sobota, 18 marca 2017

The reserve parachute line twist, WTF?


The reserve parachute line twist, WTF?

It seems that many skydivers are shocked by reserve parachute twisted lines video published on FB. Wingsuit, stable malfunction, tension knot, emergency procedure and reserve is twisting. So what is going on?

 

Wingsuit.

We are entering an interesting phase of skydiving, where the jumpers test the new assemblies. However, the main  and reserve parachutes are tested by manufacturers and jumpers in different conditions. Ever increasing in sizes WSís generate more and more turbulence and increasingly interfere with the deployment process of both main and reserve canopies. While the phase of the main parachute deployment is better thought-through and trained (jumpers care about the position, apply longer pilot chute bridle, even modern containers are modified - as the last Sun Path product) than the reserve parachute opening is quite a fresh part of parachuting history.
On my channel I have already addressed the WS turbulence forming issue and main canopy mysteriously sucked in after it was partially deployed.


This video is a proof of how interesting and difficult for the jumper phenomenons take place in the area of low pressure and in the zone of greatest turbulence behind his more and more size increasing WS. During opening of the main parachute, while maintaining the correct figure, one can count on a symmetric exposition  of the canopy leading edge. Of course, the ratio between the main canopy and WS sizes seems to be very significant. The larger the WS, the greater should be the canopy, if we consider the turbulences. I know this is a very difficult subject considering ones functioning in the herd;)

In the video that shocked part of the society you can see a nice, stable deployment of the main canopy, which is, according to the comments of more experienced WS skydivers (and in my opinion too) small, perhaps too small. However, good body position and good pilot chute throw-out is allowing for the nice start for the canopy deployment.
Packing, lines condition or other cause is leading to malfunction known as tension knot (so it seems to me at least). It seems that the jumper has already experienced such a malfunction, and perhaps he had been able to fix it before, because he is trying to regain the canopy correct state for a long time. Very long time. I'll say that itís a shame that such an experienced parachutist, who represents the brand for gladiators, shows the example of such an improper behavior. It took him 35 seconds to fight  with the main parachute. On the plus side you have to include that he is constantly controlling the altitude and acting in accordance with his plan. If, for example he is additionally a BASE jumper, it is possible that the decision altitude for cutting away the main may be lower than for the average jumper.
At some point however, he is cutting away from his main parachute. And here comes the first interesting case. The jumper is waiting 3 seconds after main canopy cutting away before pulling the reserve. I think that it was his intended action and this could have a major impact on the further development of events. During those 3 seconds the camera image is very stable. It can be assumed that the air resistance of the lower part of his suit began to set him horizontally, thus exposing a large area of the suit perpendicular to the relative wind. He has provoked the most unfavorable situation for reserve parachute deployment initiation.

The deployment of the reserve parachute is initiated by the spring-loaded pilot chute placed at the widest point of the outline of the jumperís body. It is close to the center of mass and in the flat position it needs to pop up above a turbulence zone. Flat, neutral position is the WORST position to deploy the reserve parachute regardless of brand, size, container type and condition of the the spring. During tests on dummies it can be hardly expected that they will keep flat, stable position after throwing them off of the aircraft. And that's how the producers carry out the tests. Watch movie about spring loaded pilotchute hasitating in the low pressure zone and imagine how much bigger is surfice of WS



After three seconds turbulences increased and the pilot chute was in their zone. If the jumper after main canopy cut-out immediately pulled a reserve, then the scenario would be different. How to define "immediately"? Experienced jumper is able to feel that both risers 3-rings have been released and he has parted from canopy, it just takes less than a second to realize for the brain flooded with adrenaline. These three seconds were associated with a very dangerous acceleration trend. Equally deadly like the attempt to return to flat position - the worst position for the reserve pull. Many people were killed by delaying the reserve pull out and the patches buying advocates, instead of training sell another RSL boloney. If someone MUST use the RSL he should abandon skydiving. When we do everything as if we didnít have the RSL and AAD, only then these protections make sense.
In my opinion freebag gets hit by the turbulence during reserve deployment process and at this time the jumper is turned over with his legs to the right. You can recognize that by his left forearm pressing on the left riser from the inside. The left part of the reserve is more exposed to the incoming air, left side cells deploy earlier and pull up and forward while the right side is resisting. This is just my supposition but I'm firmly convinced that the reserve deployment has been strongly affected by the turbulence from the WS. But the reserves were never designed for that! No one ever has thrown the dummies wearing WS suites within the TSO or ETSO!
So the left part is moving on while twisting the lines and clenching them in asymmetrical arrangement conducive to further turning .
From this moment, we can see a pretty, fully determined attitude of the jumper, who, despite the legs blocked by the suit is quickly unscrewing from the malfunction and is landing about 13 seconds after canopy is stabilized. In fact there is no drama yet and his plan was bloody good ;D.

Reserve parachute

Reserve parachute assembly with harness integrated with the container is carefully tested by the manufacturer before it is marketed.
The parachute in the video is PD Optimum. This parachute collects unflattering opinions in the forums discussions. Parachute is reportedly bad because it turns, because it dives and is made of thinner fabric, which perforates.
But I guess it is not the true. I can't say about the holes because I haven't seen them. If I see and educate myself about selection of the fiber thickness and fabrics production technology of this and other reserve canopies on the market then maybe I'll write something for you. For now I'll keep my mouth shut;)


The fact that a pregnant woman walks in dungarees does not mean that she became pregnant from this clothing, or clothing otherwise mysteriously caused this blessed state. It's just a coincidence, because the woman is comfortable in these pants. The reason for the incident was completely different, and you will find this excellently from the new education program guidelines ;D:D:D

The fact that PD Optimum gets more line twists (if it's the fact indeed, as I do not know any actual statistics), doesn't mean that something is wrong with this reserve. Whom to, in fact, this product is addressed by the salesmen?
It's the parachute with thinner fabric to give the jumper a bit larger area of the canopy squeezed into tiny container. And nowadays we are talking about the main parachutes very often smaller than 100 square feet! Proportionally so we also have to deal with such a tiny reserves. Except that the mains have a completely different profiles, these are the kites that can do a lot in the right hands combined with the appropriate brain. And the reserve is the traditional rectangular canopy, with seven cells, sewn of fabric partially breathable.
So it gets on the backs of the elite and those who would like to be one. Usually. It is known that the action cameras are bought by ordinary bread eaters who want to feel a little bit of this nerve which only Heroes of The Sky have.
Reserves so small, usually overloaded against the manufacturer's instructions, used in the relatively new disciplines can pull hilarious pranks. Even deadly pranks.

Size DOES matter.

How many times I've written about it, and told you? Gazillion? Well, I'll write again. As far as one can, to some extent, bend the rules for the selection of the main canopy (and jump himself in single  or from the balloon) without disturbing too much the safety then the lifesaving equipment should be selected according to the principles of the manufacturer. WL of the reserve CAN NOT be exceeded if the jumper wants to remain relatively safe. If this is exceeded then you have to expect major complications. The risk needs to be calculated.

The decisive altitude for pulling the reserve.

This is the foundation of safety! The higher the better. To have enough altitude you must also choose the right altitude of the main canopy development. And the smaller this one is the aggressively reacts during a malfunction. I believe that in today's skydiving pilot chute should be pulled at an altitude of 1200 meters. It's not just about the action during malfunction but also bigger jumpers number in the sky and growing average WL. Getting faster and faster, harder and harder on the order in the sky and the jumpers vertical separation.

Emergency procedure practice

We pull the reserve parachute immediately after cutting away he main canopy, REGARDLESS of the position. We must not cut away the main canopy without having a well-held grip on the reserve pull out handle. EVERY jumper should practice the procedure and at least once a year do it in suspended harness.
Do not cut away from the main canopy below 300 meters, it may be too low to deploy the reserve parachute.



Author: Iwan from Atmosfera
Translation: Andrzej Przygodzki from Atmosfera

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