EGPWS Envelope Modification for RNP Terrain Clearance
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Solution Overview
Problem
Current Enhanced Ground Proximity Warning Systems (EGPWS) generate nuisance warnings due to their larger warning envelopes intersecting with obstacles, which can lead to pilot desensitization and non-optimum approach paths, as they are not aligned with the more precise Required Navigation Procedure (RNP) envelopes.
Innovation Solution
The system determines the aircraft's location and RNP status, accesses RNP information, and modifies the ground proximity warning envelope to match the RNP envelope, ensuring that only obstacles impinging on the modified envelope trigger warnings, thereby reducing nuisance warnings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the EGPWS uses a larger warning envelope to ensure terrain clearance, then safety is improved, but nuisance warnings increase and pilot responsiveness decreases
Solution Approach 1:
The system applies different envelope criteria in different operational contexts. When RNP is active, a smaller RNP-based envelope is used; when RNP is not active, the larger EGPWS envelope is used. This local differentiation allows the system to optimize for precision when available while maintaining safety margins when RNP is not applicable.
Solution Approach 2:
The warning envelope dynamically adapts based on the operational mode. The system switches between two envelope definitions: the traditional EGPWS envelope and the RNP-based envelope. This dynamic adjustment allows the system to match the precision of navigation being used, reducing nuisance warnings when high-precision RNP is active while maintaining safety when using less precise navigation.
2Reliability
If the EGPWS envelope is larger to account for errors, then safety buffer is improved, but the envelope intersects with more obstacles causing false alarms
Solution Approach 1:
The system changes the envelope parameters based on the navigation system being used. When RNP is active, the envelope parameters are tightened to match RNP precision; when RNP is not active, the envelope parameters are relaxed to provide larger safety buffers. This parameter adaptation reduces false alarms while maintaining appropriate safety margins.
Solution Approach 2:
The system uses feedback from the navigation system's precision capabilities to adjust the envelope size. By monitoring whether RNP is active and what level of precision is achieved, the system dynamically adjusts the envelope dimensions. This feedback mechanism ensures the envelope is neither too conservative nor too permissive, reducing false alarms while maintaining safety.
3Productivity
If RNP envelopes are smaller and more precise, then navigation efficiency is improved, but terrain clearance warnings may be missed if EGPWS is not aligned
Solution Approach 1:
The system merges the EGPWS terrain monitoring function with RNP precision navigation by integrating the RNP envelope definition into the EGPWS. This integration allows the terrain warning system to use the same precision-based envelope as the navigation system, ensuring that terrain clearance monitoring is aligned with navigation efficiency goals without sacrificing either.
Data Source
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AI summary
Systems and methods for monitoring Required Navigational Procedures (RNP) and reducing nuisance Enhanced Ground Proximity Warning System (EGPWS) warnings including a processor 42 and a memory 40 with RNP information. The processor 42 accesses the RNP data and instructions from the memory 40- When the processor 42 determines that an aircraft 10 is in RNP space 32, the processor 42 projects an RNP envelope 32 and modifies a warning envelope 28 of an EGPWS 22 to coincide with the RNP envelope 32 if the EGPWS warning envelope 28 extends farther than the RNP envelope 32.