[Jon]

Reading many accounts from pilots attacking the IL2 they all agree that the best route was from behind and underneath, away from the gunner and directing fire into the tailplane from close range. The 20mm was perfectly capable of bringing down the IL2 provided pilots ingnored the usual areas to target such as the engine with its heavy armour.
Nick has hit the nail on the head, all liquid cooled aircraft can be brought down by a single rifle bullet, the Typhoon with its massive inviting radiator surrered considerably from ground fire as well as flying into derbs from its own kills / ground attacks. Placing armour infront of a radiator is not even an option as the engine will simply over heat in seconds.
I still think the Typhoon was the best ground attack aircraft of World War Two with its ability to hit targets hard with cannons bombs and rockets but have the ability to revert back to a fighter should it encounter enemy aircraft. The IL2 although superb at dishing it out apperas to have only been able to lumber along and defend itself by flying low, allowing mutual covering fire from its gunners