RAT Auto-Deploy via DC Bus Voltage Monitoring
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Solution Overview
Problem
Conventional power distribution systems in aerospace applications, particularly AC essential busses, rely on manual deployment of ram air turbines (RAT) when AC power is available but not available to DC buses, or when contactor statuses are unreliable, leading to potential loss of DC system loads and battery drain.
Innovation Solution
A system with multiple AC and DC busses, transformer rectifier units, and voltage sensors connected to a RAT automatic deployment controller that automatically deploys the RAT based on voltage thresholds and aircraft air mode, eliminating the need for human intervention by using AC essential bus tie contactors and essential contactors to ensure power distribution and RAT deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If manual deployment of RAT is used when AC power is available but not available to DC buses, then the system can respond to power distribution failures, but it relies on airmanship and flight crew action which may be delayed or missed
Solution Approach 1:
The system automatically monitors DC bus voltage and triggers RAT deployment without requiring manual intervention by flight crew. The automatic deployment controller continuously checks voltage levels and autonomously activates the RAT when thresholds are breached, making the system self-monitoring and self-acting.
Solution Approach 2:
The system implements continuous feedback monitoring of DC bus voltage through voltage sensors that report to the automatic deployment controller. This closed-loop feedback mechanism enables real-time detection of power distribution failures and automatic response based on predefined voltage thresholds.
2Reliability
If conventional RAT auto-deploy based on generator line contactor status is used, then the system can detect contactor failures, but it does not account for scenarios where AC power is available but cannot power DC buses or when contactor statuses are unreliable
Solution Approach 1:
Instead of directly monitoring contactor status, the system uses DC bus voltage as an intermediary indicator of power distribution health. This voltage-based monitoring approach indirectly detects various failure modes including contactor failures, TRU failures, and power source failures, providing a more comprehensive monitoring mechanism.
Solution Approach 2:
The voltage-based monitoring system serves multiple detection functions: it identifies contactor failures, TRU failures, power source failures, and abnormal power distribution conditions. A single monitoring mechanism handles diverse failure scenarios that would otherwise require multiple specialized detection systems.
3Reliability
If automatic deployment based on voltage thresholds is implemented, then the system can respond to actual power loss conditions, but it requires multiple voltage sensors and control logic increasing system complexity
Solution Approach 1:
The system uses voltage sensors on representative DC buses (such as bus 112 and bus 118) as copies or proxies for monitoring the overall power distribution system health. By monitoring key representative points, the system infers the status of the entire DC power network without requiring sensors on every single bus.
Solution Approach 2:
The automatic deployment controller combines multiple input signals (voltage sensor readings from various DC buses, air mode detection, contactor status) into a single unified control decision. This merging of multiple monitoring inputs into one centralized control logic simplifies the overall system architecture compared to having independent control systems for each monitoring parameter.
Data Source
AI summary
A system includes a first AC bus configured to supply power from a first AC power source. A second AC bus is configured to supply power from a second AC power source. A first transformer rectifier unit (TRU) connects a first DC bus to the first AC bus through a first TRU contactor (TRUC). A second TRU connects a second DC bus to the second AC bus through a second TRUC. A first voltage sensor is connected to sense voltage of the first DC bus. A second voltage sensor is connected to sense voltage of the second DC bus. A ram air turbine (RAT) automatic deployment controller is operatively connected to the first voltage sensor and to the second voltage sensor to automatically deploy a RAT based on the combined status of the first voltage sensor and the second voltage sensor.