Aircraft Brake Shutoff Valve Test for Dormant Fault Detection
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Solution Overview
Problem
Aircraft brake systems face a dormant failure condition where a faulty shutoff valve can remain operational, leading to unintended braking during takeoff due to a failure in the safety interlock mechanism, which existing technologies fail to detect effectively.
Innovation Solution
A method and system that test the brake shutoff valve by commanding it to a disarmed state during benign conditions, measuring fluid pressure and wheel deceleration to determine if braking occurs, thereby identifying any malfunction and reporting it for necessary repairs or precautions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the shutoff valve is set in the disarmed position to prevent unintentional braking during takeoff, then safety is improved, but the system cannot detect dormant failure conditions where the valve fails to inhibit fluid pressure
Solution Approach 1:
The system performs a preliminary test of the shutoff valve during benign flight phases (after takeoff or before landing) by commanding the valve to the disarmed position and attempting to activate the brake. This preliminary action detects dormant failures before they could cause unsafe conditions during critical operations.
Solution Approach 2:
The system implements feedback by monitoring whether brake activation occurs when the shutoff valve is commanded to the disarmed position. If unexpected brake activation is detected, the system generates a warning indication to alert the pilot of a potential shutoff valve failure.
2Measurement precision
If a test is performed to detect dormant faults in the shutoff valve, then detection capability is improved, but the test can only be performed during benign states limiting operational flexibility
Solution Approach 1:
The system dynamically adjusts its operation based on flight conditions. The shutoff valve test is automatically enabled or disabled based on whether the aircraft is in a benign state (after takeoff or before landing), allowing the system to adapt to operational requirements while maintaining detection capability when safe to do so.
3Measurement precision
If the servo valve is commanded to apply fluid pressure during testing, then the test can detect shutoff valve failures, but unintended braking may occur if the shutoff valve is faulty
Solution Approach 1:
The system prepares for potential harmful effects by selecting test windows during benign flight phases where unintended braking would have minimal impact. This beforehand cushioning approach ensures that even if the test causes unintended braking due to a faulty shutoff valve, the consequences are minimized.
Data Source
AI summary
A system, apparatus and method of verifying operation of a vehicle fluid brake system shutoff valve is provided, wherein the shutoff valve is adapted to enable or inhibit the transmission of fluid pressure to at least one brake solenoid valve that controls operation of at least one brake actuator so as to effect wheel braking. In verifying operation of the system, the shutoff valve is commanded to inhibit the transmission of fluid pressure to the at least one brake solenoid valve, and the at least one brake solenoid valve is commanded to apply fluid pressure to the at least one brake actuator. An operational status of the shutoff valve is determined based on the absence or presence of wheel braking.