WWII aircraft: How did machine guns/cannon fire through the airscrew?

Question

Given that WWII fighters were equipped with fairly standard blowback operated machine guns and cannon, what was the mechanism by which the shells avoided the propellor blades? I suppose this question applies mostly to Luftwaffe aircraft which had nose-mounted weaponry. A subsiduary question might be, why did allied aircraft always carry ordnance that deliberately avoided the issue? Sorry, but I'm just interested.

If the gun were interrupted by the passage of the propellor blade, the sequence of fire would also be interrupted and thus the automatic nature of fire (that the firing of one shell initiates the firing of the next) would be halted. I'm not trying to be funny, I just want to know how it works.

Answer 1

The problem started in WWI. When the air war started, they used to take pop shots at each other with hand guns. the first attempts to fire forward actually shot off the propellers.

When war came, the French Morane-Saulnier aircraft were among the first to fly over the trenches; a primitive method of firing a machine gun through the arc of the propellor, using bullet-deflecting steel wedges on the back of the propellor, was installed on Type L aircraft and later on the Type N. A revised Type N made its appearance in the summer of 1915, with the 80 hp Le Rhone engine now standard; it was immediately popular with French pilots but the 25 or so built were scattered among various escadrilles. The British bought another 25 'Bullets' and had moderate success against German observation planes until the introduction of the Fokker E series airplanes.

The German government forced Dutchman Anthony Fokker and Hugo Junkers to work together. This collaboration resulted in some famous early Fokker planes - Fokker gained further infamy with his synchronization gear invention that allowed the machine gun to be fired through the propeller, resulting in an air-superiority briefly known as the Fokker Scourge.

The device simply stopped the machine gum from firing as the propellar passed.

The famous Fokker Dr.I triplane was used by Manfred von Richthofen, the Red Baron, towards the end of his career, who achieved over a quarter of his 80 air combat victories in Fokker aircraft.

Fortunately for the Allies, two new British fighters were already in production which were a technical match for the Fokker, the Royal Aircraft Factory F.E.2b and the Airco D.H.2 ( Geoffrey de Havilland). These were both "pushers" and could fire forwards without gun synchronisation. The F.E.2b reached the front in September 1915, and the D.H.2 in the following February. On the French front, the tiny Nieuport 11, a tractor biplane with a forward firing gun mounted outside the arc of the propeller (on the top wing) also proved more than a match for the German fighter when it entered service in January 1916. With these new types the Allies re-established air superiority in time for the Battle of the Somme, and the "Fokker Scourge" was over.

Synchronised guns nonetheless quickly became the norm - and later versions of the Nieuport, as well as most new British fighters, were to be fitted with them for the rest of the war.

By WWII the machine guns had developed somewhat, and Britian used 8 machine guns that fired in a pattern the crossed at an intersection, or kill point 500 feet ahead of the plane. The need was for speed, and so they choose petrol engines with multiple propellars.

The main German bomber by comparison was built for long distance, and used diesel, with gun turrets. the fighters like the Me109E-3 which mounted two machine guns in the nose, and two in the wings. Provision for a cannon firing through the spinner was also made in the design, but due to heating and vibration problems, this was never used in action.

Answer 2

The older world war one system used a timing chain. I think the chain actually worked the gun mechanism. This system had gaps to interrupt the firing when a blade was in the way. This would not prevent the gun from firing the next round, it simply stopped the trigger for a fraction of a second. Once the blade was past, the trigger would be active again and the next round fired.

Since world war two planes had electrically fired guns, this interrupt was most likely one that bypassed the circuit, preventing the gun from firing.

However not very many planes still fired through the arc of the propeller during WW2. Most had wing mounted guns, and some had guns that fired through the hub of the propeller. So there's two possible systems, the old style timing chain directly to the gun, or an electrical interrupt.

Answer 3

Simply by having a geared synchronization with the propeller and firing mechanism. This limited the rate of fire to the propeller RPM, so as more advanced aircraft were developed, they mounted the guns away from the propellers for safety and to gain addtional firing speed to increase the number of rounds fired per minute. This kept accidental propeller damage down, and allowed bigger guns. The P-38 Lightning had dual engines, with the guns mounted in the pilot pod, so it was a much superior fighting aircraft, not having to compromise the firing distance where the rounds converged in wing-mounted guns on either side to a certain point ahead, it could just fire a concentrated fire from a center position.

- The Gremlin Guy, USA -

Answer 4

Well, the Allies did not carry ordnance that "avoided the issue"
1. It is not the volume of shells that go out the gun tube,it is the weight of the shells, that matter. Early British fighters carried up to 8 .303 rifle caliber Mg's which took a lot of bullets to make a kill, learning from this all later marks of Spits, Hurricanes carried a mix 2-4 20mm cannon and .50 cal Mg's in the wings, Typhoons, Tempests, Beaufighter,mossie etc. all carried cannons & MG's
2. US fighter's, well the P-39 (1935) started with a 37MM cannon firing through the spinner, later replaced with a 20mm, plus two MG's sycronized to fire through the prop, and 2 on each wing
The P-40 (1937) MG on both wings and cowl, later just .50's on the wing (up to 6), P-38 4 .50 cal MG +1 20mm cannon on the center pod of a twin engine fighter.
I can go on, but as the air-war progressed aircraft became heavier, could carry more ordnance, armor,fuel and packed a bigger punch. The luftwaffe added cannons under the wings of Me-109's FW-190's to attack heavy bombers, but there performance suffered, and the loss rate grew faster than they could replace experienced crews.
By the way wing mounted ordnance,if bore sighted correctly are just as effective as syncronized MG's and you can pack more ammo in the wings, than in the cowl over an engine.

Answer 5

Ww2 Machine Guns

Answer 6

one of the simplest mechanisms to protect the PROPELLER /airsceew/ from damage is the fire interruptor in the mechanical way - a small trigger - fire interruptor was in the way of bullets, and every time one of the propeller blades passed around, the blade pushed the "trigger" until the blade passed. this way it was not possible to shoot into the blade. kinda safety pin.

the more recent planes I suppose used similar mechanical locks, but already attached to the engineshaft. thus rate of fire could be phased with the proppeler blades and no harm is done to the proppeler.

German planes like Bf 109 used the hollow propeller center to use the big gun, cannon 30mm. the shaft was turning around the barrel. /briefly said/

Answer 7

They used an interrupter cam or gear. It was linked to the guns. When the propeller blades were directly in front of the guns, the guns would cease firing. Remember this was all happening so quickly that the guns did not appear to stop firing at all.

Answer 8

A simple interrupter gear or linkage. When the blades pass through that arc, it stops the guns from firing.

Answer 9

WW1 invention kept the gun from shooting off the prop it int erupted the shot when the prop was in the way

Answer 10

I'm sure this question has been asked and answered several times already... Why not use the available search features to find the correct answer to your question.