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 contol lines attached
along the rear of the wing near each end. When both toggles are depressed,
the wing slows, causing the jumper to swing foward, momentarily pitching
the flight angle of the wing upward, in the same way an airplane flares
for landing.
(source: USPA.org)
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