Forward Swept Winglet Mass Balance Reduces Flutter

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Solution Overview

Problem

Aircraft wings with high aspect ratios face limitations in achieving a high lift-to-drag ratio due to increased weight, structural robustness requirements, and susceptibility to wing flutter, which are exacerbated by aft-swept winglets that add weight and increase polar moment of inertia at the wing tip.

Innovation Solution

The implementation of forward swept winglets, with upper and lower portions extending above and below the wing, respectively, and a mass balance positioned forward to reduce the polar moment of inertia and center of mass, thereby reducing flutter susceptibility and weight distribution behind the torsional axis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Loss of energy

If aft-swept winglets are used to increase wing span and improve L/D ratio, then aerodynamic efficiency is improved, but flutter susceptibility increases due to increased polar moment of inertia and weight at the wing tip

Engineering Contradiction:

Improvefuel consumptionVSAvoidflutter susceptibility

Core Design Contradiction:

Loss of energyVSReliability

Solution Approach 1:

The patent inverts the conventional aft-swept winglet design by using a forward-swept configuration. This reversal changes the direction of the winglet sweep from backward to forward, which fundamentally alters the mass distribution and moment of inertia characteristics, thereby reducing flutter susceptibility while maintaining aerodynamic benefits

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The patent changes the sweep angle parameter of the winglet from negative (aft-swept) to positive (forward-swept). This parameter change directly affects the polar moment of inertia and center of mass location, transforming the dynamic characteristics of the wing-tip structure to reduce flutter while preserving the span extension benefit

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If winglet span is increased to improve aerodynamic benefit and reduce induced drag, then L/D ratio improves, but structural weight and flutter susceptibility increase rapidly

Engineering Contradiction:

Improveinduced dragVSAvoidwinglet weight

Core Design Contradiction:

Loss of energyVSWeight of moving object

Solution Approach 1:

By inverting the sweep direction to forward-swept, the patent achieves a more favorable weight distribution for a given winglet span. The forward sweep configuration places mass forward of the wing tip, reducing the polar moment of inertia and allowing longer spans without proportionally increasing the weight penalty

Inventive Principle:

Principle #13The other way round (Inversion)

3Loss of energy

If high aspect ratio wings are used to improve L/D ratio, then aerodynamic efficiency improves, but wing weight increases due to stronger structure requirements to resist bending load

Engineering Contradiction:

Improvefuel consumptionVSAvoidwing weight

Core Design Contradiction:

Loss of energyVSWeight of moving object

Solution Approach 1:

The forward-swept winglet acts as a counterweight element that offsets the increased bending loads on high aspect ratio wings. By positioning mass forward of the wing tip, the configuration creates a balancing moment that reduces the net bending load on the wing root, allowing high aspect ratio designs without proportionally increased weight

Inventive Principle:

Principle #8Anti-weight (Counterweight)

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 enhances aerodynamic efficiency by reducing induced drag and wing flutter susceptibility, allowing for a longer winglet span without increasing weight or structural stress, thus improving fuel efficiency and operational safety.

Implementation Method 1

Wing flutter is a dynamic phenomenon in which an approximately vertical (flapping) motion of the wing couples with a torsional mode (wing twist), resulting in unacceptable shaking in the wing that can cause structural damage

Methodology Applied

Scientific EffectFlutter: Aeroelastic Flutter

Implementation Method 2

One factor affecting wing flutter susceptibility is reduction of the natural twisting frequency of the wing. The wing may be considered to be a torsional pendulum. Resistance to torsion is typically provided by the box or tube-like structure of the wing. Given the torsional rigidity provided by this structure, the frequency is primarily determined by the polar distribution of mass about a torsional axis of the wing structure as well as a spanwise distribution of this mass

Methodology Applied

Scientific EffectPolar moment of inertia: Moment of Inertia

Data Source

PatentEP2441670B1Forward swept winglet

Publication Date: 2019.07.24 THE BOEING CO

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Figure 3A

AI summary

An aircraft may include a pair of wings. A forward swept winglet may be attached proximate to a wing tip of each wing. The forward swept winglet may include a leading edge and a trailing edge. The leading edge of each winglet may extend from the wing at a predetermined forward sweep angle relative to a line perpendicular to a chord of the wing tip in a direction corresponding to a forward portion of the aircraft.