Shy: Disclaimer-prior to installing the fan tail on the S-67 in 1974, we had the opportunity to fly a short eval in a privately owned Gazelle, and it was pure fun to fly.
212: In fact there was a marketing movie circulated re the Gazelle maneuverability, featuring a Gazelle in French Army colors and with the Light Cavalry Overture by Von Suppe as background.
SAS: re the comment about all flight loads-Yes.
I'm assuming Part 27 mimics Part 29, in requiring the basic design to positive 3.5G, but with an important follow up statement to the effect that less than 3.5 is acceptable if analysis and flight test proves the lower number is extremely remote. The flight loads survey is then flown to that envelope, and the resultant flight loads are utilized in assessing fatigue damage accumulation and component replacement times. It appears that the philosophy used by Eurocopter at the time was to use the limited capability servo system as a flight envelope limiter. I would guess that some in their flight test group foresaw the weakness of that choice, but were overruled. A design choice that was never repeated, however, as far as I know.
Alternative approaches included the Cruise Guide system on military 61's and 53's, later copied into the 47 ( Chinook ). On the S-67 we had a cruise guide AND a collective stick shaker, activated by the same control load sensor in the servo, but much more usable in a heads-out-of-the-cockpit scenario. Cruise Guide was based on a load sensor within the primary servo. The basic idea was simple. Flight test proved the relationship between control loads and stall, so setting some limits on loads thru the indicator kept the usage within the flight loads data. I must add an important note here because the handling of flight loads data is different on US military machines vs the FAA: although the military machines utilized the cruise guide indicator system, the implementation of flight loads data as to component replacement times also included a spectrum of control loads from the military structural demonstration ( which FAA Regs do not require ), where the machine is flown to the 3.5 G limit or to a limiting factor preventing that. ( example of a limiting factor from the UH-60 demo: at 80 KIAS, one can't generate enough pitch rate to get 3.5, so collective must be used. Applying collective at the max rate helped, but we quickly got to the engine limiter, drooping the rotor. With lift being a V-squared term, that didn't help. thus the max we could achieve at 80 was 2.6 as I recall. At the higher speeds, the limit G achievable was typically limited by control loads/stall/vibration-typically occurring together. While we were able to achieve 3.53 at lighter weight, 3.23 was the max achievable at design ( mission ) weight. )
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