U.S. Forest Service Should Consider a Different Mix of Aircraft to Fight Wildfires
July 29, 2012
The U.S. Forest Service should upgrade its large airborne firefighting fleet to include more amphibious scooper aircraft, with air tankers and helicopters in a supporting role during the initial attack of fires before they become large, according to a new study from the RAND Corporation.
Scoopers and air tankers are large aircraft used to drop large amounts of water or fire retardant on wildfires to assist on-the-ground firefighters in containing fires. Scoopers drop water while air tankers drop retardant. The Forest Service (an agency of the U.S. Department of Agriculture) supplies many of the large aircraft used to fight wildland fires on federal and state lands.
"Because scoopers cost less and can make multiple water drops per hour when water sources are nearby, we found that the most cost-effective firefighting fleet for the Forest Service will have more scoopers than air tankers for the prevention of large fires," said Edward G. Keating, lead author of the study and a senior economist at RAND, a nonprofit research organization. "However, air tankers are important in an ancillary role in initial attack for the minority of wildfires where water sources are not nearby, and possibly for fighting large fires as well."
The U.S. Forest Service has been trying to determine the best composition of aircraft to replace its aging air fleet for several years. Its fleet includes leased former military air tankers that date back to the 1950s. These older aircraft have been failing, with two fatal crashes in 2002 and two accidents in June 2012, one of which was fatal. Several weeks ago, legislation was finalized allowing the Forest Service to move forward with contracts for seven new tankers.
In 2009, the Forest Service hired RAND to study the composition of a mix of air tankers, scoopers and helicopters that minimized total "social costs," including the costs of wildfires—such as costs associated with destroyed property and fire suppression—and the costs of aircraft. Two prior studies conducted by the Forest Service were deemed insufficient for justifying major acquisitions by the federal Office of Management and Budget and the Department of Agriculture Inspector General.
Wildfire suppression costs have increased dramatically since 2000, currently averaging about $1.65 billion per year. Part of this rise is because residential development has expanded into areas that were previously wilderness, but it also may be a consequence of changes in weather and the accumulation of burnable wood and grasslands created by many years of aggressive wildland fire suppression, experts say.
The RAND study estimates the average social cost of a large wildfire at $3.3 million. Half of the fires cost less than $1 million and 10 percent cost more than $10 million. Fires near populated areas can be vastly more costly than fires in isolated regions. Large aircraft can help prevent these expensive large fires, easily justifying their annual cost if their activities account for the prevention of just a few large fires each year.
The RAND study focused on 1,500-gallon and 3,000-gallon air tankers, 1,600-gallon scoopers, and 1,200-gallon and 2,700-gallon helicopters. The Forest Service asked RAND not to include very large air tankers, like converted 747s or DC-10s, which can carry tens of thousands of gallons of retardant. The study also excluded smaller aircraft that carry fewer than 1,000 gallons of water or retardant.
Historically, the Forest Service's fleet of large firefighting aircraft has been composed primarily of air tankers and helicopters. Air tankers primarily carry fire retardant, which has advantages over water, but is also much more costly. There also are environmental concerns about the retardant. The key advantage of air tankers is their ability to support firefighting operations that may be far from the water sources needed by scoopers and helicopters.
Scoopers can be used in areas where there is ready access to large bodies of water. Although current models cannot carry loads as large as air tankers, scoopers can cycle back and forth between bodies of water and a fire, making multiple drops an hour. This compares to about 1.5 drops per hour for an air tanker, which must fly back to a runway and load more retardant before returning to the fire.
Helicopters also have the advantage of being able to make multiple trips in a short amount of time, and helicopters can make precise water drops. But helicopters have a limited range, fly slower than scoopers or air tankers, are less effective in mountainous areas, and cost more to acquire and maintain than scoopers on a per-gallon-delivered basis.
The total annual capital and operating costs per aircraft range from approximately $2.8 million for a 1,600-gallon scooper to $7.1 million for a 3,000-gallon air tanker, before factoring in the cost of fire retardant, Keating said.
Helicopters can use bodies of water as small as 12 feet in diameter. Scoopers need larger bodies of water, generally ranging from a quarter of a mile to eight-tenths of a mile in length, depending on obstacles adjacent to the water. RAND researchers found that at least two-thirds of the fires studied have been within 10 miles of a body of water that appeared to meet scoopers' requirements, and about 80 percent of fires have been within five miles of water bodies that would accommodate helicopters.
The RAND report was delayed twice because the Forest Service and RAND agreed to develop a second analysis drawing on a Forest Service analytical tool called the Fire Program Analysis (FPA) system. As a result, the RAND study developed two separate, but complementary, simulation models to evaluate the effectiveness of fleet mix options. One is simpler and allows for better evaluation of the influence of model assumptions, while the other rests on Forest Service assumptions built into Fire Program Analysis system.
"While the two models yielded different estimates of optimal fleets, both approaches suggested a predominant role for scoopers," Keating said.
Another finding of the study was the importance of efficient prepositioning of aircraft to meet the next day's firefighting needs and what the researchers termed "dispatch prescience."
When aircraft can be correctly and flexibly prepositioned, fewer are needed. Further, if aircraft dispatch can be optimized—that is, when they can be sent to just those fires where they make the difference between having a large fire or not—fewer aircraft would be needed. The Forest Service could dramatically reduce its aviation costs if it could increase dispatch prescience and prepositioning accuracy.
"We think there may be an opportunity for the Forest Service to improve its aircraft location and dispatch algorithms, and possibly reduce aviation costs considerably," Keating said.
The study does not recommend a specific number of aircraft, but provides a framework for the Forest Service to rebuild its fleet. Variables include how many days the aircraft would spend at particular base locations, the value of preventing certain fires and how accurately dispatchers can determine what kind of fire the Forest Service is facing. The range of solutions is on the order of 15 to 30 scoopers to be used in conjunction with two to six air tankers and a comparable number of 2,700-gallon helicopters.
The study, "Air Attack Against Wildfires: Understanding U.S. Forest Service Requirements for Large Aircraft," can be found at www.rand.org. Other authors of the study are Andrew Morral, Carter Price, Dulani Woods, Daniel Norton, Christina Panis, Evan Saltzman and Ricardo Sanchez.
Research for the study was conducted under the auspices of the RAND Homeland Security and Defense Center, which conducts analysis to prepare and protect communities and critical infrastructure from natural disasters and terrorism. Center projects examine a wide range of risk management problems, including coastal and border security, emergency preparedness and response, defense support to civil authorities, transportation security, domestic intelligence programs, technology acquisition and related topics.