SYMPOSIA PAPER Published: 01 January 1992

Composite Material Stub-Blade Wing Joint


A design study to determine the viability of a stub-blade wing joint for HALE (high-altitude, long-endurance) aircraft is presented. The resulting wing joint design uses advanced composite materials and is capable of carrying moderately high bending, shear, and torsional loads. The stub-blade concept is similar to the wing joint design used on sailplanes and is particularly applicable to a large-span, high-aspect-ratio, unswept wing that uses a single-cell wing box to carry spanwise loads. This wing structure and geometry are typical of many HALE aircraft. The stub-blade joint can be located at any wing station and uses “pin-in-a-socket” action to transfer loads from the outboard to inboard wing box. Justification and criteria for material selection are presented. Extensive use of graphite/epoxy, co-cured and bonded structure is made to achieve a minimum weight design. Major design drivers include minimum weight, ease of fabrication, and ease of repeated assembly and disassembly of the joint. The latter would be desirable on a large-span aircraft for which hangar or transportation limitations would require repeated removal of outer wing sections. A FORTRAN program was developed to optimize the blade length based on weight, and a NASA Structural Analysis (NASTRAN) model of the stubblade design was constructed to investigate the distribution of internal loads. The stub-blade joint presented in this paper was sized to loads generated for a representative baseline HALE vehicle. This Lockheed Baseline HALE Aircraft is an unmanned vehicle capable of reaching an altitude of 27 432 m (90 000 ft) and features a 8163-kg (18 000-lbs) gross weight and 80.5-m (264-ft) wingspan. The stub-blade wing joint design is weight competitive with the traditional tensiontype wing joint and offers attractive features such as ease of assembly and disassembly, ease of fabrication, and aerodynamic smoothness.

Author Information

Franklin, WM
Advanced Development Projects, Lockheed Aeronautical Systems Co., Burbank, CA
Kreimendahl, BW
Advanced Development Projects, Lockheed Aeronautical Systems Co., Burbank, CA
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Developed by Committee: D30
Pages: 264–278
DOI: 10.1520/STP20161S
ISBN-EB: 978-0-8031-5184-0
ISBN-13: 978-0-8031-1426-5