Aircraft Landing Gear Bogie Movement Detection
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Solution Overview
Problem
Existing aircraft landing gear systems face challenges in reliably detecting weight on wheels during landing, particularly due to delays in shock absorber compression and wheel spin-up on contaminated runways, and are prone to failure when the pitch trimmer malfunctions or when all wheels touch down simultaneously.
Innovation Solution
The implementation of a landing gear assembly with a shock absorber strut, a bogie, and a link assembly connected by a movement detector that can detect relative movement between the link assembly and the bogie, regardless of initial positions, allowing for weight detection through compression and trail angle changes, even in the event of pitch trimmer failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If shock absorber compression is used to detect weight on wheels, then detection can be achieved, but detection is delayed due to breakout load requirements and pitch trimmer malfunction
Solution Approach 1:
The detection system is segmented into multiple independent detection mechanisms: shock absorber compression detection, wheel spin-up detection, and bogie movement detection. Each mechanism operates independently to detect weight on wheels, eliminating the single point of failure and delay associated with relying solely on shock absorber compression.
Solution Approach 2:
The system performs preliminary detection using wheel spin-up sensors and bogie movement sensors before shock absorber compression occurs. This allows weight on wheels to be detected earlier in the landing process, before the breakout load threshold is reached, reducing detection delay.
2Ease of operation
If pitch trimmer is used to position bogie for detection, then trail angle optimization is achieved, but system fails when pitch trimmer malfunctions
Solution Approach 1:
The detection system uses local quality changes in the bogie's movement characteristics to detect weight on wheels. By monitoring the bogie's movement relative to the shock absorber strut regardless of its absolute position, the system can detect weight on wheels even when the pitch trimmer fails to maintain the optimal trail angle.
Solution Approach 2:
The bogie's movement relative to the shock absorber strut serves as an intermediary indicator of weight on wheels. Instead of directly measuring wheel contact, the system uses the bogie's movement as a mediator that reflects the transition from flight to ground mode, providing reliable detection independent of pitch trimmer functionality.
3Reliability
If wheel spin-up detection is used, then weight on wheels can be detected, but detection is delayed on contaminated runways
Solution Approach 1:
The system merges multiple detection methods into a unified weight on wheels detection system. By combining shock absorber compression detection, wheel spin-up detection, and bogie movement detection, the system ensures that weight on wheels can be detected through at least one reliable mechanism even when contaminated runways delay wheel spin-up.
4Reliability
If breakout load threshold is set high enough to avoid false detection, then false positives are reduced, but detection is delayed for low sink rate landings
Solution Approach 1:
The detection system uses dynamic thresholds and multiple detection criteria rather than a fixed breakout load threshold. By monitoring the rate of change of bogie movement and combining multiple detection signals, the system can distinguish between normal flight maneuvers and actual weight on wheels events, avoiding false positives while enabling early detection of low sink rate landings.
Data Source
AI summary
An aircraft landing gear assembly (112) including a shock absorber strut (114), a bogie (120), a link assembly (124), and a movement detector (132). The shock absorber strut includes an upper and a lower telescoping parts (118, 116), the upper part being connectable to the airframe of an aircraft and the lower part being connected to the bogie such that the bogie may adopt different pitch angles. The link assembly extends between the upper and lower telescoping parts, such that relative movement between the upper and lower telescoping parts causes relative movement between parts of the link assembly. The movement detector is arranged to detect movement of the link assembly relative to the bogie. The movement detector detects movement by sensing a change in linear displacement of, or angle between, one or more members.