Patent Description:
Some types of aircraft include engines attached to the wings, fuselage, or tail of the aircraft. The engines have nacelles which are outer casings for the engine components. A nacelle includes an inlet section at a leading or front end of the nacelle. The nacelle may also include a fan cowl, a thrust reverser section, and an aft fairing section located behind the inlet section along a longitudinal length of the nacelle. The inlet section has an inner barrel that defines an air inlet duct for directing air to the fan and downstream components of the engine. The inner barrel may have an acoustic panel to facilitate reducing noise created by the fan and a compressor of the engine.

There are several advantages associated with a compact nacelle. For example, shortening the nacelle along the longitudinal length may improve fuel burn and reduce drag, weight, and material costs. However, shortening the inlet section undesirably results in less available volume and surface area in which to integrate noise treatment and anti-ice systems. For example, there may be less space available within the inlet section for the acoustic panel, requiring a shorter acoustic panel. Some known anti-ice systems direct a stream of hot engine bleed air into a channel of the inlet section defined between a front end of the inlet and a bulkhead within the inlet. The hot air stream heats the leading edge of the inlet section to melt and/or prevent the formation of ice on the exterior surface of the inlet section. This pneumatic, bleed air-based anti-ice system has several drawbacks, including relatively high complexity (e.g., requiring valves and conduits to control the blead air, as well as bulkheads in the inlet), reduced fuel efficiency (e.g., fuel economy) due to the use of bleed air for heating rather than propulsion, lower maximum thrust level able to be generated by the engine, and the like.

<CIT>, in accordance with its abstract, states a nacelle having a porous structure is provided with laminar flow control and contamination protection. In region suction through a composite layer is achieved by evacuating a chamber adjacent the inner surface of the nacelle to provide laminar flow control. At the leading edge of the nacelle a sintered metal sheet is attached to an inner surface of the composite layer to control the flow of a liquid over the leading edge of the nacelle. The liquid is contained in a chamber adjacent the sintered metal sheet which is defined by a backing sheet which has a series of depressions therein. Hot air fed through a perforated pipe impinges upon the backing sheet and the depressions transmit heat to the sintered metal sheet.

<CIT>, in accordance with its abstract, states an inlet for an aircraft nacelle may comprise a nano reinforced polyimide composite lip skin. A lip skin for an inlet with an electric heater may comprise a surface layer, an outer composite skin, an electric heater, an inner composite skin, and a thermal barrier coating. A lip skin for an inlet with a pneumatic deicing system may comprise a surface layer, a composite skin, and a thermal barrier coating.

<CIT>, in accordance with its abstract, states an aircraft engine nacelle inlet is provided with an inlet cowling. The inlet cowling includes an inner lip, an outer lip, and a leading edge portion connecting the inner and outer lips. Heating elements are provided proximate the leading edge, either on an inside surface of the cowling or on an outside surface. An inner barrel portion and an outer barrel portion of the nacelle inlet define a space therebetween. Ice protection-related equipment such as controllers, cables, switches, connectors, and the like, may reside in this space. One or more access openings are formed in the outer barrel to enable an operator to gain access to this equipment. The inlet cowling attaches to the inner and outer barrels with its outer lip extending sufficiently far in the aft direction to cover the access opening.

<CIT>, in accordance with its abstract, states an inlet design including a single bulkhead and/or an acoustic panel extending into nacelle lip region. The inlet is used with a fluid ice protection system.

<CIT>, in accordance with its abstract, states a porous panel for use principally, but not exclusively, for the distribution of a freezing point depressant liquid on an aircraft surface. The panel comprises an outer porous sheet over the surface of which the fluid is to be distributed, a backing sheet of microporous material in contact with one side of the outer sheet, and a sheet of fluid impervious material which is spaced from the microporous sheet. The sheets may be secured to one another by adhesive bonding over a region located outwardly of the space. The outer sheet may be a porous material, a reinforced porous plastic material or a drilled sheet material.

A need exists for a nacelle inlet assembly and method of assembly that solves or at least mitigates volume constraint issues associated with a shorter, more compact nacelle, enabling the aircraft to achieve greater fuel efficiency.

According to a first aspect, there is provided an inlet assembly of a nacelle as defined in claim <NUM>.

According to a second aspect, there is provided a method for providing an inlet assembly of a nacelle as defined in claim <NUM>.

In general terms, there is provided an inlet assembly of a nacelle. The inlet assembly includes an inlet cowl and a fluid ice protection system (FIPS). The inlet cowl includes a leading edge, an inner barrel portion, and an outer barrel portion. The inlet cowl has a lipskin and an acoustic panel. The lipskin includes a front section which defines the leading edge of the inlet cowl. The front section includes a composite panel and a metallic coating disposed along an exterior surface of the composite panel to protect the composite panel from damage. The lipskin defines perforations that penetrate through the composite panel and the metallic coating at the front section to convey a liquid through a thickness of the lipskin onto an exterior surface of the inlet cowl. The acoustic panel is coupled to the lipskin and extends along the inner barrel portion. The FIPS includes a plenum back wall affixed to an interior surface of the composite panel along the front section to define a plenum between the interior surface and a front surface of the plenum back wall. The FIPS includes a fluid delivery conduit coupled to the plenum back wall and configured to supply an anti-ice liquid into the plenum through an aperture in the plenum back wall for the anti-ice liquid in the plenum to penetrate through the perforations onto an exterior surface of the inlet cowl.

These and other features, aspects, and advantages of the present disclosure will become better understood when the following detailed description is read with reference to the accompanying drawings in which like numerals represent like parts throughout the drawings, wherein:.

The foregoing summary, as well as the following detailed description of certain embodiments will be better understood when read in conjunction with the appended drawings. Further, references to "one embodiment" are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Moreover, unless explicitly stated to the contrary, embodiments "comprising" or "having" an element or a plurality of elements having a particular property may include additional elements not having that property.

This nacelle inlet assembly with composite lipskin was made with UK Government support under <NUM> - UK Aerospace Research and Technology Programme. The UK Government may have certain rights in this nacelle inlet assembly with composite lipskin.

Certain embodiments of the present disclosure provide systems and methods for providing an inlet assembly that has a short inlet architecture. The inlet assembly may be incorporated into a compact, short nacelle to achieve greater fuel efficiency relative to a longer nacelle. In one or more embodiments, the inlet assembly includes an inlet cowl that has a lipskin. The lipskin includes a composite panel with a metallic coating along an exterior surface of the composite panel. The metallic coating provides an erosion shield to protect against leading edge damage. For example, the metallic coating is exposed along the leading edge to sunlight, wind, moisture, debris, birds, and/or the like, and protects the composite panel from such elements. In an embodiment, the composite panel is or includes carbon fiber. For example, the composite panel may have a carbon fiber reinforced polymer (CFRP) material.

The inlet assembly according to an embodiment includes a fluid ice protection system (FIPS) that is operably connected to the inlet cowl. For example, the FIPS may supply an anti-ice liquid to an interior surface of the lipskin. The anti-ice liquid may be a freezing point depression compound, such as a glycol-based solution. The lipskin of the inlet cowl may include perforations (e.g., holes) that extend through the thickness of the lipskin, such that each perforation penetrates through both the composite panel and the metallic coating. The perforations may be relatively small and may be laser-formed. For example, the perforations may be microscopic (e.g., with micron scale diameters). The anti-ice liquid may weep through the perforations onto the exterior surface of the metallic coating. The liquid prevents the formation of ice (and removes any ice already present) along the inlet, which can be detrimental to flight and engine performance. The FIPS may include a plenum back wall that is coupled to the interior surface of the lipskin to define a plenum (e.g., cavity). The anti-ice liquid is supplied to the plenum through one or more conduits that extend from a reservoir remote from the inlet cowl. The FIPS may include one or more membranes within the plenum that absorb and distribute the anti-ice liquid to the perforations. For example, the membrane(s) may extend across and cover all or a majority of the perforations, such that the anti-ice fluid enters the perforations from the membrane(s).

In an embodiment, the lipskin has an outer barrel portion that extends aft for a longer length than at least some conventional inlet cowls. For example, the outer barrel portion of the lipskin may extend aft to an interface with the fan cowl. By extending the lipskin all the way to the fan cowl along the outer side, the inlet cowl described herein may lack a discrete composite outer barrel that is coupled to the lipskin. The composite panel with metallic coating may extend from the leading edge along the outer barrel portion to the interface with the fan cowl. In addition to reducing assembly steps and materials by omitting a separate outer barrel panel, providing a single, unitary structure along the outer length of the inlet may beneficially enlarge the region of laminar air flow along the inlet. For example, the exterior surface of the inlet cowl may be smooth and free of seams from the leading edge along the outer barrel portion to the end of the lipskin, which results in a low likelihood of turbulent air flow along the outer barrel portion. At least some conventional inlet cowls may include seams at interfaces between the lipskin and the outer barrel panel. The seams increase turbulence of the air flow, which is detrimental to flight and engine performance. The inlet cowl described herein may provide an extended natural laminar flow surface, resulting in improved aerodynamic performance. The inlet cowl may include support frames within an interior of the inlet cowl to mechanically support the extended length of the lipskin and withstand forces exerted on the exterior of the lipskin. One or more of the support frames may be open truss-like structures. Optionally, some of the support frames may extend longitudinally, and others of the support frames may extend circumferentially. The support frames may be located aft of the plenum back wall of the FIPS.

Referring now to the drawings, which illustrate various embodiments of the present disclosure, <FIG> is a perspective illustration of an aircraft <NUM>. The aircraft <NUM> may include a fuselage <NUM> extending from a nose <NUM> to an empennage <NUM>. The empennage <NUM> may include one or more tail surfaces for directional control of the aircraft <NUM>. The aircraft <NUM> includes a pair of wings <NUM> extending from the fuselage <NUM>. The aircraft <NUM> includes one or more propulsion systems <NUM> which are optionally supported by the wings <NUM>. In an embodiment, each propulsion system <NUM> may include or represent a gas turbine engine <NUM> surrounded by a nacelle <NUM>. In an alternative embodiment, one or more of the propulsion systems <NUM> may include motor-driven rotors surrounded by the nacelle <NUM> instead of a gas turbine engine. For example, the motor of such propulsion systems <NUM> may be powered by electrical energy supplied by an onboard battery system and/or an onboard electrical energy generation system. The nacelle <NUM> may have an exhaust nozzle <NUM> (e.g., a primary exhaust nozzle and a fan nozzle) at an aft end of the propulsion system <NUM>.

<FIG> illustrates an embodiment of a nacelle <NUM> of a propulsion system of an aircraft according to an embodiment. The nacelle <NUM> may be one of the nacelles <NUM> of the propulsion systems <NUM> shown in <FIG>. The nacelle <NUM> extends a length from a front end <NUM> of the nacelle <NUM> to an aft end <NUM> of the nacelle <NUM> (opposite the front end <NUM>). The nacelle <NUM> may include an inlet cowl <NUM> and a fan cowl <NUM>. The inlet cowl <NUM> defines a leading edge <NUM> of the nacelle <NUM> at the front end <NUM>, to direct air into a core <NUM> of the nacelle <NUM>. The fan cowl <NUM> is aft of the inlet cowl <NUM> and is connected to the inlet cowl <NUM>. The fan cowl <NUM> may connect to and extend from an aft edge <NUM> of the inlet cowl <NUM>. The fan cowl <NUM> may surround one or more fans mounted at a forward end of the engine within the core <NUM>.

The nacelle <NUM> may include a mount <NUM> for securing the nacelle <NUM> and the rotary components held by the nacelle <NUM> to the aircraft. The mount <NUM> may be a pylon. The nacelle <NUM> includes at least one aft section <NUM> that is disposed aft of the fan cowl <NUM> along the length of the nacelle <NUM>. The aft section(s) <NUM> may surround engine components such as a compressor, combustion chamber (or combustor), and turbine. The aft section(s) <NUM> may include or represent a thrust reverser, aft fairing, or the like. The aft section(s) <NUM> may define the aft end <NUM> and an aft nozzle through which air and exhaust products are emitted from the propulsion system.

<FIG> is a front view of the inlet cowl <NUM> shown in <FIG>. <FIG> is a perspective view of the inlet cowl <NUM> shown in <FIG> and <FIG>, showing the aft edge <NUM> of the inlet cowl <NUM>. The inlet cowl <NUM> has an annular barrel shape that defines a central opening <NUM>. The term "annular barrel shape" means that the inlet cowl <NUM> defines a closed, ring-like shape when viewed from the front. The inlet cowl <NUM> may have a generally cylindrical shape. For example, the leading edge <NUM> may be circular. The inlet cowl <NUM> directs air through the central opening <NUM> into the core <NUM> of the nacelle <NUM> shown in <FIG>. The inlet cowl <NUM> has an outer barrel portion <NUM> radially outside of the leading edge <NUM> and an inner barrel portion <NUM> radially inside of the leading edge <NUM>. The inner barrel portion <NUM> may define the central opening <NUM>, and operates as an intake duct to supply air into the core <NUM> for the rotary components. As shown in <FIG>, the outer barrel portion <NUM> surrounds the inner barrel portion <NUM>. The outer barrel portion <NUM> may be radially offset from the inner barrel portion <NUM> to define a cavity <NUM> within the inlet cowl <NUM>. The cavity <NUM> is closed at a front end <NUM> of the inlet cowl <NUM>, and open at a rear or aft end <NUM>.

The inlet cowl <NUM> extends a length along a central longitudinal axis <NUM>. The inlet cowl <NUM> includes a lipskin <NUM> and an acoustic panel <NUM>. The lipskin <NUM> may define the leading edge <NUM> and the outer barrel portion <NUM>. The acoustic panel <NUM> is coupled to the lipskin <NUM> along the inner barrel portion <NUM>, and the acoustic panel <NUM> defines a length of the inner barrel portion <NUM>. For example, the lipskin <NUM> may define a front section of the inner barrel portion <NUM> along the length of the inlet cowl <NUM>, and the acoustic panel <NUM> may define an aft section of the inner barrel portion <NUM>, which extends to an inner aft edge <NUM>. As a part of the inlet cowl <NUM>, the acoustic panel <NUM> is located forward of the fan cowl <NUM>. The acoustic panel <NUM> may be located in relatively close proximity to one or more fans or other rotary equipment. The acoustic panel <NUM> may have a plurality of perforations for absorbing noise generated by the rotary equipment and/or the airflow passing through the inlet cowl <NUM>.

As shown in <FIG>, the inlet cowl <NUM>, including the lipskin <NUM> and acoustic panel <NUM>, may represent a portion of an inlet assembly <NUM>. The inlet assembly <NUM> may include at least a portion of an anti-ice FIPS (shown in <FIG>) integrated within the cavity <NUM> of the inlet cowl <NUM>. The FIPS supplies an anti-ice fluid onto an exterior surface <NUM> of the inlet cowl <NUM> to prohibit ice formation on the exterior surface <NUM>. The exterior surface <NUM> that receives the anti-ice fluid is at and around the leading edge <NUM>. The exterior surface <NUM> is exposed to the elements, such as sunlight, moisture, debris, wind, birds, etc..

The inlet assembly <NUM> may include support frames <NUM> within the cavity <NUM> of the inlet cowl to mechanically support the lipskin <NUM> and the acoustic panel <NUM>. The support frames <NUM> may help withstand pressure and other forces exerted on the exterior surface <NUM>. One or more of the support frames <NUM> may be open truss-like structures that enable air flow through openings in the support frames <NUM>. In an embodiment, the inlet assembly <NUM> may lack bulkheads that partition the cavity <NUM> into multiple channels or regions that are blocked off from each other (e.g., fluidly isolated from each other). Avoiding bulkheads which sub-divide the cavity may reduce the complexity of manufacturing the inlet assembly <NUM> relative to conventional inlets.

<FIG> is a cross-sectional view of a portion of the inlet assembly <NUM> according to an embodiment. The illustrated portion shows the lipskin <NUM> of the inlet cowl <NUM> without the acoustic panel <NUM>. For example, the acoustic panel <NUM> may couple to an inner edge <NUM> of the lipskin <NUM> during the assembly process. The lipskin <NUM> in the illustrated embodiment has a curved shape that radially and longitudinally extends forward from the inner edge <NUM> to the leading edge <NUM>, and then rearward to an outer, aft edge <NUM> of the lipskin <NUM>. The lipskin <NUM> may be relatively thin. The area of the lipskin <NUM> that includes the leading edge <NUM> and the areas immediately radially adjacent to the leading edge <NUM> is referred to herein as a front section <NUM> of the lipskin <NUM>. The outer, aft edge <NUM> may define the aft edge <NUM> of the inlet cowl <NUM>, such that the lipskin <NUM> extends the full length of the inlet cowl <NUM> along the outer barrel portion <NUM>. As shown in <FIG>, the exterior surface <NUM> of the inlet cowl <NUM> is smooth and defined by a single, continuous construct (e.g., the lipskin <NUM>) along the entire length of the outer barrel portion <NUM>. There are no seams, joints, or interfaces from the leading edge <NUM> to the aft edge <NUM>, which promotes laminar air flow along the aerodynamic exterior surface <NUM>, providing a substantial drag benefit. The inlet assembly <NUM> described herein may provide a longer and/or larger surface area along which the air flow is laminar, relative to the inlet size, than conventional inlets.

The inlet assembly <NUM> may include a plenum back wall <NUM> that is affixed to the inlet cowl <NUM>. The plenum back wall <NUM> is a component of an anti-ice FIPS <NUM>. The plenum back wall <NUM> is disposed within the cavity <NUM> of the inlet cowl <NUM> and extends along the front section <NUM> of the lipskin <NUM>. The plenum back wall <NUM> may be bonded, directly or indirectly, to an interior surface <NUM> of the lipskin <NUM>. In an embodiment, the lipskin <NUM> includes integrated protrusions <NUM> that serve as mounts on which to affix the plenum back wall <NUM>. The protrusions <NUM> may be integral to the lipskin <NUM> and define sections of the interior surface <NUM>. In an alternative embodiment, the protrusions <NUM> may be discrete components that are themselves mounted to the interior surface <NUM> and serve to indirectly secure the plenum back wall <NUM> to the lipskin <NUM>. The plenum back wall <NUM> is mounted to the inlet cowl <NUM> to define a plenum <NUM> (e.g., fluid manifold) for receiving and containing the anti-ice liquid of the FIPS <NUM>. The plenum <NUM> is defined between the interior surface <NUM> of the lipskin <NUM> and a front surface <NUM> of the back wall <NUM>. The plenum <NUM> may be located along the front section <NUM> of the lipskin <NUM> only, such that the plenum <NUM> does not extend along the outer barrel portion <NUM>.

<FIG> illustrates an enlarged, schematic rendering of the inlet assembly <NUM> at the leading edge <NUM> according to an embodiment. The illustrated components in <FIG> are depicted for ease of description, and may not be drawn to scale and/or in the actual shapes as would be present in a prototype.

The lipskin <NUM> in an embodiment is a stack-up of multiple different layers. The lipskin <NUM> may include at least a composite panel <NUM> and a metallic coating <NUM>. The metallic coating <NUM> is exterior of the composite panel <NUM> to provide an erosion shield that protects the composite panel <NUM> from leading edge damage. The metallic coating <NUM> may define the exterior surface <NUM> of the inlet cowl <NUM> along all of the surface area of the inlet cowl <NUM> that is exposed to the environmental elements. The composite panel <NUM> and metallic coating <NUM> may extend the full length of the lipskin <NUM>.

The composite panel <NUM> has an interior surface <NUM> and an exterior surface <NUM> opposite the interior surface <NUM>. The interior surface <NUM> may define the interior surface <NUM> of the lipskin <NUM>. The metallic coating <NUM> is disposed along the exterior surface <NUM> of the composite panel <NUM>. In an embodiment, the metallic coating <NUM> is indirectly connected to the exterior surface <NUM> via one or more intervening layers. The one or more intervening layers include an electrically conductive layer <NUM> that is provided to assist with the application of the metallic coating <NUM> on the composite panel <NUM>. The conductive layer <NUM> may be a metallic material that has a different composition than the metallic coating <NUM>.

In an embodiment, the composite panel <NUM> is or includes carbon fiber. For example, the composite panel <NUM> may have a carbon fiber reinforced polymer (CFRP) material. The polymer may be a thermoplastic or the like. The metallic coating <NUM> may be a metal alloy. For example, the metallic coating <NUM> in an embodiment is a nickel-cobalt (NiCo) alloy. The metallic coating <NUM> may be deposited onto the lipskin <NUM> to solidify and harden. In an embodiment, the metallic coating <NUM> is applied via electroplating. For example, the metallic coating <NUM> may be a NiCo alloy that is electroplated onto the lipskin <NUM>.

The lipskin <NUM> may define multiple perforations <NUM> that penetrate the thickness of the lipskin <NUM> along the front section <NUM>. The perforations <NUM> may extend continuously through the composite panel <NUM>, the conductive layer <NUM>, and the metallic coating <NUM>. The perforations <NUM> are aligned with and open to the plenum <NUM>, such that the perforations <NUM> receive anti-ice liquid <NUM> from the plenum <NUM>. The characteristics of the perforations <NUM> (e.g., diameter, location, percent-open-area, etc.) may be selected based on application-specific parameters. In an embodiment, the perforations <NUM> have micron scale diameters. The microscopic perforations <NUM> may be formed via a laser drilling technique. The tiny perforations <NUM> enable to the liquid <NUM> under pressure to slowly weep through the perforations <NUM> onto the exterior surface <NUM>. The anti-ice liquid <NUM> may be a solution that provides freezing point depression. For example, the anti-ice liquid <NUM> may be an ethylene glycol-based solution.

The illustrated components of the FIPS <NUM> in the inlet assembly <NUM> may include the plenum back wall <NUM>, a fluid delivery conduit <NUM> that is coupled to the plenum back wall <NUM>, and one or more membranes <NUM>. The conduit <NUM> may be a duct, tube, or the like that provides a path from a fluid reservoir to the plenum <NUM>. The anti-ice liquid <NUM> may be pumped through the conduit <NUM> into the plenum <NUM> through an aperture in the back wall <NUM>. The one or more membranes <NUM> are disposed within the plenum <NUM> (e.g., between the lipskin <NUM> and the back wall <NUM>) and receive the anti-ice liquid <NUM>. A single membrane <NUM> is shown in <FIG>. The membrane <NUM> may be designed to absorb and distribute the anti-ice liquid <NUM> to the perforations <NUM>. For example, the membrane <NUM> may extend across and cover all or a majority of the perforations <NUM>. The membrane <NUM> may spread the liquid <NUM> along a length of the membrane <NUM> which supports a more uniform distribution of the liquid <NUM> among the perforations <NUM>. The membrane <NUM> optionally may be a porous material, such as an open-celled foam material.

In an embodiment, the plenum back wall <NUM> includes first and second flanges <NUM> at respective ends of the back wall <NUM>. The flanges <NUM> are secured to the protrusions <NUM> of the lipskin <NUM> along respective contact interfaces <NUM>. The flanges <NUM> may be bonded to the protrusions <NUM> at the contact interfaces <NUM>. The bonding may be accomplished via application of an adhesive, a heat treatment, and/or the like. In an embodiment, the contact interfaces <NUM> are angled transverse to the tangent of the interior surface <NUM> of the lipskin <NUM> proximate to the contact interfaces <NUM> to enhance retention of the plenum back wall <NUM> to the lipskin <NUM>. The contact interfaces <NUM> extend along ramp surfaces <NUM> of the protrusions <NUM>. The contact interfaces <NUM> have vectors <NUM> that are not parallel to the tangent <NUM> of the interior surface <NUM>. The contact interfaces <NUM> are angled to shift the pressure loading dynamics along the bonded interfaces <NUM> and enable the plenum back wall <NUM> to withstand more force before separating from the lipskin <NUM>, relative to bonding the back wall <NUM> to the lipskin <NUM> without the protrusions <NUM>.

For example, the plenum <NUM> may experience pressure that tends to force the plenum back wall <NUM> away from the leading edge <NUM>, as indicated by the force arrows <NUM>. Furthermore, the composite panel <NUM> and the protrusions <NUM> are not metallic, so the plenum back wall <NUM> cannot be welded to the lipskin <NUM>. In an embodiment, the protrusions <NUM> may be composed of a rigid, closed-cell foam. By bonding the flanges <NUM> to the protrusions <NUM> along the angled contact interfaces <NUM>, the forces exerted on the back wall <NUM> are withstood by shear retention along the contact interfaces <NUM>. For example, the forces on the back wall <NUM> may be acutely angled relative to the interface vectors <NUM>, which is resisted in part by shear loading at the interfaces <NUM>. Without the angled contact interfaces <NUM>, the forces on the back wall <NUM> may peel the back wall <NUM> off the interior surface <NUM> of the lipskin <NUM>, breaking the FIPS <NUM>.

<FIG> is a cross-sectional view of a nose portion of the inlet assembly <NUM> according to an embodiment. <FIG> is an enlarged view of a segment of the nose portion shown in <FIG>. The views in <FIG> may be more accurate in terms of scale and shapes of the components relative to the illustration in <FIG>. <FIG> shows the leading edge <NUM> of the lipskin <NUM>, the plenum back wall <NUM>, the protrusions <NUM>, and the membrane <NUM>. With reference to both <FIG>. the thin membrane <NUM> is disposed within the plenum <NUM>. The flanges <NUM> of the back wall <NUM> are secured to the ramp surfaces <NUM> of the protrusions <NUM>, as described with reference to <FIG>. In an embodiment, the plenum back wall <NUM> may be a composite structure. For example, the back wall <NUM> may include a core layer <NUM> sandwiched between two outer layers <NUM>. The core layer <NUM> may be a honeycomb structure. In an embodiment, the protrusions <NUM> may include a rigid, closed-cell foam material. The protrusions <NUM> may be integrated onto the lipskin <NUM>, such as formed with the composite panel <NUM>.

<FIG> is a cross-sectional view of a portion of the inlet assembly <NUM> according to an embodiment. <FIG> shows the acoustic panel <NUM> longitudinally extending along the inner barrel portion <NUM>, and the lipskin <NUM> longitudinally extending the length of the outer barrel portion <NUM>. The plenum back wall <NUM> is disposed at the front end of the cavity <NUM>, interior of the leading edge <NUM>. The inlet assembly <NUM> may include support frames within the cavity <NUM> to mechanically support the extended length of the lipskin <NUM> and withstand forces exerted on the lipskin <NUM> to maintain the shape of the inlet cowl <NUM>.

In an embodiment, the support frames include longitudinally extending support frames <NUM> that are circumferentially spaced apart. The support frames may also include circumferentially extending support frames <NUM>. The circumferentially extending support frames <NUM> may be located proximate to the aft edge <NUM> of the inlet cowl <NUM>. For example, the support frames <NUM> may be coupled to a flange <NUM> mounted to an aft edge <NUM> of the acoustic panel <NUM>. The support frames <NUM> may be perpendicular to the support frames <NUM>. The support frames <NUM>, <NUM> may all extend from the outer barrel portion <NUM> to the inner barrel portion <NUM>. In an embodiment, the support frames <NUM>, <NUM> are open, truss-like structures that permit fluid flow through openings <NUM> in the frames <NUM>, <NUM>. The support frames <NUM>, <NUM> may be rearward or aft of the plenum back wall <NUM>.

Optionally, the outer barrel portion <NUM> may extend aft beyond the aft edge <NUM> of the acoustic panel <NUM>. The inlet assembly <NUM> may include one or more triangular support frames <NUM> to support the overhanging, cantilevered portion <NUM> of the outer barrel portion <NUM>.

<FIG> is a schematic diagram depicting a process of assembling an inlet assembly according to an embodiment. The inlet assembly manufactured by the process may be the inlet assembly <NUM> shown in <FIG>. At box <NUM>, a curved tool <NUM> is prepped for a layup process. The curved tool <NUM> may be a mold or mandrel. The tool <NUM> may have a shape that corresponds to a desired shape of the inlet cowl. At box <NUM>, a carbon fiber reinforced polymer (CFRP) material is applied on the curved tool <NUM> to form the composite panel <NUM> via a layup process. The layup process may be an automated fiber placement (AFP) process in which multiple layers of fiber-reinforced material are applied on the tool <NUM>. The layers may be tows or bundles of carbon fibers impregnated with an epoxy resin. The tows may be applied in different orientations relative to one another. Although not shown, the protrusions <NUM> of the lipskin <NUM> may be formed during the layup step shown in box <NUM>.

The composite panel <NUM> may then be cured via a heat treatment and removed from the tool <NUM>. The conductive layer <NUM> is applied to the exterior surface <NUM> of the composite panel <NUM>. At box <NUM>, non-plated areas of the composite panel <NUM> are masked by a maskant <NUM>. The conductive layer <NUM>, if present, may be co-cured at box <NUM>.

At box <NUM>, the metallic coating <NUM> is applied on the composite panel <NUM> (and conductive layer <NUM>) by electroplating. The metallic coating <NUM> is shown in the inset enlarged view in box <NUM>. At box <NUM>, the maskant is removed from the structure, yielding the lipskin <NUM> (or stack). At box <NUM>, the lipskin <NUM> is laser drilled to form perforations <NUM> through the thickness thereof in the front section <NUM>. At box <NUM>, the membrane <NUM> is applied along the interior surface <NUM> of the lipskin <NUM> to cover the perforations <NUM>.

Box <NUM> shows a portion of the completed inlet assembly <NUM>, similar to the view in <FIG>. The assembly process may include additional steps not depicted in <FIG>, such as bonding the plenum back wall <NUM> to the composite panel <NUM> and connecting the fluid delivery conduit <NUM> to the plenum back wall <NUM>. Additional portions of the FIPS <NUM> may need to be assembled before the FIPS <NUM> is operational. <FIG> is a flow chart <NUM> for a method of forming an inlet cowl of a nacelle inlet assembly according to an embodiment. The method may be performed to form the inlet cowl <NUM> shown in <FIG>. The method optionally may include at least one additional step than shown, at least one fewer step than shown, and/or at least one different step than shown in <FIG>. The inlet cowl <NUM> is formed to include a leading edge <NUM> and an outer barrel portion <NUM>, where the outer barrel portion extends to an aft edge <NUM> of the inlet cowl <NUM>. At step <NUM>, a carbon fiber reinforced polymer (CFRP) material is applied on a curved tool <NUM>. At step <NUM>, the CFRP material is cured to form a composite panel <NUM> of a lipskin <NUM>. The lipskin <NUM> includes a front section <NUM> that defines the leading edge <NUM> of the inlet cowl <NUM>. At step <NUM>, first and second protrusions <NUM> are formed that project from the interior surface <NUM> of the composite panel <NUM>.

At step <NUM>, a metallic coating <NUM> is applied along an exterior surface <NUM> of the composite panel <NUM> to protect the composite panel <NUM> from damage. Applying the metallic coating <NUM> may include electroplating the metallic coating <NUM> along the composite panel <NUM>. In an embodiment, the CFRP material is applied and cured, and the metallic coating <NUM> is applied such that the composite panel <NUM> and the metallic coating <NUM> of the lipskin <NUM> extend from the leading edge <NUM> to the aft edge <NUM> of the outer barrel portion <NUM>.

At step <NUM>, perforations <NUM> are formed that continuously extend through both the composite panel <NUM> and the metallic coating <NUM>. The perforations <NUM> may be located along the front section <NUM> of the lipskin <NUM> and configured to deliver a liquid through a thickness of the lipskin <NUM> onto an exterior surface <NUM> of the inlet cowl <NUM>. The perforations <NUM> may be formed by laser drilling the perforations to have micron scale diameters. At step <NUM>, a membrane <NUM> may be applied along the interior surface <NUM> of the composite panel <NUM> along the front section <NUM>. The membrane <NUM> may distribute the liquid among the perforations <NUM>.

Claim 1:
An inlet assembly (<NUM>) of a nacelle (<NUM>, <NUM>), the inlet assembly (<NUM>) comprising:
an inlet cowl (<NUM>) comprising:
a lipskin (<NUM>) that includes a front section (<NUM>) that defines a leading edge (<NUM>) of the inlet cowl (<NUM>), the front section (<NUM>) including a composite panel (<NUM>) and a metallic coating (<NUM>) disposed along an exterior surface (<NUM>) of the composite panel (<NUM>) to protect the composite panel (<NUM>) from damage, the lipskin (<NUM>) defining perforations (<NUM>) that penetrate through the composite panel (<NUM>) and the metallic coating (<NUM>) at the front section (<NUM>) to convey a liquid through a thickness of the lipskin (<NUM>) onto an exterior surface (<NUM>) of the inlet cowl (<NUM>),
wherein an electrically conductive layer (<NUM>) is sandwiched between the composite panel (<NUM>) and the metallic coating (<NUM>).