Having spent most of my years in southern British Columbia (BC), Canada, I have become all too familiar with the challenges of living with wildfire. We experience with greater regularity the pains of this escalating problem; the oppressive smoke that chokes our lungs, the environmental damage, and the widespread social and economic impacts as people and businesses are displaced when wildfires encroach upon communities.
As the impacts of unwanted wildfires mount globally, wildfire management agencies are trying to adapt to give themselves the upper hand. Significant investments are being made in cleaning and treating forested areas – particularly those close to communities – to mitigate the risks of future wildfires. This progressive approach is leaving many wildfire agencies in the unenviable position of having to fund risk mitigation activities while simultaneously increasing investments in wildfire response capacity to address the immediate suppression needs. Wildfire agencies are contemplating how to best configure and deploy their resources to achieve their wildfire management goals.
Airtankers are critical tools in the response to wildfire and are a cornerstone to the success of many mature and well-funded agencies. Their value-proposition is reliant upon rapid response, the ability to access remote areas, and the powerful impact they can have in containing unwanted wildfire. Given their significant operational value and high costs of utilization, it is critical that agencies optimize their use for impact and efficiency.
Fundamental to optimizing an airtanker fleet is determination of its basic composition, premised on intended role and suppression strategy. Amphibious airtankers skim the surface of water bodies, scoop water into their tank, (may) inject a suppressant chemical into the load of water, and deliver the payload directly onto the fire. This approach to aerial firefighting is predicated on reducing fire intensity. Alternatively, land-based airtankers are loaded with long-term retardant at an airport and jettison the payload ahead of or adjacent to the fire. The intention in this approach is to impede fire growth beyond the retardant barrier created. In essence, land-based airtankers and their retardant are used to contain the fire, while amphibious airtankers and their suppressants are used to ameliorate its behavior. While the two differing approaches share a common recipe for success in buying time for ground resources to mobilize and extinguish the wildfire, they have their own unique advantages and disadvantages in how they do so.
What differentiates amphibious airtankers is their ability to deliver high volumes of water directly onto a fire at a relatively low price. As such, proximity of waterbody to fire is a key driver of efficiency and overall mission effectiveness. Quick turnaround cycles of aircraft can result in considerable impacts to a fire, reducing its intensity and spotting (mass transfer of embers through the air) potential. Given that the payload of amphibious aircraft is water, the cost per litre is lower than that of retardant. This is still the case when the water is supplemented by the addition of chemicals (class A foam or a water-enhancing gel) into the payload. The investment into infrastructure required by wildfire agencies to support the amphibious fleet is relatively low compared to land-based airtanker operations that require considerable product (retardant) storage and loading equipment.
A disadvantage of amphibious operations is the short-lived benefits often afforded by suppressant delivery. Once the water has evaporated, the suppressant is no longer effective. This differs from land-based airtanker operations where retardant payloads can continue to impede fire growth even when the water component of the solution evaporates and the product is dry. Furthermore, water drops are more susceptible to deleterious influence of the airmass and the droplet atomization process, particularly in low humidity burning conditions. This is likely to result in less product reaching the desired fuels (recovery rate), as compared to retardant operations.
Land-based airtanker operations exhibit a temporal advantage over amphibious aircraft and their suppressants. Retardant impacts on fire are relatively long lasting and can be further incorporated into tactics, where the retardant containment line is built well in advance of a fire or as a back-up contingency containment line. As land-based airtankers’ missions are complete once a retardant line is established, time commitments for aircraft on each fire are relatively brief, availing the airtankers for deployment to successive multiple targets, if required. For wildfire agencies who experience multiple new fire starts contemporaneously, whether from lightning or human activity, land-based airtankers can enable quick containment of multiple fires within a fuel cycle. Comparatively, amphibious aircraft are often actioning a single fire per fuel cycle.
In recognition of the two modalities of airtanker operations (amphibious and land-based), the obvious question is which approach is better? Better is likely site-specific, dependent on various attributes including the characteristics of the fire and its environment. Furthermore, it is directly related to the macro underlying realities of each jurisdiction such as prevalence of suitable water sources, airport locations, and agency comfort using additives/chemicals to enhance the effectiveness of their aerial operations. Best, for many wildfire management agencies is a balanced approach, combining both amphibious and land-based aircraft, taking advantage of the unique value propositions offered by each.
During my previous career working for the BC Wildfire Service, we experienced a transformation of philosophies in aerial firefighting. Our airtanker program was very much land-based biased. The use of amphibious aircraft was limited to periods of severe fire activity when we would periodically receive such aircraft from other agencies through mutual aid agreements. The use of retardant was the mainstay of our approach to aerial wildfire response until this exclusive approach no longer met the growing expectations of the wildfire agency.
As we continued to experience more fire seasons that challenged our conventional tactics, we transitioned to a more balanced approach that recognized the complimentary role of amphibious aircraft within the fleet. We modified our tactics to follow a playbook that involved quick response to wildfires with land-based airtankers, dropping retardant along the fire perimeter to create a temporary containment line. Once complete, subsequent action with amphibious aircraft was undertaken, delivering vast amounts of suppressant directly onto the flames, decreasing intensity and reducing spotting potential outside of the retardant box. This approach bore fruit and allowed our aerial fire fighters to catch fires they would not have been successful actioning previously.
The transition of approaches continued to evolve and has become more sophisticated. The historical approach of retardant followed by suppressant has shifted into a strategy of delivering retardants and suppressants simultaneously. This strategy has been born from an acceptance that both suppressants and retardants on their own have limitations on their efficacy during extreme wildfire conditions and elevated fuel moisture indices. Aerial operations on wildfires now often involve land-based airtankers building retardant lines along a fire perimeter in between amphibious airtanker drops to reduce fire intensity proximal to the freshly constructed retardant line. Success is being realized in reducing spotting and being able to immediately suppress spot fires that develop outside of the retardant line. Furthermore, this hybrid approach has enabled airtanker resources to be re-tasked from a current mission to an emerging new wildfire while still maintaining aerial support for the initial incident. The successful integration of the two airtanker types within wildfire airspace has compelled the wildfire management agency to embrace a more balanced fleet composition, resulting in the current fleet that is approximately half amphibious/half land based.
The story of BC’s transition to a balanced fleet model is not a unique narrative. Wildfire agencies throughout the world are challenged to adapt to changing wildfire regimes and their various negative impacts. Airtanker assets are an exceptionally powerful tool in responding to unwanted wildfires and careful consideration should be given to how their use can be optimized to create the best outcomes. Establishing a balanced approach to fleet characteristics that enables simultaneous suppressing and retarding of wildfires is a proven means of increasing likelihood of success and adaptation to an escalating challenge. For many agencies, the uncertainty is no longer about whether to undertake a land-based retarding approach to wildfire response, or an amphibious suppressant approach. Rather, the challenge is how to optimize a balance using both of these approaches within fleets, based on jurisdictional realities to achieve the best outcome.