Simulating the Aerial Ballet: The Dance of Fire-Fighting Planes and Helicopters ^†

Abstract

This study introduces a simulation model to analyze the efficacy of different aerial firefighting strategies in Finland, focusing on the comparative water production capacity and associated costs of firefighting aircraft versus helicopters of varying sizes. By utilizing publicly available data and direct inquiries, the model evaluates the impact of water collection distance on the volume of extinguishing water procured and its costs. The simulation reveals that firefighting aircraft offer a cost-effective solution, particularly when collecting water from distances of thirteen kilometers, where their cost per liter of water aligns with that of smaller helicopters operating closer to the fire zone. The study underscores the importance of precise data input into the calculator, highlighting the potential of aerial firefighting strategies in enhancing wildfire suppression efforts.

1. Introduction

During the summer months, a principal responsibility of the Finnish rescue services encompasses the management of wildfire incidents. The process of extinguishing extensive wildfires represents a labor-intensive and complex endeavor, often stretching the capabilities of regional rescue operations to their maximum. The objective is to detect wildfires at an incipient stage through aerial surveillance, particularly when the forest fire index is elevated. Additionally, recent advancements have seen an increased reliance on satellite technology for the identification of wildfire locations.

Wildfires frequently occur in terrains that are challenging to navigate, which hampers the swift mobilization of rescue operations to the inception points of fires. In such contexts, the strategic value of aerial firefighting techniques becomes pronounced. Aerial approaches enable the rapid containment of fire perimeters that are inaccessible to ground-based firefighting units. Rescue Academy experience demonstrates the efficacy of aerial firefighting in constraining the spread of fires, effectively serving as an interim measure until ground forces can deploy to the site. It is important to note, however, that the complete suppression of wildfires seldom relies solely on aerial tactics; it necessitates the direct, manual extinguishment efforts of firefighting personnel on the ground.

Aerial firefighting efforts in Finland have historically relied on helicopters equipped with the so-called Bambi bucket system [1,2]. The Border Guard and the Defense Forces supply helicopters for the primary aerial fleet. Additionally, the Lapland rescue service operates and deploys an Aslak rescue helicopter for firefighting missions. The fleet typically includes smaller Koala helicopters as well as the larger Super Puma and Augusta helicopters. The Defense Forces primarily use the heavier NH90 helicopters in a support role. For its operations, Lapland’s Aslak employs two light helicopters, the MB105 and the Eurocopter H125. The water-carrying capacity of these helicopters varies with their size; smaller helicopters have the capability to transport 500–1000 L of water per sortie, while larger helicopters can carry 1500–2000 L, contingent upon the helicopter’s weight and the air density.

In recent years, Sweden has augmented its wildfire suppression capabilities by acquiring two Air Tractor firefighting aircraft, a model frequently employed in southern European nations where wildfires are a recurrent challenge during the summer months. Finland possesses the option to solicit assistance from Swedish aerial firefighting resources, a consideration exemplified during the Kalajoki wildfire in the summer of 2021. To date, Finland’s experience with utilizing firefighting aircraft remains relatively limited.

Within this analytical framework, we have developed a mathematical model to compare the water production capacity and associated costs per unit time for a firefighting aircraft and two helicopters of disparate sizes.

The model incorporates the hourly operational costs of various aircraft and simulates their water production capacities based on water intake points situated at varying distances. Furthermore, the model enables the evaluation of the firefighting water yield between an airplane and a helicopter when utilizing distinct water intake points located at differential distances. We also use this modeling calculator in real life to evaluate the choice between the domestic helicopter fleet and possibly adding an Air Tractor fleet from Sweden.

2. Data and Used Methods

The foundation of the optimization simulation leverages publicly accessible data regarding the technical specifications, including the water carrying capacities, of the helicopter and aircraft fleet designated for wildland firefighting missions [3]. In the process of compiling this study, we directed formal inquiries to the Ministry of the Interior’s rescue department. This department, in collaboration with the Regional Administration of Northern Finland, orchestrates the national strategy for aerial firefighting efforts. Additionally, we extended communication to the Uti Jaeger Regiment, the entity overseeing the operation of the ground forces’ helicopter fleet, to gather data on the hourly operational costs associated with various aircraft. Furthermore, specific requests yielded information on the hourly expenditure for aerial firefighting operations conducted by the Lapland rescue service’s Aslak helicopter, specifically for the MB105 and H125 helicopter models.

This study employed the computational functionalities of Microsoft Excel 2016 to construct formulas that compute various metrics based on input numerical values. These calculations include the operational costs of each aircraft type, incorporating both the transfer flight and the actual firefighting efforts; the hourly water production capacity from a water source at a predetermined distance for each aircraft; and a comparative analysis of these factors. The objective of the simulation was to analyze the cost differential between a firefighting aircraft and a helicopter, juxtaposing this with the relative firefighting efficacy. Furthermore, the research examined the impact of utilizing two distinct water intake locations (one optimized for helicopters and the other for fixed-wing firefighting aircraft) on the volume of extinguishing water delivered by different aircraft types and the cost per liter of water derived.

3. Model Description

The operational capabilities and economic parameters of aerial firefighting assets are delineated as follows:

• Light helicopters, such as the Koala and MB105 models, possess a maximum water carriage capacity of 1000 L. The operational expenditure for firefighting missions is estimated to range between EUR 5000 and 6000 per hour. These helicopters can achieve a cruise velocity of approximately 200 km per hour unladen, which decreases to 80–100 km per hour when laden with a water payload.
• Intermediate helicopters, exemplified by the NH90 and Super Puma models, are equipped to transport up to 2000 L of water. The cost associated with their use for firefighting operations is approximately EUR 20,000 per hour. Similar to light helicopters, their speed without a load is about 200 km per hour, reducing to 80–100 km per hour when carrying water.
• Fixed-wing firefighting aircraft, specifically the Air Tractor, have the capability to extract and carry 3000 L of water in a single operation from aquatic sources. The financial requisition for their deployment on firefighting tasks is around EUR 3000 per hour. The Air Tractor maintains a travel speed of about 200 km per hour when not burdened by a load, which modestly reduces to approximately 120 km per hour with a full water load.

Leveraging a foundation of critical variables alongside established cost and performance metrics, an optimization framework was constructed, employing expressions and functions within Excel software 2016. This framework facilitates the incorporation of a broad spectrum of parameters that influence the efficacy of firefighting operations (notably, water production), in addition to elements that impact the financial outlay associated with such activities.

The output of the fire-fighting water yield from the developed calculator was benchmarked against a water yield table for helicopters, which was formulated as part of a thesis on aerial firefighting conducted at the Rescue College. This comparative analysis revealed that the calculator yielded marginally lower water quantities per hour compared to the data delineated in the thesis. It is important to note, however, that the thesis acknowledges the theoretical nature of its calculations, admitting to an over-optimistic representation relative to real-world scenarios. Considering this acknowledgment, it can be deduced that the calculator we devised offers a realistic approximation of the actual water production capacities of aircraft engaged in firefighting operations.

The evaluation underscored the imperative for meticulous definition of the variables input into the calculator. Notably, minor alterations in the input data for aircraft velocity markedly influence the frequency of sorties conducted per hour between the water collection point and the fire suppression zone. Such variations consequentially exert a significant effect on both the volumetric water yield and the associated costs relative to the volume of water dispensed. In the context of helicopters, the analysis incorporated considerations for the operational necessity of maintaining elevated velocities when laden with a full water load and reduced speeds when unburdened. For fixed-wing firefighting aircraft, a reduced speed parameter was designated as the operational velocity when fully loaded; this adjustment facilitates the pilot’s ability to navigate the aircraft more slowly and accurately along the designated discharge trajectory, leveraging flaps to modulate speed.

Within the framework of the calculator, bespoke columns were integrated to facilitate the inclusion of fixed maintenance costs into the comprehensive calculation. Furthermore, these columns enable the estimation of maintenance requirements during the midpoint of the extinguishing operations, alongside the duration such maintenance might necessitate. Moreover, supplementary rows were meticulously devised within the apparatus to accommodate the input of potential future additions to the equipment roster; see the illustration in Figure 1.

4. Analysis of Aerial Firefighting

The developed computational model was employed to analyze the efficacy of aerial firefighting strategies across three distinct wildfire suppression scenarios:

• In the initial scenario: the firefighting efforts are undertaken by a fleet comprising a compact helicopter (Koala), a substantial helicopter (NH90), and an aircraft (Air Tractor), with each aerial vehicle procuring water from a location situated one kilometer distant from the fire zone. See Figure 2.
• The second scenario delineates a similar composition of firefighting apparatus, involving a compact helicopter (Koala), a substantial helicopter (NH90), and an aircraft (Air Tractor). In this arrangement, the helicopters are tasked with water retrieval from a proximate one-kilometer distance, whereas the Air Tractor is designated to source water from a more remote location, six kilometers away. See Figure 3.
• The third scenario maintains the same ensemble of aerial firefighting vehicles; however, it introduces a variation in the water-sourcing strategy for the Air Tractor, which, in contrast to the helicopters that continue to obtain water from a one kilometer distance, is required to extend its retrieval operations to a location thirteen kilometers away from the fire zone. See Figure 4.

This approach provides a structured framework for assessing the operational dynamics and logistical implications of water sourcing distances on the efficiency of aerial firefighting tactics in varying wildfire contexts.

The scenarios facilitated an examination of the aircraft’s water production capacity. It was particularly noted that the water production of the Air Tractor aircraft, the most efficient of the three types of aircraft, decreases to match that of the Koala helicopter. This phenomenon occurs as the water collection distance increases, even though the Koala helicopter, generally used in extinguishing work, is less expensive than the NH90 helicopter. This happened in scenario 2, where the Air Tractor fetched water from a distance of six kilometers at the same time as the Koala helicopter fetched water from a kilometer away. At this point, the water yield of the two aircraft was the same, but the cost per liter of water was more expensive for Koala due to the expensive operating costs of the helicopter.

The examination persisted through to the third scenario, wherein the Air Tractor was tasked with procuring water from a distance of 13 km, juxtaposed with the helicopters, which sourced water from an additional distance of 1 km. At this juncture, it was observed that the water production capacity of the Air Tractor had diminished to merely half of the yield synonymous with the Koala. Concurrently, the cost per liter of water facilitated by the Air Tractor escalated to parity with that of the water liter produced by the Koala helicopter.

5. Discussion

In this study, a simulation model was introduced, designed to facilitate comparative analysis of the water production capacity between airplanes deployed for wildfire suppression and helicopters of varying sizes, contingent upon the distance of water collection. Additionally, the model computes the impact of said distance on the correlation between the volume of extinguishing water procured and the associated costs. Noteworthy assistance for this research was garnered from publications within the aviation and rescue sectors, augmented by direct inquiries for information to the Uti Jaeger Regiment, the Ministry of the Interior, and the rescue helicopter Aslak in Lapland. Utilizing the data acquired, it was feasible to identify the critical variables requisite for the construction of the model.

The construction of the calculator itself presented a formidable challenge due to the complexity involved in formulating various equations and managing the associated multitude of variables. Following several test runs, the calculator was capable of generating credible water flow figures, which aligned with values presented in other scholarly literature. The utility of the calculator underscores the importance of precision and necessitates a comprehensive understanding from the user regarding the veracity of the input values. Incorrect data, such as erroneous speed information, can significantly distort the simulations, with the magnitude of the error compounding as the time function increases.

The principal objective of this study was to assess the cost-effectiveness of utilizing a firefighting aircraft versus a firefighting helicopter. The simulation results unequivocally indicate that the firefighting aircraft, in terms of delivering water to the affected area, achieves a level of cost-effectiveness that is sixfold superior to that of the Koala-type firefighting helicopter. It was observed that when an aircraft collects water from a distance of thirteen kilometers, its water output decreases to half that of a helicopter. However, at this specific distance, the cost per liter of water produced aligns with that of a small helicopter operating at a proximity of one kilometer from the fire zone. Although the simulation also incorporated data for the larger NH90 helicopter, its higher operational costs rendered comparisons most pertinent between the more economical, smaller helicopter and the aircraft. The NH90 helicopter, with its substantial two-thousand-liter water capacity, is capable of generating a significant water flow at shorter collection distances. Nevertheless, the cost per liter of water remains considerably high, attributed to the aforementioned elevated operational expenses.