gun synchronization to fire through propeller arc

[kennethklee]

Originally Posted by martin66

hello

I remember an article in aviation magazine when Adolf Galland said in an interview he prefered the Bf -109 over the Fw-190 because the guns of the Messerschmitt was less prone to jamming in high g. factor maneuvres.

I think the cause is the wing guns of the FW-190 were more far of the centre of gravity of the plane and they had problems with the feeding of ammo in high g conditions than the nose guns of the Bf-109.

Martin

Originally Posted by kurlannaiskos

well, how could I have gotten that wrong?
oh , I know-I usually concentrate on the cannon armament.
(my favorite is the NS-37)

however that website also still uses old and inaccurate designations like Yak-1M , Il-2M and Il-2M3.
these are not the correct Soviet designations , but a largely typographical error in those cases.

Martin--good point, I had forgotten that outboard guns are more prone to jamming. I can't recall the source, but I also recall reading commentary from an American pilot stating this (IIRC, he was comparing the wing armament of the P-51 Mustang to the centerline guns of the P-38 Lightning).

kurlannaiskos--I had forgotten about the 37mm guns carried by the later models of the IL-2, quite formidable. I find interesting that as the IL-2 progressed and eventually evolved into the IL-10, the two 7.62mm machine guns remained steady and were not upgraded to 12.7mm or even 20 mm cannon. I suppose the machine guns were not regarded as primary armament and were used primarily for their tracer ammunition? Do you know the IL-2 with the 37mm cannon performed compared with the 23mm-gunned versions? The installation of the IL-2 37mm cannon certainly appears more graceful than the underwing 37mm cannon of the Ju 87G-1. Your note also reminds me that I am not very familiar with the formal designation nomenclature of WWII Russian warplanes.

Thanks again,
Kenneth

[kurlannaiskos]

I did look into it a bit further and the machine guns were apparently for aiming purposes only.
...as you say the tracer rounds.
(I can't imagine the 7.62 would be effective on anything but infantrymen)

the 37 mm cannons were more effective against German Armor ,but the pilots found the effect on the aircraft to be sluggish handling and more effort to pull up after making an attack run.
there was also a problem with asymmetrical recoil causing the pilot more difficulty in aiming.

[kurlannaiskos]

well, how could I have gotten that wrong?
oh , I know-I usually concentrate on the cannon armament.
(my favorite is the NS-37)

however that website also still uses old and inaccurate designations like Yak-1M , Il-2M and Il-2M3.
these are not the correct Soviet designations , but a largely typographical error in those cases.

[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.

[kolya1]

One thing worth noting is that, although an uncommon occurence, failures of the synchronisation system did sometimes happen. I think the first FW-190A captured by the Soviets in repairable condition was a plane that had cut its own propeller while straffing ground troops after the synchronisation system failed (wether because of mecanical failure or external damage, I don't know...). I can't look over all my books for that kind of incidents, but if I remember well, this wasn't a unique case, and it did also occasionnally occur in other air forces...

Anyway, as Graham said it, any fighter design is born out of a compromise between opposing factors, the goal being to have the best overall efficiency. Hubert Zemke and other US pilots remembered the P-38 for clearly having the best armament among US WWII fighters, while on the whole, they considered the Mustang or the Thunderbolt to be better fighters. Typical example of contradicting requirements was the Bf-109, which had to sacrifice part of its aerodynamics when it was needed to increase armament and MG-17s were replaced by MG-131s...

BTW, does anybody know how did the German pilots react to another of the firepower increases, namely the use of nose-mounted MK-108 30mm instead of MG-151 20mm cannon ? As far as I understand it, this change did not penalise the performance of planes as much as the MG-131 bulges, or the wing mounted gunpods, but I didn't read anything the usefulness of it in the fliers' eyes. By way of comparison, the Soviet experience with big guns (even bigger but with a slower rate of fire) is rather diversified : I've read praise about the higher hitting power in air combat of the Yak-9T's or P-39's 37mm guns, but also criticism regarding their slower rate of fire, or limited ammunition supply...