There's is an amazing amount of stuff to learn about big aircraft radial engine operation and I read quite a lot about it from a pilot that had been flying them for many years and wrote about the intricacies and debunked a lot of old myths. One was to never let any people inexperienced at hand turning the prop of a big radial engine through it's "blades" prior to starting as if they are unaccustomed to the "feel" of a cylinder hydraulic locking they can walk it right through the lock and bend a rod. Better to rely on the starter clutch to protect the engine and "bump" it through that way. Quite amazing, I never thought it was an issue. I spent hours and hours reading his stuff. No longer with us unfortunately, another - victim.
Ciao
