In in-flight fire is most pilots greatest fear, surpassing even a mid-air collision. Although relatively rare, the unique combination of combustible materials and ignition sources available in the typical personal airplane means an in-flight fire must be dealt with quickly and decisively. Doing so usually means disabling systems to deprive the fire of its fuel or ignition sources and employing a fire extinguisher to smother it. A quick landing, even if off-airport, may be necessary.

There are lots of extinguishers on the market, products both designed for aviation use and those marketed as “all-purpose” units. How do they differ? And-most important-how do they work on the materials found in a typical aircraft fire? To find out, we gathered up current examples of aviation-specific and all-purpose

extinguishers, lit a few fires and evaluated the results.

All the extinguishers we tested thwarted our efforts at arson. But we were surprised at how quickly we used up extinguishing agent. and the premium we had to pay for an extinguisher designed for the cockpit. We also discovered, however, that there are real differences between household, automotive and aviation-grade extinguishers.

Three things must exist for any fire to start: An ignition source, fuel (for the fire, not 100LL) and oxygen. These three items make the “fire triangle.” Remove any one of them and the fire either doesnt start or is extinguished. Our cockpits feature an abundance of materials capable of sustaining a fire. Carpeting, insulation, upholstery and paper charts are present in almost every airplane.

Since fuel lines often run through our cabin-routed through the fuel selector, flowing via a capillary line to a fuel pressure gauge, running down an A-post from the wing tanks-there’s another, much more combustible material nearby to get things burning. Our little experiment in pyromania demonstrated that when you combine even burn-tested fabric with some 100LL, an ignition source and the air flowing around and through an airborne airplane, youve got a problem.

Extinguisher Types

There are two basic portable fire extinguisher types on the market these days: Halon and dry chemical. Of the two, dry chemical types are less expensive and far easier to find: We snagged two Kidde-brand units from our local Wal-Mart for under $60. One was a typical residential unit, rated for use on wood/paper (type A), flammable liquids (type B) and electrical (type C) fires (see the sidebar on page 21 for an explanation of the different ratings). The other one was marketed for automobile use and rated for type B and C fires. The table (above right) summarizes the extinguishers we evaluated.

We also obtained three Halon extinguishers from H3R Aviation, which manufactures a wide range of aviation-specific extinguisher products, including portable units and those large, wheeled bottles you might find on your FBOs ramp. Two of our H3R units use blended Halon, a combination of Halon 1211 and 1301; the third uses Halon 1211. According to the company, Halon 1211 is a liquid streaming agent while 1301 a gaseous flooding agent. Because of Halons ability to react with a fire, it stops the ongoing chemical reaction without producing potentially damaging (i.e., corrosive) residues.