In defence of the senior service Crab@, in the days when MoD(PE) project managers had to know quite a bit about the kit they were procuring (the how to maintain it was a given, but how to use it wasn't), the RN chap who taught me most about their HAS Mk5/6 work was an old and bold Chief Petty Officer Roy Henshaw, who I hope won't mind me mentioning his consummate skill.