CANADA: AERIAL SUPPRESSION EFFECTIVENESS RESEARCH
BY MELANIE WHEATLEY, COLIN MCFAYDEN, RAZIM REFAI, EMILY HOPE, AND HEATHER SIMPSON
Canada’s boreal zone spans more than 550 million hectares – an area larger than the European Union.
On average, about 8,000 wildfires ignite across the country each year, burning about 2.1 million hectares. During extremely active fire seasons – such as 2023 – up to 15 million hectares burned nationwide.
Despite these numbers, the boreal forest is a fire-resilient ecosystem and relies on wildfire for renewal and health. However, when fires threaten valuable forest resources, human lives, or property, wildfire suppression tactics come into play to minimize unwanted impacts.
Suppression or control of wildfires with airtankers is a core strategy for most Canadian provincial and territorial wildfire management agencies. Airtankers include fixed wing and helicopter aircraft that drop water, retardant, or other suppressants onto wildfires.
Across Canada’s vast forests, a variety of airtankers are used, each suited to different fire conditions and landscapes.
Skimmer airtankers, which scoop water from lakes, are commonly used in areas with abundant waterbodies such as Eastern Canada. Land-based airtankers, which rely on airport refueling, are more common in regions where lakes are fewer or harder to access, such as some areas in Western Canada and the northern territories.
Some regions use both types of aircraft, combining the advantages of direct suppression with the skimmer airtanker that drops suppressant right on the flames, and indirect suppression, with land-based airtankers that drop suppressant ahead of the fire to create a barrier.
Helicopters equipped with water tanks or buckets are also widely used because they can pick up water from small lakes and rivers and manoeuvre through tough terrain.
Provinces and territories secure and operate their airtanker fleets in different ways. Some regions own and operate their own fleets of fixed-wing airtankers, some contract aircraft (and crew) from specialized suppliers, and others do a mixture of both. Helicopters (rotary-wing airtankers) are generally contracted based on demand. But no agency is left to fend for itself when fire activity exceeds the number of airtankers available.
The Canadian Interagency Forest Fire Centre (CIFFC) helps coordinate the sharing of aircraft and personnel across the country and internationally, ensuring that agencies can share resources and response effectively to wildfire. The record breaking 2023 fire season in Canada presented a historically unprecedented level of resource demand. Canadian agencies received assistance (firefighters and overhead personnel) from 12 countries. Considering climate change, it’s expected that 2023 may not be anomalous, but rather a signal of a new normal.
Leveraging research to improve suppression effectiveness in wildfire operations
Innovation in the aviation space to support wildfire suppression has its history deeply rooted in Canada. The use of airtankers to deliver water – commonly referred to as waterbombing – originated in Canada in the 1940s when pilots in northern Ontario began experimenting by dropping waxed paper bags of water or mounting water drums on aircraft to assist ground crews with suppressing fires. Since then, Canada has continued to innovate and conduct research on airtanker suppression effectiveness. Research in Ontario in the 1990s guided agencies toward an optimal configuration for their airtanker fleets – the type and number of aircraft needed to meet average fire demands.
The complex problem of defining and measuring the effectiveness of airtankers is not straightforward and therefore requires studying the operational use of airtankers in many stages throughout the fire-response process. The current research in Canada is examining the operational use of airtankers including deployment strategies, dispatch prioritization, and understanding and maximizing the effectiveness of airtanker use on fires.
One of the challenges fire managers face is day-basing – a question of where, when, and how many airtankers to pre-position in strategic locations. Researchers in Alberta and Ontario are developing airtanker positioning models to support decision making and resource prioritization.
To lower initial attack response times, a typical approach is to use pre-set rules such as attack radius, response time and fire hazard to identify optimal locations to position airtankers. Studies in British Columbia and Ontario use historical fire and airtanker use data to identify factors that influence airtanker dispatch during initial attack, insights that can be incorporated in optimization simulation models.
Understanding how well airtankers work in real-world operations is critical. In Ontario, researchers have used detailed observations from skimmer airtanker missions recorded from trained air attack officers who are deployed with the airtankers, recording operational mission data including detailed observations of fire behaviour directly observed from the fireline, along with the volume of suppression applied during a skimmer airtanker mission. This data was used to develop statistical models that quantify the ability of CL-415s to reduce fireline intensity on both initial attack and for sustained action missions. These models present the required amount of suppression to reduce fire behaviour to a smouldering state given various levels of presuppression fire behaviour. Importantly, because of the ability of the CL-415 to scoop water from nearby lakes resulting in fast turnaround-times, the findings indicate that in Ontario, the CL-415 airtanker can be effective at higher intensities than previously indicated by current operational suppression effectiveness thresholds used across Canada – an important finding to guide future airtanker use.
Theoretical models, based on what we know about the physical properties of how water and fire interact, have been developed to assess and compare the effectiveness of different skimmer and rotary-wing airtankers used across Canada’s boreal. In 2023, the Ontario Ministry of Natural Resources and Natural Resources Canada published the Reference Guide to the Drop Effectiveness of Skimmer and Rotary Wing Airtankers – a valuable tool for fire management agencies to compare the effectiveness of these different airtankers under varying levels of fire behaviour. Efforts are ongoing to communicate these findings to fire operational personnel.
Because wildfire is a dynamic and complex process, fire management research must go beyond the theoretical science. Field-based research – research on actual wildfires – is considered a gold standard to understanding not only fire behaviour but airtanker suppression effectiveness.
Before examining airtanker suppression on wildfires in the field, an understanding of drop pattern, or footprints of airtankers, is important. Efforts to study and quantify drop patterns, which measure the distribution and depth of water, suppressant, or retardant dropped by airtankers, date back to the 1960s. More recently, Canadian research firm FP Innovations, the Ontario Ministry of Natural Resources, and Natural Resources Canada developed drop patterns for airtankers used across Canada. Various airtanker types – including the Canadair CL-215T, Canadair CL-415, AT-802 Fire Boss, AT-F802F, Sikorsky S-61N, Bell 212, and others – have been tested across open fields, forested, and fuel-treated stands. Using a modified cup-and-grid method, where hundreds of cups are placed on the ground in a large grid to measure the amount of water, suppressant, or retardant collected after each drop, researchers have documented the coverage levels and drop footprints of these aircraft that are commonly used in Canada (see photos below).
Centre. Over the last 10 years, an average of 24 skimmer airtankers and four land-based airtankers are mobilized across Canada each year (this does not include
short-term support such as cross-boundary quick-strike coordinated through localized compacts). Plot is re-created from https://www.ciffc.ca/mobilization-stats.
Reference Guide to the Drop Effectiveness of Skimmer and Rotary Wing Airtankers.
Building on our understanding of airtanker drop footprints, recent field experiments have examined the impact of airtanker suppression action on active wildfires. FPInnovations and Alberta Wildfire have conducted several field-based studies that explore impacts of suppression from both rotary-wing and land-based airtankers. Studies involving helicopter tankers (Sikorsky S-61N) emphasized effectiveness in direct attack applications while those involving land based airtankers (Dash 8-Q400AT) looked at retardant effectiveness in indirect attack applications. Methods used in these studies relied on airborne thermal infrared imagery to collect data from a helicopter (figure 3). These research methods are also being used to explore the effectiveness of suppression activities from night-vision system aided helicopters for actioning fires at night.
In 2024 the Ontario Ministry of Natural Resources, The National Research Council of Canada and Natural Resources Canada initiated field research to test the effectiveness of the CL-415 on wildfires in Canada’s boreal forest. Researchers, paired with fire behaviour experts and operations staff, used an infa-red imaging-equipped helicopter positioned above CL-415 suppression activity to record the associated impact on fire behaviour. This project leverages an experimental design where controlled replicates of airtanker drops are applied in real-world settings to try to limit variability in observations as much as possible. This innovative methodology will process the infa-red imagery to provide detailed estimates of fire spread and fireline intensity, attributes that fire managers commonly used to support their decision making. These field-based studies are necessary to form a baseline scientific understanding of airtanker effectiveness, which will be the foundation of future studies related to optimizing airtanker use in fire management.
There is plenty to learn about how to support the optimization of airtanker use during operations and plan for their long-term role in wildfire management.
The execution and implementation of this research requires close collaboration between those who use the aircraft and those who research them. Canada is fortunate to have strong collaborative relationships between researchers and fire managers, a relationship that is strengthened through networks such as the CIFFC Aviation Working Group, a national group of aviation fire managers who share knowledge on aviation-related challenges in fire management and support innovation to address those challenges.
Agencies play a key role in the research process by identifying research needs, sharing operational data, providing expertise, and supporting field studies that directly measure airtanker performance. Researchers bring the analytical tools and scientific methods to refine and expand our understanding of aerial suppression effectiveness. By combining operational expertise with research, Canada continues to refine its approach to aerial fire fighting, ensuring a safe, effective use of aviation resources to support wildfire management for years to come.
Writers Melanie Wheatley, Colin McFayden, Razim Refai, Emily Hope, and Heather Simpson contributed to the overview story on page 12. See their bios on pages 14 and 16.
