Scythe Wingtip Device Cutout Drag Reduction
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Solution Overview
Problem
Existing wingtip devices effectively reduce induced drag but often increase form, skin-friction, interference, and compressibility drag due to increased wetted area and aerodynamic incompatibility at the wing-wingtip interface.
Innovation Solution
The scythe wingtip device features a leading edge with aft sweep and a trailing edge with a smooth, continuous profile that includes a cutout with forward sweep, reducing the wetted area and maintaining a continuous surface contour to minimize form, skin-friction, interference, and compressibility drag while extending the wing's effective span.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the wing span is extended to reduce induced drag, then the wetted area increases, but the form drag, skin-friction drag, interference drag, and compressibility drag increase
Solution Approach 1:
The patent removes material from the trailing edge of the wingtip device by creating a cutout. This extraction of material reduces the wetted surface area of the wingtip device, thereby reducing skin-friction drag and form drag while maintaining the span-extending function for induced drag reduction
Solution Approach 2:
The patent employs curved leading and trailing edges on the wingtip device, creating a smooth, continuous surface contour. This curvature eliminates sharp edges and discontinuities that would otherwise generate interference drag and flow separation, while the cutout in the trailing edge further refines the surface geometry to minimize drag
2Loss of energy
If a wingtip device is added to extend effective span, then induced drag is reduced, but the aerodynamic incompatibility at the wing-wingtip interface increases interference drag
Solution Approach 1:
The patent creates a smooth, continuous surface contour at the wing-wingtip interface by curving the leading and trailing edges of the wingtip device. This continuous curvature eliminates sharp discontinuities and ensures smooth airflow transition across the interface, thereby minimizing interference drag while maintaining the span-extending function
3Strength
If the wetted area of the wingtip device is increased to maintain structural strength, then the form drag and skin-friction drag increase
Solution Approach 1:
The patent removes material from the trailing edge of the wingtip device by creating a cutout, thereby reducing the wetted surface area. This reduction in wetted area directly decreases skin-friction drag and form drag while the structural design maintains necessary strength through optimized material distribution
4Object-generated harmful factors
If the wingtip device has a continuous surface contour, then skin-friction drag is reduced, but the manufacturing complexity increases
Solution Approach 1:
The patent employs curved leading and trailing edges that create a smooth, continuous surface contour. These curved surfaces can be manufactured using standard composite layup techniques or metal forming processes, making the continuous contour achievable without excessive manufacturing complexity while effectively reducing skin-friction drag
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces induced drag while minimizing additional drag components, providing a practical solution for aircraft performance improvement by reducing fuel burn, noise, and emissions.
Implementation Method 1
the cutout reduces a wetted area of the winglet for reducing effects of skin-friction
Implementation Method 2
the cutout reduces a wetted area of the winglet for reducing effects of skin-friction, form, interference, and compressibility drag
Implementation Method 3
maintaining a continuous profile with the wing trailing edge for reducing effects of skin-friction, form, interference, and compressibility drag
Implementation Method 4
an extending member that extends from an outboard interface of a wing to increase an effective span of the wing for reducing induced drag
Implementation Method 5
the cutout reduces a wetted area of the winglet for reducing effects of skin-friction, form, interference, and compressibility drag
Data Source
AI summary
Wingtip devices configured to extend from the outboard ends of aircraft wings are designed to effectively reduce induced drag, but they necessarily produce form and skin-friction drag, and they may produce interference and compressibility drag. The present disclosure describes a scythe-shaped wingtip device (or ‘winglet’ or ‘extending member’) suitable for reducing the induced drag of an aircraft wing while minimizing other types of drag. A cutout in the wingtip device reduces the wetted area of the wingtip to minimize non-induced drag while the wingtip device still reduces induced drag like a conventional wingtip device. The cutout is configured in a trailing edge of the wingtip device.