APU Inlet Door Control via Feedback Failure Detection
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Solution Overview
Problem
Existing systems for auxiliary power units (APUs) fail to determine the position of the inlet door accurately, leading to potential power unavailability during emergency in-flight starts and impacting aircraft availability.
Innovation Solution
A method and system that output control signals to alternate positions of the inlet door based on feedback signal failures, allowing the APU to operate in a degraded mode by commanding the door to a secondary position if primary feedback is unavailable, with a processing unit and memory to manage these commands and detect feedback failures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the APU inlet door position feedback is monitored strictly and the APU is prevented from starting when position cannot be determined, then system safety is improved, but APU power availability during emergency in-flight starts deteriorates
Solution Approach 1:
The system performs preliminary actions by commanding the inlet door to open to alternative positions when feedback signal failure is detected. The control system proactively switches to alternative door positions (first alternative position or second alternative position) before the APU start is blocked, ensuring power availability can be maintained during emergency in-flight starts even when primary feedback is unavailable
Solution Approach 2:
The system prepares compensatory measures in advance by establishing alternative door positions and feedback detection mechanisms. When the primary inlet door position feedback fails, the system has pre-established alternative positions ready to be commanded, cushioning against the potential loss of APU power availability during critical emergency situations
2Productivity
If the APU inlet door is commanded to alternate positions when feedback failure is detected, then APU power availability is improved, but system complexity increases
Solution Approach 1:
The control system segments the inlet door position control into multiple distinct positions: a normal operating position and at least two alternative positions. This segmentation allows the system to switch between discrete positions based on feedback signal status, managing complexity through clear position definitions rather than continuous control
Solution Approach 2:
The system dynamically adjusts the inlet door position based on real-time feedback signal status. The control system transitions from a static single-position command to a dynamic multi-position command structure, selecting appropriate positions (normal, first alternative, or second alternative) based on detected feedback failures, thereby maintaining APU power availability adaptively
3Reliability
If the inlet door position feedback signal is monitored for failures, then reliability is improved, but detection difficulty increases
Solution Approach 1:
The control system implements a feedback monitoring mechanism that continuously receives inlet door position feedback signals and detects failures. The system compares expected feedback with actual received feedback, identifying when feedback signals do not correspond to commanded positions or fall outside valid ranges, thereby maintaining reliability through active feedback verification
Solution Approach 2:
The system applies preliminary anti-action by detecting feedback signal failures before they compromise APU operation. The control system monitors feedback signals for inconsistencies with commanded positions and takes corrective action by commanding alternative door positions before the feedback failure can prevent APU start or operation
Data Source
AI summary
A system and method for controlling a position of an inlet door of an auxiliary power unit are provided. A first control signal comprising instructions for opening the inlet door to a selected one of at least a first position and a second position is output. A possible failure in a feedback signal associated with the selected one of the at least first position and second position is detected and a second control signal comprising instructions for opening the inlet door to the other one of the at least first position and second position is then output.