Patent Description:
The disclosure relates generally to ice protection systems, more specifically, to de-icing or ice protection systems for aircraft including electrical heating elements.

In operation, aircraft may experience conditions in which icing may occur. For example, a proprotor blade of an aircraft, as well as other parts of the aircraft such as the wing leading edge, may experience the formation of ice when operating in cold or below-freezing temperatures and subjected to liquid water content. The formation of such ice may dramatically alter one or more flight characteristics of the aircraft. For example, the formation of ice may deleteriously affect the aerodynamics of the aircraft and add additional undesirable weight, induce undesirable vibrations, as well as generate a hazard when such ice breaks off and potentially strikes another portion of the aircraft. For example, ice breaking loose from the proprotor may be ingested by the aircraft engine, thereby damaging the engine, or may strike the fuselage or other aerodynamic surfaces. <CIT> discloses an ice protection system according to the preamble of claim <NUM>.

According to a first aspect, an ice protection system according to claim <NUM> is provided.

In various embodiments, the electrically resistive material is a metallic foil. In various embodiments, the first contiguous busbar portion extends along a spanwise axis parallel to the first spanwise zone. In various embodiments, the first spanwise zone is inboard of the first chordwise zone. In various embodiments, the electrical heating mat further defines a second spanwise zone, a third spanwise zone, a second chordwise zone, and a third chordwise zone. In various embodiments, the second chordwise zone is outboard of the first chordwise zone, the third chordwise zone is outboard of the second chordwise zone, and each of the second spanwise zone and the third spanwise zone are inboard of the first chordwise zone. In various embodiments, the electrical heating mat further defines a second busbar portion wherein each of the first busbar portion and the second busbar portion are contiguous with the first chordwise zone. In various embodiments, a chordwise extent along a chordwise axis of each of the first spanwise zone, the second spanwise zone, and the third spanwise zone is delimited by the first busbar portion and the second busbar portion. In various embodiments, the system further comprises a second electrical heating mat of the electrically resistive material. In various embodiments, the first spanwise zone and the first chordwise zone are defined by a respective first resistive element and a second resistive element, wherein the busbar portion is monolithic with at least one of the first resistive element or the second resistive element.

The detailed description of exemplary embodiments herein makes reference to the accompanying drawings, which show exemplary embodiments by way of illustration and their best mode. While these exemplary embodiments are described in sufficient detail to enable those skilled in the art to practice the disclosures, it should be understood that other embodiments may be realized and that logical, chemical, and mechanical changes may be made without departing from the scope of the invention as defined by the claims. For example, the steps recited in any of the method or process descriptions may be executed in any order and are not necessarily limited to the order presented.

The use of terms such as "above," "below," "upper," "lower," "forward," "aft", "inboard", "outboard", "dorsal", "ventral" 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.

With reference to <FIG> and <FIG>, an aircraft such as, for example, tiltrotor aircraft <NUM> is illustrated. Although depicted with reference to tiltrotor aircraft <NUM>, it will be appreciated that the ice protection system and methods therefor may be used on other rotary aircraft, including helicopters, tilt wing aircrafts, quad til-trotor aircraft, unmanned aerial vehicles (UAVs), and other vertical lift or VTOL aircrafts, or can further be used with any device configured with a rotor blade and/or airfoil susceptible to an ice buildup, including fixed wing aircraft, turbine blades, devices with propellers, windmills, and wind turbines.

Tiltrotor aircraft <NUM> may include a fuselage <NUM>, a landing gear <NUM>, a tail member <NUM>, a wing <NUM>, a first propulsion system <NUM>, and a second propulsion system <NUM>. Each propulsion system <NUM>, <NUM> includes a fixed engine such as, for example, a gas turbine engine and a rotatable proprotor <NUM>, <NUM>, respectively. Each rotatable proprotor <NUM>, <NUM> has a plurality of rotor blades <NUM>, <NUM>, (i.e., proprotor blades) respectively, associated therewith. The position of proprotors <NUM>, <NUM>, as well as the pitch of rotor blades <NUM>, <NUM>, can be selectively controlled in order to selectively control direction, thrust, and lift of tiltrotor aircraft <NUM>.

<FIG> illustrates tiltrotor aircraft <NUM> in helicopter mode, in which proprotors <NUM> and <NUM> are positioned substantially vertical to provide a lifting thrust. <FIG> illustrates tiltrotor aircraft <NUM> in an airplane mode, in which proprotors <NUM>,<NUM> are positioned substantially horizontal to provide a forward thrust in which a lifting force is supplied by wing <NUM>. It should be appreciated that tiltrotor aircraft can be operated such that proprotors <NUM>,<NUM> are selectively positioned between airplane mode and helicopter mode, which can be referred to as a conversion mode.

With additional reference to <FIG>, a control system <NUM> for aircraft ice protection is illustrated. Tiltrotor aircraft <NUM> includes a plurality of sensors <NUM> to monitor and measure characteristics of aircraft <NUM>. The sensors <NUM> may be coupled to or in direct electronic communication with aircraft systems such as, for example, propulsion systems <NUM>, <NUM>. The sensors <NUM> may comprise a temperature sensor, a torque sensor, a speed sensor, a pressure sensor, a position sensor, an accelerometer, or any other suitable measuring device known to those skilled in the art. The sensors <NUM> may be configured to measure a characteristic of an aircraft system or component. For example, the fuselage <NUM> may include a sensor <NUM> for sensing outside air temperature (OAT) and a sensor <NUM> for sensing the liquid water content (LWC) of the air passing over the fuselage <NUM>. Sensors <NUM> such as sensors <NUM> and <NUM> may be configured to transmit the measurements to a controller <NUM>, thereby providing sensor feedback about the aircraft system to controller <NUM>. The sensor feedback may be, for example, a speed signal, or may be position feedback, temperature feedback, pressure feedback or other data. In this regard, sensors <NUM> and <NUM> may be in electrical communication with a controller <NUM>.

Controller <NUM> may be in electronic communication with a pilot through a control interface <NUM>, for example, a set of switches, buttons, a multifunction display, and/or the like that a pilot can operate. The control interface <NUM> may display information such as sensor data from the sensors <NUM> or processed information from the controller <NUM>. The control interface may output command signals to the controller <NUM> in response to receiving an interaction via the control interface. The command signals may be used as an input to an ice protection logic <NUM> of the controller <NUM>. The ice protection logic <NUM> may control, via controller <NUM>, various electrical heating elements of an ice protection system of the aircraft <NUM>.

With additional reference to <FIG> and <FIG> an exemplary airfoil <NUM> (e.g., such as one of rotor blades <NUM>, <NUM>) is illustrated. <FIG> illustrates partial perspective view of an exemplary rotor blade <NUM>. Airfoil <NUM> may be is susceptible to an ice buildup. Rotor blade <NUM> includes a spanwise axis <NUM>, a chordwise axis <NUM>, a leading edge <NUM>, a leading edge axis <NUM>, and a trailing edge <NUM>. As illustrated in <FIG>, airfoil <NUM> comprises an ice protection system <NUM>. Ice protection system <NUM> comprises one and may comprise more electrical heating mats (e.g., a first heating mat <NUM> and a second heating mat <NUM>) which may be coupled to the leading edge <NUM> of the airfoil <NUM> as denoted by the shaded area. A heating mat comprises an electrically resistive material and is configured to warm the leading edge of the airfoil <NUM>. The heating mat extends along the spanwise axis <NUM> between the inboard and outboard edge of the airfoil <NUM> and wraps over the dorsal and ventral surface of the airfoil <NUM>. In this regard, the heating mat extends along the chordwise axis <NUM> aft of the leading edge relatively above and below the leading edge axis <NUM>. Stated another way, the heating mats may be wrapped around the leading edge toward the trialing edge.

With additional reference to <FIG>, ice protection system <NUM> is illustrated in schematic block diagram. Ice protection system <NUM> includes a first heating mat <NUM> and a second heating mat <NUM>. Each heating mat <NUM>, <NUM> may be receive electrical power from a respectively independent power supply channel. The heating mats <NUM>, <NUM> may comprise a metallic foil material such as a non-conductive polymer backed metallic foil suitable for etching. The first heating mat <NUM> and the second heating mat <NUM> may comprise separately etched layers of ice protection system <NUM>. Heating mats <NUM>, <NUM> may comprise any suitable resistive heating material suitable for forming to the leading edge of the airfoil <NUM>. A plurality of resistive heating elements <NUM> may be etched in the metallic foil thereby defining a plurality of heating zones of the respective heating mat. In like regard, electrical connections <NUM> (i.e. busbars) between the plurality of heating elements <NUM> and the power supply may be etched into the metallic foil material. In this regard, the etched busbar portions of the heating mat is integral to the respective resistive element and isolated from other elements. Stated another way, the busbar portions is contiguous with the electrically resistive material thereby enabling a dual functionality as an electrical coupling and as an additional heating element of the respective heating zone.

With additional reference to <FIG>, a resistive heating element <NUM> is shown illustrating details of etching on the metallic foil material <NUM>. The metallic foil material <NUM> may include a first junction strip <NUM>, a second junction strip <NUM>, and a patterned region <NUM> extending relatively between the junction strips (<NUM>, <NUM>). The patterned region <NUM> is bounded by a first end <NUM>, a second end, <NUM>, a first lateral edge <NUM>, and a second lateral edge <NUM>. The patterned region <NUM> may comprise a plurality of holes <NUM> which are keyhole-shaped with rounded edges at the ends of the keyhole. A long dimension of the keyhole-shaped holes is oriented transverse to the overall direction of current flow in the resistive element <NUM>. In this regard, the patterned region <NUM> comprises multiple conductive paths which tend to improve reliability of the resistive element <NUM> by ensuring a break or a plurality of breaks in the patterned region <NUM> of the metallic foil material <NUM> (i.e., portions relatively between the holes <NUM>) will not inhibit current flow across the resistive element <NUM>. The ends (<NUM>, <NUM>) of the patterned region <NUM> may extend through the junction strips (<NUM>, <NUM>) to the edges of the metallic foil material <NUM> and, thereby, the entirety of the metallic foil material may comprise the patterned region <NUM>. As discussed above, the busbar portions may be integral to the resistive elements and the patterned region <NUM> may extend through the busbars of the resistive element <NUM>. In this regard, the busbar portions may be monolithic with the resistive element <NUM>.

With additional reference to <FIG>, a strain field plot <NUM> of the airfoil <NUM> is illustrated. Plot <NUM> shows the aerodynamic surface of airfoil <NUM> broken away, unfolded, and laid flat axially along the leading edge axis <NUM>. Plot <NUM> extends from the leading edge axis <NUM> toward a trailing edge boundary <NUM> of the ice protection system <NUM>. Plot <NUM> is characterized by relatively low strain at the leading edge with strain concentrations building chordwise at the mid-span portion of the wrap toward the trailing edge boundary <NUM>. Portions of the ice protection system <NUM> subjected to the relatively high strain at the corresponding mid-span portion tend to undergo accelerated degradation. For example, wired, bonded, or soldered electrical coupling may tend to suffer accelerated fatigue failures. In this regard, the dual functionality of a busbar portion contiguous with the resistive material is desirable. Ice protection system <NUM> may benefit of increased operational life by reducing a number of electrical couplings in high strain areas by substitution with busbar portions of the electrically resistive material.

With additional reference to <FIG>, an exemplary electrical heating mat <NUM> (e.g., <NUM>, <NUM>) of ice protection system <NUM> is illustrated in schematic block diagram broken away, unfolded, and laid flat axially along the leading edge axis <NUM>. The electrically resistive material of heating mat <NUM> may be etched to define a plurality of spanwise zones <NUM>, chordwise zones <NUM>, and respectively associated busbar portions. Heating mat <NUM> is etched such that each zone is defined by a single coplanar layer of resistive elements. In this regard, heat transfer may be optimized and component weight may be reduced by condensing multiple layers of heating elements to a single layer. Heating mat <NUM> includes a first spanwise zone 602A, a second spanwise zone 602B, a third spanwise zone 602C, and a fourth spanwise zone 602D. Each of the spanwise zones may be relatively inboard of the first chordwise zone 604A. In like regard the second chordwise zone 604B may be outboard of the first chordwise zone 604A and the third chordwise zone 604C may be outboard of the second chordwise zone 604B. Each chordwise zone <NUM> may have a respectively corresponding and contiguous first and/or second busbar portion. For example, first chordwise zone 604A may have a corresponding first busbar portion 604A-<NUM> and a second busbar portion 604A-<NUM>. The second chordwise zone 604B may have a corresponding first busbar portion 604B-<NUM> and second busbar portion 604B-<NUM>. The third chordwise zone 604C may have a corresponding first busbar portion 604C-<NUM> and second busbar portion 604C-<NUM>. The busbar portions may extend along the spanwise axis <NUM> parallel the spanwise portions <NUM> and relatively aft (toward the trailing edge <NUM>) thereof. In this regard, the busbar portions may delimit the chordwise extent along the chordwise axis <NUM> of the spanwise zones <NUM>.

With additional reference to <FIG>, electrical heating mat <NUM> of ice protection system <NUM> is illustrated in schematic block diagram broken away, unfolded, and laid flat axially along the leading edge axis <NUM> includes an anti-ice strip zone <NUM>. Zone <NUM> is etched in a different layer than coplanar layer of the spanwise zones <NUM>, the chordwise zones <NUM>, and the respectively associated busbar portions. In this regard, zone <NUM> is a separate isolated circuit which may be driven by a separate power channel and/or bus (see e.g., second heating mat <NUM> of <FIG>). Zone <NUM> is overlaid across the spanwise zones <NUM> and the chordwise zones <NUM> such that zone <NUM> extends along the leading edge axis <NUM> and coincides with the leading edge <NUM>.

With renewed reference to <FIG>, controller <NUM> may be integrated into computer systems onboard an aircraft, such as, for example, tiltrotor aircraft <NUM>. Controller <NUM> may comprise a processor. Controller <NUM> may be implemented in a single processor. Controller <NUM> may be implemented as and may include one or more processors and/or one or more tangible, non-transitory memories and be capable of implementing logic. Each processor can be a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. Controller <NUM> may comprise a processor configured to implement various logical operations in response to execution of instructions, for example, instructions stored on a non-transitory, tangible, computer-readable medium configured to communicate with controller <NUM>.

System program instructions and/or controller instructions may be loaded onto a non-transitory, tangible computer-readable medium having instructions stored thereon that, in response to execution by a controller, cause the controller to perform various operations. The term "non-transitory" is to be understood to remove only propagating transitory signals per se from the claim scope and does not relinquish rights to all standard computer-readable media that are not only propagating transitory signals per se.

With additional reference to <FIG>, a method <NUM> of de-icing is illustrated. The controller <NUM> may receive an activate command from the control interface <NUM>. Controller <NUM> may pass the activate command to the ice protection logic <NUM>. In response to the activate command, the ice protection logic <NUM> may command a power supply <NUM> to supply power to one or more zones of ice protection system <NUM>. In this regard, controller <NUM> may apply an electrical current to a busbar portion of a heating mat such as heating mat <NUM>. Controller <NUM> may receive an enable command from the control interface <NUM> (step <NUM>). In response to the enable command, controller <NUM> may poll sensors <NUM> for sensor data (step <NUM>). In response to polling sensors <NUM>, controller <NUM> may receive sensor data including an air temperature data and a liquid water content data (step <NUM>). Controller may pass the air temperature data and the liquid water content data to the ice protection logic <NUM> (step <NUM>). The ice protection logic <NUM> may determine, based on the air temperature data and the liquid water content data, an icing condition of the aircraft (step <NUM>). In response to determining the icing condition of the aircraft, the ice protection logic <NUM> may command the power supply <NUM> to supply power to one or more zones of ice protection system <NUM>. In this regard, controller <NUM> may apply an electrical current to a busbar portion of a heating mat such as heating mat <NUM> in response to an icing condition (step <NUM>). The controller <NUM> may apply current to the anti-ice strip zone <NUM> in response to the enable command. In this regard, the anti-ice strip zone <NUM> may be continuously active in response to the enable command and the controller may selectively apply current to the spanwise zones <NUM> and the chordwise zones <NUM> in response to the enable command and determining the icing condition.

It should be noted that many additional functional relationships or physical connections may be present in a practical system. However, the benefits, advantages, solutions to problems, and any elements that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as critical, required, or essential features or elements of the disclosures.

The scope of the disclosures is accordingly to be limited by nothing other than the appended claims, in which reference to an element in the singular is not intended to mean "one and only one" unless explicitly so stated, but rather "one or more. " Moreover, where a phrase similar to "at least one of A, B, or C" is used in the claims, it is intended that the phrase be interpreted to mean that A alone may be present in an embodiment, B alone may be present in an embodiment, C alone may be present in an embodiment, or that any combination of the elements A, Band C may be present in a single embodiment; for example, A and B, A and C, B and C, or A and B and C.

In the detailed description herein, references to "one embodiment", "an embodiment", "an example embodiment", etc., indicate that the embodiment described may include a particular feature, structure, or characteristic, but every embodiment may not necessarily include the particular feature, structure, or characteristic. After reading the description, it will be apparent to one skilled in the relevant art(s) how to implement the disclosure in alternative embodiment falling within the scope of the appended claims.

Claim 1:
An ice protection system (<NUM>) for an airfoil comprising:
an electrical heating mat (<NUM>) comprising an electrically resistive material,
wherein the electrically resistive material is configured to define a first spanwise zone (602A) of the airfoil and a first chordwise zone (604A) of the airfoil,
wherein at least one of the first spanwise zone or the first chordwise zone include a first busbar portion (604A-<NUM>) contiguous with the electrically resistive material, and characterized in that
wherein the electrical heating mat (<NUM>) is etched such that each of the first spanwise zone, the first chordwise zone, and the first busbar portion are coplanar in a first layer of the ice protection system; and
an anti-ice strip zone (<NUM>),
wherein the anti-ice strip zone is etched in a second layer different from the first layer, and
wherein the anti-ice strip zone is overlaid across the first spanwise zone and the first chordwise zone such that the anti-ice strip zone (<NUM>) is configured to extend along a leading edge axis (<NUM>) and
to coincide with a leading edge (<NUM>).