Design and Development of Stability and Control Systems for Small, Deployable Aircraft

Abstract

This thesis presents the development of the tail system for Firefly, a kilogram-scale, transonic, rocket-powered, deployable UAV. The propulsion system, vehicle size, and stowability requirements present challenges in designing control surfaces with adequate stability and control performance. To satisfy the stowability requirements, the tail was designed with an oblique hinge in which the deployment axis doubles as the control-surface actuation axis. Actuation mechanics, deployment spring sizing, and other mechanical details are also presented. To model the stability and control effects of the large oblique motion of the tail's control surfaces, a custom pre-processor was developed to deflect them for vortex lattice computations. The accuracy of this method is compared against the conventional "control" vector method in subsequent testing. Wind tunnel testing was performed to evaluate longitudinal stability and controllability. Unpowered flight tests were conducted to collect flight data and test the mechanical functionality of multiple tail designs. The accuracy of the vortex lattice aero-control predictions are discussed and recommendations are made in regards to the applicability of the oblique surface deflection pre-processor.