How rapid will rotor RPM decay?
When helicopter certification regulations were first written back in the 1950s, all of the helicopters had high inertia rotor blades. Engine failure autorotation entry tests with these helicopters had some builtin safety because of the high inertia rotor systems. Later on, helicopter rotor designs with much lower rotor inertia were certified. In some cases, factory test pilots are now admitting that the helicopters were not able to meet the certification requirements re. rotor RPM decay after engine failure. Some US FAA test pilots are also confirming this. If the helicopter manufacturers stated in their flight manuals what the RPM decay was...XX% per second...and also stated what the minimum RPM before blade stall was, would that help as a wake up call to pilots and be useful information? Do you know what these conditions are for the helicopter you fly?
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Dr. Michael K. Hynes