GB2120612A - Aircraft ejection seats - Google Patents

Abstract

An ejection seat the control apparatus whereof has timing and triggering apparatus comprising tubes (11-14) containing a pyrotechnic compound. The tubes are preferably flexible lines and may incorporate delay means within the compound or the timing apparatus may be electronic etc. <IMAGE>

Description

SPECIFICATION Improvements in ejection seats The present invention relates to aircraft ejection seats, and is particularly concerned with means for initiating and controlling a sequence of events which occur when an ejection seat is operated.

A typical sequence of events occurring when the operation of an ejection seat is initiated comprises immediate canopy jettison and man/seat harness retraction, then initiation of the operation of a Barometric Time Release Unit (BTRU), after 0.25 seconds firing of the gun to drive the seat out of the aircraft, after 0.48 seconds, i.e. at the end of the gun stroke, ignition of the rocket motor required to drive the seat away from the aircraft, and after 0.83 seconds deployment of a drogue parachute.

Dependent on altitude and deceleration the BTRU controls deployment of a main parachute and separation of the aircrewman from the seat.

In a known ejection seat the sequencing is effected by clockwork means, and the conveyance of signals and the triggering by gas-actuated mechanical devices.

An object of the present invention is to provide timing and triggering means on an ejector seat which are at least as reliable and accurate as the known means, but which are simpler, cheaper and lighter in construction.

According to the present invention an ejection seat has sequencing and triggering apparatus comprising tubes containing pyrotechnic preparations.

In one embodiment of the invention timing of the ejection seat operation sequence is at least to some extent effected within the tubes by a combination of physical length and content variation. The apparatus may incorporate an initial trigger in the form of an igniter such as a fuze or other explosive device, the trigger being arranged for operation by the ejection lever handle or button.

In another embodiment of the invention a timer, for example, an electronic timer, is arranged substantially to control the sequence and the delays. In this embodiment the pyrotechnic preparations in the tubes may be substantially similar.

The tubes containing the pyrotechnic preparations are preferably physically flexible or conformable plastics material. Such delay cords are made by Space Ordnance Systems Inc. of California, USA, Link Ordnance Inc. of California, USA, and Explosive Technology Inc., of California, USA, and can be arranged to have speeds of operation between 3 mm/second and 1 Km/second. Initiation means at the control end of the tube may comprise explosive igniters, of which there may be one for several pyrotechnic tubes.

The physical flexibility and the delay flexibility of the delay cords give means according to the present invention their principal advantage over known apparatus. Other advantages are that the pyrotechnic means are highly resistant to external heat, abrasion, impact, vibration, shock, humidity and can be arranged to operate without unacceptable variation in speed over a wide range of environmental temperature. Particularly important can be their invulnerability to electrical and electronic interference from aircraft or weapon borne apparatus or signals.

The apparatus may be arranged to operate cockpit canopy jettison means or to initiate canopy shattering means of the miniature detonating cord (mdc) type or one of the electrical types described in Patent Specifications 1 550352 and 2013146.

Ejection seat sequencing and triggering apparatus will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a pyrotechnic timing and signalling block diagram, and Figure 2 is an electronic timing and pyrotechnic signalling block diagram.

In the apparatus illustrated in Figure 1 an initiator 10 having an associated eject handle 1 0a is adapted to initiate operation of four pyrotechnic lines 11, 12, 13, 14. The line 11 is an instantaneous operation pyrotechnic and is connected to both canopy removal apparatus 1 5 and a harness retraction unit 1 6. The line 12 is a pyrotechnic delay cord connected to an ejection seat gun initiator unit 17. The line 13 is a pyrotechnic delay cord connected via an interrupter 1 8 to a seat rocket motor 1 9. The line 14 is a pyrotechnic delay cord connected to a drogue release unit primary initiator 20 and to a detonator latch 21 a associated with a barostat accelerometer unit 21.Other trips associated with the unit 21 are a 5000 metres barometric height trip 5000, a deceleration trip Z, a 2000 metres barometric height trip 2000, and a seat movement trip 21 b. The unit 21 also has a striker 21 c (typically a spring) and an output igniter 22. The igniter 22 is adapted to initiate operation of a pyrotechnic delay line 23. This is connected simultaneously to a drogue release unit secondary initiator 24, a shoulder harness release device 25, a main parachute seat shackle release unit 26 via instantaneous pyrotechnic cords 27, 28, 29 respectively. A manual override unit 30 is connected to by-pass the delay line 23.

It will be appreciated that those portions of the pyrotechnic lines 11, 12, 1 3 and 14 indicated in figure 1 as dotted are the portions adapted for delayed operation so that the line 11 operates substantially instantaneously while lines 12-14 are adapted for increasingly delayed operation respectively. It will also be appreciated that it is standard practice to employ in ejection seats seat movement interrupters which have the function of items 1 8 and 21 b, that is of ensuring that certain events have occurred in an ejection sequence before others are commenced.

In operation of the apparatus illustrated in figure 1, pulling the 'Eject' handle 1 Oa fires the igniter 10 which initiates combustion in the lines 11, 12, 13, 14. Consequently almost immediately the canopy removal apparatus 1 5 and the harness retraction apparatus 1 6 are initiated. A short while later the ejection seat gun 1 7 is fired and movement of the seat out of the aircraft commences. The seat having moved, the interrupter 1 8 permits the pyrotechnic line 13 to initiate the rocket motor 1 9 which drives the seat away from the aircraft. Then, by virtue of the line 14 the primary cartridge 20 of the drogue gun is fired and the trip 21 a removes one obstacle to the operation of the barostat-accelerometer unit 21.

Firing of the primary cartridge 20 causes the secondary cartridge 24 to fire also and assist in the deployment of the drogue. The drogue pulls out the main parachute when the release unit 26 has operated.

The operation of the unit 21 is as follows. Upon leaving the aircraft the seat movement trip 21 b ceases to inhibit operation of the striker 21 c. If the seat is below 2000 metres barometric height, all trips are out and the striker 21 c immediately initiates the output 22 and the line 23, after the inherent delay, fires the drogue secondary 24 (if it has not already been fired by the primary cartridge 20) via the line 27, the release unit 26 via the line 29, and the shoulder harness release device 25 via the line 28.

The seat occupant is thereby released from the seat, remaining suspended on the main parachute.

Alternatively, while the seat is above 5000 m the striker 21 c is inhibited until the seat and occupant have fallen to that height. Between 5000 m and 2000 m the striker 21 c is inhibited until the deceleration trip Z senses a deceleration lower than a predetermined level, when the striker 21 c becomes uninhibited and fires the unit 22 etc. as described above. In the event of a failure of the barostat-accelerometer unit 21 the seat occupant can obtain immediate seat-man separation by operating the override 30.

In a typical embodiment of the apparatus described above with reference to the accompanying figure 1, the delay lines 12, 13, 14 and 23 are arranged to take respectively 0.25, 0.48, 0.83 and 1.0 seconds to pass their signals, the devices illustrated in figure 1 by a box with an 'S' and an arrow therein are percussion cartridge strikers, the devices illustrated by a box containing the legend 'IG' are igniters, and the devices illustrated by a box with a diagonal cross therein are percussion fired power cartridges.

Alternatively face-fired cartridges may be employed, fired directly by the pyrotechnic tubes.

In the apparatus illustrated in figure 2 an electronic controller 40 is responsible for controlling the ejection sequence. It comprises a switch 41 adapted for operation by an eject handle 42 and arranged when 'OFF' to inhibit a timer 43. The timer 43 is connected via an amplifier 44 to an igniter 45, and via a 1/10000 divider 46 to a divider 47, a seat movement trip switch 48, a divider 49, and a divider 50.

The igniter 45 is linked via instantaneous pyrotechnic lines 51, 52 respectively to a canopy removal apparatus 53 and a harness retraction device 54. The divider 47 is connected via an amplifier 55 to an igniter 56 linked via an instantaneous pyrotechnic line 57 to a seat gun 58. The switch 48 is controlled by a seat movement trip 59 and is connected via a divider 60 and an amplifier 61 to an igniter 62. The igniter 62 is linked via an instantaneous pyrotechnic line 63 to a seat rocket motor 64. The divider 49 is connected via an amplifier 65 to an igniter 66 and via an electronic switch 'A' 67 to one input of an AND gate 68. The igniter 66 is linked via an instantaneous pyrotechnic line 69 to a primary cartridge 70 associated with a drogue deployment device. The divider 50 is connected via an electronic switch 'B' 71, a divider 72, and an amplifier 73 to an igniter 74.The igniter 74 is linked via an instantaneous pyrotechnic line 75 to a seat/man release device 76 and thence to a secondary cartridge 77 associated with the drogue deployment device and a shoulder harness release cartridge 54a.

A manual override 78 is arranged for firing the drogue secondary cartridge 77, the shoulder harness release cartridge 54a, and the seat/man release device 76.

This embodiment of the apparatus also includes a barostat-accelerometer unit 80 in electronic form. In the unit 80 a seat movement trip switch 81 is connected to a barometrically operated switch 82, the output of which is connected to a deceleration operated switch 83 in parallel with a barometrically operated switch 84. The outputs of the switches 83 and 84 are connected to the other input of the AND gate 68, the output of which, on reaching the logic state '1', switches 'ON' the switch 'B' 71.

It will be appreciated that the timer is adapted to provide pulses at timed intervals, and the dividers to count them and, in the case of the dividers 47, 49, 60 and 72, to pass a signal after a given number thereof. The dividers 46 and 50 produce trains of output pulses at the reduced frequencies.

Accordingly, in operation of the apparatus, pulling the handle 42 permits the timer 43 to commence, whereupon immediately a signal is passed via the amplifier 44 to the igniter 45. This fires the lines 51 and 52 and hence, practically instantaneously, the canopy removal and harness retraction means 53 and 54. The dividers 46 and 47 count down the 1 MHz pulse train from the timer 43 to produce a signal, a given time after initiation, which is passed via the amplifier 55 for firing the seat gun 58. When seat motion has operated the trip 59 (and 81) the switch 48 allows pulses through to the divider 60 and after a given number thereof a pulse is passed to the amplifier 61 for igniting the seat rocket 64. The divider 49, having counted the required number of pulses, passes a signal to the amplifier 65 for firing the primary cartridge 70 of the drogue deployment device and switches 'ON' the switch 'A' 67 for the AND gate 68. The pulses from the divider 50 are not passed by the switch 'B' 71 until a logic state '1' is achieved at the AND gate 68, when a pulse is passed to the divider 72, so that after a predetermined interval or sequence the seat/man release device 76 will be operated, together with the drogue secondary cartridge 77 and the shoulder harness release cartridge 54a.

The operation of the barostat/accelerometer unit 80 is analogous to that of the unit 21 described above with reference to figure 1, but is also defined in the logic table, Table 1, below: Table 1

< 5000 m < 5000 m > 2000 m > 2000 m < 2000 m > 5000m > 3sn < 3 -n n 5000 m baro switch 0 1 1 1 2000 m baro switch 0 0 0 1 Accelerometer switch 0 or 1 0 1 O or 1 Output state 0 0 1 1 When the output logic state of the barostat-accelerometer unit is 1, there is an output to the AND gate 68 which combines with the input from switch A 67 to turn on switch B 71 and allow the pulse train from the divider 50 through to the divider 72, for passing a signal to the amplifier 73 and the igniter 74.

Operation by the seat occupant of the manual override 78 ensures- that the drogue has been deployed and brings about seat/man separation.

In a typical example of the embodiment described with reference to figure 2, using a 1 MHz timer 43, the dividers 47, 49, 50, 60, 72 are 1/25, 1/83, 1/10, 1/48 and 1/10 dividers respectively, whereby there are trains or pulses at: Time 0.25 s to the gun cartridge 58 0.48 s to the rocket motor 64 0.83 s to the drogue primary cartridge 70 0.83 s to the AND gate 68 via electronic switch 67 and every 0.1 s to electronic switch B 71 for the 1.0 s delay in the main parachute shackle cartridge circuit.

A particular advantage of the embodiment described with reference to figure 2 is that the electronic controller 40 can be encased in metal as a single unit and thus shielded. against being affected by electric magnetic fields etc. in the vicinity thereof. Another is that it can readily be modified to provide different time intervals.

Claims (8)

1. An ejection seat having an ejection seat sequencing and triggering apparatus comprising tubes containing pyrotechnic preparations.

2. An ejection seat as claimed in claim 1 and wherein timing of the ejection seat operation sequence is at least to some extent effected within the tubes by a combination of physical length and content variation.

3. An ejection seat as claimed in claim 1 or claim 2 and incorporating an initial trigger in the form of an igniter such as a fuze or other explosive device, the trigger being arranged for operation by the ejection lever handle or button.

4. An ejection seat as claimed in claim 1 and having a timer, for example, an electronic timer, is substantially to control the sequence and the delays.

5. An ejection seat as claimed in any one of the preceding claims and wherein the tubes are physically flexible or comfortable.

6. An ejection seat as claimed in claim 1 or claim 2 and any one of the preceding claims and having initiation means at the control end, of the tubes, the initiation means comprising explosive igniters.

7. An ejection seat as claimed in any one of the preceding claims and substantially as hereinbefore described with reference to figure 1 of the accompanying drawings.

8. An ejection seat as claimed in any one of the preceding claims and substantially as hereinbefore described with reference to figure 2 of the accompanying drawings.