Propeller Gearbox Hydraulic Transfer Bearing Relocation
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Solution Overview
Problem
Existing turboprop engine pitch control systems face challenges with inaccessible and space-constrained hydraulic transfer bearing assemblies, which complicate maintenance and increase weight due to the location of these components in an envelope volume behind the propeller gearbox, often in a 'fire zone' and requiring separate passages.
Innovation Solution
The propeller blade pitch control system relocates the hydraulic transfer bearing within the propeller gearbox, allowing for easier access and reduced nacelle housing size, with a radially offset or in-line gearbox configuration that integrates hydraulic fluid controllers directly within the gearbox, enhancing maintenance accessibility and aerodynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the hydraulic transfer bearing assembly is located in the envelope volume behind the propeller gearbox, then the pitch control function can be achieved, but maintenance accessibility deteriorates and weight increases
Solution Approach 1:
The hydraulic transfer bearing assembly is extracted from the envelope volume behind the propeller gearbox and relocated to the front end of the propeller gearbox. This extraction eliminates the need for separate passages and improves maintenance accessibility while reducing the required nacelle housing size and weight.
Solution Approach 2:
The hydraulic transfer bearing assembly is merged with the propeller gearbox structure by relocating it to the front end of the gearbox. This integration eliminates the need for separate housing structures and passages, thereby reducing overall weight and improving maintenance access.
2Ease of operation
If the hydraulic transfer bearing assembly is located in the envelope volume behind the propeller gearbox, then the pitch control function can be achieved, but the nacelle housing size increases
Solution Approach 1:
The hydraulic transfer bearing assembly is extracted from the envelope volume behind the propeller gearbox and relocated to the front end of the propeller gearbox. This extraction eliminates the need for separate passages and reduces the required nacelle housing volume while improving maintenance accessibility.
Solution Approach 2:
The hydraulic transfer bearing assembly is relocated from a position behind the propeller gearbox to the front end of the gearbox, utilizing the longitudinal dimension of the gearbox structure. This dimensional relocation optimizes space utilization and reduces the overall nacelle housing volume.
3Ease of operation
If separate passages are used for hydraulic fluid flow, then the pitch control function can be achieved, but device complexity increases
Solution Approach 1:
The hydraulic fluid passages are merged with the propeller gearbox structure by relocating the transfer bearing assembly to the front end of the gearbox. This integration eliminates the need for separate passages and reduces system complexity while improving maintenance accessibility.
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 configuration improves maintenance accessibility, reduces weight, and enhances aerodynamics by moving the transfer bearing out of the 'fire zone and freeing up space, resulting in a more efficient and lightweight pitch control system.
Implementation Method 1
A hydraulic transfer bearing located between the first, rear end and the second, forward end of the propeller gearbox is operable to selectively permit a flow of hydraulic fluid from at least one hydraulic flow controller to the pitch change actuator
Data Source
AI summary
A propeller blade pitch control system includes a propeller hub for mounting at least one propeller blade, and a propeller shaft which rotates about an axis to rotationally drive the propeller hub. A pitch change yoke located within the propeller hub is configured to change a pitch of the at least one propeller blade in response to hydraulic fluid flow to a pitch change actuator. A propeller gearbox includes a first, rear end and a second, forward end located between the first, rear end and the pitch change yoke, and is configured to apply torque to the propeller hub. A hydraulic transfer bearing located between the first, rear end and the second, forward end of the propeller gearbox is operable to selectively permit a flow of hydraulic fluid from at least one hydraulic flow controller to the pitch change actuator.