I come late to this item, but feel I must comment on some of the comments on HUMS and EC155.
As somebody who was directly involved in both issues, I must say I felt some annoyance at the comments made.
Although now some time ago, it would be criminal not to mention the enormous contribution made by Alastair Gordon of Bristow to the start, definition and implementation of HUMS. Whilst all due credit must go to Shell Aircraft for their financial support, encouragement and research, the ACTUAL practical implementation and installation of the very new and unproven concepts and techniques was driven by Bristow and Capt. Gordon's enthusiasm. It was he for instance who came up with the idea of combining the CVR,FDR and HUMS which enabled this to be a practical proposition on weight alone. To forget this is to devalue the enormous effort put in by a team of over twenty people at that operator's Design office. This topic may be worth a thread of it's own!
On the 155 issue and Nigeria, I can only say that there was no 'fly off' or proper evaluation with the 412. Many other factors were present at the time, and I have heard even people at ECF admit that the 155 was the "wrong aircraft in the wrong place at the wrong time". I'll say no more.