Flight Control Logic for Pitot Fault Isolation in Normal Mode
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Solution Overview
Problem
Flight control systems face challenges in accurately detecting common mode pneumatic events, such as pitot tube blockages, which can lead to inaccurate airspeed calculations and unnecessary mode switches, due to the immediate reliance on secondary sensors without isolating the source of error.
Innovation Solution
A flight control system that determines a rate of change in measured dynamic pressure and estimated angle of attack, comparing these values to threshold levels to identify a common mode pneumatic event, allowing for a transition to extended normal mode operation before switching to secondary modes, thereby isolating the source of error and reducing false alarms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the flight control system immediately switches to secondary sensors when a pitot tube fault is detected, then the system ensures continuous operation, but it causes unnecessary mode switches and spurious alarms due to false fault detection
Solution Approach 1:
The system performs preliminary validation by checking the rate of change of dynamic pressure and angle of attack before declaring a fault. This preliminary action prevents false detections by ensuring that fault conditions are confirmed through multiple correlated parameters rather than relying on a single sensor reading, thereby maintaining measurement precision while ensuring continuous operation
Solution Approach 2:
The system uses feedback from multiple sources (dynamic pressure rate of change, angle of attack rate of change, and pitot tube readings) to continuously monitor system state. This multi-layered feedback mechanism allows the system to distinguish between actual faults and normal operational variations, improving fault detection accuracy without compromising continuous operation
2Measurement precision
If the flight control system uses multiple sensors and complex validation logic, then the system improves fault detection accuracy, but it increases device complexity and processing requirements
Solution Approach 1:
The validation logic is segmented into distinct, modular checks: dynamic pressure rate of change validation, angle of attack rate of change validation, and fault declaration logic. This segmentation allows the complex validation process to be implemented as separate, manageable functions that can be independently tested and maintained, reducing overall system complexity while maintaining high fault detection accuracy
Solution Approach 2:
The system monitors changes in physical parameters (rate of change of dynamic pressure, rate of change of angle of attack) rather than absolute values. This parameter transformation simplifies the validation logic by converting complex multi-variable analysis into straightforward rate-of-change comparisons, improving fault detection accuracy without proportionally increasing system complexity
Data Source
AI summary
A flight control system for an aircraft is disclosed, where the flight control system detects a first common mode pneumatic event. The flight control system includes one or more processors and a memory coupled to the processors. The memory stores data comprising a database and program code that, when executed by the one or more processors, causes the flight control system to receive as input a measured dynamic pressure and an estimated angle of attack. The flight control system is further caused to determine a rate of change of the measured dynamic pressure and compare the rate of change of the measured dynamic pressure with a dynamic pressure threshold value. The flight control system is further caused to determine a rate of change of the estimated angle of attack and compare the rate of change of the estimated angle of attack with a threshold angle of attack.