GB2153981A

GB2153981A - Connecting device for a pyrotechnic circuit leading to an aircraft canopy

Info

Publication number: GB2153981A
Application number: GB08500679A
Authority: GB
Inventors: Gerard Dupin; Louis Lasserre
Original assignee: Avions Marcel Dassault Breguet Aviation SA; Dassault Aviation SA
Current assignee: Dassault Aviation SA
Priority date: 1984-02-09
Filing date: 1985-01-11
Publication date: 1985-08-29
Also published as: GB8500679D0; FR2559451B1; FR2559451A1; IT8519387A0; DE3503673A1; IT1199661B

Abstract

A connecting device for a pyrotechnic circuit leading to an aircraft canopy after crossing the join between the latter and the airframe. It is subdivided into two distinct constituent pyromechanical components, (A, B) intended to be mounted, the one (A) on the airframe (S) and the other (B) on the canopy (V) to form terminals, facing one another, of two portions (3, 7) of pyrotechnic circuit that are integrated respectively into the said frame (S) and the said canopy (V), these two pyromechanical components (A, B) being designed and arranged to ensure automatically by mutual contact, the continuity of the pyrotechnic circuit (3-7) at right angles with the periphery of the canopy (V) when the latter is closed. <IMAGE>

Description

SPECIFICATION A connecting device for a pyrotechnic circuit leading to an aircraft canopy The invention relates to a connecting device for a pyrotechnic circuit leading to an aircraft canopy.

It is known that the evacuation of crews of military high-performance aircraft in distress is effected by ejecting the seat or seats (according to whether a single-seater or multi-seater aircraft is involved) out of the cockpit which, at least in flight, is closed by a transparent cover, made for example of "Plexiglas", shaped to follow the appropriate aerodynamic profile, which is commonly known as a canopy. Obviously, this canopy enclosing the cockpit constitutes a major obstacle on the trajectory of the ejector seat and, if no precaution were taken to eliminate it, the occupant of the seat would collide violently with it and could be injured or killed in the process of shattering it.From another aspect, one cannot rely on opening the canopy prior to the ejection of the seat, for not only is this procedure chancey on account of the possibility of breakdown or damage preventing it from functioning, but also this preliminary operation would consume a not inconsiderable amount of time, causing substantial delay in the process of evacuation, which in certain cases would involve an unacceptable risk.

Furthermore, it had long been envisaged that, immediately (approximately one second) before the ejection of the seat, the canopy might be broken away from the fuselage of the aircraft by pyrotechnic means such as explosive bolts or other analogous releasable fastenings, in such a way as to jettison the canopy assembly (see British Patent 711.987 of 25.1.52), but this form of procedure had to be ruled out because in practice it only replaced one danger by another just as serious; namely, the seat ejected with its occupant on the one hand, and the massive assembly of the canopy (weighing sometimes several tens of kilos) with its sharp corners and roughness on the other hand, were found to go around in the air with irregular movements at high speed and close to one another, from which there was a danger of violent collision.That was particularly true when the aircraft was spinning or was on the ground. In these configurations, aerodynamic effects did not carry the ejected canopy out of the trajectory of the pilot.

In modern military aircraft, always equipped with ejector seats, jettisoning the canopy is not a satisfactory solution, the canopy being, at present, kept in position. But the obstacle that it then constitutes on the trajectory of the pilot is reduced, immediately before the latter is ejected, by means of detonating fuses controlling explosive charges judiciously distributed and arranged to cause disintegration or embrittlement of the canopy, in such a way that, when it is passed through, only small scattered fragments are encountered which, in principal, should not cause serious wounds, not normally being liable to go through the usual protective clothing in which the crew members are dressed. The description of such systems of disintegrating or embrittling an aircraft canopy could be found in French Patents No. 70 24978 of 6 July 1970, No.

80 15489 of 11 July 1980, No. 8022365 of 20 October 1980, British Patent No.

1.340.574 and British Application No. 84 06019 filed 7 March 1984, and one could usefully refer to them for more details on the pyrotechnic means utilised which are anyway in very general use at the present time.

These systems of attacking aircraft canopies by pyrotechnic means unavoidably call for a method of transfer of the shock wave appropriate for crossing the join between the aircraft frame on the one hand and its canopy on the other hand. It must be remembered, in fact, that the latter is generally a hinged cover to allow the normal entry and exit of the crew.

For this pyrotechnic crossover, recourse has hitherto been had to flexible connecting fuses having enough slack to accommodate the displacement of the canopy between its open and closed positions. But these flexible fuses, even if they ensure the continuity of the pyrotechnic circuit, are nevertheless a cause of constraint, not to speak of the risks of damage incompatible with the very idea of security to which the system is supposed to respond.

The object of the present invention is to provide a connecting device which dispenses with such known connections employing flexible fuses for the transfer of the shock wave from the airframe to the canopy, given that the pyrotechnic system is called upon to go into action only when the canopy is in the closed position.

In accordance with the present invention, there is provided a connecting device for a pyrotechnic circuit leading to an aircraft canopy crossing the join between the canopy and the airframe, said device being subdivided into two constituent pyromechanical components intended to be mounted, one on the airframe and the other on the canopy, to form facing terminals of two portions of a pyrotechnic circuit being integrated respectively into the frame and the canopy, these two pyromechanical components being designed and arranged to ensure automatically, by mutual contact, the continuity of the pyrotechnic circuit at right angles with the periphery of the canopy when the canopy is closed.

Preferably, the two pyromechanical components of the connecting device have respective male configuration and female configuration which adapt one to the other on closure of a hinged canopy and are orientated in such a way that their axis of mutual adaptation is perpendicular to the hinge axis of the canopy.

If, as is usual, this latter axis is located at the rear of the canopy, the two pyromechanical components may likewise be disposed to advantage towards the rear of the canopy, but spaced from its hinge, for example, at the bottom of the rear arch of the canopy.

In this way, one ensures the mechanical protection of the terminals, thus reinforced, of the two pyrotechnic circuit portions, being rigid at either side, without interfering in any way with the normal movements of opening and closing the canopy which is devoid of any mechanical link with the airframe except (of course) for its hinge.

The invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a partial diagrammatic view of an aircraft canopy, illustrating the mounting of a connecting device constructed in accordance with the invention, Figure 2 is a view in axial section, on a larger scale, of a connecting device in accordance with the invention, Figures 3 and 4 are similar views showing the device in the closed position and the open position respectively.

In Figure 1 can be seen the rear part of a canopy V hinged at P on an aircraft frame 8, the canopy P being depicted in the closed position At a convenient point of the interface between the canopy and the frame, located at a position spaced from the hinge P and, with advantage, towards the rear of the canopy V, a connecting device is mounted. This has two constituent parts A and B, fixed respectively on the airframe 8 and on the canopy V and each arranged to receive a pyrotechnic circuit portion. The latter can comprise a fuse loaded for example, with 0.45 g/m of a disruptive explosive known by the name of "Hexogene" and terminating in a cap loaded for example with 60 mg of pentrite.

Part A, joined to the airframe with the aid of a fitted support, contains (see Figures 2, 3, 4) a moveable piston 1 fitted with the cap 2 of the input circuit portion 3. A spring 4 urges the piston 1 forwards and a stop 5 limits travel when the canopy is open (Figure 4), preventing the accumulation of foreign bodies such as dust or sand. The input portion 3 is flexible enough to accommodate the movements of the moveable piston 1.

Part B, joined to the canopy with the aid of a fitted support, is equipped with a cap 6 of the output portion and its configuration is such that at the moment when the canopy closes, the two portions 3 and 7 are in alignment, the moveable piston 1 ensuring permanent contact of the two walls that protect the caps 2 and 6. For the functioning of the pyrotechnic portions, the caps are such as to ensure the passage of a shock wave through their protective walls.

In practice, correct functioning is ensured with tolerances of lateral offset of + 0.25mm longitudinal offset of + 3.5 - 5mm, and angular offset of + 3 .

For a canopy V of the current type (Figure 1), the mounting of the connector A, B is located at the level of the base of the rear arch V', the plane at the interface I of the two parts passing through the axis of articulation P of the canopy which is thereby perpendicular to the axis X-Y of the connector A, B.

The system is perfectly symmetrical at the level of the pyrotechnic elements, so that the shock wave can be routed in one direction or in the other, allowing the use of the connector for any application other than the embrittlement of the canopy.

Claims

1. A connecting device for a pyrotechnic circuit leading to an aircraft canopy crossing the join between the canopy and the airframe, said device being subdivided into two constituent pyromechanical components intended to be mounted, one on the airframe and the other on the canopy, to form facing terminals of two portions of a pyrotechnic circuit being integrated respectively into the frame and the canopy, these two pyromechanical components being designed and arranged to ensure automatically, by mutual contact, the continuity of the pyrotechnic circuit at right angles with the periphery of the canopy when the canopy is closed.

2. A connecting device according to claim 1, wherein the two pyromechanical components have respective male configuration and female configuration which adapt one to the other on the closure of a hinged canopy and are orientated in such a way that their axis of mutual adaptation is perpendicular to the hinge axis of the canopy.

3. A connecting device according to claim 2, in which, with a hinge axis of the canopy located at the rear thereof, the two pyromechanical components are also disposed towards the rear of the canopy but spaced from its hinge axis.

4. A connecting device according to any one of claims 1, 2 or 3, in which one of the components includes a moveable piston hav ing a cap of a pyrotechnic circuit portion, the piston being positioned by a spring with a stop arranged to limit movement when the canopy is open, this piston being urged back against the action of the spring by engage ment with the other component when the canopy is closed.

5. Application of the connecting device ac cording to any one of the preceding claims to the embrittlement by pyrotechnic means of an aircraft canopy, with a view to the ejection through the latter of a crew member.

6. A connecting device for a pyrotechnic circuit leading to an aircraft canopy substantially as hereinbefore described with reference to and as shown in the accompanying drawings.