by Jan Meyer
Recently, a tandem master experienced a broken drogue bridle line malfunction during the deployment of the main parachute in a Vector tandem rig. Normal drogue deployment occurred after exit. After freefall maneuvers, the tandem master pulled the drogue release handle. The tubular nylon inner bridle line of the drogue broke as it became loaded. The drogue and outer Kevlar sheathing separated from the jumpers. The bag remained in the pack tray, although it was turned upright. The reserve was activated. The main and reserve parachutes opened simultaneously. The main was cutaway and cleanly separated from the jumpers and the reserve parachute. A normal landing occurred under the reserve parachute.
A post jump inspection revealed that the free bag was burned in several places by the tubular nylon cord that was attached to the main parachute. Video documentation confirmed that the tubular nylon flapped about in the recirculation zone(burble). The tubular nylon cord broke in the 2 to 3 foot area of noticeable friction wear, about 6 to 9 feet from the bag stop.
Relative Workshop is sending out notices about this incident. Further action is being developed about the inspection procedures, frequency of inspection and mandatory replacement after a specified number of jumps. The tubular nylon will be upgraded from a breaking strength of 1500 lb to at least 2300 lb. All owners and users of Relative Workshop's Vector tandem rig should inspect the entire length of the tubular nylon inner bridle line. Regular inspection of the entire nylon bridle line is inhibited because it is partially hidden inside the Kevlar sheath. Friction burns should be noticeable along a 2 to 3 foot section located 6 to 9 feet from the bag stop. The friction burns degrade the strength of the tubular nylon by 25 to 50 percent.
This malfunction is extremely dangerous! There is a high probability that the tubular nylon cord that remains attached to the main and flaps wildly in the recirculation zone can wrap around the reserve bag and completely prevent reserve deployment. This would prevent the main from deploying too. Simultaneous deployment and inflation of both main and reserve parachutes pose a high entanglement probability.
FFI: Contact Relative Workshop at (904) 736-7589.
Originally published in Sport Parachutist's Safety Journal
V2, #3 Jan/Feb. 1990.
Dedicated to enhancing sport parachuting safety by disseminating information about equipment, environments and human factors.