GB2102357A

GB2102357A - Parachutes-reducing shock loading

Info

Publication number: GB2102357A
Application number: GB08221395A
Authority: GB
Inventors: David Richard Dennis
Original assignee: UK Secretary of State for Defence
Current assignee: UK Secretary of State for Defence
Priority date: 1981-07-28
Filing date: 1982-07-23
Publication date: 1983-02-02
Also published as: GB2102357B

Abstract

On a multi-arm parachute a reef comprising a ring tie 12 situated at between 0.5 and 0.9, preferably 2/3, of the height of the risers 11, and reefing the parachute to 1/3-1/2 its full skirt diameter, and means 13, e.g. cutting means, for de-reefing the parachute shortly after deployment. The reef curtails the peak load of the parachute and enhances its stability. <IMAGE>

Description

SPECIFICATION Improvements in or relating to parachutes The present invention relates to parachutes.

In particular it is concerned with reefing means for reducing the opening load and drag of a multi-arm parachute.

Reefing means comprising periphery or skirt limitors have in the past been employed on traditional circular parachute canopies to reduce the opening force generated by the parachute to a level which is safe and acceptable to the store or person using the parachute. These reefing means are usually disposed of shortly after inflation of the parachute to the extent permitted by the reef.

It has now been discovered that the fitment of reefing means to the parachute lines has particular benefit when the parachute is a multi-arm parachute, for example a cruciform parachute or the tri-form parachute described in UK Patent Specification 8031 762 (Serial No. 2084523). The benefit consists in enhanced stability of the parachute in both the reefed and the dereefed states, that is its freedom from oscillations, lateral or rotary, and that at the particularly important stage, opening of the parachute, when oscillation couples can be only too readily set up between the parachute and the store. This can be even more important when the parachute is a drogue parachute liable to initiate store oscillations prior to opening of the main parachute.

According to the present invention therefore a multi-arm parachute has reef means comprising a ring tie situated on the parachute suspension lines, and dereefing means for dispensing with the reef means.

According to features of the invention the reef means may be situated at 0.5 to 0.9, preferably about two thirds, of the length of the suspension lines, measured from the confluence point thereof, and may reef the parachute in use to one-third to two-thirds its full skirt diameter, the amount of reefing being chosen having regard to the extent to which it it desired to curtail the canopy drag area and hence loading. The reefing means may comprise tape or cord, for example " nylon cord around the lines in the form of a collar, and the dereefing means an explosively operated cutter for cutting the collar, initiated by a cord tension sensor or a timer and/or a barostat.

In addition to stabilising the opening of a multiarm parachute reefing means in accordance with the invention have the effect of speeding up the opening thereof to useful deployment. This effect can be further improved if the parachute has taschengurts.

A parachute in accordance with the present invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a side elevation of a reefed triform parachute, and Figure 2 is a side elevation of a fully depioyed triform parachute.

The parachute shown in the drawings has a triform canopy 10, that is with three arms 1 Oa, 1 0b, 1 Oc, a set of suspension lines 1 five per arm, a reefing cord 12, and a dereefing cutter 13.

The reefing cord 1 2 is situated at about twothirds of the length of the lines measured from the confluence thereof, and serves to reef the canopy to about half fully deployed hem diameter. The dereefing cutter 1 3 is an explosively operated blade and anvil device arranged, by means of an incorporated timer/barostat, to operate a fraction of a second after reefed deployment or when the store has fallen to a predetermined altitude.

As can be seen in Figure 1 the reefed multi-arm parachute has a balloon-like configuration, with the spaces between the arms gaping large. It is this configuration which imparts a considerably enhanced stability to the parachute and the parachute/store couple and aids inflation to the reefed state.

In a particular embodiment in which the benefits of the invention are utilised an ejection seat capable of safe operation at speeds up to 650 knots has a cruciform drogue parachute reefed to half full skirt diameter by a reef at two-thirds line length. This allows the drogue to be deployed 4 second after ejection and thus to commence as early as possible both the deceleration of and the stabilisation, or maintenance of the stability, of the seat without imposing upon the seat occupant a force greater than twenty-five times the force of gravity, at which he might be liable to injury.

In an alternative embodiment of the invention a triform drogue parachute with reefing means as above described has taschengurts on each arm formed by a 5 cm broad tape attached at the hem outside the centre of the arm and forming an equilateral triangle pocket with the hem, the pocket being open above and below.

1. A multi-arm parachute having reef means comprising a ring tie situated on the parachute suspension lines, and dereefing means for dispensing with the reef means.

2. A parachute as claimed in claim 1 and wherein the reef means are situated at 0.5 to 0.9 of the length of the of the suspension lines, measured from the confluence point thereof.

3. A parachute as claimed in claim 2 and wherein the reef means are situated at two-thirds of the length of the suspension lines, measured from the confluence point thereof.

4. A parachute as claimed in any one of claims 1 to 3 and wherein the reef means reef the parachute in use to one-third to two-thirds its full skirt diameter.

5. A parachute as claimed in any one of claims 1 to 4 and wherein the reef means comprise tape or cord.

6. A parachute as claimed in any one of the preceding claims and wherein the dereefing means comprise an exposively operated cutter.

7. A parachute as claimed in any one of the preceding claims and wherein the dereefing

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to parachutes The present invention relates to parachutes. In particular it is concerned with reefing means for reducing the opening load and drag of a multi-arm parachute. Reefing means comprising periphery or skirt limitors have in the past been employed on traditional circular parachute canopies to reduce the opening force generated by the parachute to a level which is safe and acceptable to the store or person using the parachute. These reefing means are usually disposed of shortly after inflation of the parachute to the extent permitted by the reef. It has now been discovered that the fitment of reefing means to the parachute lines has particular benefit when the parachute is a multi-arm parachute, for example a cruciform parachute or the tri-form parachute described in UK Patent Specification 8031 762 (Serial No. 2084523). The benefit consists in enhanced stability of the parachute in both the reefed and the dereefed states, that is its freedom from oscillations, lateral or rotary, and that at the particularly important stage, opening of the parachute, when oscillation couples can be only too readily set up between the parachute and the store. This can be even more important when the parachute is a drogue parachute liable to initiate store oscillations prior to opening of the main parachute. According to the present invention therefore a multi-arm parachute has reef means comprising a ring tie situated on the parachute suspension lines, and dereefing means for dispensing with the reef means. According to features of the invention the reef means may be situated at 0.5 to 0.9, preferably about two thirds, of the length of the suspension lines, measured from the confluence point thereof, and may reef the parachute in use to one-third to two-thirds its full skirt diameter, the amount of reefing being chosen having regard to the extent to which it it desired to curtail the canopy drag area and hence loading. The reefing means may comprise tape or cord, for example " nylon cord around the lines in the form of a collar, and the dereefing means an explosively operated cutter for cutting the collar, initiated by a cord tension sensor or a timer and/or a barostat. In addition to stabilising the opening of a multiarm parachute reefing means in accordance with the invention have the effect of speeding up the opening thereof to useful deployment. This effect can be further improved if the parachute has taschengurts. A parachute in accordance with the present invention will now be described by way of example with reference to the accompanying drawings, of which: Figure 1 is a side elevation of a reefed triform parachute, and Figure 2 is a side elevation of a fully depioyed triform parachute. The parachute shown in the drawings has a triform canopy 10, that is with three arms 1 Oa, 1 0b, 1 Oc, a set of suspension lines 1 five per arm, a reefing cord 12, and a dereefing cutter 13. The reefing cord 1 2 is situated at about twothirds of the length of the lines measured from the confluence thereof, and serves to reef the canopy to about half fully deployed hem diameter. The dereefing cutter 1 3 is an explosively operated blade and anvil device arranged, by means of an incorporated timer/barostat, to operate a fraction of a second after reefed deployment or when the store has fallen to a predetermined altitude. As can be seen in Figure 1 the reefed multi-arm parachute has a balloon-like configuration, with the spaces between the arms gaping large. It is this configuration which imparts a considerably enhanced stability to the parachute and the parachute/store couple and aids inflation to the reefed state. In a particular embodiment in which the benefits of the invention are utilised an ejection seat capable of safe operation at speeds up to 650 knots has a cruciform drogue parachute reefed to half full skirt diameter by a reef at two-thirds line length. This allows the drogue to be deployed 4 second after ejection and thus to commence as early as possible both the deceleration of and the stabilisation, or maintenance of the stability, of the seat without imposing upon the seat occupant a force greater than twenty-five times the force of gravity, at which he might be liable to injury. In an alternative embodiment of the invention a triform drogue parachute with reefing means as above described has taschengurts on each arm formed by a 5 cm broad tape attached at the hem outside the centre of the arm and forming an equilateral triangle pocket with the hem, the pocket being open above and below. CLAIMS

7. A parachute as claimed in any one of the preceding claims and wherein the dereefing means has a cord tension sensor for initiation thereof.

8. A parachute as claimed in any one of claims 1 to 6 and wherein the dereefing means has a timer for initiation thereof.

9. A parachute as claimed in any one of the preceding claims and wherein the dereefing means has a barostat for initiation thereof.

10. A parachute as claimed in any one of the preceding claims and which has taschengurts.

11. A parachute as claimed in any one of the preceding claims and which has a triform canopy.

1 2. A parachute as claimed in any one of the preceding claims and which is an ejection seat drogue parachute.

1 3. A parachute substantially as hereinbefore described with reference to the accompanying drawings.