Sopwith's radial engine types primarily the Sopwith Camel were difficult aircraft to fly

Thanks Teribus. Those engines were rotary, not radial, meaning that the entire engine - crankcase, cylinders etc, rotated around a fixed crankshaft. This was a large mass creating large gyroscopic forces. As I understand it this is what made the aircraft so difficult to fly. In addition they were lubricated with castor oil which sprayed back giving the pilot a liberal dose.