Buzzard IMS, (H.XIMS) (1927), Maximum power 955 hp (712 kW), nine engines produced at Derby. Buzzard IIMS, (H.XIIMS) (1932-33), Maximum power 955 hp (712 kW), reduced propeller drive ratio (0.553:1), 69 engines produced at Derby. Buzzard IIIMS, (H.XIVMS) (1931-33), Maximum power 937 hp (699 kW), further reduced propeller drive ratio (0.477:1), 22 engines produced at Derby.