with the list. Are you headed for Wing Loading, Power Loading, wing area versus the weight of engines installed? Or what? I'm curious as I have all these in a file except weight of the engines. I also have span loading.

 

[kool kitty89]

Cherry_Blossom, there's also the XF5F (and related XP-50) as well as Gloster's F.9/37, Mig 5 (DIS), the small PZL.38 and several others I'm forgetting at the moment.

Grumman XF5F 303.5 ft² (28.2 m²)
Gloster F.9/37 386 ft² (35.9 m²)
Mikoyan-Gurevich DIS 38.9 m2 (419 sq ft)
PZL.38 20.4 m2 (220 sq ft)

The XF5F has a shorter wingspan than the Whirlwind in spite of the larger area and was all around very similar in size. The originally planned engines were much more in the Peregrine's class too (R-1535 radials making 825 hp before development was discontinued to focus on other Pratt and Whitney designs) but those R-1820s it ended up using added several dozen feet of frontal area along with several hundred pounds added weight. (and larger propellers needing more clearance with longer landing gear, etc, etc) 44.13 inch diameter engines vs 54.25 inch. I'm not sure why they didn't go with R-1830s, still added weight but at least less gain in frontal area and the potential to adopt the high altitude 2-stage supercharged versions. (yet more weight, but in that case well worth it)

Still, the R-1535s would have given the lowest weight and best roll rate and should have been somewhat cheaper. A twin engine fighter also should have gotten hispanos into USN service more quickly given they could adopt pilot operated cocking mechanisms to clear stoppages as the P-38 did.

Putting those R-1820s on the XF5F seems a bit like sticking Bramo 323s on the Fw 187 or Pegasus engines on the Whirlwind.

I always DID loike the single-seat Fw 187, but it didn't make production along with some other VERY interesting one-off aircraft.

I'm not sure the single-seater would have been all that much more useful if any given the advantages of a dedicated radio operator at the outbreak of the war, especially for a long range high endurance aircraft. Lack of interest in adapting beyond the standard Zerstorer requirements were more the problem and lack of interest in developing it with the Bf 110's engines. (as it was it smoked the similarly engined Bf 110B and could out perfom the 110C and match the 109E at low level) The ability to re-load cannon drums was useful on the Bf 110, but if heavy armament had been the serious limitation, I doubt it would be difficult to rectify. (further modifications to allow cheek mounted MG FF blisters or mounting them in the lower nose - I think the 187A-0 had glazing under the fuselage there somewhat like the F2A, but eliminating that doesn't seem like a critical issue) To be a good interceptor it really should have had more than 4 LMGs and 2 60 round drum fed MG-FFs. (the later Fw 190 upgraded to 4 20 mm cannons as soon as it could and with the nose mounted armament, they could have more options for MG-FF and MG-FF/M without synchronization limits)

Still a dead end without Fw being allowed to plan for the DB 601 (or at least Jumo 211) as its primary engine and using those 210s expressly in the interim (just like the Bf 110B did).

 

[GregP]

Pretty much agreed, Kool Kitty. We could discuss it, but it has been and will continue to be the subject of much discussion for Luftofiles looking for any way to turn the war outcome around. I'm with you thinking it could have been very good ... but they didn't elect to develop it to be that way and then place it into production, so it's an interesting "might-have-been" at best.

The Bf 110 was a pleasant-flying plane, but wasn't an Fw 187 by any stretch of the imagination exceft for being faily close in speed in some configurations. With similar engines the Fw 187 was, I think, better by a significant margin. Still not sure it was enough of a margin to beat single-seat fighters or hold its own against same, but that's another thread we already did some time back.

Hi Graugeist,

The XP-87 ws a neat-looking bird let down by underperforming engines, but as a neat bird nontheless. Rather unique looking and not aesthetically unappealing.

Though I love the P-38, I'm not a fan of the XP-58 Chain Lightning for several reasons, but the thread is about YOUR favorites, not specifically mine. So, good addition. If they had fixed some of the technical issues it could have been a service aircraft ... though even as an Allison fan I am not fond of double V-12 engines in one gearcase ... too many oil leak and heat issues. That is ... leak a little oil in between the engine cases and the heat of the middle exhaust will almost certainly ignite it fairly quickly. Ask any early He 177 pilot or crewmember. Still, had the issues been worled out .... who knows. I understand it was a maintenance headache due to engine access and systems located near them, but that might be inaccurate hearsay. I haven't done my due dilligence on it yet since it didn't get into service.

Thanks for the growing list.

 

[Elmas]

Nakajima J1N1 Gekko

 

[dedalos]

No boubt, the Ki 83 is among the most beautiful aircraft EVER. And its spesifications are remarkable.
If the 473mph/23000ft speed figure is true then we speek about a unique aircraft. 473mph at 23000ft (note the relatively low altitude)on single stage RADIALS plus TWO CREW members is not met in ANY other aircraft of the period . The do 335 used in Line engines, so did the hornet(plus two stage superchargers) and both in their two Seat vertions were slower. The F7F even on single Seat achieved around 460mph and was heavier.

 

[cherry blossom]

...

Cherry Blossom, I'm wondering where you are headed with the list. Are you headed for Wing Loading, Power Loading, wing area versus the weight of engines installed? Or what? I'm curious as I have all these in a file except weight of the engines. I also have span loading.

I was trying to classify the various aircraft into families because for example, whilst a Ju 88 G-6 and a P-38 were effective combat aircraft in 1944, they were aimed at rather different roles.

The list brings together some interesting pairs such as the Fw 187 and the P-38 as well as your Ki-83 and Capt Vick's Hornet (and the much later I.Ae. 30 Ñancú), which have similar weights and power as well as similar wing areas and speeds. It looks as if de Havilland and Mitsubishi were almost following the same specification to produce two beautiful aircraft.

However, that alone may not have ensured the success of the designs as the contemporary Nakajima J5N1 Tenrai was a dismal failure for the IJN despite being roughly the same size. According to Green's old books "Test flights revealed that longitudinal stability was bad and the rudder proved ineffective at low air speeds. One of the prototypes crashed while under test." The Tenrai also failed to reach its required maximum speed.

Using only wing area and maximum speed, the Arado Ar 440 seems to group with the Ki-83 and the Hornet. However, it was significantly heavier and carried a two man crew and two remotely controlled barbettes. The Arado's high speed is a tribute to a low drag design and the use of nitrous oxide (GM 1).

Lastly we can add a few more aircraft to our list. For example, Fokker can offer us the D.XXIII with the smallest wing that I have yet found (18.5 m² or 199 sq ft). It would have been interesting had it been flown with two Merlins although it might have been too small for a fighter rather a racer. The Fokker G.I (38.30 m² or 412.26 ft²) by contrast is similar in size to the Bf 110.

Of the French designs, the Potez 631 has already been mentioned but the SNCASE SE 100 with a similar sized wing (33 m² or 355 ft²) had more power and a much better performance.

Italy also produced several aircraft. They started with the Whirlwind sized IMAM Ro.57, which had a performance much inferior to the Whirlwind. However, with the DB 601 engines the slightly larger IMAM Ro.58 produced a performance that would have been impressive if it had flown two years earlier. Meanwhile Savoia-Marchetti were designing the SM.91 and SM.92 which are the subject of a web page at Might Have Beens: Italian Twin-Engined Fighters, 1943.

 

[GregP]

The SNCASE SE 100 has perhaps the most bizarre landing gear of any aircraft on this group or probably most any other group as well.

View attachment 297437

As the model above shows, the "main" gear was located in the bottom of the vertical tail and the "nose" gear looks to be the more substantial of the group, but it probably touched down on the tail gear. I haven't seen a videp clip of it, so I can't be sure, but that seems likely. I bet there were some substantial shocks above that tail landing gear and some really formidable tail spars.

Most "conventional gear" planes have two forward wheel sna one tail wheel. If this one can be classified as conventional, it has one forward gear and two tail wheels ... wonder if they were both fully swiveling or rixed. If fixed, the nose gear must have been steerable.