Firefighting Aircraft: Is Bigger Better?


May 20, 2013

Wildfire air tanker

Todd Burton

The western United States will be facing fire season in a few months and the Forest Service is preparing to respond within the budget constraints of sequestration.

The summer fire season is the most taxing time for the Forest Service's fleet of aircraft because of the sheer number of fires that start across the western half of the U.S. There have already been large fires even before the start of this year's wildfire season, such as the Camarillo wildfire near Malibu, CA, that has burned at least 28,000 acres. As part of ongoing efforts to recapitalize their fire-fighting aircraft fleet, the Forest Service recently announced that it would be using six large air tankers and a DC-10. Large air tankers drop between 1,000 and 4,000 gallons of water or fire retardant, but the DC-10 is much larger and is in a class of aircraft known as very large air tankers (or VLATs in Forest Service parlance). VLATs can drop 10,000 gallons or more of water or fire retardant to put out or contain fires.

In 2012, when RAND published a study of the Forest Service's aviation program, our focus was on the cost effectiveness of large aircraft including large helicopters, scoopers, and large air tankers—but not VLATs. Our study, which focused specifically on the options under consideration at the time, found that the most cost-effective fleet would primarily consist of scoopers, but we did recommend that the Forest Service use a few large helicopters and air tankers for a niche capability targeting those fires where scoopers could not easily acquire water.

While most people are familiar with images of raging forest fires that burn thousands of acres, a primary use for aviation is in the initial attack on wildfires. Initial attack occurs shortly after the fire has been ignited, but before it has had the chance to grow large. When a fire is caught at this stage it can be put out with relatively few resources and before it has done significant damage. Thus, having a fleet of aircraft that can support a quick response to fires in their early stages is of central importance. We were able to identify several key factors that influence the ability of the Forest Service to respond quickly, including predictions about where fires will occur, the basing of the response aircraft, and the rate at which water or retardant can be applied to a fire.

  • We found that a key consideration when buying aircraft for fighting wildfires was the accuracy of the fire predictions. The less accurate the forecasts for the number and speed of fires arising over the next few days, the more aircraft were required. Right now wildfire forecasters are not sufficiently prescient to perfectly preposition aircraft to respond to tomorrow's fires. This makes a distributed capability particularly useful because it increases the likelihood that an aircraft will be close by if a fire does occur.

  • Basing is also an important consideration. Because of their size, VLATs have access to fewer airports than scoopers, helicopters, or even large air tankers, which means they have farther to travel to reach fires. Large air tankers are also more restricted than scoopers or helicopters, although there are still more than 1,000 airports that could be used. Our study found that basing could have a substantial effect on the number of aircraft required to fight wildfires.

  • An aircraft's capacity and speed largely determine the rate at which water or retardant can be applied to a fire. VLATs certainly have the capacity to apply large amounts of fluids to a fire, but because of the distances travelled they may not be able to get a second load very quickly. On the other hand, smaller aircraft like scoopers don't have the same capacity of VLATs, but because they can refill in lakes and rivers, they can quickly return for repeated drops. Large air tankers (such as C-130s) have more capacity than scoopers, but must fly back to an airport to refill, which can also put them at a time disadvantage compared to scoopers. This was one of the primary reasons that the RAND study recommended using scoopers to fight most wildfires.

Our research suggested that the Forest Service should predominantly use scoopers for fighting wildfires, but also that large tankers have a niche role. The first part of the Forest Service's aircraft modernization focused on large tankers. This now presents an opportunity for targeted data collection and an independent analysis to determine the effectiveness of their aircraft portfolio, looking carefully at response time, effectiveness, and cost across a range of initial attack conditions throughout the Forest Service's geographic domain.

An independent study could also assess the results from use of the DC-10 tanker, which could then inform decisions about the best use for VLATs. This type of analysis could help determine if further changes in the mix of aircraft are needed. Independent analysis of wildfire forecasts, basing, and fleet responsiveness should also be considered as the Forest Service and Congress work through the acquisition policy for new aircraft. Well-designed data collection and independent, objective analysis will be key to informing these important decisions.

Carter Price is a mathematician at the nonprofit, nonpartisan RAND Corporation.

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