Redesign of a Human Powered Aircraft using the Boxplane Concept

摘要

A redesign of the human powered aircraft Gossamer Albatross using the boxplane concept, with the intention of reducing the aircraft span without compromising its aerodynamic performance, is proposed. For the same span, boxplanes have lower induced drag and better structural efficiency, but they also have greater wetted area and, therefore, higher parasitic drag. The analysis was conducted using VLAERO+©, a vortex lattice method computer program, which was first validated with respect to published flight test data of the Gossamer Albatross. The differences encountered in the validation exercise are analyzed and explained. The computations display similar trends to those of the experimental data without achieving a perfect match. The discrepancies are due to the the linear and inviscid formulation of the method. The program allows for calibration using additive and multiplicative factors that, within certain bounds, render reasonably accurate results. The calibrated model of the Albatross was then modified to become a boxplane and its performance was compared to that of the baseline Albatross. The parasitic drag was estimated using handbook empirical methods based on the friction drag of a flat plate. The structural weight changes were estimated using "area weights" derived from the original Albatross. When the two aircraft were compared, at a cruise velocity of 22 ft/s, the boxplane, with roughly half the span of the original, showed a net drag reduction of approxiametly 0.36 lb, which can be deduced from a decrease of 0.81 lb of the induced drag plus an increase of the parasite drag of around 0.45 lb. Therefore, for an aircraft with half the span, easier to handle, and more practical, the drag is essentially reduced by 4.4%.