An internal tank for military helicopters

Chinook internal water tank
Artist's depiction of a Ch-47 Chinook with an internal tank dropping on a fire.

A California man who owns two drag racing teams has designed and built some internal tanks for military helicopters. As we wrote on Wildfire Today on January 3 when discussing the tilt-rotor Osprey aircraft, the CH-46E Sea Knight and CH-53

CH-53 dropping on a fire
A CH-53 Super Stallion drops on a fire on Camp Pendleton in California, July, 2007.

Super Stallion helicopters operated by the Marine Corps have been used on fires in California since 2007 during periods when Cal Fire is unable to handle the fires with their own aerial assets. These helicopters transport water to the fire in an external bucket, but since buckets occasionally are accidentally released or otherwise fall from helicopters, there are restrictions on carrying the external loads over roads or populated areas. Internal tanks are considered to be more safe than external loads if there is a concern about dropping a 2,000-gallon tank on people.

Concerned about the external load safety issue, the California Department of Forestry and Fire Protection, Cal Fire, contacted Tom Jaroszek of Merced, California, who owns TMR Fabrications and two drag racing teams. Mr. Jaroszek agreed to design and build an internal tank for the CH-47 and CH-53 at no cost to Cal Fire with the understanding that the agency would then use them on an emergency rental agreement if needed for fire suppression.

Someone familiar with the internal tank who has no financial association with TMR Fabrications sent us the article below describing the project:

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MILITARY INTERNAL FIRE TANK

As early as 1960 the Army Air National Guard of California has been assisting public agencies in aerial fire suppression and support. In those years, UH-1 helicopters with an external bucket were the helicopter most likely to be seen on fires with military livery. In the 1970’s the use of much larger military helicopters started to appear during periods of extreme fire weather and the depletion of public and private air resources. In the 1980’s the use of the military helicopters on fires was becoming a common place usually for a week or two, maybe once or twice a fires season.

Several factors in recent years have placed a demand for large Type 1 military helicopters to be utilized more frequently and for longer periods of time. The forest eco-system seems to be more prone to the development of larger more destructive fires. The significant reduction in logging and people moving from urban centers to “the mountains” in tens of thousands has certainly had an impact on suppression capability. Light hand on the land policies and the restrictive use of prescribe fire has not help the unwanted fire picture. Because of the continuing use of large military helicopters projected into the future, a committee of aviation fire personnel was tasked with making the CH-47 Chinook a more productive and without limitation aerial fire fighter.

With the dramatic reduction of heavy Federal initial attack air tankers throughout the West, the ability to stop evolving “new start” fires from escaping containment was one of prime consideration for the military enhancement program committee. The committee included military personnel, Forest Service, Cal Fire, private sector business and engineering people.

The answer was the development of an internal self-contained, motorized vehicle that could be driven into a CH-47 Chinook or CH-53 Sea Stallion helicopter. The tank would have to drop 2,000 gallons of water in less than eight seconds. The internal tank military enhancement committee drew out the specifications and basic design which were awarded to T.M.R. Fabrication in California for engineering and manufacturing. T.M.R. although associated with several fire development projects is more noted for building race cars, dragsters that go 1,000 feet in four or five seconds. The new internal tank has a top speed of two miles per hour. When driven up the ramp of a helicopter its “shut-down speed” is five feet per minute. After entry into the helicopter the tanks hydraulic actuators lower the tank into position for attachment of cargo chains. If you ever had the privilege of looking inside a C-119 or C-130 air tanker the retardant tank you would have seen is the same basic design, a large aluminum box with lots of vents on top and adequate inside baffling to prevent sloshing. The internal tank can be loaded or unloaded in less than fifteen minutes. Configured to transport personnel only requires returning the transport seats in the down position.

The Chinook internal tank is twenty-four feet overall length four feet wide and four feet in height. Total water tank capacity is 2640 U.S. gallons. A forty gallon system provides that chemical option. The CH-53 tank is the same design but dimensions are a little different. As mentioned earlier in this article this fire apparatus is fully self contained. Nothing is connected to any of the aircraft systems. The heart of the tank is a bio-diesel power plant that provides all the energy to operate the two hydraulic Hyra-Tech 1,100 gallon per minute pumps that are Cam Lock connected to 5 inch flexible fill hose that pumps water into the tank. The pump and hoses connect to the aft portion of the tank and are twenty-six feet overall length. The bio-diesel power plant exhaust system is directed into the tank and is purged with each drop. This power plant runs constantly, either pumping or in hydraulic cooling recirculation.

In addition to hover filling from a shallow water source the internal tank has air tanker 3 inch Cam Lock fittings with solid poly 3 inch hoses to “drive in” and fill from a tanker base. The gate system to release the water sits over the center hole of the Chinook. The hook door is left in place and back, however the hook has to be removed which takes about a ten minute. An interesting feature of the internal tank is that it carries 300 feet of 3 inch hose with national hose threads which allows the flight crew to land and connect to a hydrant. A pumper connected to a good water source works just as well.

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More information from Bill:

I asked the author some questions about the tank and here is what we were told.

He said a photo of a tank is not available because TMR Fabrications will not provide one due to patent issues.

Two tanks have been built, one was sold to Able Fire Support. The other is waiting for Military approval from Redstone Arsenal and the Fort Rucker Institute Rotary-Wing Aviation Research Unit.

The purchase price of the tank is unknown, however Mr. Jaroszek’s understanding is that the tank would rent for about $3,000 per operational period.

The purpose of the power plant is to supply hydraulic energy to the two hydraulic water pumps at the end of the two 26-foot drafting hoses which fill the tank. The power plant is kept running in order to cool the hydraulic system.

Both the Chinook and the CH-53 helicopters have “hook holes” in the belly. The one on the Chinook is 30-inches square. When an external load is being carried, a military crew person lays on their stomach to monitor the load. When the water tank is used, a 20-inch long chute is attached to the tank and inserted through the hook hole.

The drop procedure:

[When a Chinook is carrying a conventional external water bucket]  during fire operations [it is crewed by] two “carded” military fire pilots, two flight engineers, and one CalFire helitack captain. The flight engineer at the right door calls the alignment and drop. The other flight engineer is in charge of the bucket. Is it filling properly, amount of fill distances in height above water etc. and on command pushes the button to release water.

With the internal tank the same will be true except the hole flight engineer will operate the fill pumps and will still make sure the water is released.

The tank is not pressurized like the systems on military MAFF air tankers and Evergreen’s 747 air tanker. Gravity is used to expel the water from the tank through a 21-inch drop valve, dropping 1,800 gallons in six seconds or 2,000 gallons in 8 seconds.

Author: Bill Gabbert

After working full time in wildland fire for 33 years, Bill Gabbert now writes about it from the Black Hills.

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