How BASE Jumping Works

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Introduction to How BASE Jumping Works

Image courtesy Lyle Cameron Jr./ Larry Walsh AirTrash
Carl Boenish, the founder of modern BASE jumping. See more pictures of skydiving

For BASE jumpers, leaping out of an airplane at 15,000 feet and freefalling at well over 100 mph isn't quite daring enough. To make things more interesting, they jump off various cliffs and man-made objects, usually at a low altitude with only a few seconds to deploy the parachute, and virtually no time at all to deal with problems or malfunctions. BASE jumping is so incredibly risky that it's actually illegal in many places.

The name "BASE jumping" is an acronym for the four types of objects that jumpers leap from:

Buildings
BASE jumping from buildings and monuments is difficult, since most places have security, locked doors and other obstacles to prevent someone from climbing to the top and leaping off. Many BASE jumpers prefer skyscrapers that are still under construction for this reason.
Antennas
Antenna towers are popular jumping points because they are often as tall as the world's tallest buildings, are easier to climb and have less security. They are often found in out-of-the-way places as well.
Spans (Bridges)
Spans, or bridges, have to cross over large canyons or gorges to be suitable for a BASE jump. The most famous BASE jumping bridge is the New River Gorge Bridge, where U.S. Route 19 crosses over the New River near Fayetteville, WV. One day each year the bridge is opened to legal BASE jumping. That day (with the accompanying festival) is known as Bridge Day.

Image courtesy National Park Service
The New River Gorge Bridge in Fayetteville, WV.
Earth
Earth refers to large natural formations that are suitable for BASE jumping -- cliffs, canyons, fjords and gorges. BASE jumping actually began on a massive rock outcropping in Yosemite National Park known as El Capitan.

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El Capitan in Yosemite National Park

History
There were isolated jumps off fixed objects in the 1960s and 1970s, but they were one-off stunts that sometimes ended badly. In 1966, two skydivers jumped off El Capitan, but their equipment was not designed for a BASE jump, and they both suffered injuries. In 1975, a jumper leapt from the World Trade Center's south tower and was arrested when he parachuted to the ground [ref].

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Modern base jumping was invented by Carl Boenish in 1978. He became convinced that modern skydiving equipment could allow for a safe jump off El Capitan. After several scouting trips, Carl and four friends hiked to the top and Carl filmed the four of them jumping. Everyone landed safely. Shortly after that, Carl and several other BASE pioneers came up with the BASE acronym for this kind of jumping -- an early alternate idea was BEST jumping (Bridge, Earth, Span, Tower) [ref].

Carl developed the BASE number system soon thereafter. Anyone who accomplishes a jump is recorded in a notebook. When they complete one jump of each type, they are assigned a BASE number in sequence of the people who have completed all four types before. Carl was BASE number 4. In 1984, he died while BASE jumping in Norway. Nobody witnessed the jump, but it is believed that he hit a rock outcropping [ref].

We'll take a look at how a BASE jump is performed in the next section.

BASE Jumping Basics

Image courtesy USMC
Modern BASE jumpers use a ram-air parachutes so they can control the speed and direction.

Image courtesy USMC
Early BASE jumpers used round parachutes, which cannot be controlled as well as rectangular ram-air parachutes.

Before we get into any discussions on the techniques and equipment used in BASE jumping, we need to make something very clear: BASE jumping is extremely dangerous. There is no margin for error. A slight mistake, or a little bad luck, and death is the result. BASE jumpers generally have about 100 regular skydiving jumps under their belt before they ever attempt a BASE jump, and they usually have an experienced BASE jumper who mentors them on the skills necessary to jump safely. No one should attempt BASE jumping without a lot of thought, training, experience and a good life insurance policy.

BASE jumping is essentially a variation on skydiving. For a good explanation of skydiving and the equipment used, check out How Skydiving Works. BASE jumpers use modern ram-air parachutes (the jumpers injured on El Capitan in 1966 were using older round parachutes, which contributed to their problems). Ram-air chutes are rectangular to give the jumper greater control over direction and speed once it has been deployed. There are some key differences between skydiving gear and BASE jumping gear, however, so BASE jumpers need special equipment and techniques. A parachute made especially for BASE jumping costs between $1,200 and $1,500.

BASE jumpers have to overcome two major obstacles: low altitude and the proximity of the BASE object. Skydivers typically open their chutes at around 2,000 feet. This gives them time to deploy the parachutes gradually (reducing line tangles and a sudden jerk on the diver) using a device called a slider [ref]. It also gives them a little breathing room. If there is a problem with the main parachute, they can still deploy their back-up chute.

But many BASE jumps start out well below 2,000 feet. While jump sites such as El Capitan and Angel Falls in Venezuela are around 3,000 feet, they are the exception. Skyscrapers and antenna towers are usually 1,000 to 1,500 feet tall. As a result, jumpers have to deploy their parachutes quickly.

A few alterations in basic skydiving equipment help to accomplish this. For example, some BASE jumpers use a larger pilot chute. This is the small parachute that drags open the main chute. Larger pilot chutes catch more air, create more drag and open main chutes more quickly. They are also helpful because low altitude jumps force jumpers to open their chutes at a lower velocity -- they haven't been falling long enough to achieve a freefalling human's terminal velocity (around 120 mph). Lower speeds mean reduced air pressure in the chute, so a larger chute is more effective. Because many BASE jumps are so low that only about five seconds of freefall are possible before impact, some BASE jumpers don't bother packing back-up chutes. If the main chute fails to deploy, or deploys incorrectly, there isn't the time to cut away a malfunctioning chute and deploy the back-up.

The BASE Jump

Instead of a ripcord, BASE jumpers release their pilot chute manually. For higher jumps, the pilot chute is stowed in an easily accessible pocket or flap, and the jumper pulls it free to release it at the right moment. This leaves both hands free during the brief freefall. If the jump is shorter, the jumper usually just holds the pilot chute in his or her hand [ref].

Image public domain
Angel Falls, Venezuela, a popular BASE jump site.

For jumps 300 feet or lower, BASE jumpers have almost no time at all to freefall and deploy a chute. They use a static line to deploy the chute automatically. This line runs from the jumper's pack to the object. During the jump, this line pulls the main chute open, and then separates from the pack.

Image courtesy Rodolfo Clix/Sxc.hu
Jumps from antennas are often the lowest and most dangerous types of jumps.

Skydivers don't have to worry about object proximity. They have to worry about hitting the ground, not the side of a building or cliff. But most BASE jumping fatalities are due to object impacts, rather than freefalling to the ground. The need for fast parachute deployments compounds the problem -- these deployments can send the jumper off into an unintended direction, such as straight into a granite wall. Jumpers call this an "off-heading opening."

Jumpers try to compensate by using a smaller ram-air parachute, one with seven air cells instead of nine. Modern parachutes designed specifically for BASE jumping have started to incorporate modified sliders that ease the suddenness of deployment, making it easier to avoid an off-heading opening.

Body position at the jump and deployment are key factors in determining the success of a jump. Jumping head first and rotating forward is incorrect. Keeping the body oriented so that the jumper is facing down, with the chute deploying behind him, is vital. On jumps with a few seconds of freefall, jumpers use tracking to direct the body away from the object. This means that the jumper "flies" away from the object using the aerodynamic shape of the body, instead of just falling straight down.

Canopy skills are vital as well. Once a ram-air parachute has deployed, the jumper may be carrying a great deal of forward velocity. Being able to steer properly and avoid slamming into the object could literally be the difference between life and death.

Next, we'll look at the status of BASE jumping and some statistics.

BASE Jumping Legality and Statistics

Image courtesy Razvan Multescu/MorgueFile
Several BASE jumpers have been arrested after jumping from the Eiffel Tower.

BASE jumping has always been a fringe sport to some extent. This due to the danger, the fact that many "traditional" skydivers feel it gives their sport a bad image, and because jumping off of building, towers and bridges is against the law in most places. Even if the jump itself weren't illegal, gaining access to prime jumping spots often involves trespassing on private property, picking locks, climbing fences or deceiving security guards.

The National Park Service frowned upon the first few BASE jumps from El Capitan. Parachuting in national parks was prohibited at the time. For a short time, officials at Yosemite National Park allowed jumpers to apply for permits and jump from El Capitan legally. However, after a few months, they decided that jumpers were not following the rules and were causing environmental damage, and they have forbidden jumps ever since. Today, if you are caught BASE jumping in a national park in the United States, you face up to $2,000 in fines, and the cost of any rescue operations that may be necessary. Park authorities can confiscate all parachuting equipment, as well [ref].

BASE jumping from buildings within cities is almost always illegal. The risk of pedestrian injury and traffic disruption are too great, although the vast majority of building jumps take place at night or at dawn. Police have promptly arrest jumpers who have leapt from the Eiffel Tower and the St. Louis Arch.

Image courtesy Gard Karlsen
Kjerag on Lysefjord in Norway, a popular and legal BASE jumping location.

There are quite a few places to BASE jump legally. Kjerag, on Lysefjord in Norway is a very popular location, and jumps remain legal there [ref]. Various natural formations throughout Europe are available for legal jumping as well. However, man-made objects with legal jumping are difficult to find, so anyone with a BASE number has probably had to break a law to get it. Bridge Day is the one obvious exception.

The specific locations of BASE jumping spots, whether legal or illegal, are closely guarded by BASE jumpers. There are several reasons for this. One is that many BASE jumpers want their sport to maintain a secretive and "outlaw" nature. Publicizing BASE jumping, or letting too many people into the sport, makes it harder to perform illegal jumps because authorities will be on guard. One of the worst things a BASE jumper can do is something that will make jumps more difficult for other jumpers. This includes getting arrested, getting killed or injured or otherwise drawing attention to the illegal side of BASE. BASE jumpers broke into the apartment of a jumper who was arrested attempting a daylight jump in Atlanta and beat him for retribution [ref].

The secretive nature of BASE jumping means that many of the statistics about the sport have to be taken with a grain of salt. No one keeps exact records on the many jumps (and deaths or injuries) that happen at night, in the wilderness or with no one else around. However, the current BASE number is above 1,000, and the World BASE Fatality List reached 97 on May 6, 2006. The highest BASE jump was probably a jump off Pakistan's Trango Towers in 1992. Two jumpers successfully leapt off a cliff over 19,000 feet high [ref]. That's about 4,000 feet higher than most skydiving planes go. The lowest feasible jump is anything around 250 feet, although using a static line with a short length, a jump could be accomplished with a full parachute deployment from much lower -- it just wouldn't be much of a jump. Finally, the first person to jump all four BASE types was Phil Smith. He will always be BASE #1.

For lots more information on BASE jumping and related topics, check out the links on the next page.

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