The US Navy mandated air cooled radial engines due to their robustness. The US Army Air Force adopted water cooled V type engines for performance. An air cool

The US Navy mandated air cooled radial engines due to their robustness. The US Army Air Force adopted water cooled V type engines for performance. An air cooled radial can suffer damage such as "dropping" a valve because each cylinder and cylinder head is largely independent. There is no shared water jacket, for instance.