Backward Blade I didn't mean to imply that 'all' of the maneuvres I listed have been performed in every helicopter out there, only that I have witnessed, have seen on film, or have heard of people doing something that might be considered aero in just about every helicopter that has been built. Some have even managed to do so successfully. I have seen skewed loops in a B206 and an R-22. I happen to consider loops in those aircraft to be extremely dangerous because if the slightest mistake is made then the outcome is likely to be fatal.
[email protected] I could not agree with you more. Without a recording G meter one has very little ability to determine if the G limits of the helicopter are being maintained.
I am often asked why Boeing performs the same routine in the Apache at every airshow. The reason is that aerobatic envelope expansion was conducted at mission gross weights to 7K Hd in an aircraft that was fully flight strained. We also did abort maneuvres such as an inverted pull through at high G from a pitch coupled roll which, as you well know, can involve some unusually high G. We know that those maneuvres and the maneuvres necessary to recover the aircraft if they go wrong, can be safely performed within all aircraft limits. We also know that they cause only a very slight reduction in the calculated lives of certain components. We don't do other maneuvres because I have no way of knowing with certainty that there are no detrimental affects to component lives unless we do another flight strain and that is very expensive.
Helicopters that are specially certificated to perform maneuvres beyond their certificated envelope are required to have a G meter installed. Further the FAA is beginning to require at the very least a vigorous engineering analysis of the proposed maneuvers for the very reasons you espouse. Many designs can do these maneuvres without coming apart in flight, but the real problem then becomes how much reduction in time-life components should be applied since these maneuvres haven't been applied to normal SN curves.