Investigation of Impact Load Absorption through Suspension Line Elongation

摘要

The purpose of this investigation was the study of suspension lines under actual operating conditions, having varying degrees of elongation, energy absorption and elasticity. A secondary purpose of the investigation was the study of fabric porosity, shape and type of canopy, and method of parachute deployment. The shock absorbing capacity of five different types of parachute suspension line cord were first evaluated for basic physical properties, then were tested by assembling into parachutes and opening the parachute at various speeds - first at 100 mph, then 150 mph, finally 200 mph - on a whirling test tower. The parachutes were evaluated first in standard back type, then in deployment bag openings. Two types of parachutes were used: one being a twenty four foot standard parachute, the other being a 30 foot parachute, with an extended skirt. The loads were measured and the cords evaluated on the basis of shock absorbing capacity, strength, and durability. Final results of the work indicates that the presently used 550 lb tensile strength cord, Specification MIL-C-5040, Type III, is the best of the cords evaluated. A good correlation was established between line energy absorption and snatch force, but opening shock loads appear to be little affected by line characteristics. (Author)