Researchers performed calculations to determine how many drones would be needed for attacking a wildfire

swarm of collaborative UAVs fire
Figure 1. (a,b) Representations of the proposed firefighting system based on the use of a swarm of collaborative UAVs. (From the research)

The person who was awarded a patent in 2017 for describing a system of drones that could be used to drop liquids on wildfires wrote a paper earlier this year with two other authors that claims to have determined how many drones would be needed for suppressing a small section of a fire.

The patent, #WO2017208272A1, awarded to Marco Ghio, is quite vague and does not supply any technical details. It says that instead of applying fire retardant or water in a conventional manner, a “rain” concept would be used:

Dropping small quantities of firefighting liquid or drizzling it over the fire, and its subsequent spreading on a large area instead of in a concentrated manner. This method, both theoretically and experimentally, is acknowledged as being particularly effective, whereas, on a practical level, it is effectively used in domestic and/or industrial firefighting systems.

swarm of collaborative UAVs fire
Diagram from the patent

In the United States fire retardant dropped from an approved air tanker is applied at coverage levels ranging from 1 to 9 gallons per 100 square feet, depending on the situation. It is not clear what coverage level “rain” would produce.

Drawing from the patent drones firefighting
Drawing from the patent

The patent specifies that drones would transport the liquid in removable containers. Upon returning empty to the mobile base the containers would be autonomously replaced with full containers, along with a charged battery if needed.

The drones and the other equipment would be transported in standard metal shipping containers which would be strategically positioned. The system would include “a control unit for the coordination of missions, the flight paths to be followed, and the selection of the ideal drop points optimized according to the environmental conditions.”

Details about how all of this would be accomplished are not specified.

The patent and the research paper written by Mr. Ghio,  Elena Ausonio, and Patrizia Bagnerini assumes that the cargo capacity of the drones would be 5 to 50 liters (1 to 13 gallons), much less than currently carried by helicopters (up to 3,000 gallons) and fixed wing aircraft (up to 17,500 gallons) that routinely fight wildfires.

Their analysis (below) takes into account wind speed, flame length, the length of fire line to be suppressed, and the dead fuel moisture. It indicates that about 75 linear meters (246 feet) of the fire’s edge could be extinguished with 120 drones each carrying 20 liters (5 gallons) or 80 drones carrying 30 liters (8 gallons). The vegetation is assumed to be grass or brush, but not timber. The example below assumes that the wind speed is 20 km/hour (12 mph) and the dead fuel moisture is 18 percent. A moisture content of 18 percent for 1-hour and 10-hour time lag fuels is quite high for a very active wildfire. It should not be very difficult to suppress a  fire under those fuel conditions.

Number of drones needed to suppress wildfire
Figure 4a shows the linear meters of fire that can be arrested by using the firefighting system. For example, approximately 70–75 linear meters of active front can be extinguished with 120 drones each carrying 20 L or with 80 drones carrying 30 L. Assumptions are that the wind speed is 20 km/hour and the dead fuel moisture is 18 percent. (from the research)

Our take

In my opinion the most difficult part of using drones to assist firefighters would be applying the retardant or water at the exact location where it can be useful. That is difficult enough when you have good communication with ground personnel, adequate aerial supervision, and experienced highly qualified air crews in helicopters or air tankers.

I don’t think the principle of “rain” in the application of retardant or water from dozens or hundreds of drones is a thing, at least when you’re talking about drones that can just carry a few gallons of water and must have the batteries replaced every 20 minutes. The suppressant still has to be delivered in a timely manner in a quantity and at the location where it can be useful. Maybe when drones are carrying 50 to 100 gallons of water, and the technology improves for placing the retardant on target, it might be useful in very remote areas when the fire is very small, less than 1/10 of an acre, and the wind speed does not exceed 5 mph.

Rain Industries is working on an Unmanned Aerial System (UAS) that could carry up to 400 pounds of cargo, or 50 gallons of water.

Drone Amplified, the developer of the IGNIS prescribed fire system currently being used for aerial ignition, and Parallel Flight Technologies, have received a $650,000 grant from the US Department of Agriculture to support further development of a large-scale Unmanned Aerial System (UAS) for prescribed fire. Parallel says their hybrid gas/electric UAS can carry 100 pounds for up to two hours, numbers that are much larger than battery operated drones. When paired with the upgraded aerial ignition payload under development which will hold and dispense 3,500 incendiary spheres, it will have eight times the payload carrying capacity of drones being used today, and ten times the flight duration.

The paper was published by MDPI, which is food for thought.

Aircraft formerly known as the SuperTanker spotted in Hawaii

And, photos of a wildfire in Hawaii

N936CA, formerly Tanker 944
N936CA, formerly Air Tanker 944, now owned by National Airlines. Photographed in Hawaii by Hiroshi Ando Nov. 4, 2021.

These photos were taken by Hiroshi Ando who was one of the drop system operators on Global SuperTanker Services’ 747 SuperTanker, Tanker 944. Earlier this year the company shut down and sold the aircraft to National Airlines, who re-registered it as N936CA and is using it as a freighter. Hiroshi shot the photo above earlier this month when the aircraft was in Hawaii. He said he has spotted the plane a few times there while it was flying on military cargo flights.

Logistic Air purchased the retardant delivery system that was in the SuperTanker and has plans to install it in a nose-loading 747-200 when the aircraft completes maintenance after the first of the year. Their website for the aircraft says “Returning to Service in 2022.”

The day after Thanksgiving, November 26, a wildfire north of Honolulu, Hawaii threatened structures near Kalana Drive and Alu Street. After the report was received around noon 12 pieces of apparatus staffed with about 34 personnel responded.

Wildfire north of Honolulu, Nov. 26, 2021
Wildfire north of Honolulu, Nov. 26, 2021. Photo by Hiroshi Ando.

Two helicopters owned by the City and County of Honolulu assisted firefighters by dropping water that was dipped out of a swimming pool at Kalihi Valley District Park.

Hiroshi said the fire north of Honolulu started about four hours after Coulson’s C-130 Air Tanker 131, N131CG, departed Hilo after the crew stopped to spend the night on their ferry flight from the US West Coast on their way to begin a firefighting contract in Australia for the country’s 2021/2022 bushfire season.

Wildfire north of Honolulu, Nov. 26, 2021 helicopter drops water
MD 500N helicopter, owned by the City & County of Honolulu, working on a wildfire north of the city. Photo by Hiroshi Ando, Nov. 26, 2021.

In a news release the Honolulu Fire Department described the fire as “large scale, rapidly spreading” driven by wind. They said it burned about four acres.

Wildfire north of Honolulu, Nov. 26, 2021 helicopter drops water
MD 500N helicopter, owned by the City & County of Honolulu, dips water out of a swimming pool while working on a wildfire north of the city. Photo by Hiroshi Ando, Nov. 26, 2021.
Wildfire north of Honolulu, Nov. 26, 2021 helicopter drops water
MD 500N helicopter, owned by the City & County of Honolulu, working on a wildfire north of the city. Photo by Hiroshi Ando, Nov. 26, 2021.

In 2018 Hiroshi sent us photos he took of the Holy Fire while the SuperTanker was working on the fire which burned more than 22,000 acres northwest of Lake Elsinore, California.

It is dry in Hawaii. The Drought Monitor classifies conditions in the state as ranging from abnormally dry to extreme drought.

Hawaii Drought Monitor, Nov. 23, 2021
Hawaii Drought Monitor, Nov. 23, 2021

C-130 designated for CAL FIRE stops by McClellan, stripped of paint

Coast Guard number 1714

Former Coast Guard C-130, 1714
Former Coast Guard HC-130H, 1714, at McClellan, Nov. 17, 2021. Tanker 118 is behind it. Photo by Mike McKeig.

One of the seven Coast Guard HC-130Hs that may eventually be transferred to the California Department of Forestry and Fire Protection (CAL FIRE), Coast Guard number 1714, returned to Sacramento McClellan Airport this month. The last time it was seen there was quite some time ago when it was still in Coast Guard livery. When it flew in from Ogden, UT on November 2 it had been stripped of paint. It is likely that the aircraft had been under the care of the 309th Aircraft Maintenance Group at Ogden Air Logistics Complex at Hill Air Force Base.

Mike McKeig got a photo of 1714 at the end of an engine run on November 17, two days before it departed for Roswell, New Mexico.

If the Air Force completes the maintenance and conversion into air tankers as Congress required in legislation passed December 20, 2013, the seven Coast Guard HC-130H aircraft will be transferred to CAL FIRE. They were originally destined for the U.S. Forest Service to be government-owned and privately-operated. But oddly, the agency lost interest and now they will be regifted to CAL FIRE if the Air Force follows through as required. Actually, all seven are still property of the Coast Guard and won’t be transferred over until all of the work is done. In the meantime, CAL FIRE is using at least one to train crews. At news conferences they take every opportunity to have one with the new CAL FIRE livery featured prominently in the background.

Organizing for night-flying firefighting operations, U.S. and Australia

What guidelines are in place?

National Night Air Operations
Image from National Night Air Operations presentation, 2018, USFS.

The investigation into the fatal crash of the Single Engine Air Tanker, that occurred in Colorado 1 hour and 49 minutes after sunset on November 16, will include an evaluation of the guidelines that had been established for night-flying operations. Approximately 90 percent of the Kruger Rock Fire was on the Roosevelt National Forest; the rest was on land where the responsibility for suppression was with the Sheriff of Larimer County. The day after the crash the Sheriff’s office said that as of 7 a.m. that day the fire was being managed by a unified command with the US Forest Service and the Sheriff.

Judging from the fire perimeter and the very strong westerly winds it appears likely that the fire started just outside or very close to the National Forest boundary and then spread into the Forest — which is tinted green in the map below.

Map of the Krueger Rock Fire
Map of the Krueger Rock Fire, Nov. 17, 2021. Green indicates National Forest. Fire perimeter created by Colorado’s Multi-Mission aircraft and crew.

After suspending their use of night-flying helicopters at night for about 40 years after a mid-air collision, the US Forest Service restored the program in 2013, making one helicopter available at night. Several other agencies in Southern California have long-standing night-flying programs.

FIRESCOPE is an organization of local fire departments, the California Department of Forestry and Fire Protection, and federal fire agencies. In 2018 they published “FIRESCOPE Fire Suppression Night Flying Guidelines”, ICS 800. The 28-page document “provides guidelines for the use of interagency aircraft for both night initial and extended attack operations on emergency incidents to enhance safety, operational effectiveness, and fiscal prudence.”

After operational trials, the state of Victoria in Australia first placed a crew on shift for helicopter night firefighting operations on December 7, 2018. Within two weeks they had two night-flying firebombing helicopters on active contracts (Sikorsky S61N and a Bell 412), each with a supervising  helicopter (Sikorsky S76B and AS355 F2, respectively). An update on their program at the time described some of the procedures and guidelines, including their “crawl, walk, run philosophy” as the project was unfolding.

Thanks and a tip of the hat go out to Cameron.

Aerial firefighting program on PBS

Shahn Sederberg, Behind the Wings

A program that aired on the Rocky Mountain Public Broadcasting System looked at fire aviation in the Western US. It featured the California Department of Forestry and Fire Protection, Los Angeles County, Interra (which manages fire data and intelligence), and United Rotorcraft which converts Blackhawks helicopters into water-dropping Firehawks. Most of the 27 minutes is spent talking about helicopters, and they mention that the state of Colorado is going to purchase a Firehawk.

This episode of Wings Over the Rockies  is dedicated to Marc “Thor” Olson, the pilot with CO Fire Aviation who was killed November 17 while on a night-flying mission over the Kruger Rock Fire near Estes Park, Colorado. We see him explaining the use of night vision goggles and fighting fire from the air at night.

Thanks and a tip of the hat go out to Tom.

Former Naval aviator’s thoughts about the fatal air tanker crash on the Kruger Fire

Kruger Fire 3-D map
Kruger Fire (in red) 3-D map, approximate location. Looking north.

(Note from Bill: Bean Barrett, a frequent contributor to Fire Aviation, spent a career in U.S. Naval  Aviation as a fighter pilot and served on the Navy Staff as a program sponsor responsible for planning, programming, and budgeting. He was also a Naval Aviation Safety Officer trained in mishap investigation.  Here are some of his thoughts about the fatal crash of the AT-802 single engine air tanker on the Kruger Fire July 25, 2021.)

A blinding flash of the obvious to an old Naval aviator.

Having been in the business of personally flying and ordering flights in marginal conditions over my flying career, I offer the following observation derived from thinking about the mishap involving the SEAT at the Kruger Fire: This mission represented a near first for fire aviation in a very difficult  environment. There is little community experience to bolster command and operational decisions by IC’s and pilots operating in this environment.

From personal experience, flying in extraordinarily bad conditions at night at sea is only possible to undertake and successfully accomplish because there are thousands of hours and sorties worth of community experience that helps those responsible know when and where to draw the line.

In this case, regardless of the NTSB/FAA mishap findings, without a significant background of fire aviation community experience to draw on for a particular situation or environment, it is always best to operate conservatively and approach any new environment in steps, never do the hardest one first if at all possible.

I would hope that the mishap SEAT flight was the culmination of a “work up” from simple to complex tasking and flying over hundreds of hours of use of night vision goggles and night drops with the aircraft.

This underscores the requirement for the fire aviation community to develop/ expand standard training and operations procedures both for general ops and by specific aircraft type and mission. If everyone trains and operates to the same standards, community experience is more relevant, experience can be accumulated and shared, procedures modified and improved, and training requirements adjusted resulting in improved flight safety and operations.

How many folks in the IMT/ IC business are aware of the AT-802 flight safety record when they order a SEAT?

Over four mishaps a year since May, 1997. This should have set off alarm bells a very long time ago except there isn’t any agency “keeping score” for type aircraft mishap rate and mishap cause that then ties the information and “lessons learned” back to mandated changes in training, maintenance, and ops procedures. It is very apparent from looking over the reference that the mishap rate is unacceptable and it isn’t getting any better.

Absent mandated standardized training, maintenance, and operations procedures for the AT-802 (and all other fire aviation aircraft), unacceptable mishap rates will continue. Since the US government is the largest contracting organization, it would seem logical to mandate a comprehensive Federal standardization program for AT-802 SEAT’s and other fire aviation aircraft that will operate under government contract.

To expect a loose confederacy of contract aviation companies to cooperatively develop a program is wishful thinking.

Some may say that such a Federal program already exists but my reply would be “where is the dash 1 or NATOPS flight manual for each type of aircraft, how is it revised, and what single agency is responsible for the manuals, standardized training, standardized operations, and standardized maintenance?” It is obvious that today’s chop suey of regulatory agencies, regulations, requirements, and instructions is not working for fire aviation.

There will be complaints about the additional cost to institute a consolidated comprehensive standardization program that will save fire aviation lives, aircraft, and improve effectiveness but my answer would be … the option of continuing with business as usual is obviously unacceptable.

Until fire aviation has a comprehensive aviation program as good as the US military aviation programs, we can expect little change in the fire fviation mishap rates or in operational effectiveness.

Enhanced vision system being tested that could assist C-130 air tanker pilots

Can help navigate through smoke

Enhanced Vision System, C-130
Enhanced Vision System, C-130. Collins Aerospace photo.

(Press release from Collins Aerospace)

Collins Aerospace successfully completed a test flight proving the effectiveness of its Enhanced Vision System (EVS) on a C130J aircraft. EVS has, for many years, increased situational awareness on commercial and business aircraft. This latest milestone brings Collins closer to providing the same benefits to military customers across the globe.

Collins’ EVS-3600 uses multiple wave-length cameras to “see-through” poor visibility conditions better than the human eye. The images are shown on head-up displays, allowing pilots to better identify the runway environment in all weather conditions including fog, haze, snow, smoke, dust, blowing sand and low illumination nighttime operations. This technology is particularly beneficial for C-130 aircraft given its need in remote areas, its widespread use during natural disasters — such as wildfires — humanitarian relief efforts across the globe and search and rescue efforts.

“The feedback we received from the crew following the test flight confirms what we’ve known for quite some time — this technology can help save lives by improving threat detection while increasing safety margins and mission success rates for our militaries,” said Dave Schreck, vice president and general manager for Military Avionics and Helicopters at Collins Aerospace. “We’re particularly interested in seeing how this technology can assist firefighting crews. Not only will it help them to navigate through heavy smoke and pinpoint hotspots while using C-130s to help stop wildfires, but they can also land and refuel closer to the fires to increase the efficiency of their efforts.

In military operations, the EVS can also assist with:

  • Safer low profile terrain flying in low visibility conditions
  • Easier visual confirmation of Drop Zone markings
  • Fewer mission cancelations due to adverse weather conditions
  • Use of heat signatures to make search and rescue operations easier and more efficient

In addition, Collins’ EVS system is among the few solutions available that doesn’t need a dedicated cooling system and remains the most compact system certified for Enhanced Flight Vision System (EFVS) Approach and EFVS Landing lower operating minima.

Collins is currently working with Air Mobility Command on a longer, more comprehensive test of the EVS System and is on track to complete the prototype aircraft installation and airworthiness approval in 2023. The upgrade package is expected to be immediately available to the C-130J community thereafter.

Thanks and a tip of the hat go out to Gerald.

Winds were strong when the air tanker crashed at the Kruger Fire

The Larimer County Sheriff’s office ordered the aircraft, using a “verbal contract” agreed to a month before.

1:30 p.m. MST Nov. 18, 2021

Weather data from Estes Park RAWS, ESPC2
Weather data from Estes Park RAWS, ESPC2. The last observation shown is at 2224 MST Nov. 16, 2021. The observations at the arrows were 12 minutes before the last detected location of the aircraft.

Around the time Single Engine Air Tanker 860 crashed at the Kruger Rock Fire in Colorado at approximately 6:36 p.m. MST on November 16, killing pilot Marc Thor Olson, the Estes Park ESPC2 Remote Automatic Weather Station recorded sustained winds of 13 mph gusting to 32 mph out of the west. The station is 3.7 miles northwest of the fire at 7,892 feet and its anemometer is 20 feet above the ground.

N802NZ, last 10 minutes of flight tracking data
N802NZ, last 10 minutes of flight tracking data, Nov. 16, 2021. Note that the times are CST. FlightAware.

Looking at the flight tracking log from FlightAware above, the wind appeared to be much stronger at the plane’s altitude, which was 8,950 to 10,450 feet while it was over the fire. The highest peak just south of the fire is at 9,400 feet.

Map of the Krueger Rock Fire
Map of the Krueger Rock Fire, Nov. 17, 2021. Colorado’s Multi-Mission aircraft and crew.

As it made four orbits near the fire during the 10 minutes it was in the area, the ground speed of T-860, an Air Tractor 802A (N802NZ) varied from a low of 82 mph while flying west to a maximum of 200 mph when east-bound. These shifts in ground speed were consistent during all four orbits. This indicates a very strong wind out of the west, a direction that is consistent with the data from the weather station.

The last flight of Tanker 860 N802NZ
The last flight of Tanker 860, N802NZ. The flight originated at Northern Colorado Regional Airport. Note that the times are in CST. FlightAware.

There are two reasons that fixed wing air tankers avoid attacking wildfires during strong winds. One, the wind makes it difficult or impossible for the retardant to hit the target, getting blown horizontally as it falls from the aircraft to the ground. Second, flying low and slow, as air tankers have to do, is difficult in mountainous terrain with calm winds, but it can be extremely hazardous during strong winds.

When you add a third complexity of dropping at night using night vision goggles, something that has been done very little in the history of aviation, and never before in Colorado, the pilot had the deck stacked against him. With the strong wind, the chances of stopping or slowing the spread of the fire with retardant, water, or any other suppressant, were very, very slim. (There is a report that the operator of the aircraft, CO Fire Aviation, experimented with night drops in Oregon in 2021.)

The weather forecast available from the National Weather Service that Tuesday afternoon called for continued very strong winds until sundown and a chance for snow Tuesday night. It predicted dry weather on Wednesday and Thursday with high temperatures in the 30s and 40s under mostly sunny skies with the relative humidity around 20 percent. The wind chill was expected to be below zero from Wednesday afternoon until Thursday afternoon. The actual low temperature Tuesday night turned out to be 11 degrees.

Risk vs. reward

With 20/20 hindsight looking at risk vs. reward, this was a very high risk mission. The potential reward was little, considering the likely effectiveness of 700 gallons of suppressant blown off target by strong winds and the weather forecast of a chance of snow in a matter of hours and wind chills the next day below zero.

Who decided to attempt the night flight?

The short answer is, the Larimer County Sheriff’s office ordered the aircraft to respond to the fire, using a “verbal call when needed contract”, an arrangement that was first agreed to on October 5, 2021.

A preliminary map appears to show that the fire was just inside the boundary of the Roosevelt National Forest. The Larimer County Sheriff’s office said on Wednesday Nov. 17 that as of 7 a.m. that day the fire was being managed by a unified command with the US Forest Service and the Sheriff.

In Colorado, Texas, and Wyoming the local county sheriffs are given the responsibility for suppressing wildfires outside of cities unless they are on federal land. The Kruger Rock Fire was in Larimer County.

As Wildfire Today reported November 16, before the fatal flight, T-860 departed from the Fort Morgan, Colorado airport, orbited the fire about half a dozen times, then landed at Northern Colorado Regional Airport at 4:38 p.m. MST. This flight is listed in the image from FlightAware above as one of two flights that day for the aircraft. It turns out that on the first flight it dropped water on the fire, which the pilot reportedly described as “successful”. After it landed at Northern Colorado Regional Airport it reloaded with “fire suppressant” instead of water, and by 6:13 p.m. MST was airborne returning to the fire.

Sunset that day was at 4:44 p.m. MST. The air tanker disappeared from tracking at 6:35 p.m., about 1 hour and 49 minutes after sunset. Air tankers working for the U.S. federal government are allowed to drop only as late as 30 minutes after official sunset.

The Denver Post reported that CO Fire Aviation said in a statement, “There was no aerial supervision or lead plane required for the mission and weather and wind conditions were reported to be within limits of our company standard operating procedures.”

In the video below Juan Browne has strong feelings about this incident. Shortly after posting it, he wrote a comment saying, “GROUNDSPEED NOT AIRSPEED!”

Below is an excerpt from a statement released November 17, 2021 by the Larimer County Sheriff’s office:

Continue reading “Winds were strong when the air tanker crashed at the Kruger Fire”