D-Truss Wing Structure for an Unmanned Aerial Vehicle Lightweight Composite Wing Architecture for Long-Endurance UAVs

This patent covers a D-truss wing structure for unmanned aerial vehicles in which three tubular spars carry bending loads while a rigid sandwich shell and a shear web form a D-shaped cross-section, combining structural efficiency with light weight for extended-endurance drone operations.

The Problem

Wing design for unmanned aerial vehicles involves a set of competing demands that are more acute than in manned aircraft. UAVs — particularly those designed for extended endurance, persistent surveillance, or long-range operation — must carry their aerodynamic loads with the minimum possible structural weight, because every gram of structure displaces payload or fuel. At the same time, wings must survive the repeated bending, torsion, and shear stresses of flight, and must tolerate thermal expansion and contraction as the vehicle cycles between altitude temperatures and ground temperatures. Traditional UAV wing structures often use a single main spar with ribs and a covering skin, which can be adequate for small or short-endurance platforms but may be suboptimal for larger vehicles where bending stiffness and torsional rigidity are both critical. A D-box structure – in which the front portion of the wing cross-section forms a closed D-shaped cell – offers a known solution to torsional stiffness, but manufacturing it efficiently in composite materials and accommodating thermal expansion without cracking the composite shell has remained an engineering challenge.

What This Invention Does

AeroVironment’s invention provides a wing structure in which three tubular members — a leading edge tube, an upper tube, and a lower tube — form the primary bending-load-carrying framework. Upper rib members connect the leading edge tube to the upper tube; lower rib members connect the leading edge tube to the lower tube. Between the leading edge tube and the upper tube, a rigid sandwich shell closes the forward face of the D. Between the upper tube and the lower tube, a sandwich shear web forms the vertical back face. Together, the rigid sandwich shell and the shear web create a D-shape in cross-section. The rigid sandwich shell incorporates one or more expansion joints — channels running between the leading edge tube and the upper tube — to accommodate differential thermal expansion without inducing damaging stresses in the composite face sheets. Cross-bracing members between lower rib members maintain geometry under load. A polyvinyl fluoride (PVF) film covers the structure, bridging over the expansion joint channels to provide an aerodynamically clean airfoil surface.

Key Features

• Three-spar bending framework. All bending loads are carried by the leading edge tubular member, the upper tubular member, and the lower tubular member, which act collectively as a truss, distributing bending efficiently and allowing the shell and shear web to carry torsion rather than bending.
• D-shaped torsion cell. The combination of the rigid sandwich shell and the shear web creates a closed D-shaped torsion box, providing excellent torsional stiffness relative to weight, which is critical for aerodynamic efficiency and control authority.
• Expansion joints in the sandwich shell. Joints running between the leading edge tube and the upper tube break the rigid sandwich shell into panels that can expand and contract independently, preventing thermally induced cracking in the composite material during the temperature cycles experienced in flight.
• Sandwich composite construction. The rigid sandwich shell comprises two thin composite face sheets of carbon fibre and epoxy separated by a low-density foam or honeycomb core, optimising the stiffness-to-weight ratio of the shell component.
• PVF film covering. A polyvinyl fluoride film (such as DuPont Tedlar) is applied over the structure to form the outer aerodynamic skin, spanning the expansion joint channels without bonding into them, preserving the thermal relief function while providing a clean surface for aerodynamic performance.

Who Is Behind It?

The applicant is AeroVironment, Inc., a California-based company that is one of the leading manufacturers of small and tactical unmanned aircraft systems, with products used across military, government, and commercial sectors. The sole named inventor is Greg T. Kendall. The application is a divisional of AU 2021216411, the national phase of PCT/US2021/016735 filed 5 February 2021, with priority to US Provisional Application 62/970,827 filed 6 February 2020. The Australian patent attorney is Spruson and Ferguson in Sydney.

Why It Matters

Unmanned aerial vehicles are seeing rapid uptake across Australian defence, border security, agriculture, resources, and emergency services applications. Structural efficiency directly determines the endurance, payload capacity, and operational range of a UAV, making wing structure patents core to the competitive position of UAV manufacturers. AeroVironment supplies tactical UAV platforms to the Australian Defence Force and allied militaries, and improvements to wing structure that extend endurance or reduce operating costs have direct procurement relevance. The D-truss architecture described in this patent is applicable to fixed-wing UAVs in the class used for persistent surveillance, disaster response, and environmental monitoring — all areas of active operational need in Australia’s diverse geographic context.

Related Concepts

The D-truss architecture belongs to a family of torsion box wing designs used across both manned and unmanned aircraft. The core trade-off in UAV structural engineering is stiffness-to-weight ratio: composite materials such as carbon fibre reinforced polymer offer exceptional specific stiffness but must be engineered to handle the thermal and mechanical cycling of operational flight.

Extended-endurance fixed-wing UAVs are increasingly central to intelligence, surveillance, and reconnaissance (ISR) operations, where wing structural efficiency directly determines loiter time, payload capacity, and operational range – making structural patents a key element of competitive differentiation for UAV manufacturers.

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AU 2026201841 was published in the Australian Official Journal of Patents on 2 April 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.