Dual-Actuator Blade Pitch Control with Series Linkages
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Solution Overview
Problem
Variable pitch propeller and fan systems face safety risks due to potential failures, particularly when transitioning from positive to negative pitch angles, leading to overspeed or loss of engine function without adequate safety features.
Innovation Solution
A dual-actuator system with series-connected linkages that allows each actuator to override the other, incorporating hydraulic and electrical power sources, and a locking mechanism to prevent unintended pitch variations, ensuring safe operation and reducing the risk of system failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single actuator is used to vary blade pitch, then the system is simpler, but the reliability is insufficient due to risk of overspeed or loss of engine function upon failure
Solution Approach 1:
The actuation system is divided into two independent actuators (first and second actuators) that can operate separately or together. Each actuator has its own linkage system, allowing independent control and override capability. This segmentation provides redundancy so that if one actuator fails, the other can still control blade pitch, preventing overspeed or loss of engine function.
Solution Approach 2:
The system incorporates safety features and operating procedures in advance to mitigate potential failures. The dual-actuator design with override capability acts as a pre-prepared safety mechanism that prevents catastrophic failures before they can occur, rather than responding after a failure has happened.
2Adaptability or versatility
If blade pitch can transition from positive to negative angle for thrust reversal, then thrust reversal capability is achieved, but the risk of fan overspeed increases
Solution Approach 1:
The system requires that the second actuator be moved away from its end of range position before the locking mechanism can be opened to allow transition to negative pitch angles. This preliminary action ensures that the second actuator is functional and can override the first actuator if needed, providing a safety check before enabling thrust reversal that prevents fan overspeed.
Solution Approach 2:
A locking mechanism acts as an intermediary between the actuators and the blade pitch transition. This locking mechanism controls when the transition from positive to negative pitch angles can occur, providing an additional layer of safety by preventing unauthorized or unsafe transitions that could cause fan overspeed.
3Adaptability or versatility
If the first actuator is used for reverse thrust production, then thrust reversal is enabled, but the risk of inadvertent operation increases
Solution Approach 1:
The system requires that the second actuator be moved away from its end of range position before the locking mechanism can be opened to allow the first actuator to vary blade pitch for reverse thrust. This preliminary action serves as a safety check to ensure the second actuator is functional and can override if needed, preventing inadvertent reverse thrust operation.
Solution Approach 2:
The locking mechanism provides feedback control by monitoring the position of the second actuator and only allowing the first actuator to operate when the second actuator is in a safe position. This feedback mechanism prevents inadvertent operation by ensuring the system is in the correct state before enabling reverse thrust capability.
Data Source
AI summary
An actuation system is provided for varying the pitch of the blades of a variable pitch fan or propeller. The actuation system includes a first actuator and a second actuator. The actuation system further includes a first linkage which operably connects the first actuator to the blades such that operation of the first actuator varies the pitch of the blades via the first linkage. The actuation system further includes a second linkage which operably connects the second actuator to the first actuator such that operation of the second actuator varies the pitch of the blades by series connection of the second linkage to the first linkage.