Twin Engine Fighters

[GregP]

It's sort of like when you go over the a automotive forums and the ban the word "Hemi" because it takes over the thread ... ha ha. The Hemi advocates think it is best-ever and the Hemi-haters point to engines that are better but not Hemis. The battle rages on ...

The Whirlwind seems to have a similar effect that I don't mind because any civil talk about aircraft is OK with me, particularly if it is about WWII aircraft. It's one of my 2 - 3 favorite subjects. The battle about "best" WWII anything still rages on, too, even with tanks and handheld weapons. Maybe the Jeep wins it's category easily, but almost nothing else does. We'll probably have someone post about a "better Jeep," so that category might not be a shoo-in, either.

Hey Graugeist,

That McDonnell Model 1 looks neat, and you probably have a point about single engines driving twin props. I'd hate to have a good engine but experience one prop hub damage that results in a stuck left or right driveshaft over enemy territory. That would be the pits! ... going down in a single-engine plane with a good engine because one of two prop drive gears takes out the power train.

You could design around it with a shear pin, but again, I'd hate to go down because the shear pins sheared while I was flying through airborne debris after making a kill. Maybe it's a good thing they didn't build one ... maybe not.

 

[pbehn]

My personal favourite as twin engined fighters are the Hornet and Tigercat both came too late for the war but that is significant, Jets had taken over the fighter role in most theatres so twin engined prop fighters filled the need for long range and carrier borne fighters for a while.

To make a twin engined fighter able to compete with a single engined plane you must have a single crew, minimal airframe and fuel, this means your twin fighter has all the drawbacks of a single engined fighter for other missions. I personally dont believe that a twin could be competitive in roll rate and probably dive performance, though maybe a little better in climb speed and range.

Fighters were part of a conflict, they were maybe at the top in aircraft performance, but that trends more towards a side show. There is no doubt that a Bf 109 was a better fighter than a Beaufighter but I doubt anyone in the RAF was concerned that Beaufighters were not downing 109s and equally the LW were very concerned as to what to do about the Beau and later the Mosquito. A twin allows a second crewman internal bomb load and greater range without compromising speed. In my opinion every mission where a Twin hit the target and got away counts as a victory of sorts. The extra cost of any twin must be justified it must carry a threat apart from to other fighters.
The Whirlwind and P38 were specifically designed as single seat fighters and were good but in the limit struggled against the best S/E fighters, being single seat restricted their utility in other roles

The Hornet was developed from the Mosquito, I personally dont believe that the RAF would have traded Mosquitos for Hornets during WW2 the Mosquito as a night fighter bomber fighter bomber photo recon plane had much more utility.

 

[GregP]

Not sure the P-38 struggled against single seaters. Early on it struggled against green pilots and a couple of mechanical issues. Once the intake manifolds and fuel issues were figured out, it had only the limit Mach issue to worry about, and more than held it's own against single-seat Japanese fighters.

Generally, though, you make pretty good points. I'll bet the guys flying twins who made it home on one engine would take some issue with the contention here. Roll rate is relative. You can make a twin roll adequately. The USA, for instance, had specifications on roll rate. We probably would not have acepted the Fw 190 until the roll rate was slowed down. While that may seem counter-intuitive, the US fighters in general did very well against any competition, despite many times rolling a bit slower ... the Hellcat in particular.

I like the Hornet a lot, but I think the primary fault was being made of wood instead of Aluminum. It was fast, climbed well, rolled well, certainly had adequate range to get to Berlin and back from London, and was well armed. I don't know whether the British would have traded Mosquitoes for Hornets had they the choice, but if they did, they wouldn't be losing anything on the fighter side ... that's for sure. I'd have to think that one over because the Mosquito was a solid performer in so many areas. That takes nothing away from the Hornet which, if anything, was a solid performer, too ... but not in all the same areas.

Food for thought at any rate.

 

[pbehn]

Greg The P38 had some great qualities but when I say the best single engined planes I meant the LW as opponents or late Spitfire P51 P47 Tempest as best in class. Sure the Hornet could get to Berlin but what would it do there if no one wanted to fight strafing Berlin at roof top height makes you vulnerable to anyone with a machine gun or rifle.

The performance of the Hornet and Tigercat seem great but being twins they had range and were ordered I dont really know if they would have been eaten by spiteful's fury's(or similar) that wernt ordered, this also ignores the jet age which had already dawned

 

[GregP]

You make some good points there pbehn. After the P-38's faults were fixed I doubt it would have had too bad a time against the Luftwaffe except for top speed late in the war. So it's probably good it went to the MTO / PTO where this wasn't much of a drawback.

As for what would a Hornet or Tigercat do over Berlin when they got there, their duty would be to escort bombers, not attack Berlin. That's why we sent bombers. I think they would have broken off and stayed out of the flak, and rejoined as the bombers left the flak ... just as the actual escorts did.

People also tend to forget how heavily armed the Tigercat was. It has four 20 mm cannons plus four 50-cal MG, none of which needed to be synchronized. They were all firing along the fuselage centerline plus or minus a few inches, except for one set of 20 mm cannons that were JUST inside of the prop arc, about 2.5 feet from centerline.

A very short burst would shred any aircraft in existence, even probably today ... if it somehow wound up in a Tigercat's sights. The Hornet was no slouch in armament, either. It lacked the four 50-cal MG but four 20 mm cannons alone firing close together is a pretty hard lick if it hits anything.

The Germans had some pretty hard-hitting planes, too, including some taht had two 20 mm plus two 30 mm ... but they really didn't face similar armament coming back at them very much. Might have been quite a surprise, had it happened earlier. Good armor against 50-cal usually isn't good armor against 20 - 30 mm cannons.

But you know all that and your points are well taken. I bet these very arguments were being discussed in 1941 - 1943.

 

[tomo pauk]

Hornet, even with 60 or 70 series Merlins would've been an asset for late ww2. The Tigercat was a short range fighter, with less fuel per engine than even the early P-47; no Berlin for it until more internal fuel is crammed in.

 

[kool kitty89]

Actually not ejector exhausts.

The XP-67 was fitted with a turbo for each of its IV-1430s. They were mounted so that their axis was horizontal, or nearly so, and the exhaust pointed rearwards. In the rear view you can probably make out that the "ejector exhausts" actually comprise two pipes - the exhaust proper and the wastegate pipe.

Yes, wrong term. Turbo exhausts configured to provide at least some additional thrust (in theory).

One of the design issues that the XP-67 ad was that there was no heat shield or firewall between the engine and the turbo.

Hmm, if the turbo was mounted back to back with the engine, I wonder how the exhaust was arranged for the turbine nozzle to be ducted rearward like that without running into the landing gear assembly or resorting to some fairly significant turns in the exhaust manifold. It looks like the wheels retract straight back and don't rotate to lay flat more like the P-40, F4U, or Ju 88.

I believe there was a proposal to fit Packard Merlins to the XP-67.

That, turbocharged V-1710s or 2-stage V-1710s would all be compelling options. (at least once the latter got water injection) If V-1710 turbocharger installations were less compact than the XI-1430 ones, they could always have used single stage supercharged engines for interim testing purposes. (or 2-stage ones if available, though the single stage models might be easier to mount)

Using 2-stage supercharged engines might have made the mixed-power arrangement easier as well, freeing up the rear of the engine nacelles to house the turbojet engines exclusively without turbocharger ducting to consider.

Wish they had sorted out the engines, but McDonnell went on to do great things anyway, didn't they?

Or if the engines failed in a less catastrophic manner and left the primary prototype airframe intact for further testing.

It's sort of like when you go over the a automotive forums and the ban the word "Hemi" because it takes over the thread ... ha ha. The Hemi advocates think it is best-ever and the Hemi-haters point to engines that are better but not Hemis. The battle rages on ...

Or hemi vs 4vpc, or vs sleeve valve which is actually what happened to radial engine development during WWII or even a bit before. Those hemispherical combustion chambers allowing very large intake and exhaust valves of areas previously only possible using Bristol's dual intake and exhaust valve arrangement. (though also making intake and exhaust manifold routing simpler than the 4vpc arrangement)

The Whirlwind seems to have a similar effect that I don't mind because any civil talk about aircraft is OK with me, particularly if it is about WWII aircraft. It's one of my 2 - 3 favorite subjects. The battle about "best" WWII anything still rages on, too, even with tanks and handheld weapons. Maybe the Jeep wins it's category easily, but almost nothing else does. We'll probably have someone post about a "better Jeep," so that category might not be a shoo-in, either.

I actually like Gloster's twin more than the Whirlwind, everything but the cockpit/nose looks nice on the F.9/37 and the single and 2-seat merlin engined (paper) so-called 'Reaper' project following it seem to have solved that aesthetic problem nicely.

 

[GregP]

I always liked those two planes, too. Wish they had proceeded.

 

[pbehn]

After the P-38's faults were fixed I doubt it would have had too bad a time against the Luftwaffe except for top speed late in the war. So it's probably good it went to the MTO / PTO where this wasn't much of a drawback.

As for what would a Hornet or Tigercat do over Berlin when they got there, their duty would be to escort bombers, not attack Berlin. That's why we sent bombers. I think they would have broken off and stayed out of the flak, and rejoined as the bombers left the flak ... just as the actual escorts did.

From what I have read the P38 in the hands of an experienced pilot could do quite well. I dont know how much training is required to transition to being a good pilot of a twin fighter compared to the transition from say a P 47 to P 51. Since my last post I have read here and there that the Tigercat had excellent dive and good roll performance so maybe if it had the range it could have done something BUT would it have been better than the P51 ..it would certainly have cost more. Both the Hornet and Tigercat were designed as single seat fighters and both later had a radar operator added.

I am surprised that people didnt see the writing on the wall and design then from the start as twin tandem seat. I could see some use for a plane with radar controlling groups of escort fighters spotting the LW by radar rather than eye sight, in the way a master bomber controlled RAF night raids. That role could have been performed by a mosquito, I presume by the fact it wasnt done there was no point to it. Its a shame that the tigercat and Hornet didnt serve in anything other than side shows and not really in their intended role but I dont see much pressure from the RAF anytime in the war for a faster lighter single seat mosquito. the Hornet was a private venture at wars end to meet a possible requirement in the far east.

I have read Winkle Browns glowing report on the Hornets general handling and performance, I presume he would have a different idea of the night fighter version which had a man and radar equipment shoehorned in the rear fuselage, that must be just about the worst "gig" in post war aviation.

 

[GrauGeist]

The Tigercat actually has it's lineage linked to pre-war via the XF5F/XP-50

In the early stages of developing the F7F, the radar equipment available was bulky and was not an option. It wasn't until the APS-6 system, which became available in 1944, that smaller airframes could accept a radar system for night-fighting missions.

A good example of this, would be the P-38E "Swordfish" which was modified to have an early radar system, with nowhere near the capabilities of the SCR-720 system. With the modified two-seat fuselage and antenna array in the nose and receivers on each wing, there would certanly be a performance penalty. It would be several years before the P-38 once again carried a radar system, this time, the APS-6 aboard the P-38M.

 

[pbehn]

In the early stages of developing the F7F, the radar equipment available was bulky and was not an option. It wasn't until the APS-6 system, which became available in 1944, that smaller airframes could accept a radar system for night-fighting missions.

That is what I meant by seeing the writing on the wall, the RAF were using experimental RADAR set ups in aircraft from 1938/39 and operationally from 1940, surely someone could see the advantage eventually of a RADAR equipped fighter. If in dog fighting position and awareness is critical I would think it is a great way to gain position before your enemy could possibly see you.

 

[kool kitty89]

That is what I meant by seeing the writing on the wall, the RAF were using experimental RADAR set ups in aircraft from 1938/39 and operationally from 1940, surely someone could see the advantage eventually of a RADAR equipped fighter. If in dog fighting position and awareness is critical I would think it is a great way to gain position before your enemy could possibly see you.

Even in day fighter operations? Would compact late-war radar have allowed high performance 2-seat twins to be effective in daylight operations? (seems more useful for interceptors than escorts -in escort situations, bombers would be better suited to handling early-warning duties once suitable radar arrived)

 

[GrauGeist]

Well, the "powers that be" knew of the emerging technology, but it was still developing and would be hard to predict just where the technology would be several years down the road. However, the designers and engineers weren't fully aware of the technology unless they were directly involved in a project. In the case of the P-61, it wasn't even designed for a radar system originally, but Jack Northrup was able to change the design to accept it.

Now, from the time the P-61 and the SCR-720 was designed, until the time it went into service, the airborn radar systems changed a great deal. So trying to actually design an airframe with a future system in mind would be a heck of a gamble.

 

[pbehn]

Even in day fighter operations? Would compact late-war radar have allowed high performance 2-seat twins to be effective in daylight operations? (seems more useful for interceptors than escorts -in escort situations, bombers would be better suited to handling early-warning duties once suitable radar arrived)

Just an idea, as part of groups forward of the bomber stream looking for fighters taking off and forming up or to the sides of the stream. I think LW interceptors had enough problems without adding the weight of a radar set and operation.

 

[wuzak]

Hmm, if the turbo was mounted back to back with the engine, I wonder how the exhaust was arranged for the turbine nozzle to be ducted rearward like that without running into the landing gear assembly or resorting to some fairly significant turns in the exhaust manifold. It looks like the wheels retract straight back and don't rotate to lay flat more like the P-40, F4U, or Ju 88.

I didn't mean to suggest that the turbo was right up against the engine. It was, most likely, towards the rear of the nacelle, behind teh wheel bay. I'd suggest that the vent at the top rear of the nacelle is about where the turbo was mounted.

That, turbocharged V-1710s or 2-stage V-1710s would all be compelling options. (at least once the latter got water injection) If V-1710 turbocharger installations were less compact than the XI-1430 ones, they could always have used single stage supercharged engines for interim testing purposes. (or 2-stage ones if available, though the single stage models might be easier to mount)

The turbo used would be the same and the position would be the same, so the V-1710 turbo installation would be the same as the IV-1430's.

 

[pbehn]

Well, the "powers that be" knew of the emerging technology, but it was still developing and would be hard to predict just where the technology would be several years down the road. However, the designers and engineers weren't fully aware of the technology unless they were directly involved in a project. In the case of the P-61, it wasn't even designed for a radar system originally, but Jack Northrup was able to change the design to accept it.

Now, from the time the P-61 and the SCR-720 was designed, until the time it went into service, the airborn radar systems changed a great deal. So trying to actually design an airframe with a future system in mind would be a heck of a gamble.

It may have resulted in some lumps and bumps on the airframe but if the second seat was already designed as an option it would be easier to sort. Maybe that was an oversight on all sides with the technical boffins not being able to communicate to A/C designers what may would be possible in 2 to 3 years time.

 

[GregP]

How about a suggestion for a twin that was built but never flown?

The Bf 109Z looks pretty good to me. The fuselages were Bf 109F-4's and when it was finished it was damaged in a hangar by an Allied bombing raid before being flown. More were planned but the war situation declined and they were never built again. Still, it looks competitive with the twins.

 

[pbehn]

How about a suggestion for a twin that was built but never flown?

The Bf 109Z looks pretty good to me. The fuselages were Bf 109F-4's and when it was finished it was damaged in a hangar by an Allied bombing raid before being flown. More were planned but the war situation declined and they were never built again. Still, it looks competitive with the twins.

View attachment 297527

For the 109Z and the P(F) 82 I can sort of see some slight advantages but wouldnt the pilot(s) get thrown about a lot in a roll because they arnt on the turning axis. I believe the F82 was quite successful in what it did but how did it handle? Did both crew have controls?

 

[GrauGeist]

Unlike the Bf109Z, the P-82 (later F-82) was built and technically available by war's end, but for lack of engines, the P-82B sat out the final months of the war.

As far as dual controls, some did (P-82B, F-82E, etc.), although the night-fighter version (P-82C/D, F-82F, etc.) had the left cockpit as the only control station and the right cockpit was for radar operator's position.

It turns out that the F-82 was very competetive in a dogfight against enemy aircraft, the first three U.S. aerial victories in the Korean war, were made by F-82Gs on 27 June 1950, over Kimpo as North Korean YaK-9s, YaK-11s and La-7s attempted an attack on departing transports. Two La-7s were downed and a phenominal dogfight ensued bewteen a YaK-11 and Lt. Hudson's F-82, resulting in the downing of the YaK for the first victory of the war.

 

[GregP]

When I read a pilot report on the F-82, all participants noted an unusual characteristic that everyone liked. To the pilot, it seemed as if the aircraft were rotating around his cockpit when it rolled. To the non-pilot, it seemed opposite. That is, both crew felt as though the aircraft were rolling around their own cockpit. So the issue you perceptively rasied above didn't occur.

That is NOT to say the Bf 109Z or any other "Siamese Twin" would have the same results. Because one twin-fuselage-fighter didn't have the issue doesn't mean others wouldn't have it. It would probaly have to be investigated for all such twins before any blanket statement could be made and even then, you can't be sure the next one wouldn't exhibit the problem.