Summary - The sequence of a main parachute deployment relies on a series of interrelated parts getting into the airstream in order. There are different systems available that vary slightly, including gear designed for student training.
Activation - Most experienced skydivers use a throw-out pilot chute system for deploying their main parachute. A small, round parachute, called a pilot chute, is packed in an external pouch. To initiate deployment, the skydiver extracts the pilot chute from the pouch and throws it into the surrounding air stream.
Deployment - The pilot chute is attached to the rest of the parachute by a length of fabric webbing or tape, called a bridle. Midway along the bridle is a pin holding the main parachute container closed. When the pilot chute inflates in the air stream, it pulls the pin, thus opening the main parachute container. The pilot chute and bridle then extract an internal deployment bag containing the main parachute.
The fabric portion of the parachute, or canopy, is folded or stuffed into the bag with the lines stowed outside in elastic bands. As the pilot chute and bridle pull the deployment bag out and away from the back pack, the lines release one stow at a time until fully stretched. With the release of the lines from the outside of the bag, the bag is now open, allowing the main parachute to inflate.
Inflation - Ram-air canopies are made of a series of inflatable tubes or "cells," connected side-by-side along their length. Each cell is designed to form the cross section of an airfoil, so when the parachute inflates, it forms a wing-shaped canopy, ready for flight.
The front of each cell is open to the air, and the back is sewn closed. Once inflated, the ram-air canopy is a semi-rigid, rectangular plane, similar to an airplane wing. It is attached to the jumper in a nose-down attitude to keep it inflated and flying forward.
The jumper steers and lands the canopy using two control lines attached along the rear of the wing near each end. When both toggles are depressed, the wing slows, causing the jumper to swing forward, momentarily pitching the flight angle of the wing upward, in the same way an airplane flares for landing.