This invention relates to a position indicator beacon for use, for example, as a crash position indicator for aircraft, helicopters, sea vessels or vehicles. It is known to provide a crash position indicator comprising a VHF/UHF radio transmitter disposed in a buoyant container and adapted to be mounted on an aircraft or vessel for automatic or semi-automatic activation and release in emergency on to the sea whereby the position of the emergency or crash is indicated by VHF/UHF radio signal transmission.

In use such devices have proved generally satis¬ factory and are widely used as safety devices in fixed wing aircraft whereby in emergency the device is released for free fall but are not suitable in some applications, for example in helicopters where, in an emergency the collective is lowered to cause rapid descending of the helicopter hence airflow upwardly through the rotor blades. This is liable to draw the released device upwardly into these blades and cause destruction of the device and/or helicopter.

Furthermore VHF/UHF radio signals are not always detectable by rescue services for reasons of interference It is known from US-A-4 186 396 to provide a radar beacon comprising a radar transponder having a slot antenna for transmitting and a slot antenna for receiving which are respectively disposed in substantially the same axial direction, and a trans¬ mitting unit and a receiving unit which are respectively connected to each end, in the axial

direction of the slot antenna. The assembly is contain¬ ed within a generally cylindrical radar dome of radar permeable material and suitably includes a dedicated battery for operation of the transmitter and receiver. The receiver is adapted on receipt of a radar signal, for example from a searching aircraft, to set the transmitter into operation. The transmitter generates a modulated radar signal such that the transmitted signal may be received by the search radar as a spaced series of blips on the radar screen representative of the bearing and distance of the beacon from the search radar. Such beacons have been used on ships and on life rafts.

It is an object to provide an improved position indicator device.

A position indicator beacon according to the invention comprises a container incorporating a VHF/UHF frequency radio transmitter connected to a power source within the container and with a trans- mitting antenna, and a radar transponder adapted on the impingement of radar signals to generate an enhanced radar signal response, the antenna and the transponder being disposed in parts of the container respectively adapted for the transmission therethrough of VHF/UHF radio and radar signals.

Suitably the antenna comprises a quarter wave whip antenna mounted above a cylindrical watertight casing of the container which contains the trans¬ ponder, the casing being of material adapted for the transmission therethrough of radar signals.

The cylindrical casing is suitably mounted on a part of the container containing the power source in the form of a battery and forming a buoyancy compart¬ ment, the battery serving as ballast to maintain the cylindrical casing in a generally upright position when floating on water.

The power source is suitably coupled to the transmitter through means automatically operable on release or ejection of the device in an emergency for example an inertia switch, frangible means, time switch, shock sensitive means, or liquid sensitive means such as a float switch or a combination of these.

In one embodiment transmitter is activated by means of a hydrostatic switch when the beacon is floating in water and obtaining an upright position within 40° of vertical for at least 8 seconds. The unit is then latched on so that the VHF/UHF transmitter is in a transmitting condition and the radar trans- ponder activated to respond to receipt of radar signals, The transmitter is suitably adapted to transmit a signal representative of the position of the aircraft at the time of the emergency or ejection of the device and to this end means are provided within the container which are adapted to record or store data representing the aircraft position which are arranged for connection to the aircraft present position indicator such that on ejection of the device the then position of the aircraft is stored. Means are provided to drive the transmitter to transmit a signal representative

of the stored position such that, for example, remote receipt of the signal via satellite communication would allow for the location of the emergency to be decoded from the signal. The recording means are suitably also arranged as a digital data recorder to store data in the manner of an aircract black box such that critical flight parameters normally monitored for black box recorder purposes will be recorded and stored in the recording means such that on location of a deployed beacon, the recording means may be retrieved and the flight data analysed.

Means for releasably mounting the beacon on an aircraft, helicopter or other vehicle or vessel suitably comprise projector means adapted to eject the device at such velocity and in such direction as to clear any impediment. In a particular embodi¬ ment developed particularly for use in helicopters the container of the device at an end of the buoyancy chamber opposite the cylindrical casing, and coaxial therewith, is provided with a cylindrical support open at its end remote from the container. The cylind¬ rical support is slidably engaged within a cylindrical mount of a mounting member adapted to be secured to the helicopter. The support and mount are secured by a transverse shear pin and compression spring ejector means are arranged between the mounting member and the device such that on shearing of the pin the spring ejector means operate to project the container axially in relation to the cylindrical mount and

support. Latch means are provided between the support and mounting cylinder and are adapted to release on shearing of the pin and arranged to take the spring force off the shear pin. A fuse or flare device is contained within the cylindrical mount and is arranged for remote ignition either by manual operation of a switch within the aircraft or by automatic means, for example, an inertia switch, frangible or other shock sensitive means, liquid sensitive means or the like or a combination of such means. The arrange¬ ment is such that, on ignition, gas generation within the cylindrical support and mount effects axial pressure thrust between the support and the mount to shear the pin and allow projection of the device. The latch means suitably comprise ball latch means arranged to act between recesses within the mount and apertures in the support, the arrangement being such that on shearing of the pin the impingement of the edges of the apertures against the balls causes the balls to move inwardly of the cylindrical support through apertures. The ball latches serve to take the spring compression force from the shear pin.

The invention will now be described, by way of example, with reference to the accompanying partly diagrammatic drawings, in which:-

Figure 1 is a side elevation to reduced scale of a buoyant position indicator beacon in upright position-and removed from mounting means,

Figure 2 is a partly sectional elevation of mounting means for the device of Figure 1 to a larger

scale and showing a supported portion of the device of Figure 1,

Figure 3 is a schematic view of the VHF/UHF radar transponder assembly of the beacon of Figure 1. Figure 4 is a side elevation of a further embodi¬ ment of beacon, and

Figure 5 is a schematic view of a further arrange¬ ment of the transmitter and transponder in association with data recording means for use within a beacon. The beacon of Figure 1 comprises a watertight container 1 constituting a lower buoyancy compartment 2 and supporting at its upper end an upright cylindrical watertight casing 3. A spigot 4 projects downwardly from a central lower portion of the container to serve as a support member for releasably mounting the beacon in mounting means as shown in Figure 2. The cylindrical casing 3 is formed of material pervious to high frequency radiation in the VHF/UHF and radar range and contains an upper transmitting antenna 5 and a lower radar transponder 6.

The container 1 and casing 3 are suitably formed at least in parts exposed when the beacon is floating of fluorescent orange (Federal Standard 595a) fire- resistant heavy gauge polyethylene to define an environ- mentally sealed container. The lower portion of the container 1 may be contained within a brass cap formed with the spigot 4.

As shown in Figure 3 the antenna 5 is coupled to a high frequency transmitter 7, suitably mounted within the container 1, arranged to be energised

by a battery 8 through switch means 9. The battery

8 is suitably mounted in a lower part of the container 1 to act as ballast and ensure upright floating of the beacon on water. The switch means 9 is suitably arranged automatically to close and energise the transmitter 7 on discharge of the beacon in emergency and may comprise a time switch, shock sensitive means, liquid sensitive means such as a float switch, frang¬ ible means, or a combination of these. Suitably a hydrostatic switch is employed as the switch means 5 operable when the lower portion of the container 1 is immersed with the beacon floating in an upright position within 40° of vertical after a predetermined minimum period of 8 seconds. The beacon is adapted to float with the cylindrical casing 3 above water level and the hydrostatic switch 5 exposed to water through a sealed aperture in the container 2.

A suitable VHF/UHF antenna is BURNDEPT Model 522 adapted to operate in the international distress frequencies of 121.5 and 243 MHz, a suitable screened VHF/UHF transmitter is BURNDEPT 121.5, 243 Model 522 operating with carrier frequencies of 121.5 and 243 MHz and a suitable radar transponder is an X - BAND MITSUBISHI MELSART Model H.9.5 GHz operating at 9.3 to 9.5 GHz.

The VHF/UHF transmitter BURNDEPT 121.5, 243 Model 522 operating with BURNDEPT VHF/UHF antenna Model 522 or with a wave whip antenna mounted extern¬ ally of the container transmitting a radio distress signal has been found to be detectable by airborne

receivers of appropriate specification up to a distance of 80 nautical miles.

The VHF/UHF transmitter is suitably provided with test load circuitry connectable through contacts exposed externally of the container and powered by the beacon's own battery whereby testing of the efficacy of the transmitter may be effected before operation of the aircraft, helicopter or other vehicle or vessel. The test circuity is also applied to the transponder 6 for like purposes. The external contacts are suitably arranged to engage complementary contacts on a support or mounting means for the beacon and from which the beacon is arranged to be deployed. The complementary contacts are suitably connected to test circuitry on the aircraft, helicopter or other vehicle or vessel incorporating test switches and an illuminated display whereby operation of individual switches allows testing of the functional components within the beacon and approp- riate illumination of the display to indicate satis¬ factory or unsatisfactory conditions.

The radar transmitter of the transponder 6 is operatively coupled to a sawtooth generator adapted when the transponder 6 is receiving a radar signal, for example, a signal from the weather radar of a search aircraft, to cause the transmitter of the transponder 6 to generate a series of enhanced radar signals in the 9.3 to 9.5 GHz band, this band range being compatible with all commercially available

aircraft and marine radars . In an embodiment the sawtooth generator is adapted to generate an operating frequency of 20 repetitions in 100 microseconds at a sweep frequency sawtooth spacing of 5 microseconds nominal, the enhanced radar signals showing an antenna gain of 3dB. As a result, when the beacon is in the line of sight-range it will recognise interrogation of the weather radar of the searching aircraft and reply or echo with a unique response pattern signal of 20 equally spaced pulses which will be represented on a radar display as 20 equally spaced blips extend¬ ing outwardly from the beacon in 0.4 nautical mile increments. The display signal is readily distinguish¬ able from other normal radar echos and against heavy sea clutters and enables the location of the beacon to be pin-pointed from ranges of 39 nautical miles on radar.

As a result a search aircraft may initially home on the radio signal and on detection of the coded radar coded signal can precisely pin-point the beacon position.

Referring now to Figure 2 the beacon of Figure 1 is suitably deployably mounted on mounting means 10 secured to an aircract, helicopter, vessel or other vehicle. The mounting means 10 comprises a cylindrical mounting member 11 slidably receiving a cylindrical extension sleeve 12 of the spigot 4 of the beacon. The sleeve 12 is open at its lower end and slidably receives a plunger 13 secured at its lower end to the member 11 by a transverse shear

pin 14. Within the member 11, below the plunger

13 there is mounted a fuse or flare device 15 arranged and adapted for remote and/or automatic ignition. The lower end of member 11 is closed by a cap 16. The sleeve 12 and member 11 are latched together in releasable manner by balls 17 seated within recesses in the member 11 and engaging apertures in the sleeve 12. The balls 17 are retained in this position by a head of the plunger 13 which is formed below the balls with an annular recess 18, such that on upward movement of the plunger 13 to an uppermost position within the sleeve 12, theballs are released from their seating to -disengage the latch.

At its upper end the sleeve 12 is formed extern- ally with a flange 19 opposed to a similar lower flange 20 extending outwardly from the member 11, the flanges 19,20 forming pressure plates between which are confined compression springs 21 in compressed condition arranged to urge the pressure plates 19,20 apart.

In operation, on ignition of the fuse or flare device 15, combustion gases generate pressure within the member 11 acting against the lower end of the plunger 13 to develop shear stress on the pin 14 until the pin shears, allowing the plunger to rise to register the recess 18 with the balls 17 which fall or are driven inwardly to release the latch between the sleeve 12 and member ^" 11. The compression springs 21 are now free to expand and project the sleeve 11 from the member 12 and thereby project

The beacon from the mounting means 10 and away from the aircraft, helicopter or whatever on which it is mounted.

Ignition of the flare device 15 is suitably by electrically operated ignition means under switched control from a dedicated battery in the helicopter, aircraft or other vehicle or vessel. Switch means for operation of the ignition suitably comprises a frang¬ ible switch, a hydrostatic switch, an inertia switch, whereby in an emergency the ignition device may be operated for example by the pilot manually, or automatically in response to immersion, impact or sensed unsafe rotation of the rotor.

The mounting member is suitably adapted to guide the beacon on projection in a predetermined path and is arranged in use on an aircraft, helicopter whatever to clear obstructions which may be presented. In this respect consideration of the operating conditions of the aircraft, helicopter or other vehicle or vessel needs to be taken into account. For example in heli¬ copter application it is particularly important to take into account the need to clear the updraft caused when reversal of airflow takes place on descent as would be common in an emergency, and the compression spring must be such as to provide adequate projection forces.

Generally with a helicopter the beacon in its mounting member is preferably mounted on the fuselage side or tail boom with the beacon deployed aft and

downwardly.

Referring now to the schematic arrangement of Fig¬ ure 3 showing the operational arrangement of the funct¬ ional parts of the assembly within the watertight container 1 of the beacon of Figure 1, the battery 8 is connected through the hydrostatic switch 9, which is exposed through a sealed aperture in the container 1 below the waterline, to a power management circuit 25 arranged to supply power to the operating circuitry 26 of the transponder 6 and to the transmitter 7 which is connected to the upper transmitting antenna 5. The power management circuitry 25 contains dummy loads for the transmitter 7 and transponder 6 and is connected to a test panel 27 having switch means accessible from outside the container 1 of the beacon and adapted to switch in the dummy loads for test purposes to illuminate LED's on the panel to indicate satisfactory condition. The power management circuitry 25 is connected to a contact set 28, exposed externally of the container 1 for external connection to a source of power for the test purposes. The switch means and on the test panel 27 is suitably arranged in assoc¬ iation with the power management circuitry to reset the power management circuitry to cut off power to the transponder 6 and transmitter 7 when the beacon has been displayed and after the beacon has been removed from water.

In the modified embodiment of Figure 4 in which like reference numerals to those of corresponding parts of Figures 1 and 3 being used, a beacon comprises

a container 1 having a buoyant section 2 with a lower cylindrical extension 30 defining a compart¬ ment for-a battery for operating a- radio transmitter and radar transponder generally as described in connection with Figures 1 and 3. The radar trans¬ ponder is disposed within an upper cylindrical casing 3 arranged to extend above water level when the beacon is floating. A h wavelength whip antenna 5 for the radio transmitter is mounted on the upper end of the upper casing 3 and has a resilient section 31 whereby the antenna 5 may be bent back beside the upper extension 3, as shown, for stowage within the beacon mounting means 10, Figure 2, prior to deploy¬ ment, and such that on deployment the antenna 5 springs to an upright condition in relation to the beacon container 1. The lower cylindrical extension 30 is secured within a lower brass cap 32 formed centrally with the downwardly extending spigot 4, for securement in the mounting member 11 of the mounting means 10 of Figure 2.

As shown in Figure 5 the transponder 6 and radio transmitter 7 contained within container 1, of Figure 4, are connected to the battery power source 8 via power management circuitry 25 and a hydrostatic switch 9 operable through the container by exposure to water when the beacon is floating upright within 40° from vertical generally as described in connection with Figure 3. Also contained within the container 1 is a digital data recorder 33 connected to contacts 34 exposed externally of the container 1 and arranged to contact complementary contacts on the beacon support 10 which are adapted for operative connection to

a present position indicator of an aircraft, helicopter or other vehicle or vessel such that present position data may be recorded and also other flight or passage data relevant to safe flight or passage prior to deployment of the beacon. The recorder 33 is suitably coupled to the radio transmitter 7 so that the carrier signals may be modulated to give a latest present position signal at the time the beacon is activated by the hydrostatic switch after deployment. Flight data recording may be stored in digital form to be retrieved by down loading to a ground based computer.