TAWS Premature Descent Envelope Expansion for False Glideslope Alerts
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Solution Overview
Problem
Aircraft pilots face challenges in safely landing due to incorrect interpretation of glideslope signals from instrument landing systems (ILS), leading to potential premature descent issues, as false signals can result in flying too low without generating alerts within the standard premature descent envelope.
Innovation Solution
A method and system that expand the premature descent envelope by comparing glideslope and localizer deviation data to acceptable bands, using a terrain awareness and warning system (TAWS) to increase minimum clearance altitudes when the aircraft is following vertical and horizontal guidance, thereby generating an alert if the aircraft flies below the expanded altitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the standard premature descent envelope is used, then the system maintains normal operation without false alerts, but the system fails to detect aircraft flying too low due to false glideslope signals
Solution Approach 1:
The system dynamically changes the parameter of the premature descent envelope (minimum clearance altitude) based on the adherence to glideslope and localizer signals. When signals indicate proper following of guidance, the envelope is expanded to higher altitudes, thereby detecting aircraft that are flying too low due to false signals while maintaining normal operation during legitimate approaches.
2Reliability
If the premature descent envelope is expanded to detect false glideslope signals, then detection accuracy improves, but false alerts may be generated during normal approaches
Solution Approach 1:
The system applies different envelope characteristics to different flight conditions. The premature descent envelope is selectively expanded only in the specific condition where the aircraft is adhering to glideslope and localizer signals, while maintaining the standard envelope for all other conditions. This localized adaptation prevents false alerts during normal approaches while improving detection accuracy when following false signals.
Solution Approach 2:
The premature descent envelope is made dynamic rather than static. The system continuously monitors adherence to glideslope and localizer signals and adjusts the envelope's minimum clearance altitude accordingly. This dynamic adjustment allows the envelope to adapt to changing flight conditions, expanding when needed to detect false signals and contracting during normal approaches to avoid false alerts.
3Reliability
If the system monitors glideslope and localizer deviation data continuously, then detection capability improves, but system complexity increases
Solution Approach 1:
The system uses the existing glideslope and localizer deviation data, which are already being processed for primary flight guidance, to perform the additional function of verifying signal authenticity and adjusting the premature descent envelope. By making the existing data processing multi-functional, the system avoids the need for separate monitoring systems, thereby improving detection capability without proportionally increasing system complexity.
Data Source
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AI summary
A method for managing a premature descent envelope during descent of an aircraft is provided. The method receives glideslope deviation data by an instrument landing system (ILS) onboard the aircraft; compares, by the ILS, the glideslope deviation data to an acceptable band of glideslope deviation values; and when the glideslope deviation data is within the acceptable band, expands, by a terrain awareness and warning system (TAWS), the premature descent envelope to produce an increased premature descent envelope for the aircraft.