Soft-Mounted Tail Rotor Actuator for Tailboom Buffet Attenuation
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Solution Overview
Problem
Aircraft tailbooms experience significant vibration due to turbulent airflow, particularly in rotorcraft, leading to passenger discomfort and anxiety, with previous solutions either failing to effectively mitigate these vibrations or resulting in excessive weight and shift of the center of gravity.
Innovation Solution
The use of a soft-mounted tail rotor actuator with a flexible elastic member, tuned to match the tailboom's natural frequency, to attenuate lateral 'ringing' by 'notching' the excitation frequency and preventing harmonic force transmission, utilizing existing rotorcraft components like the tail rotor disk and elastomer materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional vibration absorption devices are used, then vibration mitigation is achieved, but excessive weight is added and center of gravity shifts too far aft
Solution Approach 1:
The patent applies mechanical vibration principles by tuning the tail rotor actuator's natural frequency to match the tailboom's lateral-bending or torsional natural frequency (ωTB). This creates a resonance condition where the actuator's vibratory motion generates aerodynamic forces that counteract the tailboom vibrations, achieving vibration mitigation without adding traditional heavy absorption devices
Solution Approach 2:
The patent converts the tail rotor actuator, which is already part of the aircraft system, into a vibration cancellation device by soft-mounting it and tuning its natural frequency. The actuator's intended function for pitch control is supplemented with a secondary function of vibration mitigation, transforming an existing component into a beneficial vibration counteracting system without adding separate heavy absorption devices
2Stability of the object's composition
If airflow entrainment devices are used, then airflow attachment is improved, but they fail to effectively mitigate tailboom vibrations
Solution Approach 1:
The patent uses mechanical vibration by tuning the tail rotor actuator's natural frequency to match the tailboom's natural frequency, creating a resonance condition that generates counteracting aerodynamic forces. This vibratory approach directly addresses tailboom vibrations rather than merely managing airflow attachment
Solution Approach 2:
The patent introduces the tail rotor actuator as an intermediary element between the tail rotor disk and the tailboom. By soft-mounting the actuator and tuning its frequency, it serves as a mediator that generates aerodynamic forces to counteract tailboom vibrations, providing a more effective solution than direct airflow management devices
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
Effectively cancels or attenuates the vibration at the tailboom's natural frequency, minimizing passenger discomfort while maintaining a balanced aircraft without excessive weight, using preexisting components and lightweight elastomer mounts.
Implementation Method 1
an elastic member that operably couples the mass to an airframe structure, the mass being attached to the tail rotor blade pitch change mechanism, wherein the elastic member deforms to allow the mass to vibrate at a predetermined frequency
Implementation Method 2
the mass being attached to the tail rotor blade pitch change mechanism, wherein the elastic member deforms to allow the mass to vibrate at a predetermined frequency sufficient to cancel the oscillatory response of the airframe structure
Implementation Method 3
When broadband oscillatory (unsteady) aerodynamic lateral loading occurs on the tail rotor disk, the spectrum of the excitation frequency is 'notched' such that the ωTB frequency is not transmitted through the tail rotor disk
Data Source
AI summary
An anti-tail buffet device leverages existing rotorcraft components to attenuate a tailboom's lateral “ringing” from air buffeting. Anti-buffet masses are tuned to the tailboom's lateral-bending or torsional natural frequency such that when lateral motion occurs, the response at this frequency is cancelled by the anti-buffet system, preventing this vibration from entering into the tailboom structure. Motion stops prevent over-travel. The mass of the tail rotor actuator is soft-mounted, such that its natural frequency is equal to the tailboom's lateral-bending or torsional natural frequency. When lateral loading occurs on the tail rotor disk, the lateral response at this frequency is attenuated by the soft-mounted tail rotor actuator, thereby preventing the vibration in the tailboom structure.