The decision to put a FBW system in the MHP was made before I retired, and quite honestly, I foresaw a major issue with FAA certification due to the absence of a certification standard and advisory circular. Prior to any contract issue on FBW there was an internal certification committee having control over foreign sales to countries not having their own certification agencies or not depending on a US military certification. In those cases,an FAA certification standard would govern the design. You can see the issue this posed for the MHP: the FAA did not have one. But the contract included an FAA certification, eliminating further discussion.
I checked with a friend who was intimately involved with the test/qual program, who told me that actually, SA had made good progress with the FAA on FBW doing yet another “ Special Conditions “ approach. With regard to the electronic force feel connection between the sticks and the SA trim follow-up system, and in fact the whole longitudinal static stability discussion, apparently the FAA brought Airbus in, whose basic control system in this area is similar to the 92 system, they looked at it , told the FAA no problem, and that was the end of that discussion*. In the end however, due as you mentioned the VXX going to Westland and the associated subsequent USAF application, an internal decision was made to avoid the cost/schedule impact of doing the FAA certification and it was dropped. I didn’t get into the other details with my friend.
Had not known they had progressed that far with the FAA, and am a bit disappointed they discontinued the effort, as the technology not only saves a good deal of weight, it assists in eliminating a source of human induced maintenance errors-I’m referring to the elimination of all the mechanical and AFCS/Autopilot clap-trap on the forward upper deck, not to mention the ability to really tailor the control system for maximal handling qualities for the intended mission.
* we could probably start another thread about the now medieval approach to handling requirements remaining in Pt 29, but I doubt the people who should be doing something about it read this site.