Safety Check

Twists of Fate
Once considered to be only a slight nuisance, line twists are proving themselves as a much bigger problem, even leading to several fatalities. If we jumped only large, rectangular canopies at light wing loadings, line twists would seldom cause more than an inconvenience. However, jumpers flying elliptical or cross-braced canopies at moderate to high wing loadings must be prepared to treat line twists as a malfunction that requires fast action with emergency procedures.

Regardless of the canopy size or shape, line twists alone do not necessarily pose a problem. But twists that cause the canopy to spin can catch jumpers by surprise. The smaller and more elliptical the canopy, the more sensitive it is to uneven loading during a line twist and the more likely a fast rotation will develop. An increasing number of deaths are resulting from jumpers running out of altitude while dealing with line twists. Two major mistakes have led to the fatalities: keeping the main for too many revolutions and delaying reserve deployment after a cutaway. To better understand what can go wrong and to avoid the same mistakes as those before us, it helps to see exactly what occurs during a spinning line twist malfunction.

The following data came from a videotape of an actual jump. The videographer jumped a fully elliptical parachute with a 1.8:1 wing loading. He deployed the main at 3,200 feet. The canopy took 400 feet to inflate and opened with two line twists and closed end cells. The video clearly shows the risers were offset four inches from one side to the other due to one riser hanging up on deployment. This caused the main bag to rotate, twisting the risers and lines as the main canopy inflated. After initial deployment, the canopy immediately began a rapid spin due to uneven loading between the right and left sides of the canopy. At 2,800 feet, the jumper began rotating 360 degrees every two seconds, but the weight of his body wound the canopy lines into tighter twists with each rotation. The horizon blurred as the canopy accelerated in a spinning dive toward the ground, increasing the rotation speed to nearly one rotation per second.

In dealing with the malfunction, the jumper spent the first four seconds working to stop the rotation and unwind the line twists. The centrifugal force, spinning, and distorted harness made it difficult for him to locate the cutaway and reserve ripcord handles. Another four seconds passed before he found his cutaway handle and initiated emergency procedures.

He released from his main canopy with his back to earth and feet toward the horizon. The rotation stopped as his reserve static line deployed his reserve canopy. He was dizzy and disoriented, but under a fully inflated reserve just 100 feet or so below his main, and over a clear area.

At what altitude did his reserve open? At 850 feet, only about three revolutions before it would have been too late. This example illustrates how quickly a jumper can get to a dangerously low altitude after deploying his main at a normal altitude and experiencing simple line twists. As students, most of us learned we could kick out of line twists without much trouble. However, several recent fatalities prove that line twists can be much more than a slight inconvenience, especially at moderate and high wing loadings. Jumpers must be prepared to take fast action when line twists become more than just a nuisance. —Jim Crouch

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