Does anyone know how many large air tankers we need?

Two studies, completed 10 and 21 years ago, said there is a need for 35 or 41 air tankers.

In the interview with Shawna Legarza published on Wildfire Today this morning, the National Fire Director for the U.S. Forest Service said in response to a question about how many large air tankers are required:

I would say we need anywhere from 18 to 28, you know that’s what it says in the [2012 Large Airtanker] Modernization Strategy. I think that’s a good range.

We re-read that Strategy, and could not find any independent conclusion reached by the authors about the number of air tankers. But, on page 3 there was this:

Continued work is ongoing to determine the optimum number of aircraft to meet the wildfire response need, but studies have shown that it is likely that between 18 and 28³ aircraft are needed.

The referred to footnote #3 is this:

³The requirements for large airtankers have been derived from the “National Interagency Aviation Council Phase III Report, December 7, 2007”, and the “Interagency National Study of Large Airtankers to Support Initial Attack and Large Fire Suppression, Phase 2, November 1996”.

The first of the two studies recommended increasing the number of large air tankers on exclusive use contracts from 19 in 2008 to 32 in 2018. Plus, there would be three water scoopers by 2018, bringing the total up to 35. The table below is from the study.

fire Aviation Strategy
Screen grab from the 2007-2009 NIAC Interagency Aviation Strategy document. Phase III, page 21.

The second document, the 21-year old study from 1996, recommended 20 P3-A aircraft, 10 C-130B aircraft, and 11 C-130E aircraft, for a total of 41 large air tankers.

The “18 to 28” air tankers mentioned in passing in the “2012 Large Airtanker Modernization Strategy” is not reflected in the referrals indicated in the footnote.

Much has changed in the world of aerial firefighting in the 10 to 21 years since those two studies were written. (They are two of the 16 air tanker studies and reports listed on the Wildfire Today Documents page.)

But what has not changed is that the numbers in these studies, written by smart, well-meaning people, are basically back of envelope stuff. There has not been in the United States a thorough, well designed analysis of the effectiveness of aerial attack, exactly how much retardant is needed in a certain time frame, where aircraft need to be based, and how many and what type of aircraft are required.

Under pressure from Congress and the GAO to justify the aerial firefighting program, in 2012 the U.S. Forest Service began a program to develop metrics and collect data to document and quantify the effectiveness of aircraft in assisting firefighters on the ground. This became the Aerial Firefighting Use and Effectiveness (AFUE) program. It will be several more years before they expect to release findings related to the effectiveness and probability of success of aerial resources.

We asked “Bean” Barrett, a frequent contributor on Fire Aviation, for his view on how many air tankers are needed. He started by saying the general theme of the letter written in 2012 by Ken Pimlott, the Director of CAL FIRE, to the Chief of the Forest Service, is still applicable today. Director Pimlott said in part that the then-recent USFS Large Air Tanker Modernization Strategy was insufficient to meet the needs of the combined federal, state and local wildland firefighting missions.

Bean’s further input is below.


“18-28 Large Air Tankers as the Federal inventory objective? Could we be a little more precise? What if the federal requirement was defined by referring to something like required retardant gallons delivered/ hour/ mile from base/ dollar. At least then, some basic economic analysis could be used to justify inventory when it comes around to contracts and budget time. What about required number of LAT sorties/ year / GACC?

Do the NICC UTF numbers actually identify requirements shortfalls? How many IMT’s don’t bother to request air support when they don’t think any air is available? UTF data would be very useful to demonstrate inventory shortfall if UTF’s represented all the unfilled need. In 2015 UTF’s represented a 10% shortfall in LAT sortie generation requirements. In 2016 UTF’s represented a 15% shortfall. Based on what I would say are very conservative UTF numbers, there has been at least a 10-15% shortfall in available LAT inventory over the last two years.

Really hard to comment on inventory objectives when it isn’t clear what the Large Air Tanker mission is. To paraphrase Lewis Carroll, if you don’t know what you want to do with them, any number will be enough.

Is the mission IA or extended attack? Is it ground support or independent tasking? What effects are trying to be achieved and how well are they achieved? Should an attack within 24 hours really be considered IA for an aircraft? CALFIRE wants aircraft on scene in 20 minutes. The Australians want <30 minutes.

Just for openers, this is a very good ops analysis piece using real data from real fires:

Our results confirm earlier research results related to LAT use and challenge a long-held assumption that LATs are applied primarily to assist in the building of line to contain fires during IA.

Perhaps most importantly, we highlight system-wide deficiencies in data collection related to objectives, conditions of use and outcomes for LAT use.

Our current inability to capture drop objectives and link specific actions to subsequent outcomes precludes our ability to draw any conclusion about the effectiveness of the federal LAT programme.

A finding in the study … Mean time of day for drops was 15:39 and only about half of the drops were IA. This makes it really difficult to say that LAT’s are there to support the ground crews.

Why not tie LAT requirements directly to the number and type of IMT’s mobilized? Perhaps some ops analysis would find a ratio of number and type of tankers to type of IMT’s mobilized? Or perhaps a ratio of days IMT’s mobilized to LAT sorties required for support? Start thinking like an integrated air-ground team and define air requirements in terms of IMT’s or crews mobilized and supported. When the definition of Head Quarters units [ IMT’s] composition or types of ground crews includes the number and type of aircraft included in support, the inventory objective for tankers will fix itself. I expect everyone has a much better handle on the amount and type of ground support required today compared to the very vague understanding of tanker requirements. Tie air requirements to the better understood ground requirements.

Once the real data gets collected and analyzed, it may be found that the best air IA assets for type 3 IMT’s aren’t fixed wing tankers. (Provided IA is redefined to something like arrival within 20-30 minutes of dispatch.)”

Another air tanker study: the use and effectiveness of large air tankers

P2V whoopup fire air tanker
Tanker 45, a P2V, on the Whoopup Fire near Newcastle, Wyoming, July 18, 2011. Photo by Bill Gabbert.

We just became aware of another air tanker study that the U.S. Forest Service commissioned. By our count this is the 13th federal study on the use of air tankers since 1995, and was one of three completed in 2013. (A list of the studies is at Wildfire Today.)

Titled Large airtanker use and outcomes in suppressing wildland fires in the United States, it was written in 2013 and published in the International Journal of Wildland Fire in February, 2014. The document maintained a low profile, possibly because it was behind the journal’s pay wall, rather than being an Open Access document.

The study attempts to determine how effective large air tankers (LAT) have been at preventing fires from escaping initial attack (IA). The authors begin by describing the poor data that they used to develop their conclusions. For example, the sparse data made it very difficult “to track drop location and time, to associate drops to specific fire events, to gather information on the fire environment (fuels, weather, terrain, etc.) at the time of the drop and, critically, to clearly identify mission objectives for each drop.”

The authors used some convoluted methods to make guesses about which retardant drops were on IA fires and which ones were not. And, “due to data availability issues” they only considered stats from two years, 2010 and 2011. In 2010 there were 19 LATs in the fleet at the beginning of the year and 14 in 2011, but by the end of 2011 the study reports there were only 10 available.

Since the air tanker fleet has atrophied from 44 in 2002  to as low as 9 in 2013, it has been impossible to always produce a LAT every time one is needed on IA. And if it does show up, the chances of it arriving while there is still a chance to slow the spread, enabling ground based firefighters to contain the fire, are not as great as they were in 2002 when there were almost five times as many air tankers.

The authors addressed the timing of air tanker drops:

Therefore, the determination of whether or not a fire will benefit from LAT drops in IA will be directly related to the delay from ignition to drop occurrence. This delay allows a fire to grow and cross a critical threshold where fireline production of IA resources cannot catch the growing fire perimeter. When evaluated in this light, the demonstrated low success rate for IA containment could be addressed by reducing the time between ignition and LAT arrival on these fires with a high potential to escape. This would require an improved ability to rapidly recognize an individual fire’s escape potential so that LATs are ordered very early in the event. Further, this suggests that if we can improve our ability to identify when and where these types of ignitions are likely to occur we should be able to effectively pre-position LATs before an outbreak of fires. If the IA success rate could be improved through such a system, overall LAT demand may be reduced because many of the evaluated drops were associated with IA fires that ultimately escaped.

And they wrote about the resistance to control of fires that receive retardant drops on IA:

That the rate of escape associated with fires that receive drops during IA is so high – far higher than the general escape rate of approximately 2 to 5% – is strongly suggestive that LAT use, when it does occur in IA situations, occurs on the more difficult fires (i.e. Category C fires as defined by Keating et al. 2012)

The “Keating et al 2012” report is more commonly known as the Rand Report.

They also make the point that although the USFS’ policy is to prioritize LAT use on IA rather than Extended Attack (EA) fires, a high proportion of LAT drops occur on EA fires.

In spite of these conditions, the authors apparently felt comfortable making the following statement in the paper’s introduction:

Results suggest that containment rates for fires receiving large airtanker use during initial attack are quite low.

A statement like that when taken out of context, or without understanding the limitations of the report’s data, can be very misleading.

If air tankers are going to be effective in IA, first they have to be near enough to the fire to arrive, preferably, within 15 to 30 minutes after being dispatched. And, they must be dispatched if not at the first report of smoke, at the first confirmation that there is a wildfire. If there is a delay until a fire officer arrives at the scene to make the decision to order aircraft, that could be the difference in effective or ineffective air tanker use.

As we have stated many times, the prescription for keeping new fires from becoming megafires is:

Rapid initial attack with overwhelming force using both ground and air resources, arriving within the first 10 to 30 minutes when possible.

Below is a graphic that we put together showing the Unable to Fill rates for LAT requests, the number of LAT requests, and the size of the air tanker fleet since 2002.

Graph, request for large air tankers

(The chart above was revised February 3, 2015 to include data from 2014.)

A new study looks at four possible air tankers for Colorado

Colorado Air tanker study cover

In case the 11 air tanker studies since 1995 are not enough, there is now a twelfth. As you can see on the cover above, it is named Analysis of Aircraft for the Fire Fighting Mission in Colorado. It compares four different aircraft, two of which have received certification from the Interagency AirTanker Board, and two that have never been converted into air tankers:

  1. BAe-146
  2. C-130H/Q
  3. C-27J
  4. S-3B

The study is Colorado-specific in that it looks at the retardant capacities if the aircraft were to fly out of four air tanker bases in the state: Denver, Durango, Grand Junction, and Pueblo, with elevations ranging from 4,726 to 6,685 feet, and runway lengths from 9,000 to 10,502 feet.

The study primarily considered four characteristics of the aircraft:

  • Retardant tank volume (certificated or estimated)
  • Mission payload capability from USFS air tanker bases in Colorado
  • Sustainability and after sales product support
  • Mission effectiveness expressed as gallons transported per hour and per day

The C-130J/Q led the field in all four categories.

Assuming the data compiled by Conklin & de Decker Aviation Information is correct, the retardant capacities at the Colorado air tanker bases “during typical summer temperatures (ISA + 30 degrees C)” for the C-27J and S-3B are stunningly low, averaging 184 and 181 gallons, respectively. The BAe-146 would have to download from the maximum of 3,000 gallons to 1,884, while the C-130Q/H would always, according to the report, carry their maximum load of 3,500 gallons.

The tables below are from the study on page 33.

Colorado Retardant delivery by four types of aircraftWe are curious to know who paid for the study, which was “prepared for [Colorado state] Senator Steve King”. A phone call to Conklin & de Decker Aviation Information was not immediately returned. Senator King has been very interested and vocal about the possible acquisition of firefighting aircraft for his state.

Earlier this year legislation passed in Colorado that allowed for the creation of a “Colorado Firefighting Air Corps”, but it did not authorize any funding for the agency. The bill was introduced by Senators Steve King and Cheri Jahn


GAO air tanker report says more data and planning needed

A P2V on the Whoopup Fire, 2011
A P2V on the Whoopup Fire, 2011. Photo by Bill Gabbert

A report released by the Government Accountability Office yesterday about air tankers pointed out some of the same issues that were in a 2009 audit by the USDA’s Office of Inspector General. Both reports emphasized that the U.S. Forest Service and the Department of Interior need to collect data about the effectiveness of air tankers and put together a coherent plan on the management of the fleet, and a plan for the acquisition and justification of additional aircraft.

This is the 11th report about air tankers since 1995.

The GAO report was in response to a March, 2012 request by four U.S. Senators asking for a review of “the nation’s depleted fleet of firefighting aircraft and the remedies needed in the face of increasingly severe fire seasons.” The Senators were Ron Wyden, Lisa Murkowski, Dianne Feinstein, and Mark Udall.

The GAO conducted an “audit”, between August 2012 and August 2013. Their product assembled a great deal of information about the current state of the aerial firefighting fleet which has dwindled from 44 in 2002 down to 8 to 11 this year. But it does not have a lot of new, specific, and practical “remedies”, other than collect data and develop a coherent plan. It concluded:

None of the agencies’ studies and strategy documents contained information on aircraft performance and effectiveness in supporting firefighting operations, which limits the agencies’ understanding of the strengths and limitations of each type of firefighting aircraft and their abilities to identify the number and type of aircraft they need.

The GAO had three recommendations:

  • Expand efforts to collect information on aircraft performance and effectiveness to include all types of firefighting aircraft in the federal fleet;
  • Enhance collaboration between the agencies and with stakeholders in the fire aviation community to help ensure that agency efforts to identify the number and type of firefighting aircraft they need reflect the input of all stakeholders in the fire aviation community; and
  • Subsequent to the completion of the first two recommendations, update the agencies’ strategy documents for providing a national firefighting aircraft fleet to include analysis based on information on aircraft performance and effectiveness and to reflect input from stakeholders throughout the fire aviation community.

The report included some information that is not widely known about Neptune’s BAe-146 air tankers. The Interagency AirTanker Board refused to extend the interim approval of the drop system in December, 2012 due to problems with the retardant delivery system and deficient performance. However, in February 2013, the National Interagency Aviation Committee overrode the IATB decision citing a shortage of air tankers. The committee granted an extension of the interim approval of the retardant delivery system through December 15, 2013. Neptune has recognized the problem and said a redesigned system is being installed in its’ third and fourth BAe-146s and next winter the problematic design in the first two will be upgraded.

The USFS’s recent Request for Information to possibly lease 7 to 15 aircraft outfitted with high-tech sensors to serve as platforms for aerial supervision could be partially in response to the GAO’s criticism about the lack of aircraft effectiveness data. These aircraft would be equipped with Infrared/Electro-Optical sensing systems with color camera and FLIR systems which would have recording capability. If the personnel on board had time, when they are not managing aircraft, they could record air tanker drops and monitor the location long enough to determine if the water or retardant had the desired effect on the spread of the fire. The aircraft would have an aft crew station for two people designed for training which would have a duplicate set of controls and radios, which could possibly also be used for evaluating drop effectiveness when not used for training.


Thanks go out to Rick and the others who let us know about this.

AVID air tanker report released

Tanker 07 on the Myrtle Fire, 2012
Tanker 07 on the Myrtle Fire, 2012. Photo by Bill Gabbert.

The U.S. Forest Service has released another study on air tankers (large 10mb file), which is one of nine commissioned by the agency on the topic since 1995. The $380,000 contract for this one was awarded to AVID, a Virginia-based company that employed a crew of retired and current aviation professionals for this project.

It would be helpful if an expensive 117-page report like this clearly stated the objectives for the study, but all we could find was this:

The purpose of this study is to build analytical data that can be used to estimate the requirement for airtankers in the future.

The report includes a huge quantity of statistics about how air tankers have been used over the last several years. I was expecting to see some concrete recommendations about how they should be used in the future, but there was little along those lines.

This study, like the RAND report, included no information about Very Large Air Tankers. But while the RAND study was favorable toward scoopers, this AVID report addresses them like this:

There is a relatively small amount of USFS background data that documents the use of scooper aircraft, making it difficult to come to conclusions regarding their use. While continued analysis of scooper usage is warranted, the focus of the current analysis is primarily on large airtanker usage, followed by heavy helicopter usage.

There was little else in the report about scoopers, reinforcing the perception that the USFS has a bias against them.

There was definitely some interesting data in the study, and below are two illustrations. Click on them to see larger versions.

Wildfire probability June 14 Unable to fill requests vs number of air tankers

Other air tanker studies

USFS releases study on C-27J

C-27JThe U.S. Forest Service has released a study on how the C-27J could be used by the agency if the Air Force gives them seven as expected. This ninth air tanker study since 1995 was a surprise to us — somehow the Forest Service kept this one under wraps.

The report was prepared by Convergent Performance, LLC in Colorado Springs, Colorado at a cost of $54,000. We can’t find a date on it but the document must have been released very recently. We found a link to it on the Forest Service web site.

If used as an air tanker

The report confirms one thing that we were told by Art Hinaman, USFS Assistant Director for Aviation, on July 1 when we talked with him at the dedication of the memorial site for the crash of MAFFS 7 a month ago. Mr. Hinaman said he thought the C-27J would hold around 1,800 gallons of retardant when outfitted with a conventional, gravity-fed, constant flow tank, and that is what the Convergent study came up with. Of course, Mr. Hinaman had probably already seen Convergent’s findings when we talked about it.

The report concluded the C-27J could carry 1,850 gallons of retardant if 3,200 pounds of unneeded equipment were removed, including flight deck armor (approximately 1,100 lbs), miscellaneous mission equipment such as litter stanchions, tie-down chains, ladders etc. (approximately 1,000 lbs), and the cargo loading system (approximately 1,200 lbs).

If a mini-MAFFS slip-in retardant system was designed for the C-27J cargo space, which is smaller than a C-130, it would hold approximately 1,100 gallons if the same excess equipment was removed. A MAFFS2 has a maximum capacity of 3,000 gallons, but frequently carries less depending on density altitude and fuel load. The mini-MAFFS would not have an air compressor, therefore requiring the aircraft to depend on air compressors being prepositioned at air tanker bases. The USFS has six mobile air compressor systems that were built to support the original MAFFS, but the latest generation, MAFFS2, has an onboard air compressor.

If used as a smokejumper ship

C-27, jumping from rampSmokejumpers could exit the C-27J through the two side doors or the aft ramp. Depending on how the aircraft was configured, it could transport between 24 and 46 jumpers.

Here is an excerpt from the report:

The C-27J aircraft is very compatible with the smoke jumper mission. The aircraft is specifically designed as an aerial delivery platform for personnel as well as cargo. The C-27J is a high wing aircraft keeping the disruptive airflow above the jump platform; a distance of 41” between the propeller and fuselage to keep turbulence well away from the jumpers; and a horizontal stabilizer on the tail that sits well above the jumper path practically eliminating any parachute contact. The high wing design and the cockpit’s 16-windows provide the best conditions for air to ground visibility and the robust avionics suite with HUD allows pinpoint GPS accuracy for each airdrop. The side doors have a very safe and comfortable height of 6’ 4” and the rear door opening is 7’ 5” high. Free-fall jumpers can be deployed from either side door exit or from the aft ramp. Static line jumpers can only be deployed using the side door exits.

If used to transport firefighters

According to the report, the aircraft configuration can be changed and fitted with standard outer and center seating to accommodate 68 passengers with limited personal equipment plus 2 loadmasters.

The USFS asked Convergent to analyze how the C-27J could be used to transport two 20-person crews to high-elevation airports with relatively short runways. (The maximum allowable flying weight for a hotshot crew is 5,300 pounds.) The examples given were Alturas, CA (KAAT), 4,378′ above sea level; Reserve, NM (T16), at 6,360′; and Negrito Airstrip, Reserve NM (0NM7), at 8,143′. The conclusions were that landing would not be a problem. At two of the three airports taking off would be possible, but at Reserve (T16) with the 4,777′ runway, the aircraft would usually be able to carry only one crew when departing.

If used for cargo

The aircraft could carry between 12,222 and 25,353 pounds of cargo.


If the C-27J accumulated 250 flight hours annually, Convergent estimated it would cost about $7,400 an hour over a 20 to 30 year life span. At 400 hours a year the cost would be about $5,800 an hour over 20 to 30 years.


From the report:

The C-27J is training intensive and requires constant skill application by the aircrews to remain proficient and mission-ready. Although highly automated, this is not an aircraft that can be effectively and safely operated with min-run training and skill. It requires highly skilled professional aircrew. The training available is thorough and adequate, but it is time consuming (2- 3 months) and relatively expensive in its current form. The length of training and lead-time required to have a fully qualified crewmember to meet fire season operational demand will require structured, deliberate, action. Training is only offered by two sources, one being the manufacturer, but it is conducted overseas with equipment not representative of the aircraft the Forest Service would receive and is generally limited to new purchase customers as part of the point of sale agreement. The only US based training offered is in Warner-Robbins, GA.

Other air tanker studies