Fighting the Caldor Fire a feat from the sky
Firefighters on the ground endure arduous conditions in terrain sometimes not fit for a mountain lion. But now they get the help of new aerial firefighting equipment in the form of large transport category aircraft, the biggest on the Caldor Fire being a DC-10 provided by 10 Tanker, one of only four DC-10-30 former airliners converted into a massive aerial firefighting tool.
The 10 Tanker fighting the Caldor Fire was formally owned by Continental Airlines and started its new life as an aerial firefighting tool in about 2006. Based in Albuquerque, N.M., these DC-10-30s are currently the biggest fire bombardment tool in the firefighting arsenal, dropping 85,000 pounds (9,400 gallons) of retardant (or water) in one pass of a mile long and hundreds of yards wide — all in about 20 seconds. And for the Caldor Fire, the McClellan-based 10 Tanker can takeoff, deliver its load and return to base in 35-40 minutes and take off again 20 minutes later.
A 10 Tanker, which has a wingspan of 165 feet, is 182 feet long and stands about 57 feet high, started life carrying almost 400 passengers in a fuselage with an interior width of nearly 19 feet. It has three, super powerful GE 51,000 pounds of thrust jet engines. With roughly three hours of fuel on board (about 9,000 gallons) and almost 90,000 pounds of fire retardant and/or water, a 10 Tanker takes off weighing 390,000 pounds, which adds greatly to its performance safety margin.
A 10 Tanker usually follows a lead aircraft — in Cal Fire’s case an OV-10 Bronco — and it approaches its “bomb” run just 250-300 feet above the trees at an air speed of 140 knots (about 160 mph). At least 30 degrees of flaps are deployed for additional lift and control, but flying this bird at such light weights makes it very responsive to its three jet engines. Airframe stresses are also reduced at such low speeds while allowing for the DC-10-30 to put its firebombing material exactly where it needs to go. The pilots make their runs with nose down pressures on the control yoke and then release pressure after the run as the big DC-10 makes a rapid, well-controlled climb out with mammoth reserve power available.
There are only four 10 Tankers operating (one on the Caldor Fire). Other excellent ex-airliner aircraft also deliver fire-bombing services in the Caldor fight; one being an Erickson converted MD-87 airliner amd the other an Avro RJ85. Each aircraft can carry 3,000 gallons of fire-bombing materials. There were two CL-415 Super Scoopers on the fire as well. The RJ85 and Super Scoopers were from Aeroflite, a Spokane, Wash., company.
The CL-415 has been fighting fires for more than four decades, originally as a piston powered CL-215. But the much-improved, turbine-powered CL-415 is amazing in that it can drop more than 20 loads of water on a fire in an hour, depending on the proximity of the water source. Each load is 1,600-plus gallons. At Tahoe, with the lake so close, the two Super Scoopers working could do 45 1,600-gallon drops in an hour or close to one drop in every 80 seconds. There is a Spanish demonstration video of the CL-415 in operation on the internet that’s about four minutes long (type “43 Grupo 2012” on your address bar).
Aeroflite has been in the aerial firefighting business since 1963, starting with DC-4s and a few years later it acquired its first pair of CL-215s. Now it uses the Avro RJ85 and CL-415. The Avro RJ85 was originally a midsize airliner with four jet engines, a high wing and known for its slow speed stability, making it an excellent choice for conversion to a firefighter. It carries 3,000 gallons of water or fire retardant and can lay down a long swath of material on a fire with pinpoint accuracy. Approaching a fire at just 150-175 feet at a speed of about 130 knots (150 mph), Aeroflite pilots are certified as initial attack pilots so a lead aircraft is not necessary although Cal Fire may provide one or provide specific drop locations. The RJ85 is powered by four Honeywell advanced fan jets of approximately 7,000 pounds of thrust each. It flies with a 27,000-pound load of fire retardant. When released, the RJ85 has amazing reserve power. Turnaround time for the RJ85 is just 16 minutes, including taxi times for landing and takeoff.
The CL-415 mentioned above was specifically designed by Canadair/Bombardier (yes, those guys who make Ski-Doo and Sea-Doo) as a fire bomber. Powered by two Pratt and Whitney turbo-prop engines of nearly 2,400 hp each it can scoop a 1,600-gallon load of water in five seconds and be over a fire in less than a minute. While its maximum speed is about 225 mph, high speed isn’t a requirement; low speed stability and reserve power are and the CL-415 delivers. With approach speeds of just 110 knots (126 mph) and clearing the terrain by just 150 feet, this 45,000-pound fire bomber can deliver knock-out blows to a fire with amazing accuracy and effectiveness — and do it every three minutes or less as in the case of the Caldor Fire. After a drop its weight drops by almost 14,000 pounds, making it a very nimble performer.
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