...in the aircraft, first names between folks who know that what goes on in the helo, stays in the helo. If there is a recent arrival, e.g. a new Cpl flight engineer, I'll use his/her rank and lastname for a while until the experienced FE's give me the thumbs up that they've briefed the new kid on protocol and he/she's good to go and won't do things like call the OC by his first name in front of everybody in the Sqn canteen (ya, just takes one of those and a very old school CO to learn ya.)
...back on the ground, I'll call Capt/Lt's by first name if we're in a less formal environment (like crew debriefing, etc...), but when I refer to one of the officers in a more formal discussion, I find it more professional and respectful to use rank/name. In larger groups, I will call NCMs by rank/name (out of respect to them and the fact that some need that level of formality shown for consistency with how they address their own subordinates). One on one with NCOs I know well and trust my crew and machine with, I'll use their first names and personally I'm G2G with first name in private, although some prefer 'Maj'. They all use sir to me on the ground when others are around.
Some of my CADPAT brethren tell me that that kind of stuff is wrong, that it degrades discipline. I can't speak to their own situations so I won't contradict them...that may very well be true for their community. However, in my very particular operational experiences, I have not found that to be the case. As others have mentioned...time, place, situation, mutual respect, etc...you have a feel for it. There have been times when trying to verbalize rank, name and command/order in flight would take too long and a first name is exactly what you need in a busy situation to get your attention at the right split second. I don't see it as being chummy and that's not why I would use first names...I see it as a trust, intimate team interaction/response thing. It is very particular to folks' situations.
Judgment is the important bit, I think...what is acceptable for the environment you're in at the moment, respect for all involved and consistency. Some guys assure consistency by fire-walling formal...fine, whatever works for some folks. I prefer the interaction, including developing judgment in my NCMs and officers alike in that professional interaction, and I feel that it can be a tool to maximize the effectiveness of my team's msn conduct.
Cheers,
Duey
) The juniors or seniors will respect you for what you do, and you them. Working with friends, makes it a bit difficult sometimes (especially if they are 3-4 ranks above you or more...) 
) That they are all renamed Bruce to avoid confusion. Also, that their fingerprints are burned off, and all their families relocated to remote fishing villages in Newfoundland with new identities....
