Aircraft Gearbox Auxiliary Oil Pump for Windmilling Lubrication
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Solution Overview
Problem
Aircraft engine gearboxes are at risk of damage and seizure during in-flight windmilling due to inadequate lubrication when the primary oil system loses power, as existing ground-based auxiliary systems are insufficient to manage the higher oil flow requirements at higher windmilling speeds.
Innovation Solution
An auxiliary oil system with an electric pump that can be selectively activated to supply oil to the gearbox bearings during flight, independent of the primary oil system, using sensors and control electronics to detect windmilling or oil pressure failures and activate the pump as needed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a mechanically driven primary oil system is used, then lubrication is provided during normal engine operation, but the system fails to provide lubrication during engine shutdown in flight
Solution Approach 1:
The oil system is divided into two independent subsystems: a primary mechanically driven oil system for normal operation and an auxiliary electrically driven oil system for emergency windmilling protection. This segmentation allows each system to be optimized for its specific function and ensures that failure of one does not compromise the other.
Solution Approach 2:
An auxiliary electric pump acts as an intermediary system that activates when the primary oil system fails. This intermediary provides backup lubrication capability using electrical power instead of mechanical drive, ensuring continuous protection of the gearbox during engine shutdown scenarios.
2Productivity
If ground-based auxiliary oil systems are used, then windmilling protection is provided at low speeds, but the systems cannot meet higher oil flow requirements at in-flight windmilling speeds
Solution Approach 1:
The auxiliary electric pump is specifically designed and sized to deliver the higher oil flow rates required for in-flight windmilling conditions (up to 500 rpm) compared to ground windmilling (up to 100 rpm). The system parameters including pump capacity, pressure, and flow rate are optimized for the more severe in-flight operating conditions.
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 electric auxiliary oil system reduces the risk of gearbox damage and drag on the airframe by providing continuous lubrication during engine shutdowns, improving system reliability and reducing energy wastage by only operating when necessary, and allowing for flexible placement and maintenance access.
Implementation Method 1
an auxiliary oil system comprising an electric pump arranged to supply the bearings of the gearbox with oil in response to shut-down of the engine core in flight
Data Source
AI summary
A method (500) and apparatus (50, 60) for lubrication of a gearbox (30) of an aircraft engine comprise provision (502) of oil to the gearbox (30) through a primary oil system (50) driven by a core (11) of the engine (10) in normal conditions; detection (504) of windmilling conditions and/or failure of the primary oil system (50); and in response to the detected condition or failure, activation (506) of an electric pump (61) of an auxiliary oil system (60), to provide oil to the gearbox (30).