Spoiler Actuator Valve Linkage for Fail-Safe Droop Control
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Solution Overview
Problem
Aircraft spoilers face interference issues with wing flaps during electrical or hydraulic failures, particularly when in droop mode, leading to potential obstruction and movement complications due to the spoiler's own weight or pressure.
Innovation Solution
A valve and piston assembly with a mechanical link and an electrohydraulic servovalve system that allows negative stroke operation while ensuring the spoiler remains centered and does not interfere with the wing flap, even in failure scenarios, by using a check valve and solenoid valve configuration to manage fluid flow and maintain neutral position passively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the spoiler is allowed to droop (negative stroke) using a negative stroke of the piston rod, then the droop function is enabled for high lift maneuvers, but the spoiler may interfere with wing flap movement during electrical or hydraulic failures due to its own weight or pressure
Solution Approach 1:
The system dynamically switches between droop mode and fail-safe mode using a mode valve. During normal operation, the spoiler can droop for high lift maneuvers. Upon detecting electrical or hydraulic failure, the mode valve switches to passively center the spoiler and prevent interference with wing flap movement, providing adaptive response to different operational conditions.
Solution Approach 2:
A mode valve acts as an intermediary between the electrohydraulic servovalve and the actuator. This intermediate component enables the system to switch between different operational modes (droop mode and fail-safe mode) and ensures that during failures, the spoiler is passively centered to prevent interference with wing flap movement.
2Reliability
If an anti-extension valve is used to prevent extension during hydraulic pressure loss, then extension is prevented, but the spoiler may still drop to become aligned with the wing surface and cause spurious extension or interfere with flap movement
Solution Approach 1:
The mode valve is configured to proactively counteract the harmful effect of spoiler drooping during failure. By switching to fail-safe mode upon detecting hydraulic pressure loss, the system preemptively centers the spoiler to prevent both spurious extension and interference with wing flap movement, rather than merely reacting to the problem after it occurs.
3Reliability
If the EHSV is biased to retract the spoiler to zero position during electric power loss, then the spoiler is retracted to prevent excessive drag, but the system loses the ability to perform droop function or controlled movement
Solution Approach 1:
The system dynamically responds to different failure conditions. During electrical power loss, the EHSV bias retracts the spoiler to prevent excessive drag. During hydraulic failures, the mode valve switches to a configuration that passively centers the spoiler while maintaining operational flexibility for droop function when conditions permit.
4Manufacturing precision
If a mechanical stop is used to stop the piston rod at the zero position, then the zero position is defined, but the system cannot accommodate negative stroke operation for droop function
Solution Approach 1:
The valve system is segmented into multiple functional components (EHSV, mode valve, check valve, anti-extension valve) that can operate independently. This segmentation allows the mechanical stop to define the zero position while the mode valve and check valve enable negative stroke operation for droop function, resolving the contradiction between precise positioning and operational flexibility.
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
Enables reliable droop function and safe re-centering of the spoiler in case of electrical or hydraulic failures, allowing wing flap movement without interference, and permits manual operation by preventing hydraulic forces from obstructing maintenance.
Implementation Method 1
a check valve (130) in fluid communication with the second chamber (200b) of the actuator and configured to allow hydraulic fluid to flow from the second chamber (200b) to the first chamber (200a)
Implementation Method 2
a solenoid valve (140) in fluid communication with the check valve (130) and configured to switch between a first position in which the solenoid valve (140) allows hydraulic fluid to flow to the check valve (130)
Implementation Method 3
The valve is positioned between the hydraulic fluid supply and the actuator and is moveable, in response to an electric control signal, between a first position in which high pressure fluid flows from the supply into one chamber of the actuator housing
Data Source
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AI summary
An actuator control arrangement comprising: a hydraulic actuator (100) having a housing (200) and a piston rod (300) axially moveable within the housing between a neutral position, a retracted position and an extended position with respect to the housing in response to application of pressure to the piston rod; the arrangement further comprising a check valve (130) moveable between a first position (130X) providing a flow path between a pressure source (HP,LP) and the actuator, and a second position (130Y) in which the flow path is closed off; and characterised by a mechanical link (800) between the piston rod and the check valve, actuated in response to the piston rod passing a predetermined retracted position in a negative stroke direction, to set the check valve to the first position.