Airtanker - Aerial Firefighting
Aerial firefighting is the use of aircraft and other aerial resources to combat wildfires. The types of aircraft used include fixed-wing aircraft and helicopters. Smokejumpers and rappellers are also classified as aerial firefighters, delivered to the fire by parachute from a variety of fixed-wing aircraft, or rappelling from helicopters. Chemicals used to fight fires may include water, water enhancers such as foams and gels, and specially formulated fire retardants.
A wide variety of terminology has been used in the popular media for the aircraft (and methods) used in aerial firefighting. The terms Airtanker or air tanker generally refer to fixed-wing aircraft; "airtanker" is used in official documentation.
Air attack is an industry term used for the actual application of aerial resources, both fixed-wing and rotorcraft, on a fire. Within the industry, though, "air attack" may also refer to the supervisor in the air (usually in a fixed-wing aircraft) who supervises the process of attacking the wildfire from the air, including fixed-wing airtankers, helicopters, and any other aviation resources assigned to the fire. The Air Tactical Group Supervisor (ATGS), often called "air attack," is usually flying at an altitude above other resources assigned to the fire, often in a fixed-wing plane but occasionally (depending on assigned resources or the availability of qualified personnel) in a helicopter.
Depending on the size, location, and assessed potential of the wildfire, the "air attack" or ATGS person may be charged with initial attack (the first response of firefighting assets on fire suppression), or with extended attack, the ongoing response to and management of a major wildfire requiring additional resources including engines, ground crews, and other aviation personnel and aircraft needed to control the fire and establish control lines or firelines ahead of the wildfire.
A wide variety of helicopters and fixed-wing aircraft are used for aerial firefighting. In 2003, it was reported that "The U.S. Forest Service and Bureau of Land Management own, lease, or contract for nearly 1,000 aircrafts each fire season, with annual expenditures in excess of US$250 million in recent years"
Helicopters may be fitted with tanks (helitankers) or they may carry buckets. Some helitankers, such as the Erickson AirCrane, are also outfitted with a front-mounted foam cannon. Buckets are usually filled by submerging or dipping them in lakes, rivers, reservoirs, or portable tanks. The most popular of the buckets is the flexible Bambi Bucket. Tanks can be filled on the ground (by water tenders or truck-mounted systems) or water can be siphoned from lakes, rivers, reservoirs, or a portable tank through a hanging snorkel. Popular firefighting helicopters include variants of the Bell 204 and the Erickson S-64 Aircrane helitanker, which features a sea snorkel for filling from a natural water source while in flight.
Airtankers or water bombers are fixed-wing aircraft fitted with tanks that can be filled on the ground at an air tanker base or, in the case of flying boats and amphibious aircraft, by skimming water from lakes, reservoirs, or large rivers. Various aircraft have been used over the years for firefighting. Though World War II-era bombers were for a long time the mainstay of the aerial firefighting fleet and are still in use, newer purpose-built tankers are coming online. The smallest are the Single Engine Air Tankers (SEATs). These are agricultural sprayers that generally drop about 800 gallons of water or retardant. An example is the Airtractor AT-802F, which can deliver around 3000lt of water or fire retardant solution each drop. Medium aircraft include the S-2 Tracker (retrofitted with turboprop engines as the S-2T) as used by the California Department of Forestry & Fire Protection (CDF), as well as Conair Group Inc. of Abbotsford, British Columbia, while the Douglas DC-4, the DC-7, the Lockheed C-130 Hercules, P-2V Neptune, P-3 Orion and others have been used as heavy tankers. The largest aerial firefighter currently in use is a Boeing 747 aerial firefighter, known as the Evergreen Supertanker that can carry 24,000 gallons fed by a pressurized drop system.The Supertanker entered service for the first time in 2009, fighting a fire in Cuenca, Spain. The tanker made its first American operation on August 31, 2009 at the Oak Glen Fire.
The next largest aerial firefighters currently in use include two converted Martin Mars flying boats in British Columbia (one of which was brought to southern California in September 2007 to help battle the wildfires there). Each Martin Mars can carry approximately 7,200 U.S. gallons of water or fire retardant each, and the Tanker 910, a converted McDonnell Douglas DC-10 that can carry 12,000 gallons of water or retardant. The Russian Ministry of Emergency Situations operates convertible-to-cargo IL-76 airtankers that can carry up to 15,000 gallons but have been operating with 11,000 gallon tanking systems, and a few of Beriev Be-200 amphibians.
Bombardier's Dash 8 Q Series aircraft are the basis for two new ventures. Cascade Aerospace has converted two pre-owned Q400s to act as part-time water bomber and part-time transport for France's Sécurité Civile, one of which is registered F-ZBMC while Neptune Aviation is converting a pre-owned Q300 as a prototype to augment their P2V aircraft.
Similar in configuration to the World War II–era PBY Catalina, the Canadair CL-215 Scooper, and Bombardier CL-415 SuperScooper are designed and built specifically for firefighting. The "Super Scoopers" are not common in the United States where only 2 operate seasonally in southern California. Los Angeles County leases two CL-415s from the Province of Quebec during the fall when the Santa Ana winds are at their worst. 6 American owned CL 215s operate for various State and Federal agencies. Critics of scoopers in the US claim that there is not enough suitable water in fire prone states. CL-215s have been employed with success in North Carolina, Minnesota, Michigan, Wisconsin, Washington, Alaska, Northern Idaho, and Montana.
French "Sécurité Civile" owns both Canadair CL-215 and CL-415, a handful of Grumman Trackers and some Russian Mil Mi-6 helicopters. Their pilots are usually recruited amongst the best pilots from "l'Armée de l'Air", usually from "Aéronavale" (Navy pilots on aircraft carriers) or acrobatic teams like "La Patrouille de France". It is a high-risk job that requires very skilled pilots.
Croatian Air Force uses six CL-415 planes, as well as the six AT 802s for (mainly) firefighting purposes.
Another amphibian is the Russian Beriev Be-200. It can carry a maximum payload of about 3,170 gallons (12,000 litres) of water, making "scoops" in suitable stretches of water in 14 seconds. It was successfully used to fight fires in the southern European countries such as Greece and Portugal.
The Lead Plane function directs the activities of the airtankers by both verbal target descriptions and by physically leading the airtankers on the drop run. The O-2 Skymaster and OV-10 Bronco have both been used as spotter and lead plane platforms. The Ontario Ministry of Natural Resources has also used the Cessna 337. The Beechcraft Baron was long used as a leadplane or air attack ship, but most were retired in 2003; more common now is the Beechcraft King Air, used as an air attack ship and leadplane.
In the United States, most of these aircraft are privately owned and contracted to government agencies, and the National Guard and the U.S. Marines also maintain fleets of firefighting aircraft. On May 10, 2004, The U.S. Forest Service (USFS) and the Bureau of Land Management (BLM) suddenly announced that they were cancelling contracts with operators of 33 heavy airtankers. They cited liability concerns and an inability to safely manage the fleet after the wing failure and resulting crash of a C-130A Hercules in California and a PB4Y-2 in Colorado during the summer of 2002. Both aged aircraft broke up in flight due to catastrophic fatigue cracks at the wing roots. After subsequent third-party examination and extensive testing of all USFS contracted heavy airtankers, three companies were awarded contracts and maintained a combined fleet of 23 aircraft.
Borate salts were used in the past to fight wildfires but were found to sterilize the soil, were toxic to animals, and are now prohibited. Newer retardants use ammonium sulfate or ammonium polyphosphate with attapulgite clay thickener or diammonium phosphate with a guar gum derivative thickener. These are not only less toxic but act as fertilizers to help the regrowth of plants after the fire. Fire retardants often contain wetting agents, preservatives and rust inhibitors and are colored red with ferric oxide or fugitive color to mark where they have been dropped. Brand names of fire retardants for aerial application include Fire-Trol and Phos-Chek.
Tactics and capabilities
Helicopters can hover over the fire and accurately drop water or retardant. The S-64 Helitanker has microprocessor-controlled doors on its tank. The doors are controlled based on the area to be covered and wind conditions. Fixed-wing aircraft must make a pass and drop water or retardant like a bomber. Spotter (Air Tactical Group Supervisor) aircraft often orbit the fire at a higher altitude to coordinate the efforts of the smoke jumper, helicopter, media, and retardant-dropping aircraft; while lead planes fly low-level ahead of the airtankers to mark the trajectory for the drop, and ensure overall safety for both ground-based and aerial firefighters. Water is often not dropped directly on flames because its effect is short-lived. Fire retardants are typically dropped ahead of the moving fire or along its edge and may remain effective for two or more days. This can create artificial firebreaks where the terrain is too rugged or remote for ground crews to cut fireline.
Helicopters are also used to deliver firefighters or ignite backfires and controlled burns. A driptorch slung beneath the helicopter (helitorch) can be used for this purpose. Another device called a Delayed Aerial Ignition Device (DAID) can be used, which shoots a stream of flaming "ping-pong balls" into the forest. The small plastic spheres which contain potassium permanganate are individually injected with ethylene glycol or glycerine just before they are ejected from the aircraft. This method's delayed redox exothermic reaction, which results in vigorous fire soon after mixing the chemicals, poses less of a danger to the helicopter than transporting burning materials. The ping-pong ball system works best in continuous fuels or in areas where a mosaic burn pattern is desired.
Aerial firefighting is almost always used in conjunction with ground-based efforts, as aircraft are only one weapon in the firefighting arsenal. However, there have been cases of aircraft extinguishing fires long before ground crews were able to reach them.
Some firefighting aircraft can refill their tanks in mid-flight, by flying down to skim the surface of any body of water. One example is the Bombardier 415. This is particularly useful in rural areas where flying back to an airbase for refills may take too much time. In 2002 an Ontario CL-415 crew proceeded to refill 100 times within a 4 hour mission, dumping an astounding 162,000 US gallons or 1,350,000 pounds of water on a fire near Dryden Ontario.
Comparison table of fixed wing, firefighting tanker airplanes
|Category||Water/Retardant capacity (US Gallons)|
|Air Tractor AT-802F||>USA||Light||807|
|Grumman S-2 Tracker||>USA||Medium||1,200|
|Douglas DC-4||>USA||Medium||no longer in service|
|Lockheed C-130 Hercules||>USA||Medium||Permanently grounded after accident|
|Boeing 747||>USA||Super Heavy||24,000|
|Dash 8 Q Series||>Canada||Medium||2,600|
|PBY Catalina||>USA||Medium||1,000 (or 1,500 for the Super model)|