In the early days, a trained skydiver (or jumper) and a group of associates meet at an isolated airport, sometimes referred to as a "drop zone." A fixed base operator at that airport usually operates one or more aircraft, and takes groups of skydivers up for a fee. It was common for an individual jumper to go up in a Cessna light aircraft such as C-172 or C-185. These days, it is common for busier DZ's near populated areas to use multiple, larger aircraft such as the Cessna Caravan C208 or DeHavilland Twin Otter DHC6.
A typical jump involves individuals jumping out of an aircraft (usually an airplane, but sometimes a helicopter or even the gondola of a balloon), travelling at approximately 4,000 meters (around 13,000 feet) altitude, and free-falling for a period of time before activating a parachute to slow the landing down to safe speeds.
Once the parachute is opened, (usually the parachute will be fully inflated by 2,500 ft). the jumper can control his or her direction and speed with "steering lines," with hand grips called "toggles" that are attached to the parachute, and so he or she can aim for the landing site and come to a relatively gentle stop in a safe landing environment. All modern sport parachutes are self-inflating "ram-air" wings that provide control of speed and direction similar to the related paragliders. Purists in either sport would note that paragliders have much greater lift and range, but that parachutes are designed to absorb the stresses of deployment at terminal velocity.
By manipulating the shape of the body—as a pilot manipulates the shape of his aircraft's wings—a skydiver can generate turns, forward motion, backwards motion, and even lift. Experienced skydivers will tell someone that in freefall, one can do anything a bird can do, except go back up.
Skydivers generally do not experience a "falling" sensation due to the fact that the resistance of the air to their body at speeds above about 50 MPH provides some feeling of weight and direction. At normal exit speeds for aircraft (approx 90 MPH) there is little feeling of falling just after exit, but jumping from a balloon or helicopter can create this sensation. They reach terminal velocity (around 120 mph (190 km/h) for belly to Earth orientations, 150-200 mph (240-320 km/h) for head down orientations) and are no longer accelerating towards the ground. At this point the sensation is as of a hard wind. When they leave the plane, their momentum from the plane causes their direction of travel to change from the direction of the airplane's flight (horizontal) to the direction pulled by the force of gravity (vertical). Skydivers call this transition period "the hill", and the amount of distance they fly with the plane due to the momentum is called "forward throw". For typical people, less than 1g of force along the body's long axis is what causes the "stomach in your throat" feeling on a roller-coaster or other amusement park rides. This is why skydivers in the armed forces are encouraged to eat a block of cheese about an hour before jumping to keep the acids from coming up in their mouths.[citation needed]
Most skydivers make their first jump with an experienced and trained instructor (this type of skydive may be in the form of a tandem skydive). During the tandem jump the jumpmaster is responsible for the stable exit, maintaining a proper stable freefall position, and activating and controlling the parachute. With training and experience, the fear of the first few jumps is supplanted by the tact of controlling fear so that one may come to experience the satisfaction of mastering aerial skills and performing increasingly complicated maneuvers in the sky with friends. Other training methods include static line, IAD (Instructor Assisted Deployment), and AFF (Accelerated Free fall) aka Progressive Free-Fall (PFF) in Canada.
At larger dropzones, mostly in the Sun Belt region of the United States, training in the sport is often conducted by full-time instructors and coaches at commercial establishments. Commercial centers often provide year-round availability, larger aircraft, and staff who are current in both their sport and their instructional skills.
In the other latitudes, where winter (or monsoons) gets in the way of year-round operation, commercial skydiving centers are less prevalent and much of the parachuting activity is carried on by clubs. These clubs tend to support smaller aircraft. Training may be offered (by instructors who are tested and certified in exactly the same way as their commercial counterparts) in occasional classes or as demand warrants. These clubs tend to be weekend only operations as the majority of the staff have full-time jobs during the week. Club members will often visit larger centers for holidays, events, and for some concentrated exposure to the latest techniques.
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