There are only two ways to end a freefall. One is to open your parachute, and the other is not to. No one wants it to end the second way. Statistics show that the overwhelming cause of skydiving fatalities are due to the jumper not using a perfectly functional parachute in time. Why does it happen?
In order to open your parachute safely, you need to know two things: when and how. The when was discussed in the previous chapter. Altitude awareness is critical and the loss of it is a life threatening situation. The problem can be compounded if the skydiver, running out of altitude, is unfamiliar with his equipment and has trouble deploying his parachute. Add the possibility of a malfunction to low altitude and unfamiliar equipment and you have a perfect recipe for disaster. Therefore you must always watch your altitude and before you ever get on an airplane you should be totally familiar with your equipment.
The sport parachute, called a rig in skydiving jargon, is a very simple machine. It must include two canopies, a main and a reserve. The components must be TSO’d, meaning they meet government technical standard orders that require high manufacturing and testing standards. All rigs are worn on the back and consist of similar components. A look at the diagram will show that a rig consists of the deployment system (pilot chute, bridle, and bag), canopy, suspension lines, steering lines, toggles, risers, and harness/container. Deployment is initiated when the container opens and the pilot chute enters the relative wind. The pilot chute may be packed inside the container (all reserves and student mains) or kept in a pouch outside of the container and pulled out by hand, which most experienced jumpers prefer. The pilot chute acts as an anchor in the air, while the jumper continues to fall. As the two separate, the bag in which the canopy is folded is pulled from the container. The parachute's suspension lines, carefully stowed on the outside of the bag, are drawn out until they are fully extended. The bag is then pulled open and the canopy comes out. It immediately begins to inflate as the cells fill with air. Inflation is slowed by the slider which prevents the canopy from expanding too fast. It usually takes three to five seconds from deployment of the pilot chute to full inflation of the canopy.
Over the years, parachute design has been refined to a remarkable degree. In fact, square parachutes have no known inherent design malfunctions. Theoretically, given proper packing, a stable deployment, and barring material flaws, a square parachute will never malfunction. However, we don't live in a perfect world, and malfunctions are common enough that no sensible person would intentionally jump without a reserve. The malfunction rate for sport parachutes is about one in every thousand deployments. Nearly all are preventable.
The catalogue of possible malfunctions is long, but all you really need to know is that any parachute must have two characteristics. It must be open, and it must be safe to land. Otherwise it is a malfunction. The first characteristic is determined at a glance. The second one, if there is any doubt, is determined by a control check. Should you have a malfunction, the response is simple – cut away the main and pull your reserve. The main parachute is released from the harness, then the reserve container is opened, starting the reserve deployment sequence. For all practical purposes, main and reserve deployments are identical except that the canopies may be of different sizes.
Most parachutes used by experienced jumpers have a separate handle for each function of the emergency procedures so you will need some special training when you progress to your own gear. Also, at Skydive Airtight we use only square reserves. If you travel to another drop zone be sure you receive training on their equipment, and find out if the reserve is round or square. Round reserves mean you will need special training.
The first factor in preventing malfunctions is a simple one: don't leave the airplane with an existing malfunction. This means that you should always have your equipment checked by a knowledgeable second party to be sure nothing is misrouted or damaged. Prevention extends to packing. When you learn to pack you will learn to inspect the canopy. In the student phase, you have to trust your jumpmasters and packers to be responsible for the condition of your parachute, but you will eventually assume all responsibility. Because of the possibility of a jumper making a mistake, our reserves are inspected and packed by a specialist who holds a Rigger's Certificate issued by the U.S. government, thus ensuring that at least one parachute on every skydiver is technically sound.
The second factor in malfunction prevention is one you control: body position. If you think back to the deployment sequence described earlier, the importance of a stable opening becomes apparent. Since the parachute is on your back, if you are facing the relative wind in a good arch it will deploy straight out behind you. If you are unstable, it must find its way past you - between your legs or around an arm, for example. In this situation, the pilot chute could entangle with you, stopping the deployment sequence. Another possibility during an unstable opening is that the lines will feed out unevenly, creating the potential for a line knot that could keep the slider from coming down or deform the canopy to the point that it cannot fly properly. Don't forget, however, that stability is not as important as opening in the first place. Pulling at the correct altitude always takes precedence over pulling stable. An unstable opening does not always result in a malfunction; parachutes are so reliable that the worst that usually happens is a few line twists. Not opening has far worse consequences.
TEST YOURSELF
1) While you are a student, your decision altitude, sometimes called your hard deck, is 3,000 feet. If you initiate main deployment at 4,500 feet and nothing happens, how many seconds will pass before you reach the decision altitude? How many will you have used counting and checking before you realize you have a problem?
2) If you know you have a malfunction, why should you pull your reserve at once instead of waiting until the decision altitude is reached?
3) In the old days, skydivers wore their reserve mounted on the front of their harness. If you had a chest mounted reserve, what body position would you want to be in for reserve deployment?
No comments:
Post a Comment