Pre-hung Air Inlet Door Assembly for Aircraft
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Solution Overview
Problem
Current air inlet door systems for gas turbine engines, such as auxiliary power units, are time-consuming and expensive to install and repair, with close tolerance interfaces being difficult to achieve, leading to premature failures and limited component interchangeability.
Innovation Solution
A pre-hung air inlet door assembly comprising a door box frame, actuation system, and pivot shafts, where the air inlet door is fully assembled before installation, using shop fixtures for precise positioning and NC machined components to reduce binding and trimming needs, allowing for easier access and repair without removing the engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If current air inlet door designs are used with traditional assembly practices, then the system can convey air from outside the aircraft to the APU compressor, but assembly time is excessive and component interchangeability is prevented
Solution Approach 1:
The air inlet door system is divided into modular components: the door assembly, the door box, and the actuation system. Each module can be independently manufactured, tested, and replaced. The door assembly includes the door panel, hinges, and seals as an integrated unit that can be swapped without affecting other components, enabling rapid interchangeability while maintaining system functionality.
Solution Approach 2:
The door assembly is pre-assembled and pre-adjusted to specifications before installation in the aircraft. Tolerances are controlled during manufacturing rather than during field installation. This preliminary preparation eliminates the need for time-consuming on-site adjustments and ensures that components can be interchanged without requiring re-rigging or special procedures.
2Manufacturing precision
If close tolerance interfaces are required between aircraft skin, fixed structure, and air inlet door, then proper alignment can be achieved, but assembly time increases excessively
Solution Approach 1:
The door box serves as an intermediary structure between the aircraft skin and the air inlet door. It provides a pre-formed interface with controlled tolerances that mediates the connection between the fixed aircraft structure and the moving door. This intermediary component absorbs tolerance variations and ensures proper alignment without requiring excessive time for field adjustments.
Solution Approach 2:
Traditional mechanical alignment methods involving shimming, hand trimming, and rigging are replaced with precision-machined interfaces and self-aligning features. The door assembly incorporates precision bearings and pivot points that automatically align during installation, eliminating the need for time-consuming mechanical adjustment procedures while maintaining close tolerance requirements.
3Productivity
If traditional air inlet door assembly methods are used, then the system can be installed, but binding and misalignment of rotating components cause premature failures
Solution Approach 1:
The door assembly incorporates dynamic alignment features that accommodate operational variations. The hinge pins and pivot shafts are designed with floating mounting features that allow automatic adjustment during door operation. This dynamic capability ensures proper alignment throughout the door's range of motion, preventing binding and premature bearing failures while maintaining rapid installation capability.
Solution Approach 2:
The design incorporates adjustable parameters in the actuation system and hinge mounting locations. These parameters can be precisely controlled during manufacturing to optimize alignment and eliminate binding. The use of precision-machined surfaces and controlled clearance tolerances ensures consistent performance across all installed units, reducing premature failures while enabling efficient installation.
4Ease of repair
If the engine must be removed to access air inlet mechanism components for repair, then complete access can be achieved, but maintenance time and cost increase
Solution Approach 1:
The air inlet door assembly is extracted as a separate, independently accessible module from the engine system. The door box and actuation system are positioned and configured to allow removal and installation without disturbing the engine. This extraction of the inlet mechanism from the engine assembly enables maintenance personnel to service door components without the time-consuming process of removing the entire engine.
Data Source
AI summary
A pre-hung air inlet door assembly comprises an inlet door, a door box frame, and an actuation system. The door box frame is fastened to the support structure of an aircraft. The inlet door is operationally connected to the actuation system. The entire pre-hung air inlet door assembly can be pre-assembled for quick installation into an aircraft. Pre-assembly eliminates trimming operations and rigging and misalignment issues. The pivot shafts and bearing housings of the pre-hung air inlet door assembly can be accessed from outside the aircraft when repairs and/or replacement components are needed.