Halon fire-extinguishing agents have been used for many years to protect valuable electronics, oil and gas production facilities, military systems, aircraft and other critical operations. The Army Corps of Engineers developed Halon (short for halogenated hydrocarbons) in 1948 as a less toxic but highly effective alternative to methyl bromide.

As good as Halon is at snuffing out fires, it also depletes the ozone layer at a rate of up to 16 times that of CFC-11, a common refrigerant. As a result, a 1994 international treaty banned Halon production in developed countries. (Although production has ceased, it is still legal to purchase and use recycled Halon, though it carries a tax of more than $40 per pound to do so.)

Despite the high costs of Halon– both monetary and environmental– manufacturers are still using it in aircraft engine fire-suppression systems for lack of a better alternative. In fact, FAA regulations currently require use of Halon in such systems.

But that could soon change, thanks to Eclipse Aviation’s development of an environmentally friendly fire-extinguishing agent dubbed PhostrEx. According to the company, PhostrEx certification fire testing is complete and the FAA and Environmental Protection Agency (EPA) have approved the resultant report. Further, the chemical meets the requirements of both the Montreal Protocol and the Clean Air Act.

Announcing the new fire-suppression system at EAA AirVenture in late July, Eclipse president and CEO Vern Raburn said, “We are committed to changing the status quo in aviation by pioneering and applying new technologies to aircraft design and manufacturing, and PhostrEx is another significant result of our efforts. Our customers will benefit from a dramatically improved fire-suppression system. On a global scale, due to our extensive testing and work with government agencies, including the FAA and EPA, the world finally has a replacement for Halon that is lighter, more effective, maintenance-free and environmentally friendly.”

The Albuquerque, N.M.-based company added that PhostrEx is much more potent than Halon. In fact, two teaspoons of PhostrEx are equivalent to 2.5 cups of Halon. As such, the Eclipse 500’s PhostrEx system weighs only 10 percent of a traditional Halon system.

Work on the PhostrEx fire-suppression system, which Eclipse has patented, started nearly three years ago when freelance scientist Dr. Peter Holland contacted the start-up manufacturer about his patented material, chemically known as phosphorous tribromide or PBr3. Eclipse engineers quickly set up a project to develop and certify the material as a fire suppressant on the Eclipse 500 very light jet.

PhostrEx Details

The PhostrEx system, Eclipse said, is much less complex than Halon systems and is designed to be maintenance-free for 10 years, versus every five years for Halon systems. Maintenance of the PhostrEx system requires only the replacement of a canister. Eclipse’s overall lifecycle costs for its fire-suppression system are projected to be about a tenth those of a Halon system.

In 2003, Eclipse initiated a development effort to prove the efficacy of PhostrEx by testing it in nearly 200 actual fires identical to those that might occur in aircraft engines. The company designed and built a fire test rig–an exact replica of the Eclipse’s Pratt & Whitney Canada PW610F engine and nacelle installation–to provide a platform to simulate engine-born fires. Eclipse claims it will be the only aircraft manufacturer to have an FAA-certified fire-suppression system proven through actual fire testing.

By combining computational fluid dynamics, in-flight testing and data from the fire test rig, Eclipse identified flame-holding regions and thus targeted agent distribution to them. This means the Eclipse 500’s PhostrEx system delivers fire-suppression agent only to where it’s needed, unlike inefficient traditional Halon systems that disperse their agent throughout the entire engine.

On the environmental front, PhostrEx has no ozone-depletion potential and does not contribute to global warming. PhostrEx works in less than one-tenth of a second when released from its hermetically sealed canister. The chemical combines with moisture in the air and quickly becomes inert, according to Eclipse.

The agent is incapable of drifting up to the stratosphere, where ozone depletion could occur, because of this rapid reaction with moisture. In a fire, PhostrEx decomposes 1,000 times more rapidly than Halon and undergoes three sequential losses of bromine atoms, which catalyze suppression of the fire.

Eclipse said it has invested in tools and methodologies that will allow PhostrEx to be applied to the existing worldwide fleet of about 500,000 aircraft, as well as to new aircraft production. According to Raburn, a PhostrEx cartridge can be swapped with a Halon cartridge with no other engine fire-suppression system modifications.

To capitalize on its patented system, the company’s board of directors has authorized Eclipse to explore the establishment of a separate company to market PhostrEx in other aviation and land-based fire-suppression applications. Raburn said the aviation fire-suppression business alone is a $2 billion to $3 billion industry a year.