The cause is clearly blade-sail, a phenomenon which has been known about for some time, but not well understood until reasonably recently. Much of the basic theory of why blade sail happens was cracked 10-20 years ago by Dr.Simon Newman, who has published several very deep papers on the subject and is also author of "Foundations of Helicopter flight". I had lunch with Simon (who taught me as an undergraduate and has become a friend and collaborator on various non helicopter safety projects) a few months ago and we got chatting about the subject in general. Apparently with the newer more rigid rotor systems such as on the Merlin he's finding the need to start getting involved again, not because these systems are prone to decapitation based incidents in the way that the Wessex and EH60 are/were, but because the same forces and mechanisms are putting huge fatiguing loads on the actual hub mechanism and it is starting to become a serious worry at the design offices of places like WHL. Thus ends my theoretical knowledge of blade sail, but that should be enough for anybody interested to look up SJN's published work on the subject.
Regarding the website, as a moderator from elsewhere, could I lend my support to the moderators here. The subject is utterly worthy of discussion, the discussion is not aided by morbid pictures of somebody who was in a highly unfortunate accident. I have worked on the investigation of 6 fatal accidents in my career, in none of which would sight of anything more detailed than the summary of a pathologists report have helped me in my work - for which I am deeply grateful.
G
Postscript, the following references are relevant...
Helicopter flight around as ship's superstructure
JOURNAL AEROSPACE ENGINEERING - IMechE, 2002, Vol. 216, Part G, pp.13-28. (Wakefield, Newman, Wilson)
The phenomenon of helicopter rotor blade sailing
Proc. Instn. Mech. Engnrs, 1999, Vol.213, Part.G, pp.347-363. (Newman)
The design, development and operation of the shipborne helicopter.
Transactions of The Royal Institution of Naval Architects, 1999, Vol.141, Part.C, pp.192-210. (Newman)
The influence of blade flexibility on the sailing behaviour of helicopter rotors
Journal of Defence Science, 1996, Vol.1, No.4, pp.498-507. (Newman, Walker)
Last edited by Genghis the Engineer; 22nd Feb 2003 at 08:45.