AOA Vertical Control Function for Aircraft AFCS
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Solution Overview
Problem
Current AFCS modes, such as Vertical Speed and FLCH, either require constant pilot input to avoid stalling or result in erratic climbs due to changing air data parameters, leading to safety and comfort issues during aircraft altitude changes.
Innovation Solution
An AOA-based vertical control function for AFCS that maintains a constant angle of attack by adjusting thrust, pitch angle, and angle of incidence, allowing the aircraft to climb or descend safely without stalling or oscillating.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If Vertical Speed Mode is used to provide constant climb rate, then climb performance is improved, but aircraft safety deteriorates due to risk of stalling when pilot does not adjust climb rate
Solution Approach 1:
The AFCS system automatically adjusts the climb rate based on real-time AOA measurements and aircraft performance data, eliminating the need for constant pilot input. The system serves itself by monitoring AOA and autonomously modifying vertical speed to maintain safe operating margins, thus preventing stalls while maintaining climb performance.
Solution Approach 2:
The system continuously monitors AOA, aircraft altitude, speed, and performance parameters, then feeds this information back to automatically adjust the climb rate. This closed-loop feedback mechanism ensures the aircraft maintains optimal AOA throughout the climb, preventing stall conditions while maximizing climb efficiency.
2Reliability
If FLCH Mode is used to maintain constant air speed, then aircraft safety is improved by eliminating stall risk, but flight smoothness deteriorates due to erratic oscillations on pitch axis
Solution Approach 1:
Instead of maintaining constant air speed, the system changes the controlled parameter to constant AOA. By controlling the angle of attack rather than speed, the system achieves both safety (preventing stalls) and smoothness (eliminating pitch oscillations), as AOA directly correlates with lift generation and flight stability.
Solution Approach 2:
The system dynamically adjusts thrust and pitch angle to maintain constant AOA despite changing air data parameters. This dynamic control approach allows the aircraft to adapt to varying temperatures and air densities at different altitudes without creating the erratic oscillations seen in FLCH mode, providing both safety and ride comfort.
3Reliability
If FLCH Mode maintains constant air speed through changing temperatures, then safety is improved, but device complexity increases due to erratic oscillations requiring continuous adjustment
Solution Approach 1:
The patent changes the fundamental control parameter from air speed to angle of attack. This parameter change simplifies the control logic because AOA directly relates to lift and stall prevention, eliminating the need for complex oscillation dampening algorithms required in speed-based modes. The system becomes simpler while maintaining safety.
Data Source
AI summary
The present invention is directed to an AOA (angle of attack) vertical control function for an AFCS (automated flight control system) for an aircraft. The AOA vertical control function of the AFCS causes the aircraft to climb or descend while maintaining the aircraft at a constant AOA. The AFCS may maintain the constant AOA despite changing air data parameters by increasing or decreasing the thrust of the aircraft, the pitch angle of the aircraft, or the angle of incidence of the aircraft wing. By utilizing AOA, an aircraft can be safely directed to automatically climb or descend to any altitude the aircraft is capable of reaching without the risk of stall (unlike Vertical Speed Mode) or the irritation of the FLCH (Flight Level Change) Mode erratic climb.