Presented at the 15th AIAA Aerodynamic Decelerator Systems Conference, Toulouse, France, June 9-11, 1999
Our technique involves using solid state differential pressure sensors embedded in the cells and linked via flexible tubing to selected ports (figure 1). Power and data signals are transmitted via magnet wire which is finger-trapped in an additional (non-load bearing) Dacron suspension line attached to the underside of the canopy and to amplifiers taped on the harness risers. As shown in reference 1, this arrangement is sturdy enough to have survived dozens of tight packings and violent deployments without any major breaks. (Photos of the canopy during inflation and the canopy in flight show some of the above mentioned configurations.)
Over the years, BLM smokejumpers have used two ram-air parachutes, namely the Goliath which is a 360 square foot seven cell design manufactured by Para-Flite Inc., and the Trilobe, a 320 ft2 seven cell parafoil designed by Quantum Parachutes. Compared to most ram-air parachutes in the market today (including the Goliath), the Trilobe features two oversized quarter-span cells that flatten the wing at mid-span. Given this difference in cell design between two such canopies that are otherwise similar, it will be interesting to see whether each display a different pressurization "signature" during inflation.
The paper will discuss the results obtained so far, including:
1) the pressure signatures of bag strip, early cell pressurization and slider descent stages for the Goliath and the Trilobe (see figure 2);
2) the value of the maximum pressure differentials experienced;
3) the time delays and spatial correlations of pressurization between selected pairs of ports;
2. Garrard, W. L., Tezduyar, T. E., Aliabadi, S. K., Kalro, V., Luker, J. and Mittal, S. ; "Inflation Analysis of Ram Air Inflated Gliding Parachutes; AIAA-95-1565.
3. Potvin, J. ; "A Simple Description of Airflow Characteristics Inside an Unfolding Parachute". December 1997; submitted for publication.
4. Montanez, R., Potvin, J. and Peek, G.; "Wind Tunnel Investigation of Ram-Air Parachute Cell Pressurization"; AIAA-97-1524.