Composite Interface Frame for Rotary Wing Aircraft Tail Boom
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Solution Overview
Problem
Existing rotary wing aircraft designs face issues with corrosion, fatigue, and maintenance difficulties due to the use of metal interface frames between the fuselage tail boom and tail cone, which are prone to tension forces and complex assembly processes.
Innovation Solution
A single interface frame with a connecting sleeve and tubular region made of composite material, directly attached to both the fuselage tail boom and tail cone, eliminating bended flanges and using shear stress connections, which simplifies assembly and reduces weight and corrosion risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal interface frames with bended flanges are used to join the tail cone and fuselage tail boom, then the structural connection is achieved, but corrosion problems occur due to contact between parts made of different materials
Solution Approach 1:
The interface frame is manufactured from the same composite material (fiber-reinforced plastic) as the tail cone and fuselage tail boom, ensuring homogeneous material composition throughout the assembly. This eliminates galvanic corrosion between dissimilar materials while maintaining structural integrity through unified material properties.
Solution Approach 2:
The invention employs fiber-reinforced plastic composite materials for the interface frame, replacing traditional metal materials. This composite construction provides corrosion resistance while maintaining the required mechanical strength and stiffness for joining the tail cone and fuselage tail boom.
2Reliability
If bended connecting flanges are used in the interface frame, then the tail cone and fuselage tail boom are joined, but the stretch bolts are loaded with tension forces leading to fatigue issues
Solution Approach 1:
Instead of using bended flanges that create tension loads on bolts, the invention inverts the connection approach by using a straight tubular body with shear-loaded fasteners. The fasteners pass through the tubular body and are secured with nuts, transferring loads through shear rather than tension, which significantly reduces fatigue on the fastening elements.
3Ease of operation
If the connecting flanges are located at the interior of the rear of the rotary wing aircraft, then the interface frame structure is compact, but inspection and maintenance works become difficult
Solution Approach 1:
The invention extracts the fastening elements (fasteners and nuts) from the interior location and positions them accessible from the exterior of the aircraft. This allows inspection and maintenance personnel to access and service the connection elements without disassembling internal structures, significantly improving maintainability while keeping the overall structure compact.
4Ease of manufacture
If a single interface frame is used to join the tail cone and fuselage tail boom, then the assembly process is simplified, but the structural integrity must be maintained without bended flanges
Solution Approach 1:
The invention merges the functions of multiple components (tubular body, fasteners, nuts) into a single integrated interface frame assembly. This unified structure simplifies the assembly process by reducing the number of separate parts to be installed while maintaining structural integrity through the composite material construction and shear-loaded fastening system.
Data Source
AI summary
A rotary wing aircraft comprising a fuselage tail boom, a tail cone and an interface frame, the interface frame in turn having a connecting structure directly attached to the tail cone by means of a tail cone mechanical connection and a connecting sleeve fitting axially the fuselage tail boom, the connecting sleeve and the fuselage tail boom being directly attached by means of a one boom mechanical connection; the interface frame thereby joining the fuselage tail boom and the tail cone.