Split Unison Ring Bearing Layout for Propeller Pitch Failover
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Solution Overview
Problem
Contra-rotating propeller systems in aircraft face challenges in maintaining control and preventing propeller overspeed during engine shutdown, leading to potential loss of control and mission abortion due to unfeathered propellers and failure of pitch control systems.
Innovation Solution
A unison ring system with separately controllable first and second unison ring portions, mechanically linked by a bearing, allows for maintained control of propeller pitch even in the event of actuation system failure, enabling the aircraft to complete its mission at reduced efficiency and preventing propeller overspeed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pitch lock mechanism is provided to lock propeller blades in current position during failure, then propeller overspeed is prevented, but the aircraft mission must be aborted and control is lost
Solution Approach 1:
The unison ring is divided into two separate portions (first unison ring portion and second unison ring portion) that can operate independently. Each portion controls one propeller assembly, allowing the operational portion to continue functioning even when the other fails, thus maintaining mission capability while preventing overspeed
Solution Approach 2:
The bearing is pre-positioned within the co-operating bearing location portions to enable automatic mechanical linkage between the two unison ring portions. This preliminary arrangement ensures that if one actuating system fails, the other can immediately drive the failed portion through the bearing without requiring additional control systems
2Ease of operation
If separate actuating systems are used for each unison ring portion to maintain independent control, then each propeller assembly can be controlled independently, but device complexity increases
Solution Approach 1:
The system dynamically adapts its configuration based on operational needs. During normal operation, both unison ring portions are separately controllable for optimal performance. During failure conditions, the system automatically transitions to a coupled mode where the bearing mechanically links the portions, allowing the operational actuating system to control both propeller assemblies
3Reliability
If a bearing is used to mechanically link the two unison ring portions, then control is maintained during actuating system failure, but the system becomes heavier compared to separate independent systems
Solution Approach 1:
The bearing is integrated directly within the co-operating bearing location portions of the two unison ring portions, merging the linkage function into the existing structural components rather than adding a separate external linkage mechanism. This reduces overall system weight while maintaining the fail-safe control capability
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 ensures safe feathering of propellers and maintains aircraft control during engine shutdown, reducing the risk of loss of control and allowing mission completion, while being lighter and more economical than traditional designs.
Implementation Method 1
The first unison ring portion and the second unison ring portion are mechanically linked to one another by a bearing
Data Source
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AI summary
The second unison ring portion(140) is co-axial with the first unison ring portion (110). The first unison ring portion comprises a first unison ring (120) and a first bearing location portion (130), and the second unison ring portion comprises a second unison ring (150) and a second bearing location portion (160). The first bearing location portion is co-axial with the first unison ring and projects axially from the first unison ring, while the second bearing location portion is co-axial with the second unison ring and projects axially from the second unison ring. The first bearing location portion comprises a radially outwardly opening groove (132), and the second bearing location portion comprising a radially inwardly opening groove 162). The first unison ring portion and the second unison ring portion are positioned with the first bearing location portion being concentric with the second bearing location portion thereby defining an annular cavity (190) therebetween.