Serrated Roller Tray Fitting for No-Drill Fuselage Installation
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Solution Overview
Problem
The installation of fixed length roller tray segments in aircraft cargo handling systems is hindered by assembly tolerance accumulation at fuselage integration zones, requiring post-final assembly drilling into aircraft substructures, which leads to foreign object debris and cost issues.
Innovation Solution
A serrated fitting system that includes a serrated surface for engagement with a serrated plate attached to a pre-installed floor beam, allowing for no-drill installation of roller tray segments by using oversized pre-drilled holes and a fastener that bypasses the load path.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If post-final assembly drilling is performed to install roller tray attach fittings, then the roller tray segments can be securely attached to floor beams, but foreign object debris is generated and manufacturing costs increase
Solution Approach 1:
The serrated plates are pre-installed on the floor beams before final assembly, and the holes are pre-drilled at the correct positions. This preliminary action eliminates the need for post-assembly drilling, thereby preventing foreign object debris generation while maintaining secure attachment capability
Solution Approach 2:
The serrated fitting acts as an intermediary component that engages with the pre-installed serrated plate. This intermediary mechanism allows for tolerance accommodation through the serrated engagement surface while maintaining secure attachment without requiring post-assembly drilling
2Adaptability or versatility
If post-final assembly drilling is performed to accommodate assembly tolerances, then roller tray segments can be installed across fuselage integration zones, but manufacturing costs increase
Solution Approach 1:
The serrated plates are pre-installed on the floor beams before final assembly, with holes pre-drilled at positions that will accommodate the cumulative tolerances of fuselage integration zones. This eliminates the need for costly post-assembly drilling operations
Solution Approach 2:
The serrated surface geometry is designed to accommodate tolerance variations. The serrated engagement allows for positional adjustments within tolerance ranges, providing adaptability to assembly variations without requiring additional manufacturing operations
3Object-affected harmful factors
If pre-drilled holes with dimensions greater than fastener diameter are used, then no-drill installation is enabled and foreign object debris is reduced, but the fastener clearance increases
Solution Approach 1:
The holes are pre-drilled with oversized dimensions to accommodate both the fastener and the cumulative tolerances of fuselage integration zones. This preliminary drilling action eliminates the need for post-assembly drilling, preventing foreign object debris while providing sufficient clearance for tolerance accommodation
Solution Approach 2:
The hole dimension is intentionally made asymmetric relative to the fastener diameter, with the hole being larger than the fastener. This asymmetric dimensioning provides the necessary clearance for tolerance accommodation while maintaining secure fastener engagement
Data Source
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AI summary
A serrated fitting and method for installing fixed length roller tray segments spanning an aircraft fuselage integration zone. The serrated fitting includes a first surface for attachment to a fixed length roller tray segment. The serrated fitting also includes a serrated surface for engagement with a serrated plate attached to a floor beam of an aircraft. A fastener connects the serrated surface to the serrated plate and the floor beam through a pre-drilled hole in the floor beam. The pre-drilled hole is larger than the diameter of the fastener to accommodate accumulated tolerance between joined fuselage sections at a fuselage integration zone.