Tensioned Actuator Rod Assembly With Failure Indication for Blade Pitch
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Solution Overview
Problem
Actuator rods in blade pitch control systems, such as those in helicopter tail rotors, are prone to fatigue failure due to cyclic loads, leading to a lack of intrinsic fail-safe mechanisms and potential loss of yaw control if they fail.
Innovation Solution
The actuator rod assembly consists of a tubular outer rod and an inner rod, where the inner rod is tensioned to place the outer rod in compression, with an indicator washer for rotational fixation and release indicating failure, and keying formations to prevent relative rotation, allowing for continued operation and easy repair.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a single-piece actuator rod is used, then the structure is simple and easy to manufacture, but it lacks intrinsic fail-safe mechanism and can lead to loss of yaw control upon failure
Solution Approach 1:
The actuator rod is divided into an outer rod and an inner rod that are separate components. The inner rod can move independently within the outer rod, creating a segmented structure that provides fail-safe functionality while maintaining structural integrity through modular design.
Solution Approach 2:
The inner rod is nested within the outer rod, with the inner rod positioned inside the hollow interior of the outer rod. This nested configuration allows the inner rod to slide axially while maintaining containment, providing both structural simplicity and fail-safe capability.
2Reliability
If the actuator rod is designed with fail-safe mechanism, then reliability is improved, but detection of rod failure becomes more difficult
Solution Approach 1:
An indicator element is provided that changes its rotational state or position to indicate the axial position of the inner rod. This visual indicator allows pilots or maintenance personnel to easily detect rod failure or improper extension without complex instrumentation, maintaining simplicity while enabling failure detection.
3Stability of the object's composition
If the inner rod is tensioned to place the outer rod in compression, then structural stability is improved, but the complexity of assembly and tensioning increases
Solution Approach 1:
The inner rod is pre-tensioned using a tensioning device such as a lock nut or threaded mechanism before final assembly. This preliminary tensioning action establishes the required compressive load on the outer rod, ensuring structural stability is achieved during the assembly process itself rather than requiring post-assembly adjustments.
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 design provides an intrinsic fail-safe mechanism, allowing continued safe operation and easy detection of rod failure, enhancing reliability and safety by maintaining alignment and load support after outer rod failure, and enabling pre-flight integrity checks without disassembly.
Implementation Method 1
The inner rod is tensioned against the outer rod so as to place the outer rod in compression
Implementation Method 2
an indicator washer frictionally clamped in a load path between the inner and outer rods, so as to be rotationally fixed when the inner rod is tensioned and rotationally released when the tension is lost
Data Source
AI summary
An actuator rod assembly for a blade pitch control system is provided herein. The actuator rod assembly includes a tubular outer rod and an inner rod. The outer rod has a first end and a second end. The inner rod has a first end and a second end and extends through the tubular outer rod. The inner rod is tensioned against the tubular outer rod so as to place the outer rod in compression.