Aircraft Bogie Axle Mounting Using Cryogenic Shrink Fit
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Solution Overview
Problem
The conventional method of replacing axles in aircraft bogies requires disassembly and reassembly of the bogie from the landing gear, which is complex and costly due to the need for grounding the aircraft.
Innovation Solution
A method and system for mounting an axle in a bore of a bogie using a mobile bearing structure with alignment means and a tank filled with liquid nitrogen to cool and contract the axle, allowing insertion in a horizontal position without disassembly, utilizing a reference mark and laser beam for alignment, and a hoist for precise alignment and insertion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the axle is inserted horizontally into the bore while the landing gear is in gear-down position, then the maintenance time and cost are reduced, but the alignment precision between axle and bore becomes more difficult to achieve
Solution Approach 1:
The patent changes the orientation parameter of the axle from vertical to horizontal, and changes the thermal state parameter by cooling the axle with liquid nitrogen to enable thermal contraction, allowing horizontal insertion into the bore while maintaining proper fit and alignment
Solution Approach 2:
The patent introduces liquid nitrogen as an intermediary substance to cool and contract the axle, and uses a mobile bearing structure as an intermediary device to facilitate horizontal alignment and insertion, resolving the conflict between maintenance efficiency and alignment precision
2Ease of operation
If the axle is cooled with liquid nitrogen to facilitate insertion, then the insertion ease is improved, but the device complexity increases due to the need for cooling equipment
Solution Approach 1:
The patent uses liquid nitrogen's self-cooling property to contract the axle automatically when introduced, eliminating the need for complex active cooling systems. The mobile bearing structure also uses passive alignment mechanisms rather than active control systems
Solution Approach 2:
The patent exploits the phase transition of liquid nitrogen (from liquid to gas) and the associated thermal contraction effect on the axle to achieve easy insertion. The temperature change causes the axle material to contract, reducing friction and enabling smooth insertion into the bore
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Facilitates easy and cost-effective axle replacement directly on the aircraft without disassembly, reducing downtime and maintenance costs by simplifying the process and ensuring accurate alignment.
Implementation Method 1
Introducing the axle into the tank filled with liquid nitrogen allows cooling the axle to a temperature of approximately −200° C., which causes contraction of the axle which facilitates its insertion into the bore
Implementation Method 2
Once in the bore, the temperature of the axle rises to ambient temperature, which causes the axle to expand, leading to an increase in its outer diameter until it is automatically locked in place by its expansion in the bore at ambient temperature
Data Source
AI summary
A method and system for mounting an axle in a bore of a bogie mounted on a landing gear of an aircraft, the landing gear being in a gear-down position, the bore extending in a substantially horizontal direction referred to as the axle installation direction, between a first open end and a second open end are disclosed. The method includes a) supplying a mobile bearing structure (30) comprising means for moving the axle (12) which are able to move along a direction substantially parallel to the axle installation direction, b) installing the axle (12) on the means for moving the axle, c) aligning the axis (C) of the axle (12) with the axis (B) of the bore (14), and d) inserting the axle (12) into said bore (14) of the bogie (16) by moving the means for moving the axle (12) along the direction substantially parallel to the axle installation direction.