Patent Description:
Modern aircraft rely on angle of attack sensors to provide angle of attack data to aircraft air data systems, or other aircraft consuming systems, which in turn perform flight control, fault detection, and informational functions, among others. In some conventional air data systems, a control algorithm validates angle of attack data by comparing data from two or more redundant sources. Based on the comparison, the control algorithm identifies faulty angle of attack data, isolating faulty data from the air data system. While such air data systems are tolerant of a single angle of attack sensor failure, multiple contemporaneous sensor failures, although unlikely, can result in the isolation of a healthy angle of attack sensor rather than faulty sensor data. Further, angle of attack sensors may include built-in test functionality that detects locked vane conditions, monitors internal vane heaters, and evaluates electrical signal integrity. However, this built-in test functionality is not tailored to detect sensor faults resulting from impact damage or lighting strike damage. Damage detection technology is disclosed in <CIT>, <CIT>, and <CIT> (which is prior art under Article <NUM>(<NUM>) EPC only).

An angle of attack sensor according to the invention is provided as defined by claim <NUM>.

As disclosed herein, an air data system includes additional means for in-situ detection of damage to an angle of attack sensor resulting from an impact event, a lightning strike event, or other physical or electrical damage events that cause comparable damage to the angle of attack sensor. In each of the disclosed embodiments, the air data system includes an electronics module that analyzes a signal output from the angle of attack sensor to detect impact and/or lightning strike events. In each of the disclosed embodiments, the electronics module outputs an indication of an impact event, a lightning strike event and/or other physical or electrical damage event based on a comparison between the signal and damage criterion stored within the electronics module.

In some embodiments the electronics module analyzes one or more time-varying acceleration signals output from a linear accelerometer, a rotational accelerometer (i.e., a gyroscope), a multi-axis accelerometer, or other inertial sensors coupled to the angle of attack vane to detect impact events or other physical damage events that cause comparable damage to the angle of attack sensor. Impact event detection occurs when the peak acceleration amplitude exceeds one or more acceleration limits stored within the electronics module corresponding to a material limit of the angle of attack vane or an interfacing component of the angle of attack vane. Further, peak velocity amplitude or peak displacement amplitude can be computed from the acceleration signal and compared to a velocity limit or a displacement limit of the angle of attack vane or an interfacing component of the angle of attack vane to detect impact events.

In each of the foregoing embodiments, detection of impact and lightning strike events using various embodiments of the electronics module enable damage and/or failure detection of the angle of attack sensor without relying on redundant angle of attack data. Furthermore, impact and lightning damage of the angle of attack sensor can be detected in-situ and without requiring disassembly and physical inspection of the angle of attack sensor, thereby improving safe operation of aircraft.

<FIG> is a perspective view of angle of attack sensor <NUM> that includes rotatable vane <NUM> configured to rotate freely about axis A-A such that vane <NUM> aligns with a direction of an oncoming airflow F. Air data systems utilizes angle of attack sensor <NUM> to determine angle of attack angle α (i.e., an angle between oncoming airflow F or relative wind and a reference line of the aircraft, such as a chord of a wing of the aircraft).

Angle of attack sensor <NUM> further includes mounting plate <NUM> to facilitate installation of angle of attack sensor <NUM> to outer skin <NUM> of an aircraft via fasteners extending through bores 18A, 18B, 18C, 18D, 18E, 18F, <NUM>, and <NUM> that are circumferentially spaced around a periphery of mounting plate <NUM>. Exterior surface <NUM> of mounting plate <NUM> is aligned with and conforms to outer skin <NUM> of the aircraft while bores 18A-H permit fasteners to be recessed from exterior surface <NUM>, forming a smooth and continuous transition between the outer skin <NUM> and mounting plate <NUM>.

Rotatable vane <NUM> extends outward away from vane hub <NUM> to tip <NUM>. Lateral surfaces <NUM> and <NUM> extend in a chordwise direction from leading edge <NUM> to trailing edge face <NUM> and diverge to define a wedge-shaped cross-section of vane <NUM> as shown, or alternatively, lateral surfaces <NUM> and <NUM> can be convex along the chordwise direction to define a contoured cross-section of vane <NUM>. Vane hub <NUM> receives shaft connectors 34A and 34B, which connect vane hub <NUM> to rotatable shaft <NUM> disposed within housing <NUM>. Mounted to rotatable shaft <NUM> and centered on axis A-A, face plate <NUM> defines an interface between rotatable components and stationary components of angle of attack sensor <NUM> and forms circumferentially-extending gap <NUM> between an outer periphery of face plate <NUM> and a bore of mounting plate <NUM>.

Housing <NUM> extends from mounting plate <NUM> towards an interior space of the aircraft and encloses internal components of angle of attack sensor <NUM>. Electrical interface connector <NUM> protrudes from an interior end of housing <NUM> and exchanges data, including angle of attack data, with consuming systems of the aircraft, for example, an air data system.

<FIG> is a cross-sectional view of angle of attack sensor <NUM> taken along line B-B of <FIG> in which some components are shown in detail while other components are depicted schematically. As depicted, mounting plate <NUM> includes tabs <NUM> protruding from an interior side of mounting plate <NUM> and spaced circumferentially about axis A-A. At a radially outer periphery of tabs <NUM> relative to axis A-A, tabs <NUM> interface with housing <NUM>, which extends from an open end enclosed by mounting plate <NUM> to a closed end face. Electrical interface connector <NUM> mounts to to the end face of housing <NUM> opposite mounting plate <NUM>. Together, housing <NUM> and mounting plate <NUM> enclose interior volume <NUM> of angle of attack sensor <NUM>. Rear support <NUM> mounts the end face of housing <NUM> within interior volume <NUM>.

Shaft <NUM><NUM> extends into interior volume <NUM> from vane hub <NUM> and is laterally supported from front bearing <NUM> and rear bearing <NUM>. Bearing <NUM> installs within a bore of front bearing support <NUM>, and bearing <NUM> installs within a bore of rear bearing support <NUM>, each of the front bearing support <NUM> and rear bearing support <NUM> extending into interior volume <NUM> from mounting plate <NUM> and rear support <NUM>, respectively.

Counterweight <NUM> attaches to shaft <NUM> adjacent to front bearing <NUM> and at a position relative to vane <NUM> and vane hub <NUM> that reduces or eliminates the rotational moment about axis A-A due to the weight of vane <NUM> and vane hub <NUM>. To facilitate this attachment, counterweight <NUM> includes a curved mounting surface while clamp <NUM> includes a corresponding curved mounting surface, each curved surface adapted to mate with shaft <NUM>. Fasteners <NUM> extend through clamp <NUM> and into counterweight <NUM> to retain counterweight <NUM> onto shaft <NUM>.

Angle of attack sensor <NUM> includes angular position sensor <NUM>, such as a resolver or encoder, and rotational dampener <NUM>, each mounted within housing <NUM> from interior plate <NUM>. While sensor <NUM> and dampener <NUM> are depicted on opposing sides of shaft <NUM>, sensor <NUM> and dampener <NUM> can be mounted to plate <NUM> with any suitable angular spacing about axis A-A to facilitate coupling to shaft <NUM>. Angular position sensor <NUM> and rotational dampener <NUM> are coupled to shaft via gearing <NUM> or another suitable means. Rotational motion of vane <NUM>, and therefore shaft <NUM>, transmits through gearing <NUM>, or other rotational coupling, to angular position sensor <NUM> while dampener <NUM> reduces rotational oscillations when the angular position of vane <NUM> changes. Angular position sensor <NUM> senses the angular position of vane <NUM> via shaft <NUM> and gearing <NUM>, outputting signal <NUM> indicative of the angular position of vane <NUM> to electronics module <NUM>. For example, signal <NUM> can be a voltage signal variable between an upper voltage limit and a lower voltage limit in proportion to the angular position of vane <NUM>.

One or more additional sensors are included in angle of attack sensor <NUM> including linear accelerometer <NUM>, rotational accelerometer (or gyroscope) <NUM>, and current sensor <NUM>. Linear and rotational accelerometers <NUM> and <NUM> can be discrete sensors mounted at different locations or incorporated into multi-axis accelerometer <NUM> responsive to one or more linear or rotational movements. In each case, one or more accelerometers are coupled to vane <NUM> to detect vane movements and, in particular, impacts to vane <NUM> during operation. For example, one or more linear accelerometers <NUM>, rotational accelerometers <NUM>, and multi-axis accelerometers <NUM> can be imbedded within or mounted to vane <NUM> at any point along its length, or within vane hub <NUM> as shown in <FIG>. As installed, each of one or more accelerometers <NUM>, <NUM>, and <NUM> output corresponding signals <NUM> to electronics module <NUM>, each signal <NUM> indicative of an acceleration of vane <NUM> or vane hub <NUM> in one of six degrees of freedom. Additionally, current sensor <NUM> can be mounted along a ground current path between vane <NUM> and a grounding point for angle of attack sensor <NUM>. For example, current sensor <NUM> can be mounted within interior volume <NUM> and electrically coupled between an outer race of front bearing <NUM> and bearing support <NUM>, or mounting plate <NUM>, since angle of attack sensor <NUM> can be grounded to aircraft outer skin <NUM>. However, any different location could be used so long as the location places current sensor <NUM> along a grounding path of angle of attack sensor <NUM>. In operation, current sensor <NUM> transmits signal <NUM> indicative of a ground current of angle of attack sensor <NUM> to electronics module <NUM>.

Electronics module <NUM> is mounted within housing <NUM>, for example, from interior plate <NUM> or rear support <NUM>. Electronics module 72A contains at least the components related to damage detection discussed below and may also include other components necessary or desired for incorporation of electronics module 72A into an air data system remote from angle of attack sensor <NUM>. In either circumstance, electronics module <NUM> or 72A includes processor <NUM>, computer-readable memory <NUM>, and communication device <NUM> and receives one or more of position signal <NUM>, accelerometer signal <NUM>, and current signal <NUM>.

Examples of processor <NUM> can include any one or more of a microprocessor, a controller, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other equivalent discrete or integrated logic circuitry.

Computer-readable memory <NUM> can be configured to store information within electronics module <NUM> during operation. Computer-readable memory <NUM>, in some examples, is described as a computer-readable storage medium. In certain examples, a computer-readable storage medium can include a non-transitory medium. The term "non-transitory" can indicate that the storage medium is not embodied in a carrier wave or a propagated signal. In some examples, a non-transitory storage medium can store data that can, over time, change (e.g., in RAM or cache). Computer-readable memory <NUM> can include volatile memory, non-volatile memory, or both. Examples of volatile memories can include random access memories (RAM), dynamic random access memories (DRAM), static random access memories (SRAM), and other forms of volatile memories. Examples of non-volatile memories can include flash memories, forms of electrically programmable memories (EPROM) or electrically erasable and programmable (EEPROM) memories, magnetic hard discs, optical discs, floppy discs, or other forms of non-volatile memories.

Communication device <NUM> can be network interface cards (or other interface devices) configured to send and receive data over a communications network and/or data bus according to one or more communications protocols, such as the ARINC <NUM> communication protocol, CAN bus communication protocol, MII,-STD-<NUM> communication protocol, or other communication protocol.

Computer-readable memory <NUM> is encoded with instructions, that when executed by processor <NUM>, cause the electronics module <NUM> to receive one or more of signals <NUM>, <NUM>, and <NUM> from angular position sensor <NUM>, linear accelerometer <NUM>, rotational accelerometer <NUM>, multi-axis accelerometer <NUM>, and current sensor <NUM> as well as perform one or more steps of a damage detection method, which can incorporate one or more of the following algorithms discussed below.

<FIG> is a diagram of angle of attack sensor <NUM> in a space oriented reference frame in which the horizontal and vertical directions are represented by corresponding axes. As depicted, centerline <NUM> of angle of attack sensor <NUM> is aligned with reference line <NUM> of an aircraft (e.g., a chord line of an aircraft wing). Aircraft pitch angle θ<NUM> is the angle between aircraft reference line <NUM> and horizontal datum <NUM>. Vane angle θ<NUM> is the angle between vane chord vector <NUM> and horizontal datum <NUM> while air flow angle θ<NUM> is the angle between oncoming airflow F and horizontal datum <NUM>. Position signal <NUM> output by angular position sensor <NUM>, or angle of attack α, is indicative of the difference between aircraft pitch angle θ<NUM> and vane angle θ<NUM>.

<FIG> describes the kinematic model of angle of attack sensor <NUM>. Aircraft pitch angle θ<NUM>, vane angle θ<NUM>, air flow angle θ<NUM>, and angle of attack α are the angles defined in <FIG>. Damping constant b is based on rotational dampener <NUM> as well as dynamic friction within angle of attack sensor <NUM>, including from bearings <NUM> and <NUM>. The rotational components of angle of attack sensor <NUM> (i.e., shaft <NUM>, bearings <NUM> and <NUM>, hub <NUM>, vane <NUM> and face plate <NUM>) have rotational moment of inertia J about axis A-A. Aerodynamic spring constant k is proportional to aerodynamic forces imposed on vane <NUM> and the difference between vane angle θ<NUM> and air flow angle θ<NUM>. Under normal operation, the motion of angle of attack sensor <NUM> is described by equation <NUM>, where k(θ<NUM> - θ<NUM>) is the torque imposed on vane <NUM> by aerodynamic forces, b(θ̇<NUM> - θ̇<NUM>) is the torque imposed on vane <NUM> primarily by dampener <NUM> as well as other damping forces within angle of attack sensor <NUM>, and Jθ̈<NUM> is the net torque imposed on vane <NUM>. Quantities θ̇<NUM> and θ̇<NUM> correspond to rate of change of aircraft pitch angle θ<NUM> and vane angle θ<NUM>, respectively, and quantity θ̈<NUM> corresponds to angular acceleration of vane angle θ<NUM>.

During some damage events, an impact to angle of attack sensor <NUM> can partially or completely detach vane <NUM> from angle of attack sensor <NUM>, causing a moment imbalance about axis A-A. As a result of the moment imbalance and the reduced aerodynamic force on the vane, counterweight <NUM> and shaft <NUM> rotate about axis A-A until counterweight <NUM> aligns with a direction of gravity. A representative vane shear event is illustrated by <FIG> depicts vane <NUM> and counterweight <NUM> of angle of attack sensor <NUM> during normal operation. Following a vane shear event, counterweight <NUM> rotates from an initial position represented by dashed lines to a position aligned with a direction of gravity as depicted in <FIG>.

After a vane shearing event, the motion of angle of attack sensor <NUM> is described by equation <NUM>, which additionally includes torque imposed on vane <NUM> due to counterweight <NUM> and torque imposed on vane <NUM> due to a change in angle of attack α. The counterweight torque is the product of the counterweight moment arm, L, about axis A-A, the counterweight mass, m, normal load factor, Nz, gravitational constant, g, and the cosine of vane angle θ<NUM>. The torque on vane <NUM> due to a change in angle of attack α is the product of a signum function and a natural exponential function. Equation <NUM> is expressed as follows, in which Tc is the dynamic friction torque constant, Ts is the static friction torque constant, and β is a parameter that determines when the model transitions from static friction to dynamic friction, or vice versa.

<FIG> depicts an exemplary output from angle of attack sensor <NUM> during a vane shear event. The calculated output signal, α cal(t), is a function of time and is determined based on equation <NUM>, physical parameters of angle of attack sensor <NUM>, and initial angle conditions at time step t<NUM>. The physical parameters of angle of attack sensor <NUM> can include counterweight moment arm L, counterweight mass m, normal load factor Nz, dynamic friction constant Tc, static friction torque constant Ts, damping coefficient b, aerodynamic spring constant k, and rotational moment of inertia J while initial angle conditions can include one or more of angle of attack α <NUM>, pitch angle θ<NUM>, vane angle θ<NUM>, and air flow angle θ<NUM>. Also depicted by <FIG> is time-varying position signal <NUM> output by angular position sensor <NUM> and stored on computer readable memory <NUM> of electronics module <NUM>.

Electronics module <NUM> can be encoded with instructions that enable execution of damage detection method <NUM>, which can detect physical damage, electrical damage, or both physical and electrical damage. As shown in <FIG> and <FIG>, damage detection method <NUM> can include one or any combination of vane shear detection algorithm <NUM>, impact detection algorithm <NUM>, and lightning strike detection algorithm <NUM>, each of algorithms <NUM>, <NUM>, and <NUM> measuring a kinematic or electric parameter of the angle of attack sensor and comparing the parameter to a damage criterion. For instance, vane shear detection algorithm <NUM> compares position signal <NUM> output from angular position sensor <NUM> to a characteristic position signal response of a vane shear event whereby a portion or the entirety of vane <NUM>, or vane hub <NUM> separates from angle of attack sensor <NUM>. Impact detection algorithm <NUM> compares one or more accelerometer signals <NUM> to a limit and thereby detecting an impact event to angle of attack sensor <NUM>. Similarly, lightning strike algorithm <NUM> compares current signals <NUM> to corresponding limits to detect a lightning strike to angle of attack sensor <NUM>.

Embodiments of electronics module <NUM> implementing vane shear detection algorithm <NUM> can include counterweight offset <NUM> and offset tolerance <NUM> stored into computer-readable memory <NUM> prior to installation onto an aircraft. Counterweight offset <NUM> corresponds to an angular position of counterweight <NUM> in which a center of gravity of counterweight <NUM> aligns with a direction of gravity. Offset tolerance <NUM> can be expressed as a positive deviation from counterweight offset <NUM>, a negative deviation from counterweight offset <NUM>, or a deviation range bracketing counterweight offset <NUM>. For example, offset tolerance <NUM> a can be expressed as a range equal to +/- <NUM>% of counterweight offset <NUM>. However, in other embodiments, offset tolerance <NUM> can be +/- <NUM>% or a greater tolerance depending on desired sensitivity.

Alternatively, or in addition to counterweight offset <NUM> and tolerance <NUM>, electronics module <NUM> may store reference time constant <NUM> and time constant tolerance <NUM> describing a characteristic transient response of angular position sensor output during a vane shear event. Time constant <NUM> is determined from equation <NUM> and varies based on the system parameters contained therein, and tolerance <NUM>, like offset tolerance <NUM>, can be expressed as a positive or negative deviation from time constant <NUM>, or a deviation range bracketing time constant <NUM>. For example, time tolerance <NUM> can be equal to +/- <NUM>% of time constant <NUM>, +/- <NUM>% of time constant <NUM>, or a greater tolerance depending on desired sensitivity.

Further, electronics module <NUM> can store one or more physical parameters of angle of attack sensor <NUM> and tolerance band <NUM>. As described in reference to equation <NUM> and <FIG> above, physical parameters of angle of attack sensor <NUM> can include counterweight moment arm L, counterweight mass m, normal load factor Nz, dynamic friction constant Tc, static friction torque constant Ts, damping coefficient b, aerodynamic spring constant k, and rotational moment of inertia J. Each physical parameter depends on the physical characteristics of a specific angle of attack sensor and can be determined through calculation, computer-modeling of angle of attack sensor <NUM>, empirical testing of angle of attack sensor <NUM>, or a combination of one or more of these methods. Tolerance band <NUM> defines upper and lower limits relative to an expected response from position signal <NUM> after a vane shear event, for example, calculated output signal, αcal(t). Tolerance band <NUM> can be determined based on equation <NUM>, offsetting calculated output signal, αcal(t), such that calculated output signal, αcal(t), falls within tolerance band <NUM>. The upper and lower limits of tolerance band <NUM> can be offset by an amount equal to +/- <NUM>% of calculated output signal, αcal(t), αcal(t), +/- <NUM>% of calculated output signal, αcal(t), or a greater tolerance depending on desired sensitivity. The offset of tolerance band <NUM> can be constant over the time range of calculated output signal, αcal(t), or can vary as a function of time, magnitude of calculated output signal, αcal(t), rate of change of output signal, αcal(t), or a combination of one or more of these parameters.

In a first routine of vane shear detection algorithm <NUM> shown in <FIG>, algorithm <NUM> includes steps <NUM>, <NUM>, <NUM> and <NUM>. In step <NUM>, electronics module <NUM> receives time-varying position signal <NUM> from angular position sensor <NUM>. Subsequently, electronics module <NUM> receives aircraft pitch angle θ<NUM> from an aircraft air data system (e.g., an air data computer) in step <NUM>. Step <NUM> follows in which the summation of position signal <NUM> at a given time and aircraft pitch angle θ<NUM> is compared to counterweight offset <NUM>. If the summation of position signal <NUM> and aircraft pitch angle θ<NUM> differs from counterweight offset <NUM> by more than offset tolerance <NUM>, steps <NUM>, <NUM>, and <NUM> are repeated. If, however, the summation of position signal <NUM> and aircraft pitch angle θ<NUM> differs by offset tolerance <NUM> or less, electronics module <NUM> outputs, in step <NUM>, a fault signal indicating a vane shear event using communication device <NUM>.

In a second routine of vane shear detection algorithm <NUM>, algorithm <NUM> includes steps <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In step <NUM>, electronics module <NUM> receives time-varying position signal <NUM> from angular position sensor <NUM>. In step <NUM>, electronics module <NUM> extracts first position value <NUM> from position signal <NUM> at a first time step and, in step <NUM>, extracts second position value <NUM> at a second time step. Subsequently, electronics module <NUM> calculates time constant <NUM> based on first position value <NUM>, second position value <NUM>, the elapsed time between the first and second time steps, and other known system parameters from equation <NUM> in step <NUM>. In step <NUM>, time constant <NUM> is compared to reference time constant <NUM>. If time constant <NUM> differs from reference time constant <NUM> by more than tolerance <NUM>, steps <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> are repeated. Alternatively, if time constant <NUM> differs from reference time constant <NUM> by tolerance <NUM> or less, electronics module <NUM> outputs to an aircraft receiving system, using communication device <NUM>, a fault signal indicating a vane shear event in step <NUM>.

In a third routine of vane shear detection algorithm <NUM>, algorithm <NUM> includes steps <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>. In step <NUM>, electronics module <NUM> receives time-varying position signal <NUM> from angular position sensor <NUM> and, in step <NUM>, stores position signal <NUM> between a first time step and a second time step. The duration of time between the first and second time steps is selected based on equation <NUM> or, in other words, an expected response of signal <NUM> after a vane shear event (e.g., calculated output signal, αcal(t)). In step <NUM>, electronics module <NUM> determines calculated output signal αcal(t) and determines upper and lower limits of tolerance band <NUM>, each based on stored physical parameters of angle of attack sensor <NUM> and initial conditions stored at first time step of position signal <NUM>. Thereafter in step <NUM>, electronics module <NUM> compares stored position signal <NUM> to calculated output signal αcal(t) at one or more time increments between the first and second time steps. If stored position signal <NUM> is not between upper and lower limits of tolerance band <NUM>, steps <NUM>, <NUM>, <NUM>, and <NUM> repeat. If stored position signal <NUM> is between upper and lower limits of tolerance band <NUM>, electronics module <NUM> outputs to an aircraft receiving system, using communication device <NUM>, a fault signal indicating a vane shear event in step <NUM>.

Embodiments of electronics module <NUM> implementing impact detection algorithm <NUM> include one or more acceleration limits <NUM> stored into computer-readable memory <NUM> prior to installation onto an aircraft. Acceleration limits <NUM> can be determined through calculation, computer-modeling of angle of attack sensor <NUM>, empirical testing of angle of attack sensor <NUM>, or a combination of one or more of these methods. Each acceleration limit <NUM> correlates to calculated or measured acceleration amplitude at a particular accelerometer location produced by a known force or torque applied to vane <NUM> that results in physical damage to vane <NUM>, vane hub <NUM>, shaft <NUM>, front bearing <NUM>, or rear bearing <NUM>.

Impact detection algorithm <NUM> includes steps <NUM>, <NUM>, <NUM>, and <NUM> as depicted in <FIG>. In step <NUM> of impact detection algorithm <NUM>, electronics module <NUM> receives one or more time-varying accelerometer signals <NUM> from one or more linear accelerometers <NUM>, rotational accelerometers <NUM>, and multi-axis accelerometer <NUM> during operation of angle of attack sensor <NUM>. Next, electronics module <NUM> extracts and stores peak acceleration amplitudes <NUM> from each of one or more accelerometer signals <NUM> in step <NUM>. In step <NUM>, each peak acceleration amplitude <NUM> is compared to a corresponding acceleration limit <NUM>. If peak acceleration amplitude <NUM> is less than acceleration limit <NUM>, steps <NUM>, <NUM>, and <NUM> of impact detection algorithm <NUM> repeat. However, if peak acceleration amplitude <NUM> is greater than or equal to acceleration limit <NUM>, electronics module <NUM> outputs fault signal <NUM> to a receiving system of the aircraft (i.e., an air data system) indicating impact damage to angle of attack sensor <NUM>.

Optionally, impact detection algorithm <NUM> can include step <NUM> for comparing one or more acceleration signals <NUM> to corresponding acceleration thresholds <NUM>. Like acceleration limits <NUM>, one or more acceleration thresholds <NUM> can be determined through calculation, computer-modeling of angle of attack sensor <NUM>, empirical testing of angle of attack sensor <NUM>, or a combination of one or more of these methods. Each acceleration threshold <NUM> correlates to calculated or measured acceleration amplitude at a particular accelerometer location produced by a known force or torque applied to vane <NUM> that produces accelerated wear of angle of attack sensor components or lessor physical damage to vane <NUM>, vane hub <NUM>, shaft <NUM>, front bearing <NUM>, or rear bearing <NUM> relative to physical damage produced at acceleration limit <NUM>. Accordingly, the magnitude of acceleration thresholds <NUM> is less than corresponding acceleration limits <NUM> for a particular accelerometer location.

After electronics module <NUM> receives one or more time-varying accelerometer signals <NUM> in step <NUM> and stores peak acceleration amplitudes <NUM> in step <NUM>, electronic module <NUM> compares peak acceleration amplitudes <NUM> to corresponding acceleration limits <NUM> and thresholds <NUM> in step <NUM> instead of step <NUM>. If peak acceleration amplitude <NUM> is less than acceleration limit <NUM> and acceleration threshold <NUM>, steps <NUM>, <NUM>, and <NUM> of impact detection algorithm <NUM> repeat. However, if peak acceleration amplitude <NUM> is less than acceleration limit <NUM> and greater than or equal to acceleration threshold <NUM>, electronics module <NUM> outputs fault signal <NUM> to a receiving system of the aircraft (i.e., an air data system) using communication device <NUM> in step <NUM>. Fault signal <NUM> indicates that inspection, output verification, or a combination of both inspection and output verification is required for angle of attack sensor <NUM>. When peak acceleration amplitude <NUM> is greater than acceleration limit <NUM>, electronics module <NUM> outputs fault signal <NUM> to a receiving system of the aircraft (i.e., an air data system) using communication device <NUM> in step <NUM>.

Embodiments of electronics module <NUM> implementing lightning strike detection algorithm <NUM> will include one or more current limits <NUM> stored into computer-readable memory <NUM> prior to installation onto an aircraft. Current limits <NUM> can be determine through calculation, computer-modeling of angle of attack sensor <NUM>, empirical testing of angle of attack sensor <NUM>, or a combination of one or more of these methods. Each current limit <NUM> correlates to calculated or measured current at a particular current sensor location produced during a lightning strike that results in physical or electrical damage to vane <NUM>, vane hub <NUM>, shaft <NUM>, front bearing <NUM>, rear bearing <NUM>, angular position sensor <NUM>, or electronics module <NUM>.

<FIG> outlines lightning strike detection algorithm <NUM>, which includes steps <NUM>, <NUM>, and <NUM>, and <NUM>. In step <NUM> of lightning strike detection algorithm <NUM>, electronics module <NUM> receives one or more time-varying current signals <NUM> from corresponding one or more current sensors <NUM> during operation of angle of attack sensor <NUM>. Next, electronics module <NUM> extracts and stores one or more peak current amplitudes <NUM> from corresponding sensors <NUM> in step <NUM>. In step <NUM>, electronics module <NUM> compares each peak current amplitude <NUM> to corresponding current limits <NUM>. If peak current amplitude <NUM> is less than current limit <NUM>, steps <NUM>, <NUM>, and <NUM> of lightning strike detection algorithm <NUM> repeat. However, if peak current amplitude <NUM> is greater than or equal to current limit <NUM>, electronics module <NUM> outputs fault signal <NUM> to a receiving system of the aircraft (i.e., an air data system) indicating a lightning strike to angle of attack sensor <NUM>.

While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention, which is defined by the appended claims.

Claim 1:
An angle of attack sensor comprising:
a mounting plate (<NUM>);
a vane (<NUM>) supported from the mounting plate and extending from a first side of the mounting plate, wherein the vane is rotatable about a vane axis;
a housing (<NUM>) extending from a second side of the mounting plate in a direction opposite to the vane;
a sensor (<NUM>) coupled to the vane, wherein the sensor is an accelerometer; and
an electronics module (<NUM>) mounted within the housing, the electronics module comprising:
at least one processor (<NUM>);
a communication device (<NUM>); and
computer-readable memory (<NUM>), encoded with instructions that, when executed by the at least one processor, cause the electronics module to:
receive, from the sensor, a signal indicative of one of a linear acceleration of the vane and a rotational acceleration of the vane;
compare the signal to a first damage criterion, wherein the first damage criterion includes an acceleration limit corresponding to a material limit of the vane;
compare the signal to a second damage criterion, wherein the second damage criterion includes an acceleration threshold less than the acceleration limit; and
output, using the communication device, a first fault signal to a consuming system of an aircraft that is indicative of a damage event after determining an amplitude of the signal is equal to or greater than the first acceleration limit; and output a second fault signal to the consuming system that is indicative of a second damage event after determining the signal amplitude is less than the acceleration limit and greater than or equal to the acceleration threshold.