Aircraft RTA Flight Control Using Independent Cruise and Descent Speeds
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Solution Overview
Problem
Conventional Required Time of Arrival (RTA) functions for aircraft fail to independently modify cruise and descent speeds effectively, often resulting in flight speed values close to limits, making it difficult to achieve the RTA constraint and leading to inefficient fuel use, especially when relying on Cost Index-coupled Mach and calibrated airspeed combinations.
Innovation Solution
A method and system that calculate and independently modify cruise and descent speeds by generating a curve of speed combinations to ensure the aircraft meets the RTA constraint at a target waypoint, avoiding speed limits and optimizing for additional flight parameters, such as fuel efficiency, by considering both Mach and calibrated airspeed as independent variables.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional RTA functions iterate over Cost Index to find trajectories, then a single variable search is performed, but the resulting cruise Mach and descent CAS combinations are coupled and often very close to aircraft speed limits
Solution Approach 1:
The patent segments the speed control into two independent components: cruise Mach number and descent CAS. Instead of searching through a single Cost Index variable that couples both speeds, the system independently optimizes each speed parameter. This segmentation allows the cruise speed and descent speed to be adjusted separately, avoiding the constraint where both speeds are tightly coupled and pushed to their limits simultaneously.
Solution Approach 2:
The patent transitions from a one-dimensional search (iterating over Cost Index) to a two-dimensional search space (independent cruise Mach and descent CAS parameters). By adding this additional dimension of independence, the system can explore a broader range of speed combinations that satisfy the RTA constraint without being forced into corner solutions where both speeds are at their limits.
2Loss of time
If cruise speed and descent speed are set close to aircraft speed limits to meet RTA, then time constraint is satisfied, but fuel efficiency deteriorates and speed margins are reduced
Solution Approach 1:
By segmenting the speed control into independent cruise Mach and descent CAS parameters, the system can optimize each phase separately for fuel efficiency rather than forcing both phases to operate at maximum speeds. This allows for more balanced speed selections that reduce overall fuel consumption while still meeting the time constraint.
Solution Approach 2:
The patent changes the optimization parameters from a single Cost Index to two independent parameters (cruise Mach and descent CAS). This parameter change enables the system to find speed combinations that optimize fuel efficiency while satisfying the RTA constraint, rather than being constrained to CI-coupled combinations that prioritize speed over fuel economy.
3Device complexity
If Cost Index-coupled Mach/CAS combinations are used, then initial trajectory prediction is simplified, but the resulting speed combinations may not be the most fuel-efficient and may require frequent speed adjustments
Solution Approach 1:
The patent segments the trajectory optimization into independent cruise and descent speed calculations. Instead of relying on the simplified but restrictive Cost Index coupling, the system independently determines optimal cruise Mach and descent CAS values. This segmentation maintains computational tractability while enabling fuel-efficient speed selections that reduce the need for frequent adjustments.
4Adaptability or versatility
If intermediate waypoints are introduced to break the reference trajectory, then speed pairs can be calculated for each segment, but a single speed profile complying with RTA and avoiding speed limits cannot be provided
Solution Approach 1:
The patent transitions from segmenting the trajectory into multiple pieces (intermediate waypoints) to segmenting the speed parameters into two independent dimensions (cruise Mach and descent CAS). This dimensional change allows the system to provide a single consistent speed profile that satisfies the RTA constraint and avoids speed limits, rather than creating discontinuous speed adjustments at intermediate waypoints.
Data Source
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AI summary
The disclosure relates to a method of controlling a flight of an aircraft subjected to a single required time of arrival constraint at a target waypoint ahead and also subjected to an additional flight criterion. The control of the flight is carried out by adapting the flight speed of the aircraft to a Mach speed and descent speed combination where the Mach speed and the descent speed are calculated independently from each other. It also relates to an aircraft navigation system for implementing the method. The method of controlling the flight of the aircraft is carried out during the cruise phase of the flight while the target waypoint lies in the descent phase of the flight.