Drop it like it’s hot: buckets versus tanks
Buckets and tanks both have advantages when helicopter firefighting – but which has the edge? Barry Smith investigates
Experiments with dropping water from helicopters began in the late 1950s. By the early 1960s, several companies had developed internal and external tanks, as well as buckets, that could be suspended from cargo hooks. Since then, debate has continued to rage over which system is best: tanks or buckets. Barry Smith spoke with many operators of both systems, finding that each has its place in aerial firefighting.
A question of location
Geography plays an important role in the decision to use buckets and tanks. In areas of tall trees, a long line between the bucket and the helicopter can safely allow the helicopter to draw water. In many countries, sling loads are prohibited from being used over urban areas, due to the danger of the load being inadvertently dropped. Therefore, tanks are used near urban areas. That is why most public safety helicopters in Southern California take the tank option.
“Our decision to use tanks comes down to the market we wanted to pursue,” said Mel Ceccanti, Director of Rotorcraft Flight Operations for Coulson Aviation of Port Alberni, British Columbia. “We are active in both Australia and the US where tanked helicopters are very popular with our customers. Also, many of the contracts being put out by the United States Forest Service are asking for tanked helicopters. Tanks allow us to fight fires in both urban interface and wilderness areas. They also offer other advantages, such as increased airspeed from water source to the fire. We can cruise at 145 knots or faster with the tanked CH-47 en route to an incident.”
Ceccanti continued: “In addition, we operate fixed-wing large air tankers with our proprietary internal RADS tank. It just made sense for us to use the same design and adapt it to our CH-47 Chinook helicopters. We also knew from the beginning of our CH-47 program that we wanted to get into night firefighting, which would require a tank versus a bucket. We had been doing night water drops in Australia for several years with a tank-equipped S-61. So, it was a natural progression for the CH-47.
“We also knew for initial attack operations, such as our Quick Response Force program in southern California, that a bucket would just take too long to deploy. With our internal tank and retractable snorkel, we can arrive at the scene of a fire much faster, and not have to find someplace to land and set up a bucket,” Ceccanti concluded.
Always on call
For Coulson, there is no off-season. They fight fire all year round, typically flying in the US for six months, then sending the aircraft to Australia or South America for the rest of the year. They do have a couple of CH-47s with no tanks installed, and can do bucket work if that is what the customer prefers. Coulson is also looking to modify their tanked helicopters to use a bucket, making them more versatile. The tank can be easily removed in about 30 minutes to reduce weight if they need one.
We have a huge demand for our tanked helicopters all over the world
The tank system is controlled by an onboard computer which can run diagnostic checks. It has a cellphone connection that can relay diagnostics, as well as transmit data on every water or retardant drop – such as the exact location and the amount. If there is a problem, a fault code is displayed. This information can be accessed by the main office, from any aircraft located anywhere. They can also update or change the computer's software remotely.
“We have a huge demand for our tanked helicopters all over the world,” explained Ceccanti. “We could double our fleet of tanked CH-47s and would have no trouble finding contracts for them.”
Bambi in high demand
By far the most commonly used is the Bambi Bucket, made by SEI Industries of British Columbia. They have sold over 1,000 in 115 countries. First produced in 1982, Bambi Buckets come in sizes from 270 liters to 9,800 liters. One of the initial disadvantages was the water source had to be deep enough to submerge the entire bucket. For many years now, SEI has offered buckets with pumps mounted in the bottom, so water sources as shallow as 0.5 meters can be used.
The US military is a prolific Bambi Bucket customer. Many of the state Army National Guard UH-60 and CH-47 units use them for firefighting. Long line sling loads are a regular part of military helicopter operations, so it is an easy transition. In addition, the helicopters do not require any permanent modifications to use the buckets.
“We use the Bambi Max on our five Bell 212s and the regular Bambi Bucket on our other helicopters, which are Airbus AStars and Bell 407s,” stated Andrew Bradley, Director of Business Development for Blackcomb Helicopters of Whistler, British Columbia. “We do mostly ad hoc, or call-when-needed contracts, as opposed to dedicated exclusive use. This makes for a quick turnaround when an aircraft is on a long line construction job. The crew just picks up a bucket and flies to the fire. A tank would require more time to attach. If the tank were to be left mounted to the helicopter, that would reduce the weight the ship could carry for other missions.”
British Columbia is very heavily timbered, which can make the use of a tank problematic to fill
The geographical factor is again prevalent. “British Columbia is very heavily timbered, which can make the use of a tank problematic to fill,” Bradley continued. “Whereas a bucket with a 100ft or 150ft tether can dip in a water source surrounded by tall trees. Plus, the pilots are used to long line utility work, so they have the necessary skills to safely use buckets in the forest. This allows water sources to get much closer to the fire, or quickly move from one source to another around the fire. For us, the versatility of the bucket outweighs a tank in most work situations.
“With the Max model, we can do multiple drops with one load of water. It also allows us to take a full bucket every time, then drop some out as we lift out of a dip site. This allows us to safely lift the maximum amount of water, depending on the density altitude and fuel load of the helicopter – and still keep a safe power margin. We don’t have to guess how much to fill the bucket, like you do with buckets that cannot do multiple drops,” said Bradley. “The Max has a pump, so we can use more shallow water sources in the more arid regions of western Canada.
“Dipping a bucket in a river can be more difficult than a still water source, such as a lake. In fast-moving water, the bucket can get dragged along, which then drags the helicopter. If it then hits an underwater obstruction, like a log, it can get caught. So, we try to find a back eddy or side channel where the water is not moving as fast, so we can better see if there are any underwater snags,” he concluded.
The versatile hybrid
Helitak Firefighting Equipment of Queensland, Australia, has developed what one might call a hybrid tank/bucket. It consists of a carbon-reinforced resin base, with an expandable bag of heavy vinyl material. When in the stored position, the unit is no more than 18in tall. Equipped with a hover fill pump, the bag expands below the helicopter as the water is pumped into the bag until fully extended. When the water is dropped, the bag is retracted into the base by a metal lattice-work. The height of the bag when extended gives a high head pressure, allowing the water to penetrate thick foliage.
Helitak makes these units for light, medium and heavy helicopters, with capacities ranging from 1,000 to 10,000 liters of water. The pump, hydraulic and electrical equipment are all stored in the tank, so it is completely self-contained and can be mounted or removed in about 30 minutes with no helicopter modifications. This type of tank is especially useful for aircraft with wheeled landing gear, that don’t have enough clearance to mount a traditional tank on the belly.
“We were the first user and did the testing for FAA certification for Helitak’s UH-60 3700 liter tank,” explained Brad Bauder, owner of High Performance Helicopters of Redlands, California. “We have been using it for three fire seasons. It has a good drop pattern with two large doors and penetrates thick tree canopies well. There aren’t many options for tanks for the UH-60. There is the very expensive Firehawk with modified landing gear. There is an internal tank that fits in the cabin and drops out of the cargo hook door in the floor of the cabin. The drop pattern is rather thin and does not do well with canopy penetration. Then there is the Helitak system, which works best for us. We do a lot of firefighting in the Pacific Northwest, dealing with tall timber and a thick canopy.”
Bauder continued: “We fly about 130 knots with the tank full, filling the 3,700 liters in about 40 seconds. We can fill less than the full amount, based on the density altitude and fuel load. The computer control system makes multiple drops with variable patterns. Also, it is not difficult or expensive to mount the system to the belly, and we can remove the tank in about 20 minutes. We have two tanks for our one Black Hawk, so if there is a problem with one, there’s a back-up ready to go. Additionally, it usually only takes a couple of hours of flight training to get a pilot used to the Helitak system, if they have experience of other tanked helicopters. We are very satisfied with the Helitak tank.”
There is no one-size-fits-all solution to delivering water to a fire.
There is no one-size-fits-all solution to delivering water to a fire. A mixture of helicopters with tanks and buckets gives the maximum amount of flexibility. Bucket ships can be used in tall timber or confined dip sites, while the tanked helicopters are suitable for open-water sites and in the urban wildland interface.