Fighting Wildfires, California Style, Part 2 – In The Air

The Grumman S-2T Airtanker, the present-day workhorse of the Cal Fire air fleet.

This is Part 2 of the Cal Fire roster, covering the firefighting roles and aircraft types of the Cal Fire fleet of aircraft. The Cal Fire ground vehicles are covered in Fighting Wildfires, California Style, Part 1

The difficulty of ground access in much of California’s open back country, combined with the seasonal wildfire threat in the dry brushlands, means that firefighting strategies adopted air assets early on. Aircraft have been used to both observe and detect, and also to fight wildfires. Much like the ground wildfire fighting apparatus, California and other western states contracted for and employed all sorts of firefighting airplanes and helicopters, over time.

The “old school” way to detect and locate wildfires, by ground observation from fire lookout towers.

Traditionally, mountaintop observation or “lookout” towers have been used to detect wildfires. A device called an “alidade”, more specifically, an “Osborne Fire Finder”, was used to determine the exact compass direction of a fire from the lookout tower. Observations from two different towers can triangulate the exact position of the fire. The use of aircraft permit the site of the fire to be quickly determined, as well as the size and ferocity of the fire, from close-up aerial observation, thus somewhat obsoleting the alidades.

An alidade; more specifically, an Osborne Fire Finder. Sighting the smoke from a wildfire through the sights allows for triangulating the exact location of the fire.

Early on, slow and stable platforms were used to both observe and to fight fires. Typically, crop duster biplanes were adapted to the task. N3N biplanes were employed by the CDF (California Division of Forestry, later “Cal Fire” from 2007), as were Stearmans. Converted TBM Avenger dive bombers, with the addition of tanks to hold the fire fighting slurry, were used as well. The first CDF “on-call” contracts were made, with outside operators, in 1954. In 1958, the CDF contracted for full-time use of N3Ns, Stearmans, and TBMs. The biplanes could deliver 200 gallons of water or slurry per drop, while the TBM could carry 600 gallons per flight operation.

A converted TBM Avenger, making a slurry drop in the 1960’s.

Different forms of firefighting slurry were used. Initially, cans or large metal containers, filled with water or chemical concoctions, were dropped from above, and were expected to break open upon impact to smother the flames. The experiments did not work out well. Open dropping of liquids turned out to be the most effective form of aerial drop. An early use of boron compounds gave the firefighting aircraft the nickname of “borate bombers”, even though other compounds were substituted soon after. A clay-based slurry, as well as kelp-based varieties, were also tried out. Firefighters were looking for a reasonably economical and safe compound that would not only smother the flames upon application, as water does, but would also provide some sort of ongoing fire-retardant properties that outlasted the initial liquid drop. Ultimately, a phosphate-based compound was found to work the best. Yes, fertilizer, mixed with water, turns out to be a good and lasting fire suppressant. Later, the phosphorus helps the vegetation to vigorously grow back (which may or may not be a desired attribute, under the circumstances). A mix of one part phosphorus-based fertilizer, combined with seven parts water, seems to work the best. Red dye is added to the mix, to make more visible the slurry drops, as well as the exact locations of the applications on the ground.

A Stearman biplane making a water drop in 1955, in Mendocino County, CA. It appears to be a practice run.

In the 1960s, the CDF contracted for all sorts of aircraft, generally World War 2 surplus planes. Many of the WW2 bombers and light bombers in collections today served time as firefighting aircraft, which were then later returned to wartime specs and markings, after their tenure as firefighters were over. Firefighting was ideal for keeping the old bombers in shape, as the service did not add too many flight hours, but the planes got ongoing maintenance, and enough flight time, over the years, to keep the aircraft in good operating order. Like old cars, old airplanes suffer greatly from lack of use.

A B-17, owned by Evergreen Air, and under contract to the CDF. It is flying out of Hemet-Ryan Airport, a major hub for California firefighting aircraft. Note the replacement nose for the original clear piece, and the slurry stains along the bottom of the fuselage. Firefighting aircraft typically wear a unique (for the region) two-digit number on the tail, with the number sometimes repeated on either side of the nose. This is for easy identification of the plane during firefighting operations.

The F7F twin-engine aircraft, introduced to the U.S. military right at the end of WW2, were also employed by the CDF late in the 1960s, in a quest to find somewhat more substantial and newer firefighting aircraft, with fewer flight hours on them. Amphibious PBY Catalinas and larger B-17 bombers were also contracted for, especially after the horrendous 1970 fire season, which revealed huge gaps in the number and also the capabilities of both ground and aerial firefighting equipment. The movement for larger airdrop capacity as well as greater numbers of available aircraft gained momentum after the California fall fire season of 1970.

A twin-engine F7F, privately owned but under contract to the CDF in 1965, preparing for takeoff.

By the early 1970s, the biplanes had been retired, and the CDF air fleet consisted of about twenty TBMs and F7Fs. A small handful of PBYs and B-17s also passed through the CDF fleet. None of these planes were actually owned by the CDF, but instead were under full-time and part-time contract with CDF. Ownership, aircraft maintenance, and the provision of pilots were all done through outside contracted entities. A half dozen crashes of TBMs and F7Fs in 1973 and 1974 caused the CDF to review its way of doing things.

A PBY modified for firefighting. Paint jobs of the day were typically predominantly silver or white, with red or orange trim. Because the planes were privately owned by a number of companies, there was no standardization of paint schemes, number typefaces and proportions, or logos.

In 1972, the CDF first began working with the Grumman S-2 Tracker, a much more modern aircraft, equipped with twin engines. As the planes were moved off of the U.S Military rosters near the end of the Vietnam War, the CDF signed leases for multiple aircraft. Converted from aerial submarine hunting to liquid fire bombardment, tanks were engineered and installed into the aircraft, and the aircraft was designated the “S-2A”. The choice of the S-2 turned out to be a good one, as the plane could fly high and fast, and also low and slow. It was rugged, powerful, and maneuverable. During the 1970s, the modified S-2As replaced the TBMs and the F7Fs. Also, the planes were leased directly by the CDF from the U.S Navy, eliminating the “middleman” arrangement of contract use and maintenance. While modifications and maintenance could still be outsourced, and often were, the CDF had a much greater level of control over its own aircraft. Standardization around the S-2A made spares and repairs much more simple as well. Dozens of S-2As were added directly to the CDF air roster, to the exclusion of the other smaller firefighting aircraft, which were taken off contract and turned back to their outside owners.

An early photo of a CDF S-2A, showing a typical early 1970’s paint scheme.

As the CDF stayed with the S-2A through the 1980s and 1990s, the later model, higher capacity S-2E/Gs were made available as surplus by the U.S. Navy in 1996. The CDF saw fit to upgrade its fleet with the more powerful and capable later-model version, converting it to the firefighting “S-2T”.

A retired CDF S-2A in a vintage aircraft collection. This one is painted in standardized CDF markings of the 1980s and 1990s. These were replaced by the newer and more capable S-2Ts in the late 1990s and early 2000s.

The S-2Ts are the current workhorse of the CDF/Cal Fire air fleet. They can drop 1,200 gallons of water or slurry at a time, and they have a “hot loading” feature, meaning that they can land at CDF air bases, refill their water tanks, and take off without shutdown or delay. This offers many more drops in a multi-hour period, per plane, than other fixed-wing alternatives. They are maintained to a very high level of preparedness and reliability, and the multiple crashes of the 1970s, often created by mechanical difficulties, have been all but eliminated in the Cal Fire fleet, in recent decades.

A Cal Fire S-2T, doing what it does so well and so reliably.

In the 1960’s, the CDF and others had been experimenting with “heavy” firefighting aircraft, including the B-17. The B-17 was approved to carry 1,800 gallons of water or slurry, which was three times the capacity of the then-current TBM (but only 1.5 times the capacity of the much-later S-2T). After the 1970 California fire season, a push was made to grow the fleet of “heavy” firefighting aircraft.

The B-17 could drop 1,800 gallons of water or slurry per flight. This was not a huge amount, relative to the weight and size of the plane. Still, the weight of the liquid was more than twice the weight of the WW2 bomb loads (4,800 lb). The plane got away with this by carrying little fuel for short firefighting flights, rather than the considerable amount of fuel needed to traverse large parts of Europe and return to base.

The C-130 was considered as an alternative. In the early 1970s, military and Air National Guard C-130s were fitted with removable “MAFFS” (“Modular Airborne Fire Fighting System”) water tanks of 3,000 gallon capacity. In this way, the seasonal firefighting needs of the CDF could be met with MAFFS-equipped military/National Guard C-130s, which could be returned to their traditional duties when the fire season was over and the MAFFS equipment was removed.

The C-130s were also too large for most CDF air bases, and required their own distinct version of maintenance routines. By contracting military planes out to the CDF, many of these problems were sidestepped. Beginning in the 1970’s, up to eight C-130s have been made available, nationwide, for firefighting, and the program continues today.

A MAFFS-equipped military C-130 in 2021. Bright numbers and trim are used to bring the plane up to firefighting standards for identification and visibility.

In recent years, Cal Fire has worked to establish its own fleet of C-130s. Recently, the Coast Guard has made surplus some of its C-130H aircraft, and Cal Fire is currently refitting the planes for its own use. They are being presently rolled out, though they are too large for many of the Cal Fire air bases. The proof-of-concept of the MAFFS military C-130 program means that Cal Fire is not going into uncharted territory with their own planes.

A converted ex-Coast Guard C-130H being run through its paces. Cal Fire intends to deploy seven of these planes across the state, in the next few years.

All along, the CDF and Cal Fire have continued to use contract aircraft, as needed, especially the “very large air tanker” aircraft. During the destructive 2006 California fire season, the state approved a special and expensive contract to use a modified DC-10 on an “as-needed” basis. Since 2017, two of the DC-10s, privately owned by a company called “10-Tanker”, and part of a fleet of four firefighting DC-10s overall, have been under contract by Cal Fire. The planes are spectacular firefighters, lumbering low-and-slow to drop 12,000 gallons of slurry per flight. It is said that one pass will cover an area 300 feet wide and a mile long. The videos of these planes conducting their missions are worth taking the time to watch. Having witnessed these aircraft fighting fires, close up, I must say it is a very heart-thumping moment to see such a large plane flying relatively slowly, just above the ground, and then pulling up sharply once the load is dropped. The plane is said to be very maneuverable and relatively nimble, given that it has so little fuel on board (for the short firefighting flights), so it carries much less weight than its rated capacity. One of the 10-Tanker DC-10s did strike some treetops with a wing some years back, during a firefighting flight, and was repaired and continues in service. That must have been quite a ride!

One of the fire fighting DC-10s. Cal Fire has two of these firefighting behemoths under contract.

In the 2017 Fire season, Cal Fire quickly contracted for the use of a firefighting 747, as their firefighting assets became stretched. The 747 can drop up to 19,000 gallons in one pass. The fleet of three privately owned firefighting 747s was retired by its owners in 2021, but may return to service again for the 2023 fire season.

The privately owned 747 contracted by Cal Fire for the 2017 California fire season, fighting a fire in the Yucaipa area of Southern California.

Helicopters have also long been a part of the CDF/Cal Fire air fleet. They are versatile flyers, good for observation and also water drops. They have a slightly higher accuracy rate than the fixed-wing aircraft (someone took the time and effort to measure all of this) at hitting their water drop targets. Given their capacity for hovering at-will, somewhat higher accuracy should be expected. The helicopters are also used for inserting firefighters and their gear onto the ground, in places where they can’t easily or quickly hike to, or be driven to. Likewise, they can be valuable for removing firefighters at the end of their shifts, or to get them out of dangerous situations. The helicopters are also capable of performing aerial rescues, where a cable drop can retrieve a victim in a stretcher, if the need arises.

As with the fixed-wing aircraft, the CDF contracted for the use of various types of helicopters in the early years. Bell Jet Rangers were popular choices, but five accidents involving contracted Bell helicopters in 1979 (similar to the spate of fixed-wing accidents in the early 1970s), caused the CDF to review its helicopter policy, as it had done earlier with the fixed-wing firefighting program.

The result was to acquire military surplus Bell UH-1F “Hueys” in 1981, for refitting as firefighters. Initially, the helicopters were used to insert and remove teams of firefighters from the field, especially as first responders to fires detected in remote areas. Later, as the Hueys were used more often for water drops using large buckets, it was decided to more fully fit out the copters with water tanks. A new batch of later model UH-1H copters were obtained in 1989, and they were more fully worked over and upgraded for CDF use (similar to the elaborate upgrades of the S-2Ts, that was going on at roughly the same time). The CDF determined that for reliability and safety, thorough reworking of the aircraft to meet their specific needs was time and effort well spent. The new highly modified UH-1H copters were designated “Super Hueys”. The copters can deliver a 360 gallon payload, and can carry ten people in addition to the pilot.

A “Super Huey” dropping its 360 gallon payload.

The “Super Hueys” have reached an over 30 year life since their introduction, so they are being phased out in favor of a brand new group of Sikorsky “Fire Hawks”. These are the S-70 “Black Hawk” military copters, modified with water tanks for firefighting use. The on-board water capacity will increase from 360 gallons on the Super Hueys to 1,000 gallons on the Fire Hawks. That’s a tremendous improvement in capacity. The Fire Hawks are being modified and added to the fleet as we speak.

A Sikorsky S-70i “Fire Hawk” practice run, delivering firefighters to a fire site. The craft can carry twelve in addition to the pilot.

A “Fire Hawk” dropping its 1000 gallon payload.

We have covered the fixed-wing firefighters, the very large air tankers, and the helicopters. The other piece of aerial firefighting is the spotter plane. While various contracted planes had been used for fire spotting over the years, the 1970 fire season indicated that a fleet of dedicated spotter planes should become part of the fleet. In 1974, twenty military surplus Cessna O-2 aircraft were delivered to the CDF for use as fire spotters, and were designated “O-2A Super Skymasters”. Beyond spotting and pinpointing fires, they could also be used as aerial command and control aircraft during complex firefighting operations.

Military surplus Cessna O-2A aircraft were added to the CDF air fleet in 1974 as fire spotter planes.

In 1993, the O-2A fleet was replaced with sixteen North American Rockwell OV-10 aircraft. One reason for the change was that it was found that the C-130s, and, later, the DC-10s and 747s needed “lead” planes to visually follow to their air drop target sites. While the size and outward visibility of the Grumman S-2Ts meant that they could maneuver into the proper spot unaided, the larger craft need a plane to follow to the drop site. The maximum airspeed of the O-2s was about 200 mph, but the top speed of the OV-10 was just under 300 mph, making it a more appropriate choice as a lead plane for the heavy air tankers.

A Cal Fire OV-10 spotter plane in flight.

The videos of the “very large air tankers” (“VLAT”s) are spectacular, but one can also look for the OV-10 spotter planes in the videos.

A video still of an OV-10 laying down a trail of white smoke for the “very large air tanker” (VLAT) to follow and to release its air drop.

The VLAT follows seconds later, dropping the slurry load. This VLAT is the 747 “944”, under contract to Cal Fire in 2017.

The OV-10 will typically lead the VLAT, who will maintain visual contact and follow the OV-10, both by path and by elevation. At the drop site the spotter plane will set off a short trail of white smoke, after which it will quickly peel off to the side and gain altitude. The VLAT will drop its slurry load, following the white trail of smoke laid down by the spotter plane.

In a still shot from a video, with the camera mounted on the OV-10 spotter plane, and looking aft through the tails, showing the white trail of smoke left by the spotter and the VLAT 747 beginning its drop.

The 747 continues its air drop (which can last for a mile or more), while the OV-10 spotter turns left and gains altitude, after having led the 747 to the drop site, and having marked the drop spot with white smoke.

Cal Fire has about 60 to 70 aircraft in its fleet. The current roster contains 23 Grumman S-2T Airtankers, 12 Super Huey helicopters and 12 Fire Hawk helicopters, and 16 OV-10 Air Tactical (spotter) planes. Seven C-130 Airtankers are currently being added to the fleet, while the Super Hueys are expected to be retired from service over the next year. Cal Fire also has two DC-10s under long term contracts, and continues to contract with other aircraft owners during heavy fire seasons. It is not uncommon to see helicopters and aircraft fighting fires in California, other than the ones listed here. Keep in mind, too, that the U.S. Forest Service and some local firefighting agencies also employ aerial assets. You will notice that the Los Angeles area is not fully covered by Cal Fire assets. That is, in part, because the Los Angeles Fire Department has been building its own fleet of capable helicopter firefighters.

Part of the Los Angeles Fire Department air fleet, a brand new Leonardo AW-139.

Cal Fire has a large number of air bases, some exclusive and others shared with other agencies. The concept is to have air firefighting assets quickly available to any part of Cal Fire’s areas of responsibility.

Here is a map and roster of Cal Fire’s air bases and assigned aircraft. The color coding shows where Cal Fire has the primary areas of responsibility, though firefighting assets are often shared and coordinated with other agencies.

Despite Cal Fire’s significant and growing commitment to fighting wildfires, the number of acres burned, lives lost, and damage done, year by year, by-and-large continues to rise in California. It is impossible to argue a counterfactual, so one cannot say what the scope of recent California fire seasons might have been without Cal Fire’s efforts. But it is safe to say that Cal Fire’s task is ever more daunting, as time goes on.

The 747 “944” laying down a loooooong slurry drop in a 2017 California firefighting operation.