E-Learning Media Center

EQUIPMENT SAFETY

By: Gabriel Jebb

All commercial and private aircraft are subject to routine maintenance inspections on a per-flight basis. So why should your paragliding equipment be any different? In Germany and Austria , it is compulsory to send all gliders to a certified testing center after 2 years or 200 hours, whichever comes first. Commercial tandem gliders and school wings may require more frequent testing if specified by the manufacturer.

A full inspection includes;

1. Measuring the line lengths.
2. Line strength tests including break strength of main load bearing lines.
3. Canopy porosity check
4. Canopy stretch and material strength test.

Proper glider inspections require some unique equipment and know how. Although inspections are not extremely complex they should never the less be handled by a professional with the right equipment. The following guide is meant to be a summary of the inspection process and a description of the materials inspected. Perhaps it will shed some light on the importance of proper glider maintenance and care.

Paragliding Lines

The suspension lines of a paraglider are extremely important in the overall handling and safety aspects of your wing. Assuming your glider does not have the unsheathed (racing/comp) lines, each line will consist of an inner core and an outer sheath. The elastic outer sheath is made out of nylon or polyester based materials that provide protection against U.V., abrasion, heat, dirt, etc. This sheath does provide protection for the core, but does not contribute much to the overall structural strength of the line.

Two different core materials are popular in the construction of modern paragliders lines. Kevlar usually referred to as Aramid by the manufacturers and Spectra referred to as Dyneema. Kevlar and Spectra are both accepted by the DHV for certification purposes because they are very strong and provide little stretch or elongation tendancies. These materials have the following characteristics:

Kevlar: (aka: aramid, edelrid, technora, or twaron – each of these are Kevlar composite fibers with additional coatings like Teflon.)

• Approximately 3x as strong as polyester or nylon fibers.
• Can withstand high temperatures before loosing strength.
• Heat resistant to about 750 degrees Fahrenheit.
• Low elongation tendency.
• Resistant to several chemicals.
• Can become “brittle.”
• Very susceptible to abrasion.
• Low tolerance to UV (sun damage).
• Looses considerable strength when wet around 10%.

Spectra: (aka: dyneema, high tenacity polyethelene, or Superaram)

•  Best strength to weight ratio of any fiber.

•  30-40% stronger than Kevlar, about 4x as strong as nylon.

•  About 10x-15x more resistant to abrasion than Kevlar.

•  Very resistant to chemicals.

•  Highly resistant to cuts and tears.

•  Best UV resistance.

•  Low stretch tendencies.

•  Does not absorb moisture, buoyant.

•  Begins to loose considerable strength at temps higher than 225 degrees Fahrenheit.

•  Difficult to sew.

•  Can stretch over time.

So which material do you have… if the sheath is missing on any part of your line, (sometimes noticeable at the ends) you might be able to see a bit of the core? If your core is yellow, beige, or gray in color it is probably Kevlar. Spectra lines are pure white even after U.V. exposure.

From the above specs, it looks that Spectra would be the obvious choice of line material for paragliders, yet manufacturers have different philosophies on line requirements. Some manufacturers even use both.

Line inspection involves a visual inspection of the line, to insure no fraying or chaffing of the sheath. It also checks the possibility of core separation (broken core, but no break in the sheath). A ripped sheath can compromise the overall tensile strength of the line and should therefore be replaced. It's not to say that one can't fly with a rip in the line sheath, but realize, when the sheath breaks, and the core is exposed (particularly in the case of Kevlar), the line strength diminishes substantially.

Line measurement is next on the list for line testing. This is usually done with the assistance of an electronic measuring device. The line is stretched under approximately 5kg of load and the meter measures the line to within a millimeter of actually length. Depending on manufacturer specifications the lines will have to fall within 5-8mm of original length. That doesn't seem like much 0.25-0.3in., but take into consideration how many lines you have on your wing. Now multiply that by a third of an inch and you'll see that serious canopy deformation is possible. This test also helps stretch any lines that might have shrunk prematurely.

The load test or breaking strength of the main lines is the final line test. A couple of lines are actually broken to measure the weight under which they break. This test is also done with the assistance of an electronic measuring unit. The line is stretched under mechanical load and the measuring device measures the amount of weight on the line when the line breaks. The lines tested are the highest load bearing lines usually the lower A's or B's closer to the center.

Line Maintenance

Maintaining your lines is easier than you may realize. Do a visual inspection of your lines before each flight. Running your hands along the brake cascade is especially important so that you get a closer look at the brake lines but also so that you can feel if the core has broken without the sheath breaking. Yes you can still control the glider if a brake line breaks during flight (through weight shift and rear riser steering), but it just becomes more difficult. When inspecting your lines also pay close attention to where the lines meet the risers at the quick links. The stainless steel triangle karabiners sometimes chip or corrode which will cause excessive abrasion. The Cousin Trestec website (manufacturer of paraglider lines), offers the following advice regarding paragliders and paragliding lines:

The paraglider lines must be protected from the sharp angles, stone falls and the tools which could cut its fibres. Avoid any contact with corrosive, aggressive or sharp substances (acids, oils, gasoline...) which can destroy fibres without that (damage) being visible.

If the paraglider lines are wet, always let them dry in the shade, away from the heat before storing them. Always store in a dry and shaded place, away from U.V. rays and heat. Do not leave your paraglider in the sun or under the car windows, the high temperature and the U.V are very harmful for your paraglider lines.

Paragliding Fabric Description

Rip-stop nylon is the most commonly used fiber in paragliding canopy construction. Nylon exhibits excellent strength, flexibility, tear resistance, abrasion resistance, and ease of drying. It does not offer zero or near zero porosity, nor does it stand up well to UV exposure. This job is usually handled by a special coating applied to the nylon or polyester. The two prevalent types of coating are silicon or polyurethane based which can be applied either by a lamination or impregnation process

These special fibers are only manufactured by a handful of companies thus most manufacturers use the same fabric sources. These companies include Porcher Marine, NCV. ( France ), Gelvenor Textiles ( South Africa ), Perseverance Mills, Ltd. ( England ), Teijin Ltd. (Japan), Toray Textiles, Inc. (Japan), and Carrington Performance Fabrics, Ltd. (England) .

Here is a quick breakdown as to the characteristics and usage of each material.

Porcher Marine (Popular fabrics: Porcher 9017 – Skytex 36, 40 and Porcher 9092 – Skytex45)

Paragliding cloth is made by their sports fabric division which has been making fabrics for spinnaker sales, parachutes, paragliders, hang gliders, etc. for over 25 years. The paragliding cloth is produced in several different weights with three different coatings. The most recent development is Porcher 9092 fabric, which offers a balance between, lightness, strength, tightness, stability, and durability. Porcher is used by approximately 65% of the paragliding manufacturers.

Gelvenor Textiles ( Popular fabrics: LCN066 OKS, LCN066 K54, and LCN517 K54)

The Aeronautical division of Gelvenor produces the paragliding cloth and has been building fabrics for parachutes, sails, paragliders, kite surfers, etc. for over 30 years. They offer several different weights and coatings. Most of the cloth used in paragliding is known for its extremely durable polymer coating. This cloth is firmer than others on the market, which provides excellent durability. Added protection against UV is furthered by a UV inhibitor in the coating.

Perseverance Mills (Popular fabrics: Pertex Blue – PN1, PN4, & PN5)

Perseverance has been manufacturing fabrics for parachutes since the 1950's. The company has been a major manufacturer for pg materials in the past and recently became re-involved with paragliding mainly through an exclusive contract with Swing. The new materials from Perseverance offer great UV durability without the added weight.

Teijin (Popular fabrics: Polyester)

Teijin polyester was a very popular material until a few years ago when the company moved into other vertical markets that did not include paragliding. This is unfortunate because Polyester offered great resilience to moisture, UV deterioration, and durability.

Toray (Popular fabrics: Toray Nylon)

Toray is the largest textile manufacturer in Asia . Historically they have been one of the premiere suppliers of paragliding materials. They offer many different grades of nylon with unique features such as lightness and water repellent materials. They are currently restructuring operations in Asia and Europe and may soon become a major supplier of pg material again.

Carrington – No longer actively develops new fabrics, yet they still sell their existing products. Most of the manufacturers have therefore moved on to other suppliers.

So what's all this mean… well it means that there are several different fabrics on the market that offer a lot of different advantages / disadvantages? It is important to realize that while a fabric may have a unique advantage in one area this does not come without a trade-off. Improving one characteristic only comes at the expense of another. There is always the need to reach a compromise. For example, a heavier cloth will have better aging characteristics at the expense of extra weight. The additional weight might cause a glider to have a slower and more dynamic recovery from deflations. Lighter weight materials may offer nicer re-inflation characteristics, but could cause more difficulties launching a glider, or degrade faster in UV. Most manufacturers select a number of these materials when constructing their wings to obtain the optimal balance between durability and performance. It is not unlikely to have at least two different fabrics used in wing construction and sometimes three, four, maybe even five different fabrics are used.

Ultimately we all want our paragliders to stay air tight, have beautiful colors and last a long time. So what can we do to insure this? Take care of our gear. Here are a couple of tips on how to keep your wing in top shape. The most obvious culprit that causes deterioration is UV exposure from sunlight. Therefore excessive exposure in the air or on the ground will age the fabric. UV exposure is a primary suspect of glider deterioration. But, dirt, sand, debris, and other abrasive materials will wear the fabrics protective coating even faster. Moisture laden air and water will also cause deterioration, if the glider is packed up while wet. Here at Torrey another unique problem presents itself in the salinity of the air which has a very corrosive affect on everything from paragliders to automobiles.

Porosity Test

A porosity meter is the tool used to measure airflow through the fabric. This unique piece of equipment measures how long it takes a given volume of air to pass through the canopy material. The fabric ages and deteriorates so the amount of time for the volume of air to pass through the canopy material becomes shorter. As your glider deteriorates it will begin to act less like a wing and more like a parachute. At some point it will become dangerous to fly. The inspection done on your wing will include porosity tests on your canopy which can show you how fast air passes through the wing when it's new versus its current condition. This can give you a fairly accurate view of what the remaining lifespan of your wing will be.

Material Strength Test

This test consists of measuring the strength of nylon. It must withstand a specific mount of tension in order to be certified as airworthy. Of particular importance is the area around the seams which is especially vulnerable to damage and decay. Seam stretch is may also be monitored by pilots during their safety inspection. Occasionally we receive a wing so worn out that it may be pulled apart by hand. Needless to say this is probably not a safe wing to be flying and could suffer structural failure as a result of high g-force maneuvers or turbulence.

Reserve Parachute Repacking

Most manufacturers recommend that your reserve parachute be inspected and repacked annually. But this should be primarily a function of how often you fly and the conditions you fly in. Pilots that spend a lot of time in the air may want to consider semi-annual repacks. Certain climates can also be reason to repack your reserve more frequently; like hot humid environments or areas where your reserve is exposed to excessive moisture. Moisture can remain in your reserve container long after the flight has finished. This moisture causes your reserve to become sticky and may even prompt mildew.

Make sure you have your reserve repacked by an experienced individual or an instructor. It's also not a bad idea to participate in the repacking of your reserve so that you can learn all the details. The reserve should be inspected thoroughly once removed from the container to ensure that the lines and fabric are undamaged. It should be aired out to let any moisture dry out and static be discharged. Check that none of the stitching has unraveled on the canopy as well as the reserve bridle and suspension lines.

Karabiners

Aluminum karabiners should be routinely inspected for nicks, scratches, dents, corrosion, and other signs of wear. A prudent suggestion might be to replace the karabiners every couple of years just in case. Aluminum paragliding karabiners load tested to approximately 4032lbs. Consider upgrading to an all stainless steel carabiner with a greater loading capacity of nearly 5600lbs. These are not only stronger but they have to be replaced less frequently. Irregardless of your karabiner type to make sure to keep them clean. Dirt and debris trapped inside the karabiner can cause problems with spring loaded locking mechanisms.

Harness Inspection

Your harness should be inspected for wear and tear just like your glider. While harnesses are not usually replaced as frequently as gliders… prolonged use will show itself on the webbing, stitching, and even obscure areas like the accelerator pulleys. The interior of the harness should be inspected for cracked seat boards, frayed stitching, and damage or dirtied buckles. Dirt inside of the buckle can cause binding and problems with the buckles spring loaded click lock or release functions.

The main objective of periodic inspections is to insure your flight safety. Inspections are not mandatory but rather voluntary, and therefore depend largely on pilot participation. Unless you can afford to completely replace your flying equipment every year, a regular inspection and maintenance schedule is not only prudent, but a necessary step in your flying routine. A couple of minutes spent each day just looking over your equipment will reduce the possibilities of equipment malfunction in flight and bring you extra piece of mind.

Sources:
• Dupont - http://www.dupont.com/kevlar/index.html
• Teijin Ltd. - http://www.teijin.co.jp/japanese/flash.html
• Toray Industries, Inc. - http://www.toray.com/
• Perseverance Mills, Ltd. - http://www.pertex.com/
• Gelvenor Textiles - http://www.geltex.co.za/
• Porcher Industries / NCV - http://www.ncv.fr/
• Cousin Trestec - http://www.cousin-trestec.com/us/default.htm
• Edelrid - http://www.edelrid.de/
• Betech - http://www.liros.com/
• Critter Mountain Wear – http://www.crittermountainwear.com/
• Kitebuilder.com – http://www.kitebuilder.com/