Staggered Dual Winglet System for Aircraft Drag Reduction
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Solution Overview
Problem
The addition of traditional winglets to aircraft wings increases the bending moment, leading to a weight penalty and potential drag issues, while also risking wing tip strikes during takeoff and landing due to reduced ground clearance.
Innovation Solution
A dual-winglet system is introduced, where an upper and lower winglet are staggered and overlapping along the chord of the main wing tip, with a spanwise profile of the lower winglet configured to provide sufficient span without sacrificing ground clearance, and both winglets extend relative to the main wing tip, reducing the overall bending moment and drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If traditional single large winglets are added to increase lift and reduce drag, then aerodynamic performance is improved, but the bending moment on the wing increases leading to weight penalty
Solution Approach 1:
The patent divides a single large winglet into multiple smaller winglets (typically three: two lower winglets and one upper winglet, or vice versa). This segmentation reduces the bending moment on the wing by distributing the aerodynamic loads across multiple smaller attachment points rather than one large attachment point, thereby reducing the required wing structure weight while maintaining drag reduction benefits.
Solution Approach 2:
The patent arranges winglets in a vertical stack configuration along the span of the wing tip, utilizing the vertical dimension to distribute aerodynamic forces. By stacking winglets vertically rather than using a single large horizontal extension, the bending moment on the wing is reduced while maintaining effective wingtip vortex control for drag reduction.
2Loss of energy
If traditional single large winglets are added to improve aerodynamic performance, then lift and drag are optimized, but ground clearance is reduced risking wing tip strikes
Solution Approach 1:
By segmenting the winglet system into multiple smaller units stacked vertically, the overall horizontal span is reduced compared to a single large winglet providing equivalent aerodynamic benefit. This reduced horizontal span increases ground clearance and eliminates the risk of wingtip strikes during takeoff and landing while maintaining drag reduction performance.
3Weight of moving object
If multiple winglets are stacked vertically to reduce bending moment, then wing structure weight is reduced, but negative interference between winglets may increase drag
Solution Approach 1:
The patent optimizes the local geometry of each individual winglet in the stack, including airfoil section, twist distribution, and incidence angles, to minimize adverse interactions between adjacent winglets. By carefully designing the local characteristics of each winglet and their spacing, negative interference effects are minimized while maintaining the weight benefits of the segmented configuration.
Data Source
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AI summary
A winglet system for a wing of an aircraft is provided. The winglet system comprises an attachment end for attachment to a main wing of the aircraft, an upper winglet and a lower winglet. The upper and lower winglets are staggered and also overlap one another along the chord of the attachment end. A spanwise profile of the lower winglet has a midpoint where a slope of the spanwise profile at a point outboard of the midpoint is inclined more upwardly than a slope of the spanwise profile at the midpoint. The configuration of the winglet system may provide benefits such as a reduced bending moment and reduced negative interference between the winglets while also managing ground clearance.