I agree Bell_ringer, but DB getting on his high horse about a thread where no-one has suggested just going out and trying such manoeuvres seems rather OTT.
My point to DB was that less than 1g in a helicopter or even negative g doesn't lead to the instant mechanical failure he implied - you can get to negative g without aerobatic manoeuvres as you know.
Mr Crab! its been a while since we locked horns however, I like my high horse! You know well that the design certification process will accommodate any turbulence induced negative G. However, as stated by other posters here, Aerobatic manoeuvres are prohibited in all the FMs I have ever looked at. The fuselage is designed to dangle below the rotor in positive G...generally. Stick to the rules and limits because they are there for a reason. As an ex RAF SAR Hero Type I know you love to feel aligned with any form of exciting flying to get your juices flowing. However, I like my helicopter the right way up, compliant and within the limits and I balk at any suggestions of excitement or thrills that are primarily getting derived from chucking the helicopter around the sky with a scant regard for the designers limitations he set in place to keep us safe. Willy can be waved. Chest puffed out and beers downed while the lamp swings but it cuts no ice when the next poor unfortunate pilot inherits an airframe that has been stressed and damaged by morons seeking cheap thrills for fun. Like I said, this is a professional pilots rumour network. Operating beyond the limits in the FM is just not professional. Take care Mr Crab over which side of the line you want to be seen to be! I am ex Army so we are not as bright as your Brill cream Types and thus....we trust and stick to the rules cos our little green brains can't operate outside the box in nasty dangerous parts of the flight enevelope.