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Most alpine BASE jumpers biggest fear is a wall strike:

While no one can exempt themselves of this risk, there are a number of things you can do to reduce the chance of getting near a wall, or hitting it.

Off-heading openings are a common occurrence and quick, decisive action is necessary to bring yourself back on-heading, but lets have a look at what causes off-heading openings:

1. Packing:

While your pack job can have an adverse effect on the opening it is by far the least likely cause unless you´re a sloppy packer not paying attention to symmetry. A symmetrical pack job that lifts the parachute with equal distribution of weight out of the container facilitates an on-heading opening. Make sure to check that your bridle and center cell are indeed centered and flaking of the material folds etc are equal on both sides. All other factors such as wind and body position being perfect, your symmetrical pack job will likely open on-heading.

2. Body Position:

The body position before and during the deployment, as well as your forward speed can have great effect on-heading performance. The rotation of your body once the risers load can range from nearly 0° (extreme head high) to 180° (extreme head low). While a head high, arched deployment rotates from riser load to sitting in at about 90°. In addition, depending on your forward speed at deployment, the canopy can be extracted from straight up at 0 forward speed to somewhere at 45° behind you, if you were tracking fast. If your line-stretch results in one riser loading before the other the canopy starts to inflate and fly on one side before the other. Your body´s attitude and speed can have a negative effect on the rotation and the subsequent inflation of your canopy.

3. Wind conditions:

Windy conditions can have great effect on the deployment and heading performance.

First the placement of your pilot chute and its position relative to your container upon bridle stretch can pull the canopy to one side during deployment. Vented pilot chutes have better performance to stay behind your back though strong wind from one side can pull the deploying parachute to line stretch. Once the pins are popped and the mess you called a symmetrical pack-job lifts out of the container. It is then exposed to the relative wind comprising of your deployment speed (and direction) as well as the wind present. Side winds can turn the pack-job as it gets to line stretch, while front wind usually has little effect on turning the canopy before inflation. If possible (distance to the wall is big) turn into the wind, else call off the jump if side winds exceed what you are comfortable with.

4. The effects combined:

Line twists are the result of the canopy turning during the opening process, loading the canopy single sided and a combination thereof:

If you find yourself in line twists and are lucky enough that they are in front of your face (as opposed to behind your head) don´t delay or start kicking like a skydiving b!"§$%ch. Reach above the twist if necessary climbing up your own lines. This maybe hard, but you´ll be amazed at your super human power when your life depends on it. Make the canopy turn if you´re headed toward the wall: Preferably by pulling on lines or riser links of the rear riser as you will turn and slow things down at the same time. Front riser or lines of the nose will also turn the canopy but accelerate and increase the turn radius. Once on-heading to clear air you can take your time and unwind. (no pun intended)

Cliffs of a height more than 300 meters warrant assuming a tracking position to increase the distance from the wall before deployment. While a 300 meter cliff only allows for subterminal tracking it is still a good idea to use the 4 or so seconds to squeeze 10 or 20 meters out of the total distance away from the wall. A higher cliff warrants tracking as long as you can to gain the maximum distance, though your forward speed will be much higher at deployment. This in effect will put you're deploying canopy behind you as you fall away on a forward angle from the decelerating parachute. As your risers load they will still be well behind your head at a +-45° angle. If your body position is not completely square to load the risers simultaneously, you may just find yourself in line twists that still spool up as you wonder why this happened.

Fact is: the side of the canopy on which the riser loads first starts to fly first i.e. right riser loaded right side canopy inflates and flies forward hence causing an off-heading to the left. Since the riser on the right pulled on your right shoulder, you in turn will spin to the right and find yourself with line twists behind your head not knowing in which direction you are flying. Nevertheless, if the canopy opens hard and your body is flung with energy you may actually turn to the left and spool up into line twists left. There are other factors such as the recoil action of your dacron lines ect. but lets not add unnecessary variables.

With all the antlers of rigid camera gear and extended arms to hold them in place a line twist can make it virtually impossible to move your head to see whats going on. It would take time you don´t have to determine the direction in which the canopy is flying. The scary part here is that you need to make the canopy turn if it is aiming at the wall. You can do this by reaching up as high as possible and grab a riser or lines to pull the canopy into an asymmetric state that will make it turn. However, if you were flying awy from the cliff you may actually be turning it into the the cliff if you don´t know whats going on. So,-quickly determine if you are in danger and make the canopy turn if necessary.

To reduce your chance of line twists behind your head be sure to assume a head high, arched position before deployment.

Don´t pull too high, and definitely not too low:

Some people may argue that a higher deployment is safer, but think again:

Not making use of the available altitude = less tracking distance from the wall and upon a severe off-heading opening, 180 or line twists, you may hit the wall quite a way up from the talus only to be rewarded with a number of bounces all the way down to come to rest at the bottom. That is, if you don´t hang up somewhere in between. I consider a reasonable deployment altitude about 150-200 meters AGL for trackers and a bit higher for wing-suit flyers though this may vary depending on the terrain.

In summary:

A symmetrical pack job, a square and head high body position in low or no wind conditions help you're heading performance. While you cannot see the wind or its strength at deployment altitude, it is a good idea to know the direction and estimate by looking at waterfalls, smoke or trees and flags if it´s within your limits. Make use of your available altitude to gain as much distance from the wall as possible before deployment. React quickly and decisively to off-heading openings by going with the direction if there was a lot of energy going into it or counter acting to bring the canopy flight back on line.

Your input is welcomed and I wish you consistently on-heading openings on your future jumps!


Dominik Loyen
http://www.321BASE.eu

I could not agree more on the statement above but given that you write this, can you please elaborate why do you teach on your "advanced base course" people to jump handheld slider up on box position from YO and not try to "squeeze 10 or 20 meters out of the total distance away from the wall"?

Hello Markus,

I know we are divided on this issue, but to me the body position at deployment is the most important to facilitate an on-heading performance, especially in the beginning.

Thanks for your input!

Dom

I like the straightforward way its written. Do you have more introductory writing about BASE jumping???

'nuff said.

Unfortunately, I don't think it's that simple. Especially when we are talking about slider down openings.

I've been on loads from slider down objects in high cross winds where all five jumpers experienced exactly the same off-heading opening. I find it extremely unlikely that it was their body position that caused this, especially since I've seen perfect body position and wild flailing result in exactly the same off heading in these conditions.

Likewise, I've seen perfect body position and zero wind result in off headings, sometimes obviously from PC orbiting, and sometimes from no obvious factor.

There are a lot of things that can cause an off heading. Asserting that there is one cause that applies to all jumps, jumpers and conditions is likely an exercise in extreme overconfidence.

nah.

i believe fully that body position is the most important contributing factor to heading performance.

jumping in high crosswinds... well you said it right there.


i also follow the rule, out delay the x wind. if it's high, you won't and you're foolish to think it won't affect your heading.


relative wind counts from fixed objects too.

what looks like perfect body position isn't always the case. obviously, "perfect body position" is not going to help if you only have one leg strap tightened, or one riser connected.

there are no absolutes.


every off heading i have experienced (which is a very low occurrence, currently 93.37% on heading) i can attribute to bad body position, or were anticipated before exit due to strong cross winds. but of course, i can only be sure of what i do myself and what has worked for me.

My rule of thumb is: Fall faster than the wind speed. If you are falling slower than the crosswind, I expect the crosswind to govern the opening. If you can delay long enough for your fall rate to exceed the wind speed, you are back in charge.

Yet another reason why deeper delays are usually safer in BASE.

I think its a fallacy that if you have line twists 'that you can reach above them/climb above them and steer' the canopy. In 640 jumps I've had 4 sets of decent line twist and on every occassion I could not climb above the line twists and had to resort to kicking out.

I'd love to hear from people with a)jump numbers stated, b) number of jumps with line twists and c) if they could 'climb/reach above' and steer the canopy.

For the record I'm not a fat boy and am pretty reasonable at chin ups :-)

I've been able to turn above line twists.

I also had a student two weeks ago who was able to turn above twists on his 13th jump.

Both of these cases were on slider down jumps.

I think that it is possible to develop twists such that you can turn above them.

I wonder if there is a difference in likely twist mechanism between slider down and slider up openings?

Neil, were your twists slider up or slider down?

All slider up. Dacron lines. Physically impossible to pull lines down. In part because the twists started above the height that I could reach.

I've had a 180 with multiple linetwists from a 102 meter B. Perfect exit, 0 winds. Packjob as always.

Yes there is.

Linetwists will occur on the location that requires the minimal amount of energy to constrict all the lines together. Obviously, this point is located where the lines are (on average) the closest to eachothers.

Whithout slider, that point is located at the harness-elevators junction. The only thing that can move the twists further up is your head being sqeezed between the risers.

Slider down, the twisting point is somehow spread on the risers, with a tendancy to be towards the harness-risers junction point (since the slider is generally just a little wider than the shoulder straps)

Slider up, the twisting point is spread further up, between the risers and the current position of the slider. So if the linetwists are starting when the slider is still close to the canopy, you have two spindles of lines almost parallel to eachother, between the harness and the canopy. The lines will start to twist in between, then the slider is going to push it down towards the risers, and it will stop at some point depending on the line friction and the slider size.

From my experience, it very unusual to have the canopy turn more than 180-270°

Multiple linetwists generally occur when you add to that phenomenon the rotation of the human body due to the inertia of the legs bouncing sideways on opening. Correct position and muscular tension can reduce the body momentum a lot - this is probably why experienced jumpers still have 180's but less multiple linetwists.

Obviously, it's good to have a slider starting immediately to slide down rather than staying up on the canopy for soft openings.

I've had a handful of linetwists slider up on canopies that tend to open hard - the only few cases where i wasn't able to climb over it was with a wingsuit (after dezipping) - which tend to give me softer and slower openings when i'm not pulling at full speed.

You forgot to mention: "Don't jump advanced objects if you haven't yet built the skills necessary to deal with all possible outcomes".

If your "students" can not deploy symmetrically from a tracking position why are you even taking them to the Valley?
As their teacher would it not be better to recommend other sites for them to jump until such a time as they are ready for the Valley?

Best thread in a long time!!

Hopefully the kids jacked up
on Mountain Dew like Spider
Monkeys read every word.

RE: Steering

360+ BASE Jumps, most Slider-OFF,
only 1 Slider-up 180 w/ Twists from
a tall A, off heading due to shortish
delay and cross wind, did not even
think to steer, only untwist, flew in
between a set of wires, and only
alive today due to karma & luck.

This is very true.

In my experience, slider down line twists almost always develop _after_ the canopy is flying. The off heading canopy surges in one direction and the jumper is headed another. The jumper is then "slingshotted" back around under the canopy, and spins up into twists after opening. There is almost always a short time when there is a half line twist (or less), before the jumpers body spins up into more twists. Jumpers who are stiff during this period tend to be spun up harder. Jumpers who are more relaxed and responsive can often minimize the twists, or even stop them altogether.

Experienced jumpers can generally relax enough to just feel things out, but beginners would probably benefit from some instruction in terms of how best to reduce twists.

In general, my experience is that twists are more severe with a tracking body position (head low and arms and legs in tight). The head low position makes the twists more violent, and the lower rotational inertia of the jumpers body allows more twists to develop.

I think that a more head high (or standing) position, with a more relaxed (arched, rather than tracking) position at line stretch can help reduce twists. Unfortunately, it can take a fair amount of practice to track until the last moment (for best separation) and then return to a relaxed, head high arch after line stretch.

Does anyone else have any thoughts on the best body position to assume during opening to reduce the possibility of twists?

Here is a good tip I got once:

On deployment try to close your legs
and look at the horizon so you load
the harness evenly during inflation.

Hi Neil, I once climed above a linetwist to turn my canopy into the wall, no joke :-) of couse this was not my best idea so I climed up again and turned it away again. I therfore climed above linetwists already two times!

Were you slider up or slider down, Mikki?

line dump

Always check your velcro. Line dump can cause line twists too. When my buddy landed we looked at his tail pocket and the velcro was blown open. Looking at the video it looks like line dump put slack in the lines and the bridle causing the canopy to spin like a noisy whizz wheel (see picture below for description of noisy whizz wheel)

Slider up from Smelvegen, about 5 years ago. The PC fell over the nose at opening so I thought I was flying backwards :-)

I prefer to remain as large as possible as I feel that the smaller your surface area the easier your body will be spun around ie. like those figure skater chicks. May not help prevent 180s but I feel it does a lot in preventing line twists following a 180. And I've had some pretty violent 180s :-)

No one has mentioned, yet I find relevant especially for slider off jumps = properly tuned and tested deep brake settings.

If you're jumping with the same brake settings your canopy came with, you might find it's not really that "deep". I found mine flying much different following recent weight loss.

http://www.basejumper.com/...orum.cgi?post=471986

Definitely.

Unfortunately, brake setting has become something of a lost art these days.

Properly tuning custom DBS to the jumpers body weight can greatly increase the time the jumper has to respond to a serious off heading.

In general, I recommend adding a 3rd setting to the brake line when setting custom DBS, because in a tailwind condition the custom DBS (which is invariably deeper than the deeper factory setting) can cause deployment stall.

When I tune brakes I prefer to leave the lower control line with:

Factory Shallower: for slider up jumps
Factory Deeper: for slider down jumps from non-solid objects where a tailwind is possible
Custom Deep: for solid, slider down objects

Can't 'Factory Deeper' brakes also be used for SU jumps? I guess they should be shallow enough not to stall the canopy on SU opening??
I personally use my custom deep brakes for everything, SD and SU jumps. So far have worked well. Even if the canopy would stall in high tail wind, the wind would still push the canopy away from the object. (and also in case of an 180)
I only use shallow brakes (or Factory Deeper in this case) for very low jumps, so I don't stall the canopy when I need to flare almost immediately after opening.

In a deployment stall, the canopy slides backward. I've seen two tail first object strikes happen in this manner. It's quite counter-intuitive, but despite jumping in a tailwind (actually because of it) the canopy can move backward toward the object.

If you are using custom deep brakes for slider up, I would suspect they are not actually as deep as I would put them for solid, slider down objects. A good custom deep setting (and often a factory deep setting, but that depends on a lot of variables) can deflect the tail far enough to stall the slider up canopy during deployment, resulting in a "stuck" slider, which has to be pumped down with the toggles.

But does all this apply for canopies with vents?

I made myself 3 custom deep brake settings, now I jump using the middle ones, since when I jump on the deepest one, my canopy stalled a bit on SD jump. the middle one is about 3-4 cm shallower than the deepest one (the one that cause the stall). So I would guess mine are still pretty deep, but still the canopy doesn't stall on SU. I have 5 vents on my troll

I've owned two canopies that had customized DBS and were then retrofitted with vents. In both cases (a Troll and a FOX) the vents actually made the deployment stall issues worse, and I had to lighten the custom DBS after the vents had been installed.

Can you think of the reason why that happened? Could it be the air coming from vents and spilling out of the nose?

Yes, I believe that's the most likely cause. Air flowing in through the valves strikes the top surface of the canopy, and is deflected in all directions (including toward the nose). Some of it pushes out the nose and gives a slight rearward thrust, which exacerbates the deployment stall issue.

Cliff strikes happen. We can work on gear and general procedure but most people forget about the human element of tunnel vision and panic. The biggest problem that I've encountered with a 180 near a wall is the tendency to be distracted by the wall in front of me. I literally have to look away and guide strictly by peripheral vision. Front vision is slow to respond. That's why a lot of martial artists use peripheral vision. You'll just sit there in the few moments prior to impact thinking "wow, that's an interesting cliff. Look at all those details," and then WAM! you just hit the damn cliff. It's amazing that people can now survive a cliff strike given gear. And people jumped really gnarly cliffs for years prior to good gear relying on a toolbox of other tricks. I'm so glad gear has improved.

That is my setup with my Troll. I use my customised DBS (maybe good 10cm deeper than the factory setting) for all slider down and the factory DBS for all slider up. I never jump the factory shallow brake as I feel there is absolutely no use for it. Keep in mind though that vast majority of my SD are from cliffs where high tailwind is obviously not an issue.

I'm curious how you guys tested your custom DBS?

Here, I am adjusting in very small amounts and repeating test jumps, using the following pattern:

Open Canopy
Correct to on-heading using riser
Let canopy fly straight 3 seconds with brakes set
90 degree riser turn
Let canopy fly straight 3 more seconds
Switch to toggles to fly/land

I typically repeat this drill 5-7 times adjusting the DBS very slightly (around 1-2cm) in the final repetitions, to find the DBS. I usually overshoot and end up with a brake setting that is too deep (stalling the canopy) and then back off to find the custom DBS, giving myself about an inch of safety margin beyond that point.

What is your process? I'd always imagined that this process is much easier (and therefor can be done more precisely) from a bridge high enough to allow this drill for evaluation of the setting, and which can be done repeatedly on back-to-back-to-back loads.

Do you have 4 or 5 upper control lines?

I make myself 3 brake settings about 13-18 cm higher than the factory deep setting (based on own experience on jumping on Trolls). Then I jump still with factory settings and pull my toggles until the canopy starts to stall, and then I use the setting which is a bit lower than this point.

Do you test the responsiveness of the setting with canopy drills on subsequent jumps?

Do you ask because some settings can be simultaneously not deep enough to stall upon opening but too deep to correct heading with risers while toggles are still stowed?

Yes.

It's possible for the canopy to not stall at deployment, but still have brakes deep enough that it is not responsive to riser input. The riser input (on just one side) can result in a stall straight down rather than the desired stall/turn.