Parachute deployment system

Abstract: A parachute has a canopy (10) and rigging lines (11) with skirt assist lines (15) connected between a point on each rigging line (11) adjacent a lower edge (12) of the canopy (10) and a point on the interior of the canopy (10) spaced from the lower edge (12). The arrangement is such that a portion of the canopy (10) between the point and the lower edge (12) is relieved of tension as the canopy (10) is deployed to assist the opening of the canopy (10). The skirt assist lines (15) are frangible. This prevents rapid deployment of the canopy to lower g-forces on the load in high speed opening.

Description: The invention relates to parachutes. The term "parachutes" is intended to cover any type of parachute provided with a canopy with rigging lines connecting the canopy to a load. When such a parachute is deployed, air enters the canopy of the parachute and inflates the canopy. When the canopy is deployed at low speeds and at low levels, the inflation may not be sufficiently rapid to ensure satisfactory opening. In order to improve the opening, it is known to provide a plurality of skirt assist lines. Each skirt assist line extends between a respective rigging line and a respective point on the interior of the canopy such that a portion of the canopy between the point and the lower edge of the canopy is relieved of tension as the canopy is deployed. As a result, this portion of the canopy spreads very rapidly and assists in rapid opening of the remainder of the canopy. This is shown in EP-A-0861 783 in a reserve parachute. It is a problem with such skirt assist lines that, at higher speeds, the rapid deployment of the portion of the canopy between the connection points of the skirt assist lines and the lower edge of the canopy can induce g-forces on a load which are undesirable. The load may be a parachutist or cargo. This is particularly true where the load is a person and can occur, for example, where the parachute forms part of an ejection seat which may be deployed at high or low levels and at high or low speeds. According to the invention, there is provided parachute comprising a canopy having a lower edge, rigging lines connecting the canopy to a load and a plurality of skirt assist lines, each skirt assist line extending between a respective rigging line and a respective point on the interior of the canopy such that a portion of the canopy between the point and the lower edge is relieved of tension as the canopy is deployed to assist the opening of the canopy characterised in that the skirt assist lines are frangible under a predetermined load in the lines experienced when the canopy deploys at high speed. By making the skirt assist lines frangible, the skirt assist lines can be rendered inoperative in circumstances where their operation would cause undesirable g-forces. The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which:- Figure 1 is a schematic view of a parachute showing a canopy of the parachute in a first stage of deployment and rigging lines for connection to a load with skirt assist lines extending between the rigging lines and the canopy, Figure 2 is a similar view to Figure 1 but showing the skirt assist lines broken. Referring first to Figure 1, the parachute comprises a canopy indicated diagrammatically at 10 by rigging lines, some of which are shown at 11, attached to a parachutist or cargo shown schematically at 18. The canopy 10 has a lower edge 12 and an apex 13 and may be of any suitable construction. In general, the canopy will be formed by gores (not shown) interconnected by seams. The canopy 10 may be of any known shape and be for any intended purpose. For example, the canopy may be generally conical and may be deployed by static line or used in free fall. The canopy may be provided as part of an aircraft ejection seat. The parachute is provided with skirt assist lines 15. Each skirt assist line 15 is connected between a rigging line 11 and the canopy 10. The connection is between a point 16 on the rigging line 11 adjacent the lower edge 12 of the canopy and a point 17 on the interior of the canopy 10 spaced from the lower edge 12. The length of each skirt assist line 15 is less than the distance between the points 16,17 along the associated rigging line 11 and along the canopy 10. In general, the connection point 17 on the canopy will be along a main seam between two adjacent gores of the canopy 10. There may be a skirt assist line 15 between every rigging line 11 and the canopy 10 or only between some rigging lines 11 and the canopy. In use, the canopy 10 and the rigging lines 11 are packed in a deployment bag or container (not shown) from which the canopy 10 is deployed. As indicated above, this deployment may be manual or automatic. On deployment, the canopy 10 streams from the deployment bag or container and adopts the uninflated disposition shown in Figure 1. The effect of the skirt assist lines 15 is to relieve from tension the portion of the canopy 10 between the lower edge 12 and the points 17 of connection of the skirt assist lines 15 on the canopy 10. This allows this portion of the canopy 10 to move outwardly rapidly in the air flow to promote fast inflation of the canopy. This is particularly advantageous when deployment is at low level and/or low speed. The skirt assist lines 15 are frangible. The purpose of this is to prevent the portion of the canopy 10 between the lower edge 12 and the points 17 of connection of the skirt assist lines 15 on the canopy 10 from moving outwardly on deployment of the canopy 10. This is desirable when the canopy 10 is deployed at high speeds in order to prevent the parachutist or other load 18, being subjected to undesirably high g-forces. Under such circumstances, the higher speed of deployment is sufficient to ensure satisfactory inflation of the canopy 10. The skirt assist lines 15 may be made frangible and or severable in a number of ways and at any point. First, each skirt assist line 15 may be provided with a weak point designed to break under a predetermined load equivalent to that experienced by the rigging line 11 when the canopy 10 opens at high speed. Accordingly, on such high speed opening of the canopy 10, the skirt assist lines 15 break at the weak points to prevent rapid outward opening of the portion of the canopy 10 between the lower edge 12 and the points 17 of connection of the skirt assist lines 15 on the canopy 10. The g-forces on the load are thus reduced. As an alternative to weak points, each skirt assist line 15 may be provided with a device that severs the skirt assist line 15 when high speed opening loads are sensed. This achieves the same effect as the weak points. Additionally or alternatively, the skirt assist lines 15 may be able to be broken prior to deployment of the canopy 10. For example, the skirt assist lines 15 may be severable at any time before deployment.

Claims: A parachute comprising a canopy (10) having a lower edge (12), rigging lines (11) connecting the canopy (10) to a load (18) and a plurality of skirt assist lines (15), each skirt assist line (15) extending between a respective rigging line (11) and a respective point on the interior of the canopy (10) such that a portion of the canopy (10) between the point and the lower edge (12) is relieved of tension as the canopy (10) is deployed to assist the opening of the canopy (10) characterised in that the skirt assist lines (15) are frangible under a predetermined load in the lines experienced when the canopy deploys at high speed. A parachute according to claim 1 wherein each skirt assist line (15) includes a weak point designed to break the associated skirt assist line (15) if the load in the skirt assist line (15) exceeds said predetermined maximum. A parachute according to claim 2 wherein each skirt assist line (15) is severable at said predetermined load by means associated with each skirt assist line (15).

Inventors: HIRST DAVID RICHARD JORDAN, PARKER NIGEL STUART, HIRST, DAVID RICHARD JORDAN, PARKER, NIGEL STUART
Applicants: AIRBORNE SYSTEMS LTD, AIRBORNE SYSTEMS LIMITED
Application year: 2001
Main classification: B64D17
IPC codes: B64D17