Parachute Rigger HandbookFAA-H-8083-17A
Chapter 04
Operations
17 pagesPages 4-1–4-17
Introduction
Certificated parachute riggers represent a professional cadre within the parachute community. According to Title 14 of the Code of Federal Regulations (14 CFR) part 65, section 65.129(f)(1), “No certificated parachute rigger may exercise the privileges of his certificate and type rating unless he understands the current manufacturer’s instructions for the operation involved and has performed duties under his certificate for at least 90 days within the preceding 12 months.” Manufacturers of main parachutes have packing techniques that they have developed for their products. Most of them follow established methods in common use. Experience has shown that if the packing techniques required for a specific main are too complex, the market may not receive them favorably.
Throughout the chapter, each component of the parachute is discussed along with its function and how it applies to the entire assembly. One component can have a significant effect on the performance of another. For example, a pilot chute that is too large may result in too fast of an opening; and a pilot chute that is too small may not be able to overcome a bag lock.
Sport Parachute Main Packing Techniques
When we talk about “square” parachutes, what we really mean is rectangular plan form, semi-elliptical, or elliptical plan form. [Figures 4-1 through 4-3] Plan form refers to the shape of the canopy from a “birds eye view.”
Figure 4-1. Rectangular plan form canopy.
Figure 4-2. Tapered tip plan form canopy.
Figure 4-3. Elliptical plan form canopy.
There are essentially two ways to pack a square parachute: flat packing or proper ram-air orientation (PRO) packing. When flat packing, the canopy is laid on its side so that you are viewing it in profile. The canopy is S-folded stacking the line groups on top of one another. Variations to this method include rolling the nose from the leading edge to the A line, toward the tail, or splitting the nose cells in half, rolling them inward, and tucking them into the center cell. The tail is then split and cocooned around the rest of the canopy.
The most common method of packing “square” mains and reserves, however, is PRO packing. Developed by John Sherman in the early 1970s when “squares” were first being introduced, the premise was to pack them the same way one would pack a round parachute—that is, to separate the four line groups and flake the perimeter of the parachute with the nose facing forward and the tail of the canopy facing rearward. If one were tall enough to raise the round parachute off the floor, it could be PRO packed. The advantage of PRO packing is that it results in a more even distribution of forces during opening shock and on-heading openings. Figures 4-4 through 4-35 illustrate PRO packing. There are several variations to this technique designed for special purposes. Free fall cameramen may require a slower opening to reduce the opening shock. Canopy Relative Work (CRW) parachutists may want faster sub-terminal openings. The rigger should be able to provide guidance to the parachutist for the type of opening required.
Figure 4-4. Check line continuity and separate line groups. Cock the slider.
Figure 4-5. Set the brakes and walk up the lines pushing the slider ahead of you. This is also known as “Doing a 4-line.”
Figure 4-6. The nose of the canopy is facing the packer. The tail of the canopy is facing outward.
Figure 4-7. Flake out the cells of the canopy at the nose, pressing them against your thigh.
Figure 4-8. Tuck the nose of the canopy between your legs.
Figure 4-9. Flake the canopy fabric between the A-B, B-C, C-D line groups following the perimeter of the canopy.
Figure 4-10. Separate and clear the material between the line groups.
Figure 4-11. Note the staggered order of the line groups. The As are the highest; the Ds are the lowest except for the upper control lines at the very bottom of the picture.
Figure 4-12. The slider can be quartered or simply halved with the slider grommets resting up against the slider stops at the stabilizers.
Figure 4-13. Pull the tail up over the canopy and hold it under your thumb.
Figure 4-14. Roll the tail to prevent the canopy from splaying out when it is laid down on the ground. Be sure to prevent the upper control lines from coming around to the nose of the canopy. Keep them centered and back.
Figure 4-15. Press the air out of the canopy.
Figure 4-16. Lay the canopy down on the ground.
Figure 4-17. Cocoon the canopy making it a uniform width.
Figure 4-18. The “cocoon” should be slightly wider than the deployment bag.
Figure 4-19. Pull the kill line out of the bag at this time.
Figure 4-20. Use a knee to keep control of the top of the canopy.
Figure 4-21. Make the first “S” fold.
Figure 4-22. Use a knee to maintain control of the canopy.
Figure 4-23. Make an additional “S” fold.
Figure 4-24. Most canopies take two S folds. Pull PCA ring outward so that it is up against the grommet inside the bag.
Figure 4-25. Insert the canopy into the bag one side at a time.
Figure 4-26. The objective is to fill the corners of the bag and keep the center of the pack job soft.
Figure 4-27. Shove the canopy down into the bag filling the corners.
Figure 4-30. Make a locking stow.
Figure 4-28. Use the flap of the bag to help control the canopy.
Figure 4-31. The second locking stow. Note the generous size of the bight.
Figure 4-29. The closing flap of the bag is pulled so that the grommets meet the rubber bands. You should not have to stretch the rubber bands very far.
Figure 4-32. Keep the stows neat and separate. Here, the weight and mass of the lines is balanced to prevent line strip.
Figure 4-33. Pull pilot chute kill line from bottom of bag.
Figure 4-34. Pull the kill line through the bridle.
Figure 4-35. Drop the excess line into the pilotchute.
Deployment and Inflation Characteristics
Main canopies have changed dramatically over the last several years and, consequently, different opening problems have emerged. Some canopies are inherently hard openers, while others are inherently slow openers. Accuracy canopies, with their thick airfoils and large overhanging topskins, fall into the first category, while thinner airfoils, with flatter trim and baffled leading edges, tend to fall into the latter. One of the most common problems encountered is that of hard openings. Line strip or line dump is the leading cause of hard openings. This occurs when inadequately-stowed lines come off of the bag all at once instead of releasing one line bight at a time in an orderly fashion, and subsequently the canopy is allowed to inflate prior to line stretch resulting in sometimes an explosive opening. Securing the lines so that it takes approximately 12 pounds of force to release each bight is accomplished with a proper stow band and balancing the weight and mass of the lines by placing 50 percent of the line weight and mass on the mid-section of the bag and 25 percent of the weight and mass on each side of the bag. This alleviates the problem of line strip.
There are other methods employed to reduce hard openings, such as rolling the nose of the canopy to delay the initial inflation process as the leading edge unfurls. This rolling technique varies from a single roll to several rolls. [Figure 4-36] If this does not solve the opening problem, riggers should contact the manufacturer for advice. Most manufacturers are very cooperative and have considerable expertise in working with their products.
Figure 4-36. Rolling the nose of the canopy.
The manufacturer may recommend modifying the slider size or deployment brake settings. Of these options, the easiest to do is to change the brake setting. Reducing the brake setting results in less pressure on the canopy during opening, thereby reducing the opening force. The negative effect of reducing the brake setting is an increase in opening surge. The new brake setting must find the balance of these results that best fit the user. If changing the brake setting does not work, then the rigger may wish to increase the size of the slider to slow the openings. This usually means replacing the slider with a larger one. This has the effect of increasing the drag on the slider and restricting the canopy inflation. Another effective method of preventing hard openings is to install a 2-inch diameter rubber band on the center B or C line attachment tab and stowing the apex of the slider in a single wrap of that band. [Figure 4-37] The jumpers’ airspeed also has a significant effect on opening shock. Jumpers should make a conscious effort to slow down before putting out their pilot chute, and then assume a slightly head high attitude in preparation for opening.
As canopies age and accumulate substantial jumps on them, many begin to develop slow openings, commonly known as “sniveling.” If the canopy was originally packed with the nose rolled, reducing the number of rolls may speed up the openings. However, many times the slow openings are due to other causes. Probably the main reason for canopies developing slow openings is increased porosity that occurs with frequent use. It is especially noticeable on canopies that have a “lip” or a baffled nose. These particular design features cause a canopy to open slower for softer openings, which is a desirable characteristic, but as the canopy fabric wears and permeability increases, the openings may get too slow. The effect on fabric that originally had a permeability of 0–3 cubic feet per minute (CFM) or 0–5 CFM, such as PIA-C-44378, may not be as dramatic. With these canopies, pulling down the tail by deepening the brake setting speeds up the inflation of the canopy. The rigger must be careful not to set the brakes so deeply as to place the canopy in a stall during opening. If this does not work, then decreasing the size of the slider or the fabric type of the slider may help speed up the openings. The size and condition of the pilot chute may also contribute to the perceived speed of opening.
Figure 4-37. Rubber band on center C-Line attachment tab holding apex of slider.
Another cause is when the canopy gets out of trim due to the stretch of the suspension lines or shrinkage of steering/ brake lines. The rigger should check the trim of the canopy against the manufacturer’s specifications and either re-trim the canopy or re-line it. This may have a pronounced effect of improving the openings, as well as the flying characteristics.
Main Pilot Chute
Hand deploy pilot chutes are made from either the
PIA-C-44378 (0–3 CFM) (formerly known as F-111 which is a proprietary brand name that is no longer manufactured.
Currently 0-3 CFM is commonly referred to as Silktique and Exazta-Chute) fabric or zero porosity (0 CFM) fabric. The PIA-C-44378 fabric begins as a very low-porosity fabric but, as it is used, the permeability increases. When this happens, the drag of the pilot chute decreases. Consequently, the ability of the pilot chute to “lift” the weight of the canopy decreases and the speed of the opening is affected. Experience has shown that pilot chutes made from this type of fabric exhibit a decrease in performance at around 500 jumps under normal use. Pilot chutes made from the ZP fabric last considerably longer than those made from 0–3 CFM fabric. However, there has been some disagreement concerning the use of the two different fabrics in pilot chutes. One canopy manufacturer advocates the use of F-111-type fabric only. They believe the ZP fabric contributes to hard openings. Most parachutists like ZP pilot chutes because they last longer. The size of the pilot chute has a direct correlation to the type of opening experienced. In the early days of hand deploy chutes, a 36- inch 0–3 CFM pilot chute was standard on most systems.
As the canopies became smaller and lighter, pilot chutes became smaller as well. Today, 24-, 26-, 28-, and 30-inch pilot chutes are all common.
Several factors dictate the size of the pilot chute used. The first is the weight of the canopy. Another factor is the main container closing configuration. Some systems are designed to hold the deployment bag so securely that it requires more drag to extract it from the container. This type may require a larger pilot chute than the type of container that allows unrestricted extraction of the bag. This same problem can develop when an individual packs an oversized main canopy into the main container. If a larger deployment bag is used to hold the additional volume and the bag is forcibly stuffed into the container, the bag can be restricted from being pulled smoothly from the container. If the pilot chute is too small, a pilot chute in tow can result. If the parachutist puts a larger pilot chute on the system, the bag can be extracted from the container, but the increased size of the pilot chute contributes to increased snatch force during the opening sequence. This results in perceived hard openings.
It should be noted that deployment bags are matched dimensionally to containers—not to canopies. If the tray of your container is 12 inches wide, 7 inches long, and 5 inches thick, the bag should also be those dimensions. Forcing a larger bag into the container overstresses the flaps, grommets, stiffeners, and some loop anchors. Conversely, if you put a smaller canopy than was originally intended into the container, you should use the same bag and pack the canopy as wide and “fluffy” as possible. In other words, do not squish all of the air out of the pack job as you normally would. The main closing loop should be appropriately shortened.
Using a smaller bag than the container was built for can result in unsafe conditions as well. In the event of a premature container opening, the bag may float out before the jumper has an opportunity to deploy the pilot chute. Some friction is desirable so that the bag rotates out of the container in the proper sequence—bridle up, lines down. There is an exception to this tenet for wingsuiters, who essentially open in a track. So, the size of the pilot chute and, to some extent, the deployment bag can have considerable effect on the opening of the main parachute.
Bridle Length
The length of the bridle has an effect primarily on the deployment of the main pilot chute itself. In the case of a throw-out pilot chute, the bridle must be long enough to get the deployed pilot chute out of the turbulence in the wake of the jumper’s back. If the bridle is too short, the pilot chute stays in the parachutist’s burble. The length of the bridle from the locking pin to the pilot chute averages around 7 feet. Recent years have seen the growth of the use of the “birdman” flying suits or wingsuits. Because of the increased surface area and the decreased free fall speeds, the use of a longer bridle has become common, with a 9-foot length working well. Along with the longer bridle, containers have been modified to allow the bottom to open fully and the main bag to be extracted rearward towards the feet due to the more horizontal trajectory of the parachutist. Some manufacturers have also reoriented the mouth of the main deployment bag for wingsuiters so that the lines are sitting on the floor of the container tray rather than the bottom flap. This way the bag rotates 90° out of the container rather than 180°.
In the case of a pull-out pilot chute, where the jumper actually pulls the pin, the pilot chute is placed with an arc motion of the arm in the fast air near his or her head so as to avoid the burble. The jumper’s grip on the pull-out handle is gradually released as they rotate into a head-high position, reducing the size of the burble, and in preparation for opening.
Rubber Bands
The rubber stow bands play an important part in the deployment sequence and serve two important functions.
First, they hold the mouth of the deployment bag closed and prevent premature deployment of the main canopy.
Secondly, they hold the line stows securely to allow a clean, orderly deployment of the lines. With the advent of smaller diameter lines, such as 550 or 725 Spectra® and HMA®, smaller diameter rubber bands have been developed to properly secure these lines. If the smaller rubber bands are not available, many parachutists double stow the larger rubber bands around the small lines.
There are other products, which are designed to replace rubber bands and last longer, but they have downsides. Rubber bands other than military standard (Mil Spec) rubber bands may not break at the desired 40–45 pounds and can lead to bag locks. Other products may not have enough retention ability and allow the lines to “dump.” Figure 4-38 shows the various rubber bands and Tube Stoes®. In addition to the correct rubber bands, the length of the line stows is important as well. In the past, 1-inch stows were common, but today 3-inch stows are recommended by several manufacturers. Figure 4-39 shows the comparison between the two lengths. The main point to remember is that the lines must be stowed neatly and securely.
Figure 4-38. Rubber bands and Tube Stows®.
Figure 4-39. Line stow length comparison.
Assembly of the Main Canopy To The Harness and Container
The rigger should be familiar with the various types of canopy releases currently in use. In skydiving, the most common release is the 3-ring release system. It was originally developed in 1976 for skydiving, but has since become the dominant release system for intentional jumping, both civilian and military.
Riggers must be familiar with the assembly of the 3-ring release since they may have to connect new canopies to the harness and container or have to disconnect the main canopy to untangle it after landing. Shown in Figures 4-40 through 4-47 is the correct assembly sequence. The rigger must also be able to inspect the 3-ring release to determine any wear. In particular, the following areas need to be inspected:
Figure 4-40. 3-ring layout.
Figure 4-41. 3-ring middle through large ring.
Figure 4-42. 3-ring small through middle ring.
Figure 4-43. 3-ring loop over the top ring.
Figure 4-44. 3-ring loop profile view.
Figure 4-45. 3-ring housing terminal over loop (rear).
Figure 4-46. 3-ring cable through loop.
Figure 4-47. 3-ring assembled (from front).
Harness 3-ring attachment—check for wear on the webbing and any damage to the ring or chipping of the plating. [Figure 4-48]
Figure 4-48. Harness 3-ring inspection.
Main riser rings—check for webbing wear, hardware plating, grommet wear, and locking loop wear/ damage. [Figure 4-49]
Figure 4-49. Riser release end.
Release housings—check for damage to terminal endings and grommet, obstructions or dirt in housing, and check security of the housing tacking to the harness. [Figure 4-50]
Figure 4-50. Release housing and terminal.
3-ring release handle—check the cable for cleanliness and cracks, and ensure that the cable ends are sealed. Yellow Lolon cables must be oiled monthly to ensure release-ability. [Figure 4-51] Red or orange Teflon cables do not require oil but should still be inspected every 180 days; inspect the Velcro® on the handle. [Figure 4-52]
Any questions concerning the particular harness 3-ring installation should be directed to the harness and container manufacturer.
Figure 4-51. A 3-ring release handle with yellow Lolon cable needs oiling.
Figure 4-52. A 3-ring release handle with orange Teflon cable does not need oiling.
Assembly of Components and Compatibility
Advisory Circular (AC) 105-2D, Sport Parachuting states that “the assembly or mating of approved parachute components from different manufacturers may be made by a certificated, appropriately rated parachute rigger in accordance with the parachute manufacturer's instructions and without further authorization by the manufacturer's or the FAA.” This allows the rigger to assemble different canopies to different harness and container systems. This is an important authorization for any rigger in that there are dozens of possible combinations. When various parachute components are interchanged, the parachute rigger should follow the canopy manufacturer’s instructions, as well as the parachute container manufacturer’s instructions. However, the container manufacturer’s instructions take precedence when there is a conflict between the two. The logic behind this is that the container is the active component and the canopy is the passive component with regard to deployment. Determining compatibility is more than simply determining the volume compatibility of a canopy to a container size. Other factors, that need to be considered are the deployment type, technical standard order (TSO) certification, and placard limitations.
Reserve Bag Extraction Force
When we ask the question, “How do you determine compatibility between approved parachute components,” the answer is, “Rig functionality must not be compromised.” Some say if a reserve canopy is too bulky, the reserve deployment bag is not easily extracted. If you can get the bagged canopy in the container, it should take no more than 18 pounds of pull force to extract it.
TSO Certification and Placard Limitations
This area is one where many riggers have some confusion. According to AC 105-2, Sport Parachute Jumping, “the strength of the harness must always be equal to or greater than the maximum force generated by the canopy during certification tests.” In the case where the harness is certificated under TSO-C23b and the canopy under TSO-C23c, the maximum generated force of the canopy must not exceed the certificated category force of the harness and container (i.e., Low Speed Category (3,000 pounds) and Standard Category (5,000 pounds)). In this instance, no additional marking on the container is necessary.
In the case where the canopy is certificated under TSO-C23b and the harness under TSO-C23c, the strength of the harness must be equal to or greater than the certificated category force of the canopy.
For the current TSO-C23d, the peak force measured during the strength drops must be placarded on the outside of the harness. In this case, the strength of the canopy must not exceed that of the harness.
The rigger, when making the determination as to whether a particular canopy and rig combination is compatible, must consider all of the above areas. If there is any doubt, the rigger should contact the rig manufacturer for guidance.
Harness Strength
TSO-C23b was originally written back in the 1940s before the advent of square parachutes. It had two categories under which a parachute system could be certified. The “Low Speed” category was limited to use in aircraft under 150 miles per hour (MPH) and certified to 3,000 pounds. This category required large block letters decrying “limited to use in aircraft under 150 MPH.” It also had a “Standard Category.” This category required no warning labels and had neither weight nor speed limitations and was tested and certified to 5,000 pounds. It is important to note that neither category had a weight limitation.
Weight has only a minimum effect on parachute opening forces. To be exact, if you were to increase a given weight by 50 percent, you would only see a 5 percent increase in opening force; likewise if you double that given weight, you would only see a 10 percent increase in opening force. This seems counter intuitive until you think about it. Speed is the critical factor that hurts us and our equipment when we have the occasional hard opening. But because speed is often derived from mass or weight, we associate the hard opening with primarily weight. Let us look at the calculations. The math model for opening forces is described in the “Recovery Systems Design Guide” by Theodore Knacke.
The definitions and formula is as follows:
Force—total opening forces
Cd—drag coefficient of canopy
So—square footage of canopy
Q—dynamic pressure in pounds per/square foot (½ ρʋ2)
X1—decreasing load factor
NOTE: There are 2 methods for deriving this factor.
The Pflanze method and a lookup of the chart included in the reference manual. The chart is the simplest for personnel parachutes and effectively results in being one tenth of the pound per square foot loading.
Cx = shock load coefficient which is derived from testing and includes such things as slider size, brake setting, angle of nose cut, etc. For this exercise we will use a value of 1 as this number ranges from .5 to 1.5 or so. Without a slider it can go as high as 10.
Therefore: Force = Cd × So × Q × X1 × Cx If we group the Cd × So × Q and calculate them, at first we get a big number ie:
Cd = .8 So = 200 square feet Q = 33 PSF @ 117MPH together = .8 × 200 × 33 = 5,280 pounds. This number is then ameliorated by the X1 decreasing load factor and the Cx shock load factor. If the Cx is 1 (and we will assume this for this example), then it has no effect on the outcome.
The X1 factor is the key because it is based on pounds per square foot loading multiplied by 1. If you try different weight values and reiterate the formula, you can see it only changes the X1 factor by fractional amounts and only affects the outcome minimally as described earlier.
National Aerospace Standards (NAS) 804 has the best requirements for structural integrity of any standard written to date. This is because it has a strength requirement: 3,000 pounds for the Low Speed Category and 5,000 pounds for the Standard Category. Other standards (AS8015) use a performance requirement (weight versus speed) for structural integrity verification. This would be acceptable except for one small problem. AC 105-2, Sport Parachute Jumping, allows for mixing and matching of approved components. This is a problem because different canopies open with different opening characteristics at the same weights and speeds. This is defined and accounted for by the Cx value. Therefore, if a harness is built and tested using a canopy with a low Cx and matched with a canopy (under the provisions of AC 105-2) with a high Cx, the results could be disastrous.
NAS 804 systems need no further consideration other than originally called for. The Low Speed designation is limited to use in aircraft under 150 MPH at any weight. Likewise, the Standard Category of 5,000 pounds has no weight or speed limitations. This is an unlimited category. One reason for this is because of the limited effect of weight on opening forces. Speed is what kills. If a human body were to reach a 5,000 pound shock load, it would come apart before the harness or canopy. At less than 150 MPH, even at a high weight, it will not exceed 3,000 pounds.
It may be evident now that there is a flaw in our structural requirements due to the mixing and matching of approved components under the performance standard versus a structural standard. This came about as a result of the change from a Structural Standard (NAS-804) to a Performance Standard (AS 8015b). Now we have no way to determine compatibility for TSO-C23c (AS8015b).
It may not be possible to have compatibility using performance standards alone. That is why we added placards for the “weight tested to” for harnesses and the “force generated” for canopies to TSO-C23d. There is no way to determine compatibility from one parachute system to another within the same category of the same standard if they are judged using a performance standard. Just because they were tested at the same weight and speed does not mean they saw the same opening forces. Different canopies open with different characteristics. Listed below is a hypothetical comparison of the opening characteristics of two different systems tested to the same performance standard. The math is the same as previously discussed. The two canopies have very different opening characteristics, and they produce very different results when tested at the same levels. When a mix of the two systems is applied and subjected to a high-stress sport jump, the capability of the harness may be exceeded. Both systems were tested using a 300-pound test dummy at 180 knots (207 MPH) Cat “B” TSO-C23c.
System 1: 200 square foot canopy W/.8 Cd produces a 1,304 pounds force on opening at test speeds.
System 2: 100 square foot canopy W/.9 Cd produces a 3,668 pounds force on opening at test speeds.
The ratio of opening force differential is 2.8 to one or System 2 opens with 2.8 times greater force than System 1.
Let’s say a harness is built for System 1 using 1,500 pounds capable hardware. It passes the structural drops, as it only sees 1,304 pounds.
Another harness is built for System 2 that has a canopy with desirable flight characteristics but that tends to open hard. The jumper wants the canopy with desirable flight characteristics in his new System 1 rig. If compatibility is derived from performance standards, then these are compatible since they were both tested using a 300-pound drop test dummy at 180 knots. It is entirely possible that a sport opening under extreme conditions could produce an opening of 1,600 pounds, which exceeds the capability of the 1,500 pound hardware. [Figure 4-53]
Figure 4-53. Canopy characteristics.
TSO-C23b does not really have any limitations except for speeds below 150 for “Low Speed” category with no weight limit. That standard is good for all skydiving scenarios. The 3,000 pounds test load is strong enough for anything and force is a good base line for compatibility.
The current regulation for placarding (AS8015c/TSO C-23d) calls for “Average Peak Force.” Under AS8015b/TSO-C23c (the previous version), there is no way for a rigger to make the necessary determinations without help from the manufacturer doing some kind of retro placcarding as the requirement did not include force measurement. Fortunately, there are only a small number of systems/components certified under this rendition. Any component so certified would not be able to be used as there are no guidelines for compatibility.
Volume
An important criterion in determining compatibility is the volume of the canopy. The canopy has to fit into the container in such a manner as to not place undue stress on the system when packing and to be extracted by the pilot chute during deployment. The container manufacturer usually provides a volume chart of their systems stating what the volumes are for the various model sizes. Container volumes are somewhat nonsequitur; however, as container manufacturers derive their numbers in different ways. Some container manufacturers do not publish numbers per se; rather, they indicate a model designation that fits a size range of canopies.
The canopy manufacturer should provide the volumes of the canopy models. Measuring canopy volumes has proven to be an imprecise science as there are various methods that can be used. The most common method involves placing the canopy in a tubular chamber and compressing it with a standard amount of weight for a set time. The displaced volume is then measured. Figure 4-54 shows one such volume chamber. Slight differences in volume can be seen from chamber to chamber and canopy to canopy. These variances occur due to humidity at the time the test is conducted and due to variation in the bulk of the fabric that the canopy was built with. For example, sometimes a 150 square foot reserve is 312 cubic inch and sometimes that very same model, built using a different dye lot of fabric is 363 cubic inch. Canopy volume charts can be found on the Parachute Industry Association (PIA) website at www.pia. com and the Parachute Labs website at www.jumpshack. com. While some canopy manufacturers disagree with the resultant numbers, most container manufacturers and riggers agree that these independent test methods are useful in determining volume compatibility.
Deployment Type
In Chapter 2 of this handbook, Design and Construction, the different types of canopy deployment devices were described. In some instances, the container system needs to be of a specific configuration to accommodate a certain deployment device. An example of this would be where a round canopy utilizing a Type 1 configuration is packed into a pilot emergency parachute system. In this case, the pilot chute is compressed directly onto the floor of the container system. [Figure 4-55] This same canopy can be packed into a sport reserve container, but the sport rig has two internal or staging flaps that compress and hold the canopy in place and are locked together by the bridle. [Figure 4-56] The pilot chute is then packed on top of the internal flaps. The rigger needs to know and understand these differences to determine how the two components interface for compatibility.
Figure 4-54. Volume chamber.
Figure 4-55. Type 1 deployment in a pilot emergency rig.
Figure 4-56. Type 1 deployment in a sport piggyback.
Chapter Summary
This chapter focuses on main parachute packing techniques. The first rule is that the lines must be straight (no tangles, also known as “step throughs”). If the lines are straight and the slider is up (in square parachutes), the parachute will most likely open. The speed of the opening directly impacts the comfort or discomfort perceived by the jumper. Opening speed and orderliness is controlled by attenuation devices such as the slider, deployment bag, stow bands, or the diaper on a round parachute. Accoutrements, such as pilot chutes and bridles, must be checked frequently for wear that could affect their performance.
Rubber bands should be changed when they begin to exhibit small holes or ragged edges. Minor maintenance now prevents hard openings and major failures later. Learn to be observant of small details about the parachute system even when packing the main. Virtually every pack job should be an inspection. It does not have to be as thorough an inspection as you would perform at the 180-day inspection and recertification, but the packer should be vigilant for damage or things that do not look quite right.
Compatibility can be complex. When in doubt about which TSO a component was certified in, and whether it is compatible with another component in terms of opening force generated by the canopy versus strength of the harness, do not hesitate to call the manufacturer for guidance.
One of the most critical things the rigger must observe when servicing their customers rigs is reserve bag extraction force. When a customer brings his or her container for inspection and repack, reserve bag extraction force should be tested with the container closed. A good rule of thumb is that the extraction force should be the same as the weight of the bagged canopy. If excessive forces are encountered, call the manufacturer.