I actually havn't flown an R44, but on discussion with fellow R22 drivers a few years back, a comment came out about the cooling fan cracking at full RPM if there is any decent vibration involved with the mag check. It was not uncommon to find cracks in the fans and the comment seemed to have some merrit to.
Having said all that I don't know how true it all was.
P.S. I like the springy idea above. Sounds like he actually knows what he is talking about - where as everything I have learnt usualy involves a lot of alcohol and tall stories.
Cheers