Fuselage APU Installation Using an Unpressurized Rear Compartment
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Solution Overview
Problem
Aircraft retrofits requiring additional auxiliary power units (APUs) face challenges due to heat and exhaust issues, which complicate ventilation and increase aerodynamic drag and design complexity when housed internally or externally.
Innovation Solution
Mounting the APU in a compartment of the fuselage that maintains external pressure, using existing connections and structures to integrate the APU without additional openings or design changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the APU is housed internally in a pressurized cabin environment, then the APU is protected from external conditions, but heat and exhaust ventilation becomes complex and requires additional weight and cost for pressure box modifications
Solution Approach 1:
The fuselage is divided into a pressurized cabin section and an unpressurized equipment section. The APU is housed in the unpressurized equipment section at the rear of the fuselage, which is not part of the pressurized cabin. This segmentation allows the APU to be protected from external conditions while avoiding the complexity of pressurizing the entire fuselage, eliminating the need for complex ventilation systems and heavy pressure box modifications.
2Device complexity
If the APU is mounted externally on the aircraft, then ventilation is simplified, but aerodynamic drag increases and design complexity increases
Solution Approach 1:
The APU is merged with the existing aircraft fuselage structure by housing it in the unpressurized equipment section. This integration allows the APU to benefit from simplified ventilation (no pressurization required) while avoiding external mounting, thereby eliminating increased aerodynamic drag and the associated design complexity.
3Reliability
If modifications are made to the airframe for a dedicated pressure box, then the APU can be housed internally, but weight and cost penalties increase
Solution Approach 1:
The unpressurized equipment section at the rear of the fuselage is repurposed to house the APU. This section was already designed to be unpressurized for other equipment, so no additional modifications or heavy pressure box structures are required. The existing structural design serves multiple functions, avoiding both weight and cost penalties.
Data Source
AI summary
An aircraft is disclosed, including a fuselage having a compartment configured to house refueling apparatus. An auxiliary power unit is mounted in the compartment.