The 'no-nonsense' twin-engined fighters for 1938-1943
- Thread starter tomo pauk
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wuzak
Captain
Like the Supermarine Type 313? Actually a cannon armed fighter proposed for F37/35, which led to the Whirlwind.
I believe Kestrels were the engine of choice. Hispanos were an alternative, possibly with cannon firing through the hub.
May have been able to fly in the period requested by OP had it not been cancelled.
The Type 324 with twin Merlin as 12 x 0.303" mgs in outer wing panels may fit the requirement, but would not have flown in the period required. Possibly a prototype would have been available about the same time as the Tornado and Typhoon in late 1939/early 1940. Would have developed into the cannon armed Type 327.
Shortround6
Major General
Well, F5F with 2400hp doing 380mph (?) after drag reduction program
P-47 with water injection 2200hp at sea level
333 mph?
Engines on the F5F are each bigger than the R-2800
F5F would have been faster at sea level than P-47M using 2800hp.
Something doesn't seem right.
FLYBOYJ
"THE GREAT GAZOO"
It doesn't - but many of the sources I've been coming up with show that 380mph at sea level the recorded maximum speed. I've been trying to find an official flight test report, even one from Grumman.
Shortround6
Major General
Best I have seen is
http://www.alternatewars.com/SAC/XF5F-1_and_XFL-1_PD_-_26_December_1942.pdf
I don't know if they are true. It seems like the F5F was designed around a promised engine that never materialized.
The promised two stage doesn't show up in the P & W model designation list. The R-1535-2 was a standard single speed engine used in SBU-2/3 aircraft.
Photo/s of an early mock up show different sized engine nacelles.
Somewhere there was another photo from a different angle but I can't find it at the moment.
Now if you look at the 2nd link you can find "estimated" 283 mph at sea level so we have the possibility of a typo?
Admiral Beez
Major
Skipping over what I found to be a confusing preamble (that's on me), and focusing on the question rather than the merits of the aircraft, I'd say Japan would benefit the most having 2-engined fighters. IJAF twin-engined interceptors like the Ki-83, J5N and Ki-96 can attack B-29 raids with less worry of long range, more agile single-engine escorts. And if we want to look at merits, their fast twins look wicked.
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Admiral Beez
Major
the same assumptions leads to the similar solutions - at least usual... Soviets have started working on this one at the period when PZL-38 have been dropped in favour of it's "bigger brother" PZL-48 which never reached prototype phase...
for this one theoretically powerplant selection was more correct than for PZL-38
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Shortround6
Major General
What do you want the twin engine plane to do???
Kelly designed the P-38 to be a twin because he didn't have a 1500hp single engine available at the time.
Now in about 1 1/2 years that changed.
Same for the Germans. They designed the Bf 110 because they couldn't get a single engine aircraft to do the job (speed, armament and range) with engines available (or soon to be delivered).
The French seemed to defy this logic. They were making twin engine everything. Most of the time using 500-700hp engines so the results weren't much different than using 1000hp single engines.
Kelly designed the P-38 to be a twin because he didn't have a 1500hp single engine available at the time.
Now in about 1 1/2 years that changed.
Same for the Germans. They designed the Bf 110 because they couldn't get a single engine aircraft to do the job (speed, armament and range) with engines available (or soon to be delivered).
The French seemed to defy this logic. They were making twin engine everything. Most of the time using 500-700hp engines so the results weren't much different than using 1000hp single engines.
A.G. Williams
Airman 1st Class
- 182
- Oct 10, 2020
This is my take on it, only specifically for the RAF/FAA: BRITISH WW2 MULTI
- Thread starter
- #32
Depends on the country.
USAAC will want a bomber destroyer - hence my notion that, initially (1938) the preferred weapon set-up is two 37mm cannons. Yes, that will not last for long.
RAF - a general-pupose fighter, with an accent towards killing the enemy bombers. 12 LMGs 1st, then 4 cannons once available.
Germans - something offensive and thus with good range/radius + firepower, and also suitable to intercept and shot down enemy bombers. All of that while not being afraid that enemy fighters might be a big threat.
Soviets - they started installing 20mm cannons on I-16s. A 2-engined fighter with V12 engines can carry 4 of those and have a greater speed. Similar situation with French, just they use 1 cannon on 1-engined fighters.
Italians - they saw how monoplane bombers in Spain were both fast and resilient. Going with 2 engines (I favor I-F Asso V12s, these are not as bad as A.74s) on a monoplane will mean speed and firepower.
Japanese - Asia and Pacific are big places, two engines might mean the engine-out situation is not equal to a fighter and pilot lost, can mount better firepower, can have ample range.
Poland - they need a quick way to move from obsolete PZL fighters.
Both Japanese and Italians have problem with actuall making enough of 2-engined fighters with their fragile economies and modest industry base when compared with other 'big' countries. Fuel situation in the Axis countries is also not good, to say at least - a 2-engined fighter force will use much more fuel than a 1-engined force.
Shortround6
Major General
Thank you Tomo.
What I was getting at is that the 2 two engine fighter should do something the single fighter could not.
At times armies, navies, air forces in 1930s (and other times) copied other forces.
"If they have one then we need one"
And not what they really needed.
The US 37mm is a bit confusing. In the Airacuda the guns used 5 round magazines. The early P-39 used a 15 round feed system. it didn't get the 30 round system until a bit later.
This is one reason the Airacuda got a 5 man crew.
People knew the cannon were coming, but it was hard to know exactly when to to leap on the horse. Especially for the single seat aircraft as you need a reliable feed system of large capacity or you are wasting you money.
If the guns won't fire more than a few seconds the extra range/endurance isn't as useful.
For the Americans having four .50 cal guns that worked (and they often didn't in the late 30s) was better than two 37mm guns that didn't.
But building 20 twin engine fighters may not get you anything that 40 single engine fighters won't. depends on range and years and the engine situation.
As you know, I like the Whirlwind. Had it been pushed harder in might have done a lot more but it was never going to be an escort fighter. It's wing was smaller than a Hurricane. Without a major redesign it had limitations. It was never going to be a bomb truck either unless very short range.
But using twin Merlins to haul 12 .30s when you have fighters with single Merlins hauling eight guns doesn't make sense. Unless you can use them at long range.
Give the pilots gunnery training rather than trick fighters
And the difference might only be a year or two. The P-38 snuck in under the wire but if the P-38 didn't show up when it did would it really do much the P-47 could not?
Once the R-2800 showed up the need for the US to make twin engine fighters using 1200-1425hp engines went away. The production lines were set up and they were useful but they were sort of a duplication. (assuming they sort out the P-47 drop tank problem sooner).
What I was getting at is that the 2 two engine fighter should do something the single fighter could not.
At times armies, navies, air forces in 1930s (and other times) copied other forces.
"If they have one then we need one"
And not what they really needed.
The US 37mm is a bit confusing. In the Airacuda the guns used 5 round magazines. The early P-39 used a 15 round feed system. it didn't get the 30 round system until a bit later.
This is one reason the Airacuda got a 5 man crew.
People knew the cannon were coming, but it was hard to know exactly when to to leap on the horse. Especially for the single seat aircraft as you need a reliable feed system of large capacity or you are wasting you money.
If the guns won't fire more than a few seconds the extra range/endurance isn't as useful.
For the Americans having four .50 cal guns that worked (and they often didn't in the late 30s) was better than two 37mm guns that didn't.
But building 20 twin engine fighters may not get you anything that 40 single engine fighters won't. depends on range and years and the engine situation.
As you know, I like the Whirlwind. Had it been pushed harder in might have done a lot more but it was never going to be an escort fighter. It's wing was smaller than a Hurricane. Without a major redesign it had limitations. It was never going to be a bomb truck either unless very short range.
But using twin Merlins to haul 12 .30s when you have fighters with single Merlins hauling eight guns doesn't make sense. Unless you can use them at long range.
Give the pilots gunnery training rather than trick fighters
And the difference might only be a year or two. The P-38 snuck in under the wire but if the P-38 didn't show up when it did would it really do much the P-47 could not?
Once the R-2800 showed up the need for the US to make twin engine fighters using 1200-1425hp engines went away. The production lines were set up and they were useful but they were sort of a duplication. (assuming they sort out the P-47 drop tank problem sooner).
- Thread starter
- #34
For the Americans, a 2-engined fighter can be heavily armed and still perform well. A fighter powered by a single R-1830 might be under-performing with two 37mm M4 cannons under the wings, ammo feed and supply is hndered by the restrictive space in the wings. A 2-engined fighter has far more leeway with ammo supply and feed, and the load is shared by two engines instead of just one.
Until the 37mm issues are sorted out, we might, possibly, make an alternative weapon set-up that holds 6 belt-fed .50s...
Six .50s with ample ammo supply will be too much to carry and still perform for the 1-engined fighters powered by R-1830s and V-1710s of the era.
At least Americans have money to buy, industry required and enough of fuel for both these and 1-engined fighters, unlike some Axis countries for example.
As you know, I like the Whirlwind. Had it been pushed harder in might have done a lot more but it was never going to be an escort fighter. It's wing was smaller than a Hurricane. Without a major redesign it had limitations. It was never going to be a bomb truck either unless very short range.
But using twin Merlins to haul 12 .30s when you have fighters with single Merlins hauling eight guns doesn't make sense. Unless you can use them at long range.
Give the pilots gunnery training rather than trick fighters
It is easy to like the Whirly. RAF didn't want to have their fighters being used as bomb trucks - fighters are supposed to shoot bombers over the UK, making any other suggestion a heresy.
British (and other) need to start early and with a design that is not tailor-made for a particular engine type. I've suggested going with a bit bigger airframe, 280-300 sq ft wing etc. With Kestrels, it will still perform at least as good as the historical Fw 187 (much better power at altitude for the British machine), and it will be easier to upgrade with Merlins rather than it was (not) the case with Whirly.
Hauling 12 .303s at 375 mph in 1940 (or at 340 mph in 1938) is a far better thing than hauling 8 .303s at 315 mph. Having 50% extra firepower is not a trick, nor is the extra speed. Once people start add protection for both pilot and fuel, a 2-engined fighter will have better time wrt. loss of performance (both speed and RoC). Replacing MGs with cannons is less tricky on a 2-engined fighter.
British also have wherewithal to produce and field 2-engined fighters along the 1-engined fighters.
A fighter that fits the description can be in production by 1938. The one with R-2800 can be in production by 1941?
USAAC was requiring new fighters pronto in the late 1930s (one of big reasons what they went all-out with P-40 and why XP-39 lost the turbo), the P-47 as we know it was not even in drawing phase in 1938.
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- Thread starter
- #35
People at Boeing have had a 1500 HP engine available for 1938 when the Clipper 1st flew.
High drag radial vs less drag with a water cooled V-12?
- Thread starter
- #37
Drag of one radial engine vs. drag of two V12s.
Shortround6
Major General
Which is more than a little late.
The Lockheed design team was working though the summer of 1937, the Army issued a contract ($163,000) for the XP-38 prototype on June 23rd 1937. Construction started in the summer of 1938 (?). A bit late to change from a twin engine design to a single engine airframe
The Engines in the 314 Clipper were rated at 1500hp/2400rpm for take-off and 1200hp/2100rpm at 5,000ft 'Normal/max continuous'
Questions are if GE can supply a turbo for the R-2600 at this time (The B-1 turbo used on the XP-38 might have been too small leading to needing two?) and if the R-2600 engine would cool at hi-altitude at power levels.
Drag of one big radial engine. The R-2600 was about 54-55 in diameter, it was almost identical to the R-3350, just two less cylinders on on each row.
The R-2800 had about 92% of the frontal area of the R-2600 which helps explain (not the only reason) the lack of R-2600 powered fighter designs.
Shortround6
Major General
We are scrambling times line here. In 1938 an R-1830 was a 1050hp engine for take-off. It wouldn't get to 1200hp until mid 1940 in production (and needed 100 octane fuel)
Hanging 37mm cannon under each wing wasn't going to to work.
Well, it is questionable if the six .50s were a good idea for R-1830s and V-1710s of 1942-43 let alone for 1938-40
Problems with the twin Kestrel is that the Kestrel is over 100lbs lighter than the Peregrine. Change to the Merlins is not impossible but is more difficult.
Problem is not helped by the extra 30-50 sq ft of wing if the wing is not strong enough to do what you want. If you want good performance with a pair of 745hp engines at 14,000ft
you have to keep the wing structure light. Changing from 970-980lb engines to 1430-1450lb engines (and coolant/oil coolers, ect) AND maintaining the strength requirements ( Mosquitos were not built to fighter "G" Loads) requires beefing up the wings (and more?) and that requires making a bunch of stress calculations.
FW 187 has about 10% less power than the Kestrel. Depends on who (and what) you believe about RAM pressure and exhaust thrust.
Just pointing out that time was a factor, especially for some people that want to cut aircraft types and combine production. It took a while and with hindsight we can see that the P-47 could do most of the things the P-38 could. BUT without hindsight it is not so obvious and it requires adding another R-2800 factory to make the engines (and changing P-38 production to P-47), also requires changes to the P-47 earlier.
- Thread starter
- #40
Which is more than a little late.
The Lockheed design team was working though the summer of 1937, the Army issued a contract ($163,000) for the XP-38 prototype on June 23rd 1937. Construction started in the summer of 1938 (?). A bit late to change from a twin engine design to a single engine airframe
Clipper was also a product of months of the work in the design bureau and in the workshops, it didn't just materialized a few weeks before the maiden flight
From Wikipedia:Boeing's bid was successful and on July 21, 1936, Pan American signed a contract for six.
That is a 13 months before the contract was awarded to the XP-38. The not-P-38 needs to be mooted around one 1500 HP engine from the start.
GE was not Bell, promissing the moon and failing to deliver, time after time.
If the 1500 HP engine will not cool well at 20000 ft, we can have the 1600 HP engine installed and down-rate it to 1500 HP. Or by 1941 install the 1750 HP engine and either down-rate it to 1600 HP, or go (oh, heresy) with R-2800. Cooling fan was also trialed in 1941 by NACA.
Still a 390- and later 400-mph aircraft.
A fighter with two V12s will also have two cooling systems to add drag, and the central pod/fuselage to add drag.
R-2800 was much earlier to have 2-stage supercharger, preceding such an R-2600 by 15-18 months? That's eternity in the lead up for the ww2. An extra of 100-250 HP is also worth mentioning.
No scrambling times here at all. My point about the R-1830-powered fighter is still there (1050 or 1200 HP base power): whether it has two 37mm cannons or six .50s, the performance loss will be substantial vs. a lighter weapon set-up.
Well, it is questionable if the six .50s were a good idea for R-1830s and V-1710s of 1942-43 let alone for 1938-40
Bingo
I'm not intending to have wing structure too light, after all a fighter is supposed to do 9-12G. Stress calculations is what engineers do, and there was plenty of aircraft that received heavier and more powerful powerplant in a commendable way.
I want good performance, thus the engine power is high for late 1930s (both for RoC and speed), and the drag needs to be kept reasonable.
Jumo 210G was supposed to do 670 PS at 3800m (661 HP at 12470 ft - works to about 630 HP at 14000 ft; all values are for no ram condition and without exhaust thrust). Kestrel as installed in the later versions of the Fury was making ~18% more.
Time was indeed a factor. This is one of the reasons for this thread - a simple 2-engined fighter can be designed, tested and put in production faster than a complex fighter that is supposed to be all-singing and all-dancing.
The 1-engined fighter with a turbo that uses a big radial is a thing I also favor. The P-47 still can materialze and have a fruitful life. What might meet the axe is the B-26, at least wrt. the powerplant choice. Or, the DB-7 is mated to V-1710s and thus the all-American fast bomber is born...
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