About 20 or so years ago I went up to RNAS Yeovilton for a presentation by Lt Cdr Adrian Orchard on the future of the Fleet Air Arm. He was CO of 800 Sqn flying Harrier Gr9’s at the time. One of the subjects I raised at the questions session afterwards was what were they going to replace the Sea King airframes with, they were close to retirement then and there was no plan. I suggested the Merlin was the ideal airframe for the Jungglies (846, 845 and 848 Sqns). The RN already had the HC2 version in service at sea and the technical support in place. Another 45 or so airframes would be ideal or 24 if they cut the sqns down to 8 apiece, which was being suggested at the time. He said that was not an option, the HC3 Merlin was not blade folding and was not suitable for Cdo Ops, which I suggested was complete bollocks (I had served in 846 and 845 sqns so I did know something about the subject). There was also the matter of cost, they did not have the budget to buy any more airframes, so I suggested we take the RAF airframes and get them blade folding capable. He stopped the conversation by saying it would almost certainly require a complete rethink for the RN and he favoured Chinooks, which was a crazy idea given the amphibious ships we had then (HMS Ocean). They would have to stay on deck or be blade stripped to go below, which would make their usefulness in an assault to be almost zero. The Chinook is a fine helicopter, but it isn’t navalised and it would suffer badly at sea, on an open deck.
Stealing the airframes from the RAF was the only option in the end. All of those airframes are being converted to HC3/4 standard with folding blades etc etc and they will equip 846 and 845 Sqns with them in the Commando Helicopter Force, based at RNAS Yeovilton. 848 Sqn was disbanded in 2016.
847 Sqn (formerly 3 Cdo Bde Air Sqn based in Plymouth) now provides armed support to the force flying Wildcats. I served in that for 2 years when it was in Plymouth.
Cant see the AW 139 being suitable for RAF Troop lift, executive toys at best !! More Merlins I would say, and make them HC4 capable to fly from carriers, spread the load so to speak.