Mighty Gem - yes thanks, I saw that the first time round but phrases like -
'rotor wake(s) being tracked in a Lagrangian sense using the free-vortex method of Bhagwat & Leishman'
- are a bit beyond my O level maths and make me feel quite sleepy
I know Nick's web pages had some more 'pilot-friendly' info but none of the links work any more - I guess he has moved to another provider.