Landing Gear Load Feedback for Aircraft De-Rotation Control
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Solution Overview
Problem
During the landing phase of a vehicle, the movement of pitch control surfaces to maintain pitch angle and control de-rotation rate can apply large downward forces to the main landing gears, potentially causing damage due to excessive loads, especially when open-loop control systems fail to account for environmental disturbances.
Innovation Solution
A closed-loop feedback control system that adjusts the deflection of pitch control surfaces based on real-time load measurements from the main landing gear, setting updated trailing-edge-up limits to mitigate excessive loads and adapt to environmental uncertainties such as crosswinds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the pitch control surface trailing edge is moved up to maintain pitch angle and control de-rotation rate, then the pitch angle control is improved, but large downward forces are applied to the main landing gear struts causing excessive loads
Solution Approach 1:
The patent implements a closed-loop feedback control system that uses load sensors to measure the actual load on the landing gear struts and feeds this information back to the flight control computer. The computer dynamically adjusts the trailing-edge-up limit of the pitch control surface based on the measured load, thereby maintaining pitch angle control while preventing excessive downward forces on the landing gear.
Solution Approach 2:
The system dynamically adjusts the trailing-edge-up limit parameter based on real-time load conditions rather than using a fixed limit. This dynamic adjustment allows the pitch control surface deflection to adapt to changing environmental conditions and landing gear load states, optimizing the balance between pitch control effectiveness and landing gear load reduction.
2Device complexity
If a fixed trailing-edge-up limit is used to control de-rotation rate, then the de-rotation control is simplified, but the system cannot adapt to environmental disturbances such as crosswinds
Solution Approach 1:
The patent employs feedback control by continuously monitoring the load on the landing gear struts through load sensors and adjusting the pitch control surface trailing-edge-up limit accordingly. This feedback mechanism enables the system to adapt to environmental disturbances like crosswinds while maintaining relatively simple control logic in the flight control computer.
3Reliability
If the pitch control surface is commanded to move upward to prevent nose gear slap-down, then the nose gear protection is improved, but the load on the main landing gear struts increases significantly
Solution Approach 1:
The system uses load feedback from the main landing gear struts to dynamically adjust the pitch control surface trailing-edge-up limit. This feedback control prevents excessive loads on the main gear struts while still providing sufficient upward pitch moment to protect the nose gear from slap-down, thereby protecting both landing gear systems within their respective load capacities.
Solution Approach 2:
The patent changes the trailing-edge-up limit parameter dynamically based on the measured load condition. By adjusting this critical parameter in real-time, the system optimizes the balance between protecting the nose gear from impact and preventing excessive loads on the main landing gear struts, ensuring both systems operate within safe load margins.
Data Source
AI summary
An example method includes receiving pitch angle sensor information indicative of a pitch angle of a vehicle, wherein the vehicle comprises a main landing gear having a strut and a pitch control surface configured to control the pitch angle of the vehicle; determining a trailing-edge-up limit for upward movement of the pitch control surface to control a de-rotation rate of the vehicle as the vehicle lands; receiving load sensor information indicative of a load on the strut of the main landing gear of the vehicle; based on the pitch angle of the vehicle being below a pitch angle threshold, determining an updated trailing-edge-up limit based on the load on the strut; and controlling the pitch control surface based on the updated trailing-edge-up limit.