dual spark heads

Aircraft engines use dual plugs because they run separate ignition systems. Also the dual plugs may help get all of the combustion gasses to burn in those huge diameter cylinders. My O-320 is 320 cubic inches on 4 cylinders. Before takeoff pilots set the RPM to 1700 and turn off each ignition system to check if the other mag is working and noting the RPM drop. The engine loses about 100 RPM on one ignition. Aircraft engines are very low performance as far as how they are built. Mine has 7-1 CR and runs on 87 octane non-jokenol car gas.