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Comment by nescioquid | Hacker News Reader

Serious question: why not just move the guns so they do not shoot through the props?

I've always assumed there was a reason for it that required solving the engineering problem in the first place. But now I wonder whether it was just simply easier to invent the 'sync gear' than deal with whatever problems ensue from moving the guns.

> Sync gear, also known as an interrupter or gun synchronizer, was developed during World War I to ensure that...

Was the sync gear an application or adaptation of an existing technique?

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> why not just move the guns so they do not shoot through the props?

You can mount guns in the wing, as seen on many WWII fighters, or run through the center of propeller shaft. These approaches have significant benefits, notably the rate of fire is not limited by propeller speed and number of blades, as well as having much more room to work with when wing-mounting (or the case of the P-39/P-63, having significant volume in the nose).

However, these approaches have some significant limitations, particularly for WWI-era aircraft. Most importantly, the wings of WWI aircraft were not strong enough to survive the stresses of mounting (and firing) machine guns. Wings of WWII and later metal aircraft are vastly stronger than the early wood, fabric, and wire bracing wings of most WWI aircraft. Through-propeller mountings are fundamentally incompatible with radial and rotary engines, and really only work with V-type inline engines. Relatively few WWI fighters were fitted with such engines. Also notable, wing-mounted guns must be angled inwards to converge at a desired range, and to be effective a pilot wants a gunsight that helps them estimate range to target. Such gunsights didn't exist in WWI, and so fuselage-mounted guns are easier to aim with basic sights.

Because if the gun is mounted on the centerline of the aircraft, it's more natural for the pilot to aim. Also, you can fire out to the full range of the ammunition.

Guns mounted on the wings had to be canted inward so that their pattern of fire intersects at some distance in front of the aircraft, so you only get the full firepower of all your guns at or around that specific range.

https://en.wikipedia.org/wiki/Gun_harmonisation

Guns mounted on the wings will increase the roll moment of inertia, making the airplane less agile.

I think a real consideration is how fragile those early airplanes were. Machine guns are heavy, their ammo is heavy, and you need heavy mounts to absorb the recoil of firing them. The wings of WW1 fighters are basically made out of toothpicks and tissue paper (an exaggeration, but not by much). I wouldn't be surprised if they simply couldn't handle the load of wing mounted guns.

Three reasons, 1) Easier to line up barrel with target, 2) Easier to clear jams especially given the colder air temperature at altitude (up to 12k feet), 3) Easier to replace belt when out of ammo with a box of ammo behind the pilot.

Much easier aiming if its at the center (like no ""focal point""), and then the early ones also had only one, balance! But both uneducated guesses.

focal point: not sure if its the right term here, what I mean is: If you put the guns far to the side and still let them shoot straight you have drastically reduced the chance to hit a plane flying in front. And if you point them inwards you have only one good distance (where bullets cross, like focal point) where you hit well.

> why not just move the guns so they do not shoot through the props?

Some did do just that.

With the British Foster mounting[0] variants of the S.E.5a, Sopwith Camel and Nieuport fighters mounted their guns over-wing and above the arc of the propeller. Convergence issues still apply here, as noted by the other comments.

[0] https://en.wikipedia.org/wiki/Foster_mounting

My guess: it's easier for the pilot to aim a gun that he's sitting directly behind. If the guns were mounted under the wings or whatever, it would be much harder.

Old aircraft had the gun on a rail above the prop. To reload the gun or clear a jam, the pilot had to pull the gun down a rail, reload it, and push it back up. This was difficult to do during a dogfight.

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