Newsletter à télécharger en pdf :
Télécharger le pdf ici (6,4 Mo)
Mais également en lecture à l’écran sur Calameo :
Bonne lecture !
Dernier épisode pour une saison 2017 qui aura tiré en longueur. : des news, des photos des opérations aux USA mais aussi un compte-rendu de l’AFF qui s’est tenu à Nîmes en octobre dernier.
Newsletter à télécharger en pdf :
Télécharger le pdf ici (4,7 Mo)
Mais également en lecture à l’écran sur Calameo
Bonne lecture !
As the 2011 and 2012 CFPA news issues are no longer available on calfirepilots.com, you can find these here, free to download (links are at the page bottom) or in direct reading on Calameo (Individual link under each issue summary).
Note to download files : the use of adblock plugin is recommended to avoid banners and pop-ups.
This article was published in september and october 2012 issues of CFPA Newsletter.
The C-130 is an exceptional aircraft. Still in production 50 years after its maiden flight is evidence of its qualities and effectiveness. Successful for numerous tactical missions from transport through maritime surveillance, C-130 has also been involved in the fight against forest fires since the early 70’s, initially with the United States Air Force and Air National Guard. And between 1990 and 2002, a handful of civilian C-130As contracted to US Forest Service left their mark on this business; they were considered some of the best airtankers ever used for fighting wildland fires.
Today (1), only military C-130s with MAFFS are used for aerial fire suppression in the USA. The MAFFS I (Modular Airborne Fire Fighting System) was conceived in the 70’s to give military aircraft the capacity to reinforce the commercial airtanker fleet when all civilian firebombers are activated and in use. This 3000 US gal device consists of a mobile palletized platform installed aboard a C-130, with 5 tanks, and two nozzles protruding through the opened rear ramp. System pressurization was from an external source at the reload base. The 8 USFS-owned, USAF-operated MAFFS I were phased out, replaced by MAFFS II in 2009. MAFFS II consists of a single 3400 US gal tank with internal pressurization and a single nozzle which passes through the port side door, which allows the aircraft to remain pressurized.
There are numerous criticisms against MAFFS systems. Many consider them not as effective as, and more expensive than a permanently mounted retardant delivery system. But several countries elected to equip one or more C-130s with MAFFS I, ie, Portugal, Morocco, Thailand, Tunisia, Italy, Brazil and Turkey.
C-130s with MAFFS I performed over 6,500 fire missions between 1974 and 2009, applying 75,000 tons of retardant on fires in the USA. 9 MAFFS II where bought by USFS but sadly, July 1st 2012, MAFFS 7 from 145th AW, crashed in South Dakota while making a drop killing 4 National Guard Aviators (2). The crash was due to a severe windshear during the drop run. It was the first crash ever for a MAFFS aircraft.
Commercially contracted C-130 Airtankers
During the 80s, several USFS contractors in charge of providing heavy tankers to the federal agency were looking for a new type of heavy tanker after several structural failures resulted in the grounding of C- 119 airtankers. The USFS request the U.S. Air Force to transfer some C-130A, recently stored in Arizona, to supplement and modernize its commercial fleet of old Privateer, Neptune, and Douglas piston-powered propliners.
An agreement was reached in 1987, and C-130s were provided to Hemet Valley Flying Services, Hawkins & Powers, and TBM Inc. in exchange for former airtankers such as C-119s, B-17s, C-54s to be used as exhibitions in museums. A fourth company, T&G from Arizona, eventually obtained some Hercules. In addition, P-3A Orion were obtained by Aero Union Corporation in Chico, California.
Ultimately 22 C-130A were transferred to these companies, with the goal of turning them into fire bombers and leasing them back to the USFS at a competitive price. A percentage of the aircraft were to be used as “spare parts” to support those converted to airtankers. This plan was intended to help contain the cost of supporting the aircraft for a large portion of the aircrafts life cycle as an airtanker, thus reducing the contracting cost to the Forest Service.
The agreement created a huge scandal a few years later. Commercial airtanker operators that were not included in the agreement claimed unfair competition.
Federal investigations were conducted about these transactions. In 1993 it was determined that the USFS did not have the authority to conduct these negotiations with the eventual outcome that the Branch Director was fired.
After T&G got some C-130s, they were accused of supplying aircraft in the early 90s to a Central American company, Trans Latin Air, suspected of being a carrier of the Cali cartel. T&G also sold two aircraft for 3.6 million to a Mexican company. One of the aircraft was seized in 1997 by Mexican authorities for being involved in a smuggling case involving the Tijuana Cartel. However, it was later determined that the aircraft, was not used to transport narcotics to the U.S. But that aircraft, acquired through a bank sale before the Forest Service program started, can’t be linked with the USFS program.
One of the operators used the aircraft given to them for non-firefighting missions. This infuriated the USFS and they stopped all contracts for C-130s with that operator, who went on to contract with France and Spain as fire bombers.
There was a long series of trials held throughout the decade to uncover what the responsibilities of the various parties was and even to determine the correct owner of some of these aircraft. There were accusations that the agreement between the USFS and the USAF was not legal, there were even prison sentences. However, the C-130s that had been contracted to be Airtankers remained active. There is no doubt now that these various scandals involving the C-130A had a considerable influence on events early next decade.
The C-130A tankers are category I type tankers in the Incident Command System classification, together with MAFFS, DC-7, and P-3 Orion as they have a 3000 US Gal capacity. The first C-130A Airtankers are activated for the 1990 fire season.
C-130 with conventional tanks
Hemet Valley Flying Services, from California, and Hawkins & Powers from Wyoming where former C-119 users and had jointly designed the Flying Boxcar’s tank. As new users of C-130A, they again joined their forces and, using the old tank, modified it to be used for the new airtanker.
The tank is about 3,000 gallons. The rectangular tank weighs 860 pounds empty. It has eight belly gates that allow drops in sequence or massive and was installed in Tanker 81, T82, T83 and T88 for HVFS and Tanker 130, T131 and T133 for H&P. The HVFS and H&P tanks also suffered from reliability problems.
In terms of efficiency, conventional tanks are more effective than MAFFS, but control of the flow is not as fine as the system that is installed on other C-130 Tankers…
C-130 RADS, the ultimate weapon!
For their C-130A, TBM and T&G companies called upon Aero Union for the installation of a 3000 gallons/27 000 lbs tank with an advanced drop system.
The RADS (Aerial Retardant Delivery System) tank is a «Constant Flow» design, equipped with two doors controlled by a computer (3). The crew simply selects the quantity and coverage level desired. The computer opens the doors and modulates the flow to achieve the selected setting. The tank requires an opening of 20 feet long and 2 feet wide in the floor. Filling points are located on each side of the fuselage to facilitate ground operations. A control module with the settings of quantity and density is located on the pilot’s overhead panel of the cockpit and a release button located on both yokes. The lower part of the tank, with baydoors, is permanently installed, adding about 480 lb to the aircraft, but the top of the tank is removable, allowing the aircraft to be used for cargo missions by removing the upper part of the tank and installation of a removable floor.
The French and Spanish experience
In 1990, French Sécurité Civile, organism in charge of fighting wildland fires in south of France, phased out its last two DC-6 which for ten years had shown the importance of having planes loaded with ten tons (2600 Gallons) of retardant in support of their Canadairs. In search of a new heavy tanker it was decided to call in reinforcements from the U.S. and thus the Hemet Valley Flying Services, C-130 N135FF Tanker 82 came to demonstrate its capabilities for two months that summer.
The Tanker lease was renewed for the year 1991 for two aircraft and N131FF Tanker 81 came with Tanker 82 to support the French fire fighting assets.
The following summer, HVFS provided only one plane, the N131FF Tanker 81, the second was a T&G RADS one, N116TG Tanker 30. In 1993, the Sécurité Civile contracted T&G for two C-130s, N116TG (T-30) and N117TG (T-31).
These two aircraft were locally renamed Pélican 82 and 81 (4) to fit into the French tanker numbering system. Because the uneventful 1996 season no C-130 was leased in 1997. The contract resumed for the 98 season but for a single aircraft, the Pelican N116TG Pélican 82 and was through the 2000 season. In September 1999, C-130 was used for multiple logistic missions to Greece, after earthquakes. Thanks to its versatility, the Hercules was again completely at ease with its generous anatomy and ease of loading and unloading provided by the large rear ramp, a real asset for this kind of mission.
Alas, while thoughts about the purchasing of some C-130 is still underway when, in his last flight of the 2000 season, on September 6th Pelican 82 crashed in Ardèche. Of the four men on board that day, two are killed, the flight engineer Joe Williams and the French first officer Paul Trinque. The other two, the captain Ted Hobart and the mechanic Ted Meyer were seriously injured, which was a miracle. The investigation concluded that is was CFIT, with the sun in front of the crew as aggravating factor.This tragedy will mark the end of C-130 fire bomber in France even if the aircraft was not at fault in the crash.
For the 2002 and 2003 summers, T&G N117TG flew as a Tanker for ICONA in Spain. Based in Valencia, the C-130 was able to operate everywhere in the country in less than two hours. It was widely used, sometimes making dozens of flight hours each week and making many drops. While the contract should have been renewed in 2004, it was cancelled by the new spanish government, elected in March. It was the true end for C-130A Airtankers, because the whole fleet was refused by the US Forest Service in USA since 2002.
The dramatic end of an adventure.
On August 13th, 1994, the HVFS Hercules, N135FF Tanker 82 crashed against the hills near the town of Pearblossom, California (5). The NTSB investigation concluded that unexplained explosion in an engine was the origin of this tragedy. HVFS did not survive for very long after the crash, some of their aircraft were bought by H&P.
Eight years later, a little less than two years after the Pélican 82’s accident, on June 17th, 2002, mid-afternoon, the Hawkins & Powers C-130 Tanker 130 N130HP was flying near Walker, California, ready to make his 6th drop of the day on the «Canon Fire». It crashed, leaving no chance for its crew of three men (6).
The incident was filmed and the several seconds of footage was rapidly broadcasted around the world because the images were stunning. The focus was largely detrimental to the reputation of the C-130A AirTanker. The footage showed the Hercules coming to drop its load, the two wings appear to fold upward and separate from the fuselage which rotated, struck the ground and exploded. No chance for the crew to escape their terrible fate. All C-130A Tankers are grounded that evening.
Just over a month later, on July 18, a PB4Y Privateer of the same company, Hawkins & Powers, Tanker 123, had a fatal structural failure in flight near Estes Park in Colorado, killing both pilots.
For the USFS, these last two accidents were the direct consequences of an aging fleet of fire-fighting aircraft. On May 10, 2004, days after the publication of a formal report on the status of the heavy air tankers fleet, the federal agency made a decision: None of Heavy Air Tanker will be activated for the season! To resume the service, the contractors had to examine their planes and produce certificates of compliance.
The Hercules and Privateer, which had not flown since 2002 accidents, are banned from any federal contract for the future, which was a fatal blow for their careers as firefighters.
The technical investigation about the crash of Tanker 130 found a strong structural fatigue and a huge crack in the lower center wing panel. For operating companies, particular attention should have been paid to their maintenance. The H&P Company is blamed for carelessness as significant traces of fatigue were found on the wreckage of its crashed aircraft and those still in service.
H&P were C-130A, Privateer and KC-97 operator and was particularly affected by the May 2004 decision. It did not recover, finally disappearing in the following months, unable to do anything with its now unusable aircrafts.
According to this investigation, the N135FF wreck was examined a second time. In light of the occurrence of Tanker 130 crash, the investigators (7) discovered that the origin of the famous fatal blast was directly linked to an undetected fatigue cracking of the lower surface panel at a Center Wing Station 80 (L or R). Both planes had been victims of the same symptom, a mixture of structural undetected fatigue due to lack of maintenance. The C-130A are now permanently banned from federal contracts for fire fighting. Some of them, belonging to T&G (now International Air Response), and TBM are now used for a large range of missions, from freight hauling upon government request to weapons flight tests, through spraying chemical dispersant against oil spills. Other former airtanker C-130As were cannibalized and their wrecks are lying miserably on airfields in California or Arizona waiting to be, one day, donated to museums or finally scrapped.
A new hope?
For ten years, the USFS large airtanker fleet slowly decreased and consists of only P-2 Neptune and P-3 Orion. As some contractors are working on their own to build the airtanker for the years to come with the BAe 146 jet as main contender, in july 2011, USFS cancelled the Aero Union P-3 contract. The aircraft were grounded immediately and the company closed, leaving the USFS with only an handful of aging Neptunes for the upcoming season, and, of course the not so efficient, and costly, military MAFFS.
In January 2012, at the Aerial Firefighting Conference, in Sacramento, the Canadian company, Coulson Flying Tanker, owner of the very amazing, and very old, Martin Mars water bombers, announced working on a former NASA EC-130Q purchased some months before (8). This aircraft will receive a 4000 US Gallons constant flow tank. Old Hercules versions are banned for USFS contracts (C-130A to E) and no US contractor is able to invest in C-130H’s or C-130J’s. If the Canadian project is a success, it could influence the federal agency, which, in search of solutions, has a new policy recently issued, written specifically for BAe 146.
Is C-130 Hercules still a solution as a fire bomber ? In the near future the Coulson project will hopefully re-ignite interest in the C-130 with RADS. The story of the legendary C-130 has had success, drama, and loss and is now on the threshold of redemption and rebirth. A privately owned Hercules coming out of the smoke dropping retardant with a constant flow tank is still a possibility for the near future… Time will tell.
Many thanks to Jérôme Laval, Ted Meyer, Fritz Wester, Dave Kunz, Tom Janney, Jeremy Tulloa, René J. Francillon, Cyril Defever, Cédric Soriano, Dominique Roosens, Bernard Servières and Fernando Morais.
(1) At the date of writing, end of 2011, early 2012.
(2) Lt Col Paul Mikeal, Major Joe McCormick, Major Ryan Scott David and Master Sgt. Robert Cannon.
(3) The computer is «programmed» with preset door positions and flow rates monitored through the float system to allow the computer to precisely monitor and adjust the door aperture to maintain the proper rate of flow through the doors. The two doors are hinged separately via a rubber hinge at the outboard side of each door. There is also two torque tubes, one with actuating mechanisms for each door.
(4) Pélican is the radio callsign for french Canadairs water bombers. The callsign Hercules was also used for C-130s in France.
(5) Captain Bob Buc, Joe Johnson and Shawn Zaremba were killed onboard Tanker 82.
(6) The crew was Captain Steve Wass, Craig LaBare and Mike Davis.
(7) The investigation was relaunched by NTSB inspector Mr George Petterson. In 2014 his personal involvement in this case was rewarded by the first Walt Darran International Fire Fighting Award.
(8) EC-130Q N427NA was at the Kenosha Military Museum (WI) since its withdrawal from NASA service in 2004.
In December 2013, Evergreen International ceased activity. Awkward timing: their Supertanker, which was stored in Marana, Arizona, had just been promised a “call when needed” contract with the US Forest Service. And these last few years, Very Large Air Tankers (VLAT) which had been awarded call-when-needed contracts have proven very useful, and sometimes even more profitable exclusive contracts came after hard-working seasons.
To be a candidate to these contracts, Boeing 747-100 Tanker 979 had to get back in the air, which needed to find turbojets and perform a C check maintenance operation, a full inspection of the airframe, engines and systems. The whole operation would cost an estimated $1 million; Evergreen postponed the check for a few months… and went bankrupt in the meantime. The aircraft remained in Marana while her owner’s assets were auctioned.
According to the terms of the potential USFS contract, the plane was to yield $75’000 each day it was activated, plus $12’000 per flight hour, and fuel and retardant were to be supplied by the federal organization. Even though USFS promises can be fluctuating, these terms were very attractive. Therefore, former Evergreen employees, most of them deeply involved in the Supertanker project, created a new, dedicated company: Global SuperTanker Services, LLC. When Evergreen was liquidated, they bought the pressurized drop system, spare parts and patents. They also acquired a younger, more efficient aircraft: the new Supertanker, third of its kind, is based on a Boeing 747-400.
N744ST (cn 25308, the 885th 747 to be produced) was built in 1991 as a Boeing 747-446, and first flew on 25 October 1991. Delivered to Japan Airlines the following month and registered JA8086, she would be flying passenger service until 2010. She was then bought as N238AS by AerSale Inc., a company dedicated to second-hand aircraft market, which turned her into a 747-446(BCF) freighter and sold her to Evergreen (as N492EV) in 2012. In November 2013, when Evergreen ceased operations, she was put on storage in Victorville, California.
Global SuperTanker Services chose a 747-400 because of its improved efficiency. 25 years have passed since its inception: the time has now come when big airlines start selling aircraft of this type, and airframes which still have some potential become affordable. N744ST has flown 75’000 hours; a properly maintained 747 can log 100’000 flight hours, which lets her some 25’000 hours to live. As a tanker seldom flies more than 500 hours a year, she could remain active for decades.
With new, more powerful engines than the previous Supertankers, this new aircraft can take-off at a maximum weight close to 400 tons, but she probably won’t meet this weight very often in her new career. Therefore, she will have a more favorable thrust-to-weight ratio, which is obviously interesting for this mission. Her more modern conception also implies rationalized maintenance processes, which will reduce immobilization times and cost for these essential operations. The 747-400 also has a “glass cockpit”, with standard navigation, systems management and operating systems conceived for a two-man crew, while previous Supertankers needed a flight engineer to face the workload of planes conceived in the late 70s.
After being bought by GSS, N744ST quickly went through a C-check operation in Victorville. On 23 January 2016, she flew to Marana, Arizona, to get her modern, gleaming and spectacular new painting. She was christened Spirit of John Muir, after the famous Scottish-American writer/adventurer — who was also a naturalist and a pioneer in the environmental movement.
Her now permanent base is in Colorado Springs, but her first public display was on 22 March 2016 in Sacramento: she was the great attraction during the Aerial Fire Fighting conference, held on McClellan airfield.
During her painting stay in Marana, the release system taken from the first-ever Supertanker was also installed. This needs a bit of an explanation. During the adventures of Evergreen’s Supertankers, two successive tanks systems were conceived. The first one was made of steel and installed on pallets, so it could easily get in and out through the nose door of a Boeing 747-200F, keeping the multi-purpose abilities of the type. This was not possible for the former passenger 747-100s, so Evergreen conceived a new, lighter, aluminum-built mechanism, which was permanently installed through the side cargo door. When the second Supertanker was stored, the whole system was taken off the plane… and when Evergreen was liquidated, it was nowhere to be found!
Consequently, when GSS bought Evergreen’s fire fighting assets, it included only the first dropping system, which had been cleanly stored in Marana. So it is this one, cleared of its now useless pallets but retaining its 75’000 liters capacity, which was installed in the new 747-400.
As the drop system was already approved by the FAA and the Interagency Airtanker Board in the Forest Service, the adaptation should by quick and N744ST could be a candidate to operations as soon as this summer. The first ground drops were made on 30 April 2016 and the next day, she made her first test flight and first aerial drop.
Her crew consisted of Cliff Hale, GSS chief pilot and more importantly former Evergreen Supertanker captain — the man who flew more than 90% of trial and demonstration flights, as well as every operational drop. His first officer was Tom Parsons, an experienced tanker pilot who has flown with Neptune Aviation. A third seasoned pilot has also been hired: in the process of extending his type rating, he was put in charge of rough terrain testing.
For most passenger or freight missions, Boeing 747-400s require only a two-man crew, but fire fighting is another deal. GSS invented a third crew member, named Drop System Operator. Bob Soelberg, GSS Vice President and Supertanker program manager, explains: “Global SuperTanker has felt from the beginning that both pilots need to be focused on flying and communications, not drop system set up. For that reason, we have modified the flight deck to allow Don Paulsen, our Chief Safety Officer and former flight engineer, to act as our DSO.”
Settled in the center jump-seat, Don Paulsen will be responsible for selecting the proper settings for the retardant release system, according to the situation and the requirements from the authorities, and then tell the pilots when the device is ready to drop. In Evergreen’s Supertankers, the flight engineer was in charge of the release system, with some information also displayed on the cockpit’s center console; on the new installation, everything was designed to be in the DSO’s reach. This new job could be offered to former flight engineers as well as seasoned air mechanics, with a proper DSO training course still to be approved by the FAA; meanwhile, a second DSO has already been hired and should also be trained as a first officer.
This new aircraft also has important room for improvements. For example, Supertanker operations not only need an airfield with a long and resistant enough runway; they also need an air compressor, necessary to the pressurized release system. GSS thinks about installing two compressors aboard, so the plane would be able to arm her equipment on her own. New wiring was pre-installed for potential new equipments, notably for new data management requirements — thus, the Supertanker could offer a load of technical data about it systems as well as its structure. Yet, these modifications are a future matter and the aircraft currently still conforms to Evergreen original STC: according to Bob Soelberg, “some pre-positioning of components will allow us to respond to future requests for various data output. This decision [not to make new installations right now] was based on the lack of clear guidance on which system would be most common among the various agencies, as well as our desire not to delay the FAA STC process.”
When the second Supertanker came in Châteauroux, France, in July 2009, Evergreen was already considering night operations, thanks to the craft’s ability to drop higher than conventional tankers and avoid risks of flying too close to the ground. GSS is also working this way and has already made some preliminary studies in that regard, analyzing experience from L.A. Fire Department helicopter pilots, who have been flying by night for years. To add night VFR capabilities to the Supertanker, many evolutions are considered, such as installing enhanced vision systems or modifying the cockpit so it could be used while wearing night vision goggles. No decision has yet be made, as it is still a long-term evolution project.
Amongst VLATs, the Supertanker is also unique in being qualified to work on oil spills, Evergreen having entered this market after the Deepwater Horizon disaster: N744ST will be able to release oil dispersant as soon as she’ll be certified. Since the dropping system is made of two individual, parallel, independent 37’500-liter lines of tanks, GSS says she could even work as a fire suppression tool and an oil dispersant vector at the same time. From its base in Colorado Springs, she could reach the Gulf of Mexico within 3 hours and get anywhere in the world in about 20 hours; as says Bob Soelberg: “Our niche is the ability to respond quickly to areas of the world where local capabilities are limited.”
In the near future, certification should not be a problem and the main question is: will the USFS, which still lacks some fire fighting aircraft, honor the promises made to Evergreen in 2013? That is the hole point, though GSS is also talking to Australia (who has been successfully using one of 10 Tanker’s Douglas DC-10s for the last two years) and to the European Union’s Emergency Response Center.
Evergreen’s history has shown that such a huge plane seldom finds missions big enough for her. Yet, these last few years (and especially the very rough 2015 season) saw very impressive fires and asked for an intensive use of VLATs; particularly, the three DC-10s belonging to 10 Tanker, LLC have proven more than useful. Can the new Boeing 747-400 be a better match for the next years fires? Will the Forest Service follow up on GSS’s arguments? The next few weeks will be decisive for this exciting project.
Translated by Franck Mée
Firefighting. If we split this word, we find “fight”. And indeed, it is a sort of war that is fought against fires: infantry and ground troops, paratroopers jumping in remote areas… And, of course, attack aircraft, named water bombers and sometimes made from ground attack planes, which are guided by observation planes to provide ground firemen with something similar to close air support.
The weapon is of course water, either pure or mixed with additives to turn it into foam or gel, or special fire retardant products. The choice of the weapon has a critical impact on its efficiency, but the way it comes to the ground is just as important: direct attack right on the flames has a blast effect that blows the fire; a semi-direct attack, starting to drop the product just in front of the flames, produces less blast but makes the vegetation slower to catch fire; and an indirect attack means dropping retardant ahead or aside the fire to prevent it from spreading. A good dropping mechanism should be perfectly fit to at least one of these strategies, if not all three of them.
Gravity tanks with simple doors
This is the most obvious system. The tanks include segments, each segment being held by a single door. The carrying vessel (or vector) can make as many drops as there are doors, or heavier single drop by releasing all doors at once.
With a four-door system, we can make one full drop (1+2+3+4) or four separate drops (1 – 2 – 3 – 4), but also two half-loads (1+2 – 3+4 or, if the system allows it, 1+3 – 2+4 to get a wider coverage). In the first case, the massive fall produces a heavy blast, but in the second case, it makes a longer and thinner ground imprint, and other combinations make for intermediate effects. Now, imagine the complex possibilities using the 22 doors in the Martin Hawaii Mars!
This simple conception is very reliable and very efficient for direct and semi-direct attack, to which it is perfectly suited, though it can also be used for indirect attack with acceptable efficiency. It is found on flying boats like Canadair CL-215s and CL-415s, Beriev Be-200s or of course Martin Mars. Many tankers also rely this mechanism, for example most Lockheed P2V Neptunes, Grumman Trackers tanked by Conair and Douglas DC-7s still operating, and many helicopter kits operate on the same principles.
Gravity tanks with constant flow doors
Conceived and developed by Aero Union in the late 80s for their own Lockheed SP-2H (called “Firestar”), constant flow tanks were later designated RADS (for Retardant Aerial Delivery System) when the system was sold for the Lockheed C-130As operated by TBM, Butler and T&G. This principle then set a trend and was produced by several other operators.
Its principle is similar to the traditional gravity tank, but a constant flow tank segments are only meant to steady the load and prevent shifts in the aircraft’s center of gravity. There are only two doors covering the whole tank and allow partial opening, so as to regulate the liquid flow falling down. Instead of setting how many doors should open for the next drop, the pilot using a constant flow system sets two commands, the total amount of product to be dropped and the wanted concentration on the ground. Then, the integrated computer calculates how widely and how long the doors should remain open.
According to experts, the constant flow doors are the most reliable and effective system currently in operation. It is simple, efficient and most of all versatile: selecting a high coverage level and a huge quantity of product, it can make heavy and decisive direct or semi-direct drops; but using a lower coverage level allows to create thin and long retardant lines that act like a firebreak.
Constant flow tanks are now widely used with many different installations: they can consist in fixed on-board tanks or removable devices, completely or partially integrated in the fuselage or just hung outside. Some equipment keep the original abilities of the aircraft, making them multi-purpose, as the removable inside tanks of the Lockheed Hercules (both C-130 and L-100) cargo planes from Coulson Flying Tankers and the external ones found under the Bombardier Q400 liner planes in service with the French Sécurité Civile and the Erickson Aircrane heavy helicopters. Other aircraft use fixed constant flow tanks, as Douglas DC-10s from 10 Tanker, McDonnell-Douglas MD-87 from Erickson Air Tankers, Lockheed Electras from Air Spray, Convair 580s and Avro RJ85s from Conair. It also fits lighter planes like the Grumman Trackers used by the Cal Fire; Air Tractor AT-802Fs and Fire Bosses also used that kind of mechanism, named Fire Retardant Dispersal System. It could also be fitted to flying boats and, provided this project gets real, constant flow tanks should equip the firefighting version of Japan-made ShinMaywa US-2.
Pressurized dropping systems were born in the 70s, when FMC Corporation conceived the Modular Airborne Fire Fighting System (MAFFS) which were later produced by Aero Union. It was actually an adaptation of the system used to spray defoliant and herbicides during operation Ranch Hand in Vietnam: its principle is to pressurize the liquid inside the tank so that it flows more rapidly, giving a higher product density on the ground. This was necessary as the request for proposals required that no modification should be made to the carrying plane for the firefighting device: the flow obtained by just pouring liquid through the rear ramp wasn’t sufficient and the only way to get an efficient drop was to pressurize the tank.
On MAFFS 1 (which uses two nozzles through the open ramp door), the tank was pressurized on the ground, during the retardant loading. The MAFFS 2 update, in the late 2000s, included its own compressor, allowing the pressurization to occur in-flight (it also uses only one nozzle, through the side door, so the plane remains closed during operations).
The MAFFS platforms are mostly used in Lockheed C-130 Hercules, but they are not the only pressurized system: the same principle has been used on Evergreen’s Boeing 747 Supertanker (4 nozzles in the belly, behind the wing).
Pressurized systems share several limitations. The first one is the waiting delay before the tanks pressure is high enough: it makes MAFFS 1 systems remain on the ground several minutes, and requires other planes to fly long enough before a drop can be made. The small diameter of nozzles implies a narrow line, which can be a problem, and even with pressurization the maximum concentration level on the ground is lower than that obtained with gravity tanks. The slower dropping rate also means it takes longer to make a full drop in case of emergency, and it is not possible to obtain a blast effect for direct or semi-direct attacks: pressurized systems are better-suited to indirect attack using retardant product.
A similar system can also be fitted on Erickson Aircrane heavy helicopters: a fire hose can connect to their 9000 liters RADS tank, allowing a near-perfect accuracy. This technique can be useful against forest fires, as well as urban or industrial fires; it is, though, not used often and even rarely installed. Karman also announced that their K-Max, which can carry a Bambi bucket (see further) or a specific drop system to fight fires, could be equipped with a similar device.
Simplicity is not a crime
In the same spirit as the MAFFS, a simpler design has been made using unpressurized tanks, the liquid flowing through nozzles thanks to gravity. It keeps most limitations of MAFFS, but is simpler to operate with no delay for pressurizing the system. Not widely used, its major application is the 45 tons VAP-2 platforms installed inside Emercom’s Ilyushin Il-76s. MBB also conceived a smaller device for the Transall C-160, used in Germany and mostly in Indonesia.
Much more popular is the helicopter bucket, informally called “Bambi bucket” after the most famous models. Bambi buckets are hooked under an helicopter; they can be filled in a matter of seconds by laying into a lake, and drop their content the same way as a simple gravity tank. Different sizes exist, from 300 to an impressive 20’000 liters for the Russian heavy helicopter Mil Mi-26! Very simple and practical, the Bambi bucket suffers of a high sensitivity to wind, like any kind of sling load. Its efficiency depends on the vector’s capacity but heavier models have proven quite versatile. Good abilities associated with reasonable costs and operating simplicity made Bambi buckets very popular all over the world.
An older system should also be noted for historical purposes: the rotary tank. A simple tube, with a side opening, is usually fixed above the pontoons of a float-plane, right below a snorkel that scoops water aside the floats
The opening can be rotated up to fill the tank and carry water, then down to pour it over the flames. This archaic system had arguably small capacities, but it was used on De Havilland Canada Beavers and Otters for years; it was superseded by central tanks fitted with doors.
Other, even more peculiar systems were also considered: for example, a giant watering can was patented in the USA during the 1920s. We really wonder why it was never mass-produced… or not.
The promise of packaged water
In the 1920s, pioneers tried to drop bags filled with water to put out fires. They were not successful, but lately the industry seems to have new thoughts about packaged liquid drops.
The Precision Container Aerial Delivery System, also known as Caylym Guardian, is made of cardboard boxes, each containing 1’000 liters of water or retardant. The boxes are then dropped from the rear ramp of a standard army cargo plane such as Lockheed C-130 Hercules, Alenia C-27 Spartan, Antonov An-26, Boeing C-17 Globemaster III or Airbus A400M, and open mid-air to release their product.
The major drawback of the PCADS is it cannot make an homogeneous retardant line in indirect attack. It also can be a danger for goods or people on the ground in case the box don’t open correctly and it gives the fire some fuel – although a few pounds of cardboard is not a big deal in case of a huge fire. On a more positive side, it should allow an accurate release and be quite efficient for direct attack, though there is little practical information at this time. PCADS also has some undeniable advantages. Since the boxes open mid-air, it is possible to drop them from a higher altitude, which offers safer operation. It is also very cost-effective: it doesn’t need any modification to the cargo plane and the affordable boxes can be stored for years until needed. Therefore, this system fits well nations which only have big fires once in a while and wouldn’t afford an expensive specialized equipment. It is currently in operation with the Romanian Air Force, which uses Alenia C-27J as a vector.
Another example of packaged drop is the Hydrop, made by Elbit Systems. It consists of light biodegradable 200 ml bags, this size being the best compromise between mass, practical considerations and safety of goods and people on the ground. It can be used in any carrying system, either in planes or helicopters, and bags can carry water, gel or retardant. Its major drawback is it needs a special equipment to fill the many little bags, which means costs and operating constraints. Yet, it allows higher drops for better aircraft safety, which its inventor says should allow night operations, and keeps an homogeneous ground imprint. Demonstrations were made in 2014 from a Sikorsky S-61, belonging to Croman and fitted with a special tank; there is no evidence of operational applications since then.
Discussions about the best water bombers usually limit to speed and supposed agility of aircraft, as well as the quantity of product they can carry. The very nature of the product and the system that delivers it are often forgotten; however, reliability and versatility can be important points, which impact both operational and commercial aspects and sometimes explain the wide adoption of some aircraft. To come back to the military analogy, the characteristics of the vector are one thing, but those of the weapon and those of the mechanism that delivers it are just as important. And when all three assets come together, fire quickly cools down.
Translation : Franck Mée