http://handle.dtic.mil/100.2/ADA085203Inherent in the design optimization of wing span-distributed load (spanloader) aircraft is the lack of ground operational down bending load reaction capability of the wing structure. It is necessary to provide a means to react these down bending loads if the wing structural weight is minimized. Recent studies have provided wide tread landing gears as a means to react these down bending loads, limiting the operational capability of the aircraft where the tread width exceeds most existing airport taxiway or runway widths. This study examines the feasibility of replacing the wide tread gear with a peripheral jet air cushion landing system (PJ-ACLS) in combination with a minimum tread (75 feet) width gear. The PJ-ACLS is located adjacent to the wing tip and is used primarily as wing down bending load reaction device. The minimum tread width gear is retained to simplify takeoff and landing procedures and to reduce the magnitude of the lift required from the PJ-ACLS.
Studies were conducted to assess the technical feasibility and to evaluate the economics of a span-distributed loading aircraft relative to a conventional aircraft. A 700,000 kg (1,540,000-lb) aircraft with a cruise Mach number of 0.75 was found to be optimum for the specified mission parameters of a 272,155-kg (600,000-Ib) payload, a 5560-km (3000-n .mi.) range, and an annual productivity of 113 billion revenue-ton km (67 billion revenue-ton n. mi .). The optimum 1990 technology level span loader aircraft exhibited the minimum 15-year life-cycle costs, direct operating costs, and fuel consumption of all candidate versions.
Parametric variations of wing sweep angler thickness ratio, rows of cargo, and cargo density were investigated. The optimum aircraft had two parallel rows of 2.44 x 2.44-m (8 x 8-ft) containerized cargo with a density of 160 kg/cu m (10 Ib/cu ft) carried throughout the entire 101-m (331-ft) span of the constant chord, 22-percent thick, supercritical wing. Additional containers or outsized equipment were carried in the 24.4-m (80-ft) long fuselage compartment preceding the wing. Six 284,000-N (64,000-Ib) thrust engines were mounted beneath the 0.7-rad (40-deg) swept wing. Flight control was provided by a 36.6-m (120-ft) span canard surface mounted atop
the forward fuselage, by rudders on the wingtip verticals and by outboard wing flaperons.
Benefits of the spanloaded aircraft relative to a conventional aircraft with identical mission capability are: 11.7-percent lower direct operating and 15-year life-cycle costs, 8.2-percent less fuel consumption, 20.8-percent lighter operating weight, and a 10.4 percent smaller gross weight. Cargo loading and the 66.5-m (218-ft) main landing gear tread will pose potential airport compatibility problems.
The Lockheed-Georgia Company conducted a technical and economic assessment of span-distributed loading cargo aircraft concepts as part of its Independent Development Program. The approach, guidelines, and requirements outlined in NASA Request for Proposal 1-16-5603 provided the basis for the general plan followed in the Lockheed study. Several minor changes were made to the suggested guidelines, and some additional study
tasks were undertaken.
Monthly reports were submitted to Allen H. Whitehead, Jr., NASA's Span-Distributed Loading Aircraft Studies coordinator, to keep him informed of the latest progress on the Lockheed study. Several conferences, including mid-term and final presentations at the NASA-Langley facility on 23 October 1975 end 5 February 1976, respectively, were held to assure compatibility with the NASA efforts. Toward the end of the study, Lockheed and NASA agreed to make the results available in a NASA report to the general public • Funding to underwrite part of the cost of this publication was provided through Contract NAS 1-14383.
William M. Johnston" the Study Manager, and his Deputy, John C. Muehlbauer, were responsible for the overall direction of this study which was performed as part of a continuing preliminary design investigation of new aircraft concepts by the Transport Design Department - Roy H. Lange, Manager. Roy R. Eudaily coordinated the overall structures effort; specific responsibilities were as follows: Michael C. Campion - Loads, Charles M. Jenness - Flutter, Lewis B. Lineberger - Stress, and R. Earnest Stephens -Weights. Ben T. Farmer fulfilled the design requirements, Sterling G. Thompson performed the economic analysis, and John F. Honrath directed the aerodynamic performance and parametric activities. Other contributors to this study included: S. R. Anthony, J. A. Bennett, D. N. Byrne, B. N. Crenshaw, H. V. Davis, Jr., R. S. Ferrill, O. M. Hayes, J. G. Hewell, Jr., J. D. Sowers, V. L. Turner, and F. M. Wilson, Jr.