Removable APU Inlet Duct for Aircraft Skin Servicing
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Solution Overview
Problem
Existing methods for servicing aircraft auxiliary power units require removal of the aircraft skin to access components, which is inconvenient and disrupts the aircraft's structural integrity.
Innovation Solution
An inlet duct is designed with a seal that can be seated on the APU housing flange without a fixed connection, allowing it to be removed from the aircraft skin while keeping the skin in place, providing access to the APU for servicing without disassembling the aircraft.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the aircraft skin is removed to service APU components, then access to LRUs is improved, but structural integrity and maintenance complexity are worsened
Solution Approach 1:
The inlet duct is separated from the aircraft skin structure, allowing it to be removed independently. The duct includes a first flange that interfaces with the skin and a second flange that connects to the APU, creating modular segments that can be serviced without removing the entire skin assembly.
Solution Approach 2:
The inlet duct is extracted as a removable component from the fixed aircraft skin structure. By making the duct removable rather than integral, the design allows service personnel to access APU components through the opening in the skin without removing the skin itself, thereby maintaining structural integrity while improving accessibility.
2Stability of the object's composition
If the inlet duct is fixed to the aircraft skin, then structural integrity is improved, but ease of servicing APU is worsened
Solution Approach 1:
The inlet duct system is divided into separable components: a first flange that remains attached to the aircraft skin and a second flange that connects to the APU housing. This segmentation allows the duct to be detached for APU servicing while leaving the skin structure intact and stable.
Solution Approach 2:
The inlet duct transitions from a fixed, static connection to a dynamic, removable connection. The duct can be in an installed position during normal operation maintaining structural integrity, and then removed when APU servicing is required, providing adaptability between operational and maintenance states.
3Ease of repair
If the inlet duct is made removable from the skin, then ease of servicing is improved, but connection reliability is worsened
Solution Approach 1:
The seal is integrated with the second flange of the inlet duct, combining the sealing function with the connection structure. This ensures that when the duct is connected to the APU housing flange, a reliable seal is formed to prevent air leakage, maintaining connection reliability while allowing removable installation.
Solution Approach 2:
The seal acts as an intermediary element between the inlet duct flange and the APU housing flange. This intermediary component ensures proper sealing and connection reliability while allowing the duct to be removed and reinstalled during servicing operations.
Data Source
Figure 1~6D
Figure 2~3
Figure 4~5
AI summary
An aircraft auxiliary power unit assembly includes an aircraft skin (22) providing a cavity (11). The aircraft skin (22) is secured to a structure (13) in an assembled condition and provides an opening (60). An auxiliary power unit (10) is arranged within the cavity (11) and secured to the structure (13). The aircraft skin (22) substantially covers the auxiliary power unit (10) in the assembled condition. An inlet duct (18) is removably secured within the opening and is selectively connected to the auxiliary power unit between installed and service positions. The installed and service positions are with the aircraft skin (22) in the assembled condition. A method of servicing the auxiliary power unit includes removing the auxiliary power unit inlet duct (18) from the opening (50) in the aircraft skin (22). The auxiliary power unit (10) that is arranged within the cavity (11) of the aircraft skin (22) is exposed. A portion of the auxiliary power unit (22) is serviced through the opening (50).