Same vintage as LITAS was AAI (Angle of Approach Indicator) but even I can't remember how that worked, although I did see one on Peter Cadbury's airfield at Preston Candover (now long gone)!
OK then, from the 'Manual of Air Traffic Control' (no not 'MATS Part 1), define 'slush'.
Last edited by chevvron; 27th January 2014 at 17:44.