Aircraft Tail Spar Spring for Vibration Reduction
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Solution Overview
Problem
Rotorcrafts face challenges in reducing oscillatory loads and vibrations, particularly due to the sensitivity of tail vertical surfaces, which require intrusive design changes or significant weight adjustments to achieve dynamic tuning, often resulting in high costs and parasitic weight.
Innovation Solution
The implementation of a forward attachment system that provides axial compliance to the vertical tail, allowing for dynamic tuning by decoupling tail vibration modes from fuselage bending modes, using a combination of an inner and outer member with elastomeric pads to restrict rotation within a specific range, thereby reducing oscillatory loads and vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If intrusive design changes or significant weight adjustments are made to achieve dynamic tuning, then vibration reduction is improved, but device complexity and parasitic weight increase
Solution Approach 1:
The attachment system is divided into inner and outer members with separate functional zones. The inner member provides axial compliance while the outer member provides rotational restraint, allowing independent optimization of each function without requiring intrusive changes to the entire tail structure.
Solution Approach 2:
Elastomeric pads are introduced as intermediary elements between the inner and outer members. These pads provide the necessary compliance and damping to reduce vibrations while maintaining structural strength, avoiding the need for significant weight adjustments or complex design changes.
2Adaptability or versatility
If axial compliance is provided to the vertical tail, then dynamic tuning capability is improved, but rotational stability may worsen
Solution Approach 1:
The attachment system provides different mechanical properties in different directions: axial compliance is provided along the longitudinal axis while rotational restraint is maintained in the vertical and horizontal planes. This directional differentiation allows dynamic tuning without compromising rotational stability.
Solution Approach 2:
The system transitions from a static, rigid attachment to a dynamic, compliant attachment that allows controlled axial motion. The elastomeric pads provide progressive stiffness, becoming more rigid under high loads while allowing compliance during normal operation, thus maintaining stability across different flight conditions.
3Object-affected harmful factors
If elastomeric pads are used to provide compliance, then vibration reduction is improved, but structural strength may worsen
Solution Approach 1:
The attachment system combines rigid metallic members with compliant elastomeric pads in a composite structure. The metal members provide structural strength and load-bearing capacity while the elastomeric pads provide vibration damping and compliance, achieving both strength and vibration reduction simultaneously.
Solution Approach 2:
The elastomeric pads are positioned to provide cushioning before oscillatory loads can transmit through the rigid structure. This beforehand cushioning absorbs and dampens vibrations at the source, protecting the overall structure from resonant stresses while maintaining strength.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution effectively reduces global oscillatory loads and vibrations while maintaining structural strength, allowing for critical tail fin load reactions and axial motion, thus improving aircraft dynamic response without the need for intrusive design changes or excessive weight addition.
Implementation Method 1
an inner and outer member with elastomeric pads to restrict rotation within a specific range
Data Source
AI summary
According to one embodiment, an empennage attachment system features an aft attachment mechanism and a forward attachment system. The aft attachment mechanism is configured to be coupled to a tail section of a body of an aircraft and to an empennage proximate to an aft spar of the empennage. The aft attachment mechanism defines a pitch axis such that the aft attachment mechanism allows the empennage to rotate about the pitch axis. The forward attachment system is configured to be coupled to the tail section of the body and to the empennage proximate to a forward spar of the empennage. The forward attachment system is configured to restrict rotation of the empennage about the pitch axis to an allowable range of motion.