have satisfactory elasticity. A parachute made from fabric with good elasticity is stronger and gives less opening shock. Weight Lightweight fabric is an absolute necessity for all parachute canopies. A canopy of lightweight material opens faster. Can you imagine a pilot walking around wearing anything as heavy as a canvas beach umbrella? Lightweight cargo and deceleration parachutes enable the aircraft to carry more weight in cargo and fuel. Resistance to Abrasion This refers to a fabric’s ability to withstand wear and rubbing. In its lifetime, a parachute is subjected to a great deal of abrasion. When you pack a parachute, you pull the canopy down the table. A deceleration parachute slides along the runway. For this reason, deceleration parachute riser webbings and personnel parachute harnesses and risers are treated with Merlon (brand name) to make them more resistant to abrasion damage. Resistance to Mildew and Insects Moths and other insects love to feast on fabrics; mildew and other fungi thrive on them in warm, damp climates. Parachutes damaged by mildew or insects would be unsuitable for Navy use. Therefore, it is necessary that parachute fabric be as resistant as possible to this type of damage. Moisture Regain The term moisture regain refers to the percentage of moisture that a bone-dry fiber absorbs from the air under standard conditions of temperature and humidity (65 percent relative humidity and 70 “F). Less than 5 percent moisture regain means that the fibers build up static electric charges when rubbed. If static electricity builds up, the parachute assembly is more difficult to service. Static electricity also adversely affects the opening time of a parachute assembly. The ability to take on dye (color) is another important consideration when selecting parachute fabrics. The percentage of moisture regain possible in a fabric determines whether it can be successfully dyed. Dying gives the fabric color, which is important for a parachute canopy. Rescue teams can easily spot multicolored canopies from the air. Pickup crews can quickly identify colored deceleration canopies on runways. Also, yellow dye in a canopy makes it more resistant to ultraviolet damage from sunlight, which relates to the next engineering requirement on this list. Resistance to Sunlight Ultraviolet light, which is found in sunlight, reduces the strength of fabrics. Ultraviolet rays give you a painful sunburn when you’re out on the beach too long. All parachutes are exposed to some sunlight. Military specifications for parachute materials state fabrics should not lose more than 25 percent of their original strength after 50 hours exposure to sunlight. Investigations into causes of deceleration parachute failures have shown strength loss of more than 50 percent after 50 hours of exposure to sunlight. Resistance to Heat In addition to sunlight, heat and friction are natural enemies of a parachute. In case of fire on an aircraft, personnel and deceleration parachutes may be exposed to great amounts of heat. Friction and heat are generated when the deceleration parachute comes in contact with the runway. Line- overs cause friction and burn holes in parachute canopies. Line-overs happen when an improperly stowed suspension line is drawn over the canopy during deployment. Resistance to Chemicals Because parachute assemblies are exposed to various chemicals, it is important to know which chemicals are harmful and which are not. Most damaging are mineral-type acids, such as the type used in batteries. You have studied a long list of engineering requirements that are important to know when you service parachutes. You already know that nylon is the most widely used fabric in the parachute shop. In the following text, we examine the good and bad characteristics of nylon in parachute construction. There is no fabric known to man that measures up perfectly to all the engineering requirements for parachute construction. But nylon comes closer, by far, than any other fabric. Nylon, when properly handled by the parachute 10-8