Can anyone enlighten me as to how this system actually works ? PS. Please don't just tell me it allows machine guns to fire through the prop blades without hitting them - I know that already.
Essentially the MGs are converted to sem-automatic fire (one shot at a time). The timing of each shot is controlled by the synch system, which fires the gun each time it can do so without hitting a prop blade. So the sequence goes something like this: 1. Pilot presses firing button. This doesn't fire the gun, it just tells the synch system to fire when ready. 2. Synch system is linked to propeller revs (or engine revs in the case of a direct-drive propeller, as in WW1). 3. Synch system fires the gun as soon as the prop blades are out of the way. 4. Gun reloads, then synch system fires again.....and so on. There were various methods used by synch systems to fire the guns. The first types were mechanical - a cam attached to the propshaft pushed a lever to fire the gun, or a cable was used. The British developed the CC hydrosonic system in WW1, while Germany developed an electrical system (the firing signal was sent to a solenoid which fired the gun). In WW2 Germany used the ultimate system in the MG 131 and MG 151: electrical ignition. The synch system sent an electrical impulse to the gun, which directly ignited the electrical primer. The effect on the rate of fire of the gun varied considerably, depending on a number of factors. The best results were achieved by Germany in WW2, with about a 10% loss. Most others at that time saw a loss of around 25% with some at 40-50%. Tony Williams: Military gun and ammunition website and discussion forum
