Green replacement for Halon close to FAA approval

Very-light-jet pioneer Eclipse Aviation is claiming a breakthrough in fire-suppression technology with development of the first commercially viable replacement for ozone-depleting Halon. Designed for the Eclipse 500 jet, the patented PhostrEx fire-suppression system has been approved by the US Environmental Protection Agency and is close to certification by the US Federal Aviation Administration.

PhostrEx works to chemically shut down a fire in less than a tenth of a second, then combines rapidly with moisture in the air to become inert “before it can be transported to the stratosphere where ozone depletion could occur”, says Eclipse. Because the material is far more potent than Halon, much less is needed.

PhostrEx works by releasing bromine atoms that catalyse a recombination of reactive chemicals in the flame, shutting off the heat release and extinguishing the fire. While Halon releases the bromine reluctantly, PhostrEx decomposes about 1,000 times more rapidly in a fire. “Two teaspoons of PhostrEx are equivalent to two and a half cups of Halon,” says Eclipse.

The fire-suppression agent is also targeted at flame-holding regions within the powerplant, and airflow through the nacelle used to transport agent to these zones more effectively than the current approach of flooding the engine compartment. These regions and airflows were identified using computational fluid dynamics and a fire test rig providing a high-fidelity simulation of the engine within the nacelle.

In almost 200 fire tests with various “worst case” combinations of fuel and air flows, fire locations, temperatures and flight conditions “we were always able to extinguish a fire”, says Eclipse. Fire testing is complete, and the report approved by the FAA, with one flight test to validate airflows within the nacelle required for final certification, says Eclipse chief executive Vern Raburn.

Although PhostrEx has been developed for the Eclipse 500, Raburn sees potential for wider application. The aviation industry was granted a waiver to the 1987 Montreal protocol banning Halon, but production was halted in 1994 and stockpiles are being gradually depleted. The waiver was granted “until there is an approved and certificated substitute for Halon”, with PhostrEx being the first viable alternative, he says.


Source: Flight International