The RN are not bothered about their harmony guidelines as they understand the need to deploy in ships for extended periods. The first thing the RMs want to do when they get back from Herrick is a spot of leave and then off on an ex or more ops. I seem to recall that the RAF would deploy for 4months and 1 day because that would get them the OWP.
Another thing missed recently is that you need to be able to operate from a deck in sea state 6+, I do not think we have done that for a while around the Gulf and Med. That would probably count the AH guys out and make the CH47 go running for their beds.
In terms of capability maybe the CH47s should be split between the Army and RN....only teasing.