BVRAAM - it could get really silly at nav school when I was going through. Not only did we have to address all instructing staff as "sir", this applied irrespective of rank. So you would get the crazy situation of a flying officer student nav calling his flying officer staff pilot "sir" while the sergeant FE who flew on the Varsity addressed his pilot as Fred (or whatever). We also had a flight lieutenant stude on my course who was expected to address the flying officer educator who took us for maths revision as "sir". On reflection it might have been better if we had all called each other "mate"!