Altitude, Summer, 2010
by Ed Unrau
Until the 1950s, once a forest fire or prairie wildfire spread across the landscape, there wasn’t much to do except watch it burn and try to limit the path of destruction.
The situation changed with the development of aerial control techniques.
In Canada, one of the first documented cases of where an aircraft was used in forest fire control occurred in the summer of 1921 when a pilot spotted a fire on an island near Sioux Lookout, Ontario. He returned to base to pick up a ranger with the necessary fire-fighting tools and flew back to the island; the fire was extinguished before it got out of control. Flying crews and equipment to “hot zones” by floatplane or helicopter has been a mainstay of fire fighting control ever since.
There is no record of who came up with the idea of dropping water on fires, although it is an obvious aviation application. There are reports that some of the first experiments consisted of attempts to drop water onto fires from wooden beer kegs mounted in single-engine airplanes.
Wikipedia, the on-line encyclopedia provides the following historical insight: “aerial firefighting, or water bombing, was tested experimentally by Art Seller’s Skyways Air Services in Canada in 1952 (dropping a mix of water, fertilizer and seed), and established in California in the mid 1950s.”
A search for Art Seller ends up at the website of the Canadian Museum of Flight in Abbotsford, B.C. The museum’s biography on Seller agrees with the Wikipedia claim, stating that “the use of aircraft for this purpose had never before been seriously tried anywhere in Canada… Although the idea was being developed in several parts of the U.S., Skyways and B.C. were now leaders, at least in Canada, with the idea.”
Other clues into the development of aerial firefighting are found on the websites of the Ontario Ministry of Natural Resources and Borealforest.org, a website maintained by Lakehead University in Thunder Bay. The following is a synthesis of that information.
In the mid-1940s, Carl Crossley, a pilot-engineer stationed at the Temagami base of the Ontario Provincial Air Service (OPAS), had the idea that if military aircraft could carry large loads of bombs against enemy forces, why couldn’t civilian aircraft bomb forest fires with loads of water?
Crossley created a complex contraption to load water from the lake surface into an onboard barrel while the aircraft taxied along the surface. The device did not work and he settled with pumping the water onboard while the plane idled.
He experimented with the idea of loading water into the floats. Because 1920s-era floats were not baffled or compartmentalized, pilots attempting the manoeuvre ran the risk of upsetting aircraft balance by over- or under-filling the floats – pilots had no way of knowing how much water they were taking on. Further, they had no way of dumping the load quickly.
Crossley then designed and built a set of floats that he fitted onto a Noorduyn Norseman. His solution included installing water pickup and drop controls in the cockpit. Crossley was successful in attacking a fire near Temagami in August 1945. Carrying a mere 100 gallons of water at a time, which took nine seconds to jettison, Crossley was able to suppress the fire sufficiently so ground crews could move in to finish it off.
Dropping water onto forest fires with any degree of effectiveness was also a challenge. Crossley’s experiments at dropping water from onboard containers resulted in the liquid dispersing into a fine mist with no effect on the fire. Another experiment involved dropping water-filled wax paper bags; this proved equally ineffective because it was difficult to deliver a concentrated rain of water and, further, when a bag actually scored a direct hit, the impact sent embers flying, spreading the conflagration.
Crossley left the Ontario air service before his ideas were fully developed. One reason for his departure appears to be the fact that air service management did not share his enthusiasm for aerial fire fighting. He later pitched his ideas to the federal government, where there was more interest but little action.
But Crossley’s ideas weren’t forgotten. Tom Cooke, a former RCAF Canso pilot who joined OPAS, believed Crossley’s concept had merit. And he proved it in the 1950s. The idea of carrying water-filled tanks in the cargo cabin and jettisoning the water out the side doors was quickly scrapped. Cooke, together with air engineer George Gill, designed a water dropping design known as roll tanks. The tanks were attached to the floats of Beavers and Otters with a forward-facing pipe below the waterline. As the aircraft taxied, the forward motion directed water up the submerged pipe into the open-top tanks. With full tanks, the plane took off for the fire site where the pilot released a latch to roll the tanks sideways to empty them. This delivered a small, but concentrated load. The counterweighted tanks automatically reset themselves for the next pick-up.
In the summer of 1957, Cooke got his chance to prove the viability of “water bombing.” At a fire near Sudbury, with an Otter equipped with roll tanks, he was able to contain a fire until the ground crews arrived with their equipment. It was later conceded that aerial waterbombing was an important factor in containing the fire.
There were other attempts to develop water bombers. In the U.S. for example, there were projects to modify surplus Stearman PT-17 and N3N military biplanes as air tankers after the Second World War. But their limited capacity made it obvious that aircraft capable of carrying greater loads were necessary. Retrofitting existing air force bombers was one response because these surplus aircraft were available and inexpensive, and were designed to transport bombs or cargo over long distances. In short, the “retired” bombers had the manoeuvrability, speed and structural strength to withstand extreme stresses of aerial firefighting. A variety of WWII-era aircraft were soon seen over forests; some examples include the Boeing B-17 Flying Fortress, Grumman PBY Supercat and Privateer, F7F Tigercat, and Fairchild C-119 Boxcar.
Ten years after Cooke’s demonstration near Sudbury, the Canadair CL-215 made its debut in October 1967 as the first aircraft specifically built for aerial firefighting. It was designed as a firefighting amphibian to replace the assortment of planes used as “water bombers.”
Arising from market research and a request by forestry officials in Quebec who wanted an effective way of delivering water to forest fires, the original concept envisaged a twin-engined floatplane altered into a “firefighter.” The preliminary Canadair design, the CL-204 was a purpose-designed water bomber that evolved into an amphibious flying boat. The definitive design product, the CL-215, received program go-ahead in February 1966 and made its maiden flight on October 23, 1967. The aircraft was first purchased by the Province of Quebec, and the Protection Civile in France. The CL-215 was produced in five model series (including a turbo model, CL-215T) until April 1990. Over its 33-year production run, 125 aircraft were built and delivered around the world. The CL-215 has also been used in other operational configurations such as maritime patrol and search and rescue.
The CL-215’s unique capabilities are apparent when it swoops down to touch the surface of the water to scoop up its water load in around ten seconds before climbing aloft to drop the water onto the fire. Flying just 100 feet above the drop zone, its belly doors – like the bomb bay doors on a military bomber – open to drop 1,400 gallons of water or a water-chemical mix onto a fire. An amphibian by design, the CL-215 is equally operational on water or land, where its on-board tanks can be filled with water or fire-retardants in about two minutes.
The CL-215 is rugged. It withstands “dive bomber” handling tactics, resists corrosion from the water and retardant chemicals, and survives the heat and pollutants from the fire itself. Durability and reliability were vital requirements in the CL-215 design because the demands of a raging forest or wildfire typically require dozens of runs in a single day. (When water and fire sites are in close proximity, CL-215s have recorded up to 125 drops in a day.)
In 1986, Canadair was folded into Bombardier Inc., and based on the success of the CL-215, the Bombardier 415 was introduced with production beginning in 1994. The Bombardier 415 has an updated cockpit, aerodynamics enhancements and changes to the water-release system to create a modern firefighting amphibious flying machine. Compared to the CL-215, the Bombardier 415 has increased operating weight and speed, improved productivity and performance, and can deliver massive quantities of suppressant to fire sites. The Bombardier 415 is still the only aircraft specifically designed for aerial firefighting. The 415 aircraft takes 12 seconds to scoop 6,137 litres (1,621 U.S. gallons) while skimming over water; foam suppressant may be added during this intake. To date, 198 aircraft have been delivered to 20 worldwide customers. A spin-off model, the Bombardier 415MP, can be configured for other applications. Bombardier continues to support the CL-215 and CL-215T aircraft still in service.
- Bombardier Aerospace website, Montreal, Quebec.
- Borealforest.org, the website of northwestern Ontario forestry issues maintained by the Faculty of Forestry and the Forest Environment, Lakehead University.
- Canadian Museum of Flight website, Abbotsford, British Columbia.
- Ministry of Natural Resources, website, Province of Ontario.
- U.S. Centennial of Flight Commission website, a site sponsored by the National Air and Space Administration.
This article originally appeared in the Summer, 2010 edition of Altitude.