RAT Pump Controller Prevents Stall via Frequency Feedback
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Solution Overview
Problem
Aircraft hydraulic systems face challenges in maintaining stable hydraulic power during emergency situations, such as engine failure, where Ram Air Turbines (RATs) may experience fluctuations in rotational frequency due to wind interruptions, leading to potential stall conditions and loss of hydraulic pressure.
Innovation Solution
An electronic controller is integrated with a Ram Air Turbine (RAT) variable displacement hydraulic pump system, utilizing a permanent magnet generator (PMG) to monitor rotational frequency and adjust the swash plate position via an electro-mechanical servo, ensuring the hydraulic pump operates above a targeted frequency and maintains regulated fluid pressure, even during wind interruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the RAT variable displacement hydraulic pump is used to provide emergency hydraulic power, then hydraulic power is available during engine failure, but the turbine rotational frequency fluctuates due to wind interruptions causing potential stall conditions
Solution Approach 1:
The hydraulic pump is designed with variable displacement capability, allowing the pump flow to be dynamically adjusted based on turbine rotational frequency. The electronic controller continuously monitors frequency and modifies pump displacement to maintain operation above stall conditions, transforming a static pump system into a dynamic one that adapts to varying wind conditions.
Solution Approach 2:
An electronic controller with frequency sensing capability provides real-time feedback on turbine rotational frequency. When frequency drops below a predetermined threshold, the controller automatically adjusts pump flow to increase frequency back above the stall threshold, creating a closed-loop control system that maintains reliable operation despite wind interruptions.
2Stress or pressure
If the pump flow is increased to maintain hydraulic pressure, then hydraulic power is sustained, but the turbine rotational frequency drops due to increased load
Solution Approach 1:
The variable displacement pump allows dynamic adjustment of flow based on system needs. When hydraulic pressure demands increase, the pump flow is increased, but the system simultaneously monitors frequency and reduces flow if frequency approaches stall conditions, creating a dynamic balance between pressure maintenance and frequency stability.
Solution Approach 2:
The system changes the operational parameters of the pump by adjusting displacement based on frequency feedback. When frequency drops, the pump displacement is reduced to decrease load on the turbine, allowing frequency to recover while maintaining adequate hydraulic pressure through controlled adjustments.
3Reliability
If the electronic controller with frequency monitoring is implemented, then stall conditions are prevented, but the system complexity increases
Solution Approach 1:
A frequency sensing circuit provides automatic feedback to the electronic controller, eliminating the need for complex manual monitoring systems. The controller compares frequency against predetermined thresholds and automatically adjusts pump flow, replacing complex human intervention with a simple automated feedback loop that enhances reliability without requiring operator training.
Solution Approach 2:
The control system is designed to be self-regulating, automatically detecting frequency drops and adjusting pump flow without external intervention. The system monitors its own operational parameters and corrects deviations from safe operating conditions, reducing the need for additional complex control mechanisms or human oversight.
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 effectively maintains stable hydraulic pressure and prevents turbine frequency drops, ensuring continuous power and preventing stall conditions by adjusting the pump flow to match wind velocity changes, thus enhancing safety and reliability during emergency landings.
Implementation Method 1
The controller is in signal communication with the PMG and is powered in response to receiving the voltage signal output from the PMG
Implementation Method 2
the external airstream induces rotation of the RAT to continue providing hydraulic power to a load
Implementation Method 3
The flow of hydraulic fluid in the fluid circuit controls a fluid pressure of the aircraft
Data Source
AI summary
An aircraft hydraulic control system includes a pump system, a fluid circuit, and a controller. The pump system includes a hydraulic pump and a ram air turbine assembly. The fluid circuit delivers hydraulic fluid to the hydraulic pump and receives the hydraulic fluid output from the hydraulic pump. The controller is in signal communication with the hydraulic pump. The controller determines a rotational frequency of a ram air turbine included in the ram air turbine assembly, and controls the hydraulic pump so as to control the flow of hydraulic fluid in the fluid circuit. The flow of hydraulic fluid in the fluid circuit controls a fluid pressure of the aircraft.