GB1585518A - Supervisory arrangements for airfield landing light installations - Google Patents

Description

(54) SUPERVISORY ARRANGEMENTS FOR AIRFIELD LANDING LIGHT INSTALLATIONS (71) We, MILLTGAN ELECTRONICS LIMITED, a British company of Tolworth Close, Surbiton, Surrey KT6 7ER, formerly of 36 Clapham Crescent, London, S.W.4., do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to supervisory arrangements for airfield landing light installations.

In the operation of airfields used for aircraft movements at night it is necessary to provide large numbers of lamps arranged to illuminate the runway. Because of the large distances involved it is impossible to effect useful visual supervision of such installations from a central control point and although some indication of lamp operation is obtainable by observing the current drain in the various lamp circuits this gives only a general and inaccurate picture of the actual state of affairs.

The present invention provides a means whereby there may be obtained a knowledge of the state of operation or malfunction of each runway lamp, or of as many of these as is desired by means not requiring the provision of a wire circuit from each supervised lamp to the central point.

According to the present invention there is provided runway lighting supervisory apparatus including means arranged to respond to light emitted by a runway lamp by developing a radio frequency signal denotive of lamp performance, means for transmitting said radio frequency signal to a position remote from said lamp and means at said position responsive to said signal for producing a further signal in the event of lamp failure.

Embodiments of the invention may be devised to suit particular circumstances and operational requirements of specific airfields. Several such embodiments will now be briefly described.

In one embodiment of the invention each runway lamp to be supervised has associated with it a very low-power radio transmitter that may be powered by a solar cell exposed to the light of the lamp. An appropriately positioned antenna receives the signals radiated by each lamp transmitter and because means later described are provided whereby the signals from the respective lamp transmitters received on the aerial may be individually distinguished it is thus possible to determine from the received signals which, if any, runway lamps are not operating in a desired manner.

The invention will now be described with reference to embodiments thereof each embodiment being illustrated by one figure of the accompanying drawings, comprising Figures 1 to 6.

Figure 1 shows two runway lights 11, 12, though in practice there will be many more lights to be supervised. Each of runway lights 11, 12 is provided with a brightness monitor 20, 30 respectively including a solar cell 21, 31 exposed to the light of the lamp.

The brightness motor also includes a radio transmitter 22, 32 causing a radio-frequency signal to be radiated from an antenna 23, 33 when the respective light is operating correctly. As it is usual for such lights to be arranged to be operated at different levels of brightness, to suit differing ambient conditions, it is usually advantageous to arrange that transmitter 22, 32 delivers a radio-frequency signal modulated in a manner representative of the lamp brightness. The signals from the transmitters 22, 32, radiated by antennae 23, 33 are received by a monitoring apparatus 40 including a receiving antenna 41, the signals received by which are applied to a receiver 42 by which the received signals are demodulated to derive respective signals representative of the individual lamp brightnesses and these signals are used to actuate a warning device in the event of lamp failure.For this purpose the received and demodulated signals are applied in this embodiment to a monitor device 43 arranged to provide a visual display denotive of the fact that a lamp has failed, when this is the case, and preferably also arranged to provide an indication denotive of the identity or location of the lamp which has failed.

In the simplest manner of operation, which may be assumed to be that employed in the apparatus of Figure 1, each lamp radiates a radio frequency signal of a respective individual frequency and having an amplitude related to the lamp brightness.

In this case the identity of a failed lamp may be determined by circuits arranged to provide an appropriately identifyable display if the amplitude of the signal received from a particular light does not correspond to the intended lamp brightness as notified to the circuitry by an appropriate signal from the lamp brightness control means.

In many cases, however, it is not convenient to use individual radio frequencies for each individual monitored lamp, of which there may be very large numbers.

Figure 2 illustrates an arrangement in which a substantial restriction of the necessary total frequency band is possible. In this arrangement there are seen individual runway lamps numbered 11 to 18, these being representative only of the large numbers found in practice. Each of a plurality of sets of lamps is allocated a common frequency band, and each lamp of the set is allocated an individual frequency within that band.

For simplicity in explanation it is assumed in the illustrated embodiment that each set, of which two only are shown, comprises four lamps, though in practice the number of sets using a common frequency band and the number of lamps in a set, and therefore of individual frequencies, will be much larger. Thus a first set includes lamps 11 to 14 and a second set comprises lamps 15 to 18.

Lamps 11 and 15 each transmit a signal of a radio frequency fl, lamps 12 and 16 radiate signals of frequency f2, lamps 13 and 17 signals of frequency f3 and lamps 14 and 18 signals of frequency f4. The radiated signals are of very low power and it is convenient to arrange that sets of lamps 11-14 and 15-18 using common frequency bands are in fact spaced relatively far apart. Thus an antenna 41a arranged to receive the signals from lamps 11-14 will in practice be so far removed from the lamps 15-18 that the signals from those lamps may be excluded by a simple limited circuit in the receiver. For the same reason, signals from lamps 11-14 will not be effectively received by the receiver 41b arranged to receive the signals of lamps 15-18.Similar receivers 42a, 42b respond to the signals received on the antenna 41a, 41b, respectively, and provide signals over individual radio or wire channels to a monitor and display unit 43 which provides the required indicatings of lamp failure.

The arrangements described above are disadvantageous in requiring that each of a plurality of lamps shall be provided with a transmitter radiating a signal on an in dividual relatively accurately predetermined frequency, which in the event of a trans mitter requiring replacement necessitates individual tuning of the replacement trans mitter.

An arrangement considerably more con venient in this respect is illustrated by Figure 3, where a series of lamps 11, 12 (n- 1), (n) all are provided with transmitters radiating on the same radio frequency f.

However the signal radiated by each of the lamp transmitters is modulated with an individual modulation denotive of the respective lamp. Since digital counter and logic circuits are at this time available at little cost, it is preferred that the individual modulations shall comprise binary codings which may denote the lamp identity and, if required its state of operation, that is its brightness condition. The signal received by antenna 41 of the monitoring apparatus is thus modulated with a large plurality of individual codes, which may be arranged in known manner to be individually dis tinguishable from the complex signal received.

The basis of such a system of coded modulation is shown in Figure 4. Digram A in Figure 4 illustrates a transmission interval 50 within which it is possible to transmit and recognise 21 individually binary bits 51. Waveforms B to H illustrate individual distinguishable codes that may be transmitted and received individually and distinguishable during this interval.

Digital means for performing decoding operations of the kind here required are well known and do not require further description. Thus transmission interval 50 may be used to transmit seven lamp signals on the same transmission frequency while the individual signals may be individually identified at a receiver from the combin ation of all the received modulation signals.

Obviously the principle may be extended as required.

Another manner of ensuring that a restricted bandwidth only is required is to employ time-multiplexing, each lamp trans mitter being arranged to be operative only during an individual time-channel. Since an instantaneous reporting of lamp defects is not necessary, provided that no long delay in reporting occurs, and because any simultaneous failure of a large number of lamps may be detected by monitoring the total power drawn by the lamps, it may be convenient to employ simple counting systems driven by the a.-c. supply to establish the individual time-channels during which the lamp transmitters are made operative. The basis of such a system is illustrated by Figure 5, in which the apparatus required at two lamps only is considered.

In Figure 5 an a.-c. supply 59 is applied to the apparatuses 60 and 70 at two lamps.

Each lamp includes a counter 61, 71 driven by 100 Hz pulses derived from the a.-c. supply. Counters 61, 71 from the driven by 100 Hz pulses derived from the a.-c. supply. Counters 61, 71 are each arranged to control a respective bistable trigger or flip-flop 62, 72, which is set by a signal derived when the counter reaches a predetermined, lower state of count and is reset when the counter reaches a predeterminedly higher state of count.

When a flip-flop 62 or 72 is set, it causes transmitter 63 or 73 to radiate from an antenna a signal denotive of lamp operation as monitored by a solar cell 64, 74 exposed to the light of the lamp. The individual transmission intervals thus determined are selected so as not to overlap and are advantageously not immediately consecutive. At a receiver to which the signals are thus transmitted, an appropriate selector means operated by a similar counter, will apply each signal received from an individual lamp during a respective transmission interval to control an appropriate indicating means.

In. a system of the general kindEescribed in these embodiments it is very possible that on relatively frequent occasions a false lamp failure signal will be received, owing to movement of ground vehicles, reflections from aircraft moving down the runway and similar causes. It is therefore advantageous to arrange that a warning signal will be given only when a lamp failure signal is repeatedly received. This may readily be done by providing for each indicator circuit a counter device which must be actuated in response to a lamp failure signal a predetermined number of times before a warning of lamp failure is provided to the operator or supervisor.

ln some cases it may be advantageous to arrange that the radio frequency signals are transmitted from the lamp to the receiving position over the a.-c. leads by which power is supplied to the lamps. Such an arrangement is illustrated by Figure 6, wherein two lamps (not shown) each include a supervisory device 80, 90 comprising a solar cell 81, 91, a radio frequency transmitter 82, 92 and an output transformer 83, 93 by which the output of the transmitter is coupled to an a.-c. supply line 85, to which a receiving transformer 95 couples a receiver 96 that actuates a monitor device 97 as in previous embodiments The radio frequency signals are isolated from the supply mains by a filter 86, indicated as comprising a shunt capacitor and a series inductor, though more complex filters are well known and will be preferred in most applications.

Receivers such as 96 may be provided in each of a plurality of individual lamp control switching positions and their outputs fed by wire or radio to a central control position.

It will be understood that an arrangement in which the radio frequency signals are thus transmitted over a conductor may be operated in any of the manners described above for radiated signals with reference to Figures 2-5.

It is advantageous to arrange that different lamp brightnesses may be indicated to the central control point since runway lamps are commonly operated at different brightnesses in accordance with the ambient lighting. This may be achieved by arranging that predetermined changes in lamp brightness will result in the radiation of appropriately different signals.

Many modifications of the arrangements described above are possible. The low power necessary for the transmitter may be derived by inductive coupling from the a.-c. supply to the lamp, or may be provided by a long-life battery arranged to be connected to supply power to the transmitter only when the lamp is alight by a suitable photoelectric control device.

The signalling arrangements used are preferably arranged to be of a fail-safe nature so that any intrinsic defect in the apparatus will result in a "lamp failed" indication.

When the lamp supervisory device is powered by the light of the lamp itself, then it is apparent that any lamp failure will result in the cessation of the signal from that lamp. If other sources of power are used it is a relatively simple matter to ensure that lamp failure will result in signal cessation, though for the sake of simplicity it may sometimes be preferred to provide a supervisory signal only in response to lamp failure.

It will often be considered unnecessary to supervise each of the very many runway lamps and only a predetermined fraction of the total number of lamps will then be provided with supervisory means. Obviously the supervised lamps will be appropriately spaced to prevent failure of any large number of lamps from being neglected.

WHAT WE CLAIM IS: 1. Runway lighting supervisory apparatus including means arranged to respond to light emitted by a runway lamp by developing a radio frequency signal denotive of lamp performance, means for transmitting said radio frequency signal to a position remote from said lamp and means at said

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (12)

**WARNING** start of CLMS field may overlap end of DESC **. made operative. The basis of such a system is illustrated by Figure 5, in which the apparatus required at two lamps only is considered. In Figure 5 an a.-c. supply 59 is applied to the apparatuses 60 and 70 at two lamps. Each lamp includes a counter 61, 71 driven by 100 Hz pulses derived from the a.-c. supply. Counters 61, 71 from the driven by 100 Hz pulses derived from the a.-c. supply. Counters 61, 71 are each arranged to control a respective bistable trigger or flip-flop 62, 72, which is set by a signal derived when the counter reaches a predetermined, lower state of count and is reset when the counter reaches a predeterminedly higher state of count. When a flip-flop 62 or 72 is set, it causes transmitter 63 or 73 to radiate from an antenna a signal denotive of lamp operation as monitored by a solar cell 64, 74 exposed to the light of the lamp. The individual transmission intervals thus determined are selected so as not to overlap and are advantageously not immediately consecutive. At a receiver to which the signals are thus transmitted, an appropriate selector means operated by a similar counter, will apply each signal received from an individual lamp during a respective transmission interval to control an appropriate indicating means. In. a system of the general kindEescribed in these embodiments it is very possible that on relatively frequent occasions a false lamp failure signal will be received, owing to movement of ground vehicles, reflections from aircraft moving down the runway and similar causes. It is therefore advantageous to arrange that a warning signal will be given only when a lamp failure signal is repeatedly received. This may readily be done by providing for each indicator circuit a counter device which must be actuated in response to a lamp failure signal a predetermined number of times before a warning of lamp failure is provided to the operator or supervisor. ln some cases it may be advantageous to arrange that the radio frequency signals are transmitted from the lamp to the receiving position over the a.-c. leads by which power is supplied to the lamps. Such an arrangement is illustrated by Figure 6, wherein two lamps (not shown) each include a supervisory device 80, 90 comprising a solar cell 81, 91, a radio frequency transmitter 82, 92 and an output transformer 83, 93 by which the output of the transmitter is coupled to an a.-c. supply line 85, to which a receiving transformer 95 couples a receiver 96 that actuates a monitor device 97 as in previous embodiments The radio frequency signals are isolated from the supply mains by a filter 86, indicated as comprising a shunt capacitor and a series inductor, though more complex filters are well known and will be preferred in most applications. Receivers such as 96 may be provided in each of a plurality of individual lamp control switching positions and their outputs fed by wire or radio to a central control position. It will be understood that an arrangement in which the radio frequency signals are thus transmitted over a conductor may be operated in any of the manners described above for radiated signals with reference to Figures 2-5. It is advantageous to arrange that different lamp brightnesses may be indicated to the central control point since runway lamps are commonly operated at different brightnesses in accordance with the ambient lighting. This may be achieved by arranging that predetermined changes in lamp brightness will result in the radiation of appropriately different signals. Many modifications of the arrangements described above are possible. The low power necessary for the transmitter may be derived by inductive coupling from the a.-c. supply to the lamp, or may be provided by a long-life battery arranged to be connected to supply power to the transmitter only when the lamp is alight by a suitable photoelectric control device. The signalling arrangements used are preferably arranged to be of a fail-safe nature so that any intrinsic defect in the apparatus will result in a "lamp failed" indication. When the lamp supervisory device is powered by the light of the lamp itself, then it is apparent that any lamp failure will result in the cessation of the signal from that lamp. If other sources of power are used it is a relatively simple matter to ensure that lamp failure will result in signal cessation, though for the sake of simplicity it may sometimes be preferred to provide a supervisory signal only in response to lamp failure. It will often be considered unnecessary to supervise each of the very many runway lamps and only a predetermined fraction of the total number of lamps will then be provided with supervisory means. Obviously the supervised lamps will be appropriately spaced to prevent failure of any large number of lamps from being neglected. WHAT WE CLAIM IS:

1. Runway lighting supervisory apparatus including means arranged to respond to light emitted by a runway lamp by developing a radio frequency signal denotive of lamp performance, means for transmitting said radio frequency signal to a position remote from said lamp and means at said

position responsive to said signal for producing a further signal in the event of lamp failure.

2. Apparatus in accordance with claim 1, wherein said radio frequency signal is transmitted from an antenna at said lamp to a receiving antenna at said position.

3. Apparatus in accordance with claim 1, wherein said radio frequency signal is transmitted from said lamp to said position over a conductor by which said lamp is supplied with power.

4. Apparatus in accordance with claim 1, 2 or 3, wherein each of a plurality of said means is arranged to transmit a signal of an individual radio frequency.

5. Apparatus in accordance with claim 1, 2 or 3, wherein each of a plurality of said means is arranged to transmit a signal of the same radio frequency having respective individual modulation.

6. Apparatus in accordance with claim 4, wherein lamps in a plurality of spacedapart sets are arranged to transmit radio signals of the same frequency, said signals being arranged to be received by differently positioned receiving antennae.

7. Apparatus in accordance with any one of claims 1 to 6, wherein each said means includes apparatus whereby each said radio frequency signal is transmitted during a respective individual time interval.

8. Apparatus in accordance with any one of claims 1 to 7, wherein said further signal is applied to means providing an indication of the identity or location of any lamp of which the respective radio frequency signal denotes lamp failure.

9. Apparatus in accordance with claim 8, wherein said indication is provided only when a signal denotive of lamp failure is received over a predetermined period.

10. Apparatus in accordance with any one of the preceding claims, wherein the or each said transmitter is powered by a solar cell exposed to light from the respective lamp.

11. Apparatus in accordance with any one of claims 1 to 9 wherein the or each said transmitter is powered by a battery arranged to be connected to power the transmitter only when the lamp is alight.

12. Runway lighting supervisory apparatus substantially as herein described with reference to the accompanying drawings.