Downward Canted Wing Tip Device Drag Reduction
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Solution Overview
Problem
Existing wing tip designs for aircraft, such as winglets, increase induced drag while also enhancing wing root bending moment, leading to structural strength and weight penalties.
Innovation Solution
A downwardly canted tip device with a swept leading edge and reducing chord, which influences span loading and vortex sheet, positioning the tip vortex outboard and reducing trailing vortex intensity, combined with a raked back trailing edge to minimize root bending moment, and incorporating a feature for enhanced ground clearance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional upwardly canted winglets are fitted to reduce induced drag, then induced drag is reduced, but wing root bending moment increases significantly
Solution Approach 1:
The patent inverts the conventional upward cant angle to a downward cant angle (between 5 and 30 degrees downward). This inversion changes the direction of the lift vector produced by the tip device, so that instead of increasing the root bending moment as conventional upward-canted winglets do, the downward-canted configuration reduces the root bending moment while still effectively reducing induced drag through vortex manipulation
Solution Approach 2:
The patent changes key geometric parameters of the tip device: the cant angle is set downward rather than upward, the leading edge sweep angle is optimized (between 15 and 45 degrees), and the chord distribution is carefully controlled. These parameter changes create a tip device that generates a beneficial downward lift component that reduces root bending while maintaining drag reduction effectiveness
2Loss of energy
If wing tip devices are added to reduce induced drag, then induced drag is reduced, but device weight and wetted area increase
Solution Approach 1:
The patent optimizes the geometric parameters of the tip device to achieve an favorable balance between drag reduction and weight penalty. The downward cant angle, leading edge sweep, and chord distribution are specifically designed to maximize aerodynamic efficiency while minimizing the amount of structural material required, thereby reducing the weight of the tip device itself
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
The solution effectively reduces induced drag with a lower increase in wing root bending moment compared to conventional winglets, while maintaining aerodynamic performance and avoiding wave drag penalties, thus offering a favorable balance between drag reduction and structural integrity.
Implementation Method 1
positioning the tip vortex outboard and reducing trailing vortex intensity
Implementation Method 2
utilise the cross flow occurring around the tip to reduce the intensity and concentration of the trailing vortex
Implementation Method 3
the additional lift which they produce and its siting at the maximum span position
Implementation Method 4
increase in the wing root bending moment in flight
Data Source
AI summary
A tip device to act as an outboard continuation of an aircraft wing or other aerodynamic lifting surface has a downward cant angle, a leading edge swept back in relation to the leading edge of the inboard lifting surface, and a chord reducing in the outboard direction of the device. A favourable balance between induced drag reduction and increased wing root bending moment can thereby be achieved. Preferably the device also has an upwardly canted portion at its root end so that the downward cant commences from a relatively elevated spanwise location, thereby alleviating any ground clearance problems.