EP0675334B1 - Aerodynamic stabilisation and braking device for air-drop body - Google Patents

Description

The present invention relates to dropable vehicles from an aircraft, of the type fitted with passive stabilization means aerodynamics, such as fins, intended for take an initial trajectory after dropping substantially parallel to the speed of the aircraft. The term "aircraft" must be interpreted as covering both devices to rotary wing as those with fixed wing.

The invention finds an important application in the field of infrared or electromagnetic decoys which, to be effective, begin to play their role nearby of the aircraft to cause the hang of a self-steering or radar of a hostile and then have to move away sufficiently progressive that the self-director or the radar stays on them, but fast enough so that a missile self-director or a radar cannot, after extinguishing the lure, hang on again the aircraft.

We already know (CH-A-480 612 which corresponds to the preamble of claim 1) a rocket having brake flaps deployable from a position where they are pressed against the body at a stop position, substantially perpendicular to the body. The shape and inclination of flaps remain unchanged regardless of the train, due that the flaps bear against a stop or are put in place by a drawer. We also know (DE-A-2 637 793) a dispersion munition provided with elastic lamellae, intended to bring the ammunition in a vertical position. For this, the slats deploy as soon as the ammunition is out of its container and take an orientation of minus 10 °, typically around 20 °. The constitution of these slats gives them an effect that is not what you are looking for for the invention.

Current lures, whether or not equipped with a propellant charge, do not fill this condition throughout the flight envelope of the aircraft to be equipped

If for example we give to a non-powered lure, aerodynamically stabilized, a drag coefficient Cx such that it gives the machine a separation from the plane satisfactory at high speed and low altitude, this coefficient cannot provide sufficient separation for a ejection at lower speed or higher altitude, due to from the drop in dynamic pressure.

The present invention aims in particular to provide a machine whose spacing law after release from an aircraft is almost insensitive to flight conditions, unlike previously known devices. The invention proposes for this purpose a machine according to the characterizing part of the claim 1.

Other characteristics and particular modes of realization are defined in the subclaims.

We can thus adapt the drag of the machine to the conditions ejection, so that the relative trajectory of the aircraft and the craft respect a given size, whatever these conditions, at least in one area of predetermined use.

It will be mainly a question afterwards of the case of a machine, such as a lure, without propellant. But the invention also applies in the case of a machine fitted with a load of clean propulsion, giving a non-adjustable thrust, intended either to bring the machine to the front of the aircraft after drop, or to slow the increase in delay the craft.

In all cases, the maintenance of the law of separation in a predetermined template is carried out without intervention external, without preliminary adjustment, without active means to edge of the craft.

The above provisions, as well as other usable advantageously in conjunction with the previous ones, but can be independently, will appear better at reading the following description of particular modes of embodiment, given by way of nonlimiting examples.

• la figure 1 montre les éléments concernés par l'invention d'un dispositif constituant un premier mode de réalisation, vu en demi-élévation avec coupe partielle, alors que les volets sont repliés ;
• la figure 2, similaire à la figure 1, montre les volets totalement déployés ;
• la figure 3 est une vue en coupe suivant la ligne III - III de la figure 2 ;
• les figures 4 et 5, similaires à la fig. 1, montrent un autre mode de réalisation, les volets étant représentés à l'état replié (figure 4) et à l'état déployé (figure 5).

The description refers to the accompanying drawings, in which:

• Figure 1 shows the elements affected by the invention of a device constituting a first embodiment, seen in half-elevation with partial section, while the flaps are folded;
• Figure 2, similar to Figure 1, shows the flaps fully deployed;
• Figure 3 is a sectional view along line III - III of Figure 2;
• Figures 4 and 5, similar to fig. 1, show another embodiment, the flaps being shown in the folded state (FIG. 4) and in the deployed state (FIG. 5).

The machine whose general appearance is shown in Figures 1 to 3, is intended to be used as an infrared lure or electromagnetic. It has a body 10, of general appearance cylindrical, having a front cone and a boundary envelope a chamber 12 which contains the payload: a load pyrotechnic or a jammer as appropriate. The craft is designed to be placed in a magazine cell and for be evicted on demand by a charge of unloading represented. The charger itself may have a constitution known, for example that described in the patent application No. 93 10928 of the applicant (FR-A-2 710 025).

The body carries aerodynamic stabilization means of the machine, intended to orient its longitudinal axis along of the trajectory. These purely passive means are formed by several fins or fins 14. These fins, four in number in the illustrated embodiment, are each fixed to two sockets 16 rotating on two aligned axes arranged in the body. Pre-compressed means tend to move the fins 14 from their folded position and bring them in the radial orientation where they are shown in Figures 1 and 2 and dashed in Figure 3. These means can be constituted by springs (not shown). The final orientation of the fins is fixed by support of these fins against a stop of the envelope.

According to the invention, the machine further comprises flaps which can be deployed automatically after release. In the case illustrated in FIGS. 1 to 3, each of these flaps 17, four in number, is constituted by a spring steel plate, the front part of which is held pressed against the body by fixing means, such as screws 18. When the machine is stored, the flaps 17 are kept applied against the body of the machine, under the fins 14, and are therefore compact. They are preformed in the deployed position, so that they are then under tension and in the absence of stress they take a free position making a determined angle a with the axis of the machine ( a ≈ 45 ° for example). The elasticity of the flaps is such that the dynamic pressure exerted on them in flight gives them an angle relative to the axis of the body which depends directly on the dynamic pressure and which is less than a . The length of the flaps 17 and the fins 14 is such that they do not project beyond the rear of the body.

In the embodiment illustrated in Figures 1 and 2, the front part of each flap 17 is reinforced by shorter elastic blades 20 whose presence modifies the law of deformation. These additional blades will be or not present according to the law of variation of the drag at give to the craft. They are fixed flat on the shutters, for example by rivets 22.

Figure 3 shows that the addition of the flaps of aerodynamic braking does not imply a decrease in payload of decoy and modifies very little the outer geometry of the machine. The bulges that represent the sockets needed to articulate the fins 14 and allow them to fold over the flaps take place easily, in the cells, square in shape, of the charger. It will simply be necessary, in general, to give each of the flaps 17 a width less than the body diameter, as shown in Figure 3. The overall dimensions extra due to the fins is shown in the figure 3 by a dashed frame. Deployment of the fins, such as indicated by the arrow f, releases the flaps 17 and allows them to deploy in turn.

The shape of the fins 14 and that of the flaps 17, as well that the nature of the flap fixing means depend on of the intended application. We can indicate as an example that in the case of a device consisting of a lure with a gauge of 30 mm and about twenty centimeters long, four flaps without reinforcing blades, spring steel 0.6 mm thick, fixed to the body by a few solder points.

The embodiment shown in Figures 4 and 5, where the elements already shown in Figures 1 to 3 bear the same reference number, still has fins of stabilization 14 and deployable flaps 17a.

The stabilization fins have the same shape and the same mounting as in the case of FIGS. 1 to 3. On the other hand, each flap 17a is constituted by an elastic metal blade (spring steel in general), articulated on the body to the back of the skates. For this, each flap 17a can be welded to one of the elements of a hinge 24 placed immediately behind the rear sockets 16. The hinges have a limited clearance, so that the flap in the free state, once turned towards the rear , make an angle b of about 45 ° with the axis of the body, near the hinge.

The flap 17a is intended to be folded towards the nose of the machine when it is stored and kept pressed against the body by a fin 14 (Figure 4). The shutter can be preformed to take the form shown in solid lines in FIG. 5 as soon as the machine is ejected and the fins 14. When the flaps 17a have a raised beak 26, their deployment is caused by the action of the wind on beak. The wind action can be replaced or supplemented by that of other means, for example by a pincer spring mounted on the hinge 24, a spring intended to take off slightly the flap of the body when released, or a wire of traction connected to the corresponding fin.

Once deployed, the flaps 17a take a form which depends on the dynamic pressure acting on them, intermediate between the form indicated in dashed lines and the form indicated in dashes in figure 5. If necessary, the hinge 24 can be fitted with a retractable or destructible stop under a given constraint, so as to release the shutter beyond a given dynamic pressure and to reduce then maximum drag.

Claims (10)

1. A missile which may be dropped from an aircraft, provided with passive aerodynamic stabilisation means, designed to follow an initial substantially parallel trajectory at the speed of the aircraft after being dropped, comprising, at the rear, braking flaps (17, 17a) which can be automatically deployed after dropping, characterised in that the flaps are so designed and mounted on the missile body that they assume an orientation directed towards the rear on dropping, such that the dynamic pressure exerted on the flaps automatically modifies the inclination or shape of the flaps in a direction such that the additional drag imparted by the flaps varies as an inverse function of said dynamic pressure, ensuring automatic adaptation to the flight conditions.
2. A missile as claimed in claim 1, characterised in that the flaps (17, 17a) are of a flexibility such that they deform immediately they reach their deployed position in a direction which reduces the drag coefficient when the dynamic pressure exerted on them increases.
3. A missile as claimed in claim 2, characterised in that the front of said flaps (17) is fixed flat against the body (10) of the missile.
4. A missile as claimed in claim 2 or 3, characterised in that the front part of the flaps is reinforced by shorter blades (20) fixed flat against the flaps (17).
5. A missile as claimed in claim 2, 3 or 4, characterised in that the flaps are preformed so as to be oriented at approximately 45° relative to the axis of the missile in the released state.
6. A missile as claimed in claim 1, characterised in that the flaps are joined to the body of the missile by resilient means which bend under the action of the force exerted on the flaps, in a direction which reduces the drag coefficient when the dynamic pressure increases.
7. A missile as claimed in claim 1, characterised in that each flap (17a) is made from a blade of resilient metal, the rear of which is hinge-mounted on the body to the rear of pads by means having a restricted displacement, the flap being designed so that it can be folded in towards the nose of the missile when it is stowed and held supported against the body.
8. A missile as claimed in claim 7, characterised in that said flap (17a) has an upturned nose (26) designed to cause deployment due to the action of the wind on the nose.
9. A missile as claimed in claim 7 or 8, characterised by elliptic spring means for detaching the flaps.
10. A missile as claimed in claims 7, 8 or 9, characterised in that the hinge means (24) are provided with a stop which is retractable or destructible under a given constraint so as to release the flap above a given dynamic pressure.

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