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

[ThomasP]

The 37mm M4 and M10 could both use articulated metal link belt feed. The first production P-39Ds were fitted with the belt feed, but production was quickly switched to the magazine type endless belt feed. The articulated metal belt feed arrangement only allowed 15 rounds of 37mm. The Russians received a bunch of the aircraft with the belt feed in their first Lend-Lease shipments. The image below is from the Mar'42 edition of the TM.

 

[yulzari]

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.

Indeed squeezing in more fuel and/or drop tanks for escort work would be a benefit but the Whirlwind was not intended for that. It was a home defence bomber destroyer to operate from British and French bases intercepting German bombers. Range was not a critical part of the task. Similarly in single engines types the Spitfire and Me109 had limited ranges because they were for the same short range interceptor or tactical escort roles.

We can see the uncertainly of the best way to do it at the time as the RAF employed three options. The multi rifle calibre single seaters, turret fighter and four cannon twin. What the twin brought was the same power as later developed single engine fighters but much earlier by using the leverage of mounting existing engines not relying upon new types or later developments. Essentially you can get a quasi Tempest two years early. It is not what you can make but what you can bring to the battle today.

First define the task then examine the means available to meet it. For the same four 20mm gun armament the Beaufighter was intended for tasks needing endurance hence had a longer range. Equally hence, was larger and heavier.

Whirlwind tests showed that a beard radiator on the engines gave much the same drag as the standard wing radiators so the inner wing could have been freed up for more fuel. All part of the differences that would have led to a more capable MkII which would better meet the post BoB tasks.

 

[Admiral Beez]

Indeed squeezing in more fuel and/or drop tanks for escort work would be a benefit but the Whirlwind was not intended for that. It was a home defence bomber destroyer to operate from British and French bases intercepting German bombers. Range was not a critical part of the task.

It's a fair point, and there's no need for long sortie time when you've all of sixty rounds per gun, for a grand total of about 4-5 seconds at 700 rpm. Once you shoot down your first or second bomber you're coming back to replenish anyway. This reminded me of the A6M paradox, where superlative sortie time enables you to stay in fight for a long period, but your ammunition capacity is tiny by comparison. IIRC, Midway, IJN fighters will near full fuel loads had to keep cycling back for ammunition.

So, if we're going to exceed its original low range role, the Whirlwind needs to move to a much larger magazine. I suggest to behind the pilot with a (at that time not existent) serpentine belt to the guns. CoG will need to be compensated for.

 

[tomo pauk]

First define the task then examine the means available to meet it. For the same four 20mm gun armament the Beaufighter was intended for tasks needing endurance hence had a longer range. Equally hence, was larger and heavier.

Let's not mix up the things.
Beaufighter was 1st and foremost a large and heavy aircraft. Reason for that was that it was a major redesign of a 2-engined torpedo bomber (of all things), with the hope that it will be fast and easy to start making the fighters.
This is how it became a fighter, and not because AM posted a specification for companies to compete in the task of making an over-sized 2-engined fighter, that Bristol won. The bomber genes are also a reason why it have had impressive fuel tankage for a fighter - again not a thing that RAF required back in the 1930s/early 40s.

Unfortunately, Bristol was one of companies that, when it was about making over-performing aircraft, was under-performing.

Whirlwind tests showed that a beard radiator on the engines gave much the same drag as the standard wing radiators so the inner wing could have been freed up for more fuel.

Any good source wrt. the Whirly with beard radiators?

 

[Admiral Beez]

Whirlwind tests showed that a beard radiator on the engines gave much the same drag

Beard radiators? Has any RR inline been so equipped? Surely the smaller Spitfire-like underwing rads would suffice? Or how about something like the P-38s?

 

[Shortround6]

We don't need to rewrite history this bad.

t's a fair point, and there's no need for long sortie time when you've all of sixty rounds per gun, for a grand total of about 4-5 seconds at 700 rpm.

If it's going to keep its low range role, the Whirlwind needs to move its now much larger magazines to behind the pilot with a (at that time not existent) serpentine belt to the guns. CoG will need to be compensated for.

The British lowered the rate of fire down to about 600rpm fairly early to gain reliability. But one extra second isn't that big a deal.
However NOBODY had a 20mm gun that held more than 60rpunds (except the Russians) in 1938-39 or most of 1940. Which is why the Bf 110 used the rear seater to change drums, as did the first 400 Beaufighters and even the Japanese Ki-45 used the rear gunner to change drums on their single 20mm gun.
HOWEVER, people were working on belt feed guns and the British were working on mechanical air powered contraptions that would hold 110-120 rounds for the Hispano.
There was no need to come up with serpentine belts that would go behind the cockpit. Not unless you can come up with electric motors that can move the belts through the feed ways.
There was also a bit of room in the Whirly's fuselage for around 40-50imp gal of fuel (two tanks).

Once the British decided to go back the original French belt feed system and came up with the belt feed guns for the 401s Beaufighter there is no reason that Belt fed Hispano's could not have been put in the Whirlwind except that all development had been canceled at that point.

 

[Shortround6]

Beard radiators? Has any RR inline been so equipped? Surely the smaller Spitfire-like underwing rads would suffice? Or how about something like the P-38s?

Somewhere RR had a beard radiator. They certainly had them in 1940/41.

And Halifaxes and Lancasters and Wellingtons and...........

Just about every airplane is a compromise

Unless you want to change the flap system and the landing run and several other things using under wing radiators might just mean a new airplane.
Mounting radiators ahead of the ailerons may not be a good idea either.
P-38s mounted radiators in the tail booms.
Whirlwinds had enough trouble with cooling the engines while running on the ground (the flaps had to be lowered at least somewhat) without turning the radiators sideways to the airflow.
This is what happens when you use a 250sq ft wing. You run out of space to put things.
You can make the wing bigger, but then you go slower.

 

[yulzari]

We don't need to rewrite history this bad.



The British lowered the rate of fire down to about 600rpm fairly early to gain reliability. But one extra second isn't that big a deal.
However NOBODY had a 20mm gun that held more than 60rpunds (except the Russians) in 1938-39 or most of 1940. Which is why the Bf 110 used the rear seater to change drums, as did the first 400 Beaufighters and even the Japanese Ki-45 used the rear gunner to change drums on their single 20mm gun.
HOWEVER, people were working on belt feed guns and the British were working on mechanical air powered contraptions that would hold 110-120 rounds for the Hispano.
There was no need to come up with serpentine belts that would go behind the cockpit. Not unless you can come up with electric motors that can move the belts through the feed ways.
There was also a bit of room in the Whirly's fuselage for around 40-50imp gal of fuel (two tanks).

Once the British decided to go back the original French belt feed system and came up with the belt feed guns for the 401s Beaufighter there is no reason that Belt fed Hispano's could not have been put in the Whirlwind except that all development had been canceled at that point.

Westland had developments in hand for either a 12x.303" pepper pot or a single row 150 round belt fed Hispanos noses.

 

[Shortround6]

Unfortunately, Bristol was one of companies that, when it was about making over-performing aircraft, was under-performing.

Unfortunately Bristol had several strikes against it.
The head designer, Frank Barnwell, died in Aug 1938. His assistant might have been very good, but the British were understaffed in many of these key roles.
ALL British companies were getting bad information from the government research establishments. Some believed it and some did not.
Government did a lot of panic buying. Trying to turn existing aircraft into other things to get something, anything, into production quickly.
The Beaufighter was hit by all three.
Bristol aircraft was let down by Bristol Engines to boot.
Flip/flops by the Air Ministry on requirement's didn't help.

 

[yulzari]

Beard radiators? Has any RR inline been so equipped? Surely the smaller Spitfire-like underwing rads would suffice? Or how about something like the P-38s?

The beard radiator is entirely from memory* but the Whirlwind radiator was a very poor example using the only available radiator type that would fit at the time of design and Westland were not happy with those and would have replaced them with others in a proper MkII. The beard was a known success for Rolls Royce and likely to be at least as effective as the existing MkI wing leading edge ones. However the existing installation still did the job for the MkI.

* but see The Westland Whirlwind British fighter aircraft of WW2 and post155 on this thread.

 

[Shortround6]

Westland had developments in hand for either a 12x.303" pepper pot or a single row 150 round belt fed Hispanos noses.

The guns were not belt feed. They had a magazine with a number of vertical columns that feed downwards and a feed system to push the rounds across the bottom of the magazine to the gun. It was powered by compressed air. Unfortunately the thing used many times the amount of air originally estimated and existing air tank and compressor could not keep up with one gun for very long let alone 4 guns. The famous one gun Whirlwind was the test rig for this, not a single large caliber gun.

About the only thing it proved was that there was space/volume/balance to fit 4 guns and a lot more ammo.

 

[Shortround6]

Beard radiator?

 

[yulzari]

I cannot comment upon the best source for P38 but The Westland Whirlwind British fighter aircraft of WW2 covers much ground for the Westland Whirlwind. Lightning I for RAF goes over the ground for the RAF and Armee de l'Air Lockheed Lightning Anglo-French Purchasing Committee.

In terms of single seat pure fighter roles these were the leading active service types with most of the rest of twin engined fighters being in the two+ seater 'heavy' fighter class.

 

[Shortround6]

Whirlwind radiator was a very poor example using the only available radiator type that would fit at the time of design

Something stupid like using 3 "standard radiator No 10s" or other nonsense. They KNEW they could fit in a rectangular radiator with at least 20% more cooling capacity in the same space. But that would require a custom radiator and not off the shelf parts.

 

[Shortround6]

Getting back off the Whirlwind for a bit we have the earlier mentioned Gloster F.9/37

RR Peregrine engines with beard radiators.
and the infamous near vaporware Bristol Taurus engines.
With the Peregrines the speed was around 330mph at 15,000ft.
After the first radial engine plane crashed and was rebuilt with a later model Taurus engine the performance dropped by 25-30mph and no Taurus engine ever made that kind of of power at 15,000ft again.
More photos here

Gloster F9/37

The Gloster F.9/37 (also known as the Gloster G.39) was designed to meet specification F.9/37 which called for a twin-engine, two-seat day and night fighter. The aircraft that emegered from the Design Team, led by W.G. Carter, was a twin-engine monoplane bearing more than a passing resemblance...

ww2aircraft.net

You have a 386 sq ft wing which could be cut down.
changing to Merlins may require quite a bit of modification. Not impossible but using heavier engines that far forward harder than doing it further back.
Plane was also under 12,000lbs gross as built so heavier armament, heavier engines and more fuel also needs work.

Early P-38s went around 15,000lb with 300 US gallons of fuel and only 200rpg for the four .50 cal guns and 150rounds for the single 20mm.
Granted no Turbos in our British twin engine fighter but..............Going to Merlins and 3-4 20mm guns is going to run up the weight.

 

[yulzari]

View attachment 798710
The guns were not belt feed. They had a magazine with a number of vertical columns that feed downwards and a feed system to push the rounds across the bottom of the magazine to the gun. It was powered by compressed air. Unfortunately the thing used many times the amount of air originally estimated and existing air tank and compressor could not keep up with one gun for very long let alone 4 guns. The famous one gun Whirlwind was the test rig for this, not a single large caliber gun.

About the only thing it proved was that there was space/volume/balance to fit 4 guns and a lot more ammo.

Quite so. See The Westland Whirlwind British fighter aircraft of WW2 for the Hydran magazine system. However the Chatellerault belt system was the one that was actually to be used if a developed Whirlwind ever came to be.

 

[Reluctant Poster]

Beard radiators? Has any RR inline been so equipped? Surely the smaller Spitfire-like underwing rads would suffice? Or how about something like the P-38s?

Rolls Royce fitted a Mosquito with beard radiators and their tests found no determinantal effect on performance

 

[tomo pauk]

Beard radiator?

Fairey aircraft, like the Battle, Fulmar and barracuda were also outfitted with beard radiator.
So were the Merlin-powered versions of Beaufighter, Halifax and Lancaster.

You have a 386 sq ft wing which could be cut down.
changing to Merlins may require quite a bit of modification. Not impossible but using heavier engines that far forward harder than doing it further back.
Plane was also under 12,000lbs gross as built so heavier armament, heavier engines and more fuel also needs work.

Early P-38s went around 15,000lb with 300 US gallons of fuel and only 200rpg for the four .50 cal guns and 150rounds for the single 20mm.
Granted no Turbos in our British twin engine fighter but..............Going to Merlins and 3-4 20mm guns is going to run up the weight.

There is no doubt that weight will go up in the steep fashion with Merlins installed, but the resulting A/C it will not be the barn door like it was the Beaufighter. And probably less of a problem for it if/when enemy fighters are encountered.

 

[Admiral Beez]

Just about every airplane is a compromise

Some more than others. What did the P-51D compromise?

 

[Howard Gibson]

Some more than others. What did the P-51D compromise?

The big gas tank in the rear make flying awkward. The Mustang was overweight compared to the Spitfires. Was four or six guns the correct armament? Also, I don't like the colour of this one.