From: ftr@sam.neosoft.com (Walt Appel)
Subject: BASE Article #3 - Assisted BASE Deployment Systems
Date: Mon, 24 Apr 1995 22:28:58
Feel free to e-mail me, but don't ask me to recommend specific sites. I will not recommend specific sites, nor do I recommend BASE jumping. BASE, even though it has evolved a great deal over the past few years, is still somewhat experimental and I consider it to be an extremely dangerous activity. I am posting these articles because the lessons that have been learned about BASE have cost us dearly. I do not want to see anyone hurt or killed because they were unknowingly re-inventing the sport.
In case, you're wondering about my background in BASE, I have made 55 BASE jumps, mostly freefalls from under 500 ft, from a variety of sites. I make and sell BASE accessories, e.g., pilot chutes, bridles, mesh sliders, etc., and I have been on the Bridge Day staff for the past few years.
Disclaimer: I am not now, nor will I ever be, the final word on BASE jumping. Nobody is the ultimate authority.
BASE is an extremely dangerous activity. In my opinion, the best way to reduce your chances of injury or death is to talk with as many experienced BASE jumpers as you can, learn as much as possible, *think* about it, and jump in a way that makes sense to you. This article is written from one person's point of view (mine) and you'd be nuts to consider it the best or only point of view. There is a lot more to BASE than any series of articles can present. Use the information only as a starting point.
Assisted BASE Deployment Systems
Previously, I have emphasized the idea that a BASE jumper needs to carefully choose the deployment system for each jump based on
the amount of altitude that is available for freefall and deployment, leaving sufficient altitude to safely reach the landing area. On some objects there is not sufficient altitude for freefall. It is on these objects that assisted deployment systems are used.
The term "static line BASE jump" comes up occasionally, but it is generally understood by BASE jumpers as referring to any type of BASE jump where deployment is not completely initiated and controlled by the jumper. Static lines are used sometimes, but by far and away, the most popular methods of assisted deployment BASE jumping are the "direct bag" (or DB for short) and the "pilot chute assist", sometimes called the "buddy assist". There has been some very interesting use of static lines, but since they are not in common use, I will defer discussion of static line techniques to a future
article.
The Hand-held Direct Bag
Mark Hewitt is generally credited with introducing this piece of equipment to the sport of BASE jumping. I consider it to be one of the most important innovations in modern BASE jumping because it gives reasonably reliable parachute deployments from altitudes previously considered impossible to jump safely.
When used for a BASE jump, an assistant stands directly behind the jumper at the exit point, holding the direct bag in a position that will enable the canopy, which is *not* attached to the bag, to begin deploying as soon as the jumper exits. The bag is held so that the canopy will deploy with the same heading as the jumper.
The lines, stowed in rubber bands, unstow as the jumper falls and pull the canopy free of the bag at line stretch. Inflation is pretty fast, although it seems to take forever.
I have seen various figures on distance required for full canopy inflation on DB jumps, but in my experience it varies depending on the canopy. With a DB deployment, you can generally expect an
open canopy in 50 to 75 feet. My lowest DB jump was from 125' and I have seen video of a DB jump from 63'. Don't try that at home!
DBs can be used with rounds or squares, but are most commonly used with slider-down or slider-removed square canopies.
The hand-held direct bag looks very similar to a freefall skydiving deployment bag, but there are three critical differences:
- The bag has 2 handles (loops of nylon webbing, similar to the steering loops found on steering toggles), one on each side,
- There is a "half stow" line stow band in the middle of the "hinged" edge of the bag's closing flap,
- There is no grommet in the closed end of the bag. Instead, there is either a loop for attaching a safety line, or a safety line sewn directly to the bag at the point where the bridle grommet is located on a skydiving deployment bag.
on the side.
There is a de facto standard for handles on direct bags--the right handle is red and the left handle is not red. This is important because it enables the bag holder to clearly identify proper orientation of the bag to avoid line twist. When the canopy is packed, the packer carefully notes the color code and properly orients the canopy in the bag.
The "half stow" provision on the bag allows the final stows to leave the right risers at the right side of the bag and the left risers on the left side. Try this: pack a canopy in a deployment bag and stow the lines normally, but stow them all the way to the connector links. Suppose the last stow is on the left side of the bag. Unstow *only* the right line groups from the last stow and stow them (at the connector links) on the right side of the bag.
The slack that results can conveniently be stowed if you have a stow band in the middle. BASE jumpers do this to make sure that the risers are properly oriented in the intended direction of deployment and are not twisted around one another.
The safety line, attached to the middle of the closed end of the deployment bag, gives the jumper some assurance that if the bag
holder drops the bag during deployment the canopy will still deploy. Of course all bets are off on the canopy's heading when it opens in this scenario! The safety line is generally about 8 to 9 feet, made of the same type of webbing as bridles (1" square weave nylon), and is looped around a railing or other convenient attachment point and secured using a caribiner.
I'll discuss DB packing and use in a future article.
Pilot Chute Assist
The pilot chute assist, or buddy assist technique, is quite simple. The canopy is packed exactly the same as it would be for a very low freefall, e.g., a free-packed (no deployment bag!) slider-down or slider-removed ram-air canopy with a tailpocket and a large BASE pilot chute and BASE bridle. At the exit point, an assistant holds the pilot chute securely with one hand and holds the s-folded bridle with the other, making sure that it is clear of the jumper's gear and body, and is clear of the object.
When the jumper exits, the assistant releases the *bridle* and continues to hold the pilot chute tightly until it is quickly jerked from his grip at line stretch.
It's a pretty nice technique, but has its pros and cons. On the positive side, there is no special pack job required. Just pack for a low freefall. On the minus side, it is not as reliable as the DB for on-heading openings and takes a little more distance (maybe 25 to 35 feet more) to open.
My lowest PC assists have been from about 175 feet--once with a round (a very low opening!) and once with a square. I do a PC assist instead of a DB when I've got at least 175 feet over water or 200 feet over land, and the opening heading is not critical. We are typically talking bridges for this type of jump.
Note: As good as these techniques are, they do not relieve the jumper of the need for a very clean exit and very sharp awareness! I'll discuss exits in an upcoming article.
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