Flight Management System Vertical Descent Trajectory Rejoining
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Solution Overview
Problem
During the descent phase in high-traffic airspaces, conventional flight management systems struggle to efficiently rejoin the vertical descent trajectory, leading to excessive deviations and increased fuel consumption, which can result in delayed approach phases and increased pilot workload.
Innovation Solution
A method utilizing a flight management system to calculate and manage vertical deviations, activating an optimized catch-up mode with specific target speeds and thrust settings to minimize fuel consumption and passenger discomfort, while reducing pilot workload. This involves calculating the vertical deviation between the aircraft and the descent trajectory, comparing it to a predetermined threshold, and activating an optimized mode for catching up on the vertical descent trajectory at minimum thrust with target rejoining speeds adjusted based on the aircraft's L/D ratio and operating speeds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the FMS operates in conventional vertical descent trajectory catch-up mode, then the aircraft can rejoin the descent trajectory, but the aircraft requires wide speed ranges and long distances to catch up, resulting in excessive deviations and increased fuel consumption
Solution Approach 1:
The patent changes the speed parameters from conventional wide ranges (descent speed ±20 knots) to optimized narrow ranges based on L/D ratio speed and VMO. This parameter optimization enables the aircraft to maintain better energy efficiency while improving descent trajectory rejoining performance through calculated target speeds
Solution Approach 2:
The patent performs preliminary calculations of optimal target speeds (VCRP and VCRD) based on aircraft performance characteristics before executing the descent catch-up maneuver. This preliminary action allows the aircraft to plan an energy-efficient rejoining path that minimizes fuel consumption while maintaining productivity
2Loss of time
If the aircraft is constrained to follow a level trajectory for a long time, then the vertical deviation from the descent trajectory increases, but the aircraft must wait for ATC clearance, increasing loss of time
Solution Approach 1:
The patent implements a feedback mechanism that continuously monitors the vertical deviation (VDEV) and compares it against a threshold (SVDEV). When the threshold is exceeded, the system automatically activates optimized catch-up mode, enabling the aircraft to respond dynamically to deviation conditions and reduce rejoining time without excessive deviation accumulation
3Ease of operation
If the FMS uses conventional target rejoining speeds (descent speed ±20 knots), then the aircraft can maintain simple speed management, but the aircraft generates wide excursions above the descent trajectory, requiring manual air brake intervention
Solution Approach 1:
The patent enables the FMS to automatically calculate and adjust optimal target speeds (VCRP and VCRD) based on aircraft performance parameters without requiring pilot intervention. The system serves itself by autonomously optimizing speed management, maintaining both simplicity and reliability while eliminating the need for manual air brake usage
4Loss of energy
If the aircraft accelerates to catch up on the descent flight plan, then the vertical deviation is reduced, but the air brakes generate vibrations that are uncomfortable for passengers and increase energy consumption
Solution Approach 1:
The patent changes the acceleration parameters by using optimized target speeds (VCRD = VMO - V2) instead of conventional aggressive acceleration to descent speed +20 knots. This parameter optimization reduces energy consumption and minimizes vibrations, thereby improving passenger comfort while maintaining effective descent trajectory rejoining
Data Source
AI summary
A method is provided for assisting in rejoining a vertical descent trajectory that an aircraft is assumed to have to follow, using a flight management system FMS embedded onboard the aircraft, and includes the following steps: calculation of a vertical deviation VDEV, in the vertical plane, between the aircraft and the vertical descent trajectory, and comparison between the vertical deviation VDEV and a predetermined deviation threshold SVDEV; when the vertical deviation VDEV reaches the deviation threshold SVDEV, a step during which the activation of an optimized mode for catching up on the vertical descent trajectory is authorized; if the optimized mode for catching up on the vertical descent trajectory is activated, piloting of the aircraft by the flight management system FMS in optimized catch-up mode, that is to say at minimum thrust with a target rejoining speed in level VCRP and a target rejoining speed in downward trajectory, the target rejoining speed in level VCRP being equal to the maximum L/D ratio speed of the aircraft uprated by a first value V1 of between 5 and 15 knots, and the target rejoining speed in downward trajectory VCRD being equal to the maximum operating speed VMO with which the aircraft is allowed to fly downrated by a second value V2 of between 3 and 10 knots, a knot being equal to 0.514 ms−1.