2383. The V/STOL Propulsion Weight Fraction Revisited

Paper

Abstract

In light of the current JSF prototype program, the causes for the 40 year long cyclical and stymied efforts to develop the fixed-wing high-speed powered-lift V/STOL aircraft are briefly reviewed. Four imperative design objectives are suggested and defined. Two of these are: 1) a benign exhaust footprint, and 2) a low propulsion weight fraction of take-off weight. The propulsion group weight fractions of 45 designs, encompassing ten powered-lift concepts, are plotted Vs conception year, It is shown that airframe weight savings have the potential to offset propulsion weight increments. Cruise engine weight is the largest part of total propulsion weight, and bypass ratio one of the most important cycle variables. Therefore, a correlation of engine thrust/weight ratio with bypass ratio for 17 engines was made to trend the upper and lower bounds of the scatter band.