Nose mounted machine guns and cannon.

[NARSES2]

Been musing, so quick question.

When one looks at late 1930's and WWII aircraft armament you find that the French, Germans, Soviets and to some extent the US had mg's mounted above the engine and cannon firing through the prop boss. Now the UK seems to have given this up with the demise of the bi-plane fighter and moved to wing mounted weapons for its single engined fighters.

Does anyone know if this was doctrinal (a greater continuous weight of fire from the wings for instance) or simply a case of issues with newer more powerful engines and interrupter gear ? I did read somewhere a long time ago that the RAF was looking at the French interrupter gear on the Ms.406 but it didn't go any farther after the fall of France.

[Gondor]

You missed out the Japanese, who had engine deck-mounted guns on their Zero and probably others. I believe it was to allow for a greater weight of fire, especially as the specifications that led to the Hurricane and Spitfire called for more weapons than could be carried on top of the engine deck.

[NARSES2]

You missed out the Japanese, who had engine deck-mounted guns on their Zero and probably others. I believe it was to allow for a greater weight of fire, especially as the specifications that led to the Hurricane and Spitfire called for more weapons than could be carried on top of the engine deck.

Yup, brain was purely focused on the European theatre at the time.

Right, but it's still odd that the UK moved away completely from fuselage guns whilst most other countries maintained a mix of fuselage and wing mounted. The other oddity that's always hit me is the US's pre-War "habit" of having fuselage guns of different calibres. Must have been a nightmare for the armourers ?

Edited completely because my origional reply completely miss-understood Gondor's reply    I blame it on the Med's which tend to Zombify me  . Going back to the telly now.

[Thorvic]

Was is it to do with the format of the Merlin engine streamlined fuselages inspired by the Schneider racers?, Although the radial Gladiator had its guns on the side rather than the top of the deck,

[scooter]

I want to say it was for ease of convergence.  I may only be partly right.

[Mossie]

Spread and number of guns. Wing mounted allowed more guns and a greater probability of hit but less damage.  Nose mounted allowed greater concentration of fire and more damage but a lower chance of a hit. Pros and cons to both.

Nose mounted may also increase the drag slightly.

[Rick Lowe]

Maybe that more ammo could be carried in the wings?

[Charlie_c67]

I know that Russian pilots often had the wing guns removed for various reasons, one of which was the fact that having only nose guns meant you aimed the aeroplane at you target, hitting whatever was immediately in front of you rather than having to worry about bullet spread.

[PR19_Kit]

The RAF aimed the wing mounted guns so the shots all arrived at the same spot around 200 yards (I think...) ahead of the aircraft. So bullet spread wasn't an issue if it all worked.

[jcf]

Spread and number of guns. Wing mounted allowed more guns and a greater probability of hit but less damage.  Nose mounted allowed greater concentration of fire and more damage but a lower chance of a hit. Pros and cons to both.

Nose mounted may also increase the drag slightly.

Centreline nose-mounted MG and cannon have a higher probability of a damaging hit than spread out wing-mounted guns because deflection shots are much simpler with that layout. Wing-mounted guns have to be adjusted to converge at a given range, if the target is at exactly the right place the massed fire is most effective, inside or outside of the sweetspot means that the probability of a killshot drops, especially with rifle caliber ammunition i.e. .303, .30, 7.92 etc. Deflection shooting is also more difficult than with nose mounted armament. Which is one of the reasons why wing-mounted cannon armament became more common, over or under was less of an issue. The USAAF was the only airforce that stayed with an MG only armament for various reasons, primarily logistics in spite of claims that six to eight .50 was just as effective as cannon because of weight of fire. The reality is that with thousands of bombers and fighters in service all using the same ammunition the logistics trail was much simpler from factory to field if they stayed with the .50 M2. The USN however made the move to cannon later in the war, they wanted to be sure they knocked down the target. Also as the USN logistics train was very different swapping out .50 for 20mm wasn't as much of an issue and the USN was already used to sourcing and handling a broader range of ordnance.

As to synchronization it isn't that difficult even with the larger more powerful engines of the period. The Germans had the best approach, they used electrically ignited ammunition, the primer flashed when the circuit was closed.

[NARSES2]

Many thanks for your thoughts gents 

The RAF aimed the wing mounted guns so the shots all arrived at the same spot around 200 yards (I think...) ahead of the aircraft. So bullet spread wasn't an issue if it all worked.

Yup and some pilots had that reduced from what I've read in the past.

Overnight when my brain kicked in again I wondered if it was anything to do with the development of sighting equipment from the simple ring and bead to reflector sights ?

[Old Wombat]

Many thanks for your thoughts gents 

The RAF aimed the wing mounted guns so the shots all arrived at the same spot around 200 yards (I think...) ahead of the aircraft. So bullet spread wasn't an issue if it all worked.

Yup and some pilots had that reduced from what I've read in the past.

Overnight when my brain kicked in again I wondered if it was anything to do with the development of sighting equipment from the simple ring and bead to reflector sights ?

No, it came down to weight of fire.

In the early-mid-1930s the RAF realised that the 2 or 3 machine guns their existing fighters carried were no longer sufficient to significantly damage a modern bomber aircraft.

However they had not had much success with aircraft cannon (but were working on it) by the late-mid-1930s.

In the interim, they settled on 8 x .303 cal machine guns mounted in the wings & set to converge at a given range as being able to apply enough weight of fire to the target to have a reasonable chance of causing enough damage for what is now called a "mission kill".

Spinner-mounted machine guns/cannon were a no-go because the design of the Merlin (& later Griffon) did not lend itself to the various methods of achieving this.



You will note that the British mounted as much of the big-bang stuff on the centre-line of their twin-engined fighters as they could, as it made shooting significantly easier with exactly the same sighting systems as the single-engined fighters.

[NARSES2]

You will note that the British mounted as much of the big-bang stuff on the centre-line of their twin-engined fighters as they could, as it made shooting significantly easier with exactly the same sighting systems as the single-engined fighters.

Yup and went back to it when jet fighters came in

[Dizzyfugu]

I think this move was pragmatic. First of all there's only limited space around the engine, you need the gearbox to synchronize the weapons (= dead weight), and the vicinity to the engine might also cause problems. The biggest gun concentration around a single engine I remember is the Lavochkin La-9 with four(!) 23mm cannon above the engine. Moving all that to the wings reduces many problems, even though the extra weight far away from the CoG might be detrimental to handling/agility - but the win in firepower and simplicity overall would certainly outweigh this. The problem the British fighters (and also the bomber with their twin and even quad MGs) encounterd with their large light MG arrays was that these lacked weight of fire and impact to do serious damage with only a few hits - during the Korean war the USAF had the same experience with the F-86 against MiG-15 and Tu-4s.

[PR19_Kit]

Yup and went back to it when jet fighters came in

And then reverted to wing mounted guns, albeit cannon by then, when they fitted radar in the nose of the jets, viz. NF Meteors and Javelins.