Abstract
An exterior aircraft light includes a housing having a length (L), a width (W), and a height (H), the length (L) being greater than the width (W) and the height (H) and the housing having a front end region and a rear end region, wherein the housing is configured to be mounted on a tail portion of a fuselage of an aircraft; at least one first light source, arranged in the rear end region of the housing, for providing aircraft rearward signal lighting; and a plurality of second light sources, which are arranged spaced along the length (L) of the housing for a distributed illumination of a stabilizer of the aircraft.
Claims
1. An exterior aircraft light, comprising: a housing having a length (L), a width (W), and a height (H), the length (L) being greater than the width (W) and the height (H) and the housing having a front end region and a rear end region with respect to its length, wherein the housing is configured to be mounted on a tail portion of a fuselage of an aircraft, with the length (L) of the housing being arranged along a stabilizer of the aircraft and generally along a longitudinal direction of the fuselage; at least one first light source, arranged in the rear end region of the housing, for providing at least one of aircraft rearward navigation lighting, aircraft rearward white strobe anti-collision lighting, and aircraft rearward red beacon lighting; and a plurality of second light sources, which are arranged spaced along the length (L) of the housing for a distributed illumination of said stabilizer of the aircraft.
2. The exterior aircraft light according to claim 1, wherein the at least one first light source is exactly one first light emitting diode (LED).
3. The exterior aircraft light according to claim 1, further comprising: at least one first optical system, associated with the at least one first light source, with the at least one first optical system transforming the light output from the at least one first light source into a signalling output light intensity distribution for aircraft rearward signal lighting.
4. The Exterior aircraft light according to claim 3, wherein the at least one first optical system comprises at least one lens.
5. The exterior aircraft light according to claim 3, wherein the signalling output light intensity distribution has a horizontal opening angle of at least 70°.
6. The exterior aircraft light according to claim 5, wherein the horizontal opening angle is 70° and 90°.
7. The exterior aircraft light according to claim 3, wherein the signalling output light intensity distribution has a vertical opening angle of at least 90°.
8. The exterior aircraft light according to claim 1, configured to operate the at least one first light source in at least two modes of operation, which comprise: a navigation mode of operation, wherein the at least one first light source continuously outputs light of a first light intensity, and an anti-collision mode of operation, wherein the at least one first light source outputs a sequence of light pulses, with the light pulses having a second light intensity.
9. The exterior aircraft light according to claim 8, wherein a ratio between the second light intensity and the first light intensity has a value of at least 15.
10. The exterior aircraft light according to claim 8, wherein the at least two modes of operation further comprise: a combined mode of operation, wherein the at least one first light source outputs a sequence of light pulses, with the light pulses having at least the second light intensity, and wherein the at least one first light source outputs light of at least the first light intensity between the light pulses.
11. The exterior aircraft light according to claim 1, having a stabilizer illumination opening angle of between 40° and 70° in at least one cross-section orthogonal to the length of the exterior aircraft light, for illuminating the stabilizer of the aircraft.
12. An aircraft including at least one exterior aircraft light in according to claim 1.
13. The aircraft according to claim 12, comprising: a fuselage having a tail portion; a vertical stabilizer; a left horizontal stabilizer; and a right horizontal stabilizer; wherein the at least one exterior aircraft light comprises: a first exterior aircraft light, mounted to the tail portion of the fuselage between the vertical stabilizer and the left horizontal stabilizer; a second exterior aircraft light, mounted to the tail portion of the fuselage between the vertical stabilizer and the right horizontal stabilizer; a third exterior aircraft light, mounted to the tail portion of the fuselage below the left horizontal stabilizer; and a fourth exterior aircraft light, mounted to the tail portion of the fuselage below the right horizontal stabilizer.
14. A method of operating an exterior aircraft light mounted to a tail portion of a fuselage of an aircraft along a stabilizer of the aircraft and generally along a longitudinal direction of the fuselage, comprising: providing at least one of aircraft rearward navigation lighting, aircraft rearward white strobe anti-collision lighting, and aircraft rearward red beacon lighting from a rear end region of the exterior aircraft light via at least one first light source, and providing distributed illumination of said stabilizer of the aircraft via a plurality of second light sources, which are arranged spaced along the exterior aircraft light.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) Further exemplary embodiments of the invention will be described with respect to the accompanying Figures.
(2) FIG. 1 shows an aircraft in accordance with an exemplary embodiment of the invention in a rear view, the aircraft being equipped with four exterior aircraft lights in accordance with exemplary embodiments of the invention;
(3) FIG. 2 shows an exterior aircraft light in accordance with an exemplary embodiment of the invention;
(4) FIG. 3A shows the aircraft rearward signalling part of the exterior aircraft light of FIG. 2 in a perspective views;
(5) FIG. 3B shows the aircraft rearward signalling part of the exterior aircraft light of FIG. 2 in a perspective views;
(6) FIG. 4A shows a cross-sectional views through the aircraft rearward signalling part of the exterior aircraft light of FIG. 2;
(7) FIG. 4B shows a cross-sectional views through the aircraft rearward signalling part of the exterior aircraft light of FIG. 2;
(8) FIG. 5A shows an exemplary signalling output light intensity distributions of one and two exterior aircraft lights in accordance with exemplary embodiments of the invention;
(9) FIG. 5B shows an exemplary signalling output light intensity distributions of one and two exterior aircraft lights in accordance with exemplary embodiments of the invention;
(10) FIG. 6A shows an exemplary light intensity distributions relevant to the signalling output light intensity distributions of exterior aircraft lights in accordance with exemplary embodiments of the invention;
(11) FIG. 6B shows an exemplary light intensity distributions relevant to the signalling output light intensity distributions of exterior aircraft lights in accordance with exemplary embodiments of the invention;
(12) FIG. 6C shows an exemplary light intensity distributions relevant to the signalling output light intensity distributions of exterior aircraft lights in accordance with exemplary embodiments of the invention;
(13) FIG. 7A shows exemplary courses of an output light intensity of the aircraft rearward signalling part of an exterior aircraft light in accordance with an exemplary embodiment of the invention over time in one mode of operation;
(14) FIG. 7B shows exemplary courses of an output light intensity of the aircraft rearward signalling part of an exterior aircraft light in accordance with an exemplary embodiment of the invention over time in one mode of operation;
(15) FIG. 7C shows exemplary courses of an output light intensity of the aircraft rearward signalling part of an exterior aircraft light in accordance with an exemplary embodiment of the invention over time in one mode of operation;
(16) FIG. 8 shows a tail portion of an aircraft in accordance with an exemplary embodiment of the invention, equipped with an exterior aircraft light according to an exemplary embodiment of the invention, in a top perspective view;
(17) FIG. 9 shows the aircraft of FIG. 1 in the same rear view, illustrating the light output towards the vertical stabilizer for one of the exterior aircraft lights in accordance with exemplary embodiments of the invention;
(18) FIG. 10 shows a cross-sectional view through the stabilizer illumination part of an exterior aircraft light in accordance with an exemplary embodiment of the invention;
(19) FIG. 11 shows an illumination pattern upon a vertical stabilizer, effected by an exterior aircraft light in accordance with an exemplary embodiment of the invention.
DETAILED DESCRIPTION
(20) FIG. 1 shows an aircraft 110, in particular a large commercial passenger airplane, in accordance with an exemplary embodiment of the invention in a rear view. The aircraft 110 has a fuselage 100, a left wing 103, provided with a left engine 107, a right wing 203, provided with a right engine 207, a left horizontal stabilizer 102, a right horizontal stabilizer 202, and a vertical stabilizer 104. The left horizontal stabilizer 102, the right horizontal stabilizer 202, and the vertical stabilizer 104 are provided in a tail portion 105 of the fuselage 100.
(21) The aircraft 110 is equipped with four exterior aircraft light units 101, 201, 301, 401 in accordance with exemplary embodiments of the invention. Each of the exterior aircraft lights 101, 201, 301, 401 has dual purpose, namely to illuminate a surface of one of the stabilizers of the aircraft and to provide rearward signal lighting. These functionalities will be described in detail below. In FIG. 1, the illumination of the respective stabilizer surfaces is illustrated by hatched cones, illustrating the respective light outputs of the exterior aircraft lights towards the respective stabilizer surfaces. The rearward signal lighting is not illustrated in FIG. 1, as it is output towards the observer of FIG. 1, but will be described in detail below.
(22) The first exterior aircraft light 101 in operation illuminates the left side of the vertical stabilizer 104 and provides rearward signal lighting. The second exterior aircraft light 201 in operation illuminates the right side of the vertical stabilizer 104 and provides rearward signal lighting. The third exterior aircraft light 301 in operation illuminates the underside of the left horizontal stabilizer 102 and provides rearward signal lighting. The fourth exterior aircraft light 401 in operation illuminates the underside of the right horizontal stabilizer 202 and provides rearward signal lighting. In the exemplary embodiment of FIG. 1, the first exterior aircraft light 101, the second exterior aircraft light 201, the third exterior aircraft light 301, and the fourth exterior aircraft light 401 jointly provide rearward navigation lighting and rearward white strobe anti-collision lighting for the aircraft 110. This will be described in detail below.
(23) FIG. 2 shows an exterior aircraft light 101 in accordance with an exemplary embodiment of the invention in a side view. The exterior aircraft light 101 may be used as the first exterior aircraft light 101 of FIG. 1, provided inter alia for illuminating the underside of the left horizontal stabilizer 102. The exterior aircraft light 101 is shown from the left in the aircraft frame of reference. It is understood and apparent to the skilled person that the exterior aircraft light 101 may also be used for the other exterior aircraft lights, depicted in FIG. 1, upon re-arrangement of individuals components and/or re-orientation/mirroring of individual components and/or adjustments regarding the light output angles.
(24) The exterior aircraft light 101 has a housing 2, having a fuselage mounting plate 4 and a lens cover 6. The fuselage mounting plate 4 and the lens cover 6 form an inner space where the light sources and optical systems are arranged, as will be described below. The housing 2 has a front end region 30 and a rear end region 32. The orientation of the exterior aircraft light 101 is further illustrated by arrow 34, which indicates the aircraft rear direction. Accordingly, in the viewing direction of FIG. 1, the rear end region 32 is visible.
(25) The exterior aircraft light 101 comprises a first light source 10 and a first optical system 12. The first light source 10 and the first optical system 12 are arranged on a first mounting plate 14 in the rear end region 32 of the exterior aircraft light 101. The first light source 10 and the first optical system 12 face rearward, i.e. generally in the rear direction 34 of the aircraft. For this purpose, the first mounting plate 14 is generally orthogonal to the fuselage mounting plate 4. In the exemplary embodiment of FIG. 1, the first light source 10 is a first LED.
(26) The exterior aircraft light 101 further comprises a plurality of second light sources 20. Each second light source 20 is associated with a respective second optical system 22, and these associated components are respectively arranged on a second mounting plate 24. In the exemplary embodiment of FIG. 2, six second light sources 20 are provided. The second mounting plates 24 are generally parallel to the fuselage mounting plate 4. It is also possible that the second light sources 20 and the second optical systems 22 are arranged directly on the fuselage mounting plate 4.
(27) The exterior aircraft light 101 of FIG. 2 has a dual purpose, namely to provide rearward signal lighting via the first light source 10 and the first optical system 12 and to provide illumination of a stabilizer surface of the aircraft via the plurality of second light sources 20 and the associated plurality of second optical systems 22. In order to receive power and control information, the exterior aircraft light 101 has four electrical connections in the exemplary embodiment of FIG. 2. A first electrical connection 40 is a ground connection. A second electrical connection 42 is an anti-collision mode power connection. A third electrical connection 44 is a navigation mode power connection. A fourth electrical connection 46 is a stabilizer illumination power connection. Via each of the second, third, and fourth electrical connections 42, 44, 46, an appropriate amount and time sequence of power is supplied to the exterior aircraft light 101 for the desired lighting functionality. Via the second electrical connection 42, pulsed current is provided to the first light source 10, which results in an intermittent/flashing light emission by the first light source 10, thus achieving anti-collision lighting. Via the second electrical connection 44, a continuous stream of power is provided to the first light source 10, which results in a continuous light output for navigation lighting. Via the fourth electrical connection 46, a continuous stream of power is provided to the plurality of second light sources 20 for illuminating the desired stabilizer surface. A control unit may be provided outside of the exterior aircraft light 101 and supply power via the second, third and fourth electrical connections 42, 44, 46 for achieving a desired light output at any point in time. However, it is also possible that more of the control functionality is provided within the exterior aircraft light 101. For example, it is possible that the exterior aircraft light 101 has a power input and a control input and that the exterior aircraft light 101 itself generates appropriate supplies of electrical power to the first power source and the plurality of second power sources 20, depending on the information received via the control input.
(28) The rearward signal lighting functionality and the stabilizer illumination functionality of the exterior aircraft light 101 will be described in detail below with respect to the remaining Figures. While FIGS. 3 to 7 relate to the rearward signal lighting, FIGS. 8 to 11 relate to the stabilizer illumination.
(29) FIG. 3 shows the first optical system 12 and the first mounting plate 14 of the exterior aircraft light 101 of FIG. 2 in a lower perspective view in FIG. 3A and in an upper perspective view in FIG. 3B. The first light source 10 is not visible in the viewing directions of FIG. 3A and FIG. 3B, because it is arranged between the first optical system 12 and the first mounting plate 14. The first mounting plate 14 may be a printed circuit board that provides mechanical support for the first light source 10 and the first optical system 12 as well as power supply to the first light source 10.
(30) In the exemplary embodiment of FIG. 3, the first optical system 12 is a lens with various optically effective surfaces. In particular, the lens of FIG. 3 has a total internal reflection surface 50, a first central light output surface 52, a second central light output surface 54, a first lateral light output surface 56, a second lateral light output surface 58, a first shutter 60, and a second shutter 62. The optical effects of these surfaces will be described below with reference to FIG. 4. The lens may be made from any suitable refractive material, for example from PMMA, PC, silicone, glass, etc. It is pointed out that the first optical system 12 may have many different forms and may comprise various different elements, such as reflecting elements, refracting elements, shutters, etc. While the given lens is an efficient means of generating a desired signalling output light intensity distribution, it is apparent to the skilled person that other approaches are possible as well.
(31) FIG. 4A shows a horizontal cross-sectional view through the first light source 10, the first optical system 12, and the first mounting plate 14. The cross-sectional plane of FIG. 4A is indicated by the dashed line A-A in FIG. 3B. The cross-sectional plane of FIG. 4A is referred to as horizontal cross-sectional plane, because this cross-sectional plane comes to lie horizontally in the aircraft frame of reference when the exterior aircraft light is mounted on the aircraft.
(32) The optical effect of the various optical surfaces is now described with respect to a central light emission direction 36, orthogonal to the first mounting plate 14, and illustrated by various light rays. The light around the central light emission direction 36 passes the lens 12 fairly unaltered. In other words, the first central light output surface 52 does not have a big refractive impact on the passing light. The first and second lateral light output surfaces 56, 58 are stripe optics that refract light towards the central light emission direction 36. The first and second shutters 60, 62 block light from exiting the first optical system 12 at small angles with respect to the first mounting plate 14. In this way, a horizontal opening angle α of about 70° is achieved.
(33) The central light emission direction 36 is angled at about 35° with respect to the aircraft rear direction 34. In this way, the light output covers about 70° horizontally between the aircraft rear direction 34 and a right rear direction of the aircraft. In this way, the exterior aircraft light 101 is able to cover about half of the horizontal opening angle required by FAR regulations for rearward navigation lights.
(34) FIG. 4B shows a vertical cross-sectional view through the first light source 10, the first optical system 12 and the first mounting plate 14. The cross-sectional plane of FIG. 4B is indicated by dashed line B-B in FIG. 3B. The cross-sectional plane of FIG. 4B is referred to as vertical cross-sectional plane, because this cross-sectional plane comes to lie vertically in the aircraft frame of reference when the exterior aircraft light 101 is mounted on the aircraft.
(35) The total internal reflection surface 50 collimates a portion of the light from the first light source 10 in or close to the rear direction 34. Again, the light passes the first central light output surface 52 in a substantially unaltered manner. The second central light output surface 54 provides for some refraction of the light from the first light source 10. Overall, the total internal reflection surface 50, the first central light output surface 52, the second central light output surface 54 and an internal refractive surface 64 of the lens 12 provide for the desired transformation from the source-side light intensity distribution of the first light source 10 into the desired signalling output light intensity distribution.
(36) The signalling output light intensity distribution has an opening angle β of about 90° in the vertical cross-sectional plane, depicted in FIG. 4B. In this way, the signalling output light intensity distribution is able to satisfy the upper half of the FAR requirements for navigation lights, as will be described in more detail below.
(37) It is also possible that the opening angle β is larger than 90°. In particular, it is possible that the opening angle β is about 100°, for example due to the first light source 10 not being an ideal point light source and its image extending the opening angle β. With the opening angle β being above 90°, it is possible to tilt the first light source 10 and the first optical system 12 downwards. In this way, some light is still emitted straight up, i.e. at a vertical angle of 90° with respect to the aircraft rear direction, while more of the light output is concentrated around the horizontal plane.
(38) While it has been described that the first light source 10 and the first optical system 12 of the exterior aircraft light 101 of FIGS. 2 to 4 can satisfy rearward navigation lighting requirements for a sector of those requirements, the signalling output light intensity distribution can also satisfy anti-collision light requirements upon increasing the light intensity and providing pulsed power to the first light source 10. The first light source can be operated in a navigation mode of operation and an anti-collision mode of operation. This will be described in detail below with respect to FIGS. 6 and 7.
(39) FIG. 5A shows a signalling output light intensity distribution of an exterior aircraft light in accordance with an exemplary embodiment of the invention, with the first light source being operated in the anti-collision mode of operation, in the vertical cross-section plane of FIG. 4B. As the depicted signalling output light intensity distribution is for the anti-collision mode of operation, it is also referred to as anti-collision output light intensity distribution 70. For comparison, the Federal Aviation Regulation (FAR) requirements for the vertical distribution of anti-collision lighting are given as a dashed curve, also referred to as predefined anti-collision mode light intensity distribution 80. It can be seen that the anti-collision output light intensity distribution 70 satisfies the FAR requirements for half of the vertical angular range, namely for the upper half, i.e. for the angles above the horizontal cross-sectional plane through the exterior aircraft light.
(40) FIG. 5B shows a signalling output light intensity distribution of two exterior aircraft lights in accordance with exemplary embodiments of the invention, with the respective first light sources being operated in the anti-collision mode of operation, in the vertical cross-section plane of FIG. 5A. In particular, the joined anti-collision output light intensity distribution 72 may belong to the first and third exterior aircraft lights 101, 301 of FIG. 1, when operated in the anti-collision mode of operation. It can be seen that the joined anti-collision output light intensity distribution 72 satisfies the FAR requirements for the whole vertical angular range, i.e. for all angles above and below the horizontal cross-sectional plane through the exterior aircraft light. In this way, the two exterior aircraft lights work together to fulfil the FAR requirements for anti-collision lights for the depicted as well as various other vertical cross-sectional planes.
(41) FIG. 6A shows an exemplary embodiment of a predefined anti-collision mode light intensity distribution 80, defined by the FAR requirements for the respective angles, and an exemplary embodiment of a predefined navigation mode light intensity distribution 82, defined by the FAR requirements for the respective angles, in a vertical cross-sectional plane. The light intensity distributions 80 and 82 are given in terms of angles with respect to the horizontal direction.
(42) The predefined anti-collision mode light intensity distribution 80 and the predefined navigation mode light intensity distribution 82 are required light intensity distributions for an anti-collision light and a navigation light, respectively, according to Federal Aviation Regulations (FAR). The depicted courses of the light intensity distributions indicate minimum values in accordance with the FAR. Accordingly, for an anti-collision light or a navigation light to be in accordance with the respective FAR requirements, the output light intensity distributions must be above the shown course for all angles.
(43) The exemplary predefined anti-collision mode light intensity distribution 80 requires the following minimum light intensity values in the vertical cross-sectional plane. A light intensity of 400 cd is required for a range between +5° and −5° with respect to the horizontal. A light intensity of 240 cd is required for a range between +/−5° and +/−10° with respect to the horizontal. A light intensity of 80 cd is required for a range between +/−10° and +/−20° with respect to the horizontal. A light intensity of 40 cd is required for a range between +/−20° and +/−30° with respect to the horizontal. A light intensity of 20 cd is required for a range between +/−30° and +/−75° with respect to the horizontal. These required values may be absolute values or effective light intensity values which take into account the observer's perception, as discussed above.
(44) The exemplary predefined navigation mode light intensity distribution 82 requires the following minimum light intensity values in the vertical cross-sectional plane. A light intensity of 20 cd is required in the principal light emission direction, i.e. in the horizontal. A light intensity of 18 cd is required for a range between 0° and +/−5° with respect to the horizontal. A light intensity of 16 cd is required for a range between +/−5° and +/−10° with respect to the horizontal. A light intensity of 14 cd is required for a range between +/−10° and +/−15° with respect to the horizontal. A light intensity of 10 cd is required for a range between +/−15° and +/−20° with respect to the horizontal. A light intensity of 6 cd is required for a range between +/−20° and +/−30° with respect to the horizontal. A light intensity of 2 cd is required for a range between +/−30° and +/−40° with respect to the horizontal. A light intensity of 1 cd is required for a range between +/−40° and +/−90° with respect to the horizontal.
(45) FIG. 6B shows the predefined anti-collision mode light intensity distribution and the predefined navigation mode light intensity distribution of FIG. 6A, scaled to a normalized peak intensity. In particular, the predefined anti-collision mode light intensity distribution 80 of FIG. 6B is the same as in FIG. 6A.
(46) However, the scaled version 82a of the predefined anti-collision mode light intensity distribution 82 is the predefined navigation mode light intensity distribution 82 of FIG. 6A multiplied by the factor 20. The factor 20 stems from the fact that the peak intensity of the predefined anti-collision mode light intensity distribution 80 is 20 times as high as the peak intensity of the predefined navigation mode light intensity distribution 82. As can be seen from FIG. 6B, the predefined anti-collision mode light intensity distribution 80 and the scaled version 82a of the predefined navigation mode light intensity distribution 82 have the same peak intensity of 400 cd.
(47) In FIG. 6C, a compound light intensity distribution 84 is shown, which is the result of a combination of the predefined anti-collision mode light intensity distribution 80 and the scaled version 82a of the predefined navigation mode light intensity distribution 82. The compound light intensity distribution 84 is derived from the light intensity distributions 80 and 82a in such a way that the more restrictive requirement of the two light intensity distributions is chosen for each angle. In other words, the compound light intensity distribution 84 is derived by tracing the respectively upper one of the two light intensity distributions 80 and 82a along the angular axis. This compound light intensity distribution 84 has a very particular property. If a light unit emits light with the compound light intensity distribution 84, said light unit satisfies the FAR requirements for an anti-collision light. Moreover, if a light unit emits the compound light intensity distribution 84, with the intensity values over all angles being divided by 20, the light unit satisfies the FAR requirements for a navigation light. Accordingly, the compound light intensity distribution 84 has a shape that, when scaled properly, satisfies both the predefined anti-collision mode light intensity distribution 80 and the predefined navigation mode light intensity distribution 82. In other words, the compound light intensity distribution 84 is an example of a relative output light intensity distribution that is suitable for both an anti-collision light and a navigation light according to the FAR.
(48) Based on these consideration, the at least one first optical system 12 has such a design that it transforms the light intensity distribution of the at least one first light source 10, which may for example be Gaussian or Lambertian for the at least one first light source 10 being a single LED, into a signalling output light intensity distribution that satisfies the relative requirements of the compound light intensity distribution 84. The satisfaction of the absolute predefined anti-collision mode light intensity distribution 80 and the predefined navigation mode light intensity distribution 82 is then achieved via a scaling of the light intensity output by at least one first light source 10. This light intensity is in turn controlled by the illumination current flown through the at least one first light source in operation.
(49) FIG. 7 shows three light intensity sequences over time, implementing a navigation mode of operation, an anti-collision mode of operation, and a combined mode of operation. With respect to the light intensity distributions of FIG. 6, which show the distributions in the vertical plane, the intensity value at the angle of 0° is shown in FIG. 7. In other words, the intensity values shown in FIG. 7 are the light intensities emitted by the at least one first light source in a horizontal direction.
(50) FIG. 7A shows a first light intensity course over time. The first light intensity course has a constant value of 20 cd. In this way, the first light intensity course is in accordance with the requirements of the navigation mode of operation, which requires a continuous output of light. Also, the value of 20 cd is in accordance with the peak value of the predefined navigation mode light intensity distribution 82, shown in FIG. 6A.
(51) FIG. 7B shows a second light intensity course over time. The second light intensity course has a pulsed shape. It comprises a sequence of equally high, equally long pulses that are separated by intervals of no light being emitted. In this way, the second light intensity course is in accordance with the requirements of the anti-collision mode of operation, which requires a sequence of light pulses, also referred to as a sequence of light flashes or a strobe operation. In the exemplary embodiment of FIG. 4B, the pulses are rectangular pulses. The intervals of no light being emitted are as long as the pulse lengths. The pulse shape, the pulse length, and the length between the pulses may have any suitable form/value. The light intensity value of 400 cd, which is present during the pulses, is in accordance with the peak value of the predefined anti-collision mode light intensity distribution 80, shown in FIG. 6A.
(52) FIG. 7C shows a third light intensity course over time. The third light intensity course is a combination of the first light intensity course and the second light intensity course in such a way that the light intensity values along the third light intensity course correspond to the respectively higher value of the first light intensity course and the second light intensity course, shown in FIGS. 7A and 7B. In particular, the pulses of the third light intensity course correspond to the pulses of the second light intensity course. However, during the intervals between the pulses, the light intensity of the third light intensity course is at 20 cd. In this way, the light intensity between the pulses corresponds to the continuous light intensity of the first light intensity course. As a minimum light intensity of 20 cd is ensured at all times in the third light intensity course, the combined mode satisfies the FAR requirements for a navigation light. Further, with the light pulses having a light intensity of 400 cd, the combined mode also satisfies the FAR requirements for an anti-collision light.
(53) The light intensity during the pulses of the second light intensity course and the third light intensity course, shown in FIGS. 7B and 7C, is subject to various considerations. On the one hand, the light intensity may be right in accordance with the desired light intensity distribution. This is shown in FIG. 7 with respect to the exemplary predefined anti-collision mode light intensity distribution of FIGS. 6A and 6B and the exemplary compound light intensity distribution of FIG. 6C. On the other hand, the light intensity value may be scaled to account for the different perceptions of light pulses of different lengths. The correction factor may be calculated with the Blondel Rey equation, known to the skilled person. An illustrative example is given as follows. Light pulses with a length of 200 ms are perceived with a lower light intensity. In particular, the Blondel Rey equation says that a pulse of 200 ms is perceived half as bright as its actual intensity value. Accordingly, in an exemplary embodiment, the light pulses of FIGS. 7B and 7C may have a length of 200 ms and may have a light intensity value of 800 cd.
(54) FIG. 8 illustrates an aircraft 110, namely an airplane, in accordance with an exemplary embodiment of the invention in an upper perspective view, the aircraft 110 being equipped with an exterior aircraft light 101 in accordance with an exemplary embodiment of the invention. In the depicted arrangement, the exterior aircraft light 101 is mounted on the fuselage 100 between the vertical stabilizer 104 and the horizontal stabilizer 102. The aircraft 110 and the exterior aircraft light 101 may correspond to the aircraft 110 and the first exterior aircraft light 101 of FIG. 1, only shown in a perspective view. Accordingly, the aircraft 110 may also have the second, third, and fourth exterior aircraft lights 201, 301, 401 of FIG. 1, which are blocked from view due to the perspective of FIG. 8.
(55) The longitudinal axis of the exterior aircraft light 101 may be parallel to the longitudinal axis of the fuselage 100, or the longitudinal axis of the exterior aircraft light 101 may be skewed relative to the longitudinal axis of the fuselage 100. The exterior aircraft light 101 is substantially arranged in a front-to-rear direction of the airplane 110.
(56) FIG. 9 shows the aircraft 110 of FIG. 1 in the same rear view for illustrating the illumination of the left side of the vertical stabilizer 104 by the first exterior aircraft light 101. In order not to overcrowd FIG. 9, only said first exterior aircraft light 101 is shown. It is understood that the second, third, and fourth exterior aircraft lights 201, 301, 401 may also be present. The first exterior aircraft light 101 is mounted on the fuselage 100 between the vertical stabilizer 104 and the left horizontal stabilizer 102 near the tail of the fuselage 100 aft of the left wing 103.
(57) FIG. 9 further shows a normal direction 108, off which the exterior aircraft light 101 irradiates the vertical stabilizer 104 at an angle φ, relative to the normal direction 108. In the exemplary embodiment of FIG. 9, the exterior aircraft light 101 provides illumination in an angular illumination range of from φ=30° to φ=80°. This can also be expressed as the exterior aircraft light 101 having a stabilizer illumination opening angle χ of 50° towards the vertical stabilizer. The normal direction 108 and the angles φ and χ are depicted in a viewing direction straight from the rear of the aircraft 110 in FIG. 9. It is also valid to define said parameters in a cross-sectional plane through the exterior aircraft light 101 orthogonal to the longitudinal extension thereof. It is further also valid to define said parameters with respect to a tangential plane to a top of the exterior aircraft light 101, in particular when the housing of the exterior aircraft light 101 has a rounded lens cover, as described below. The given angles φ and χ may apply to one or more or all cross-sections through the exterior aircraft light 101.
(58) It is pointed out that above described angular illumination range of from φ=30° to φ=80° is exemplary only. It is apparent that this range may be adapted, depending on the size of the vertical stabilizer 104, the distance between the vertical stabilizer 104 and the exterior aircraft light 101, and the curvature of the fuselage in the tail portion thereof. In particular, the angular illumination range may become smaller, the larger the distance to the vertical stabilizer 104 is and the farther the exterior aircraft light 101 is positioned downwards on the arc towards the horizontal stabilizer 102. For example, the angular illumination range may be from φ=35° to φ=70° or from φ=45° to φ=60°. It is pointed out that the expression of the angular illumination range being from φ=30° to φ=80° does not mean that illumination is exclusively present in this angular range. It rather means that illumination is at least present in the given angular range. Stray light outside of said range is not excluded by the given terminology.
(59) It is further apparent that above described angular illumination range and, thus, the stabilizer illumination opening angle, may have different values, depending on the stabilizer to be illuminated. In particular, exterior aircraft lights with different stabilizer illumination opening angles may be used for illuminating the sides of the vertical stabilizer and the undersides of the horizontal stabilizers.
(60) FIG. 10 shows an exterior aircraft light 101 in accordance with an exemplary embodiment of the invention in a cross-sectional view. The cross-sectional view is orthogonal to the longitudinal extension of the exterior aircraft light 101 and cuts through one of the second light sources 20. The exterior aircraft light 101 may be the first exterior aircraft light 101 of the previous Figures.
(61) The exterior aircraft light 101 has a housing 2, which comprises a mounting structure 4 and a lens cover 6. In the depicted exemplary embodiment, the mounting structure 4 is a fuselage mounting plate, having substantially even upper and lower faces. The mounting plate has a width W in the depicted cross-section and in other cross-sections. The fuselage mounting plate 4 has substantially rectangular upper and lower faces. The lens cover 6 has a semi-tube-like shape. It is arranged on the mounting structure 4 and creates an inner space between the mounting structure 4 and the lens cover 6. The lens cover 6 is made from highly resistant transparent or translucent material. In particular, the lens cover 6 may be resistant to wide temperature variations, particle strikes, and hydraulic fluids, as described above. The mounting structure 4 and the lens cover 6 together have the height H.
(62) The exterior aircraft light 101 has a plurality of second light sources 20, with one of them being arranged and shown in the cross-sectional plane of FIG. 10. The plurality of second light sources 20 are arranged in a linear manner on the mounting structure 4 along the longitudinal extension of the exterior aircraft light 101. The other second light sources are arranged in front of and behind the drawing plane of FIG. 9. In the exemplary embodiment of FIG. 9, the second light sources 20 are second LEDs.
(63) Each of the second light sources 20 is provided with a second optical system 22 for directing the light of the respective second light source 20 towards the vertical stabilizer of the aircraft. In the exemplary embodiment of FIG. 9, the second optical system 22 has a collimating reflector 24 and a collimating lens 26. The collimating reflector 24 is shaped to collimate the light from the second light source 20 substantially towards the tip of the vertical stabilizer. As the tip of the vertical stabilizer is the region of the vertical stabilizer that is farthest removed from the exterior aircraft light 101, a high light intensity in the direction of the tip is desired. In the exemplary embodiment of FIG. 9, the collimating reflector 24 is parabolic and is shaped like a partial cup, in particular like a cup having a sector towards the vertical stabilizer cut out. For shaping the light not affected by the collimating reflector 24, the collimating lens 26 is provided. The collimating lens 26 is arranged to affect the light leaving the second light source 20 towards the top and towards the cut-out portion of the collimating reflector 24. The collimating lens 26 is a custom-shaped lens that distributes the captured light over the vertical stabilizer. The light leaving the collimating lens 26 has a smaller angular range in the depicted cross-sectional plane than the light hitting the collimating lens 26. Hence, the collimating lens 26 is referred to as collimating. It is pointed out, however, that any kind of second optical system may be employed that effectively distributes the light from the second light source 20 over the stabilizer to be illuminated, in particular over the full height of the vertical stabilizer/full width of the horizontal stabilizer in at least a vertical/horizontal corridor thereof. The shaping of the light intensity distribution for illuminating the stabilizer by the second optical system 22 is illustrated by a plurality of exemplary light rays.
(64) The mounting structure 4 is attached to the outer skin 100a of the fuselage 100. It is also possible that the exterior aircraft light 101 is partially sunk into a corresponding recess in the fuselage 100. In the latter case, the lens cover may be shaped to be flush with the outer skin 100a of the fuselage 100 where the light from the second light sources 20 leaves the exterior aircraft light 101.
(65) FIG. 11 shows an aircraft 110 in accordance with an exemplary embodiment of the invention, equipped with an exterior aircraft light 101 in accordance with an exemplary embodiment of the invention. In particular, FIG. 11 shows, in an upper perspective view, a tail portion 105 of the fuselage 100 and illustrates the width W and the length L of the exterior aircraft light 101, which has a displacement D along the circumferential arc from the vertical stabilizer 104. Again, for illustrative purposes, only one exterior aircraft light 101 is shown in a schematic view. It is understood that further exterior aircraft lights in accordance with exemplary embodiments of the invention, such as described herein, may be provided.
(66) FIG. 11 shows the illumination distribution 104a on the vertical stabilizer 104, when illuminated by the exterior aircraft light 101. Unlike a conically outwardly fading illumination of customary aircraft vertical stabilizer illumination lights, the present illumination pattern 104a exhibits a high degree of uniformity of illumination of the vertical stabilizer 104. In particular, the vertical stabilizer may experience a highly uniform illumination of at least 100 1×. The illumination patterns created by the light from the second light sources of the exterior aircraft lights in accordance with exemplary embodiments of the invention may not be centered around a point, due to the plurality of second light sources 20, but provide a highly homogeneous illumination.
(67) While the invention has been described with reference to exemplary embodiments, 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. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.
