Research group studies airbags for helicopters

 - February 7, 2007, 8:37 AM

European-funded research project Helisafe, led by Marignane, France-based Eurocopter, is studying airbags and harnesses as a possible means of enhancing the safety of helicopter occupants. A Helisafe engineer emphasized that the project is still in the research stage, so practical applications of the airbags and harnesses are probably several years away.

A researcher working on the Helisafe project told AIN that future body protection devices may work in three steps. In the first step, the occupant’s body will be pinned to the seat. Second, load limiters will control the body’s forward movement while airbags will cushion the end of the body’s movement.

The three-step crash-protection process must begin with an active harness that pins the body on the seat. So-called pretensioning devices give the body the necessary position for the airbag to operate efficiently. Current, passive harnesses are not always as efficient as they should be in body protection, as the occupant can slip under the harnesses, said Pierre Prudhomme-Lacroix, head of airframe components at Eurocopter’s stress office.

Airbags may play in helicopters the same role that they play in cars. In current rotorcraft, the occupants’ bodies can suffer from shocks–either on the head, arms, legs or feet. As a result, researchers are interested in the idea of fitting airbags in various places in the cabin.

Ensuring that airbags are efficient is more complex in a helicopter than in a car. First, crash scenarios are more varied and simulations and tests are more sophisticated for helicopters. Second, integration of the airbag system is more difficult in a helicopter because the pilot must be able to continue to fly the helicopter even if an airbag inflates unnecessarily. Therefore, researchers have yet to determine where airbags should be installed. Possible locations include the upper part of the flight panel, lateral frames or even flight controls.

Another obstacle to the installation of airbags in helicopters is the small amount of data available about helicopter crashes. “Helicopters have neither cockpit voice recorders nor flight data recorders,” another researcher added. Eurocopter provided some statistics about helicopter accidents. According to the company, 40 percent of helicopter accidents involve injuries to the occupants, while there is no significant deformation to the helicopter. Certification standards stipulate that a helicopter must survive an impact at a vertical velocity component of approximately 20 feet per second without damage.

The research team will continue to conduct trials on testbeds designed for car crash-test dummies. It has also developed special dummies to integrate vertical acceleration measurement. During the first phase of Helisafe, tests with one frontal airbag yielded satisfactory results, the researcher told AIN.

“In the second phase (which began in March and will run through March 2007), we will try to go more deeply into crash scenarios, airbag integration, inflation triggering, leg protection and, last but not least, we will endeavor to cover a wide spectrum of the population,” he said. In other words, the systems must work with the tall, small, slim and not so slim.

Inflation triggering can be tricky, as temperature variations or electromagnetic effects must not influence the activation of the system. “We have to locate the sensors in the right places so as to be able to order inflation at the right time,” the researcher pointed out. Crash scenarios will include lateral velocity and rollover.

A full-size test is pegged “in the coming months” with a complete Bell UH-1 Huey airframe, a pilot dummy and a passenger dummy, the latter sitting on a side seat in the cabin. The trial will involve no airbag, though researchers hope to conduct a full-size test with airbags in the future. Vertical and longitudinal accelerations will be applied. Engineers expect the measurements to validate their computation models.