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BASE Jumping: Articles: Suggested Topics: Jumping: Pilot Chute Dynamics

Pilot Chute Dynamics updated

by admin
Pilot Chute Dynamics The pilotchute is what extracts your canopy out of the container towards line-stretch. A moving pilotchute will transfer its movement to the canopy itís attached to, at least to a certain extent. This problem is often referred to as the Ďoscillating pilotchute. Imagine a stowed pilotchute tossed out to your side. It will inflate and extend and come from the side towards the center. It carries momentum, continues to the other side and then bounces back. Essentially you see a pilotchute bouncing back and forth above the jumper. This movement is transferred to the canopy contributing to an offheading opening. There are two major causes for pilotchute oscillations: 1. An assymetrical pilotchute, either because itís manufactured that way or because itís attached to the bridle that way. An assymmetrical pilotchute will spill more air on one side than on the other and start tipping over, until the other side spills more and tips to the other side, never quite finding an equilibrium. See the section on * Closing the pilotchutes for more information on how to detect and avoid this. * A pilotchute throw that is too strong to the side. Note that the force with which you throw your pilotchute is a delicate one. You want to make sure the pilotchute clears a potential burble and has a chance to inflate and do its work. At the same time, a throw that is too strong can contribute to offheadings. When in doubt, err on the side of throwing too hard. It is better to have an offheading canopy than no canopy at all. To combat pilotchute oscillations, manufacturers came up with vented pilotchutes that reduce oscillations. These vents let some amount of air spil through the top of the pilotchute, allowing the low pressure point above the pilotchute to be filled. Supposedly this results in pilotchutes that are more stable. Practice has shown vented pilotchutes to offer some advantage over non-vented pilotchutes, but the science of it is too fuzzy to come to strong conclusions. Some people prefer non-vented F-111 over vented ZP pilotchutes arguing that the F-111 is permeable over its entire surface, achieving what vents try to do more effectively.

Submitted by admin on 2007-06-14 | Last Modified by FredPot on 2009-06-18

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