Mosquito (3)
The Hispano canon, while not used universally in aircraft (it was also used to shoot aircraft down!), was popular for use in aircraft because it was comparatively light. (The difference between a canon and a machine gun, for those not in the know, is that the rounds from a canon explode on impact.) The repeating mechanism on the Hispano was gas-operated. When the projectile passed a port cut into the barrel, the hot gas entered a chamber where it pressed against a piston. The piston was connected to a rod running back down towards the rear of the gun, that unlocked the bolt or breech-block, which was then driven backwards allowing the next round to be fed into the breech. The chamber containing the piston and rod can be seen on the top of this gun.
Mosquito (3)
The Hispano canon, while not used universally in aircraft (it was also used to shoot aircraft down!), was popular for use in aircraft because it was comparatively light. (The difference between a canon and a machine gun, for those not in the know, is that the rounds from a canon explode on impact.) The repeating mechanism on the Hispano was gas-operated. When the projectile passed a port cut into the barrel, the hot gas entered a chamber where it pressed against a piston. The piston was connected to a rod running back down towards the rear of the gun, that unlocked the bolt or breech-block, which was then driven backwards allowing the next round to be fed into the breech. The chamber containing the piston and rod can be seen on the top of this gun.