To return to the original point, the AAC's heavy outflow of helicopter pilots is inevitable given the nature of the beast. Unlike the RAF and RN, the Army does not need officers for the majority of its drivers airframe slots. They are therefore taken by very bright and competent young SNCOs.
Whereas an officer pilot can expect and aspire to a full and rewarding career on return to regimental duty after a flying tour, this is not the case with most SNCO pilots. After commanding an aircraft and operating on an equal professional footing with senior officers, it is not an attractive prospect to become a grunt again and lose flying pay. Therefore, most who cannot transfer to permanent AAC or who are not considered suitable for commissioning in their own regiments will leave and look for a rewarding job in civvy aviation.
Even if a SNCO transfers to AAC permanent cadre, there is very limited scope for career advancement so when the embuggerances outweigh the attractions they will leave for greener fields.
If the Army wants to retain these highly skilled pilots it needs to rethink their career options, Ts and Cs and rewards, especially flying pay. These will not necessarily resemble those of the RAF and RN equivalents, because they are not equivalent.