Aerial Wildfire Suppression Model

1. Introduction

This document describes the computational model and data sources underlying the Aerial Wildfire Suppression Simulator. The model compares cumulative water or fire retardant delivery over time between two operational modes: conventionally manned helicopter fleets and fully autonomous (uncrewed) helicopter fleets.

The central hypothesis is that autonomous systems gain a decisive throughput advantage from two sources: (a) near-zero startup latency when a fire call is received, and (b) the ability to fly through the night, bypassing the sunset-to-sunrise grounding window that constrains manned aerial firefighting operations.

The model is parameterized so that users can vary scenario conditions (distances, fleet composition, time of day, season) while holding aircraft performance data fixed at sourced values. It is intended for rapid trade-space exploration, not as a certified operational planning tool.

2. Aircraft Performance Data

The following table summarizes the key performance parameters for each aircraft modeled. Values are drawn from U.S. Forest Service contract rate sheets, DoD FY2025 reimbursable rate publications, manufacturer specifications, and trade press reporting.

3. Operating Cost Data

Operating costs vary significantly depending on whether the operator is military, government contractor, or commercial. The model uses the USFS contract rate as the baseline, which bundles fuel, maintenance reserves, insurance, and overhead into a single hourly rate.

For autonomous operations, the model uses the same hourly airframe cost but eliminates the crew component. In practice, autonomous operations would require ground control operators, but at a substantially lower ratio (one operator supervising multiple aircraft vs. two pilots per aircraft). The model does not currently break out the ground control cost separately; this is a conservative simplification that slightly favors the manned case in cost comparisons.

4. Computational Model

4.1 Timeline

The simulation advances in discrete 1-minute time steps from the moment the fire call is received (t = 0) through the end of the specified simulation duration. Each aircraft independently progresses through a state machine with the following phases:

• Phase 1 — Startup: Manned crews require a configurable delay (default 20 minutes) for crew notification, mission briefing, walk-around preflight, and engine start. Autonomous aircraft require only an automated systems check (default 3 minutes).
• Phase 2 — Transit: One-way flight from base to the fire area at cruise speed. Transit time = D_base / v_i.
• Phase 3 — Sortie Cycling: Once on station, the aircraft cycles between the water source and the fire drop zone. Each cycle: transit to water source, fill time, transit back, approach and drop. Total cycle time = 2 × (D_water / v_i) + t_fill + t_drop. At the completion of each cycle, C_i gallons are added to the cumulative delivery total.
• Phase 4 — Grounded (manned only): From 30 minutes before sunset through 30 minutes after sunrise, manned aircraft are grounded. When the grounding window ends, a 10-minute re-startup delay is applied.
• Phase 5 — Maintenance (autonomous only): Every 6 flight hours, autonomous aircraft undergo a 30-minute automated maintenance check (fluid levels, sensor calibration, structural inspection). This is a conservative assumption.

4.2 Cumulative Delivery Function

For a fleet of N aircraft, the cumulative delivery at simulation time t is:

where n_i(t) is the number of completed sorties by aircraft i at time t, C_i is its per-sortie capacity, and λ is the payload factor (1.0 for water, 0.90 for retardant).

4.3 Cost Accumulation

Total cost accumulates for each aircraft during active flight phases (transit and cycling). Grounded and maintenance time do not accrue flight-hour costs. The marginal cost per gallon at time t is:

This metric converges over time as fixed startup costs are amortized across more sorties.

5. Night Flying Constraint

Aerial firefighting operations are traditionally restricted to daylight hours. The restriction is not regulatory per se — the FAA permits night helicopter operations for IFR-rated pilots — but is an operational safety policy enforced by wildfire management agencies. The primary concerns are:

• Terrain collision risk: Firefighting requires low-level flight in mountainous, smoky terrain where visual obstacle avoidance is critical.
• Ground crew safety: Water drops can injure or kill ground firefighters who are harder to see at night.
• Drop accuracy: Without visual reference to the fire perimeter, drop placement degrades significantly.

Recent developments in NVG-equipped operations (Coulson Aviation, Kachina Aviation, McDermott Aviation) have demonstrated that night aerial firefighting is operationally feasible with proper equipment and training. However, these programs remain limited in scope and are not available for general deployment in most U.S. states, including Texas.

The model assumes manned aircraft are grounded from 30 minutes before sunset to 30 minutes after sunrise. In central Texas (Bryan/College Station area), this window ranges from approximately 5.5 hours in June to approximately 10.5 hours in December. This grounding window is the single largest driver of autonomous advantage in the model.

Autonomous helicopters, equipped with FLIR, LiDAR, and computer vision, can operate through the night without the crew safety and visibility constraints that ground manned operations. This is the core value proposition of the autonomous wildfire suppression concept.

6. Model Variables

7. Limitations and Assumptions

This model makes several simplifying assumptions that should be understood when interpreting results:

• Constant cruise speed: The model does not account for wind, altitude-dependent performance, or the speed penalty from slung bucket loads. Actual delivery rates will be lower in adverse conditions.
• Instantaneous loading/unloading: Fill and drop times are modeled as fixed durations. In practice, these vary with water source depth, approach geometry, and drop pattern requirements.
• No refueling: The model does not account for fuel stops. UH-60 endurance is approximately 2.3 hours; CH-47 endurance is approximately 2.5 hours. For long simulation durations, actual sortie rates would be lower. This affects both modes roughly equally.
• Single water source: The model assumes a single water source at a fixed distance. Real operations may use multiple sources or require extended search for suitable dip sites.
• No weather effects: Smoke, wind, turbulence, and precipitation are not modeled.
• Autonomous technology readiness: The model assumes autonomous helicopters achieve equivalent drop accuracy and safety to manned operations. This represents a future state; current autonomous helicopter technology (e.g., Sikorsky MATRIX, Kaman K-MAX UAS) has demonstrated cargo delivery but not yet operational firefighting.
• Equal operating cost: Using the same airframe hourly rate for autonomous operations is conservative. Autonomous operations would likely have lower per-hour costs due to elimination of crew salaries and reduced insurance premiums.

8. Data Sources

1. U.S. Forest Service, "Helicopter Services — Awarded Flight Hour Rates," 2018-2021 contract rate sheet.
2. Office of the Under Secretary of Defense (Comptroller), "FY 2025 Reimbursable Rates," effective October 1, 2024.
3. Vertical Magazine, "Western Firefighter: Helinet Aviation's UH-60A Black Hawk," August 2020.
4. Vertical Magazine, "CH-47D Chinooks: A Formidable Tool for Firefighting Missions," January 2024.
5. U.S. Forest Service, Missoula Technology and Development Center, "Ground Pattern Performance of the National Guard Black Hawk Helicopter," Technical Report.
6. Coulson Aviation / Vertical Magazine, "Coulson's CU-47 is Ready for the Fire Fight," May 2020.
7. AerialFire Magazine, "Night Aerial Firefighting — Taking the Fight 24/7," March 2020.
8. Aerospace America / AIAA, "Taking the Fight to the Night," 2022.
9. Santa Barbara County Fire Department, "CH-47 Chinook" specification sheet.
10. U.S. Government Accountability Office, military aircraft operating cost per flight hour report.