For mckeg4's benefit I would ask how many main gear box failures have there been? And just think of how many flights there are on the North Sea and around the world. Yes there have been cases of gear boxes 'making metal', but catastrophic failures like this are extremely rare. The only one that comes to my mind at the moment is the Bristow's Puma 9M-SSC out of Lutong, Sarawak back in December 1980. There may have been others, but I can't think of any at the moment. Generally more frequent (but still rare) incidents are with tailrotor or other failures which are surviveable.