Thank a lot of the explanations - genesis the engineer Dick and Lasseb, i now understand it a bit better now, but obviously a quite complicated subject! Dick and Lasseb you two guys know your !!!!.
N.B. Dick i got this from 'ace the tech pilot interview' i understand there is meant to be a few mistake from this book, but sadly it seems to be what the airlines are using, as a couple of my friends that are now with the airline studied this book religiously though for my own sake and others reading trends i am trying to find out where these mistake are in the book, thanks for your help Dick.