Best Whirlwind armament layout to fight Japanese fighters and bombers?

[Admiral Beez]

it was said of the R-R engineers that they were nothing special in terms of engine design, but were absolutely terrific at engine development.

Totally understandable as you don't need to be producing two V-12s (though they did end up that way by 1943 with the Merlin and Griffon) but it's a shame we didn't see what RR could have developed the Whirlwind's Peregrine into.

 

[yulzari]

Long ago I spoke with a Westland engineer who described the 12 x .303 as being able to 'saw a fuselage in half' with the concentrated fire.

 

[Shortround6]

Totally understandable as you don't need to be producing two V-12s (though they did end up that way by 1943 with the Merlin and Griffon) but it's a shame we didn't see what RR could have developed the Whirlwind's Peregrine into.

Just about an 80% Merlin at any given moment (fuel and parts needed to stand up to the power) which kind of shows why it went away. A hot rod Peregrine was going to roughly equal a plain Jane Merlin so any airframe that would hold the Merlin was better off with the Merlin.

 

[wuzak]

Exactly. As I understand it, higher-octane fuel has little effect by itself, its value is that it permits higher boost pressures to be used.

I recall reading that the Merlin engine went through its entire development process using the same valve timing and compression ratio: all of the increases in power (which doubled from 1939 to 1945) were due to the boost pressure being turned up as higher-octane fuel became available.

Late war Merlins could cruise at +7psi boost, whereas pre-war and early war Merlins (on 87 octane fuel) had a 5 minute limit of around +6psi boost.

Such was the development during the war, especially with the improvement with fuels.

 

[Shortround6]

Merlin type........................................III...............................XII....................45.............................XX
Full power boost+RPM......6 1/4/12+3000........12+3000.........16+3000...........14/16+3000
Climb Boost + RPM................6 1/4+2600..............9+2850............9+2850.................9+2850
Max cruise Boost+RPM........4 1/2+2600 ............ 7+2650............7+2650.................7+2650

However a Merlin 45 running at 6lbs boost and 2650 rpm was burning 70imp gallons an hour so a frequent look at the fuel gauge was needed.

 

[Ascent]

Thanks, I've been wondering how the octane alone made a difference. My turbocharged car requires 91 octane, and AIUI if I put in 95 or even 100 octane fuel it makes no difference in power with the stock setup, beyond paying more for marketing gimmicks at the gas station. But, if I could adjust the boost level like our Whirlwind pilot can, the higher octane makes more power. Now I understand, I think.

An engine designed to use a lower octane fuel will gain no benefit from a higher octane rating however an engine designed to use a higher octane fuel will lose power when using a lower octane fuel due to changes in ignition timing and boost levels.
At least in modern vehicles where the ECU controls everything.

 

[stona]

I'm not one for 'what iffery' but I will say that whatever you decide must include cannons.

We know from the data of the Spitfires sent to Australia that it took, on average, nine gunnery passes to down a Japanese aircraft. There are several reasons for this, the poor marksmanship common across the RAF/RAAF being one, but there is no doubt that the consistent failure of the cannon to fire reliably was also significant.
The cannon usually stopped firing after a few opening rounds at relatively long range. By the time the Spitfires closed to close range they were spraying the general area of the target with four .303 calibre machine guns to little effect.
It's the reason that Caldwell, whatever his faults, sensibly argued for .50 calibre machine guns in place of the cannon on the Spitfire squadrons. This was totally impractical at the time and in Australia, but he was right that it would have been better than what they had.

 

[Admiral Beez]

An engine designed to use a lower octane fuel will gain no benefit from a higher octane rating however an engine designed to use a higher octane fuel will lose power when using a lower octane fuel due to changes in ignition timing and boost levels.
At least in modern vehicles where the ECU controls everything.

I belong to a vintage motorcycle club, and so many of the chaps think they're doing their old Triumph or whatnot a favour by using the high octane fuel, usually marketed as "super premium" or thereabouts. But these higher octane fuels do nothing for our low compression engines and with their higher ethanol content these high octane fuels may rust out our fuel tanks and corrode the fuel system. For my own 1980's Suzuki I put in 87 octane unless I'm storing the bike, then it's 91 octane because that's the level at Petro Canada that claims to be ethano-free. The higher 91 octane is useless to me otherwise.

 

[PAT303]

I'm not one for 'what iffery' but I will say that whatever you decide must include cannons.

We know from the data of the Spitfires sent to Australia that it took, on average, nine gunnery passes to down a Japanese aircraft. There are several reasons for this, the poor marksmanship common across the RAF/RAAF being one, but there is no doubt that the consistent failure of the cannon to fire reliably was also significant.
The cannon usually stopped firing after a few opening rounds at relatively long range. By the time the Spitfires closed to close range they were spraying the general area of the target with four .303 calibre machine guns to little effect.
It's the reason that Caldwell, whatever his faults, sensibly argued for .50 calibre machine guns in place of the cannon on the Spitfire squadrons. This was totally impractical at the time and in Australia, but he was right that it would have been better than what they had.

Of the 100 pilots that flew with 1st wing over Darwin only 6 had ever seen combat, when you add up everything, the lack of experience, poor reliability, low boost engines, no spares, unreliable guns, poor quality ammunition and a 100 other things using Darwin as an example of armament effectiveness is not really a good idea, and the .50's would have been just as unreliable because they still jammed in a turning fight, and it took till late '43 to get specialised ammunition into mass production.

 

[stona]

Of the 100 pilots that flew with 1st wing over Darwin only 6 had ever seen combat, when you add up everything, the lack of experience, poor reliability, low boost engines, no spares, unreliable guns, poor quality ammunition and a 100 other things using Darwin as an example of armament effectiveness is not really a good idea, and the .50's would have been just as unreliable because they still jammed in a turning fight, and it took till late '43 to get specialised ammunition into mass production.

They were typical of RAF and Commonwealth squadrons at the time. There is no reason to believe other squadrons would have done any better. Poor gunnery was a problem across the RAF.

What the Whirlwind needed was reliable cannon armament, so that when the few pilots who could actually hit a cow's arse with a banjo did close with a target they could shoot it down. Throughout most of the war a very small minority of pilots shot down a large majority of enemy aircraft. In the Battle of Britain just 17 pilots accounted for more than 200 of the Luftwaffe aircraft claimed. In Australia it would be perfectly normal for a handful of the pilots on those three squadrons to account for enemy aircraft destroyed, but they would have shot down a lot more with reliable weapons, preferably cannon.

 

[PAT303]

They were typical of RAF and Commonwealth squadrons at the time. There is no reason to believe other squadrons would have done any better. Poor gunnery was a problem across the RAF.

What the Whirlwind needed was reliable cannon armament, so that when the few pilots who could actually hit a cow's arse with a banjo did close with a target they could shoot it down. Throughout most of the war a very small minority of pilots shot down a large majority of enemy aircraft. In the Battle of Britain just 17 pilots accounted for more than 200 of the Luftwaffe aircraft claimed. In Australia it would be perfectly normal for a handful of the pilots on those three squadrons to account for enemy aircraft destroyed, but they would have shot down a lot more with reliable weapons, preferably cannon.

You fight with what you have, no cannons were reliable in 1940, same for the .50, so you pick the best weapon the RAF had which was the .303. The BoB proved that no plane is going to survive a solid 2-3 second burst from eight .303's, twelve is going to do it quicker. The Browning's were very reliable, fired effective reliable specialised air to air ammunition and importantly were light, people forget that, with only around 1100 hp available weight plays a big factor in weapon selection.

 

[A.G. Williams]

What the Whirlwind needed was reliable cannon armament, so that when the few pilots who could actually hit a cow's arse with a banjo did close with a target they could shoot it down. Throughout most of the war a very small minority of pilots shot down a large majority of enemy aircraft. In the Battle of Britain just 17 pilots accounted for more than 200 of the Luftwaffe aircraft claimed. In Australia it would be perfectly normal for a handful of the pilots on those three squadrons to account for enemy aircraft destroyed, but they would have shot down a lot more with reliable weapons, preferably cannon.

The Hispano experienced various problems in its early development and use, some were rectified fairly easily (e.g. a shortened chamber to ensure that the firing pin hit the primer with enough force to fire the round) but the most fundamental issue was that it was designed as a "motor cannon" firing through a hollow propeller hub. This meant that it was designed to be bolted to the engine which provided it with very rigid support - support which was missing in wing-mounted guns. Each wing installation therefore had the mounting "fine-tuned" for that particular model of aircraft. Fuselage-mounted guns like the Whirlwinds' and the Beaufighters' tended to be more rigidly supported so probably caused fewer problems (although I don't have any data on that). For the P-38 the US designed a rigid mounting.

After much reflection on all this I have concluded that the RAF buying the Hispano was a mistake, simply because it took so long to develop and de-bug the gun that it was not ready when it was needed most - for the Battle of Britain. Hindsight suggests that one of the Oerlikons would have been a better choice - on paper they had an inferior performance, but were fully developed and very reliable, plus smaller and lighter than the Hispano. My choice for the RAF would have been the mid-sized FFL (only really used by the Japanese Navy aircraft, as the Type 99-2). This fired at 500 rpm instead of 600 but weighed only 33 kg compared with 50 kg for the Hispano, and the ballistics were close to the .303 MG's at c.750 m/s.

 

[tomo pauk]

You fight with what you have, no cannons were reliable in 1940, same for the .50, so you pick the best weapon the RAF had which was the .303.
...

There was a number of reliable cannons and .50s around in 1940, reliable and in service. Unfortunately, not for RAF, while USAAF was almost in the same bucket (granted, they didn't do the fighting in 1940), especially with regards to cannons. Japanese were also behind the curve in 1940.

 

[stona]

S/L Munro was sent to the first Whirlwind squadron, charged with the task of 'persuading the cannon to fire without continual stoppages'.

The Hispanos had a habit of stopping after just a few rounds, and when they did fire, the blast wave buckled the nose cone. This fairing was initially made from aluminium sheet over duralumin formers, but thicker sheet and the addition of duralumin blast tubes quickly solved this problem. The stoppages took a little longer. S/L Munro was the ideal man for the job as he had written the original armament installation specification for the aircraft, and it was on his instructions that P6970 and subsequent aircraft fired their cannons pneumatically not hydraulically as originally designed.

On a different note, relevant to the original question, the Air Ministry judged Westland's design for the 12 machine gun nose to be 'unsatisfactory and unsafe', so that is probably not an option. Martin Baker mocked up a much better installation, but the project was dropped before it went beyond that.

 

[PAT303]

There was a number of reliable cannons and .50s around in 1940, reliable and in service. Unfortunately, not for RAF, while USAAF was almost in the same bucket (granted, they didn't do the fighting in 1940), especially with regards to cannons. Japanese were also behind the curve in 1940.

What cannons in 1940 were reliable?

 

[tomo pauk]

What cannons in 1940 were reliable?

Already in 1930s: Oerlikon 3 different lines of cannon - F, L and S, Shvak. In 1939: MG FF (Oerlikon FFF spin-off), HS 404. In 1940: MG FFM, Japanese Type 99-1 (Oerlikon FFF licence). In-service types listed.

 

[Admiral Beez]

What cannons in 1940 were reliable?

IIRC, the Bf 109E's MG FF cannon were one of the most reliable of 1940.

 

[PAT303]

Already in 1930s: Oerlikon 3 different lines of cannon - F, L and S, Shvak. In 1939: MG FF (Oerlikon FFF spin-off), HS 404. In 1940: MG FFM, Japanese Type 99-1 (Oerlikon FFF licence). In-service types listed.

All of them could not use full drums because they jammed, the MG in particular could only be loaded with 55 rounds and had to be updated to FF/M standard to get some hope of reliability. None of the 20mm ammunition worked, it either had faulty fuzes or the body castings were faulty, the original 1940's cast bodies turned to dust or unequal sized chunks when they detonated, all had low firing rates and low velocity especially the Type 99, the MG FF/M were considered obsolete after the BoB, the Type 99 only soldiered on because the A6M couldn't carry anything better. The effectiveness of 1940 cannons is best illustrated by the fact every plane that had them also carried MG's so the pilots had guns with more than 7-9 seconds of firing time that worked. If the Whirlwind went to war in 1940 stick to 12 .303's loaded with as much AP, Tracer and incendiary that it can carry.

 

[Admiral Beez]

If the Whirlwind went to war in 1940 stick to 12 .303's loaded with as much AP, Tracer and incendiary that it can carry.

How about just four .303 in the nose and tons of ammunition? The concentrated fire of four .303 should kill anything flying in 1940.

 

[tomo pauk]

All of them could not use full drums because they jammed, the MG in particular could only be loaded with 55 rounds and had to be updated to FF/M standard to get some hope of reliability. None of the 20mm ammunition worked, it either had faulty fuzes or the body castings were faulty, the original 1940's cast bodies turned to dust or unequal sized chunks when they detonated, all had low firing rates and low velocity especially the Type 99, the MG FF/M were considered obsolete after the BoB, the Type 99 only soldiered on because the A6M couldn't carry anything better. The effectiveness of 1940 cannons is best illustrated by the fact every plane that had them also carried MG's so the pilots had guns with more than 7-9 seconds of firing time that worked. If the Whirlwind went to war in 1940 stick to 12 .303's loaded with as much AP, Tracer and incendiary that it can carry.

No need for changing the goal post, you didn't asked for ammo supply (Oerlikon was offering belt-fed cannons for RAF years before ww2; Shvak was belt-fed) or firing rates to match LMGs (cannons have shells that offer order or two of magnitude better effect on target than LMGs). You claimed that there were no reliable cannons (and HMGs) in 1940 - and that was not the case.