Deployment Initiators - A Comparative Study
by Jan Meyer
Deployment starts when the container is opened and a pilot chute is ejected into the airstream with a predetermined relative velocity with respect to a jumper. Two crucial functions of a deployment initiator are opening the container where the parachute is packed and ejecting the pilot chute with the appropriate relative velocity. Freely falling jumpers have a choice of three deployment initiators: a ripcord, throw-out or pull-out system. The throw-out and pull-out systems are also called hand deploys because the pilot chute is literally placed into the airstream by hand. Ripcord systems launch a pilot chute into the airstream by converting stored energy of a spring (potential energy) into energy of motion (kinetic energy).
A ripcord may be a steel cable with swaged pins that passes through a hole in a metal handle or a teflon cable mounted directly to a cylindrical handle. The handle is stowed in an elastic or velcro pocket on the main lift webbing. The cable passes through a protective housing that ends a few inches from the closing loop(s) (or cones) of the container. A pull on the ripcord handle is required to clear the pins or cable from the locking loop(s) and container grommet(s). After a pin or cable clears a container grommet, a compressed spring, sewn inside the pilot chute, is free to extend itself. As it does, it pushes the container flaps apart and then leaves the container with a relative upward velocity. This velocity allows the pilot chute the pass through the dead air space over a jumper's back and inflate several feet above the jumper. The inflated pilot chute acts as a "pull from above" to fully extend the bridle line and pull the bag from the container. The rest of deployment is standard.
A throw-out system has a pilot chute packed externally from the main container. A handle, generally a 2" cylindrical tube, is mounted to the apex of the pilot chute. As this handle is pulled, the pilot chute is extracted from a pouch. The pouch is most commonly located on the back of the right leg strap. Other locations include the bottom of the main container, the back of the container or on a belly band. The pilot chute does not inflate in the airstream next to the jumper until he lets the handle go because the handle is attached to the apex of the pilot chute. A jumper vigorously throws the pilot chute laterally away from him. The pilot chute rotates 180º and inflates. The inflated pilot chute now acts as a "pull from above" to extend the bridle line and extract a curved metal closing pin from the closing loop. The container opens when the pin clears the closing loop and container grommet. The bag is now free to be pulled from the container and the rest of the deployment sequence is standard.
A pull-out system has a pillow type handle fastened to the lower right-hand corner of the container. The handle is attached directly to a straight metallic pin via an 8-10" bridle line. This short bridle line passes through a grommet mounted at the base of the pilot chute. As the handle is pulled, the pin clears the closing loop and container grommet. The container is now open. The pilot chute is now extracted from the container as the handle is pulled laterally away from the body. The pilot chute rapidly inflates in the clear airstream next to the jumper because the handle is attached to the base of the pilot chute. The jumper vigorously throws the pilot chute to his side at arm's length. The pilot chute acts as a "pull from above", extends the bridle line as the jumper continues to fall away, and then extracts the bag from the container. The remainder of deployment is normal.
The three systems described above all work when they are properly routed and packed. The systems differ in packing and more importantly, potential malfunctions. All three systems are widely used today, but controversy surrounds the answer to "Which system is the best?" "Best" is a subjective decision based upon factors such as: specific application (student vs. experienced jumper), personal preference ("I want to be able to see the handle.") and potential failure modes (hard pull, floater, pilot-chute-in-tow). Advantages of a ripcord and spring loaded pilot chute system include the ease of pulling a readily visible handle and a very low stability requirement to ensure a good deployment. Most teflon cable ripcord systems have the plastic handle mounted near the hip area. This makes gear transitions easier for student jumpers. A disadvantage of this system occurs with AFF students. The main ripcord handle, a bright handle mounted near the student's right hip, is not visually accessible to a secondary jumpmaster. Packing is more difficult because of the additional "fussing" one must do while compressing the spring and closing the container. Hand deploy systems are easier to pack, since there is no spring to keep compressed while closing the container. Vigorous arm extension and handle release, while maintaining stablity, are crucial to the success of hand deploy systems. Pilot chute hesitations occur when a jumper does not throw the pilot chute laterally away from his body. A throw-out system may have a greater chance of continuing a normal deployment than a pull-out or ripcord system when a pilot chute hesitation occurs. This is because the container is still closed in the throw-out method. Pull-out and ripcord systems have open containers and there might be a small chance of the pilot chute and bridle line becoming fouled with the bag and suspension lines.
Totals: Hard Pulls and Floaters
Hard pull and floater malfunctions can happen to all 3 systems. Ripcords are usually the easiest to see because they are mounted to the front of the main lift webbing. Teflon cable ripcords and throw-out handles are still visible, but a jumper may unintentionally lose stability while pulling or groping for a handle. Ripcord floaters can be found by visually following the ripcord housing and grasping the ripcord cable with both hands and then pulling. The ripcord handle is at the end of the cable. In freefall, jumpers can tell another jumper he has a floating reserve ripcord by getting the jumper's attention, pointing to his own reserve handle and then the other jumper's reserve handle. Throw-out floaters are sometimes delibrately packed in by jumpers. Some jumpers leave several inches of the pilot chute apex dangling from the mouth of the pouch. During freefall the handle flaps violently about and may easily be snagged on aircraft and/or other jumpers. Pull-out handles are not visually accessible to a jumper. Some may consider this to be an advantage. One may be less likely to blindly grope for a handle than grope for a handle in sight and thus, less likely to lose track of time and altitude. Jumpers can watch the ground or their altimeter as they try for a pull-out handle, since no visual sighting is required. Floaters on pull-out systems may be found quickly following the container pack with your hand towards the pin. Total malfunctions can be packed in by misrouting the short bridle line around the base of the pilot chute. As the handle is pulled, tension is put on the pilot chute (still inside a closed container) and no tension is put on the pin. A proper pin check, given before donning the gear, can easily detect this total malfunction. Jumpers have been known to pull on lose horizontal adjuster or leg straps instead of a ripcord or pilot chute handle. Whether or not a handle is visually accessible is a matter of personal choice. If a handle cannot be found in two tries, it is suggested to immediately deploy the reserve parachute. The direction a jumper pulls on a handle is almost unimportant in ripcord and pull-out systems, but can be critically important in throw-out systems. Pilot chutes can be easily trapped inside pouches by an incorrect pull direction. Pouches mounted on belly bands have a very small range of appropriate pull angles, whereas pouches mounted on the back of the leg strap have pull angles coincident with the natural and comfortable pull from a jumper. Pouches should be made from Spandex and be sized to match the pilot chute size.
Premature container openings tend to be more hazardous for the throw-out system than either of the ripcord or pull-out systems. If the container opens inadvertantly in the ripcord or pull-out systems, then a normal deployment is most likely to occur because the pilot chute should catch air and inflate first. In a throw-out system, the bag and canopy can emerge from the container and flap above a jumper's back while the pilot chute remains stowed inside its pouch. This situation is almost a horseshoe malfunction. Jumpers may attempt to deploy the pilot chute and get a good canopy or at least a clean streamer to cut-a-way from. Premature openings can also occur in throw out systems when the pilot chute works its way free of its pouch. The pilot chute will normally catch air and initate a normal deployment for a surprized jumper.
The throw-out system has some additional malfunctions that do not have corresponding malfunctions in the ripcord and pull-out systems. A pilot chute in tow malfunction occurs when the pilot chute cannot pull the curved closing pin from the closing loop. Many of the causes of this malfunction can be detected in a pin check, prior to gearing up. Stitching and webbing, that fastens the closing pin to the bridle line, should be checked for airworthiness. A pilot chute in tow will occur if the closing pin breaks free from the bridle line. A closing loop that is too short can trap the closing pin. A straight closing pin in a throw-out system is highly susceptible to a pilot chute in tow. A nick or groove in the closing pin or container grommet may prevent the pin from being extracted. The bridle line may become entangled with a jumper's arm or may do a half hitch around the pilot chute as it rotates 180º just after a jumper lets the handle go. Waving off with pilot chute in hand is also another excellent way to wrap the bridle line around your arm. The most common way to get a pilot chute in tow is to put the gear on wrong. Twisted belly bands and leg straps looped through the horizontal adjuster strap are the most popular ways. A proper pin check after donning gear is crucial too. An extremely dangerous scenario arises when a jumper with a pilot chute in tow pulls the pin by hand, opening the container, and then realizes the bridle line is misrouted around part of the harness. He must now deploy his reserve into canopy and lines above his back. USPA recommends that jumpers maintain stablity and pull the reserve ripcord immediately if faced with a pilot chute in tow. Do not waste valuable time and altitude by pulling the cut-a-way handle.
Three modern systems used to initiate deployment have been explained in detail. All three systems work. All three systems can have hard pull, floater type high speed malfunctions and experience premature openings. The throw-out system can also experience a high speed pilot chute in tow malfunction. Jumpers are responsible for their own safety. No amount of rules and regulations can save a jumper with two packed-up parachutes at 1000 feet AGL. Only prior education and preparation about how equipment works, how equipment malfunctions and how to cure equipment failures in real time can save jumpers. Each jumper should determine the system he would prefer and is capable of using in a proper and safe manner.
Originally published in Sport Parachutist's Safety Journal V1, #1 May/June 1988.
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