The Helicopter’s Role in Fighting Wildland Fires…
As a helicopter enthusiast, I have to confess that part of me loves fire season. When smoke clouds billow into the sky and haze chokes the valley, my ears are primed for the thump of rotor blades.
A fire two summers ago that forced the evacuation of my neighborhood also spawned a helibase less than two miles from my house. I could climb up the hill and see two Sikorsky S61 Sea Kings, several Bell 205′s, a Bell 206 L4 and a 407, and my favorite, a Sikorsky S58T. Due to the close proximity of the Missoula Airport, the Erickson Sky Crane was staged there instead of the helibase. The airport is also the home base for Neptune Aviation, an air tanker company that flies vintage Lockheed P2V Neptune maritime patrol aircraft converted to drop up to 2,700 U.S. gallons (10,220 liters) of flame retardant. Considering that the fire was within 10 miles of a base full of air tankers, each capable of carrying a load of retardant weighing more than the largest helicopters at the helibase, why bring in helicopters at all? Obviously helicopters can do a lot more at fires than burn money and give overweight, middle-aged men an excuse to wear Nomex® flight suits!
Fixed-wing air tankers are very effective at laying down a long line of retardant along a fire’s flanks to slow the fire’s lateral spread. Hand crews or bulldozers usually follow up by digging a fire break, or fire-line, along the retardant drops. Rarely is retardant dropped at the “head” of the fire where the flame front is greatest.
Fire speed and intensity can overwhelm the drop and make accurate drops difficult. Smaller, more agile “lead planes” are deployed to direct the air tanker’s drops. Once an air tanker drops its load, it must return to the air base to reload and refuel. Depending on the distance to the fire and the size of the tanker, this could take a while despite the air tanker’s speed advantage over helicopters.
Smaller, single-engine air tankers called SEAT’s, can carry as much as 800 gal. (3,030 l.) of fire retardant and can be deployed much closer to fires at smaller runways, preferably within 50 miles (80 km.).
Helicopters have the advantage of proximity to their water or retardant sources. With their buckets and snorkels, helicopters can take on water in nearby lakes, ponds, and rivers, and from portable “dip tanks” filled by pumps. This lowers the “cycle” time from pickup to drop.
Helicopters can drop water at the head of the fire to slow it down, or on spot-fires along the fire’s flanks to hold the fire-line. The smaller helicopters assist the ground crews to attack spot fires and “mop up” burned areas along fire-lines.
Larger helicopters like Bell 205′s and UH 60 Firehawks work farther from the ground crews because the rotor downwash can create falling tree hazards. The largest helicopters are often assigned a section of fire-line all to themselves. These are usually in the most difficult, inaccessible, or hazardous terrain.
Firefighting helicopters also perform traditional roles such as crew transport, logistical support, and reconnaissance. Advanced thermal imaging cameras combined with global positioning systems are mounted on the smaller helicopters to locate spot fires and hidden “hot spots,” and accurately map out fire boundaries.
Ironically, helicopters are also quite effective at lighting fires when needed, such as for back-burns and controlled prescribed fire. An onboard delayed aerial ignition device, or DAID, injects potassium permanganate-filled ping-pong balls with ethylene glycol and dispenses them out of the helicopter. The ensuing chemical reaction ignites the ping pong balls on the ground. Helitorches are drip torches slung on long lines that drip burning fuel. These are much more precise aerial ignition methods than dropping napalm bombs out of screaming F4 Phantom Jets.
On the day that my neighborhood was evacuated, smoke prevented air tankers from making drops. Only one Bell 205 was available, but it did its best making bucket drops and back-burning firebreaks dug by bulldozers. Fortunately, our neighborhood was spared thanks to the bravery of all of the firefighters.