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Reserve back-up

Automatic opening capability to give paratroopers extra assurance

Four seconds after exiting a military airplane on a low-altitude jump, paratroopers are trained to pull the handle on their reserve parachute if they don’t feel the opening shock of their main parachute.

Paratroopers on low-altitude jumps currently have no automatic opening capability for their reserve parachutes. A system is under development.

Sometimes the reserve is not opened when it’s needed, which is why engineers in the Airdrop Technology Team at the U.S. Army Soldier Systems Center (Natick) are working on a device called the Parachute Reserve Automatic Opening Capability.

The Army vision includes maintaining the airborne infantry as a strategic deterrent and as an early entry force. Jump-related casualties lessen combat effectiveness. Statistics from the Army Safety Center show that between 1974-1999 almost one-third of airborne fatalities could have been prevented if the reserve parachute had an automatic opening capability, said Bill Millette, project officer.

“This device is being designed to address total malfunctions of the main parachute,” he said, although effectiveness during partial malfunctions may come later. “A broken static line is the primary failure.”

Automatic reserve opening capability has been available for high altitude, low opening jumpers based on a system that uses barometric pressure. If the paratroopers descend to a certain altitude at a speed higher than the main travels, the reserve deploys. The same system is impractical with aircraft dropping paratroopers at about 500 feet.

“That takes way too much time for low-altitude jumps,” Millette said. “An incapacitated jumper can’t react to a malfunction, and a disoriented jumper has very little time to react. We anticipate training-related fatalities caused by broken static lines or total canopy failures will be eliminated.”

The project began in 1999 as a Small Business Innovation Research program with Cybernet Systems, Inc. in Ann Arbor, Mich., and transitioned in October to a Science and Technology Objective program scheduled through 2005 that may also involve other manufacturers.

The current device houses a pressure sensor and three accelerometers inside an aluminum case about the size of a camera body. A hole the diameter of a pencil senses the blast of air a jumper experiences while exiting the aircraft and starts to count. Accelerometers simultaneously record movement in three axes and calculate a total velocity measurement. The battery-powered automatic opener is connected to a small explosive charge to push out the handle if the system senses that an automatic activation is required.

The current device houses a pressure sensor and three accelerometers inside an aluminum case about the size of a camera body.

“It’s intended to provide enough information to determine whether the reserve should be activated. If the system doesn’t sense the tug of the main parachute within four seconds, it will activate the reserve,” Millette said, adding that soldiers will still be able to actively open the reserve.

The Cybernet system uses low-cost accelerometers that were developed for automobile airbags, and the industry has posted a solid reliability record with the microelectromechanical systems, according to Millette.

Still, challenges remain. One capability yet to be handled is how to ensure that the device will not activate during door checks by jumpmasters, since these checks repeatedly expose them to rushing air before leaving the aircraft.

Static line jumps from helicopters are another area that will require attention because the slower airspeed used during helicopter jumps requires paratroopers to count two extra seconds before deciding whether to activate their reserve.

The battery-powered automatic opener is connected to a small explosive charge to push out the handle if the system senses that an automatic activation is required.

Engineers are considering incorporating extra instrumentation into the system, although Millette said the usefulness of such devices must be balanced against their cost. One desirable device under consideration is a gyroscope, which measures rotation of the jumper.

“You probably don’t need a gyroscope in the system if you’re only concerned about responding properly to total malfunctions, such as when the static line breaks,” he said. “But if you’re looking at more complex situations, such as a towed jumper, a gyroscope may be helpful. You wouldn’t want the system to activate the reserve in that situation.”

The system is currently designed for use with the Modified Improved Reserve Parachute System, but the activation mechanism could be modified to work with reserve parachutes that use soft loops.

Initial testing consisted of data-gathering drops conducted with mannequins at Yuma Proving Grounds, Ariz. More recently, soldiers and airborne-qualified Natick employees wore the devices to gather data during ramp jumps from CH-47 helicopters and C-130 aircraft. Human testing gathered useful data for the system developer because people are flexible and respond differently to forces, said Millette.

Since the automatic opener records data, it can act as a paratrooper’s “black box,” which has interested the Army Safety Office as a tool to investigate paratrooper accidents.

“We hope it doesn’t get to the point where the Safety Office uses it during a fatality investigation because we expect it to work properly,” Millette said. “The device also has the potential to be used to provide jumpers with feedback on their exit technique.”

He said one goal is to integrate the automatic reserve opener as a pre-planned product improvement into the future Advanced Tactical Parachute System. It’s possible that continued development could lead to the product being trimmed down to the size of a chip.

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