Survey of significant technical problems unique to VSTOL encounteredin the development of the XC-142A.

Abstract

The XC-142A is a tri-service, V/STOL transport employing the tilt-wing concept for vertical lift. Five of these aircraft are being built by Ling-Temco-Vought, prime contractor with Hiller and Ryan as associates for operational suitability testing. Although the basic configuration does not entail extending the state of the art, the interrelationship of the tilt-wing deflected slipstream concept and the flight control system led to certain problems unique to the XC-142A. Aerodynamic analysis led to the selection of counter-rotating propellers and leading edge slats. Stringent weight guarantees posed a significant challenge in view of the interconnecting cross-shaft system and associated dynamic and aeroelastic problems. High intensity noise was a major design consideration for the XC-142A, since both structure and personnel could be affected. Establishment of adequate design criteria posed the most important initial technical problem, since MIL specs did not exist for flying qualities between the conventional aircraft and the helicopter. To solve the significant problem of minimizing cross coupling and yet provide controls that always apply the correct moment about the correct axes, a mechanical integrator linkage was employed to transmit pilot control motion to the proper controls as a function of wing position. As conceived by the Department of Defense, the XC-142A program was provided with adequate test programs, so that these problems could be overcome.