VLJ parachute study falls short

 - November 1, 2006, 7:22 AM

Don’t expect to see Ballistic Recovery Systems (BRS) parachutes on the first crop of very light jets. The Minnesota company, which makes the parachutes for the Cirrus line of piston singles, received a $600,000 grant in 2003 to study the possibility of such parachutes, but the two-year program did not yield a marketable product.

In fact, after some 100 drops and countless hours at computer screens, project chief engineer Tony Kasher told AIN, “We’re about 15 to 20 percent of the way there.” He said if any of the OEMs expressed interest, the company might move forward with the program, but he also said a viable product would be at least two years away, even with unlimited funding.

For parachute engineers, the dynamics of a system that could save a light jet are fascinating. Kasher called the two-year program, which concluded last September, encouraging. “We had some success,” he said.

VLJ Parachute Design Challenges

The biggest challenge is devising a system that will open the parachute progressively, since opening it abruptly at 350 knots would rip it apart. Any system that would be practical at that speed for an 8,000-pound airplane would need to be a multi-stage system, said Kasher, involving at least one drogue chute to slow and stabilize the jet before the main chute deploys.

Even after the drogue chute slows the airplane, a closed-loop system of sensors would be required to read the load on the canopy and “reef” the riser lines to control the inflation of the chute. A large part of the problem in establishing such an autonomous sensor system is that the canopy presents fluctuating loads to the sensor as it flutters in the slipstream. Kasher said, “It amounts to trying to control the shape of a rag that’s flapping through the air.”

Kasher said the NASA-funded study constituted a feasibility study, and he was encouraged by what he saw. But at present, BRS is undergoing a management restructuring and new president Larry Williams has other issues on his front burner, according to Kasher. “We’d need a wide array of drop tests to move forward,” he said, “and the weight of the system is also a matter of prime concern. Traditional woven materials are the most cost-effective, but using Mylar reinforced by Kevlar could result in weight savings that could be significant.”

Another possible source of interest in a high-speed BRS parachute is the military, said Kasher, though he said UAVs are generally not equipped with parachutes. He said when UAVs are flying over enemy territory the last thing the military wants is for them to float gently to Earth.