1937-45: Doubling down on the 2-engined 'day fighters'

[Admiral Beez]

We can recall that Bf 110 have had a positive exchange (kills/loses) during the BoB. Despite being big and heavy, bigger and heavier than needed.

With a top speed at mid-level of over 330 mph, was there anything with two engines and two or more crew that was faster in 1939/40? The other twin-engined fighters like the Fokker G.I were slugs by comparison. So we must give Messerschmidt some credit.

 

[Reluctant Poster]

I'm talking about what can be read in the most recent publications, not just dividing the claims with losses.

Point me in their direction please

 

[Howard Gibson]

I'm talking about what can be read in the most recent publications, not just dividing the claims with losses.

In 1939/1940, the Luftwaffe were flying the least manoeuverable and the most successful fighters. This included the Bf110. They were using hit and run tactics, and making no effort to dogfight. With an altitude advantage, a Bf110 could engage and break off combat with Hurricanes running at 6-1/4psi. Spitfires were too fast. The only way to break off from a Spitfire is to hope it switches to the bombers you were protecting.

Profile #111 The Hawker Hurricane I has a table at the back showing turning radii at 300mph and 10,000ft. The data is quoted by Len Deighton in his book Fighter. The Hurricane could turn at 7.5g, the Spitfire at 7.0g, and the Bf110 5.2g. My interpretation of this is that the Bf110 was not stressed for high Gs. This makes for a lighter, faster aircraft, unless something catches you and forces you to turn.

A Bf109 turned at 8.1g and had the tightest turn radius. I assume this was due to the pilot's semi-reclining seating position. Len Deighton did not notice that this works only at high speed. At lower speeds, wing loading limits your turn radius.

 

[Shortround6]

A twin engined fighter, if well designed to eschew anything but necessary weight gain and extra crewmen should be faster than a single engined fighter. For example, is there any fighter powered by a single Allison V-1710 that's faster than a P-38 powered by two? The only twin engined, single-seat fighter powered by the Merlin is the post-war DH Hornet. If we made the DH Hornet in 1939 using the early Merlin, can we outpace 1939's Spitfire or Hurricane? Otherwise I don't see the point. As the P-51 shows, if you want longer range, you needn't add an engine.

A bit simplistic. No production single seat fighter with a single Allison engine used the turbo, The turbo added several hundred pounds and a number of cubic feet of volume.

The P-38 was designed to give to give the same performance as the P-39 (or what would become the P-39) except do it for twice as long ( 2 hours of endurance instead of 1).

The P-63 got a two stage supercharger, it also got a 2 ft longer fuselage to hold it. It also got a new wing (new airfoil) and it it makes comparing it to a P-38 rather hard. The P-63 had a more modern airfoil than the P-38. They used water injection instead of an intercooler that crossed over with the P-38 power plant. The P-63 could make around 1800hp at sea level instead of the 1500hp (about) that the P-38J could do in fall 1943. However in the thinner air (less drag) above 20,000ft the P-63 was making a bit under 1200hp while the P-38J engines were good for about 1300hp to 25,000.

P-63 also truly sucked at fuel capacity. 126 US gallons internal doesn't get much further than a Spitfire with a high HP engine.

Now shoving a pair of Merlin IIIs into a single seat fighter but doubling the fuel per engine might not give you any better speed than the Spitfire. UNLESS you also used a thin wing a few other tricks. Which makes it hard to fit in over 300 imp gals of fuel.

 

[Shortround6]

Why use 2 engines when 1 can do the job? One propeller to purchase and maintain. This can be extended to all the auxiliary systems such as fuel. Double the maintenance. Less pilot training, very important when your air force is expanding at a breakneck pace. The number of pilots qualified to teach how to fly a high performance twin in the 1930s was tiny. A smaller, more agile aircraft, rate of roll of twins is slower.

I don't want to turn this into another Whirlwind thread but...................Somebody (or more than one?) wanted to cancel the Whirlwind because it used two engines, not one. Fair enough except that the plane they wanted to replace the Hurricane (and Spitfire) with used 24 cylinder engines, not 12 cylinder engines. It also used larger wing, and it weighed over 9,500-10,500lbs
British (and American) twin engine fighter training was rather sketchy at this time (got better later) and nobody has ever said that the Typhoon (or Tornado) was easy to land.
The Early Typhoon used an approach speed of about 100mph IAS instead of 105-110 that the Whirlwind used and actual touch down was slower than the Whirlwind.

It seems that there was a bit of selected editing going on.

Stick a better engine in the Spitfire (MK XX?) and the single instead of twin argument holds up very well. Claiming the big Hawker fighter will be much cheaper because it is single engine is papering over a lot things.

 

[tomo pauk]

Point me in their direction please

Books by J. Vasco are pretty recent. Eg. from here
He is also a member of this forum.

 

[drgondog]

Johnson and Kartveli didn't have any input into the design of the V-1710, in fact Kartveli didn't use the V-1710 in his aircraft. The 2,000 HP V-1710G series were a post war development that was never installed in a P-38.
The USAAF actually preferred the V-1650. The V-1710 was the only major US engine that that saw a reduction in production in 1944 when all the others showed increases. The V-1710 was cancelled shortly after VE day while the V-1650 remained in production until after VJ day

Except for V-1710-143 (very ltd) which powered F-82E and Subsequent. It was a derivative of the -119 so may have been kit mod.

 

[Admiral Beez]

A bit simplistic. No production single seat fighter with a single Allison engine used the turbo, The turbo added several hundred pounds and a number of cubic feet of volume.

Well yes, that's what I'm getting out. A twin-engined, single-seat fighter only makes sense if it can get more out of two engines than a single-engined fighter can get out of one. Otherwise, it's a waste of an additional engine. And that's what the Lightning accomplished, taking an engine that single-engined fighters could not maximize and by using two of them in a bespoke design to make a superlative aircraft.

 

[tomo pauk]

The P-38 was designed to give to give the same performance as the P-39 (or what would become the P-39) except do it for twice as long ( 2 hours of endurance instead of 1).

200 gals of fuel in the XP-39 might've probably gave the same endurance like what the XP- and YP-38s has with 400 gals

The P-63 got a two stage supercharger, it also got a 2 ft longer fuselage to hold it. It also got a new wing (new airfoil) and it it makes comparing it to a P-38 rather hard. The P-63 had a more modern airfoil than the P-38. They used water injection instead of an intercooler that crossed over with the P-38 power plant. The P-63 could make around 1800hp at sea level instead of the 1500hp (about) that the P-38J could do in fall 1943. However in the thinner air (less drag) above 20,000ft the P-63 was making a bit under 1200hp while the P-38J engines were good for about 1300hp to 25,000.

Granted, the 1st 'military grade' 2-stage V-1710s were lacking wrt. altitude power, perhaps mimicking what the 1-stage fully rated DB 605A was good for? The P-38J was supposed to do 1425 HP at 25000 ft, and even 1600 in WER at that altitude.

With that said, there is a number of details that also need to be mentioned. Engine in the P-63 was without the intercooler drag (for how many MPH difference in top speed?), there is no drag related to the cooling of the turbo, as well as no drag from the exposed turbo, it was giving significant exhaust thrust (talk 15% extra propulsive power above 20000 ft?) unlike what the turbo did. No requirement for ducting to and from the turbo (adds indeed to the size of A/C = a bit greater drag and weight).
The 2-stage V-1710 on the E11 (on P-63A) and E21 (on P-63C) was also with the carb before the 1st stage, cost of ~2500 ft in the rated height. Plus, for whatever the reason, it seems like the E11 was bad on taking advantage of the ram effect, gaining only 1700 ft of rated altitude at max speed (~400 mph on a good day), while the E21 and E22 (on P-63E, with carb relocated in the intake of the 2nd stage) were 'snatching' extra 4000 ft. The turbo V-1710, as well as the turboed R-2800, were gaining much less from the ram effect.

(unfortunately, the figures of 1800 HP at 24000 ft for the E21 - Vee's for victory pg. 258 - as well as the similar claim for the F28R on the XP-40Q-3 pg. 186 same book - are badly wrong)

P-63 also truly sucked at fuel capacity. 126 US gallons internal doesn't get much further than a Spitfire with a high HP engine.

Bell really sucked in making the most of the P-63s wing, leaving a lot of volume free by the time USAAF was eager to have long range fighters in numbers, and even the HMG didn't fit in. All of that despite the wing of generous area and thickness, and a lot information about what can be packed in a wing if one wants it.
Add the engine that was about a year behind the curve, and we can congratulate to the USAAF to not choosing the P-63 for their fighter squadrons.

Now shoving a pair of Merlin IIIs into a single seat fighter but doubling the fuel per engine might not give you any better speed than the Spitfire. UNLESS you also used a thin wing a few other tricks. Which makes it hard to fit in over 300 imp gals of fuel.

Doubling the fuel per engine installed vs. a Spitfire (= ~350 imp gals for a 2-engined fighter) was not in the cards for the RAF's fighter until well, well into ww2.
Not that it can't be done, since the twins - especially the 1-seaters taildraggers designed around 1000+ HP engines - have generous space in both fuselage and in the wings.

 

[Shortround6]

Well yes, that's what I'm getting out. A twin-engined, single-seat fighter only makes sense if it can get more out of two engines than a single-engined fighter can get out of one. Otherwise, it's a waste of an additional engine. And that's what the Lightning accomplished, taking an engine that single-engined fighters could not maximize and by using two of them in a bespoke design to make a superlative aircraft.

I think you are missing the point. While the basic engine was the same the powerplant/s were different. Unlike a two stage Merlin where the single engine and twin engined planes used pretty much the same engine/power plant the turbo Allisons (and turbo Radials) had quite a bit of extra stuff in the powerplant that added weight and bulk.
Curtiss XP-60A with turbo Allison.

Maybe not the best example of packaging.
The 'same' airframe with a Packard 28.

There is a LOT of extra fuselage hiding the turbo parts/accessories.
Which makes comparing turbo and non turbo planes using the same basic engines very difficult.

 

[Admiral Beez]

Curtiss XP-60A with turbo Allison.
View attachment 798538
Maybe not the best example of packaging.
The 'same' airframe with a Packard 28.

View attachment 798539
There is a LOT of extra fuselage hiding the turbo parts/accessories.
Which makes comparing turbo and non turbo planes using the same basic engines very difficult.

Let's compared apples to apples then. Were the single-engine turbo Allison aircraft above faster than a P-38?

 

[Shortround6]

200 gals of fuel in the XP-39 might've probably gave the same endurance like what the XP- and YP-38s has with 400 gals

We may run into the planned operational endurance vs the ferry range endurance/fuel capacity.
A lot of US fighters carried more fuel than they were estimated at/tested at/approved for for ferrying.
XP/YP-39 was very overweight. Performance figures with 200 gal on fuel on board?
Estimates do vary
Neither plane actually flew with the 'paper' engines that the estimates were based on (1000hp).

Granted, the 1st 'military grade' 2-stage V-1710s were lacking wrt. altitude power, perhaps mimicking what the 1-stage fully rated DB 605A was good for? The P-38J was supposed to do 1425 HP at 25000 ft, and even 1600 in WER at that altitude.

I used the tested performance of a below standard (book?) example from here.

http://www.wwiiaircraftperformance.org/p-38/P-38J_43-13563_Eng-47-1656-A.pdf

A sorted out example would do better I was trying to get close to the P-63 in late 1943.
The first production P-63C with the -117 engine doesn't show up until Dec 1944. Just a little late.

Bell really sucked in making the most of the P-63s wing, leaving a lot of volume free by the time USAAF was eager to have long range fighters in numbers, and even the HMG didn't fit in. All of that despite the wing of generous area and thickness, and a lot information about what can be packed in a wing if one wants it.

Well, you might have been able to find room for the fuel, But the P-63A went just under 9000lbs clean so adding 300lbs of fuel plus tanks just to get it to a Mustang without rear tank isn't going to do it any favors
The P-63 was a hot rod at low altitude but the extra stage didn't do what was needed in 1944.

 

[don4331]

Doubling the fuel per engine installed vs. a Spitfire (= ~350 imp gals for a 2-engined fighter) was not in the cards for the RAF's fighter until well, well into ww2.
Not that it can't be done, since the twins - especially the 1-seaters taildraggers designed around 1000+ HP engines - have generous space in both fuselage and in the wings.

S Shortround6 - I'm also trying not to turn this into Whirlwind rehash, but:

You don't need 2x the fuel per engine; on ~40% more fuel (134 gal), the Whirlwind had >25% more range than Spitfire I/II (94 gal). Alternate comparison; Whirlwind has ~10% less range on ~15% less fuel than a Typhoon. Twins are more efficient in cruise.

And I'm not aware of any Spitfire fighter with 175 imp gal internal fuel.​

And Petter had plans to have double the fuel (192 gal) of Spitfire in Whirly Mk. II.​

As I see it there are 3 challenges:

1. Picking the correct engine - Whirlwind/Fw.187 die because their engines Peregrine/Ju.210 are removed from production. P-38/Bf.110 soldier on as their engines are in production/improved to the end of the war.​

2. Hitting the sweet spot for size - small enough for excellent performance day one, big enough to support more power, more fuel, more armour, more armament. Whirlwind with 250 ft^2 is too small, Bd.110 at 414 ft^2 is too big.​

3. Navigating the politics. There is only limited window of opportunity to get the Mk. I version into production (true of all fighters); if you miss the window Whirlwind uses ~70% more material than Spitfire, not 3x (not even 2x); your accountants better be ready to go head to head with theirs. You need AM to commit to your plane. You need a C. R. Fairey in your court​

Not sure if Gloster F9.37 could meet the duck test.

1. The Taurus isn't committed to BC's single engine bomber/Fighter's Command's point defense fighters. And the P&W R-1830 provides a fallback should the Bristol engine encounter development difficulties.​

2. With 386 ft^2, G.39 is a little on the large side, but 360 mph performance in '39 is pretty darn good*. 4 - LMG/2 - 20mm cannon is pretty good too.​

3. This Achilles heal - Gloster is owned by Hawkers. Does the F9.37 compete too much with Typhoon? F9/37 was designed to be constructed by semi-skilled labour - does that make is candidate for overseas (Cdn.) production <not so much about the skill level as the distance from home office>.​

​

*I recognize performance will be hurt by extra weight for self sealing tanks, armour, etc, but 100 octane/supercharger improvements are supposed to offset that.​

 

[wuzak]

I don't want to turn this into another Whirlwind thread but...................Somebody (or more than one?) wanted to cancel the Whirlwind because it used two engines, not one. Fair enough except that the plane they wanted to replace the Hurricane (and Spitfire) with used 24 cylinder engines, not 12 cylinder engines.

Perhaps because the Whirlwind had the wrong engine.

They also had a back-up design for the Whirlwind which also twin engine - the Bristol Beaufighter.

 

[GrauGeist]

It would have been interesting to see what Italy could have done with the Savoia-Marchetti SM.88/SM.91/SM.92 types if they had more time and resources.

 

[Admiral Beez]

Perhaps because the Whirlwind had the wrong engine.

The Whirlwind had terrible range for a twin. Move the radiators and fill the void with fuel. But the new rads will add to drag and speed loss.

 

[tomo pauk]

Well, you might have been able to find room for the fuel, But the P-63A went just under 9000lbs clean so adding 300lbs of fuel plus tanks just to get it to a Mustang without rear tank isn't going to do it any favors
The P-63 was a hot rod at low altitude but the extra stage didn't do what was needed in 1944.

Remove the wing guns' installation, together with the ammo, and there is the weight allowance.
While we're at it, replace the 37mm gun with 20mm belt-fed gun.

 

[TM06]

While we're at it, replace the 37mm gun with 20mm belt-fed gun.

This is getting off topic but I don't know if that's the wisest choice. The only belt-fed 20 mm the US had at their disposal was the AN/M2 - a hilariously unreliable gun. The 37 mm M4 and subsequent M10 were not bad they just lacked muzzle velocity, something the M9 version tried to fix with a longer barrel and bigger, longer round (37x223 I think?). IIRC the M9 had a MV of 3,000 f/s or about 910 m/s.
What I would suggest is dropping the wing guns and attempting to mate the M9 to the M10's link system. The extra weight of the M9/10 would be compensated for by the removal of the wing guns and the centre-of-gravity would be much better.

 

[Shortround6]

Remove the wing guns' installation, together with the ammo, and there is the weight allowance.
While we're at it, replace the 37mm gun with 20mm belt-fed gun.

Just give the things to the Russians or empty some .45s into the engines on the airfield/s. Save the pilots and some fuel.

 

[Shortround6]

This is getting off topic but I don't know if that's the wisest choice. The only belt-fed 20 mm the US had at their disposal was the AN/M2 - a hilariously unreliable gun. The 37 mm M4 and subsequent M10 were not bad they just lacked muzzle velocity, something the M9 version tried to fix with a longer barrel and bigger, longer round (37x223 I think?). IIRC the M9 had a MV of 3,000 f/s or about 910 m/s.
What I would suggest is dropping the wing guns and attempting to mate the M9 to the M10's link system. The extra weight of the M9/10 would be compensated for by the removal of the wing guns and the centre-of-gravity would be much better.

They managed to to get the gun in the P-38 to work fairly well. Not great but few, if anyone, was yanking the 20mm out and replacing it with a 5th .50 cal?
Of course they mounted the gun in a rather heavy mount/cradle which helped.

The M10 also had a rather low rate of fire. Not improved with the M9 (slightly slower) and the MV was a lot closer (under 800ms) unless using some oddball AT ammo.
The M9 also gained about 80-90kg in weight (nearly double) over the M10. So yes, ditching the wing .50s will get you close. The M9 did use a belt feed system.
It might be interesting to see what the recoil loads were from the M9 though. IS the much heavier gun enough to dampen out the significantly increased recoil?