I know that this subject has been debated many times.
Whilst patiently waiting for my new R44 I have spent many hours researching this.
Accidents don't just happen to other people and I am well aware of my responsibilities to my innocent passengers, especially as the ink on my PPLH is still wet.
One report well worth reading is this one - a huge 115 pages.
http://www.ntsb.gov/publictn/1996/SIR9603.pdf
Many of the accidents described find no reason why the main rotor struck the tail. One second everything is fine, the next...disaster and death.
Bird strikes have been mentioned and in one case bird debris has been found on a blade but still not cited as the most probable cause.
You don't need to be a scientist to understand that even a small bird hitting a rotor blade in the cruise will be a serious impact in view of the speeds involved.
The NTSB speak about wind tunnel testing. I can't find much on this specific subject.
Has this, for example ever involved the simulation of a heli in the cruise - possibly involving sets of run-out blades - and firing birds directly at the blades?
In the case of homicide, very sophisticated DNA technology is brought into play and positive results achieved with microscopic samples. I wonder if similar technology is used to examine rotor blades?
A bird strike could surely provide the very force necessary to distort a blade in such a sudden and devastating way, yet not necessarily leave evidence visible to the naked eye?
My guess is that this has all been specifically debated here many times but I am a relative newcomer.
Any help will be gratefully appreciated.
HP