No-back Device Backlash Adjustment for Flight Control Actuators
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Solution Overview
Problem
Existing no-back devices for flight control surface actuators require cumbersome adjustments to manage backlash, which increases due to wear over time, affecting the aircraft's trim stability.
Innovation Solution
A backlash adjuster mechanism is integrated into the no-back device, allowing selective adjustment of backlash lengths by moving a threaded nut relative to the screw, with biasing springs and brake assemblies to control axial movement and prevent unwanted rotation, enabling easy adjustment without disassembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a no-back device is used to prevent back-driving of the screw, then the aircraft trim stability is improved, but the backlash increases due to wear over time requiring cumbersome adjustments
Solution Approach 1:
The patent implements a dynamic backlash adjustment mechanism where the adjustment member can be rotated to change the axial position of the braking member relative to the screw. This allows the backlash to be dynamically adjusted from a fixed position, enabling the system to adapt to wear over time while maintaining ease of operation through a simple rotational motion rather than cumbersome disassembly and repositioning procedures.
Solution Approach 2:
The adjustment member is designed to be accessible and operable directly on the actuator without requiring disassembly or specialized tools. The operator can independently adjust the backlash by rotating the adjustment member, allowing the system to self-maintain its performance characteristics without external intervention or complex maintenance procedures.
2Manufacturing precision
If the backlash is reduced to improve precision, then the manufacturing precision is improved, but the device complexity increases due to additional adjustment mechanisms
Solution Approach 1:
The adjustment member serves multiple functions: it positions the braking member axially to control backlash, provides a means to lock the braking member in position, and can potentially serve as an adjustment indicator. By combining multiple functions into a single component, the patent achieves precise backlash control without proportionally increasing device complexity.
Solution Approach 2:
The adjustment member is nested within the existing no-back device structure, fitting into the available space around the screw and braking member assembly. This nested configuration allows the adjustment mechanism to be integrated into the existing design without requiring additional external components or increasing the overall footprint of the device.
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 solution simplifies backlash adjustment, reducing maintenance costs and frequency by allowing precise control of backlash lengths, enhancing the stability and reliability of flight control surface actuators.
Implementation Method 1
moving a threaded nut relative to the screw
Implementation Method 2
biasing springs and brake assemblies to control axial movement
Implementation Method 3
brake assemblies to control axial movement and prevent unwanted rotation
Data Source
AI summary
Disclosed is an actuator for varying the position of a flight control surface on an aircraft, wherein the actuator comprises a no-back device including a backlash adjuster, which is arranged to select a plurality of different backlash lengths. The backlash adjuster may be a nut which moves relative a housing of the no-back device by rotating the nut. Also disclosed is a method of adjusting the backlash (B) in a flight control surface actuator, by moving the backlash adjuster axially to adjust the backlash (B) to a desired value.