2329. Method for Balancing VTOL/STOVL Aircraft

Paper

Abstract

A closed-solution balance procedure for the preliminary design of VTOL/STOVL aircraft is presented. The effects of various propulsion concepts on balance and aerodynamic configuration are discussed. It is shown that for a CG location, specified in percentage of MAC, the problem reduces to solving two simultaneous linear equations for the required engine and wing locations, respectively. In contrast, when the CG location is implicitly expressed in terms of longitudinal stability and horizontal tail size parameters, the equations will be non-linear. As opposed to trial-and-error, the present procedure directly exposes the influence of all pertinent design variables, thus providing the designer with valuable and time-saving insights to arrive at a balanced configuration. A table depicts fourteen basic VTOL concepts. Of’ these, balance equations are derived and discussed for five ”lift/cruise” types and for one fan-in-wing type. For any other V/STOVL concept, the pertinent equations can be easily set up, and as many component weight terms added as the case may require. A constant-bleed hover reaction control systems (RCS) is discussed in appendix A. Spreadsheet examples of the procedure are given in appendix B for a Lift+Lift/Cruise, and in appendix C for a fan-in-wing design. * An outline of this paper was given in SWR-7 at the society’s First Annual Southwestern Regional Meeting, 11 October 1974. The subject was a key element in preliminary design studies for the Sea Control Ship VFA, conducted at the former Advanced Aircraft Systems Program Office of the Naval Weapons Center, China Lake, in the 1972-1975 period. The author was then head of the Aircraft/RPV Predesign and Advanced Technology Branch. Interest in the current JAST development program prompted this formalized and expanded issue.