Short Takeoff Performance Using a Gravity Assist Ski Jump

Abstract : A modified or gravity assist ski jump is developed, through an application of the calculus of variations, to provide for the shortest takeoff roll for a thrust vector control type vertical or short takeoff and landing (V/ STOL) aircraft that will maintain a better-than-minimum required rate of climb. As a means of comparison between the resulting modified and a conventional ski jump, the equations of motion are programmed to model the takeoff performance using a ski jump. The results of this model are found to compare well with Naval Air Test Center ski jump test results of the AV-8A aircraft. A comparison of the standard and gravity assist ski jump shows a reduction of 30 percent in required ground roll and 20 percent in distance to a 50-ft altitude, while maintaining a better-than-minimum required rate of climb, with the modified ramp. A simple modified ramp, using a pair of standard multiple girder bridging (MGB) ramps, is shown to provide similar improvements in takeoff performance.