How Helicopters Fight Forest Fires with Underbody Tanks

Underbody tanks in helicopters, one of the equipment of helicopters in fighting and intervening in forest fires: 

Underbody tanks in helicopters are special equipment used in fighting forest fires. These tanks are installed under the fuselage of the helicopter within 20-30 minutes, and the underbody tank fills itself in 40-45 seconds depending on the size of the tank and the snorkel's capacity to draw water from water sources (lake, river, pond or pool) with the snorkel it has to fight and intervene in the fire, and is now ready to carry water to the fire. In helicopters, the equipment for adding and mixing fire retardant chemicals to the underbody tanks is almost standard. There are two types: fixed under-fuselage tanks and fixed under-fuselage tanks that can be flexed.

In the photo below, the Sikorsky S-70A Firehawk fixed underbody water tank of the Los Angeles County Fire Department is throwing water at its target. The fixed under-fuselage tank has a water carrying capacity of up to 3785 liters and can be filled in 45 seconds on average. The landing gear of this helicopter has been upgraded to increase the capacity of the under-fuselage water tank.

In the photo above, Aerotech Australasia Pty Ltd's S-70 Black Hawk helicopter is equipped with a flexible under-fuselage Helitak FT4500 tank and snorkel.

The water carrying capacity of this under-fuselage flexible tank is up to 4500 liters. When the flexible underbody water tanks are mounted on the helicopter, there is no need to raise the landing gear and helicopter skids.

Advantages of using underbody tanks in helicopters:

Increased Capacity: 

Under-fuselage tanks can usually carry larger quantities of water or fire retardant chemicals. This ensures an effective response in firefighting.

Pressurized Distribution: 

Underbody tanks can be pressurized, which allows for more controlled and precise water distribution compared to buckets.

Targeting: 

Targeting and water throwing precision capability is higher. 

Training and orientation: 

Helicopter pilots who will use underbody tanks in firefighting are easier to train than helicopters equipped with bucket systems, and they can adapt to the new mission more quickly.

The T-70 Black Hawk is ready to go to the fire zone after taking the required amount of water from the portable pool through its snorkel. As of April 2024, there are 3 T-70 Black Hawk helicopters in Turkey that have been tested and equipped with the Helitak FT4500 kit. 2 of these helicopters belong to the Gendarmerie General Command. 1 of these helicopters belongs to the General Directorate of Forestry Aviation Department. 

The TAI T-70 Black Hawk helicopter belonging to the Gendarmerie General Command of the Ministry of Interior of the Republic of Turkey is equipped with a Helitak FT4500 tank and snorkel. The T-70 Black Hawk has descended to draw water from the portable pool with its snorkel and has submerged its snorkel into the portable pool (Pumpkin Tank). This test flight took place on September 14, 2023.

Pictured above is a Sikorsky S-70A Black Hawk of Aerotech Australasia Pty Ltd. in Adelaide South Australia near Parafield Municipal Airport on November 9, 2023. "Patches II" is the fourth S-70A Black Hawk helicopter to join the Aerotech fleet. It is seen taking off in a Helitak FT4500 designed and built in Australia for the bushfire season. The tank-mounted snorkel is collected and secured to the helicopter. Photo by Phil Hosking

Open Water Areas: 

Suitable for open water areas and urban-wildland interface.

Higher Airspeed: 

Underbody tanks in helicopters allow helicopters to travel at higher speeds (e.g. 145 knots or faster) from the water source to the fire.

Maneuverability:

Helicopters flying with underbody tanks allow pilots to maneuver more aggressively, especially after dropping water on the target. 

Night Firefighting: 

Underbody tanks can make night firefighting operations more reliable. Compared to a bucket helicopter, a helicopter equipped with an underbody tank provides a safer flight due to the absence of buckets and cables connected to the bucket. 

Disadvantages of using underbody tanks in helicopters:

High cost: 

They are considerably more expensive than bucket systems.

Weight: 

They are larger and heavier than buckets in bucket systems and this weight increases fuel consumption.

High Current Draw: 

Underbody tanks require a significant amount of electrical power (90-125 amps) to operate.

Maintenance: 

Maintenance requirements for underbody tanks can be more complex. Maintenance costs can be high.

Night Firefighting with Underbody Tank Assistance: 

A helicopter equipped with an underbody tank can provide more reliable night firefighting operations than a helicopter equipped with a bucket system. However, flying the helicopter at night can be risky due to the need to maneuver lower than bucket-equipped helicopters in order to effectively drop water. In night conditions, visibility conditions can be very poor and the depth perception of pilots can be adversely affected, resulting in fatal accidents. The most important thing to remember is that the first priority of helicopter pilots who will intervene in the fire at night is to intervene in the fire without risking flight safety. Even in cases where night flight conditions are not favorable for more and more effective water disposal, pilots may take excessive risks due to various reasons (operational pressure, fatigue and stress, compatibility problems with night vision equipment, contract terms, pressure on helicopter crews and pilots by bureaucrats who do not know the business of firefighting with helicopters, negative news and criticism in the press and social media, pilots' desire to extinguish and control the fire as soon as possible), resulting in fatal accidents that do not end well.

In the photo, a Sikorsky S-70A Firehawk equipped with an under-fuselage tank fighting a fire at night from very low altitude