<div class="htmlview paragraph">PROPULSION SYSTEM PARAMETER selection for a V/STOL design must recognize a set of priorities somewhat different from those identified with classical engine cycle analysis. Propulsion and airframe design parameters interplay to a major extent in driving the configuration. This interplay highlights the importance of properly selecting thrust geometry, lift cruise fan parameters and the number of core engines to be employed.</div> <div class="htmlview paragraph">V/STOL A missions as currently defined converge in a propulsion system “design space” which suggests that propulsion commonality is attractive. The desirability of commonality expansion to other design arenas can be grossly evaluated in the conceptual design phase by use of a commonality payoff function.</div>