One aspect of the Helos accident which interests me is whether either of the flight crew had had hypoxia training. During my commercial pilot training (back in 1969) we were all taken to the nearby Navy base and put in the chamber and taken up to 35,000 ft or so and then asked to do simple tasks after the oxygen was turned off. (We had previously covered all the various physiological aspects in the classroom). It was really impressed on us how vital it was to get onto oxygen should there be a pressurisation failure and the dangers of not doing so. But the actual experience of hypoxia in that chamber is something I have never forgotten.
As a professional pilot I have asked some of the new entrant pilots whether they have had hypoxia training and have been very surprised that this was not included in the syllabus for their commercial training. I would have thought that all commercial pilots who may be involved in operating pressurised a/c ought to have had practical training concerning hypoxia.