New Backup Coming for Four-Second Parachute Countdown
By Curt Biberdorf
Special to American Forces Press Service
NATICK, Mass., March 26, 2002 Paratroopers making low- altitude jumps are trained to pull the reserve chute ripcord if they don't feel the main chute open four seconds after exiting their plane.
Sometimes the reserve parachute is not opened when it's needed. That's why engineers at the U.S. Army Soldier Systems Center here are working on an automatic reserve parachute opener.
The Army vision includes maintaining the airborne infantry as an early entry force. Jump-related casualties lessen combat effectiveness. Army Safety Center statistics show that an automatic reserve parachute opener might have prevented almost one-third of airborne fatalities between 1974 and 1999, project officer Bill Millette said.
"This device is being designed to address total malfunctions of the main parachute. A broken static line is the primary failure," he said. "We anticipate training-related fatalities caused by broken static lines or total canopy failures will be eliminated.
Effectiveness during partial malfunctions may come later, he added.
Automatic reserve opening capability has been available, but for high-altitude, low-opening jumpers. Their system uses barometric pressure. If the paratroopers descend to a certain altitude at a higher speed than the main chute travels, the reserve deploys. That system is impractical for paratroopers at 500 feet -- their jump time's too short.
"(It) 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."
The automatic opener project began in 1999 as a Small Business Innovation Research program with Cybernet Systems Inc. of Ann Arbor, Mich. It evolved in October to a Science and Technology Objective program scheduled through 2005 that may also involve other manufacturers.
The current prototype fits inside an aluminum case about the size of a camera body and houses a pressure sensor and three accelerometers . Through a pencil-sized hole in the case, the sensor measures the blast of air a jumper experiences while exiting the aircraft and it starts a countdown. The accelerometers record the jumper's movement in three axes and compute a total velocity measurement.
"If the system doesn't sense the tug of the main parachute within four seconds, it will activate the reserve," Millette said. In that case, a small explosive charge connected to the battery-powered opener "pulls" the reserve handle. Jumpers will still be able to open the reserve manually.
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 components, according to Millette. Still, challenges remain. One, he said, is preventing false countdowns caused by door checks. Jumpmasters inspect their troopers' rigs at the door to ensure they're squared away, but as short as the checks are the delay exposes jumpers and sensors to rushing air, he noted.
Static-line jumps from helicopters are another area that will require attention, because the slower speeds used during helicopter jumps require troopers to count two extra seconds before deciding whether to activate their reserve.
Engineers are considering adding more instruments into the system, but Millette said their usefulness must be balanced against cost. One device under consideration is a gyroscope, which would measure the jumper's rotation.
"You probably don't need a gyroscope if you're only concerned about responding properly to total malfunctions, such as 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 it could be modified to work with others, he said.
Initial testing consisted of data-gathering mannequin drops at Yuma Proving Ground, Ariz. More recently, soldiers and airborne- qualified Natick employees wore them to gather data during jumps from CH-47 helicopters and C-130 aircraft.
Since the opener records data, it could be used as a paratrooper's "black box," Millette said. Its possible use as a tool for accident investigators has the interest of the Army Safety Office.
"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 another goal is to integrate the automatic reserve opener as a 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, he noted.
(Curt Biberdorf works in the Public Affairs Office of the Army Soldier Systems Center in Natick, Mass.)