Assalamualaikum.. Selamat Datang...

Assalamualaikum.. Selamat Datang...
Hari Keputeraan KDYMM ke-61, 2007

A Picture tells a thousand stories

A Picture tells a thousand stories

Monday, June 18, 2007

Landings

There are two goals when landing your parachute: the first is to land safely and the second is to land where you want to. Clearly, the first goal is much more important than the second one, yet a surprising number of skydivers have had the opportunity to consider their values at leisure while recuperating from landing injuries. A parachute is only as safe as the person operating it.

As soon as you have determined that your parachute is functioning properly, it is time to start thinking about the landing. Look for potential landing sites - any level area free of obstacles will do but we try to land at an established point, our student landing area, if we can. Usually you can get back over this landing area with at least a thousand feet of altitude left. If this is not the case check the area below you and between you and your target for possible hazards; if you are not positive you can make it safely to the planned landing area, you must select an alternate site. Do not go below the thousand foot mark without making a firm decision about where you will land!

Assuming you have made it over the target above one thousand feet, you should turn into the wind and check your ground speed. This is especially important on windy days. Remember the higher the wind speed is, the less ground speed you have when holding, and while running with the wind your ground speed will be higher. Keep this in mind and avoid getting too far down wind of your target area. (Helpful hint: if you can find your canopy's shadow on the ground it will show you exactly how fast you are going!)

As you hold into the wind you can make a rough guess as to how far you could fly in, say, 250 feet of vertical descent. Take that estimated distance and lay out an imaginary line of that length from the target to a point downwind. Now just work your way to that point and stay near it until you are about three hundred feet up. Turn towards the target. If your original guess was good, you would slightly overshoot the target. A small "S" turn - ninety degrees one way, then 180 back to the approach, and ninety degrees back into the wind - will line you up on a good final approach. As long as you start your final approach a little high, you can continue these "S" turns to adjust until you are on approach at the right altitude.

Remember that your first priority is to land safely, not necessarily in the target. You may have to share the landing area with another canopy, in which case you need to avoid flying in front of or near them. For example, if you are on one side of the target and another student is near the other side, stick to your side rather than aiming at the middle. Be careful to always look before you make a turn and assume the other canopy pilots may not see you. Whoever is lowest has the right of way. Also look for dust devils. They can turn or even collapse your canopy and should be avoided.

Most skydivers like to set up their final approach by using a pattern similar to the kind airplanes use approaching an airport. After your ground speed check at one thousand feet, work your way down wind until five hundred feet. Then turn cross wind (90 degrees to the wind direction) until you are over that imaginary point where your final approach begins. This type of pattern lets you observe wind indicators as you refine your estimate of where to turn onto final. Another useful tip: the more turns you do, the harder it is to tell where you are going, because your descent rate and forward speed change in a turn. A few smooth, slow turns will set you up better than lots of radical ones. At an altitude of about one hundred feet you are committed; just let the parachute fly straight ahead and limit any corrections to turns of ten degrees or less.

The last part of the approach is the flare. This procedure is simple: pull down both toggles simultaneously to slow down your parachute to a comfortable landing speed. To get the most out of flaring, you must be flying full speed on your final approach, so keep your toggles all the way up until it is time to flare. (An exception is if you have poor depth perception, when the lighting is bad, or when the surface is uncertain such as water or corn. Then you may be better off approaching in partial brakes to slow your approach, giving you a little more time to assess the situation.) The flare should be done when your feet are about two to three body heights above the ground. A smooth flare over about three to four seconds will work better than a fast, hard flare, but the main thing is to have both hands all the way down when your feet are three or four feet off the ground. If you realize you started the flare low, speed up; if you started high, slow down. Do not, however, let your toggles back up once you have started to flare. This will cause your canopy to dive forward and result in a hard landing. The illustration showing a canopy's flight during a flare will show the consequences of a badly timed flare. Too low, and you have a lot of forward speed even though your descent is slow. Too high, and you will have a lot of downward speed even though your forward speed is low. That is why you should flare a little high and slow on a calm day, a little low and fast on a windy one.

Let's quickly review the three most important points for a safe landing. First, always pick a safe place. Be sure of your landing site before you reach 1,000 feet! People who hit hazardous things such as cars, buildings, or power lines almost always do so because they did not choose a safe landing site high enough and were forced to land in a bad location when they realized, too late, that they could not make the target.

Second, never land in a turn. We know that a parachute's descent rate increases dramatically in a turn, and that speed remains for a few seconds after the turn is stopped. Landing in turns is by far the biggest cause of skydiving injuries. These low turns are usually made by people who did not pick a safe area and turned at the last moment to avoid an obstacle, or by people who thought landing on the target was a higher priority than landing safely. No low turns!

Third, land into the wind. This one is too obvious to need elaboration; the slower you are going, the softer you land. However, landing down wind or cross wind is less likely to cause injury than landing in a turn or on obstacles! On a breezy day, turn towards your parachute after you touch down and pull in one line to collapse the canopy. You may need to run around down wind of the canopy.

After the Freefall

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?

4) How often should you practice your emergency procedures?

Flying Your Body



The principles of freefall flight are quite simple; after all, you are dealing with just two things: your airfoil (body) and the wind. In a perfect, relaxed arch, or box man, you will fall straight down at a constant rate. To an observer falling along side, you appear stationary. You only seem to be falling relative to someone not in freefall, such as an observer in the airplane or on the ground.

The box man is the neutral freefall position from which all maneuvers are carried out. Relative to a stationary observer, by altering your body position you can turn in place, move up and down, backwards and forwards, or sideways. You can even turn upside down or fly standing up. In fact, no one really knows the limits of body flying yet!

From the box position you can easily initiate turns, forward, backward, and sideways movement, and changes in fall ra From the side, the body presents a continuous smooth curve to the wind. The head is up, the arms higher than the body, and the legs are bent at a 45-degree angle, leaving the lower leg slightly extended into the wind.

From above, the elbows are straight out from the shoulders and the hands are at least as far out as the elbows. The knees are slightly spread so that the feet are as wide apart as the elbows.

The basic moves are well understood. The most commonly used maneuvers are turns, forward and backward movement, and faster or slower falling. All are accomplished by changing the flow of air around your body. If you think of your box man as being balanced on his center in a neutral position, all he has to do to turn left is deflect more air off his right arm than his left. This is done by simply banking like an airplane - left arm down slightly, right arm up in proportion. The turn will continue until he resumes the neutral position. Lowering one knee relative to the other accomplishes the same thing. That's why an unintentional turn can often be stopped by assuming a neutral position and then giving a little "legs out" to increase awareness and balance the legs.

Turns are also based on deflection of air. In the neutral position, equal amounts of air spill off both sides of the body. To turn right, our box man banks his arms, just as an airplane does in a turn. More air flows off the left side, creating a right turn. Note that the position of the arms relative to each other does not change; both arms tilt as a unit. The rest of the body remains neutral. To stop the turn, simply return to neutral.

Forward motion works on the same principle of deflection. To deflect more air to the rear, resulting in forward motion, bring your arms back a few inches and extend your legs. This tips your body slightly head down, air rushes back off your torso and legs, and you slide forward. The two elements combine to create forward movement. Naturally the opposite motion - arms out and legs in - will make you backslide.

Now think about how to go up and down. Everyone knows that given the same power, a streamlined vehicle can go faster than one that isn't. It slips through the air easier, just as a canoe knifes through the water more easily than a barge. So to speed up, you simply arch more, letting air slip off easily. Flatten out, or lower your knees and elbows, and you will fall slower. Incidentally, the faster you fall the more stable you are because your center of gravity is further below your control surfaces (arms and legs.)

TEST YOURSELF

1) If you reverse your arch, what will happen? Is this position stable?

2) Think about forward and backward motion. What would you do to fly sideways?

Parts of Round Parachute

Cruciform (Square) parachutes



The unique design characteristics of cruciform parachutes reduces oscillations (swinging back and forth) during descent. This technology will be used by the US Army as it replaces its current T-10 parachutes under a program called ATPS (Advanced Tactical Parachute System). The ATPS canopy is a highly modified version of a cross/ cruciform platform and is square in appearance. The ATPS (T-11) system will reduce the rate of descent by 25 percent from 21 feet per second to an incredible rate of 18 feet per second. The T-11 is designed to have an average rate of decent 14% slower than the T-10D thus resulting in lower landing injury rates for jumpers. The decline in rate of descent will reduce the impact energy by almost 25% to lessen the potential for death.

Proper Gears


Proper gear protects lives of parachuters and they in fact put their lives in the hands of the gear, so to speak. Now you can see the importance of proper parachuting jumpsuits.

Jumpsuits tend to be made in two general styles. They can be made of special slippery fabrics and tailored tight around the body for faster speeds, or they can be designed in that typical MC Hammer baggy fashion with canvas-like material to help slow down fall speeds.

Other clothing that doubles as protective and practical gear includes a helmet and goggles. Helmets are mandatory clothing for beginner jumpers, but don’t be embarrassed if you happen to be one, most experts wear them too. You can even individualize yours, choosing from styles like old leather football helmets to hard, motorcycle-like helmets. Depending on your helmet, you may need to protect your eyes with goggles.

The pants, suits, and helmets are just one aspect of your required equipment. Other gear includes an automatic activation device (or AAD). which helps to safeguard you in case you drop too low in altitude without pulling your cord, the AAD does it automatically for you. Also, there is the reserve static line (or RSL). which is another safety device. The RSL is your lifeline and pull cord for your reserve parachute.

Saturday, May 26, 2007

Round Parachutes

An American paratrooper using an MC1-1C series 'round' parachute


Round parachutes, which are purely drag devices (that is, unlike the ram-air types, they provide no lift ), are used in military, emergency and cargo applications. These have large dome-shaped canopies made from a single layer of triangular cloth gores. Some skydivers call them "jellyfish 'chutes" because they look like dome-shaped jellyfish. Rounds are rarely used by skydivers these days.

The first round parachutes were simple, flat circulars, but suffered from instability, so most military round parachutes are some sort of conical (i.e. cone-shaped) or parabolic (picture a flat circular canopy with an extended skirt) US Army T-10 parachute used for static-line jumps.

Round parachutes are designed to be steerable or non-steerable. Steerable versions are not as maneuverable as ram-air parachutes. An example of a steerable round is provided in the picture of the paratrooper's canopy; it is not ripped or torn but has a "T-U cut". This kind of cut allows air to escape from the back of the canopy, providing the parachute with limited forward speed. This gives the jumpers the ability to steer the parachute and to face into the wind to slow down the horizontal speed for the landing. The variables impact the way and the speed that the parachute falls, because it depends on the speed or the amount of force in the wind that might change how a parachute falls.