Aircraft Rudder Shaft Assemblies for Pedal Link Failure Tolerance
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In fly-by-wire aircraft rudder systems, a disconnect or failure of the rudder pedal link can lead to significant unwanted rudder changes, increased flight crew workload, and reduced controllability, especially when one pilot loses resistance from the centering unit, causing unclear rudder trim position indications.
Innovation Solution
A rudder system with dual shaft assemblies, each equipped with a centering unit and a rudder trim link, ensures continuous functionality and resistance to pedal movement, providing clear trim position indications even after a pedal link failure, using a pedal input link and rudder trim link to synchronize the shaft assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single rudder pedal link is used to connect both pilots' pedals, then the system structure is simplified, but the reliability decreases significantly when the link disconnects or fails
Solution Approach 1:
The patent divides the rudder control system into two independent shaft assemblies (first shaft assembly and second shaft assembly), each with its own centering unit and pedal link. This segmentation ensures that a failure in one shaft assembly does not affect the other, maintaining reliability while using relatively simple individual structures.
Solution Approach 2:
The patent changes the system architecture from a single shared pedal link to dual independent shaft assemblies with separate centering units. This parameter change transforms the failure mode from system-wide to localized, allowing the system to maintain functionality even when one shaft assembly experiences a pedal link disconnection.
2Device complexity
If the rudder pedal link disconnects, then the structural simplicity is maintained, but the handling qualities deteriorate due to loss of resistance and unclear trim position indications
Solution Approach 1:
By segmenting the rudder control into two independent shaft assemblies, each with its own centering unit, the patent ensures that one assembly can continue to provide proper resistance and trim position indication even when the other assembly's pedal link disconnects.
Solution Approach 2:
The patent provides beforehand cushioning by having redundant centering units in each shaft assembly. When a pedal link disconnects, the intact centering unit in its corresponding shaft assembly continues to provide resistance and trim position feedback, cushioning the impact of the failure on handling qualities.
3Reliability
If one pilot loses resistance from the centering unit due to pedal link failure, then the system structure remains intact, but the information feedback to the pilot is lost
Solution Approach 1:
The patent segments the information feedback system into two independent channels, one for each pilot. Each shaft assembly has its own centering unit that provides trim position indication to its corresponding pilot. When one shaft assembly fails, the other continues to provide accurate trim position information to its pilot without being affected by the failure.
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 system maintains improved handling qualities and reduces pilot workload by ensuring both shaft assemblies function independently, automatically returning to the rudder trim position and providing clear trim position indications, minimizing unwanted rudder changes.
Implementation Method 1
The centering unit includes a spring that applies a force to the shaft that resists rotation of the shaft away from a position corresponding to the rudder trim position
Data Source
AI summary
A rudder system of an aircraft includes a first shaft assembly and a second shaft assembly. Each of the first shaft assembly and the second shaft assembly includes a shaft, a trim crank coupled to the shaft, and a pedal crank. The trim crank is configured such that rotation of the trim crank causes rotation of the shaft, and pedal crank is configured such that rotation of the pedal crank causes rotation of the shaft without rotation of the trim crank. The rudder system includes a pedal input link configured to couple the pedal crank of the first shaft assembly and the pedal crank of the second shaft assembly together. The rudder system also includes a rudder trim link configured to couple the trim crank of the first shaft assembly and the trim crank of the second shaft assembly together.