I recall the FD12 was selected for the Hunt class because it's characteristics of low vibration & low magnetic signature were necessary when sweeping above active mines. The FD12 generated electrical power at 1800 r/min, which equates to 360 firing cycles per second, vibration was further minimised by mounting the gen set on a raft with two sets of mounts transmitting little vibration to the hull/sea. Three gen sets were mounted in the hull above sea level further reducing noise transmitted into the water. The crankcase was cast in non-magnetic aluminium, as were many of the auxiliary casings, stainless steel conn rods & c/shafts etc all adding to low magnetic signature. Part way through development Foden decided the work was not for them & the MoD transferred the work to R-R Crewe, presumably because R-R had considerable experience of 2 strokes with the K60, which had proven to be the best 2 stroke in UK military service. When sweeping the ship employed electric only propulsion making the ship was pretty stealthy, noise-wise. It was during the Iraq / Iran war that the Hunt class cleared the passage of mines into Kuwaiti waters for the allies, they did the job well without loss, they were the best ship available to do the job.