Interesting find Hesham. The above explains why the Lynx was used. I expect Westland/AW/Leonardo may have similar sketches of modified Lynx's and Wildcat's filed awayThe main aim of this paper is to assess the dynamic stability of compound helicopters and compare their stability to a conventional helicopter. The strategy for the current work is to use an established mathematical model of a conventional helicopter (in this case the AgustaWestland Lynx), then convert this model to represent compound configurations. The Lynx was chosen as a well established data set [17] and model was available [18].