Exterior aircraft light unit and method of disabling a light output of an exterior aircraft light unit

Abstract

An exterior aircraft light unit includes a power input coupleable to an aircraft on-board power supply; at least one LED coupled to the power input for receiving power from the aircraft on-board power supply and configured to emit a light output; an optical sensor arranged for sensing an intensity detection portion of the light output and configured to output a detection signal indicative of an intensity level of the light output; an end of life detector, coupled to the optical sensor for receiving the detection signal and configured to determine an end of life condition; and a fuse circuit coupled to the end of life detector; wherein the fuse circuit is configured to irreversibly disable an LED circuit board upon the end of life detector communicating the end of life condition to the fuse circuit.

Claims

1. An exterior aircraft light unit, comprising: a power input coupleable to an aircraft on-board power supply, at least one LED coupled to the power input for receiving power from the aircraft on-board power supply and configured to emit a light output, an optical sensor arranged for sensing an intensity detection portion of the light output and configured to output a detection signal indicative of an intensity level of the light output, an end of life detector, coupled to the optical sensor for receiving the detection signal and configured to determine an end of life condition, and a fuse circuit coupled to the end of life detector, wherein the at least one LED, the optical sensor and the fuse circuit are arranged on an LED circuit board and wherein the fuse circuit is configured to irreversibly disable power reception at the LED circuit board upon the end of life detector communicating the end of life condition to the fuse circuit.

2. The exterior aircraft light unit according to claim 1, wherein the fuse circuit comprises a one time settable latch.

3. The exterior aircraft light unit according to claim 1, wherein the end of life detector is configured to determine the end of life condition if the detection signal indicates that the intensity level of the light output is below a set threshold value.

4. The exterior aircraft light unit according to claim 3, wherein the end of life detector comprises a timer circuit and wherein the end of life detector is configured to determine the end of life condition if the detection signal indicates that the intensity level of the light output is below the set threshold value for a set time interval.

5. The exterior aircraft light unit according to claim 3, further comprising a temperature sensing circuit configured to sense an operating temperature of the at least one LED, wherein the temperature sensing circuit is coupled to the end of life detector and wherein the end of life detector is configured to determine the end of life condition only if the operating temperature of the at least one LED, sensed by the temperature sensing circuit, is below a normal operation threshold value.

6. The exterior aircraft light unit according to claim 5, wherein the temperature sensing circuit is arranged on the LED circuit board.

7. The exterior aircraft light unit according to claim 1, wherein the optical sensor is arranged on the LED circuit board.

8. The exterior aircraft light unit according to claim 1, further comprising a time of use recorder configured to record an aggregate operation time of the at least one LED, wherein the time of use recorder is coupled to the end of life detector and is configured to communicate the aggregate operation time to the end of life detector, with the time of use recorder in particular being arranged on the LED circuit board.

9. An LED circuit board for use in an exterior aircraft light unit, LED circuit board comprising: at least one LED configured to emit a light output, and an optical sensor arranged for sensing an intensity detection portion of the light output and configured to output a detection signal indicative of an intensity level of the light output; and a fuse circuit configured to irreversibly disable power reception at the LED circuit board upon receiving an end of life condition signal indicating an end of life condition of the at least one LED; wherein the LED circuit board is coupleable to a power input for receiving power from an aircraft on-board power supply.

10. The exterior aircraft light unit according to claim 1 in combination with a an aircraft that includes an on-board power supply coupled to the unit and wherein the one exterior aircraft light unit is arranged in an outer portion of the aircraft for lighting an outside environment of the aircraft.

11. A method of disabling a light output of an exterior aircraft light unit upon detection of an end of life condition, with the exterior aircraft light unit having at least one LED arranged on an LED circuit board, the method comprising: operating the at least one LED for emitting the light output; sensing an intensity level of the light output using an optical sensor which is arranged on the LED circuit board; determining the end of life condition on the basis of the intensity level of the light output; and irreversibly disabling power reception at the LED circuit board upon determining the end of life condition.

12. A method according to claim 11, wherein determining the end of life condition comprises determining the end of life condition if the intensity level of the light output is below a set threshold value for a set time interval.

13. A method according to claim 11, wherein the step of determining the end of life condition comprises: sensing an operating temperature of the at least one LED; and determining the end of life condition only if the operating temperature of the at least one LED is below a normal operation threshold value.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) Further exemplary embodiments of the invention are described in detail with respect to the accompanying figures, wherein:

(2) FIG. 1 shows an aircraft in accordance with an exemplary embodiment of the invention in a top view, the aircraft being equipped with a plurality of exterior aircraft light units in accordance with exemplary embodiments of the invention;

(3) FIG. 2 shows a block diagram of an exterior aircraft light unit in accordance with an exemplary embodiment of the invention;

(4) FIG. 3 shows a circuit diagram of an LED circuit board, with the LED circuit board being usable in exterior aircraft light units in accordance with exemplary embodiments of the invention;

(5) FIG. 4 shows selected components of an exterior aircraft light unit in accordance with an exemplary embodiment of the invention in a cross-sectional view.

DETAILED DESCRIPTION

(6) FIG. 1 shows an aircraft 100 in accordance with an exemplary embodiment of the invention in a top view. The aircraft 100 of FIG. 1 is a large commercial airplane, such as a passenger airplane or a cargo airplane. The aircraft 100 has an aircraft on-board power supply 40. The on-board power supply 40 is a power supply network that provides power to a variety of different devices in the aircraft 100. For illustrative purposes, the aircraft on-board power supply 40 is depicted as a set of power lines running along the fuselage of the aircraft 100 and running along the wings of the aircraft 100. The aircraft on-board power supply 40 is a 115 V/400 Hz power distribution network in the exemplary embodiment of FIG. 1.

(7) The aircraft 100 has a plurality of exterior aircraft light units in accordance with exemplary embodiments of the invention. For illustrative purposes, five exterior aircraft light units are depicted in FIG. 1. In particular, the aircraft 100 has an upper beacon light unit 2-1, which is mounted to the top of the fuselage of the aircraft 100, a lower beacon light unit 2-2, which is mounted to the bottom portion of the fuselage of the aircraft 100, a left wing tip navigation light unit 2-3, which is mounted to the wing tip of the left wing of the aircraft 100, a right wing tip navigation light unit 2-4, which is mounted to the wing tip of the right wing of the aircraft, and a tail navigation light unit 2-5, which is mounted to the tail of the fuselage of the aircraft 100. It is understood that these exterior aircraft light units are exemplary in nature and that the aircraft 100 may have various further exterior aircraft light units, such as white flashing anti-collision light units, wing and engine scan light units, take-off, landing, taxiing and runway turn-off light units, logo light units, etc.

(8) FIG. 2 shows an exterior aircraft light unit 2 in accordance with an exemplary embodiment of the invention in a block diagram. The general structure and working principle of the exterior aircraft light unit 2, which will be described below, may be applied to all of the five illustrated exterior aircraft light units of FIG. 1 as well as to other exterior aircraft light units, as described above.

(9) The exterior aircraft light unit 2 has a power input 4, consisting of two power lines, for coupling the exterior aircraft light unit 2 to the aircraft on-board power supply 40, as illustrated in FIG. 1. Further, the exterior aircraft light unit 2 has a communication terminal 6 for exchanging data with the remainder of the aircraft, such as for exchanging data with the board computer of the aircraft.

(10) The exterior aircraft light unit 2 has a power conditioning and control module 8. The power conditioning and control module 8 in turn comprises a power input and communication filter 82, which may include an electromagnetic interference filter, a power factor correction circuit 84, an LED driver circuit 86, and an auxiliary power circuit 88.

(11) The exterior aircraft light unit 2 further comprises an LED circuit board 10. Arranged on the LED circuit board 10, there are provided an LED chain 12, a temperature sensing circuit 14, an optical sensor 16, a fuse circuit 18, and a time of use recorder 20. Yet further, the exterior aircraft light unit 2 comprises an end of life detector 30.

(12) Above mentioned components are coupled to each other as follows. The power input 4 is coupled to the power input and communication filter 82, which in turn is coupled to the power factor correction circuit 84 via two power lines, which in turn is coupled to the LED driver circuit 86 via two power lines. Further, the power input and communication filter 82 is coupled to the communication terminal 6 for exchanging data with the outside of the exterior aircraft light unit 2. Also, the power input and communication filter 82 is coupled to the end of life detector 30 via a communication line for receiving status information about the end of life condition of the exterior aircraft light unit 2.

(13) The power factor correction circuit 84 is coupled to the auxiliary power circuit 88 via a power line. Further, the auxiliary power circuit 88 is coupled to the end of life detector 30 as well as to the temperature sensing circuit 14, the optical sensor 16, the fuse circuit 18, and the time of use recorder 20 via an auxiliary power distribution network 52.

(14) The LED driver circuit 86 is coupled to the LED chain 12 via two LED power lines 51. The LED driver circuit 86 is further coupled to the temperature sensing circuit 14 and the end of life detector 30 via a temperature communication line 54. The end of life detector 30 is further coupled to the optical sensor 16 via an intensity communication line 56. The end of life detector 30 is further coupled to the fuse circuit 18 via an end of life communication line 58. The end of life detector 30 is further coupled to the time of use recorder 20 via a time of use communication line 60.

(15) The operation of the exterior aircraft light unit 2 is described as follows. Upon the reception of an according on-command over communication terminal 6, the LED chain 12 is provided with power from the aircraft on-board power supply for emitting a light output. In particular, the power input and communication filter 82, the power factor correction circuit 84, and the LED driver circuit 86 provide power to the LED chain 12 in a suitable form. Further in particular, said power is filtered for electromagnetic interference by the power input and communication filter 82, is power factor corrected in the power factor correction circuit 84, and is conditioned to a suitable current level in the LED driver circuit 86. Further, operating power is provided to the end of life detector 30, to the temperature sensing circuit 14, to the optical sensor 16, to the fuse circuit 18, and to the time of use recorder 20 via the auxiliary power circuit 88.

(16) During normal operation of the exterior aircraft light unit 2, the LED chain 12 constantly emits the light output for lighting an outside environment of the aircraft. At the same time, the temperature sensing circuit 14 senses a temperature indicative of the operating temperature of the LED chain 12. Further at the same time, the optical sensor 16 senses an intensity level of the light output by sensing an intensity detection portion of the light output of the LED chain 12. Further at the same time, the end of life detector 30 continuously compares said intensity level of the light output to a set threshold value. Yet further at the same time, the time of use recorder 20 continuously counts the operating time of the LED chain 12. After the exterior aircraft light unit 2 is shut down and re-started, the time of use recorder 20 starts its counting operation at the value of the previous shut-down, such that an aggregate operation time is counted by the time of use recorder 20. The time of use recorder 20 continuously or periodically communicates the aggregate operation time to the end of life detector 30 via the time of use communication line 60.

(17) In the exemplary embodiment of FIG. 2, the temperature sensing circuit 14 continuously communicates the operating temperature of the LED chain 12 to the end of life detector 30 and to the LED driver circuit 86 via the temperature communication line 54. The LED driver circuit 86 is configured to adapt the current provided to the LED chain 12 via the LED power lines 51 depending on the operating temperature. In this way, a temperature-compensated operation of the LED chain 12 may be achieved, which allows for a constant light output, as long as the aging of the LED aging does not become significant. It is also possible to actively decrease the current to the LED chain 12 at very high operating temperatures for self-protection.

(18) Next, the operation of the exterior aircraft light unit 2 is described for the situation that the end of life detector 30 determines that the intensity level of the light output, as indicated by the signal from the optical sensor 16, is below the set threshold value. The set threshold value may be a percentage value of the normal light intensity of the exterior aircraft light unit, such as 50% of the original output light intensity upon going into service.

(19) When the end of life detector 30 determines that the intensity level of the light output is below the set threshold value, it starts a timer circuit. This timer circuit, which may be set to a value somewhere between 10 s and 30 min, ensures that the intensity level must be below the set threshold value for the set time, in order for a further action to take place. In other words, the end of life detector 30 checks if the intensity level of the light output is below the set threshold value for the time set in the timer circuit. If the intensity level of the light output rises above the set threshold value, the timer is re-set and is re-started upon a subsequent falling of the intensity level below the set threshold value.

(20) At the same time, the end of life detector 30 monitors the operating temperature of the LED chain 12, as provided by the temperature sensing circuit 14 via the temperature communication line 54. In particular, the end of life detector 30 compares the operating temperature to a normal operation threshold value. If the operating temperature is below the normal operation threshold value and the intensity level of the light output of the LED chain 12 is below the set threshold value for the set time interval set by the timer circuit, the end of life detector 30 determines an end of life condition. If the operating temperature is above the normal operation threshold value, no end of life condition is determined.

(21) Upon determining an end of life condition, the end of life detector 30 communicates an according signal to the power input and communication filter 82 for communicating said end of life condition to the outside of the exterior aircraft light unit 2 via the communication terminal 6. Further, the end of life detector 30 signals the end of life condition to the fuse circuit 18 via the fuse communication line 58.

(22) Upon receiving the signal indicating the end of life condition, the fuse circuit 18 irreversibly disables the LED circuit board 10. In particular, the fuse circuit 18 disables the operation of the LED chain 12, the temperature sensing circuit 14, the optical sensor 16, and the time of use recorder 20. In a particular embodiment, the fuse circuit 18 irreversibly interrupts the power lines 51 to the LED chain 12 as well as according portions of the auxiliary power distribution network 52 to the temperature sensing circuit 14, the end of life detector 16, and the time of use recorder 20. It is also possible that the fuse circuit 18 does not interrupt the power to these devices, but that it sends an according irreversible control signal to the respective control logics associated with these components.

(23) The disabling of the LED circuit board 10 is permanent and cannot be reversed without replacing the LED circuit board 10. In particular, irrespective of what ensuing signal is provided on the fuse communication line 58, the fuse circuit 18 does not reverse its control action of disabling the LED circuit board 10.

(24) The exterior aircraft light unit 2 may also be operated in a test mode to test the functioning of the end of life procedure without actually disabling the LED circuit board 10. In particular, it may be possible to interrupt the fuse communication line 58, to operate the LED driver circuit 86 to provide a current to the LED chain 12 that results in a light output with an intensity level below the set threshold value, and to monitor the signalling of the end of life condition by the end of life detector 30 to the power input and communication filter 82. It is also possible that an optical indicator is provided instead of/in addition to said signalling to the power input and communication filter 82. In this way, the functioning of the end of life determination may be tested, without irreversibly disabling the LED circuit board 10. It is also possible that the optical indicator, such as an indicator LED, lights up when the end of life detector 30 determines that the intensity level of the light output is below the set threshold value, irrespective of the operation of the associated timer circuit and the operating temperature monitoring. In this way, the functioning of the optical sensor 16 can be tested quickly without carrying out the full end of life procedure and without irreversibly disabling the LED circuit board 10.

(25) FIG. 3 shows an exemplary circuit implementation of the LED circuit board 10 of FIG. 2. Out of the LED chain 12, five exemplary LEDs are shown. However, a greater or smaller number of LEDs may be provided in the exterior aircraft light unit 2. The operating temperature sensor 14 and the optical sensor 16 are provided in close proximity to the LED chain 12 for an accurate sensing of the operating temperature and the light intensity of the light output. The time of use recorder 20 may count the operating time whenever power is provided to it, assuming that the auxiliary power distribution network 52 is powered up at the same time as the LED power lines 51. It is also possible that the time of use recorder 20 comprises a sensor capable of detecting current flow in the adjacent LED power line 51 and records the time of said power flow.

(26) The fuse circuit 18 has a disabling output 62. This disabling output 62 controls a first switch 64, arranged in one of the two LED power lines 51, as well as a second switch 66, arranged in the auxiliary power distribution network 52. By opening the first and second switches 64, 66, the power provision to the LED chain 12, the temperature sensing circuit 14, the optical sensor 16, and the time of use recorder 20 is interrupted. In FIG. 3, this state of power interruption is depicted. It is again pointed out that this state of power interruption, as depicted in FIG. 3, is not reversible. In other words, the fuse circuit 18 does not provide a command for closing the first and second switches 64, 66 again. In order to implement this functionality, the fuse circuit 18 may be a one time settable latch or flip-flop.

(27) In order to bring the exterior aircraft light unit 2 back into service, the LED circuit board 10 is to be replaced with a new LED circuit board, having new LEDs whose light output is above the light output requirements.

(28) FIG. 4 shows selected components of an exterior aircraft light unit 2 in accordance with an exemplary embodiment of the invention in a cross-sectional view. In particular, the LED circuit board 10 is shown, which carries a single LED 12 in the exemplary embodiment of FIG. 4. The single LED 12 is associated with a lens 22 that shapes a desired output light intensity distribution of the exterior aircraft light unit 2. In the exemplary embodiment of FIG. 4, the exterior aircraft light unit 2 is a forward navigation light unit, with arrow 110 indicating the forward direction of the aircraft. The light leaving the LED 12 is referred to as light output. The light leaving the lens 22 and contributing to the output light intensity distribution of the exterior aircraft light unit 2 is referred to as useful light output portion 26, illustrated by various exemplary light rays in FIG. 4.

(29) Towards the right of the lens 22, a surface of total internal reflection is provided, which generates a strong output peak in the forward direction 110. However, this surface of total internal reflection is imperfect, such that few light rays exit the lens 22 there. These light rays are part of the non-useful light output portion of the exterior aircraft light unit 2. Further, these exemplary light rays form the intensity detection portion 28 of the light output in the exemplary embodiment of FIG. 4. The intensity detection portion 28 is redirected towards the optical sensor 16 by a reflector 24. As the intensity detection portion 28 is stray light that does not contribute to the useful light output of the exterior aircraft light unit 2, the intensity sensing by the optical sensor 16 does not hurt the overall efficiency of the exterior aircraft light unit 2.

(30) 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.