gun synchronization to fire through propeller arc

[kolya1]

Originally Posted by Graham Boak

I suspect there were biplane fighters with 4 fuselage-mounted machine guns, although I can't think of one offhand. The Me 209-II had a similar wingroot mounting to the Fw series. The La 7 is nagging at me - there were versions with three cannon in the fuselage and others with either two or four. My books are temporarily out of reach.

Yes, there were effectively some biplane fighters with 4 guns firing through the propeller's arc : I can think of the Polikarpov biplanes : I-15, I-15bis, and I-153. The early models had PV-1 MGs while the late ones used ShKAS, which must have been quite difficult to synchronise, because of their very high rate of fire (1800 rounds/min unsynchronised). The MiG-3 also usually carried 3 guns in the nose above the engine (2 ShKAS, 1 UB). The La-7 had usually 2 ShVAK 20mm guns, but by the end of the war versions with 3 lighter B-20 guns appeared. The post-war La-9 and La-11 had 4 NS-23 23mm guns.

I don't know if that is among the reasons why some air forces favored wing guns and other fuselage ones, but I think I once read that Soviet pilots who fired at close range complained about the disposition of the Spitfire's armament. I suppose it's possible that air forces that emphasized deflection shooting preferred wing guns which covered a wider area...

[kennethklee]

Originally Posted by Graham Boak

I suspect there were biplane fighters with 4 fuselage-mounted machine guns, although I can't think of one offhand. The Me 209-II had a similar wingroot mounting to the Fw series. The La 7 is nagging at me - there were versions with three cannon in the fuselage and others with either two or four. My books are temporarily out of reach.

Originally Posted by kolya1

Yes, there were effectively some biplane fighters with 4 guns firing through the propeller's arc : I can think of the Polikarpov biplanes : I-15, I-15bis, and I-153. The early models had PV-1 MGs while the late ones used ShKAS, which must have been quite difficult to synchronise, because of their very high rate of fire (1800 rounds/min unsynchronised). The MiG-3 also usually carried 3 guns in the nose above the engine (2 ShKAS, 1 UB). The La-7 had usually 2 ShVAK 20mm guns, but by the end of the war versions with 3 lighter B-20 guns appeared. The post-war La-9 and La-11 had 4 NS-23 23mm guns.

I don't know if that is among the reasons why some air forces favored wing guns and other fuselage ones, but I think I once read that Soviet pilots who fired at close range complained about the disposition of the Spitfire's armament. I suppose it's possible that air forces that emphasized deflection shooting preferred wing guns which covered a wider area...

Kolya and Graham

Thanks for the information about the Russian WWII and post-war fighters. I certainly have overlooked the Russian fighters and their heavy reliance on synchronized guns firing through the propellor arc. I'm very impressed that the La-7 and La-9 could accomodate 3 or 4 23mm cannon in the fuselage and I can only imagine how powerful such a configuration would be.

Kolya, I think you are correct in that some pilots viewed wing guns has having too great a dispersal of fire and favored fuselage and engine-mounted guns for their concentration of fire. I recall Werner Moelders and perhaps Gerhard Barkhorn commenting they favored the concentrated fire of the Bf 109F's two fuselage-mounted machine guns and engine-mounted 15mm (increased to 20mm shortly) cannon, whereas Adolf Galland viewed this configuration as a regression from the 109E armament (2 fuselage machine guns, 2 wing cannon); I also recall that Galland felt that the majority of Luftwaffe fighter pilots did not have the marksmanship to take advantage of the 109F gun configuration.

Kenneth

[kennethklee]

Originally Posted by kolya1

Yes, there were effectively some biplane fighters with 4 guns firing through the propeller's arc : I can think of the Polikarpov biplanes : I-15, I-15bis, and I-153. The early models had PV-1 MGs while the late ones used ShKAS, which must have been quite difficult to synchronise, because of their very high rate of fire (1800 rounds/min unsynchronised). The MiG-3 also usually carried 3 guns in the nose above the engine (2 ShKAS, 1 UB). The La-7 had usually 2 ShVAK 20mm guns, but by the end of the war versions with 3 lighter B-20 guns appeared. The post-war La-9 and La-11 had 4 NS-23 23mm guns.

I don't know if that is among the reasons why some air forces favored wing guns and other fuselage ones, but I think I once read that Soviet pilots who fired at close range complained about the disposition of the Spitfire's armament. I suppose it's possible that air forces that emphasized deflection shooting preferred wing guns which covered a wider area...

Originally Posted by Graham Boak

I suspect there were biplane fighters with 4 fuselage-mounted machine guns, although I can't think of one offhand. The Me 209-II had a similar wingroot mounting to the Fw series. The La 7 is nagging at me - there were versions with three cannon in the fuselage and others with either two or four. My books are temporarily out of reach.

I have a trivial but perhaps interesting follow-up to the discussion about Russian fighters carrying more than 2 fuselage-mounted synchronized cannon: I just discovered today that the IL-2 Sturmovik 1946 WWII combat flight simulation game models several versions of the La-7 fighter, one of which carries three 20mm cannon in the engine cowling. The model seems visually accurate, down to the assymetrical configuration (2 on the left, 1 on the right) of the cannon. For those who are not familiar with this aerial simulation game, IL-2 is amazingly historically accurate in its attention to detail in the aircraft it models, some of which are historically obscure, as well as the simulation of combat flight.

Kenneth

[Jukka Juutinen]

Originally Posted by Harri Pihl

Finnish experience on wing vs fuelage guns appear to be rather contradictory. One of the first Fokker D.21s (FR-76) was ordered with 20mm Oerlikon canons mounted on gondolas below the wing. The installation was unsuccesfull, pilots reported poor accuracy, apparently the wooden wing was too flexible. However, later Fokkers with P&W Wasp Junior had only the wing guns (4x 7,7mm Browning).

The Myrsky had four fuselage guns (LKk 42 12,7mm) and the Pyörremyrsky as well as VL Humu had only the fuselage guns (all these featured wooden wing...). Also many war time pilots avdocated for fuselage guns; Juutilainen as example thought that inertia caused by wing guns is a bad thing.

One of the most succesful wartime weapon upgrades in Finland was wing gun related; the wing guns of the Brewster (Colt MG53) were replaced with the LKk 42. The LKk 42 had about twice higher rate of fire than the Colt and in the wing the LKk 42 could exploit this advantage fully because no synchronization was needed so the end result was about 50% higher firepower than before the upgrade.

Anyway, I agree pretty much with Graham; wing gun installations, even relatively weak, proved to be succesfull so apparently other factors are more important than location of the guns in the plane.

Did you base these comments on the Fokker and Humu articles in SIL? If so, where did you get the claim of poor accuracy of wing cannon in the Fokker case since the combat report quoted in the article does not claim that.

And according to the LKk 42 article it did not have "about twice" the rate of fire.

And Juutilainen clearly preferred fuselage guns. Juutilainen also noted that in the case of the other wing gun jamming, the asymmetric recoil ruined the aim. In fact, I have not encountered a single Finnish pilot report preferring wing guns. Have you?

As for the last statement, I wonder if 6 x HMG in wings would be Harri´s first choice in fighting e.g. the Il-2 or the B-29. In real life, not sims.

[PeterVerney]

While my experience is not strictly relevant to the thread, I'll stick in my two pennorth.
We had Mosquito night fighters with 4 fuselage mounted 20mm. We then upgraded? to the Meteor night fighter which had 2 20mm in each wing, mounted outboard of the engines.
We got lower scores on air firing exercises with the Meteor and particularly noticed stoppages as a problem. A stoppage meant abandoning the exercise because the yaw induced made accurate aiming impossible. Whereas on the Mosquito a stoppage had no effect, except for reducing the number of rounds fired which reduced the score.

[kennethklee]

Originally Posted by PeterVerney

While my experience is not strictly relevant to the thread, I'll stick in my two pennorth.
We had Mosquito night fighters with 4 fuselage mounted 20mm. We then upgraded? to the Meteor night fighter which had 2 20mm in each wing, mounted outboard of the engines.
We got lower scores on air firing exercises with the Meteor and particularly noticed stoppages as a problem. A stoppage meant abandoning the exercise because the yaw induced made accurate aiming impossible. Whereas on the Mosquito a stoppage had no effect, except for reducing the number of rounds fired which reduced the score.

Peter-

Thanks for sharing your flying and gunnery experiences with the Mosquito and Meteor. I find interesting that a gun stoppage on the Meteor would induce such yaw as to make accurate aiming afterwards impossible. (I assume this occurred because of the resulting assymetry of recoil of the remaining outboard guns firing.) I'm surprised that this would occur with a two-engined aircraft, I would think single-engined fighters would be more vulnerable to this. I haven't read of the gun stop-related yaw occurring in other fighters with outboard (i.e., wing-mounted) guns, but your experience induces me to wonder if it has.

Kenneth

[PeterVerney]

AAAH. What I forgot was that we only fired two guns. We carried 50 rounds per gun to make a total of 100. It was the only way pilots could calculate percentages ! No computers in those days, only computOrs, which we navs used.

[Graham Boak]

I don't think there is any argument that concentrating the guns in the nose is a superior solution from the point of view of aiming, or concentration of fire. However, with synchronisation being required it will produce lower rates of fire, and the other design compromises required may not lead to it being a superior solution overall. There's no such thing as a perfect WW2 fighter.

The choice of Finnish pilots is inevitably coloured by what they had available. They might well have preferred 4x20mm Hispano, had they the choice, despite having to accept them in the wings. It would also seem to be a superior armament against these hypothetical B-29s, than one or two cannon plus two machine guns.

[Jukka Juutinen]

So you´d prefer 4 cannon in wings rather than 4 cannon in the fuselage? And like it or not, e.g. Juutilainen (our top ace), considered the 109G-2 armament superior to the 4 HMG armament of the Buffalo. Yes, he preferred one MG 151/20+2 x MG 17 to 4 of those "magnificent" über-Brownings hailed by many American authors and their minions.

I once had a chance to examine the Hispano, ShVAK and MG 151 close up. The latter two were proper quality designs whereas the Hispano gave the impression of being hacked together by a third rate blacksmith with extremely crude finish all over and very clumsy weapon overall. Very much like the British "quality" of Ford Anglia or Vauxhall Viva.

[Graham Boak]

What is appropriate for a top ace and superb shot is not necessarily what works best for the wider number of wartime pilots. Some of the Russians also preferred the "sniper" approach, but it lead to the slow-firing heavy cannon of the Korean War period that were less than optimum.

I might prefer what I could get. 4xHispanos were available in 1941, in the wing of single-engined fighters or in the fuselage of twins. It is fair to say that it overloaded the 1930s generation of fighters, needing some 1500-2000hp to benefit, and for dogfights a lighter armament was better. However, you were the one who introduced the B-29 as the potential target! Please be consistent in your arguments.

The 4-cannon in fuselage Lavochkin was 1946, and used the much smaller lighter Russian cannon that did not appear until the very end of WW2. Nobody ever put 4 Hispanos into a single-engine fuselage. The Hispano was designed in the mid thirties: it is always possible to produce something better, ten years later.

As for quality standards, excessive quality in wartime production is a waste. This was normally very much the Russian approach, with high quality only applied where it was vitally necessary. After some development of the French original the Hispano worked: that's all that was needed. If the MG151 was "better" made, then it was worse made.