Aircraft Landing Gear Axle Locking Device
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Solution Overview
Problem
Existing locking devices for steerable axles in aircraft landing gear require the steering mechanism to align the axle before locking, which can be problematic due to bogie beam deflection under static load, leading to potential failure in locking engagement.
Innovation Solution
The use of barrier arms with a two-bar over-centre linkage and actuator system that can lock the axle in a desired orientation without requiring the steering mechanism to align it first, with arm abutments engaging the axle abutments to maintain the orientation and prevent pivoting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a locking actuator is provided between the bogie beam and the steerable axle to lock the axle in a predetermined orientation, then the axle can be locked in the desired orientation, but the locking may fail to engage when the bogie beam bends under static load causing the axle to pivot away from the correct orientation
Solution Approach 1:
The locking mechanism is divided into two independent functional components: a steering actuator that orients the axle and a separate locking device with barrier arms that physically prevents pivoting. This segmentation allows each component to perform its specific function without being compromised by bogie beam deflection, as the locking arms can engage the axle regardless of its precise orientation.
Solution Approach 2:
The barrier arms act as intermediary elements between the locking actuator and the axle. These arms extend across the path of the axle and physically block pivoting motion, serving as a mechanical mediator that ensures locking engagement even when the steering mechanism cannot precisely position the axle due to bogie beam flexibility.
2Ease of operation
If the steering actuator is positioned between the bogie beam and the steerable axle to control orientation, then the axle can be steered, but deflection of the bogie beam causes the axle to pivot and may prevent the lock from re-engaging
Solution Approach 1:
The system separates steering control from locking function. The steering actuator handles orientation control while the independent locking device with barrier arms handles physical restraint. This segmentation ensures that steering operations are not compromised by locking mechanisms and vice versa, maintaining ease of operation while ensuring reliable re-engagement.
Solution Approach 2:
The locking barrier arms are positioned in advance to block the pivoting path of the axle before any unwanted movement can occur. By having the locking mechanism ready and positioned, the system prevents the axle from moving into positions where re-engagement would fail, rather than attempting to correct movement after it occurs.
3Measurement precision
If an internally locking actuator is powered to a centred position defined by a control system, then the actuator can be positioned centrally, but tolerances may cause the lock position to not exactly coincide with the driven position preventing engagement
Solution Approach 1:
The locking function is extracted from the steering actuator and implemented by a separate locking device with barrier arms. This extraction eliminates the dependency between precise actuator positioning and locking engagement, as the barrier arms provide a mechanical locking interface that does not require sub-millimeter positioning accuracy from the steering mechanism.
Solution Approach 2:
The locking mechanism changes the operational parameters from precision-dependent (actuator position) to tolerance-insensitive (mechanical barrier engagement). The barrier arms engage the axle through a mechanical interface that accommodates manufacturing tolerances and positioning variations, transforming the locking problem from one requiring high precision to one that is robust against imprecision.
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
A landing gear (10), including an elongate axle (16a) pivotally (18) connected to a bogie beam (14), the landing gear further including a locking device (30) for locking the axle at a substantially fixed orientation with respect to the bogie beam, the locking device including first and second barrier arms (32c, 34c) that are movable between a first configuration, in which they define a barrier so as to maintain the maintain the axle in the substantially fixed orientation with respect to the bogie beam, and a second configuration, in which the axle may pivot about the bogie beam.