Aircraft Tail Plane Flutter Mitigation via Compressive Stiffeners
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Solution Overview
Problem
Aircraft tail planes are prone to aeroelastic flutter, a dangerous phenomenon that can lead to dynamic instability and structural failure, especially at high speeds, due to the coupling of natural modes of vibration in flapping and twisting, which existing damping methods struggle to effectively mitigate without adding weight or requiring structural modifications.
Innovation Solution
The implementation of stiffener means that exert compressive stress on the stabilizer portions of the tail plane, specifically at the root interface with the tail boom, to increase stiffness by at least 20% in twisting, shifting the frequency of natural modes of vibration and preventing destructive coupling between flapping and twisting modes, thus reducing the risk of flutter without needing to redesign existing tail planes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing damping methods are used to mitigate flutter, then the risk of flutter is reduced, but the weight of the tail plane increases or structural modifications are required
Solution Approach 1:
The invention changes the physical parameters of the stabilizer portion by filling the clearance with a material of predetermined stiffness, thereby modifying the natural frequency of twisting vibration without adding significant weight. This parameter change shifts the frequency away from the flapping mode, preventing flutter coupling.
Solution Approach 2:
The filler material acts as an intermediary element between the stabilizer portion and the tail boom peripheral wall. This intermediary provides the necessary stiffness to shift vibration frequencies while maintaining the existing structural configuration, avoiding direct structural modifications.
2Reliability
If existing damping methods are used to mitigate flutter, then the risk of flutter is reduced, but structural modifications to the tail plane are required
Solution Approach 1:
The invention achieves flutter mitigation by changing the stiffness parameter of the stabilizer portion through filler material, rather than requiring structural modifications such as adding braces or changing the airfoil structure. This maintains the existing device complexity while improving reliability.
Solution Approach 2:
The filler material serves as a non-intrusive intermediary that fits within the existing clearance space, requiring no structural modifications to the tail plane or tail boom. The filler is simply inserted into the available gap, maintaining device simplicity.
3Reliability
If the natural frequency of twisting vibration is close to the natural frequency of flapping vibration, then the tail plane is prone to flutter, but increasing stiffness shifts the frequency away from resonance
Solution Approach 1:
The invention carefully adjusts the stiffness parameter of the stabilizer portion by selecting appropriate filler materials with predetermined stiffness values. This controlled parameter change shifts the natural frequency of twisting vibration away from the flapping frequency, reducing flutter risk without excessive stiffening.
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 increases the stability margin of the tail plane, reducing the risk of flutter by shifting critical frequencies and maintaining stability over time and varying temperatures, while being easily maintainable and applicable to existing aircraft, including rotorcraft and helicopters.
Implementation Method 1
stiffener means exerting predetermined compressive stress on the stabilizer portion
Implementation Method 2
the phenomenon of aeroelastic flutter, commonly referred to simply as 'flutter'
Data Source
AI summary
An aircraft (1) provided with a tail boom (4) including a tail plane (100) provided with an airfoil surface (5), the airfoil surface (5) being provided with at least one stabilizer portion (11, 12) extending laterally outside the tail boom (4) and with a central portion (13) extending inside the tail boom (4), said stabilizer portion (11, 12) being implanted in an orifice (6, 7) of the tail boom (4) that is defined by a peripheral wall (6′, 7′), clearance (21, 22) existing between said stabilizer portion (11, 12) and said peripheral wall (6, 7). The aircraft includes combating means (30) for combating the flutter phenomenon, which means are provided with stiffener means (31, 32) exerting predetermined compressive stress on said stabilizer portion (11, 12), said stiffener means (31, 32) being arranged at the root of the stabilizer portion (11, 12).