Large Helo Autorotation/Certification vs Operational
Crab, I believe that you have it right, and allow me to expand just a tad on the technique used in the S-92 video.
FAR 29.79 and 83 provide the requirements and AC 29.2c, pages B-83-84 provide general guidance. One will note the absence of a required minimum landing speed, and the AC only recommends a speed under 40 kts.
Another reality surrounding the question of what is the best way for the manufacturer test pilot to proceed is that the machine in question is typically the envelope expansion/structural test aircraft, and thus has the maximum instrumentation installation. That makes it a very dear commodity, with serious consequences should it be seriously damaged.
It is clear in reading the advisory circular that the FAA intent is clear and stated in AC 29.75A.b.(2)(vii).(C): " The intent of this rule is to demonstrate controlled touchdown conditions and freedom from loss of control or apparent hazard to occupants when landing with all engines failed."
There is no instruction or direction that requires the demonstration to perform multiple power off landings to replicate what might be the best operational power off landing procedure for conditions such as: landing in forest, landing in a soft, or muddy plowed field, or the ocean. Certainly, ( and I think you were referring to these conditions ) in any large single rotor machine, these conditions would make the pilots approach to ensuring tail rotor clearance during the end of the flair a bit different, as the pilot will want to minimize the touchdown groundspeed.
As to the question of practice and build-up, its not very complicated. Since the pilot knows that at sometime in the future the landing has to be made, he will do a powere recovery auto at the end of other test flights, to look at the flare entry speeds and the flare angle required to temporarily zero out the rate of descent. Then, when its time to do it for real, two or three power recoveries and then finish it.
This is the approach used by the pilots who did the CH-53A, the S-64 E and F, and that I used in the S-67, UH-60, SH-60, S-76 and S-92. No dents or dings in any of them. I am sure that other OEM test Pilots can attest to approaching this first-time task in a quite similar way.
Thanks,
John Dixson