Moveable Wing Tip Actuation With Inertia Tuning for Flutter Stability
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Solution Overview
Problem
Existing aircraft wings with moveable wing tip devices face challenges in managing large loads and wing root bending moments, particularly during high-load events, which can lead to heavy wing designs and increased flapping frequencies, affecting flutter stability.
Innovation Solution
The implementation of a rotatable wing tip device with an actuation system comprising a motor, geared rotary actuators, reduction gearbox, and a clutch, along with a mass disposed radially outward on a shaft, increases rotational inertia to reduce flapping frequency and enhance flutter speed, while allowing the wing tip device to move freely under aerodynamic forces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the wing tip device is made heavier to reduce flapping frequency, then flutter stability is improved, but the overall wing weight increases
Solution Approach 1:
The invention applies local quality by placing a mass specifically at the wing tip device rather than distributing weight throughout the entire wing. This localized mass concentration at the tip creates the necessary rotational inertia to reduce flapping frequency and improve flutter stability without requiring a proportional increase in overall wing weight. The mass is positioned radially outwardly from the shaft to maximize its moment of inertia effect.
Solution Approach 2:
The invention utilizes another dimension by fixing the mass radially outwardly from the shaft, creating a three-dimensional distribution of mass that optimizes the moment of inertia. This radial positioning in the third dimension (distance from the rotation axis) is more effective than simply increasing mass along the wing span, as the moment of inertia depends on the square of the radial distance from the axis of rotation.
2Force
If the wing tip device is allowed to move freely under aerodynamic forces, then load alleviation is achieved, but control over flapping frequency is lost
Solution Approach 1:
The invention applies self-service by allowing the wing tip device to move freely under aerodynamic forces without active control systems. The passive mass attached to the shaft automatically provides the necessary rotational inertia to control flapping frequency, and the device self-regulates its movement based on aerodynamic loading conditions. The mass effectively serves itself by utilizing the existing aerodynamic forces to achieve both load alleviation and frequency control.
Solution Approach 2:
The invention utilizes parameter changes by modifying the physical parameter of moment of inertia through the addition of mass. This changes the dynamic characteristics of the wing tip device, allowing it to maintain controlled flapping frequency even when moving freely under varying aerodynamic forces. The altered inertial parameter enables the device to respond differently to the same aerodynamic inputs.
3Speed
If a mass is added to the wing tip device itself, then rotational inertia is increased, but the additional weight is excessive
Solution Approach 1:
The invention uses an intermediary approach by attaching the mass to the shaft that drives the geared rotary actuator, rather than directly to the wing tip device. This intermediary positioning allows the mass to influence the rotational dynamics of the wing tip device through the gear mechanism. The shaft acts as a mediator, transmitting the inertial effects of the mass to the wing tip device while allowing for a more efficient weight distribution.
Solution Approach 2:
The invention applies another dimension by positioning the mass radially outwardly from the shaft axis rather than along the wing span. This radial positioning in the dimension perpendicular to the wing surface maximizes the moment of inertia for a given mass, as the moment of inertia is proportional to the square of the radial distance from the rotation axis. This dimensional change achieves the desired inertial effect with minimal mass.
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 the wing's required structural weight and enhances flutter stability by minimizing the gradient of flapping frequency increase with aircraft speed, allowing for a lightweight design that can manage high loads and comply with airport gate limits.
Implementation Method 1
the shaft is fixed in rotation to a mass disposed radially outwardly from the shaft... the rotational inertia of the wing tip device is increased when it rotates relative to the fixed wing
Data Source
AI summary
An aircraft wing is disclosed having a fixed wing with a tip, and a wing tip device rotatably mounted on a hinge at the tip of the fixed wing, such that the wing tip device is rotatable about the hinge, and an actuation system for rotating the wing tip device about the hinge. The actuation system includes a motor, at least one geared rotary actuator, a reduction gearbox, a clutch for selectively decoupling rotation of the motor from rotation of the geared rotary actuator, the geared rotary actuator is driveable by the motor and arranged to convert rotary motion into a different rotary motion and is arranged to rotate the wing tip device relative to the tip of the fixed wing. The clutch is coupled to the geared rotary actuator by a shaft and the shaft is fixed in rotation to a mass disposed radially outwardly from the shaft.