Best Whirlwind armament layout to fight Japanese fighters and bombers?

[ThomasP]

Hey guys,

For the RAF which belt-feed are we talking about? IIRC the Hurricane IIC (mid-1941) used a form of recoil assisted feed mechanism, and I do not recall reading of any particular problems with it. It only had to feed a 94-round belt vs the later 120-round belt for the Spitfire VC (late-1941) and such, but was there any particular problem with either?

 

[tomo pauk]

We're talking about belt feed for cannons, pros and cons of it.

 

[Admiral Beez]

What about 6 or 8 .303's? Like Beez said, I doubt any Japanese aircraft except a large flying boat ever came home with 300+ bullet holes in it, especially if incendiary rounds are plentiful.

Japanese home builders and aircraft manufacturers of the prewar era seemed to follow the same materials and building techniques. Keep it dainty, light and highly flammable.

 

[Shortround6]

Hey guys,

For the RAF which belt-feed are we talking about? IIRC the Hurricane IIC (mid-1941) used a form of recoil assisted feed mechanism, and I do not recall reading of any particular problems with it. It only had to feed a 94-round belt vs the later 120-round belt for the Spitfire VC (late-1941) and such, but was there any particular problem with either?

Once you have a decent belt feed you can make it in any capacity you have the room (volume) and weight lifting capacity for (with in reason)
Beaufighters used up to 283 rounds per belt.
Typhoons used 140 rounds per belt.
Mosquitos used 150 round belts.
The belt feed mechanism (and de-linker) was pretty much the same on all the installations.

The drum like devices are the belt feeds/de-linkers.

 

[Reluctant Poster]

It may have been made by them and/or final development made by them but the basic design came from France, the Chatellerault feed. The plans were actually gotten out of Paris in May of 1940?

The Martin Baker feed was a later design used in later production Seafires. See the following link posted by NeedySeaGoon back in October.
Halton 81st Entry
The MB5 also used the MB feed. See the following cutaway:
https://i.pinimg.com/736x/e3/ac/63/e3ac637131a5a772947476ffcc67023a.jpg

 

[ThomasP]

Hey Shortround6 and Reluctant Poster,

Thanks for the info on the belt-feeds.

I do not know for sure which aircraft also used the servo-assisted feed mechanism other than the Beaufighter, but if you have any technical information or diagrams on it I would be interested.

 

[PAT303]

When belt feed was available, people used it. Nobody was using it before it was available.

Was the Whirlwind in operational use when belt fed Hispano's reached front line fighters?

 

[PAT303]

Hey Shortround6 and Reluctant Poster,

Thanks for the info on the belt-feeds.

I do not know for sure which aircraft also used the servo-assisted feed mechanism other than the Beaufighter, but if you have any technical information or diagrams on it I would be interested.

Same here, good info.

 

[ThomasP]

Yes, Whirlwind operational life was from late-1940 to late-1943. The recoil assisted feed mechanism entered service with the Hurricane IIC in mid-1941. Maybe a little earlier in the Beaufighter? [edit: I have not been able to find any solid info on when the first Beaufighters switched over to the belt-feed system(s).]

 

[A.G. Williams]

That would be all rounds fired including the misses, there's not an aircraft made anywhere in the world that would be in a flyable state after having 4,500 AP and incendiary .303's fired into it.

Yes, of course. I've not seen any figures for the percentage hit rate achieved in the BoB, but later in the war the Luftwaffe found that only around 5% of the cannon rounds fired at large bombers scored hits.

 

[A.G. Williams]

I suggested the very same thing and got roasted for it, if I flew in WW2 I'd have my Spit set up exactly as you described, use short bursts from the .303's until I saw the flash then toggle the switch and let the SAPI's go to work.

The problem with that is that while the .303's muzzle velocity was around 750 m/s, the Hispano's was 880 m/s. Which could mean that relying on the MGs to indicate the correct lead angle to hit a target might result in a clean miss with the cannon.

 

[tomo pauk]

Was the Whirlwind in operational use when belt fed Hispano's reached front line fighters?

Yes, already a year.

 

[Shortround6]

[edit: I have not been able to find any solid info on when the first Beaufighters switched over to the belt-feed system(s).]

I seem to remember that one book said the first 400 Beaufighters used drums. I don't know if that is exact or not, or how long it took to build the first 400 Beaufighters. Or even if that is accurate.

 

[Shortround6]

The problem with that is that while the .303's muzzle velocity was around 750 m/s, the Hispano's was 880 m/s. Which could mean that relying on the MGs to indicate the correct lead angle to hit a target might result in a clean miss with the cannon.

It may mean a clean miss even using Oerlikon guns depending on range and firing angle.

The basic problem with trying to use MGs as sighters for cannon is that the observed tracers and/or strikes tell you where you should have been aiming a fraction of a second ago.
Tie that in with most pilots were doing good if they had a reaction time of under 0.20 seconds.
So our intrepid pilot (using German MG 131 round of 750m/s) fires at target, time of flight to 300 meters at sea level is 0.453 seconds, after a period of time firing he sees strikes (from rounds fired 0.45 seconds before) it takes him 0.2 seconds to trigger the cannon, (117gram shell from MG 151/20) takes 0.477s to cover the same 300 meters distance. (the 3rd digit is not worth dealing with and even the 2nd digit needs a bigger difference than .02-.03).
A 300mph plane is covering 134 meters as second so the target plane will have moved (0.2 sec +0.47 seconds x 134 m/s) 89.78 meters from when the pilot saw the mg bullets hitting to when the cannon shells arrive. Firing plane, if also doing 300mph will cover 89.78 meters in the same period of time.

Longer ranges get worse much quicker.
Higher altitudes have shorter flight times but the reaction time stays the same.
Short ranges quickly diminish the need for "ranging" shots. The times of flight get much shorter even if the reaction time stays the same( 300mph plane covers 26.8 meters during the reaction time or almost 3 airplane lengths for a small fighter.) a 200mph plane will cover 17.9 meters.

A number of pilots may have tried to use this technique but it may require a fairly stable firing solution (like a tail chase) to be successful. Large angle defection shots and closing shots have th eranges and leads changing too fast.

Flight times from Page 52 of "Flying Guns World War II." By A.G. Williams and Dr Emmanuel Gustin.
Any other math errors are mine.

 

[Greyman]

In practice, the .303 MGs proved disappointing in the BoB, which is why the RAF was so desperate to fit cannon even before they were ready. Luftwaffe bombers made it back to base with as many as 300 bullet holes in them.

Probably the worst way to get my point across -- but I think a fair amount of this is 'a poor workman blames his tools'. The flight and gunnery training for RAF fighter pilots was at its absolute nadir at this stage of the war. While reading memoirs / anecdotes of this period you can't help but stumble across this type of thing time and time again. From Alan Deere's book:

Pilot Officer Mick Shand, who came to my flight, certainly looked promising until I learned the grim details of his flying experience ... ​

"Hello," I said greeting him at dispersal that afternoon. "I hear you're a fellow countryman of mine."​

"Too right, and glad to be here," was the cheerful rejoinder.​

"What flying experience have you got?"​

"I've got a total of 140 hours approximately, mostly on Wapitis. I only managed to get twenty hours on Spitfires at OCU and it was hardly enough to get the feel of flying again after two months' lay off. As a matter of fact I know damned all about fighters, I was trained as a light bomber pilot."​

"Have you fired the guns in a Spitfire yet?"​

"No, I haven't; apart from a very little free gunnery from a rear cockpit, I've no idea of air firing."​

"What about the reflector sight, do you understand it?"​

"Haven't the remotest idea what it is, much less understand it."​

"Good grief," I thought. "It does seem a shame to throw him into battle so soon." There was no alternative, and certainly no time or aircraft to fit in any further training ... This was typical of the replacement pilots arriving in the squadrons, desperately keen to get cracking but all lacking in basic flight experience.​

​

To me this doesn't strike me as a good environment to judge things. Hurricane night fighters repeatedly proved that eight .303s were perfectly capable of downing a Heinkel with a 1-2 second burst at very close range.

Now I'm not suggesting switch to heavier calibre guns wasn't the correct move to make, but I don't think eight .303s was a bad armament at all in 1940.

According to operational research, the percentage of successful combats rose steadily throughout the war. I don't have figures from the period in question, but in the Spring of 1942 the average closing distance in combat was 570 yards with 12% of attacks being successful. Only 4.5% of attacks were closed to under 200 yards, with 62.4% not even closing to within 600 yards.

By the winter of 1943 the average closing distance was 331 yards and 27% of attacks successful.

By the end of the war this was down to 280 yards and 54% of attacks successful.

Of course there are other reasons for this increase in lethality, but firing range seems to be the major factor in every time period.

Quite a change from 1942 to 1945 considering the Spitfire's armament didn't change all that much (I left out gyro sight figures from my 1945 totals). I think if the '40 RAF had the luxury of '45 RAF training, tactics, etc. -- the .303 Browning wouldn't have been maligned so much.

 

[A.G. Williams]

Lots of issues over fighter armament being raised here, and some good points being made. A few additional comments:

The use of MGs as "sighters" for the cannon was likely to prove more useful against bombers than fighters, since the tactical situation did not change so rapidly - a small fighter jinking to avoid fire is a very different target from a bomber on a steady course.

In tests involving shooting at a Blenheim on the ground, incendiary bullets (both .303 and 7.9 mm) were only effective in about 10% of hits in the fuel tanks (the .303 Mk VI raised that to 20%). AP bullets were even less effective. On paper, they could penetrate around 10-12 mm armour plate, but in practice they were destabilised on hitting the aircraft structure to such an extent than only a minority of hits even reached the Blenheim's 4 mm armour plate, and hardly any penetrated. The firing tests were at 200 yards.

The vulnerability of the aircraft used in the BoB changed during the course of the Battle, with armour plate being added in the field (both sides did this, I believe). The .303 MG armament presumably therefore became less effective during the course of 1940.

 

[PAT303]

On paper, they could penetrate around 10-12 mm armour plate, but in practice they were destabilised on hitting the aircraft structure to such an extent than only a minority of hits even reached the Blenheim's 4 mm armour plate, and hardly any penetrated. The firing tests were at 200 yards.

During the very same tests the .50 Browning rounds behaved the same, people are very quick to point out that the .50 can penetrate 25mm or so of armor at 90 degree's at 100m, when shooting at the same Blenheim the bullets hit at oblique angles causing them to also tumble, I used to have a photo of the plate and most of the hits were keyholes.

 

[SwampTiger]

As the OP raised the issue of effectiveness versus JAPANESE aircraft, I must go with the 8-12 .303 armament through 1942, and possibly 1st half of 1943. The lack of SSFT and armor left these opponents vulnerable to even tumbling solid projectiles.

The discussion of the cannon armament is fascinating. However, these are not needed till later in the war.

 

[PAT303]

As the OP raised the issue of effectiveness versus JAPANESE aircraft, I must go with the 8-12 .303 armament through 1942, and possibly 1st half of 1943. The lack of SSFT and armor left these opponents vulnerable to even tumbling solid projectiles.

The discussion of the cannon armament is fascinating. However, these are not needed till later in the war.

They were never needed, a good 2-3 second burst of 8-12 .303's had them flaming, I'd go for more fuel and ammo than bigger guns when fighting the Japanese, and greater effort improving gun sight technology.

 

[Graeme]

there was no 37mm gun. The gun in the photos of a single gun Whirlwind is a 20mm Hispano. What they were testing seems to be lost in time.
A number of books and many websites say the gun is a 37mm but the British had no 37mm gun in development at any of the British gun companies or government arsenals.
37mm was not a standard British gun size and no other British gun in several decades was a 37mm. (except for purchased guns). British had a variety of 40mm guns (2pdrs).

So, Commando Comics LIED to me all those years ago?

(In the story, the Whirlwinds are based in Russia. )