Instrumentation of Paratroopers and Large Parachute Pallet Loads

Joseph M.Strus, Earl G.Blackwell, Christian A.Gellrich, Michael R.Kirkpatrick, and James W.Sinko

Abstract:	The US Army Operational Test Command, Airborne & Special Operations Test Directorate (ABNSOTD) needed a convenient instrumentation system to verify parachuted pallet rigging configuration designs prior to use by operational forces. They also needed to instrument personnel being dropped via parachute to determine why dangerous swinging oscillations occur and to determine how variations of weight and wind affect the landing positions. For the paratrooper unit, the dynamics of the exit from the aircraft were not a major concern. Because of the limited space for instrumentation, a decision was made to limit the instrumentation to a small helmet-mounted antenna, a GPS receiver, and a custom-built data logger. For the paratroopers, swinging oscillations were detected by examining variations in the GPS velocity. In order for the GPS to lock on to the SV signals quickly, the receiver was fed reradiated signals while in the aircraft. For the large cargo pallets, the attitude changes during aircraft exit are of major interest, and instrumentation size and weight are only a minor concern. Thus, a tactical grade inertial measurement unit (IMU) was used in conjunction with the GPS to obtain a complete position and attitude profile. All processing was post-mission and a forward/backward-smoothing filter was used for the GPS data as some GPS track interrupt was expected on exit from the aircraft. Processing of the IMU data was complicated by large pitch changes (pallets frequently rotate beyond vertical when exiting), accelerations exceeding 20 g’s, and the need for gyro alignment transfer. An embedded processor was used to record the data and synchronize the IMU data to GPS time. A number of preliminary tests were made to help choose the components to use and to develop the processing algorithms. These included static tests in which the receiver was switched among spaced antennas (to simulate going from the reradiator inside the airplane to direct reception outside the airplane), dynamic tests on the freeway (including overpass outages), and tests on a motorcross track. It was found that there were significant differences among different brands of receivers in reacquiring GPS signals after exiting the aircraft. The final tests were conducted from military cargo aircraft.
Published in:	Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002) September 24 - 27, 2002 Oregon Convention Center Portland, OR
Pages:	2457 - 2465
Cite this article:	M.Strus, Joseph, G.Blackwell, Earl, A.Gellrich, Christian, R.Kirkpatrick, Michael, W.Sinko, James, "Instrumentation of Paratroopers and Large Parachute Pallet Loads," Proceedings of the 15th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GPS 2002), Portland, OR, September 2002, pp. 2457-2465.
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