<div class="htmlview paragraph">The continuing requirement for weapon systems capable of efficient operation over a wide range of altitude, Mach number, and power setting emphasizes the importance of propulsion system off-design performance. This paper illustrates the effect of installation losses on this off-design performance and considers some of the limits on usable performance imposed by stability considerations. The nature and extent of installation data required are discussed. The importance of using realistic installation loss coefficients during cycle selection is stressed and the improvements to be gained by using components with inherent aerothermodynamic flexibility is discussed.</div>