Bistable Spoiler for Wing Gust Load Alleviation
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Solution Overview
Problem
Aircraft wing components face challenges in reducing weight while maintaining the ability to withstand gusts and aerodynamic loads, with existing morphing flow control devices struggling to accurately predict and manage localized loads, potentially triggering unwanted snap-through phenomena.
Innovation Solution
A flow control device that transitions between stable states in response to strain thresholds, allowing for passive activation and deactivation based on structural strain, enabling efficient gust load alleviation without active control systems.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the wing weight is reduced to improve fuel efficiency, then fuel efficiency improves, but the wing's ability to withstand gust loads and aerodynamic pressures deteriorates
Solution Approach 1:
The patent applies a dynamic flow control device that can actively change its shape and position in response to detected gust conditions. The device transitions from a retracted state during normal flight to an extended state when gusts are detected, allowing the wing to maintain structural integrity under reduced weight by dynamically managing aerodynamic loads rather than relying solely on increased structural mass.
2Measurement precision
If active control systems are used to manage flow, then flow control precision improves, but device complexity and weight increase
Solution Approach 1:
The patent employs a self-service control mechanism where the flow control device monitors its own structural strain and aerodynamic conditions to automatically determine when to transition between states. The device uses embedded sensors to detect strain thresholds and autonomously actuates without requiring complex external control systems, achieving precise flow management while minimizing system complexity and weight.
Solution Approach 2:
The patent implements a feedback mechanism where strain sensors continuously monitor the structural load on the wing and provide real-time data to the flow control device. When the strain exceeds a predetermined threshold indicating gust conditions, the feedback signal triggers the device to extend and modify the airflow, thereby reducing the effective load on the wing structure.
3Strength
If the flow control device responds to all aerodynamic pressure changes, then gust load alleviation improves, but unwanted snap-through phenomena during normal maneuvers increase
Solution Approach 1:
The patent uses preliminary action by pre-setting strain threshold values that distinguish between normal aerodynamic pressures during maneuvers and abnormal pressures during gusts. The flow control device is configured with hysteresis characteristics and threshold-based activation that prevents premature or unwanted snap-through during routine flight operations, while still providing rapid response when genuine gust conditions exceed the predetermined thresholds.
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 device effectively reduces aerodynamic loads on the aircraft wing by passively transitioning between states in response to structural strain, enhancing weight reduction and stability without compromising gust resistance.
Implementation Method 1
Shape adaptation can exploit structural elastic instabilities. Elastic instability refers to a temporary loss of stiffness of a structure, which is restored before irreversible deformation occurs.
Implementation Method 2
From this unstable equilibrium the structure will 'snap through' to a secondary state. A 'bi-stable' structure has two stable equilibrium states and an intermediate unstable equilibrium state.
Implementation Method 3
a flow control device with a device aerodynamic surface arranged on a structure with a structure aerodynamic surface such that strain in the structure is at least partially transferred to the flow control device
Data Source
AI summary
A flow control device on a structure such that strain in the structure is at least partially transferred to the flow control device is disclosed having at least two states, or shapes, separated by an elastic instability region. The flow control device is arranged to rapidly transition, or snap through, from the first state to the second state when strain in the structure exceeds an activation threshold of the flow control device. A spoiler on an aerofoil has a rest position where it is substantially flush with the low pressure surface and an activated position where it protrudes from the low pressure surface and modifies the airflow over that surface. The spoiler bends to move from the rest position to the activated position when the strain in the aerofoil crosses a threshold. The deployed spoiler reduces the lift on the aerofoil, acting to reduce the lift induced strain of the aerofoil to which the spoiler is attached.