Patent Description:
The present invention relates in general to the field of dampers, and more particularly, to a novel damper assembly.

Without limiting the scope of the invention, its background is described in connection with aircraft dampers.

One such patent is <CIT> and entitled, "Dual frequency damper for an aircraft". Briefly, these inventors teach a dual frequency damper includes a liquid inertia vibration eliminator (LIVE) portion and a fluid damper portion. The LIVE portion and fluid damper portion are said to operate in series and function so that dual frequency damper is optimized in both stiffness and damping at multiple frequencies. LIVE portion acts as a frequency dependent switch to selectively cause low frequency oscillatory forces to be treated primarily by the high spring rate and high damping rate characteristics of the fluid damper portion, and also to select high frequency oscillatory forces to be primarily treated by the low spring rate and low damping rate characteristics of the LIVE unit portion.

One such patent application is <CIT>, and entitled "Rotating Shaft Damping With Electro-Rheological Fluid". Briefly, these applicants teach rotating shaft damping using an electro-rheological fluid. At least a portion of a circumferential surface area of a portion of a rotorcraft rotating shaft is surrounded with multiple hollow members, and each hollow member includes an electro-rheological fluid having a viscosity that changes based on an electric field applied to the electro-rheological fluid. The vibration of the rotorcraft rotating shaft is controlled by changing the viscosity of the electro-rheological fluid in response to the electric field applied to the electro-rheological fluid.

Yet another application is <CIT>, and is entitled "Method For Damping Rear Extension Arm Vibrations Of Rotorcraft And Rotorcraft With A Rear Extension Arm Vibration Damping Device". Briefly, these applicants are said to teach a method for damping vibrations in a tail boom of a rotary-wing aircraft includes the steps of detecting tail boom vibrations induced by external vibration excitation, and generating and introducing strains into the tail boom based on the detected tail boom vibrations. Next, strains are applied over a surface area and are out-of-phase with respect to the detected tail boom vibrations so as to damp the externally excited induced tail boom vibrations. In addition, a rotary-wing aircraft, includes a fuselage, a cockpit area integrated into the fuselage, a tail boom arranged on the fuselage and a tail boom vibration-damping device. The vibration-damping device includes at least one sensor element configured to detect tail boom vibrations induced by external vibration excitation and at least one actuator configured to generate and introduce strains into the tail boom that are out-of-phase with respect to the induced tail boom vibrations, the actuator being functionally coupled to the sensor element, engaging with a tail boom structure at one side of the tail boom, and forming a flat-surfaced bond with the tail boom.

<CIT> discloses a vibration damping apparatus which has a first looped rope member and a second looped rope member each having a loop portion formed of a rope member in a loop shape. The rope member is formed by twining a plurality of linear members. Further, the vibration damping apparatus has a first base member and a second base member disposed in an up-and-down of the first looped rope member. The first looped rope member is fixed to the first base member and the second base member with the loop portion standing up. The second looped rope member is fixed to an intersecting portion, in one of the first base member and the second base member, intersecting a fixing portion of the first looped rope member with the loop portion standing up.

The present invention includes an aircraft having a damper assembly and a tailboom as recited in claim <NUM>. The present invention further includes a method as recited in claim <NUM>. Some optional or preferred features are outlined in the dependent claims. In one embodiment, the present invention includes a damper assembly for an airframe comprising: a mass to damp the vibration of the airframe; one or more wire rope isolators having a first and a second portion, wherein the mass is attached to the one or more wire rope isolators and the mass is isolated from the airframe by the one or more wire rope isolators; and a first fastener and a second fastener, wherein the first fasteners attaches to the first portion of the wire rope isolator to the mass, and the second fastener attaches the second portion of the wire rope isolator to the airframe to dampen vibration of the airframe. In one aspect, the wire rope isolators are further defined as comprising a stiffness, compression/shear, compression/roll, and shape, wherein the stiffness, compression/shear, compression/roll, and shape of the wire rope is selected to provide frequency isolation of the mass in two or more frequencies. In another aspect, the first fastener or the second fastener is selected to attach the damper assembly to a rotorcraft or vertical take off and landing craft. In another aspect, the first and second portions of the one or more wire rope isolators are along a side of the one or more wire rope isolators, at the ends of the one or more wire rope isolators, at the end and/or along the side of the one or more wire rope isolators. In another aspect, the mass is connected by <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more wire rope isolators that are positioned on one or more sides of the mass. According to the invention, the mass is positioned at the end of a tail boom, along the length of a tail boom, or a combination thereof. In another aspect, the damper assembly is a passive damper assembly. In another aspect, the damper assembly further comprises a coating on the mass, the first or second fasteners, and/or the one or more wire rope isolators. In another aspect, the mass, the first or second fasteners, or the one or more wire rope isolators are selected from at least one of metal, composite, polymer, ceramic, alloys, or combinations of the same. In another aspect, the wire rope isolators are defined further as comprising one or more of fiber strands, fiber wires, polymer strands, polymer wires, lubricating oil, polymer, adhesive, filler, and/or a coating. In another aspect, the wire rope is selected from a size, shape, and strength of the wire rope in one or more dimensions based on at least one of: (<NUM>) a rope bending length l; (<NUM>) a diameter D of sheave and/or drum; (<NUM>) one or more simple bendings per working cycle w-sim; (<NUM>) one or more reverse bendings per working cycle w-rev; (<NUM>) a combined fluctuating tension and bending per working cycle w-com; (<NUM>) a relative fluctuating tensile force deltaS/S; or (<NUM>) a rope tensile force S. In another aspect, the vibration is adjusted in two or more frequencies based on the shape, size, compressive strength, rotational strength, or pull strength of the wire rope.

In another embodiment, the present invention includes a method for damping vibration of an airframe comprising: providing a mass to dampen the vibration of the airframe; selecting one or more wire rope isolators having a first and a second portion, wherein the mass is isolated from the airframe by the one or more wire rope isolators; and attaching the mass to the one or more wire rope isolators and the one or more wire rope isolators to an airframe, wherein one or more first fasteners attach the first portion of the one or more wire rope isolators to the mass, and one or more second fasteners attach the second portion of the one or more wire rope isolators to the airframe, wherein the mass dampens vibration of the airframe, wherein the mass is positioned at the end of the tail boom, along the length of the tail boom, or a combination thereof. In one aspect, the wire rope isolators are further defined as
comprising a stiffness, compression/shear, compression/roll, and shape, wherein the stiffness, compression/shear, compression/roll, and shape of the wire rope is selected to provide frequency isolation of the mass in two or more frequencies. In another aspect, the first fastener or the second fastener is selected to attach the damper assembly to a rotorcraft or vertical take off and landing craft. In another aspect, the first and second portions of the one or more wire rope isolators are along a side of the one or more wire rope isolators, at the ends of the one or more wire rope isolators, at the end and/or along the side of the one or more wire rope isolators. In another aspect, the mass is connected by <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or more wire rope isolators that are positioned on one or more sides of the mass. According to the invention,
the mass is positioned at the end of a tail boom, along the length of a tail boom, or a combination thereof. In another aspect, the damper assembly is a passive damper assembly. In another aspect, the method further comprises coating one or more of the mass, the first or second fasteners, or the one or more wire rope isolators. In another aspect, the mass, the first or second fasteners, or the one or more wire rope isolators are selected from at least one of metal, composite, polymer, ceramic, alloys, or combinations of the same. In another aspect, the wire rope isolators are defined further as comprising one or more of fiber strands, fiber wires, polymer strands, polymer wires, lubricating oil, polymer, adhesive, filler, and/or a coating. In another aspect, the wire rope is selected from a size, shape, and strength of the wire rope in one or more dimensions based on at least one of: (<NUM>) a rope bending length l; (<NUM>) a diameter D of sheave and/or drum; (<NUM>) one or more simple bendings per working cycle w-sim; (<NUM>) one or more reverse bendings per working cycle w-rev; (<NUM>) a combined fluctuating tension and bending per working cycle w-com; (<NUM>) a relative fluctuating tensile force deltaS/S; or (<NUM>) a rope tensile force S. In another aspect, the vibration is adjusted in two or more frequencies based on the shape, size, compressive strength, rotational strength, or pull strength of the wire rope.

For a more complete understanding of the features and advantages of the present invention, reference is now made to the detailed description of the invention along with the accompanying figures and in which:.

Illustrative embodiments of the system of the present application are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developer's specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure.

In the specification, reference may be made to the spatial relationships between various components and to the spatial orientation of various aspects of components as the devices are depicted in the attached drawings. However, as will be recognized by those skilled in the art after a complete reading of the present application, the devices, members, apparatuses, etc. described herein may be positioned in any desired orientation. Thus, the use of terms such as "above," "below," "upper," "lower," or other like terms to describe a spatial relationship between various components or to describe the spatial orientation of aspects of such components should be understood to describe a relative relationship between the components or a spatial orientation of aspects of such components, respectively, as the device described herein may be oriented in any desired direction.

The present disclosure is a passive vibration dampening device that is attached with wire ropes to the frame of a craft, such as an aircraft. Non-limiting examples of aircrafts include rotorcraft, such as helicopters and vertical take off and landing aircraft. Briefly, the moving mass is excited by a given source, typically the vibrational forcing from rotor blades, which in turn provides damping for a critical mode placed very near a known excitation frequency. This reduces the vibration levels at that frequency felt throughout the aircraft.

As used herein, the term "wire rope" refers to one or more ropes with strands of metal or steel wire laid or twisted into a shape around a core. The cross-sectional shape of the wires can be, for example, round, ovoid, trapezoidal, square, rectangular, triangular, or combinations thereof. The wire rope may also include a "core", which can be one of three types: (<NUM>) a fiber core, made up of synthetic or natural material (fiber cores are generally the most flexible and elastic, but are easily crushed and thus not suitable for heavy loads); (<NUM>) a wire strand core, is made up of one additional strand of wire, and is typically used for suspension; and (<NUM>) an independent wire rope core, which is the most durable in all types of environments, or combinations thereof. The one or more wires of the wire rope are typically made of non-alloy carbon steel although other suitable materials may be used such as steel, iron, stainless steel, chromium steel, galvanized steel, alloys, monel, and bronze materials. Wires may be made by suitable methods, such as the drawing process where the wire cross-section is reduced in stages, for example in multiple stages, e.g., from <NUM> to <NUM> diameter. Using a drawing process, the nominal strength of the wire may be increased.

The type and material of the wire rope can be selected to select different compression, tensile strength, flexure, or any parameter in three dimensions, including using different types of wire rope within a single wire rope assembly. Non-limiting examples of wire rope include those that are: (<NUM>) stranded ropes (aka running ropes) that are formed by bending over sheaves and cylinders and are stressed mainly by bending and secondly by tension; (<NUM>) stationary ropes or stay ropes (spiral ropes, e.g., full-locked), which carry tensile forces and are therefore mainly loaded by static and fluctuating tensile stresses; (<NUM>) track ropes (aka full locked ropes) generally do not take on the curvature of any rollers and under the roller force, a so-called free bending radius of the rope occurs, which radius increases (and the bending stresses decrease) with the tensile force and decreases with the roller force; and/or (<NUM>) wire rope slings (aka stranded ropes), which are slings that are stressed by tensile forces but first of all by bending stresses when bent over more or less sharp edges. In particular, one or more of the following factors can be varied to optimize the dampening effect caused by the wire rope, including: (<NUM>) working cycles up to rope discarding or breakage (mean or <NUM>% limit); (<NUM>) number of wire breaks (detection to need rope replacement); (<NUM>) rope safety factor (minimum breaking force Fmin / nominal rope tensile force S), which is the ability to resist extreme impact forces; (<NUM>) Donandt force (yielding tensile force for a given bending diameter ratio D/d), generally, the nominal rope tensile force S is smaller than the Donandt force SD1; and (<NUM>) rope diameter (maximum rope endurance for a given sheave diameter D and tensile rope force S).

<FIG> depicts an aircraft <NUM> in accordance with a preferred embodiment of the present application. In the exemplary embodiment, aircraft <NUM> is a helicopter having a fuselage <NUM> and a rotor system <NUM> carried thereon. A plurality of rotor blades <NUM> is operably associated with rotor system <NUM> for creating flight. The system of the present invention is
used in conjunction with an aircraft <NUM>. Although shown associated with a helicopter, it will be appreciated that the system of the present application could also be utilized with different types of rotary aircraft and vehicles.

For example, <FIG> illustrates a tiltrotor aircraft <NUM> that utilizes the system in accordance with the present application. Tiltrotor aircraft <NUM> includes rotor assemblies 202a and 202b that are carried by wings 204a and 204b, and are disposed at end portions 206a and 206b of wings 204a and 204b, respectively. Rotor assemblies 202a and 202b include nacelles 208a and 208b, which carry the engines and transmissions of tiltrotor aircraft <NUM>. Tilt rotor assemblies 202a and 202b move or rotate relative to wing members 204a and 204b between a helicopter or hover mode in which tilt rotor assemblies 202a and 202b are tilted upward, such that tiltrotor aircraft <NUM> flies like a conventional helicopter; and an airplane or cruise mode in which tilt rotor assemblies 202a and 202b are tilted forward, such that tiltrotor aircraft <NUM> flies like a conventional propeller driven aircraft.

<FIG> illustrates another tiltrotor aircraft <NUM> that utilizes the system in accordance with the present application. Tiltrotor aircraft <NUM> includes rotor assemblies 202a and 202b that are carried by wings 204a and 204b, and are disposed at end portions 206a and 206b of wings 204a and 204b, respectively. Rotor assemblies 202a and 202b include nacelles 208a and 208b, which include the engines and transmissions of tiltrotor aircraft <NUM>. In this embodiment, the engines are fixed to the wing and do not rotate, rather, only the pylons 210a and 210b with the rotor assemblies 202a and 202b rotates. Tilt rotor assemblies 202a and 202b move and rotate relative to wing members 204a and 204b and the nacelles 208a and 208b. The tilt rotor assemblies 202a and 202b do not move relative to the wing members 204a and 204b. Instead, during the transition between a helicopter or hover mode only the pylons 210a and 210b with the rotor assemblies 202a and 202b rotate to redirect the thrust from the rotor assemblies 202a and 202b. The rotorcraft <NUM> is still able to fly like a conventional helicopter; and an airplane or cruise mode in which on the rotors are tilted forward, such that tiltrotor aircraft <NUM> flies like a conventional propeller driven aircraft.

<FIG> shows a damper system <NUM> on a tail boom <NUM> of a rotorcraft and
<FIG> shows a close-up view of a tail section <NUM> at the end of the tail boom <NUM> showing one configuration of the wire rope damper assembly <NUM> of the present invention. In the close-up view, the damper assembly <NUM> is attached to the distal end <NUM> of the tail boom <NUM>, and includes a mass <NUM>, wire ropes 312a, 312b, first fasteners 314a, 314b, and second fasteners 316a, 316b. The mass <NUM> is attached to the wire ropes 312a, 312b via first fasteners 314a, 314b, and the wire ropes 312a, 312b are connected to the distal end <NUM> of the tail boom <NUM> via second fasteners 316a, 316b. Thus, the wire ropes 312a, 312b isolate the mass <NUM> from the distal end <NUM> of the tail boom <NUM>.

<FIG> shows a side view of the distal end <NUM> of the tail boom <NUM> and one configuration of the wire rope damper assembly <NUM> attached to the tail rotor gearbox support structure. In this side view, the damper assembly <NUM> is attached to the distal end <NUM> of the tail boom <NUM>, and includes a mass <NUM>, wire ropes 312a, 312b, first fasteners 314a, 314b, and second fasteners 316a, 316b. The mass <NUM> is attached to the wire ropes 312a, 312b via first fasteners 314a, 314b, and the wire ropes 312a, 312b are connected to the distal end <NUM> of the tail boom <NUM> via second fasteners 316a, 316b, all of which are attached by bolts <NUM>. Thus, the wire ropes 312a, 312b isolate the mass <NUM> from the distal end <NUM> of the tail boom <NUM>, and further include a plate <NUM>, which can provide additional surface to attach the damper assembly <NUM> to the distal end <NUM>, which distal end <NUM> is often open to reduce the mass of the airframe.

<FIG> shows a top view of the distal end <NUM> of the tail boom <NUM> and one configuration of the wire rope damper assembly <NUM>. In this top view, the damper assembly <NUM> is attached to the distal end <NUM> of the tail boom <NUM>, and includes a mass <NUM>, wire ropes 312a, 312b, 312c, 312d, first fasteners 314a, 314b, 314c, and 314d, and second fasteners 316a, 316b. The mass <NUM> is attached to the wire ropes 312a, 312b, 312c, 312d via first fasteners and the wire ropes 312a, 312b, 312c, 312d are connected to the distal end <NUM> of the tail boom <NUM> via second fasteners. Thus, the wire ropes 312a, 312b, 312c, 312d isolate the mass <NUM> from the distal end <NUM> of the tail boom <NUM>.

In <FIG> and <FIG>, the damper assembly <NUM> is located at the aft-most end of the tail boom, which attached to the tail rotor gearbox support airframe structure, however, the exact position for different rotorcraft can be selected for convenience and/or effectiveness. While there is no specific requirement on location, the damper assembly can work at multiple locations throughout the aircraft, with one factor being that the attaching structure must be stiff enough (of additional stiffening added) to support the damper assembly.

<FIG> shows an isometric view of the distal end <NUM> of the tail boom <NUM> and one configuration of the wire rope damper assembly <NUM>. In this top view, the damper assembly <NUM> is attached to the distal end <NUM> of the tail boom <NUM>, and includes a mass <NUM>, wire ropes 312b, 312c, 312d, first fasteners 314b, and second fasteners 316a, 316b. The mass <NUM> is attached to the wire ropes 312b, 312c, 312d via first fasteners 314b and the wire ropes 312b, 312c, 312d are connected to the distal end <NUM> of the tail boom <NUM> via second fasteners 316b, 316c, and 316d. Thus, the wire ropes 312b, 312c, 312d isolate the mass <NUM> from the distal end <NUM> of the tail boom <NUM>.

<FIG> shows a side view of a helicopter airframe <NUM> that shows potential location for on or more damper assemblies <NUM>, <NUM>, <NUM>, or <NUM>.

<FIG> shows a diagram of an exploded side view of one configuration of the damper assembly <NUM> of the present invention, which is attached to the tail boom <NUM>. In this configuration, one portion of the wire rope <NUM> is connected via plate <NUM> to the tail boom <NUM>, and the portion of the wire rope <NUM> is connected via plate <NUM> to the mass <NUM>. In this configuration, the wire rope isolator is providing isolation based on shear.

<FIG> shows a diagram of a side view of another configuration of the damper assembly <NUM> of the present invention, which is attached to the tail boom <NUM>. In this configuration, the tail boom <NUM> is shown in a side view, while the damper assembly <NUM> is shown as an end-view of the tail boom <NUM>. The mass <NUM> is depicted as inside the tail boom <NUM>, with the wire ropes 312a, 312b, 312c, and 312d support the mass <NUM> within the tail boom <NUM>. Alternatively, the same configuration of the damper assembly <NUM> could be fitted within a frame positioned, and connected to, the distal end <NUM> of the tail boom <NUM>. For example, in this configuration, the wire rope isolators dampen based on, e.g., <NUM> degree compression and/or roll.

<FIG> shows a diagram of a side view of another configuration of the damper assembly <NUM> of the present invention, which is attached to the tail boom <NUM>, and in which the mass is the tail ballast. In this configuration, the wire rope <NUM> is connected to plate <NUM> and plate <NUM>, one of which is attached to the mass <NUM>, and the mass is positioned below the plate and wire assembly <NUM>. In this configuration, the wire rope isolators dampen based on compression.

<FIG> shows a diagram of an end view of one configuration of the damper assembly <NUM> within the tail boom <NUM>. The mass <NUM> is depicted in the center of the tail boom <NUM>, and the mass <NUM> is shown attached to the wire ropes 312a, 312b, 312c, and 312d via plates 320a, 320b, 320c, and 320d, and the wire ropes 312a, 312b, 312c, and 312d are attached to the tail boom via plates 322a, 322b, 322c, and 322d. In this configuration, the plates 320a-320d and 322a-322d are attached to the sides of wire ropes 312a-d, which provide for isolation in different directions, e.g., along the longitudinal axis of the wire ropes 312a-d, and based on the stiffness of the overall wire ropes 312a-312d, all of which can be optimized to maximize the dampening of vibrations by the mass <NUM>. In this configuration, the longitudinal axis of the wire ropes 312a-312d are depicted as being generally perpendicular to the longitudinal axis of the tail boom <NUM>, however, the skilled artisan will recognize that the longitudinal axis of the wire ropes 312a-312d can be varied in relation to the longitudinal axis of the tail boom <NUM> for each of wire ropes 312a-312d. In this configuration, the wire rope isolators can be a compact rope isolator that each provide dampening based on both compression and shear.

<FIG> shows a diagram of an end view of one configuration of the damper assembly <NUM> within the tail boom <NUM>. The mass <NUM> is depicted in the center of the tail boom <NUM>, and the mass <NUM> is shown attached to the wire ropes 312a, 312b, 312c, and 312d via plates 320a, 320b, 320c, and 320d, and the wire ropes 312a, 312b, 312c, and 312d are attached to the tail boom. In this configuration, the plates 320a-320d are attached to the sides of wire ropes 312a-312d, which provide for isolation in different directions, e.g., along the longitudinal axis of the wire ropes 312a-312d, and based on the stiffness of the overall wire ropes 312a-312d, all of which can be optimized to maximize the dampening of vibrations by the mass <NUM>. In this configuration, the longitudinal axis of the wire ropes 312a-312d are depicted as being generally parallel to the longitudinal axis of the tail boom <NUM>, however, the skilled artisan will recognize that the longitudinal axis of the wire ropes 312a-312d can be varied in relation to the longitudinal axis of the tail boom <NUM> for each of wire ropes 312a-312d. In this configuration, the wire rope isolators can be a wire rope isolator that each provide dampening based on both compression and roll.

<FIG> shows a diagram of a side view of one configuration of the damper assembly <NUM> of the present invention connected to an airframe <NUM>. In this configuration, the damper assembly <NUM> includes the mass <NUM> (which can be, e.g., the tail ballast) that is connected via wire ropes 312a, 312b and first fasteners 314a, 314b. The wire ropes 312a, 312b are connected to the airframe <NUM> via second fasteners 316a, 316b. In this configuration, the mass <NUM> is cantilevered.

<FIG> shows a diagram of a side view of one configuration of the damper assembly <NUM> of the present invention connected to an airframe <NUM>. In this configuration, the damper assembly <NUM> includes the mass <NUM> (which can be, e.g., the tail ballast) that is located between pairs of wire ropes 312a, 312b and 312c, 312d and first fasteners 314a, 314b, 314c, 314d. The pairs of wire ropes 312a, 312b and 312c are connected to the airframe <NUM> via second fasteners 316a, 316b, 316c, 316d. In this configuration, the mass <NUM> is supported on both sides.

<FIG> shows a diagram of a side view of another configuration of the damper assembly <NUM> of the present invention connected to an airframe <NUM> via plate <NUM>. In this configuration, the damper assembly <NUM> includes the mass <NUM> (which can be, e.g., the tail ballast) that is connected via wire ropes 312a, 312b and first fasteners 314a, 314b to the plate <NUM>. The plate <NUM> is attached to the airframe <NUM>. The mass <NUM> is connected to the wire ropes 312a, 312b via second fasteners 316a, 316b along a narrow portion of the wire ropes 312a, 312b.

<FIG> shows a diagram of a side view of configuration of the damper assembly <NUM> of the present invention connected to an airframe <NUM>, but in which the wider portion of the wire ropes 312a, 312b is attached to the mass <NUM>. In this configuration, the damper assembly <NUM> includes the mass <NUM> (which can be, e.g., the tail ballast) that is located between pairs of wire ropes 312a, 312b and 312c, 312d and first fasteners 314a, 314b, 314c, 314d. The pairs of wire ropes 312a, 312b and 312c are connected to the airframe <NUM> via second fasteners 316a, 316b, 316c, 316d.

All of the devices and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure.

Claim 1:
An airframe having a tail boom (<NUM>) and a damper assembly (<NUM>), wherein the damper assembly (<NUM>) comprises:
a mass (<NUM>) to damp the vibration of the airframe (<NUM>);
one or more wire rope isolators having a first and a second portion, wherein the mass (<NUM>) is attached to the one or more wire rope isolators (312a-d) and the mass (<NUM>) is isolated from the airframe (<NUM>) by the one or more wire rope isolators (312a-d); and
first fasteners (314a, 314b) and second fasteners (316a, 316b), wherein the first fasteners (314a, 314b) attach the first portion of the one or more wire rope isolators (312a-d) directly to the mass (<NUM>), and the second fasteners (316a, 316b) attach the second portion of the one or more wire rope isolators (312a-d) to the airframe (<NUM>) to dampen vibration of the airframe (<NUM>), and
wherein the mass (<NUM>) is positioned at the end of the tail boom (<NUM>), along the length of the tail boom (<NUM>), or a combination thereof.