Aaron Do you mean attrition, or just unserviceable and having to wait until return to port? The annual Instructions, from which the 2nd and 3rd Order Assumptions were derived, set out the latest attrition forecast, based on historical data. I do recall that it was fairly steady in the mid-80s, and the sudden jump from a Lynx loss every 40,000 flying hours, to 30,000, caused ructions. This was about the time 'Sonics Lynx' was being mooted, and it was assumed someone had tweaked the figure in anticipation of the new role. Engines will probably know more, but I know there was a large initial peak in SHAR attrition due to outriggers hitting the ramp. But that settled down.