USA — for decades lumbering, propeller-driven planes used to lay down ribbons of red fire retardant on wildfires — have entered the jet age.
Three years after the U.S. Forest Service asked for bids to replace its aging fleet of military surplus planes with faster, safer and newer tankers, an Oregon company flew its first sorties in June with two Boeing MD-87s.
The twin-engine passenger jets retrofitted by Erickson Aero Tanker of Madras — launched from the Redmond Air Tanker base to work on the Two Bulls fire west of Bend.
The first jet dropped 48,000 gallons of retardant in less than four hours — that’s 12 drops of 4,000 gallons each.
From the ground, it was clear what the major difference was between the older planes and the new generation tankers: speed.
“It’s no different to fly than an airliner,” said pilot Doug Griffin, who flew five missions on the Two Bulls fire and has flown piston-powered tankers for years. “Even when fully loaded, it weighs less than an airliner. But it’s a much faster airplane.”
When Griffin pushes the drop button on the control column in the cockpit, gravity takes over, delivering the 4,000 gallons of red slurry in 3.8 seconds.
Inside, the jet’s seats, galley and restrooms have been stripped away, replaced by twin 2,000-gallon tanks that sit over the wings. Simple hydraulics open the long, thin doors, called spades, on the underbelly, releasing the retardant.
“There’s not really too much to it,” Griffin said. “All we’re doing is putting down retardant on the flanks and the heel of the fire, trying to pinch it off. We are strictly there to support firefighters on the ground, buying them some extra time.”
Erickson Aero Tanker, a division of Aero Air in Hillsboro, bought seven MD-87s and so far has modified two as tankers and is using a third for parts. The company plans to modify the remaining four jets to fly for the Forest Service in coming years, said air tanker operations manager Glen Newton.
The Forest Service also has contracted with the operators of six additional jet air tankers, including two DC-10s that can dump 11,000 gallons of retardant — a stripe a mile long — in one trip.
Giant C-130 aircraft (considered turbine-powered aircraft even though they have propellers) also have been pressed into service this season, fitted with temporary modular airborne firefighting systems that allow them to dump 2,700 gallons of retardant on each run over a fire.
Erickson jets also dumped retardant on the Shirley fire in California in June, but the company voluntarily pulled its jets from service after noticing surging in the jet engines that appeared to be caused by retardant gettng sucked into the turbines, Newton said.
Engineers have made slight modifications to the spade openings and jet T-101 is expected to return to service next week; T-108 will return the following week.
This next generation of air tanker must pass a series of rigorous tests before they work the firelines, said Jennifer Jones, a spokeswoman for the Forest Service at the National Interagency Fire Center in Boise.
Those include submitting a tank design for the aircraft, proving the tank design in a controlled grid test and dropping retardant on a series of cups laid out on the ground. The aircraft also must pass muster with the interagency Air Tanker Board and the Federal Aviation Administration.
The process came about after a series of crashes and deaths involving the old air tanker fleet. Thirty-six crewmen died in crashes between 1994 and 2013, including planes that had wings fall off, according to a Los Angeles Times investigation.
“The process really shows the difficulty and complex problems that come with turning a passenger plane into an air tanker,” Jones said. “No one makes an air tanker per se, the aircraft have to be modified. All the steps are geared to make sure the plane flies safely and effectively.”
Although the so-called legacy, piston-powered air tankers are still flying, they’re wearing out, said John Kent Hamilton, aviation safety manager for the Forest Service.
“With attrition they will be replaced by jets or turbo-prop aircraft,” Hamilton said.
This fire season, Jones said, the Forest Service has a total of 23 air tankers available for fire duty — nine are jets and 14 are legacy tankers.
But no matter how many tankers are out there, they don’t replace firefighters on the ground, she said.
“Aircraft alone can’t put out a fire most are too big and too hot,” she said. “What the tankers do is put down the retardant to reduce the intensity and the fire’s rate of spread. It’s firefighters who put the fires out.”