Hang Gliding – Articles
The Ballistic Controversy
By Betty Rothman
Once upon a time purchasing a parachute system for your hang glider was easy. You called your local dealer and said, "I need a parachute." The dealer said, "okay" and you bought a parachute. Today the hang glider pilot is required to make decisions not only about the size shape and performance of his/her hang glider parachute but also about the method of deployment.
The purpose of this article is to help pilots make more informed decisions when considering ballistically deployed or hand thrown hang glider parachute deployment systems. This article will address the deployment method regardless of parachute style or type. Remember, there are tradeoffs in everything you do. As a pilot it is your job to decide which system best suits your flying style and environment.
The term "ballistic" refers to pyrotechnic and air rockets. Pyrotechnic rockets are those which burn a fuel while air rockets use pressurized air to produce thrust.
Some of the early problems of ballistic systems revolved around the manufacturersÕ choice of ballistic device itself. Rockets stored energy with great efficiency, but getting the thrust duration of the rocket right was a problem. Too much thrust at the end of full canopy extension could cause the burning rocket to change direction and become unpredictable. With too little thrust, the rocket would not pull the parachute from the container properly and reach full canopy extension. Too much thrust could pull the parachute out of the container too fast and cause burning of the lines or canopy by the friction of nylon rubbing against nylon. In addition there was always the risk of burning the parachute material. Manufacturers wanted just enough thrust to get the parachute to full extension with out burning the canopy. The thrust produced by the solid fuel rockets today seems to balance both the mass of the parachute as well as the amount of burn time.
Other early design issues included how the rocket would be carried by the pilot, should it be mounted on the hang glider frame or the harness, how the rocket was to be launched, should the manufacturer use a spring loaded trigger with a firing pin or some other arrangement, how the rocket should be attached to the parachute, how the parachute should be pulled from its container, where to mount the parachute and the launch tube, where the handle should be mounted, and a host of other considerations. Later problems included how to best mount the launch tube so it will not get caught up on side wires, how to build a safety that is easy to open if the pilot forgets to undo the safety before launch, and, always, how to minimize the number of pilot errors.
With time many of these questions have been answered. Continued analysis of how hang gliders break and how the wreckage behaves form a basis of continued research and development the field of parachutes. (It is interesting to note that 10 years ago hang gliders seemed more prone to tumbling to the ground while more recently broken hang gliders seem to spin to the ground. Some broken hang gliders have been known to come down slower than the parachute packed in its deployment bag.)
Pros and Cons of Ballistic Deployment Systems
The pros of the ballistically deployed parachute systems are obvious. Foremost, assuming an uneventful deployment, the ballistic system will give you a very fast deployment. The pyrotechnic rockets give a continuous thrust of about 50 lbs. for a duration of about one second. The air system initially accelerates the rocket with 60 to 75 pounds of thrust, which then drops off as the parachutes travels to full stretch with its own momentum. Since speed is directly related to altitude, you can successfully deploy your ballistic parachute at a much lower altitude than if you were using a conventional hand thrown deployment method. Since the rocket on a pyrotechnic system provides the parachute with a constant state of tension throughout the deployment, an orderly sequence of deployment is maintained while the parachute is inflating. The chances for an asymmetrical deployment are much less with constant tension. You get the same advantages with the air system although the thrust decreases as the parachute reaches full extension.
The less time it takes for parachute inflation the less likely your bridle or lines are to wrap up in a spinning or tumbling hang glider. If your hang glider is broken a ballistic system needs only a narrow channel of clear space for the rocket and parachute to get through the wreckage. A conventional hand thrown deployment bag needs a wider opening. Just prior to deployment the hang glider pilot need think of only two things when using a ballistically deployed system: point and pull.
The cons of the ballistically deployed parachute system deserve more attention. First is the increased complexity of the system. As with any mechanical devise, the more complex it is the greater the chance that something can go wrong. The cost of purchasing a ballistic deployment system ($599-750) may be another consideration. Maintaining the system is definitely more reasonable. A current BRS rocket on a 6-year maintenance schedule costs about $175 to overhaul. That translates into $1.22 a month cumulative maintenance plus the regular repack charges that occur with all common parachute systems (non-vacuum packed).
If you travel on airlines with your harness and pyrotechnic rocket, you may have difficulty bringing a "Class-C Explosive" aboard. The air rocket can be depressurized before your flight then refilled with a scuba tank when you reach your destination.
The extra weight (1.5 lbs. to 2.5 lbs.) of a ballistic system may not play as big of a role in considering disadvantages as it once did. The hang gliders today seem to be able to carry "weight" much better. In addition the newest "high tech" parachute designs are bringing more weight down at a much slower rate of descent than those of the previous generation. If, however, you have a tendency to land away from roads and retrieval, fly off of a shallow launch, or you need to hike into your flying site, you may want to argue this point.
Mounting location of the ballistic rocket is critical both in terms of locating the deployment handle in a easy to reach spot and directing the launch tube to fire the rocket in the desired direction (preferably not at your own body). You should be able to reach your deployment handle with either hand. As of last year, BRS has decided that mounting is so important they want to factory install all of their systems.
Once you have your ballistic system mounted you must then consider how you plan to aim it in the event of an emergency. Moving your body to aim your rocket may be difficult especially if your glider is broken and you cannot find anything on which to hold. If you do not get a clear shot and your rocket or parachute gets hung up on the wreckage, a ballistically deployed system can be very difficult if not impossible to reel back in and hand throw.
If your system does not fire your only option short of having a second parachute or a ballistic system that can be hand thrown, is to cut the rocket connector line and pull the parachute out of the container by hand in an attempt to deploy it by hand. This would be very difficult at best.
In addition a system that is shooting a raw canopy through the wreckage or is storing the parachute in close proximity to Velcro hook has a greater tendency for parachute damage than that which uses a deployment bag or other protective sleeve arrangement.
If you have accidentally fired your rocket in the same direction you are falling the extra thrust can pull you closer to the ground and it will take even more time for you and your hang glider to fall below your parachute in order for it to inflate.
Finally, the ballistic systems require a much higher degree of care by the pilot than hand deployed. First, the pilot must remember to undo the safety just before launch and immediately attach the safety right after landing. The consequences of a woofo helping you and grabbing the wrong handle, or a child who just wants to see what happens when he pulls the handle can be disastrous. The chance of an accidental deployment during a bad landing or crash is increased with ballistic systems. The pyrotechnic rockets can give off enough heat to cause injury. All ballistic systems should be treated like a loaded gun. They need to be kept locked away from children and handled with care. Launch tubes made from aluminum tubing are not impervious. Careless handling can dent the launch tube and interfere with a proper deployment.
The Internal AIR System by Second Chantz has really addressed many of the potential problems associated with some side mounted ballistic systems. It can ballistically deploy or hand deploy the same parachute. Both deployment handles are in easy to reach visible locations. The launch tube is embedded in the parachute container on the chest exposing only about 5 "of launch tube from the front bottom corner of the parachute container and making it very difficult to get caught on the side wires. The problem inherent with this arrangement is that you now have a hard cylinder diagonal across your chest so in the event of a hard belly landing.
For all the things that can go wrong, the ballistically deployed parachute systems remain superior in doing the one thing that can save your life... getting your parachute out fast!
Pros and Cons of Hand Deployed Parachute Systems
The pros of a hand deployed parachute system packed in a deployment bag include the pilotÕs ability to throw the parachute in the best direction given her/his particular situation. The pilot is not dependent on positioning the launch tube by rotating his/her body but can use his /her natural instincts to throw the parachute in any number of different directions.
There is no extra weight of a rocket.
You have a protective "pillow" on your chest in the event of a hard belly landing on jagged rocks. (At least 6 pilots have attributed no injuries during crash landings to having a parachute protect their chest).
The parachute and lines are protected by the deployment bag from sharp edges as it is thrown through the wreckage. If the parachute hits the sail or other objects it may be able to bounce off without disrupting the deployment sequence. If it gets caught in the wreckage the pilot may be able to reel the parachute back in and throw it again.
On the down side, the pilot must have the presence of mind and physical ability to hand throw into clear air (usually the harder the better). This means that the pilot must make more decisions about when and where to throw. If you wait too long, the spin may gain too much momentum to allow you a clear throw.
The amount of time it takes for full bridle, line, canopy extension is dependent on the amount of force with which the deployment bag was thrown as well as the direction of throw relative to the specific situation of the pilot. You must be able to forcefully throw the deployment bag.
A hand thrown system needs a wider channel of clear air through the wreckage than the ballistic systems require.
The biggest negative associated with the hand deployed system is the amount of time and energy it takes to throw the parachute to full canopy extension.
Learning from Real Life Situations
As with any life-saving devise, the importance of following manufacturersÕ guidelines cannot be over emphasized. Although rockets enjoy a 99.9% reliability rating (when using the current NASA testing procedures) that statistic does not reflect problems with the rigging, the trigger mechanism, the mounting of the system, or the improper use of the ballistic device.
The importance of following ridged packing guideline is best illustrated by one pilot who needed to use his ballistic system the day after he had repacked his parachute. The pilot, Ken, had s-folded his parachute and stacked his lines in an unconventional manner in a parachute container mounted on the side of his harness. During the incident he was easily able to locate and pull his deployment handle. His legs were out of his harness and he was in a balled up position when he fired his system. The projectile glanced off his leg (it did not leave a mark!) then continued to get caught in the wreckage. The pilot contributes part of this failure to an improperly packed parachute that may have hampered the amount of force the rocket needed to pull out the parachute. Fortunately Ken was able to ride the glider to the ground. He suffered whiplash.
The importance of not "improving the system" without consulting the manufacturer can be illustrated by GeorgeÕs experience. George felt that he really wanted easy access to his ballistic deployment handle. He mounted his side ballistic canister further towards his head than normal then redirected his deployment handle from the top of the canister in a straight line towards his shoulder and secured it with Velcro. In this way he could easily grasp the handle with either hand. What he did not consider is that in the event of a bad landing, the brush could also grab the handle and fire the rocket. That is exactly what happened. George reports that he was very surprised at how quiet the rocket was when it fired. The projectile left a 1" hole in his harness while the after burners burned another 5 to 6 inches of harness. The rocket buried itself 6 to 8 inches into the soft sand. It pulled the parachute out of his container and through the hole in his harness. Remarkably the parachute was not damaged. Had George talked to the manufacturer about the routing he may have avoided this problem with other precautions.
The importance of remembering to unlock the system was demonstrated when Eric was unable to find his deployment handle after tumbling from a blown loop attempt. It seems that he had not adequately released the handle cover before launch. Anyone could just as easily forget to unclip the safety handle restraint. Luckily ErikÕs leading edge took the brunt of his impact with the ground.
Proper instillation of any system, be it hand deployed or ballistically deployed, is imperative. The pilot who deployed his system with his side pocket unzipped was very surprised to find the projectile getting snagged on the open zipper. We will never know if the deployment would have been normal had his pocket been zipped. What we do know is that it is to the customers benefit to send a picture of the installed system straight to the manufacturer so they can do a final inspection regardless of who does the actual instillation.
The importance of careful inspection and maintenance of any ballistic system was demonstrated by a NY pilot who blew an aerobatics maneuver in Telluride. Apparently he did not notice that the nut attaching the handle (a location difficult to inspect) to his firing mechanism had loosened. When he grabbed his handle he pulled it right out of the launch tube without firing the rocket. Fortunately he had a back up hand thrown parachute that saved him.
Then there was Jacque who fired his pyrotechnic rocket to find that the rocket somehow wound up sizzling on his back. It burned through his down jacket, sweater, shirt and left 2nd degree burns on the back of his shoulder. The parachute never left the container although reports indicate that, when pulled, it did easily snake out of the container.
These are just a few illustrations of problems experienced by improper use maintenance, or performance of ballistic systems. Hand deployed parachute users have not been without their own horror stories. Consider the pilot who was spinning with such centrifugal force that he could not reach the handle, or the pilot whose parachute fell below him and ultimately opened pinning him to the sail, or the pilot without safety locks on his parachute system that deployed when he didnÕt want to. Most recent as of this writing was OrinÕs experience. After tumbling his glider, Orin remembers that he could not move his right arm. He does not remember throwing his chute but he does remember watching the parachute still in the deployment bag falling below him as his was spinning to the ground with tremendous force.
In conclusion, there are many factors to consider when choosing the method of parachute deployment that is best for you. Weight, bulk, and cost are minor considerations compared to how much time you spend low to the ground, your aerobatic desires, and usual flying environment.
In researching this article I found that each method of deployment was superior under different situations. If the pilot had an uneventful deployment, ballistically deployed chutes were far better in getting the parachute out as quickly as possible. The number and types of things that can go wrong, however, are far greater with a ballistic system than with the traditional hand deployed parachute. To complicate the "ballistic controversy" even further, the pilot must now recognize that hang glider failures resulting in severe spins greatly affects the performance of the parachute even once it is out.
The bottom line is that no matter what kind of parachute deployment system you have, you must treat it with care. You must treat it as if your life depends on it because it very well may.
A special thanks to Dan Johnson, Paul Thompson, Rob Kells, Gary Douris and John Dunham for their help in researching this article.