Rotorcraft Tail Assembly Transition Structure Stress Reduction
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Solution Overview
Problem
The interface zone between the tail fin and tail boom in rotorcrafts experiences high stress concentrations, especially when a ducted tail rotor is present, leading to weight and maintenance challenges due to the need for a larger tail fin cross-section and complex power transmission shaft arrangements.
Innovation Solution
A transition structure with a higher transverse dimension is introduced between the tail boom and tail fin, featuring a cut-out elevation step and reinforcement ribs to reduce stress concentrations, allowing a smoother transition and optimizing the corner radius, while the power transmission shaft penetrates through a forwardly offset opening, reducing stress and maintaining accessibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the tail fin cross-section is increased to accommodate a ducted tail rotor, then the tail rotor can be housed within the tail fin, but stress concentrations increase at the interface zone between tail fin and tail boom
Solution Approach 1:
The invention offsets the power transmission shaft penetration point forward along the longitudinal axis, away from the critical interface zone between tail fin and tail boom. This dimensional relocation in the longitudinal direction eliminates the stress concentration problem while still allowing power transmission to the ducted tail rotor housed in the tail fin.
Solution Approach 2:
The invention introduces a transition structure with a cut-out elevation step that acts as an intermediary element. This transition structure mediates between the tail boom and tail fin, providing a smooth geometric transition that reduces stress concentrations while accommodating the forward-offset power transmission shaft penetration.
2Power
If the power transmission shaft penetrates through the tail fin at the interface zone, then power can be transmitted to the tail rotor, but maintenance accessibility becomes difficult
Solution Approach 1:
The invention relocates the power transmission shaft penetration point forward along the longitudinal axis to a position away from the tail fin interface zone. This dimensional change in position allows power to still be transmitted to the tail rotor while significantly improving maintenance accessibility, as the shaft can now be accessed from the front of the aircraft rather than from the difficult-to-reach interface zone.
3Loss of energy
If the tail boom cross-section is minimized to reduce aerodynamic interaction, then aerodynamic efficiency improves, but the interface zone with the tail fin experiences higher stress concentrations
Solution Approach 1:
The invention offsets the power transmission shaft penetration forward along the longitudinal axis, relocating it away from the critical interface zone. This allows the tail boom to maintain its minimized cross-section for aerodynamic efficiency while the stress concentration problem is resolved by moving the penetration point to a different longitudinal position where it does not interfere with the tail fin attachment.
Data Source
AI summary
A tail assembly for a rotorcraft. The tail assembly is manufactured to include at least one transition structure provided in the tail assembly. The transition structure is longitudinally arranged between a longitudinal median boom portion and a tail fin. A power transmission shaft of the rotorcraft extends at least partly externally above a longitudinal median boom portion of the tail assembly. The transition structure includes at an entering region a cut-out elevation step, where is made a passing through opening for the power transmission shaft.