Have to disagree with Roamingcyclic.. .. .The limits were set by the turns we did for original certification structural substantiation. We took data while turning, and labled the data "12 second turn". I did most of that flying, along with Dave Wright, the current S-76 Chief Pilot. That set the limit. We have since turned at blithering rates without concern, but never submitted the data to the FAA for increase of the limit. The S-76 was used as a demonstrator for LHX maneuverability, and the FANTAIL demonstrator had no tail cone mods necessary to do 90 degree snap turns in 2 seconds at 120 knots.. .. .But the law is clear, you are stuck with the limit.. .. .As a general comment, few helicopter limits are set by the strength of the sheet metal, most are rotor stresses due to maneuvering. This is not true of airplanes, where the loading of the metal tails or wings directly affects the maneuver envelope. That is why most helo pilots think that pulling too much G or yawing too fast will wrinkle the metal. In reality, the rotors will hit limits, and bearings will wear out early, or blades will get wrinkled if you maneuver too fast or too hard. Seldom will the tailboom or fuselage structure be the problem.