Patent Description:
Almost all aircraft have exterior aircraft lights. In particular, large passenger air planes are equipped with a wide variety of exterior aircraft lights. Examples of such exterior aircraft lights include take-off and/or landing lights, taxi lights, navigation lights and anti-collision lights.

The term "anti-collision light" is a generic term, which encompasses white flashing strobe lights, typically mounted at the wing tips and the tail of an aircraft, and red flashing aircraft beacon lights, usually mounted above and below the fuselage of an aircraft.

Aircraft beacon lights typically comprise a large number of light sources aiming in different directions for generating a circumferential light distribution. Any failure of light sources leaves a gap in the circumferential light distribution emitted by the aircraft beacon light. As a result, the aircraft beacon light may no longer comply with aircraft safety regulations. The emission characteristics of red LEDs, which are often employed as light sources in aircraft beacon lights, are highly dependent on ambient temperatures and aging. Thus, it is desirable to closely monitor the light emission of the light sources of aircraft beacon lights.

Further, the outer light transmissive cover of aircraft beacon lights is susceptible to erosion. Erosion of the light transmissive cover may spread / diffuse the light to such an extent that minimum light intensities, as required by aircraft safety regulations, are no longer achieved. Thus, it is desirable to also monitor the erosion of the light transmissive cover of an aircraft beacon light.

<CIT> discloses a recognition light including a reflector having an axis and first and second annular semi-parabolic reflective surfaces which have respective focal points axially spaced apart from one another, and first and second annular lamps respectively disposed at the focal points. A cover surrounds the reflector and lamps and includes a lens for focusing the light along a plane perpendicular to the axis of the reflector, the lens including first and second Fresnel lens portions each including a convex lens and a prism lens, the convex lenses being disposed adjacent one another and transaxially aligned with the first and second lamps, respectively. A light detector detects light emitted from at least one of the lamps, a monitor circuit provides a fail signal when a characteristic of the light output of at least one of the lamps does not satisfy a specified criteria, and a control circuit first activates the first lamp and then the second lamp in response to receipt of the fail signal of the monitor circuit.

According to <CIT> a combined aircraft navigation and anti-collision light, includes: at least one navigation light source; a navigation light sensor, in operation outputting a light detection signal corresponding to an amount of light detected by the navigation light sensor; a first optical system, associated with the at least one navigation light source, wherein the first optical system is configured for shaping a navigation light output from light emitted by the at least one navigation light source and is configured for directing stray light from the at least one navigation light source to the navigation light sensor; at least one anti-collision light source; a second optical system, associated with the at least one anti-collision light source and configured for shaping an anti-collision light output from light emitted by the at least one anti-collision light source; a lens cover, arranged over the at least one navigation light source, the first optical system, the at least one anti-collision light source, and the second optical system for passing the navigation light output and the anti-collision light output therethrough, wherein the navigation light sensor is arranged with respect to the lens cover to detect light emitted by the at least one anti-collision light source and diffusely reflected by the lens cover; and a controller, coupled to the navigation light sensor and configured to determine a state of erosion of the lens cover from a pulsed signal component of the light detection signal.

<CIT> discloses a light signalling device including multiple light units e.g. light emitting diodes, mounted on a support and surrounded by a translucent cover. The cover reflects the light emitted by the units and is disposed near the units. A photometric sensor is positioned between the support and the cover. A comparison unit compares a light intensity detected by the sensor with a reference light intensity.

Accordingly, it would be beneficial to provide an aircraft beacon light and a method of determining a health status of an aircraft beacon light, which allow for reliably monitoring the operation of an aircraft beacon light.

Exemplary embodiments of the invention include an aircraft beacon light comprising an annular arrangement of light sources which are configured for repeatedly emitting beacon light flashes; a light detection sensor surrounded by the annular arrangement of light sources; and at least one reflective portion arranged for reflecting light emitted by the annular arrangement of light sources onto the light sensor.

Exemplary embodiments of the invention further include a method of determining a health status of an aircraft beacon light, wherein the aircraft beacon light comprises an annular arrangement of light sources and a light detection sensor surrounded by the annular arrangement of light sources, and wherein the method includes: repeatedly emitting beacon light flashes from the annular arrangement of light sources; generating sensor measurement outputs with the light detection sensor, the sensor measurement outputs being indicative of light emitted by the annular arrangement of light sources and reflected onto the light detection sensor by at least one reflective portion; and determining a health status of the aircraft beacon light from the sensor measurement outputs.

In an aircraft beacon light according to an exemplary embodiment of the invention and in a method according to an exemplary embodiment of the invention, a single light detection sensor may suffice for monitoring the operation of all light sources and the erosion of the light transmissive cover. Since only a single light detection sensor is employed for monitoring the operation of a large number of light sources, as are usually employed in an aircraft beacon light, an aircraft beacon light according to an exemplary embodiment of the invention may be provided at comparatively low costs. According to other approaches, which rely on a plurality of light sensors for detecting light emitted by the plurality of light sources in different spatial directions and light reflected by different eroded portions of the outer cover of an aircraft beacon light, the monitoring of the aircraft beacon light may be achieved at reduced complexity and cost.

According to an embodiment, the aircraft beacon light further comprises a light transmissive cover, covering and protecting the annular arrangement of light sources and the light detection sensor.

According to an embodiment, a cavity is formed between the light transmissive cover and the outer periphery of the aircraft, and the light sources and the light detection sensor are arranged within said cavity.

According to an embodiment, the at least one reflective portion is a separate component, i.e. a component which is provided separately from the light transmissive cover, and the at least one reflective portion is arranged within the cavity defined by the light transmissive cover and the outer periphery of the aircraft. The separate component forming the at least one reflective portion may be supported by the light transmissive cover and/or it may be supported by an additional support structure provided within the cavity.

According to an embodiment, the at least one reflective portion is supported by the light transmissive cover. In such a configuration, no additional support structure needs to be provided.

According to an embodiment that is not covered by the claims, the at least one reflective portion is formed integrally with the light transmissive cover. By integrating the at least one reflective portion with the light transmissive cover, the number of components and, thus, the cost for manufacturing the aircraft beacon light may be kept particularly low.

According to an embodiment, the at least one reflective portion comprises a reflective paint or coating, in particular a diffusely reflective paint or coating. The at least one reflective portion or part of the at least one reflective portion may be formed by said reflective paint or coating. The reflective paint or coating may in particular be applied to at least a portion of the light transmissive cover. Using a reflective paint or coating for forming at least part of the at least one reflective portion may provide for a comparably simple and cost efficient way of implementing a reflective portion. The diffusely reflective paint or coating may for example be a white paint or coating.

According to an embodiment, the at least one reflective portion includes a specular reflecting portion and/or a diffusely reflecting portion. Depending on the specific implementation of the aircraft beacon light, specular reflection or diffuse reflection may be beneficial for achieving an optimized trade-off between quality of evaluation results and complexity of implementation.

According to an embodiment, the at least one reflective portion includes a substantially planar portion. Additionally or alternatively, the at least one reflective portion may include a curved portion, in particular a curved portion having an ellipsoidal shape.

Depending on the geometry of the aircraft beacon light, in particular the shape of the light transmissive cover, the at least one reflective portion may comprise at least one planar portion or at least one curved portion, or a combination thereof, in order to provide reflection properties that are beneficial for achieving reliable evaluation results.

For enhancing the operating conditions of the light detection sensor, the light detection sensor and at least one of the light sources may be arranged in such a way that a portion of the light, emitted by the at least one light source, is focused at the position the light detection sensor.

According to an embodiment, the light sources are arranged in a circular or ellipsoidal configuration, allowing the light sources to emit light in all spatial directions, i.e. into a set of directions which, when projected onto a horizontal plane, completely surround the aircraft beacon light. In other words, the light sources may be arranged to provide a <NUM>° light output around the aircraft beacon light.

According to an embodiment, the light sources are arranged in a rectangular, hexagonal or octagonal configuration, allowing the light sources to emit light in four, six or eight spatial sectors, extending along four, six or eight spatial directions, respectively. The opening angles of the spatial sectors may be set so that the spatial sectors, in combination, cover all spatial directions; i.e. the combination of all spatial sectors, when projected onto a horizontal plane, may cover a full circle of <NUM>° around the aircraft beacon light, so that light is emitted in all spatial directions. Configurations emitting light in different numbers of spatial sectors are possible as well.

According to an embodiment, the annular arrangement of light sources comprises at least two subsets of light sources. Each subset comprises at least one light source, respectively, and the light sources of different subsets are switchable independently of each other.

According to an embodiment, the aircraft beacon light comprises a controller, which is configured for selecting one subset of light sources after the other from the at least two subsets of light sources and modifying the length of at least one of the beacon light flashes emitted by the selected subset of light sources and/or modifying the lengths of the beacon light flashes emitted by the non-selected subset(s) of light sources, so that the length of the at least one beacon light flash emitted by the selected subset of light sources exceeds the lengths of the beacon light flashes emitted by the non-selected subset(s) of light sources by a predetermined extension time period and only the selected subset of light sources is active during the predetermined extension time period.

The controller is further configured for evaluating sensor measurement outputs, which are provided by the light detection sensor during the predetermined extension time periods, for determining a health status of the aircraft beacon light.

According to an embodiment, the annular arrangement of light sources comprises at least two subsets of light sources, each subset comprising at least one light source, respectively, and the method of determining a health status of an aircraft beacon light comprises: selecting one subset of light sources after the other from the at least two subsets of light sources and modifying the length of at least one of the beacon light flashes emitted by the selected subset of light sources and/or modifying the lengths of the beacon light flashes emitted by the non-selected subset(s) of light sources, so that the length of the at least one beacon light flash emitted by the selected subset of light sources exceeds the lengths of the beacon light flashes emitted by the non-selected subset(s) of light sources by a predetermined extension time period and only the the selected subset of light sources is active during the predetermined extension time period. The method further comprises evaluating the sensor measurement outputs of the light detection sensor during the predetermined extension time periods for determining the health status of the aircraft beacon light.

Modifying the length of at least one of the beacon light flashes may include extending the length of at least one of the light flashes emitted by the light source(s) of the selected subset and/or shortening the lengths of the beacon light flashes emitted by the light source(s) of the non-selected subset(s).

Such an aircraft beacon light and such a method of determining a health status of an aircraft beacon light may allow for individually evaluating the sensor measurement outputs corresponding to light which is emitted by the different subsets of light sources with only a single light detection sensor. An aircraft beacon light and a method according to exemplary embodiments of the invention may in particular allows for individually determining aging of the light sources of the different subsets of light sources and/or for individually evaluating light which is emitted by different subsets of light sources and reflected by different portions of the light transmissive cover. In consequence, erosion of different portions of the light transmissive cover may be individually determined at low costs, since only a single light detection sensor may be employed.

The selecting of one subset of light sources after the other may be carried out in a cyclic manner and may result in multiple sensor measurement outputs per subset. In this way, a broader data basis and a highly reliable determining of the health status may be achieved. It is also possible that every subset is evaluated only once during a particular health status determining operation.

The subsets of light sources may comprise one light source or a plurality of light sources, respectively. In this way, an individual evaluation of light sources of a group-wise evaluation of light sources may be carried out. Depending on the aircraft beacon light involved, the desired evaluation complexity, and the desired length of the health status determining operation, the number of light sources per subset may be set.

According to an embodiment, determining the health status of the aircraft beacon light includes detecting erosion of the light transmissive cover and/or detecting aging of the light sources. In particular, the determining of the health status of the aircraft beacon light may include distinguishing between erosion of the light transmissive cover and aging of the light sources. Distinguishing between erosion of the light transmissive cover and aging of the light sources may be beneficial for maintenance as it allows for determining in advance, i.e. without a mechanic inspection of the aircraft beacon light, whether light sources and/or the light transmissive cover need to be replaced. As a result, the parts necessary for replacement may be delivered in advance to the site of maintenance and the time needed for maintenance may be reduced.

According to an embodiment, the light sources of the at least two subsets of light sources are configured for providing light emission in different spatial directions.

According to an embodiment, the at least two subsets of light sources include a first subset of light sources, which is configured for providing forward light emission, and a second subset of light sources, which is configured for providing non-forward light emission. The second subset of light sources may in particular be configured for providing rearward light emission.

According to an embodiment, the at least two subsets of light sources further include at least one further subset of light sources, providing lateral light emission.

Providing different subsets of light sources, which are configured for providing light emission in different spatial directions, may allow for individually evaluating the light emitted in the different spatial directions. It may further allow for individually evaluating different portions of the light transmissive cover, passing the light emitted in the different spatial directions, respectively. It may in particular allow for individually evaluating a front portion of the light transmissive cover, passing the light of the forward light emission, which usually is more prone to erosion than the lateral and rear portions of the light transmissive cover, passing the light of the non-forward light emissions.

According to an embodiment, evaluating the sensor measurement outputs includes comparing the sensor measurement outputs caused by light emitted by the at least two different subsets of light sources with each other. Since erosion predominantly occurs at the front side of the light transmissive cover, facing into the direction of flight, comparing the sensor measurement outputs caused by light emitted by a subset of light sources, which is configured for providing forward light emission, with sensor measurement outputs caused by light emitted by at least one subset of light sources, which is configured for providing non-forward light emission, may allow for determining erosion of the light transmissive cover.

According to an embodiment, evaluating the sensor measurement outputs includes storing the sensor measurement outputs in a memory and evaluating a change of the sensor measurement outputs over time.

Evaluating a change of the sensor measurement outputs over time may allow for detecting erosion of the light transmissive cover and/or detecting aging of the light sources from a gradual change of the sensor measurement outputs provided by the light detection sensor over time. In particular, a slow increase of the sensor measurement outputs detected when the forward oriented light sources are activated may be a clear indication for erosion. A gradual decrease of the sensor measurement outputs, in particular a gradual decrease of the sensor measurement outputs associated with multiple of all of the subsets, may be a good indication for aging of the light sources.

According to an embodiment, each beacon light flash has a length of between <NUM> and <NUM>, in particular a length of between <NUM> and <NUM>. According to an embodiment, the predetermined extension time period has a length of between <NUM> and <NUM>, in particular a length of between <NUM> and <NUM>. Such time frames are in agreement with aircraft safety regulations and may allow for reliably evaluating the light detection sensor output caused by light emitted by the light sources of a single subset of light sources during the additional extension time period.

According to an embodiment, the aircraft beacon light includes at least two switchable bypass circuits, each switchable bypass circuit allowing for individually bypassing one of the at least two subsets of light sources, respectively. An aircraft beacon light including switchable bypass circuits may allow for individually adjusting the lengths of the light flashes, emitted by the different subsets of light sources, without modifying the external power supply controlling the operation of the aircraft beacon light. In consequence, an aircraft beacon light comprising multiple switchable bypass circuits, which allow for individually and selectively bypassing the subsets of light sources, may be connected to a conventional aircraft beacon power supply. This may allow for an easy and convenient replacement of a conventional aircraft beacon light by an aircraft beacon light according to an exemplary embodiment of the invention.

According to an embodiment, the light sources are configured for emitting red light, in particular aviation red light, as it is usually emitted by aircraft beacon lights. Alternatively or additionally, the light transmissive cover may be transmissive for red light only, e.g. the light transmissive cover may be a red light filter. It may also be said that the aircraft beacon light is configured to emit red beacon light flashes, in particular aviation red beacon light flashes, in operation.

According to an embodiment, the light sources are or include LEDs. LEDs provide efficient and reliable light sources at comparatively low costs.

According to an embodiment, the method of determining a health status of an aircraft beacon light includes detecting an intensity of ambient light and evaluating the sensor measurement outputs only when the detected intensity of ambient light does not exceed a predetermined threshold.

Evaluating the sensor measurement outputs only when the detected intensity of ambient light does not exceed a predetermined threshold prevents the evaluation results from being affected by ambient light, such as bright daylight, thereby enhancing the quality and reliability of the evaluation results.

According to an embodiment, the light detection sensor is configured for detecting an intensity of ambient light and the controller is configured for evaluating the sensor measurement outputs only when the detected intensity of ambient light does not exceed a predetermined threshold.

According to an embodiment, the aircraft beacon light comprises a separate ambient light sensor for detecting an intensity of ambient light and the controller is configured for evaluating the sensor measurement outputs only when the detected intensity of ambient light does not exceed a predetermined threshold. Such a configuration may enhance the quality and reliability of the evaluation results, as it prevents the evaluation results from being affected by ambient light. A separate ambient light sensor may be arranged at a different position than the light detection sensor, in particular at a position which is more suitable for detecting ambient light without being affected by light emitted by the light sources of the aircraft beacon light.

Exemplary embodiments of the invention further include an aircraft comprising at least one aircraft beacon light according to an exemplary embodiment of the invention. The aircraft may be an air plane or a rotorcraft. The aircraft may in particular comprise a first aircraft beacon light, which is arranged on a top portion of the aircraft, in particular on a top portion of the fuselage of the aircraft, and a second aircraft beacon light, which is arranged on a bottom portion of the aircraft, in particular on a bottom portion of the fuselage of the aircraft.

Further exemplary embodiments of the invention are described below with respect to the accompanying drawings, wherein:.

<FIG> depicts a schematic side view of an aircraft <NUM> in accordance with an exemplary embodiment of the invention, which is equipped with two aircraft beacon lights <NUM> according to exemplary embodiments of the invention.

The aircraft <NUM> has a fuselage <NUM> and two wings <NUM>, which are attached to the right and left sides of the fuselage <NUM>. Each of the wings <NUM> carries an engine <NUM>. Further, two horizontal stabilizers <NUM> and a vertical stabilizer <NUM> are mounted to a tail portion of the fuselage <NUM>. In the schematic side view depicted in <FIG>, only one of the two wings <NUM>, the two engines <NUM> and the two horizontal stabilizers <NUM> is visible, respectively. It is pointed out that aircraft in accordance with other designs and constructions are encompassed by exemplary embodiments of the present invention as well.

The aircraft <NUM> further comprises two aircraft beacon lights <NUM>, mounted to the fuselage <NUM>. An upper aircraft beacon light <NUM> is mounted to a top portion (roof) of the fuselage <NUM>. A lower aircraft beacon light <NUM> is mounted to a bottom portion (belly) of the fuselage <NUM>. The aircraft <NUM> also comprises an aircraft power supply <NUM> for supplying electric power to electric consumers with in the aircraft <NUM>, in particular to the aircraft beacon lights <NUM>.

The aircraft <NUM> shown in <FIG> is an air plane <NUM>, in particular a large passenger or cargo air plane <NUM>. It is pointed out that other types of aircraft, such as smaller air planes <NUM>, may be equipped with aircraft beacon lights <NUM> in accordance with exemplary embodiments of the invention as well.

<FIG> shows a schematic side view of another aircraft <NUM>, in particular of a rotorcraft (helicopter) <NUM>, having a fuselage <NUM> and two rotors <NUM>, <NUM>.

A lower aircraft beacon light <NUM> according to an exemplary embodiment of the invention is mounted to a bottom portion (belly) of the fuselage <NUM>. An upper aircraft beacon light <NUM> is mounted to the top of a vertical stabilizer <NUM> at the tail <NUM> of the rotorcraft <NUM>. The aircraft <NUM> also comprises an aircraft power supply <NUM> for supplying electric power to electric consumers with in the aircraft <NUM>, in particular to the aircraft beacon lights <NUM>.

For both the <FIG> and <FIG> embodiments, the upper and lower aircraft beacon lights <NUM> are configured for emitting light flashes of red light in operation, in order to provide a beacon light behavior, as it is expected by other aircraft, ground personnel and air space control. The aircraft beacon lights <NUM> may in particular emit light flashes of aviation red light, with the light flashes of aviation red light indicating that the engines <NUM> of the aircraft <NUM> are running.

Although only two aircraft beacon lights <NUM> are shown in <FIG> and <FIG>, respectively, an aircraft <NUM>, <NUM> may comprise more than two aircraft beacon lights <NUM>. An aircraft <NUM>, <NUM> may in particular comprise various combinations of aircraft beacon lights, and at least some of the aircraft beacon lights may be mounted to the wings <NUM> and/or to the stabilizers <NUM>, <NUM>, <NUM> and/or to the tail <NUM>, <NUM> of the aircraft <NUM>, <NUM>. Not all aircraft beacon lights <NUM> of the aircraft <NUM> need to be aircraft beacon lights <NUM> according to exemplary embodiments of the invention.

The upper and lower aircraft beacon lights <NUM>, depicted in <FIG> and <FIG>, are formed in accordance with exemplary embodiments of the invention, the details of which will be described in the following.

<FIG> depicts a cross-sectional view of an aircraft beacon light <NUM> according to an exemplary embodiment of the invention, and <FIG> depicts a top view thereof. In particular, <FIG> depicts a vertical cross-sectional view through a center of the aircraft beacon light <NUM>, with the cross-sectional plane extending along the longitudinal direction of the aircraft, when the aircraft beacon light <NUM> is mounted to the aircraft.

The aircraft beacon light <NUM> comprises a plurality of light sources <NUM> for repeatedly emitting beacon light flashes. The light sources <NUM> are in particular configured for emitting red light. The light sources <NUM> may be or may include LEDs.

The light sources <NUM> are mounted to light source supports <NUM> extending from a ground plate <NUM>. The ground plate <NUM> may be a circuit board, in particular a printed circuit board (PCB). The light sources <NUM> and the light source supports <NUM> are arranged in an angular configuration (see <FIG>) for emitting light in all spatial directions, in particular for emitting light into a set of directions which, when projected onto a horizontal plane, covers an angle of <NUM>° around the aircraft beacon light <NUM>.

In the exemplary embodiment depicted in <FIG>, the aircraft beacon light <NUM> comprises eight planar light source supports <NUM>, which are arranged in an octagonal configuration. In the schematic illustration shown in <FIG>, each light source support <NUM> supports five light sources <NUM>, respectively. Every light source support <NUM>, however, may support a different number, in particular a larger number, of light sources <NUM>, respectively. The total number of light sources <NUM> of the aircraft beacon light <NUM> may in particular exceed the number of fifty light sources <NUM>.

The plurality of light sources <NUM> mounted to a common light source support <NUM> form one of eight subsets <NUM>-<NUM> of light sources <NUM>, respectively. The lights sources <NUM> of each subset <NUM>-<NUM> generate a light emission <NUM>-<NUM> around a common light emission direction L<NUM>-L<NUM>. Each light emission direction L<NUM>-L<NUM> is oriented substantially orthogonal to the plane of the corresponding light source support <NUM>.

The octagonal arrangement of the light source supports <NUM>, depicted in <FIG>, is only exemplary. An aircraft beacon light <NUM> according to exemplary embodiments of the invention may in particular comprise more or less than eight light source supports <NUM>.

In alternative configurations, which are not shown in the figures, the aircraft beacon light <NUM> may, for example, comprise four light source supports <NUM> arranged in a rectangular configuration, or six light source supports <NUM> arranged in a hexagonal configuration. It is also possible that the light sources are arranged along one or more curved light source support(s), in particular arranged along a cylindrical light source support. It is also possible that the light sources are arranged on the ground plate and that portions of their light output is directed laterally outwards by suitable optical element(s).

The light source supports <NUM> may be formed separately from each other. Alternatively, the light source supports <NUM> may be formed integrally with each other, forming a single light source support <NUM> comprising a plurality of planar light source support portions facing in different spatial directions.

An aircraft beacon light <NUM> according to an exemplary embodiment of the invention may also comprise a light source support <NUM> having an arcuate shape, for example having a circular or ellipsoidal cross-sectional shape, with the light sources <NUM> being arranged at the outer periphery of the arcuate shaped light source support <NUM>.

The aircraft beacon light <NUM> further comprises a light detection sensor <NUM>. The light detection sensor <NUM> is arranged on the ground plate <NUM> in a position in which it is surrounded by the annular arrangement of light sources <NUM>. The light detection sensor <NUM> may be, but not necessarily needs to be, arranged at the center of the annular arrangement of light sources <NUM>.

Optionally, the aircraft beacon light <NUM> may additionally comprise an ambient light sensor <NUM>, which is configured for detecting ambient light. The additional ambient light sensor <NUM> may be arranged inside or outside the annular arrangement of light sources <NUM>.

The ground plate <NUM> is supported by a base <NUM>, configured to be mounted to the exterior of the aircraft <NUM>, <NUM>, which is not depicted in <FIG> and <FIG>.

The aircraft beacon light <NUM> also comprises a light transmissive cover <NUM>, supported by the base <NUM> and covering the light detection sensor <NUM> and the annular arrangement of light sources <NUM>.

At least one reflective portion <NUM> is arranged on the inside of the light transmissive cover <NUM>, in particular arranged opposite the ground plate <NUM> and facing the light sources <NUM> and the light detection sensor <NUM>.

In the orientation depicted in <FIG>, which corresponds to an orientation in which the aircraft beacon light <NUM> would be mounted to a top portion of an aircraft <NUM>, <NUM>, the at least one reflective portion <NUM> is arranged above the light sources <NUM> and the light detection sensor <NUM>. In a configuration, in which the aircraft beacon light <NUM> is mounted in an upside-down orientation to a bottom portion of the aircraft <NUM>, <NUM>, the at least one reflective portion <NUM> would be arranged below the light sources <NUM> and the light detection sensor <NUM>.

The at least one reflective portion <NUM> is configured for reflecting light emitted by the light sources <NUM> onto the light detection sensor <NUM>. As a result, the light detection sensor <NUM> provides sensor measurement outputs, correlating with the light emitted by the light sources <NUM>.

The reflective portion <NUM> may have a rotational symmetry with respect to a vertical axis A, extending perpendicular to the ground plate <NUM> and to the base <NUM>. In particular embodiments, in which the light sources are arranged in a polygonal configuration, the reflective portion <NUM> may have a corresponding polygonal symmetry.

In the embodiment depicted in <FIG>, the reflective portion <NUM> comprises a central planar reflective portion 16a and a curved reflective portion 16b formed at the outer periphery of the planar reflective portion 16a.

The curved reflective portion 16b may extend from a vertical line V, extending parallel to the vertical axis A through the light sources <NUM>, to an angle α in the range of <NUM>° to <NUM> °, particularly to an angle α in the range of <NUM> ° to <NUM> °, more particularly to an angle α of <NUM> °, with respect to the vertical line V, when measured from the light sources <NUM>. The angle α extends laterally outwards from the vertical line V.

Optionally, the curved reflective portion 16b may have an ellipsoidal shape.

The light sources <NUM> and the light detection sensor <NUM> may by arranged so that the curved reflective portion 16b collimates light, emitted by the light sources <NUM>, towards the position of the light detection sensor <NUM>.

In the embodiment depicted in <FIG>, the reflective portion <NUM> is provided inside the light transmissive cover <NUM>, so that it is protected by the light transmissive cover <NUM> from adverse exterior influences, such as water, moisture, dirt, dust and mechanical impact.

In the embodiment depicted in <FIG>, the at least one reflective portion <NUM> is provided as a separate component supported by the light transmissive cover <NUM>.

In an alternative configuration, which is not explicitly shown in the figures, the at least one reflective portion <NUM> may be supported by an additional support structure, which is provided separately form the light transmissive cover <NUM>. The side of the at least one reflective portion <NUM>, facing the light sources <NUM> and the light detection sensor <NUM>, may be covered with a light reflective coating or paint.

The at least one reflective portion <NUM>, for example, may be provided as a light reflective coating or paint, which is applied to the light transmissive cover <NUM>.

The at least one reflective portion <NUM> may include a specular reflecting portion and/ or a diffusely reflecting portion. A diffusely reflecting portion may be provided by a bright paint, in particular a white paint, applied to the at least one reflective portion <NUM> and/or the light transmissive cover <NUM>.

The aircraft beacon light <NUM> further comprises a controller <NUM>. The controller <NUM> is configured for controlling the operation of the light sources <NUM> and for evaluating the sensor measurement outputs, provided by the light detection sensor <NUM>.

In an aircraft beacon light <NUM> according to an exemplary embodiment of the invention, the controller <NUM> is in particular configured for cyclically selecting one subset <NUM>-<NUM> of light sources <NUM> after the other and for modifying the length of at least one of the beacon light flashes <NUM>-<NUM> emitted by the light sources <NUM> of the selected subset <NUM>-<NUM> (cf. <FIG> and <FIG>) and/or modifying the lengths of the beacon light flashes <NUM>-<NUM> emitted by the light sources <NUM> of the non-selected subset(s) <NUM>-<NUM>, so that the length of at least one beacon light flash <NUM>-<NUM> emitted by the light sources <NUM> of the selected subset <NUM>-<NUM> exceeds the lengths of the beacon light flashes <NUM>-<NUM> emitted by the light sources <NUM> of the non-selected subset(s) <NUM>-<NUM> by a predetermined extension time period T<NUM>, T<NUM>, T<NUM>, T<NUM> and only the light sources <NUM> of the selected subset <NUM>-<NUM> are active during said extension time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>.

Modifying the length of at least one of the beacon light flashes <NUM>-<NUM> may include extending the length of at least one of the light flashes <NUM>-<NUM>, emitted by the light sources <NUM> of the selected subset <NUM>-<NUM>, and/or shortening the lengths of the beacon light flashes <NUM>-<NUM>, emitted by the light sources of the non-selected subsets <NUM>-<NUM> of light sources <NUM>.

The controller <NUM> is further configured for determining a health status of the aircraft beacon light <NUM> by evaluating the sensor measurement outputs, provided by the light detection sensor <NUM> during said extension time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>.

The diagrams shown in <FIG> schematically illustrate the operation of the light sources <NUM> according to an exemplary embodiment of the invention.

In the diagrams shown in <FIG>, the time t is plotted on the horizontal axis, and the current I flowing through the light sources <NUM> of each subset of light sources <NUM> is plotted on the vertical axis.

For clarity, only four subsets <NUM>-<NUM> of light sources <NUM> and only four light flashes <NUM>-<NUM> are illustrated in <FIG>. The skilled person may easily extrapolate the information provided by <FIG> to further light flashes and to additional subsets of light sources <NUM>.

At the beginning of each light flash <NUM>-<NUM>, all light sources <NUM> of the aircraft beacon light <NUM> are simultaneously activated and operated during a first time period T<NUM>, T<NUM>, T31, T<NUM>, e.g. during a first time period T<NUM>, T<NUM>, T<NUM>, T<NUM> of approximately <NUM>.

At the end of the first time period T<NUM>, T<NUM>, T<NUM>, T<NUM>, the light sources <NUM> of all but a selected single subset <NUM>-<NUM> of light sources <NUM> are deactivated, and the light sources <NUM> of the selected single subset <NUM>-<NUM> of light sources <NUM> are continued to be operated for an additional second time period T<NUM>, T<NUM>, T<NUM>, T<NUM>, which corresponds to the previously mentioned extension time period T<NUM>, T<NUM>, T<NUM>, T<NUM>.

The second time period T<NUM>, T<NUM>, T<NUM>, T<NUM>, for example, may have a length of <NUM>. The selected subset <NUM>-<NUM> of light sources <NUM>, which are operated for the additional second time period T<NUM>, T<NUM>, T<NUM>, T<NUM>, is cyclically changed after every light flash <NUM>-<NUM>. In other words, another subset <NUM>-<NUM> is selected after every light flash <NUM>-<NUM>.

In an alternative configuration, a new subset <NUM>-<NUM> may be selected not after every light flash <NUM>-<NUM>, but after every n-th light flash <NUM>-<NUM>, with n being a natural number larger than <NUM>.

As a result, over time, every subset <NUM>-<NUM> of light sources <NUM> is activated for the additional extension time period at some point.

In the exemplary configuration depicted in <FIG>, the operation time of the light sources <NUM> of the first subset <NUM> is extended for the first light flash <NUM>, the operation time of the light sources <NUM> of the second subset <NUM> is extended for the second light flash <NUM>, the operation time of the light sources <NUM> of the third subset <NUM> is extended for the third light flash <NUM>, and the operation time of the light sources <NUM> of the fourth subset <NUM> is extended for the fourth light flash <NUM>.

The previously mentioned specific values for the first time periods T<NUM>, T<NUM>, T<NUM>, T<NUM> of <NUM> and of <NUM> for the second time periods of T<NUM>, T<NUM>, T<NUM>, T<NUM> are only exemplary, and the light sources <NUM> may be activated for shorter or longer time periods. The first time periods T<NUM>, T<NUM>, T<NUM>, T<NUM> may in particular be selected from a range of between <NUM> and <NUM>, in particular from a range of between <NUM> and <NUM>; and the second time periods of T<NUM>, T<NUM>, T<NUM>, T<NUM> may be selected from a range of between <NUM> and <NUM>, in particular from a range of between <NUM> and <NUM>, respectively.

<FIG> depicts a diagram illustrating exemplary sensor measurement outputs, provided by the light detection sensor <NUM>. The sensor measurement outputs M, which correlate to the intensity of light detected by the light detection sensor <NUM>, are plotted on the vertical axis, and the time t is plotted on the horizontal axis.

During the first time periods T<NUM>, T<NUM>, T<NUM>, T<NUM> all light sources <NUM> are activated, as it has been described with reference to <FIG>. As a result, the light detection sensor <NUM> provides a high sensor measurement output MH, which is identical for all first time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>.

During the second time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>, following the respective first time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>, only a respective single subset <NUM>-<NUM> of the light sources <NUM> is activated, as it has been described before with reference to <FIG>.

In consequence, the sensor measurement outputs M, provided by the light detection sensor <NUM> during the second time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>, are smaller than the high sensor measurement output MH, provided during the first time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>.

Further, the sensor measurement outputs M, provided by the light detection sensor <NUM> during the second time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>, are in general not identical.

For example, different erosion levels of different portions of the light transmissive cover <NUM>, facing into different spatial directions, may cause the sensor measurement outputs, provided by light detection sensor <NUM> during the second time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>, to be lower or higher than an average sensor measurement output Mavg.

In the example depicted in <FIG>, the first light flash <NUM> is emitted by the light sources <NUM> of the first subset <NUM> of light sources <NUM>, which are directed forward (cf.

Due to mechanical impact of dust and dirt during flight, the front side of the light transmissive cover <NUM>, facing into the direction of flight FD (see <FIG> and <FIG>), is most prone to erosion. Erosion of the light transmissive cover <NUM> causes a portion of the light, emitted by the forward directed light sources <NUM>, to be diffusely reflected by the light transmissive cover <NUM>. This prevents the reflected portion of light from passing the light transmissive cover <NUM>, resulting in a decrease of the amount of light emitted by the aircraft beacon light <NUM> and in an increased illumination of the light detection sensor <NUM>.

In consequence, the sensor measurement output, provided by the light detection sensor <NUM> during the second time period T<NUM> of the first light flash <NUM>, is higher than an average sensor measurement output Mavg, as it is depicted in <FIG>.

A slow increase of the sensor measurement outputs, which are provided while the forward directed light sources <NUM> are activated, indicates erosion of the light transmissive cover <NUM>. Thus, the controller <NUM> may be configured for issuing an alarm signal, indicating that the light transmissive cover <NUM> needs to be replaced, when the sensor measurement outputs, which are provided while the forward directed light sources <NUM> are activated, permanently exceed a predefined threshold Mth.

Since a decrease of the intensity of light, emitted by the light sources <NUM> due to aging of the light sources <NUM>, may at least partially be compensated by an increased reflection of the light transmissive cover <NUM> caused by erosion, the mentioned increase of sensor measurement outputs due to erosion of the light transmissive cover <NUM> may prevent the controller <NUM> from reliably detecting aging of the light sources <NUM>.

In consequence, only sensor measurement outputs provided during the operation of light sources <NUM> not facing into the forward direction may be used for detecting aging of the light sources <NUM>.

Cyclically extending the length of at least one of the beacon light flashes, emitted by the light sources <NUM> of the selected subset <NUM>-<NUM>, and/or shortening the lengths of the beacon light flashes <NUM>-<NUM>, emitted by the light sources of the non-selected subsets <NUM>-<NUM>, for predetermined extension time periods T<NUM>, T<NUM>, T<NUM>, T<NUM> and evaluating the sensor measurement outputs, provided by the light detection sensor <NUM> during the predetermined extension time periods T<NUM>, T<NUM>, T<NUM>, T<NUM>, allows for the controller <NUM> to individually evaluate the light output provided by the different subsets <NUM>-<NUM> of light sources <NUM>.

As a result, damage or aging of the light sources <NUM> may be detected individually for each subset <NUM>-<NUM> of light sources <NUM> with only a single light detection sensor <NUM>.

Individually evaluating the light output provided by the different subsets <NUM>-<NUM> of light sources <NUM> may allow for detecting and localizing erosion of the light transmissive cover <NUM>. It further may allow for distinguishing between deterioration of the light output provided by the aircraft beacon light <NUM> caused by damage or aging of the light sources <NUM> and deterioration of the light output caused by erosion of the light transmissive cover <NUM>.

Details of the electric configuration of an aircraft beacon light <NUM> according to an exemplary embodiment of the invention is described in the following with reference to <FIG>.

<FIG> depicts a schematic block-diagram of an aircraft beacon light <NUM> according to an exemplary embodiment of the invention.

The aircraft beacon light <NUM> depicted in <FIG> comprises two power lines <NUM>, which are electrically connected to the controller <NUM> for receiving electrical power from an aircraft power supply <NUM> for operating the light sources <NUM>. The aircraft power supply <NUM> may in particular periodically supply electric power pulses to the aircraft beacon light <NUM>, for example electric power pulses having lengths of approximately <NUM>, for operating the aircraft beacon light <NUM> in a flash light mode.

The controller <NUM> comprises a cyclic delay timer <NUM> and a plurality of bypass circuits <NUM>, <NUM>, <NUM>. Each bypass circuit <NUM>, <NUM>, <NUM> is associated with one of the subsets <NUM>, <NUM>, <NUM> of light sources <NUM> and configured for selectively bypassing the light sources <NUM> of the associated subset <NUM>, <NUM>, <NUM>, respectively.

For clarity, only three subsets <NUM>, <NUM>, <NUM> of light sources <NUM> and three bypass circuits <NUM>, <NUM>, <NUM> are depicted in <FIG>. The skilled person can extrapolate the information provided by <FIG> to aircraft beacon lights <NUM> comprising more than three subsets <NUM>, <NUM>, <NUM> of light sources <NUM> and a corresponding number of bypass circuits <NUM>, <NUM>, <NUM>. The aircraft beacon light <NUM> may for example comprise eight subsets of light sources, as described above, and eight bypass circuits or may comprise a smaller or lager number of subsets of light sources and bypass circuits.

When the aircraft beacon light <NUM> according to an exemplary embodiment of the invention is operated, the cyclic delay timer <NUM> cyclically selects one of the bypass circuits <NUM>, <NUM>, <NUM>.

At the end of the predetermined first time period T<NUM>, T<NUM>, T<NUM>, which is shorter than the length of the electric power pulses provided by the aircraft power supply <NUM>, the cyclic delay timer <NUM> activates all bypass circuits except for the selected bypass circuit. As a result, the light sources <NUM> of all subsets of light sources <NUM>, expect for the light sources <NUM> associated with the selected bypass circuit, are bypassed and thereby deactivated, so that only the light sources <NUM> associated with the selected bypass circuit are continued to be operated, as it is illustrated in the diagrams shown in <FIG>.

A portion of the light emitted by the still activated light sources <NUM> is reflected by the reflective portion <NUM> and/or by the light transmissive cover <NUM> (see <FIG>). The reflected portion of light is detected by the light detection sensor <NUM> and a corresponding sensor measurement output is transmitted from the light detection sensor <NUM> to an evaluation logic <NUM>.

The evaluation logic <NUM> is configured for evaluating the received sensor measurement output and for providing a resulting evaluation output, indicating aging of the light sources <NUM> and/or erosion of the light transmissive cover <NUM> at an evaluation output line <NUM>.

The cyclic delay timer <NUM> and the evaluation logic <NUM> may be provided as dedicated electronic circuits within the controller <NUM>. Alternatively, they may be provided a separate electronic circuits separately from the controller <NUM>.

The controller <NUM> may also comprise at least one microprocessor <NUM>, and the functionalities of the controller <NUM>, in particular the functionalities of the cyclic delay timer <NUM> and/or of the evaluation logic <NUM>, may be at least partly implemented as software programs running on said at least one microprocessor <NUM>.

The controller <NUM> may further comprise a memory <NUM>, which allows for storing the sensor measurement outputs and evaluating changes of the sensor measurement outputs over time. Evaluating changes of the sensor measurement outputs over time may allow for detecting erosion of the light transmissive cover <NUM> and/or detecting aging of the light sources <NUM> from a gradual change of the sensor measurement outputs, provided by the light detection sensor <NUM> over time.

Ambient light detected by the light detection sensor <NUM> may disturb the evaluation of the sensor measurement output provided by the light detection sensor <NUM> and cause false or unreliable evaluation results.

In order to avoid false and unreliable measurement results caused by ambient light, the evaluation logic <NUM> may be configured for evaluating the sensor measurement outputs provided by the light detection sensor <NUM> only if the intensity of detected ambient light is below a predefined ambient light threshold.

Ambient light may be detected by the light detection sensor <NUM> during time periods in which all light sources <NUM> are deactivated. Alternatively, the aircraft beacon light <NUM> may comprise an additional ambient light sensor <NUM> (see <FIG> and <FIG>), which is configured for detecting ambient light.

Claim 1:
Aircraft beacon light (<NUM>) with integrated health monitoring, comprising:
an annular arrangement of light sources (<NUM>), configured for repeatedly emitting beacon light flashes (<NUM>-<NUM>);
a light detection sensor (<NUM>) surrounded by the annular arrangement of light sources (<NUM>);
a light transmissive cover (<NUM>), covering the annular arrangement of light sources (<NUM>) and the light detection sensor (<NUM>); and
at least one reflective portion (<NUM>) arranged to reflect light, emitted by the annular arrangement of light sources (<NUM>), onto the light detection sensor (<NUM>)
wherein the at least one reflective portion (<NUM>) is provided as a separate component, supported by the light transmissive cover (<NUM>).