RNP Approach Design Using Vertical Error Budget Obstacle Clearance
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Solution Overview
Problem
Current navigational procedures, such as TERPS and PANS-OPS, are not sufficient for providing safe and efficient aircraft approaches in obstacle-rich environments, particularly during low visibility conditions, as they do not guarantee clearance to the decision altitude and can lead to increased accident risks during non-precision approaches.
Innovation Solution
The method involves designing an approach for a selected runway by gathering obstacle data, calculating an obstacle clearance surface using a vertical error budget approach, and adjusting the decision altitude to ensure safe clearance, incorporating advanced navigation systems like GPS and RNP to provide precise guidance and safety buffers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional TERPS obstacle identification surfaces are used to guide aircraft approaches, then obstacle clearance is provided through empirical safety buffers, but the surfaces may not provide sufficient clearance to allow guidance all the way down to decision altitude in obstacle-rich environments
Solution Approach 1:
The patent changes the fundamental parameters of obstacle clearance surface design by transitioning from empirical TERPS surfaces to mathematically calculated surfaces based on actual aircraft performance parameters (climb gradients, thrust, weight, configuration). This allows the surface to accurately reflect the aircraft's ability to clear obstacles during missed approach, enabling guidance all the way to decision altitude while maintaining safety.
Solution Approach 2:
The patent replaces the empirical/mechanical TERPS surface methodology with a computational/mathematical system that uses aircraft performance data and physics-based calculations to generate obstacle clearance surfaces. This substitution enables more precise and flexible surface generation that adapts to specific aircraft characteristics and environmental conditions.
2Reliability
If non-precision approaches with minimum descent altitude are used instead of precision approaches with decision altitude, then obstacle clearance is maintained above minimum descent altitude, but the flight crew must execute circling procedures that present undue risk during low visibility
Solution Approach 1:
The patent performs preliminary calculation of the obstacle clearance surface and determines the safe decision altitude before the approach is executed. By pre-calculating the missed approach climb performance and obstacle clearance requirements, the system establishes a decision altitude that guarantees safe obstacle clearance, eliminating the need for risky post-decision maneuvers during low visibility conditions.
3Ease of operation
If ground-based radio navigation systems are used to provide position information, then navigational procedures can be developed for poor visibility conditions, but the systems are not particularly accurate and provide less certainty of aircraft position the farther the aircraft is from the transmitter
Solution Approach 1:
The patent introduces an intermediary computational layer that processes raw navigation data and calculates precise obstacle clearance surfaces. This intermediary system bridges the gap between imperfect ground-based navigation signals and the requirement for precise obstacle avoidance, using mathematical modeling to compensate for navigation system limitations and provide accurate safety margins.
4Reliability
If traditional empirical TERPS criteria are used for approach design, then safety is deemed adequate through large numbers of safe operations, but the criteria have not kept up with improved navigation system capabilities that permit tighter containments
Solution Approach 1:
The patent makes the obstacle clearance surface generation dynamic and adaptive to specific aircraft performance characteristics rather than using static empirical criteria. The system dynamically calculates surfaces based on real-time or aircraft-specific performance data (thrust, weight, configuration, climb gradients), allowing the safety margins to optimize with improved navigation capabilities while maintaining the reliability foundation of proven safety methodologies.
Data Source
AI summary
A method (200) is disclosed for designing an RNP approach for an aircraft at a particular runway (90). The method includes selecting a runway (201), gathering obstacle data for the obstacle evaluation area (202), selecting a VEB method and terms (204), laying out a preliminary approach, inducing a missed approach segment (206), calculating a preliminary obstacle clearance surface (208), calculating a momentary descent segment using a physical model of the aircraft (210), adjusting the obstacle clearance surface so that no obstacles intersect the surface (212), and optionally optimizing the approach by departing from the operator's standard procedures (214). Preferably, the obstacle clearance surface is adjusted so that it just touches an obstacle, without any object intersecting the surface, thereby providing an optimal decision altitude.