Takeoff performance of jet-propelled conventional and vectored-thrust STOL aircraft.

Abstract

An analytical method for the determination of the air distance of jet-propelled conventional (CTOL) and vectored-thrust short takeoff and landing (STOL) aircraft has been developed. The method assumes constant lift and drag coefficients during the climb and a constant value of the horizontal acceleration based on the aircraft's average velocity from touchoff to the 35- or 50-ft obstacle. It is indicated by this method that some classical or specification methods for computing CTOL air distances are not generally applicable. Design charts are developed for determining the ground, air, and total takeoff distance in terms of: an STOL thrust-to-weight ratio, (Tx/W)/( - TV/W) an effective wing loading (W/S)(l/aCLo)', and the L/D ratio. A parametric study of approximately 100 hypothetical CTOL and STOL aircraft was made, and graphs of the takeoff performance presented. It is shown that thrustto-weight ratios greater than approximately 0.6 are required in order to show performance gains by thrust vectoring, that the major improvement in takeoff distance derives from the reduction in ground roll while air distance is relatively unaffected, and that reduced wing loadings or improved high-lift capabilities are equally as beneficial.