There is a considerable amount of chatter about “valved” parachutes going around these days. Many skydivers believe that airlocked parachutes are the way of the future, while others see the introduction of this new technology as a temporary fad. In this article I will discuss the pros and cons, as objectively as I can, to this new development in parachute design.
    Simply put, an “Airlock” is a system designed to contain the internal pressure of a ram-air canopy, and therefore its airfoil shape. In short, the air goes in, but it doesn’t go out. If the wing’s shape is not reliant upon the relative wind (created by airspeed), then the performance range is consequently expanded and enhanced in every respect. In addition, the theory holds, such a self-contained airfoil will not distort or be otherwise adversely effected by turbulent flying conditions.
    Parachute designers have worked towards the goal of a valved parachute since the very birth of the ram-air canopy. Domina Jalbert, the man to whom credit is given for developing the world’s first ram-air canopy, was among the first to design such a system. Although his “valve” didn’t exactly revolutionize the industry, the spirit of Jalbert’s concept of a self-contained airfoil continued to possess (and obsess) the minds of inventors worldwide. Some twenty years later, I too got enthralled with this quest.
    I got involved with the airlock project as the result of a near-fatal collapse of my para glider in 1993. From my wheelchair, I began designing various systems to keep the air in the wing, with mixed success. I built scores of miniature parachutes, experimenting with every type of valve I could imagine. I discovered that regardless of the type of valve, I had to retain the leading edge “scoop” of the airfoil in order to maintain adequate internal pressure. I realized that there are many ways to achieve this end, but found only one method that stood head-and-shoulders above the rest. So I brought my idea to the only person I could think of that might be crazy enough to actually build it: Tony Uragallo. He hired me on the spot.
    Tony and I did extensive research on the valve concept over the course of three years. Some of our designs were incredible, while others weren't worth the fabric we built them out of. It was an age of synthesis, a time of wild creative genius and misdirected insanity. We eventually developed a product that we were proud of, and marketed it as “The Jedei”. As expected, the market received it with mixed emotions. Now that there are literally hundreds of these canopies flying all over the world, the pros and cons of valved parachutes have become much more readily observable. The safety and performance advantages of the design seem to be very well received. Pilots of valve parachutes have observed significantly longer landing surfs, even without dangerous acceleration maneuvers. This is due to the lack of “wing shrinkage” as the airspeed decreases. Furthermore, owners report that the wing feels far more stable in turbulence, exhibiting little or no span wise compression, even in the nastiest of conditions. The most exciting news is what has not been reported: there have been no documented canopy collapses due to turbulence whatsoever...Not One.
    Clearly the primary objective has been achieved. Consequently, a valved-parachute “cult” has formed; a sector of the skydiving population that refuses to jump anything that isn't valved. Supporters of the movement shun the use of “open-celled” parachutes in much the same way as early Zero-P jumpers avoided F-111 canopies. Although the supporters are adamant, they all have reported similar shortcomings to the airlocks.
    The disadvantages to the design seem to be born of the same attribute that attracts airlock customers in the first place... the air doesn't come out of the wing, whether you like it or not. For instance, after landing on an excessively windy day, you may be in for a bit of a fight if you haven’t developed a technique for “downing” the parachute. No one has reported any injuries as a result of being dragged after landing, and the hassle is something the owners seem to be willing to trade for the performance gains. The bottom line is: "would you rather have a bit of struggle with getting the air out on the ground, or a whole lot of struggle getting it back in during flight?"
    The drop zone packers usually have a bone to pick with the airlock concept as well. As the air tends to stay inside the wing longer, the airlocks sometimes require an extra step in the packing process. Most packers have adapted a technique of laying the parachute in a side-pack configuration, and then rolling their bodies across the canopy from tail to nose. Once most of the air is out, the parachute packs up the same as any Zero-P canopy. Although the packers’ gripe is valid, one must keep in mind that if it were solely up to the packers, we’d all be jumping F-111 parachutes.
    Lastly, there is the issue of cutaways. It is true that a few people have lost their valved canopies after cutaways. An undeniable side-effect to the airlocks is that the parachute can sometimes drift further after a cutaway than an “open-cell” canopy. This is usually not the case, but the possibility does exist. Interestingly, all of the despondent owners have replaced their lost parachutes with new valved canopies, an unarguable sanction of the technology.
    The final question still remains: “Is it all worth it?”... Is the theoretical safety margin afforded by parachute valve systems worth the new problems that they create? The fate of the airlock parachute remains in the hands of the skydiving community... the future is still to be decided. The airlock may be just another passing facet of the “Techno Fad”, or a permanent feature of the sport that will develop into the industry standard. As always, the direction and nature of the accepted technology is determined solely by the consumer, not the inventor.
    Brian S. Germain
    April 8, 1997
    Also known as a competitive freeflyer and lecturer, Brian Germain is the CEO of BiG Air Sportz, a new Colorado-Based parachute manufacturer. An avid skydiver with over 5000 jumps, Brian is the sole Patent holder on the “AirLock”, (U.S. Patent 5,573,207).
    The airlock technology is currently available through BiG AiR on a limited basis, and will shortly be available from Performance Designs, Inc., and Precision Aerodynamics, Inc once PD's exclusive license expires. Although the airlock technology available from BiG AiR is arguably significantly different from that licensed to Performance Designs, Precision has decided to wait until the expiration of PD's license (July 31) to release BiG AiR's line of canopies in the U.S.
    Subject: Airlock Article by Brian
    Date: 11/08/1999
    Author: Zenfreefall

    By admin, in Gear,

    Spot Cleaning of Nylon Parachute Fabric

    The following is presented as a public service. It is copied directly out of a handbook from Performance Textiles, Inc. which I obtained at the 1999 PIA Symposium in San Diego.
    This information is intended as helpful suggestions. Performance Textiles makes no guarantees of results and assumes no obligation or liability whatsoever in connection with this information. For that matter, neither do I, but with all of the questions asked about cleaning parachutes, I wanted to get the best information available out to the public.
    Most stains can be avoided by immediately wiping the stained area with an absorbent cloth or paper towel. Always handle the fabric carefully and treat the smallest area possible. The following cleaning procedures have been used successfully to remove stains from coated and non-coated parachute fabrics:
    Stain Type: Food, soda, catsup (kethup for most of us), mud, dirt, sweat.
    Procedure: Use clean water and a sponge gently. Rinse area thoroughly with clean water. NEVER USE FULL STRENGTH DETERGENT.
    Stain Type: Mustard, red clay, blood.
    Procedure: Use a MILD detergetn. Let it sit on the stain 3-5 minutes, then sponge gently and then firmer if needed. DON'T use bleach as it can (my comment as a chemist...WILL) affect the fabric strength, finish, and color. (My comment....Can you say turn it into tissue paper quality?!!!)
    Stain Type: Motor oil, hydraulic fluid, grease, exhaust and demo smoke.
    Procedure: Allow to sit on stained area for 1 minute and work into the stain with a sponge. Then gently and carefully clean and rinse as above. Be aware that staining chemicals and cleaning agents can affect fabric strength, finish, and color. (In this paragraph, they left out the comment about what to use. Presume they mean mild detergent again.)
    DO NOT USE FLAMMABLE SOLVENTS SUCH AS GASOLINE, ACETONE, MINERAL SPIRITS, PAINT THINNER, ETC., as they may damage the fabric or fabric coating and other components.
    WARNING: If the fabric shows any sign of (excessive) wear, fraying, or a cut, scratch, or tear, do not use the parachute. (My comments: I added the word excessive. Gee whiz...if we followed this protocol, we'd have very few jumps on our parachutes because they all have some minor stuff as they age. That's one reason why a rigger should check the systems out routinely!)

    Never use bleach or products containing bleach. Contact the original parachute manufacturer for any problems associated with the parachute.
    One final sentence from the pamphlet: Cleaning may be more harmful than the spot!
    Stay safe out there.
    Blue Skies & Safe Dives from Mike Turoff,
    Co-author (with Dan Poynter) of Parachuting, The Skydivers Handbook, 7th ed.
    Instructor and Tandem Examiner, Jump Pilot
    Subject: Spot Cleaning of Nylon Parachute Fabric
    Date: 1999/10/30

    By admin, in Gear,

    How To Select The Right Canopy For You

    In this article we will explore some of the questions you might ask when you go shopping for a parachute. While this advice is intended primarily for the novice jumper--just off instruction to one hundred jumps or so -- instructors may also wish to take note. As instructors we are often asked by our students, for advice on what kind of equipment to purchase. I always try to advise as if I were counseling a family member. “If you were my little brother or my little sister I would recommend the following.” Especially when I am in a student/instructor situation, I feel responsible for this fledgling until he is well on his way.
    Picking the right parachute is more complex than you might imagine. With well over 200 main canopies to choose from, this decision can be harder than buying a house. Today, there is a huge spectrum of canopies, from extremely high-performance parachutes to downright sluggish ones. There are some excellent selections for the novice and intermediate jumper in the mid to lower performance range. Let’s begin by defining some key terms for the uninitiated.
    High Aspect Ratio: The span (width) of the canopy is more than twice the chord length (straight line measurement from front to back) or greater than 2:1 aspect ratio.

    Low Aspect Ratio: The span of the canopy is less than twice the chord length or less than 2:1 aspect ratio.
    Elliptical High Aspect: As its name suggests, the elliptical canopy has tapered wing tips that significantly reduce wing tip vortices, thus reducing induced drag. When heavily loaded, this type of parachute goes very fast. The landing and stall characteristics are not as forgiving as a straight wing. It is only for the highly experienced skydiver with appropriate accuracy skills.
    Dynamic Flare vs. Steady State Flare
    There are two ways to land a parachute. More commonly in the past, the two methods were referred to as the “steady state flare” and the “dynamic flare”. The dynamic flare is one in which the brakes are applied, close to the ground or at the last moment at a toggle application rate of 1 foot per second. This is not a rapid movement -- it is really quite slow if you think about it. This maneuver converts downward and forward speed to vertical lift and diminishing horizontal glide. It should eventually result in a “tippy toe” landing. This maneuver, under a small canopy (meaning more than one pound per square foot of loading), almost anyone can do -- when the winds are up. In zero wind conditions the same maneuver requires years of experience, hundreds, perhaps thousands of jumps and a fabulous understanding of a particular canopy’s flight characteristics.
    The steady state flare is what is commonly used by practitioners of precision accuracy. You do not have to be a highly experienced accuracy jumper to use it, as it is a very forgiving technique. You must have a canopy of adequate square footage, however, and it generally works better on the thicker airfoils (accuracy canopies, demo canopies, some student canopies). In a steady-state flare the application of brakes is done more gradually, can be initiated at a higher altitude, and generates a minimum of lift. This is in opposition to the dynamic flare which generates a great deal of lift. The goal is the same with either technique. The last six inches above the ground should look the same: forward speed is virtually eliminated, and the parachute is brought straight down.
    The Pros And Cons Of Zero-P
    Zero Porosity fabric is impregnated with a silicone-based product that makes the fabric more resistant to wear and aging. This coating is what makes the fabric feel so slippery.
    The “Pros”
    The “Pros” of Zero-Porosity fabric include a better resale value, because the canopy will retain its original flight characteristics longer. But resale value, I try to stress to all canopy shoppers should be the last parameter. Buy what is right for you now. Choose the colors that you like. Go for the size and model that best suits your present needs. Zero porosity does not improve canopy performance as such. It only improves the longevity of the canopy. That is a big plus. However...
    The “Cons”
    It is harder to pack. You can sugar coat it a lot of ways but the fact is, the slippery, slimy feeling fabric is more difficult to keep under control, especially for the novice just learning to pack. Zero-P packs “bigger” because you can’t get as much air squeezed out of the pack job as you can with F-111. You will take longer to pack. At this stage of the game you want to keep up with the loads -- make more jumps in a day and not be fatigued. Your energy is better spent learning to skydive, rather than wrestling with your pack job.
    Canopies made from F-111 cost less. Considerably less. You can get many happy years of use out of your F-111 canopy, provided there is enough square footage over your head to start. Accuracy parachutes are made of F-111 because it allows the parachute to “bleed air” and sink better. This is something to bear in mind if you plan on doing a lot of demo jumps into tight areas!
    Line Drag vs. Pack Volume
    When should I choose Dacron? When should I choose Micro or Spectra line? Dacron lines provide greater parasitic drag, helping the canopy to shut down easier. Note that I speak in a positive light about this parasitic drag. In many cases it can be a good thing. Students would likely benefit from Dacron lines, as they often have trouble slowing down enough or at the right moment. Micro line or Spectra line reduces pack volume -- as a container manufacturer I love that aspect. I will grudgingly accept Dacron on my accuracy canopy to help control forward speed, however, and would recommend it to some young jumpers (under 200 jumps), for the same reason.
    Micro lines do not cause hard openings. Loose, short line bites, oversized rubber bands or Tube Stows, or otherwise improperly stowed lines cause hard openings. Consistently soft openings are commonplace on many micro-lined canopies. Likewise, hard openings are easily achievable with big, fat Dacron lines, if improperly stowed.
    Thick Dacron lines do not necessarily mean stronger lines. Jump Shack uses 1500 lb. Spectra on its’ Tandem canopies. There is nothing with greater tensile strength in use, in the parachute industry today.
    I almost always recommend Micro or Spectra on reserves. It is stronger. It reduces bulk in an area where space is at a premium. You may want to fit an AAD in the reserve container later on. Because your reserve is most likely a relatively low aspect 7 cell, excessive forward speed is not a problem. The reduced line drag will enhance the performance of your otherwise low-performance canopy.
    Winds And Field Elevation Change Everything
    Ask yourself this question: “Is it predominantly windy where I jump? Is it rarely windy where I jump?” If you are lucky enough to jump in Hawaii where it is absolutely beautiful, but windy most of the time, you can get away with a smaller canopy. You may in fact need a higher aspect canopy to survive if you are a lightweight. You don’t want to risk blowing off the DZ, after all. If it is only sometimes windy at your Drop Zone, and mostly calm, anticipate having to judge the distance of your glide on those low wind landings.
    Also consider Drop Zone elevation, and density altitude in the Summertime. Your parachute is going to display decreased performance capability at airports above 2000 feet, and on high temperature, high humidity days (the air actually gets thinner). You will have more difficulty stopping your canopy. The higher the elevation of your drop zone, the more square footage you should have. Otherwise anticipate a longer distance to bleed off forward speed. Above 2000 feet is where this factor becomes very evident, but I can feel the difference when I go away from DeLand, elevation 80 feet, and jump in New England at about 500 feet.
    Surprised is the student who makes his first 8 jumps in a 7 - 10 mph breeze, on a 288 sq. foot canopy, then suddenly finds himself off instruction, with no radio, on a windless day, with a 190 sq. foot demo canopy. Don’t let it happen to you -- unless you have endless desert stretched before you, free of barbed wire fences. This brings us to another important point -- drop zone location. In conservative New England (God love it), where the drop zones are small and the obstacles many, novices are generally guided toward canopies that are adequately large and docile. Whether it is done consciously or not, I have witnessed that the square foot per pound ratio (important! not the pound per square foot ratio) amongst young jumpers in that region is about 1.5, which I think is perfect. If you jump in a congested area, or one with many obstacles on or near the Drop Zone, you are generally better off with a relatively low-performance canopy. Don’t buy the argument about not being able to “get back” to the Drop Zone on a long spot day. Keep in mind that even todays “low performance” canopies could fly circles around the parachutes that we used 15 or 20 years ago, and we used those parachutes for demos, for accuracy, for students...
    Take The Conservative Approach
    Fifteen to twenty years ago, instructors were jumping parachutes that were not significantly different from those of the student. Giving advice was easy. You could go round or you could go square. If you were a big fella, you jumped a T-10. If you were a lightweight you could have a 28 ft. flat circular. If you had some money to spend you could get a ParaCommander. If you really wanted to go out on a limb you could have a Cloud or Paraplane (the latter not all that low in performance)! The point is, most of the canopies were relatively low in performance, or sufficiently high in square footage (or area).
    If I am speaking on the phone to a potential buyer, I always inquire about his age, physical condition, weight, and experience. I also ask where he jumps to get an indication of field elevation and prevailing conditions.
    Because many of us have fantasies of being a Sky god or a World Champion of some sort, we have a propensity to project this onto our students, giving advice with this in mind for one and all. We forget how many years it took to achieve our present status. We forget that many are in this sport just for fun! We should remind ourselves and our students, that there is plenty of time to learn, and there should be no rush. The instructional community seems to have no problem with telling the new jumper to sit down on a windy day so that he can jump tomorrow, rather than risk a bad landing that will put him out for three months. Likewise we should be telling them to take the conservative approach to canopy selection. We must assume that the novice jumper is going to make a mistake at some point, so why not let him do it on a big, forgiving canopy?
    Before you shop, talk to a few people, including your instructor, and some of the older, more experienced skydivers on your Drop Zone. Be careful not to let a salesperson dictate what you should buy. Because, while most retailers out there are reputable and knowledgeable -- they have a tendency to want to sell you what is in stock.
    A Formula To Go By
    Most manufacturers of parachutes speak in terms of pounds per square foot. For example, if John weighs 200 pounds and jumps a 97 sq. ft. canopy, he is loading it at 2.06:1 or 2.06 pounds per square foot of canopy.
    When you go shopping for a canopy, you should think in terms of square feet per pound of your body weight (i.e. you weigh 200 pounds and you have 0 - 20 jumps). Using the following chart, multiply your 200 pounds by the 1.75 sq. ft./pound recommendation for your number of jumps, and find that you should be jumping a 350 sq. ft. canopy.
    The following numbers are general guidelines from a conservative point of view. They are based largely on my own personal experience as an instructor, and active competitor, with 20 years of experience, flying canopies in every size range. For tandem jumping, I prefer the 400 square foot range. For accuracy, I jump a 252 to 259 square foot canopy, and for style, RW and everything else, I use a 107 square foot elliptical. So you see also, that different jobs require different canopies! Also remember -- there is an exception to almost every rule. For example, not all 7 cells are low aspect. The new Triathlon is a recent exception to that old rule. Not all reserves are 7 cells. There are 9 cell reserves, even 11 cell reserves. There is such a thing as thick Spectra line, and rather thin Dacron suspension line. There are a lot more exceptions where those came from.
    Number Of Jumps Appropriate Square Footage Aspect Ratio : 1
    1 - 20 1.75 sq. ft. / lb. <2.0 : 1
    21 - 50 1.65 sq. ft. / lb. <2.0 : 1
    51 - 200 1.50 - 1.35 sq. ft. / lb. 2.0 to 2.5 : 1
    201 - 1000 1.30 - 1.10 sq. ft. / lb. 2.0 to 2.8 : 1
    1001 - ? 1.10 - 1.00 sq. ft. / lb. >2.8 : 1
    Some interpolation will be required here. Round the figure up or down as much as 15% to find an existing canopy size.
    We know that highly experienced jumpers can and do exceed the one pound per square foot maximum as prescribed by most canopy manufacturers. This is one of the benefits as well as one of the hazards of living in a free society. We just have to be sensible about such freedoms.
    A jumpers’ age and physical condition must also be weighed into the equation. Ask yourself honestly,
    Am I athletic and limber? Can I run off excessive forward speed from a small, high aspect ratio canopy on a high-density altitude, no wind day? Am I simply in good physical condition? (Perhaps you can’t run as well or as fast as you used to.) Am I in fair physical condition? (I don’t want to have to run at all.) Or am I in poor physical condition (Lacking in strength and muscle tone, not very flexible)? If you are a “1," eventually when you have gained experience, you will be able to jump the sportiest of canopies. If you are a “2,” you may want a high aspect canopy, but with square footage in the 1.35 to 1.15 range. If you are a “3” or a “4,” consider a low aspect canopy, as well as abundant square footage.
    The Step-Down Method
    Spend your first two years or first 500 jumps on a canopy that is 1.5 square feet per pound in relation to your body weight. You should be completely comfortable in any situation or meteorological condition with that canopy before you graduate to the next size down. Then spend a year-- or 300 jumps-- whichever comes first, on the next size down the canopy, and so on.
    Riding The Clutch
    Fly with a little bit of brakes. It is OK to fly leaning on the toggles a bit. We do not have to be in full flight all the time until landing -- especially when there is a lot of other canopy traffic in the air. I routinely fly my Stiletto 107 in 1/4 brakes when on a large RW load or when picking my departure point to land in the pea gravel area. In a congested situation, one has to get in the landing queue (ahead of the big floater, behind the hot little 99 square foot canopy). The main reason for flying with a little bit of brake applied is to provide for more forward speed in the event you misjudge and find yourself short of your targeted landing area. You now have a little “extra gas”. Additionally, if you’re “steep” (high and close to your target), it is OK to apply some brake and sink till you reach the desired angle of attack.
    Timing the flare is infinitely critical. Learning this skill simply takes a number of jumps to perfect. I think it is probably harder to master than the basic freefall skills. Some jumpers have a natural “feel” for this. Others may take hundreds of jumps to learn it! Most skydiving schools do not spend enough time on canopy control. More emphasis should be placed on canopy control in the post-instructional period. Teaching drop zones might consider a five or ten-jump “stand-up accuracy” course before graduating that student. Abundant square footage will provide for a greater margin of error until you develop the necessary canopy control skills. There are canopies out there for you.
    If you have under 200 jumps you should allow yourself ample square footage, seriously consider low aspect, and resign yourself to a medium or large sized container. There is plenty of time to work your way down in size of canopy. No one ever screwed themselves into the ground because they were jumping a canopy that was too large.
    Nancy J. LaRiviere
    USPA/ I, Tandem Examiner
    Pilot, COM, MEL
    Senior Rigger
    May, 1995
    © The Jump Shack
    Reprinted with permission

    By admin, in Gear,

    Top Ten Misconceptions About Zero-P Canopies

    A while back, I overheard a bunch of people discussing their lative merits of different types of canopies and materials for low-time jumpers. I heard some interesting misconceptions about what's dangerous and what's not, what works and what doesn't. In the interest of getting some discussion going, I figured I'd-list my top ten misconceptions about Zp canopies:
    1. Zero-p canopies are dangerous.
    Zp canopies have gotten a bad reputation over the years, since most hp canopies are made of Zp fabric. However, this does not mean that hp fabric itself is dangerous - it just allows smaller canopies to land well, and so is often used for smaller, high performance canopies. A large 9 cell Zp canopy is just as safe a sits same-size F111 counterpart.
    In fact, it is often safer. Zp fabric keeps air from escaping though the top and bottom skins of the canopy, and thus allows better canopy pressurization at a given airspeed. This helps prevent canopy collapse in bumpy winds. In addition, the Zp fabric allows the airfoil to be a bit more efficient, and thus allows you to slow down a little more before landing. During a landing in a bad area (a power station, for example) that slower speed can be a life saver.
    2. Zero-p canopies are harder to land than F111 canopies.
    Not at all. In fact, the opposite is often true. Zp canopies have more lift during the flare, and that extra lift can be used to slow yourself to walking speed before touching down. F111 canopies, especially old ones, often can't do that any more -they become so porous that they stall before slowing you down enough. Often, you will see people with older F111 canopies doing all sorts of tricks to get good landings - front rise ring, taking wraps on the brake lines, and turning low. Generally, such maneuvers are not required with Zp canopies.
    This year I watched maybe 200 landings at bridge day. Conditions were not great - zero wind and an uphill landing. The people who got the best landings were the people with fairly new(i.e. not porous) F111 canopies and the people with Zp (Triathlons, Sabers, even a Stiletto or two). The people with the ragged old Cruise lites and Pursuits were slamming in hard. The canopies simply did not have enough lift left to slow down the jumper before landing.
    3. F111 canopies are a good choice for a first canopy.
    Well, yes and no. A good, fairly new F111 canopy, loaded correctly, is indeed a good first canopy. However, you have two things against you:
    Few people sell good, low-time F111 canopies anymore. Most have 500-1000 jumps on them, and at that age, they become difficult to land. A larger canopy will not be affected by this as much as a smaller canopy, so size matters. A pd230 may still land you well after 1000 jumps, since its forward speed is low to begin with. A PD150 with 1000 jumps will be very hard to land without injury for most jumpers.
      It's hard to resell F111 canopies, for the very reason mentioned above. They are generally retired after about 500-1500 jumps, do you're paying about $1 per jump for them. Zp lasts much longer - you can easily get 2000 jumps out of a Sabre 150 with an occasional line replacement. This ends up costing you around $.60 a jump. 4. Zero-p canopies open really hard.
    This rumor came about mainly because of the performance of the Sabre and the Monarch, two popular Zp 9-cells. It is no longer true. The Sabre was tamed by a larger slider, and mods exist for the Monarch. Newer Zp canopies, like the Triathlon, open quite reliably and comfortably. Some new Zp canopies, like the Stiletto, Spectre and Jedi, are designed to snivel for a longtime, and give extremely soft openings.
    This was a boon for cameramen, who need soft openings due to all the weight on their heads.
    Of course, there's a trade off between too little snivel and too much. But there are Zp canopies available that open at nearly any rate, from rapid to very slow. Packing is an important part of that scale, and between canopy selection and packing technique there should be a wide range of openings to choose from.
    5. You have to get a smaller canopy to get better landings.
    Not true. Many people start out on old F111 canopies, and simply assume that to get nice, soft, swooping landings like the pros, they need a small canopy like the pros. The truth is that nearly any Zp canopy will land you well, if you fly it correctly.The technique you use depends on the loading, as listed below:
    6. You need to get a smaller canopy to go faster.
    While it's generally true that smaller canopies go faster,there are many other options to increase your speed and turn rate without taking away wing area. Wing area is all you have keeping you in the air, and taking it away decreases the canopy's "forgiveness", or tolerance for mistakes. Some ideas for increasing speed/maneuverability without sacrificing area:
    Canopy choice. The Silhouette, for example, is designed to be a faster large canopy. A 170 should give you nearly the same forward speed as a Sabre 150, with the extra forgiveness that the larger size entails.
      Pilot chute. The single best thing you can do for your medium / high performance canopy is to get a collapsible pc. It will do wonders for your glide, forward speed, and flare. I highly recommend this as a first step, before you get rid of that old, doggy canopy. Even older F111's can benefit from this.
      Slider. Figure out how to stow your slider somewhere. There are many different types of collapsible sliders, and they affect performance two ways - by reducing drag, and by allowing the risers to spread out more. Avoid stowing it on your jumpsuit, though - this can prevent a cutaway if you have a problem later, and has led to a few serious injuries.
      Riser tricks. Mini-risers reduce drag a bit, but not a whole lot. Separate riser-keeper rear risers allow the toggles a bit more freedom, and distort the canopy a bit less when you flare, allowing a little more flare power. Front-riser handles allow you to easily add front riser, a good way to increase your speed when trying to buck a headwind (for example.) 7. You should never, ever turn near the ground.
    This is a good rule of thumb for your first few jumps.However, there are times when turning near the ground is necessary, and all jumpers should know how to do this safely. Basically there are two ways to turn low - the braked turn and the flare-turn. Practice these! Both allow radical turns without a resulting dive towards the ground. Many jumpers have been killed when they found themselves flying downwind or towards an obstacle on final, and tried to turn without using these tricks.Depending on the canopy, you can safely make a 180 degree turn as low as 50 feet - if you've gotten instruction on how to do it and practiced it up high.
    8. Skydive Chicago puts first-time jumpers on tiny Sabres.
    Not quite, but close. They put first-time jumpers on Mantas(or have them do tandems) for the first few jumps, then transition them to hp canopies. And interestingly, there have not been more injuries as a result. I think this is because many new jumpers learn bad habits on Mantas, and these bad habits are difficult to unlearn. At Skydive Chicago, they transition early on, and get good instruction on how to fly the newer hp canopies.
    This is a good model for transitioning ourselves. Whenever you're going to make a significant canopy transition (i.e.smaller, square to elliptical, etc.) get instruction! It costs little to badger a more experienced jumper or instructor into watching you land a few times, and the advice you get can be invaluable later.
    9. 7 cell canopies are dogs.
    Not any more! The Triathlon and the Spectre are both high performance Zp canopies, and are good choices for jumpers buying their first Zp canopy. The big difference between 7 and 9 cell canopies is aspect ratio - which is just the relationship between wingspan and front to back size. 7 cells have ar's around 2.5 to1, and 9 cells are around 3 to 1. Generally, a higher ar has a better glide ratio, but that's about the only hard-and-fast difference. Zp 7-cells can go as fast, land as well, and plane out as far as their 9-cell counterparts, if they are loaded correctly. They are a bit more forgiving at similar loadings, and are thus a really good choice for a first Zp canopy.
    10. It's really hard to pack Zp fabric when it's new.
    Sometimes this is true, but not always. "South African" fabric, such as the material they use in the Triathlon, is pretty easy to pack from day one. It doesn't seem to last quite as long as the more slippery PD material, though.Some canopies, like the Silhouette and the Turbo-z, mix F111 and Zp material to make a canopy that flies well and is still easy to pack.
    But even a brand new Sabre is manageable, if you work at it.The psycho-pack is a good way to control an unruly canopy, and there's at least one gadget out on the market that helps you pack slippery canopies.
    Copyright ©1997 Billvon Novak, Safety and Training Advisor

    By admin, in Gear,

    Buying your first set of Kit

    Mk 1 PC with sleeve in lightweight
    2 Pin Pack, Complete with matching reserve container.
    Lightweight I24 - unused. A bargain at only £250!
    Ideal First Kit! How many ads on the notice board at your parachute centre start or finish with these words?
    My immediate reaction is to want to tear down the ad, because the chances are it isn't. Take a closer look at the kit and it will be something that was 'hot' fifteen years ago, has not been in production for at least ten years, yet comes with the statement 'only 250 jumps'. The seller has to try to sell it to an unsuspecting novice, because no-one else would touch it. So, buyer beware! That is not to say that it is necessarily unsafe, merely it is not ideal first kit, unless your only consideration has to be cost.
    Advice should easily be on hand at any drop zone in the form of instructors and riggers (other than one who is trying to sell the kit!). Never buy your first set of gear without plenty of advice from someone whom you would trust. Always ensure it has been thoroughly checked beforehand. Apart from the serviceability of the gear there are many things you will need to take into account:

    experience level
    skydiving interests
    where and how much you will be jumping
    re-sale value
    your wallet! Let us look at some of these in greater detail and answer a few common questions:
    Experience level, age and weight
    If you have just achieved category 8, whether on the category system or through AFF, you will probably have between 20 and 40 jumps, possibly all on squares or mainly on rounds. If, like most people you have limited opportunity to hire equipment you will now need to buy something fairly soon. New may well be out of the question, because of the waiting time involved, the cost and the fact that your needs will change rapidly in the next few hundred jumps. There is a lot of second hand equipment about so don't be rushed into buying the first thing you see.
    All canopies will state an all-up weight limit for the equipment. This is to include yourself (with clothes), your rig and lead, if used. Many experienced (and some lesser so) jumpers use equipment for which they are overweight but swear by it because of the added performance they gain from it. This is not something to be recommended - the extra performance is in fact an increase in speed, both horizontal and vertical, which an inexperienced jumper is advised to avoid. You need to decide not just whether you can cope in 15mph winds on your big, familiar DZ, but also in nil winds, landing off the airfield in a small area.
    When buying your first equipment, it is not a bad idea to go one size up rather than being on or too close to the limit. Don't pay too much regard to the cool and groovies who will tell you how boring you will soon find it. Compared with an Aeroconical or a Manta it will be all the fun you need for a while and it will keep you safe for the first season or two.
    Your skydiving interests
    What do you want your skydiving equipment to do, other than the obvious decent opening and landing that we all desire?
    If you are interested in accuracy or CF you will need a canopy which is suitable for those disciplines. For either you are likely to need a larger, steady 7-cell. More performance can be gained from a higher aspect ratio (more rectangular than square) 9-cell. If you are not too bothered just yet, then either a 7-cell or 9-cell would be fine. There are more and more elliptical, ultra high performance canopies around . These are not intended for the novice and if you were to buy one there are not many CCI's who would let you jump it! 9-cells do usually give more performance (both in the air and for landing), they will tend to be faster but with a greater range of control. These days you can buy a safe canopy which will still give you plenty of forward speed, a good flare and lots of fun. Many canopies are zero porosity (ZP). They take a little getting used to when packing, but they will retain their performance for longer. As long as it is a sensible size for you and not an elliptical, a ZP canopy can be perfectly acceptable as a first canopy.
    Do I need a round or a square reserve?
    The answer is, if you can afford it get a square. These days it is possible to get decent equipment with a square reserve from £500 to £600 upwards. Consider when the wind is 20 knots on the ground, maybe 30 knots at 2,000ft, whether you would be happy underneath a round. It is not much fun to have to stand yourself down through lack of confidence in your equipment. Also, what is the standard of spotting like - not just on your home DZ, but when you go abroad to boogies? How many hazards are there around? How much overshoot? The only reason for buying a round reserve nowadays has to be because it is very cheap. If you do decide to go for the cheaper option but have never jumped a round, make sure you get briefed on it by an instructor.
    Whatever shape your reserve is, ensure you are within its weight limit!
    What type of container?
    This is really down to personal preference or availability if buying second hand. There are many types on the market these days. The most important thing is to make sure the harness is a good fit and comfortable, with all handles located in a sensible position. The main choice will be whether to have one or two reserve pins. Generally speaking, one pin rather than two will allow for an easier reserve pull. The maximum allowable is 22lbs, check on the repack paperwork how much it was. With a 'Pop Top' reserve (as on a Teardrop for example) the reserve pin(s) are against your back, so are very well protected in the aeroplane. But all modern equipment has covers that do the job. On some older rigs neither the main nor reserve pins are as well protected. This is something to be aware of when sitting down in and exiting the aircraft.
    What sort of deployment system is best?
    Until you are D-licence (category 10 and 200 jumps) you are not allowed to jump a pullout in the UK. This means ripcord or throwaway. Realistically, no-one jumps a ripcord after clearing student status, so you will need a throwaway deployment. But you still have a choice of where to put the pilot chute; on the leg strap or on the bottom of the container (BOC). Either is fine. If you are buying a second hand rig with one of these, you might as well leave it as it is. If your rig needs converting from pullout, you need to decide which to go for.
    These days increasingly the choice is to have a BOC. There are many good reasons. It will always be in the same place, whereas a leg strap can loosen or shift about. There is no (or very little) velcro to maintain. There is virtually no exposed bridle - relevant if you are doing high speed jumping such as free-flying. If you are having it converted there is no velcro to be sewn on the container, so it should be a little cheaper.
    The advantage of a leg strap throwaway is that it can be seen. Admittedly most people don't look for it but, one day when you are having difficulties, it may just save a second (200ft) if you can see a handle.
    Do I need an AAD or RSL?
    Once you are category 8, it is no longer a BPA requirement to have either. (If you jump at a military centre, the cut-off is category 10, so you have no choice until then.) It is only since the introduction of the Cypres that it has been common for anyone but a student to jump with an AAD. This was one of the reasons for designing the Cypres. It is an excellent piece of equipment and if you can afford it, get one. Quite simply there can be virtually no argument against it. If you are still in freefall at Cypres activation height (750ft), you deserve and need it to fire.
    There is more debate about the pros and cons of an RSL. Its function is to operate the reserve as you cut away. The disadvantage is that you may well be unstable immediately after a cutaway and hence for the reserve deployment. This is more likely for an extremely high performance canopy, which you are hopefully not jumping. It is more of a problem if you wear a camera on your head, this is not possible until you are D-licence. On balance, for a relatively inexperienced jumper with a relatively docile canopy, an RSL is a good idea.
    With both of the above, when you are no longer a student, you need to take more responsibility for yourself, so deciding how many safety features to have on your equipment is your decision.
    So why shouldn't I buy that 'Chaser / Pegasus / Preserve IV for £550 ono'? Although 'old' does not always mean 'knackered', the older a piece of equipment is, the more likely it is to be getting worn out. It would need a very thorough inspection of the harness and container - the stitching may be becoming unsafe. The webbing and risers may have spent ten years rubbing against velcro. The main canopy probably has hundreds if not thousands of jumps. It will have possibly lost most of its porosity, giving harder openings and landings. It is coming to the end of its life. Unless it is very cheap and you really cannot afford anything else, I would not recommend it.
    In summary
    Most equipment that is in good condition, with a square reserve and a main in the general range of 170 to 220 square feet will still be worth relatively the same in a year or two. You can buy it now, use it for a couple of hundred jumps and then resell it to the next generation of category 8 students. In the mean time you can improve your ability under canopy, try some other models and save up for new gear.
    Have a good look at the equipment that is around, compare prices and get advice!
    Cornelia Waymouth
    Illustrations Danny Crossman
    Skydive - The Mag

    Republished with permission

    By admin, in Gear,

    How To Select A Parachute Container System

    The harness/container assembly is your safety system. Any canopy, round or square, can be plugged into the main or reserve container/attachment, and be persuaded to open. The container system controls the deployment of those canopies. The harness secures you to those canopies. There have been a lot of dissertations on parachute canopies (how to select, fly, repair, etc…). Little has been published about the harness and container system, because, while seemingly simple, they are infinitely complex. The sheer number of the different emergency scenarios while skydiving is astronomical (i.e., low speed, high speed, total, partial, two canopies out, and so on). Your harness and container system must answer these challenges; it must answer them by prioritizing procedures in the order of the frequency of occurrence. Your job is to understand those options and make an intelligent selection. The purpose of this document is to help you understand the individual features you should consider while making this decision.
    The TSO is the minimum safety & testing requirement. TSO standards have changed over the years; so the present day TSO may be measuring one quality adequately but not another. There is a difference between a Performance Standard and a Structural Standard. A test to a “Performance Standard” is fine for a functional test. However, testing structural integrity is another matter. During a “Performance Standard” structural test, it is assumed that the canopy opens normally. In the real world canopies don’t always open normally. As we know there are frequent aberrant openings, usually dubbed “line strip” or “line dump” openings. This type of opening has, in fact, occurred during drop testing by some manufacturers. The results have been catastrophic. Some of the manufacturers who have experienced this have built their products to withstand these aberrant openings. Some have not. Some have modified their products after the original testing with no consideration for the reduction of structural integrity. How can consumers protect themselves? Ask the manufacturer about the strength of their webbing and hardware. Ask them to what load the harness has been proved. Then ask their competitor to confirm this claim. Ask them if the harness is “fail safe”. That is, which location/joint will fail first and what will happen to the wearer if and when it does fail. The wearer should not come out of the harness.
    The Ultimate Test
    Time in the field = Proof of performance. It takes a minimum five years to “prove out” a new feature of a rig.
    Container Flexibility
    There are two choices for container comfort and fit. One is a soft flowing container which flexes and bends and is easy to pack. The down side of this choice, is that this type of container may “catch air”, and create excess drag. The other choice is a hard packed, molded container that is small enough to be completely out of the air flow, and will allow full body movement. This type of container must be shaped by design. Before you put it on look at it -- it should have a shape waiting to clamp onto your back. Modern design contour fit!
    Container Fabric
    There are several fabric types used in the manufacture of sport containers of today. They are generally divided into two categories: Parapac and Cordura. Certainly there is a sub difference of the base types. That sub division is usually defined by denier. military containers used a 420 denier Mil-Spec C-7219 Parapac. This fabric is specifically designed for use in parachute containers. There are deniers less than 420 available and they should be avoided except for decorative purposes. Cordura has proven to be a popular and durable fabric for use in containers in spite of it’s excess weight. Theoretically, Cordura is more ultraviolet resistant because the coarseness of the material casts a larger shadow protecting it from ultra-violet deterioration.
    Reserve Container Design
    There are two basic reserve container designs in common use today. They are internal pilot chute and external pilot chute. On the internal design multiple side flaps are cantilevered over the pilot chute to a locking loop through a grommet which is secured with a ripcord pin. The external system has the pilot chute sitting on the outside of the flaps with loops passing down through the flaps between the folds of the canopy to the back side of the container where they are retained with the loops through a grommet by a ripcord pin through the loop.
    Main Container Design
    Which flap closes first and which flap closes last? On some containers this is critical. Buy a container where it either doesn’t matter or where they can’t be assembled incorrectly.
    Available Sizes
    With the availability of over two hundred main canopies alone, container sizing has become an enormous challenge for container manufacturers. Generally, most mains are bigger than the reserve by a small percentage. The sizes of the canopies and the ratio between them should be close(See How To Select The Right Canopy For You). However there are times when you might need to vary from this practice, such as for an accuracy rig. The containers you buy should be sized for the canopy that will go into them. Over-stuffing and under-stuffing can cause problems i.e. cause the container to wear out more quickly by overstressing stitch areas and grommets, in the case of over-stuffing; premature openings, caused by pins falling out of loosely loaded loops, in the case of under-stuffed rigs. Be advised that similarly sized (square) main and reserve canopies seem to fly in unison better if you happen to have both open at the same time. This is a highly debated topic in recent years, with the world-wide move to square reserves and more frequent use of AAD’s.
    Main Deployment Choices
    In the beginning there were ripcords and spring loaded pilot chutes for deploying our mains from our backs, and reserves from our chests. This system worked by packing a conical spring loaded pilot chute, in compressed form, inside the main container, on top of the canopy and it’s devices. The container was held closed with a cone and grommet/pin system with the release pin on a cable leading to the release or ripcord handle. Pulling on that handle pulled the pin from a hole in the cone allowing the grommet to slip off of the cone, thus releasing the container flaps and allowed the spring to expand and spring out of the pack, hopefully. There were other variations on this theme, such as umbrella type springs, a even a springless pilot chute which was a hat (yes, a real hat!). To deploy, you removed your hat and flung it into the air; which brings us to the next generation in main deployment.
    Hand Deploy / Throw-Out
    While the hat trick was a little difficult, a pouch, external to the container, was devised. With the handle for the pilot chute mounted on the top or apex of the canopy, the springless pilot chute was folded into this container and the bridle to the container was Velcro’ed to the rig along its path to the pin on the container. The pin is curved to allow angular loading. Pulling the pilot chute out of the pouch with the handle on the top, and tossing the canopy into the free stream is all that is required to deploy the main. Pouches for this system have been mounted in several places, from the front of the leg strap, to the back of the leg strap, to the bottom of the main container.
    The pull-out retains the sequence of the ripcord system and provides the added safety of keeping the springless pilot chute in the same container as the main canopy. It is equipped with a handle, mounted on the back, lower outside corner of the main container. Pulling that handle extracts the straight ripcord pin allowing the container to open, and the internally stored springless pilot chute to be put into the free stream. The handle on this system is mounted on the base of the pilot chute.
    AAD On Main?
    Generally in this sport, AAD’s are mounted on the reserve container. Some skydivers, and the entire "East Block", have however, elected to put their AAD’s on the main. It was explained to me this way. "I want my AAD on my main because my greatest fear is to be knocked unconscious in freefall. I would prefer to wake up under a malfunctioned main than I would under a malfunctioned reserve."(Al Kruger a.k.a. "Captain Hook"). Of course, having an AAD on the main would require a spring loaded pilot chute.
    Reserve Deployment
    Reserves must deploy in two different environments. Slow speed, after a cutaway, and high speed, in the event of a totaled main. According to TSO C23c, slow speed deployments are required to complete within 3 seconds after a cutaway. The test allows no more than 2 seconds of free fall after the cutaway before pack opening. If an RSL is used, the benefit of the speed acquired by the 2 second free fall is lost and the reserve must still deploy in 3 seconds. Trying to control the “not more than 2 seconds” rule is difficult, and is allowed only because, without an RSL, there must be some delay. The intent is for immediate deployment. Manufacturers have played games with this specification. Some have interpreted it by saying, “if it opens in five seconds after cutaway it’s OK”. NOT TRUE! The only test that can be trusted is the test where an RSL is used. This is a critical feature, as there are many combinations of canopies and containers in use today which do not meet this requirement. Your only protection is to see a video of the tests. DON’T BUY a system without seeing a video of its reserve deployment abilities. Take a stop watch with you when you view this video and time the deployment. Time it from pack opening to full canopy. Make sure that there is no more than 2 seconds from the cutaway to the time when the pack is opened. If your time on the deployment is more than 3 seconds don’t buy it.
    The high speed requirement is not difficult to meet, but some do fail this parameter. It is generally accepted that a reserve should open in 350 feet, at terminal. That equates to about 2 seconds at 174 ft./second. The testing is done by throwing the dummy out at 500 feet, at speed. The test is not timed and is not difficult to meet.
    Riser Covers (Main):
    There are two choices for main riser covers. Open or trough type covers, and Velcro sealed closed covers. If you skydive on your chest all the time, then you might like the open or trough type. If you skydive in other configurations you will prefer the sealed type, as they don’t open when you are on your back. Recent improvements to the trough type include an "over riser" inside flap.
    Harness Strength
    There are several types of webbing used in the manufacture of personnel delivery harnesses. To understand the choices requires a little history lesson. Originally, harnesses were made of cotton webbing. During this era hardware was designed for use with the cotton webbing. We use the very same hardware today. When nylon was invented, it became apparent that nylon was infinitely better than cotton for use in most applications, especially personnel harnesses. Rather than retool the hardware, the nylon was then configured to be compatible with the hardware. The resultant product was 7000 lb. tensile, Type 13 harness webbing, identified by a black edge trace. At the same time Type 8 (Black Center Line, 4000 lb. tensile), and Type 6 (Red Center Line, 2500lb Tensile) were designed to be used with the Type 13 in a supplemental roll, where involvement with hardware and exposure to environmental hazards were not a concern. Additionally, Type 7 (Yellow edge trace, 6000 lb. tensile) was introduced at that time for use in cargo delivery, where no interaction with personnel hardware would occur. Some sport manufacturers have adapted this weaker webbing (Type 7) for use in sport harnesses. While strength has been a minor issue with this application, it does slip in the hardware and won’t hold proper adjustment.
    Friction Adapters are the only hold over from the cotton webbing days. Most harnesses don’t use any other hardware, as additional hardware adds weight and creates a weak spot in the harness. Additionally, hardware can cause bruising of the wearers body. On harnesses where other hardware is used, for articulation for example, the consumer should know the ultimate strength of the hardware and its associated joint. A minimum of 4500 pounds, with a “fail safe” configuration is required for safety along the main lift web.
    Harness Comfort
    Sizing and fitting a harness is like sizing and fitting a suit of clothes. There are several benchmarks or “hard points” that must be held as the harness size changes. One is the point of suspension; it occurs at the top of the pectoral muscle in the hollow of your shoulder. Many rigs allow this point to rotate up to the top of the shoulder. This is incorrect and you will know it when you look under the shoulder portion of the harness and while the chest strap is keeping your mouth closed. If your harness suspends you correctly you will feel like you are sitting in a chair. This might require sliding your leg straps down under your thighs after opening. The other benchmark is the top of container. The harness must encircle your body while holding these two points. You should make sure that the harness you buy is custom made for you and that the manufacturer sizes your harness in both the main lift web and over-the-shoulder dimension. The harness must be comfortable in three different environments: in the air (in freefall), under canopy, and lastly on the ground. In the air we are usually on our bellies; under canopy, sitting in a chair; and on the ground, walking. The flex of webbing accomplishes this job just fine if the harness is configured properly.
    Harness Materials
    Harness materials should meet mil-spec., but that is not enough. The material must be used as design intended. The webbing should be “shuttle weave”(the weave of both edges look the same) as opposed to “needle weave”(the weave of both edges look different). A “shuttle weave” is a locking weave, that will not unravel if the edge is nicked or broken. Refer to The Parachute Manual, pg. 80 - , sections 4.060 through 4.062.
    Comfort Pads
    There are two kinds of foam used in comfort pads -- closed cell and open cell. Most manufacturers use open cell foam that they buy at the carpet store. Buy a rig that uses closed cell athletic padding that will float and not absorb water.
    Riser Releases
    The riser release system in common use today is the “3-Ring”, it is the de facto standard. There are several variations of this design in use. Due to some recent incidents where cutaways have been from difficult to impossible, I would anticipate additional variations or improvements. The 3-ring is a single point riser release system designed around three rings of decreasing diameter. Each is able to nest inside the larger with clearance for mounting webbing. They are secured and released with a locking loop, through a grommet, into a “push/pull” cable system that releases both sides. The housing pushes, while the cable pulls from the locking loop, which when released, allows the ring/levers to “tumble” open. There are two sizes available. The mini, which is capable of approximately 3600 lb. load and has about a 60 to 1 mechanical advantage, and the large or standard, which has more than a 200 to 1 mechanical advantage. The mini is generally accepted as adequate for normal solo sport jumping. The large is used for tandem, military and situations where high loading is anticipated. (See “The 3 Ring, What It Is And How It Works”)
    Option Availability
    You should look for a rig manufacturer who can provide you with the options your skydiving requires. Be reasonable, there are some options which might be dangerous. Find a designer with whom you can talk it over.
    Pilot Chutes
    Pilot chutes have become an included component in Harness and Containers, therefore they should be discussed.

    Main pilot chutes were generally discussed in the “Main Deployment” section. They do have some additional features mentionable here. There is large hole mesh and small hole mesh and there are two types of canopy fabric in common use, Zero-P and F-111. The zero-p is a silicone coated F-111, and as such, has a lower permeability, both initially and in the long run. The initial difference is minor, and for all practical purposes doesn’t exist. However, if you consider the following you can make your own decisions about the fabric and the mesh. A colander or sieve is held under a slow running stream of water. The water passes through the sieve as fast as it enters. Increase the water flow and the sieve will fill up and the water will spill over the edges. This is equivalent to what happens with porous fabric being drug through the air.
    There are two important aspects of the reserve pilot chute. As it is usually spring loaded, the “jump” or launch of the spring is important. Additionally the drag capability must be considered. While you can judge the jump with your eye (remember to judge it coming out or off of the container) the drag capability is more evasive. You could drag them through the air with a fish scale but your airspeed might vary from jump to jump. The only way to accurately determine the coefficient of drag, is in a wind tunnel test. Poynter reports on tests of several kinds which might be enlightening and help to establish a mental base line. You must ask the manufacturers and judge their answer. If they can’t supply a “Coefficient of Drag” number beware!
    Auxiliary Systems
    Read our What you should Know About RSL’s article.
    Will the rig of your choice accept the AAD of your choice? Has the rig maker approved the AAD makers installation? Has the AAD maker approved the rig makers instructions? The important thing to remember whenever you consider an AAD, is that the container, not the AAD, is the primary life saving device. The AAD must not interfere with the proper function of the TSO’d container and its TSO’d reserve.
    John Sherman

    April, 1996

    © The Jump Shack
    Reprinted with permission

    By admin, in Gear,