[Forest Fire] Status and Prospect of Forest Aviation Fire Extinguishing Technology

Abstract : This paper expounds the status quo of forest aviation fire extinguishing technology at home and abroad, analyzes the advantages and disadvantages of existing forest aviation extinguishing technology, and forecasts the future development of forest aviation extinguishing technology.

Keywords: Stereoscopic forest fire; Forest aviation fire suppression; Water mist

China is a country with frequent forest fires. Among the many factors affecting the forest ecological environment, the impact and destruction of fire on forests is the most serious. In our country, forest extinguishment is mainly based on manual extinguishing. This type of extinguishing method has poor safety and low extinguishing efficiency and can no longer meet the requirements of current forest extinguishing.

The extinguishing of forest fires in China at this stage is mostly based on the principle of "dragging early and playing small." When there is no effective early warning of forest fires or they are not effectively contained in the early stages, the fires will develop at a rapid rate. Because of the fierceness of the fire, the flames have a large space for distribution and conventional fire-fighting measures have been unable to effectively curb them. According to the situation of fire fighting at home and abroad at this stage, this type of forest fire after the disaster mainly depends on forest fire extinguishing.

1 Research status of aviation fire extinguishing technology at home and abroad

Domestic and foreign aviation fire extinguishing can be divided into fixed-wing firefighting aircraft and fire-fighting helicopters according to different fire-fighting platforms. Fixed-wing firefighting aircraft are generally equipped with water tanks and other equipment, which is loaded with fire extinguishing agent or water, flew over the fire field to throw fire. Fire-fighting helicopters generally use buckets (sling pods) to extinguish fires. Suspended buckets (hanging sacs) are suspended under the aircraft. Extinguishing agents (water or chemical extinguishing agents) are used to extinguish the fire. In addition, there are aircraft throwing fire extinguishers to extinguish fires.

1.1 Overseas Research Status

The research on extinguishing forest aviation in foreign countries started earlier. Many studies have also been conducted on aviation firefighting aircraft and firefighting bombs. The development of their aviation firefighting aircraft has become more mature.

1.1.1 Fixed-wing firefighting aircraft

The Бе- 200 ЧС type firefighting seaplane jointly developed by Russia's “ТАНТК” and “Иркут” companies is equipped with MN-85 weather radar, inertial navigation system and electronic flight instrument system. This kind of aircraft uses the cabin to store water and sprinkle water over the fire. Aircraft load 8000kg , water storage 12m3 ( 8 water tanks, can be divided into one or several airdrops), there is also a 1.2m3 Capacity of liquid chemical agent tank. The Бе- 200 ЧС aircraft has excellent performance in extinguishing forest fires. Currently, the Бе- 200 ЧС aircraft is still unique in the world in aircraft used for forest firefighting .

Canada specifically designed a forest fire-fighting aircraft. The aircraft is an amphibious type, can take off and land on the water; the fuselage is boat-shaped, and there are active landing gear on both sides, the fuselage has two tanks on the abdomen, the aircraft dive to the surface and continue to advance for a distance It can be automatically poured into the water tank via a water scoop, filled with 5 tons of water for 20 seconds ; the aircraft can be at a height of 30 meters above the fire site , with a height of 175 km/h At a speed of flight, the water in the tank can be poured into the fire at the same time or one after another.

C-160 prototype aircraft used in Germany is a military transport aircraft is widely used, which has excellent low slow flight performance, a water-carrying vehicles may be 12,000 L, when the load speed is 385km / h, when the spraying is 450km/h . MMB Aircraft Company developed for a set of special fire-fighting equipment, the entire length of the apparatus 13.8m, the cylindrical tank (extinguishing agent can also be installed) and a trailing end sprinkler tubes, the volume of the tank is 12,000 L, mounted front of the nacelle, when extinguishing with 4 TLEl6 flume water filled, water-filled time 3min42s, then flew over the scene to spraying operation.

The Field Master aircraft was developed by the British Norman Aircraft Company in the late 1970s and was delivered in 1987 . The tank made of titanium alloy is an integral part of the structure of the fuselage, the profile matches the fuselage skin, and the engine is installed in front of the tank. When water is sucked, the airplane is 3m away from the water The height of the flight, while installed in the rear fuselage with suction pipe hanger down a section of a downward rotation, so that the end of the hanger and suction pipe into the water, relying on pneumatic power absorption, 1min to full suction.

1.1.2 Fire fighting helicopter

The biggest characteristic of the Ka- 32A 11BC fire-fighting helicopter developed in Russia is the coaxial arrangement of the propeller, no propeller at the rear and strong maneuverability; the weight is 6t , the effective load is 5t , the water-carrying basket is collapsible, and the hanging basket can be hung when hovering. Put water into the water from the bottom of the basket, and then the solenoid valve closes. If the water source is small, the Power Fill pumping system can be used to draw water through the catheter.

In 1997 , French Aerospace Airlines began launching a fire-fighting helicopter as part of the “special part” of the firefighting in the Mediterranean forest. This is the squirrel-shaped helicopter. A water reservoir was installed below the helicopter fuselage and it was placed between the two landing gears. The reservoir has a flat rectangular shape, with a suction pipe at the bottom left, which can absorb 700kg each time . When a forest fire occurs, the helicopter can use any natural water source. It flies to the surface of the water for stagnation and extends the suction pipe into the water. After the water is filled, the helicopter can fly to the fire to extinguish the fire.

The S-64 Aerial Crane helicopter was a large-scale crane helicopter developed by Sikorsky Corporation of the United States and was put into operation in 1964 . Its greatest feature is the use of a removable pod in the rear of the cockpit, which can fully exert its loading capacity; a capacity of 9500L is installed in the lower middle of the fuselage. The water tank, which has a capacity of 290L The auxiliary fire extinguishing agent box, equipped with a proportional mixer can automatically adjust the concentration of the fire extinguishing fluid; the lower part of the body is equipped with a water suction pipe, which can be from not less than 0.5m in 45 ~ 60s . Drain the water tank in deep water.

AS332 Super Jaguar is a Japanese fire extinguishing helicopter developed on the basis of the AS332LI helicopter. It was designed in 1974 and delivered in 1980 . Its lower body can be mounted fire extinguishing means (AIRATTACKER) a removable, which can accommodate internal 2700kg Fire extinguishing water can be thrown from the air through the lowest water outlet.

1.1.3 Aviation fire extinguishing bomb

A U.S. timber company named Huiyin is developing a 1.2m wide PVC plastic bag. This plastic bag can hold 900kg each Water and flame retardant. Bags filled with water and a flame retardant can be loaded into a box with a parachute, when the case is thrown down from the aircraft the parachute opened, the bag mouth rope lines and also connected to the parachute opens and away from the bag Ground 70m The air will sprinkle water on the fire.

1.2 Domestic Research Status

China's forest fire extinguishing research is still in its infancy, and in the face of the forest fire after the disaster, passive fire extinguishing methods such as evacuating residents and excavating isolation barriers can only be used to control the fire, and fire extinguishers can be used to assist in extinguishing the fire. Most of the researches on firefighting aircrafts involve the introduction of foreign mature technologies and transformations. The relevant research institutes also conducted some researches on airborne firefighting bombs, but no practical reports were found.

1.2.1 Fixed-wing firefighting aircraft

SH-five types of aircraft by the China Institute of Special Vehicle Design, Harbin Aircraft Manufacturing Corporation trial production in 1980 and put into use, the maximum water storage tank of the aircraft cabin is 8.3t, at 100km / h 15s planing speed in time to suck in the water tank; after launch at 50 ~ 100m height, i.e., the reservoir can all be administered within 2 ~ 3s End time; sprinkler coverage area of 20m × 200m.

Y-12 is a light multi-purpose fixed-wing aircraft developed by Harbin Aircraft Manufacturing Factory. The maximum range is 1400km (the maximum standard fuel, 5% of the remaining oil), and the maximum cruising speed is 290km/h . In 2007 , Southwest Aviation Forest Protection Station has tested the modified Y-12 type IV aircraft, and a 1.5t water tank can be installed to conduct air-water sprinkler extinguishing.

1.2.2 Fire fighting helicopter

China's Feilong professional airlines purchased M-26 heavy - duty fire-fighting helicopters (namely Mi -26 heavy - duty fire-fighting helicopters) from Russia , mainly used for carrying out forestry fire prevention tasks in the Northeast. M-26 heavy helicopter fire in the Russian M-26 heavy-lift helicopters modified on the basis of the development of heavy firefighting helicopters. The M-26TC carries a special water container VSU-15 . This container can directly fill the tank with water from lakes and other sources. The maximum capacity of the tank is 8m3 .

1.2.3 Aviation fire extinguishing bomb

Anhui University of Science and Technology designed an explosive water mist fire extinguishing bomb. The fire extinguishing bomb is composed of a bullet shell, salt water and a drug column. When used, the projectile is mechanically projected or airdropped into the fire by using a helicopter, and the water mist is generated over the fire field to solve the problem of short spray distance of the mist-like water. At the same time, the water mist contains a large number of flame inhibitors and the overpressure shock wave generated by the explosion can also assist in extinguishing the fire.

The Heilongjiang Provincial Forest Protection Research Institute has developed a self-directed forest fire extinguishing bomb that consists of a drug core, a fuse, a filler, and an outer package. The shape of the fire extinguishing bomb is a cube. The fuse used for this type of fire extinguishing bomb is a kind of rope wrapped by special drugs. After the aircraft is put into the forest fire, it will ignite and detonate the drug core. The high pressure and high temperature gas generated after explosion can form a columnar shock wave. Then it spreads to the surrounding air, gets accelerated after passing through the combustion, produces a negative pressure effect, destroys the combustion chain, and thus plays a role in extinguishing the fire.

Jiangxi Aviation Forest Protection Station and Wuhan Yushen Fire Co., Ltd. respectively developed airborne dry powder fire extinguishing bombs. The two types of airborne fire extinguishers used dry powder fire extinguishing agents as fire extinguishing materials, and the fire extinguishing agents were sprinkled on the fire field to initiate fire extinguishing using methods of throwing and touching the ground, but no application report was found.

In addition to the above-mentioned domestic and foreign aviation fire extinguishing methods, sometimes people use the method of artificially increasing rain to extinguish the forest. However, this method has a large limitation, and has strict requirements on the coverage area and the degree of water content of the cumulonimbus, and is subject to gas. The influence of the movement direction and speed of the regiment is also great and it cannot be widely used for forest fire prevention and control.

1.3 Execution Status of Fire Extinguishing Agents in Forest Aviation Extinguishing

Common fire extinguishing agents include liquids, solids, and gases. The forest fire burning environment is very different from other types of fires. Not all fire extinguishing agents can be used for forest fire extinguishing. Fire extinguishing agents commonly used in forest aviation at home and abroad are liquid and solid.

1.3.1 Water extinguishing agent

Fire extinguishing agents commonly used in forest aviation fire extinguishing include water and water-based extinguishing agents containing additives.

Water has a strong heat absorption capacity and has a significant cooling effect on the combustion materials. Water vaporization can generate a large amount of water vapor, which can squeeze out and prevent air from entering the combustion zone and reduce the oxygen content. Because water can infiltrate wood, the extinguishing of forest fires is quite effective. Therefore, most of the above-mentioned domestic and foreign aircraft fire extinguishing techniques use sprinkler fire extinguishing methods.

In addition, adding additives in water, changing the physical and chemical properties of the water can improve the fire extinguishing effect. Additives are divided into three types: absorbent particles, surfactants, and thickeners. Some fire extinguishing bombs used by the Russian-developed АСП- 500 air fire extinguishing device and the US S-64 “air crane” fire-fighting helicopter used this extinguishing agent.

1.3.2 Solid fire extinguishing agent

Solid fire extinguishing agents include dry powder fire extinguishing agent and aerosol fire extinguishing agent. The main fire extinguishers for aviation forests are ABC dry powders in dry powder fire extinguishing agents. They can generate metaphosphoric acid, phosphorus pentoxide and polyphosphates when they are burned. The solid surface is melted and forms a glassy coating that blocks the air and smothers it. In China, dry powder fire extinguishing agents are widely used in forest fire extinguishing. Two types of airborne dry powder fire extinguishing bombs developed by Jiangxi Aviation Forest Protection Station and Wuhan Yushen Fire Protection Co., Ltd. are the fire extinguishing agents.

2 Forest Aviation Fire Situation Analysis

2.1 advantages of forest aviation extinguishing technology

At present, the forest fire extinguishing technology advantages mainly include the following points:

( 1 ) It is highly mobile and free of terrain restrictions. Relying on the aircraft's maneuverability can reach the mountainous areas where general fire-fighting forces cannot reach, and can perform fire-fighting operations in a timely manner. After the disaster, the forest fire has a huge scale and its destructive power is very strong. Generally, the fire extinguishing force is difficult to fight and the aviation fire extinguishing is almost the only effective fire extinguishing method.

( 2 ) The fire extinguishing area is larger in one flight. The existing aviation firefighting aircraft has a relatively large carrying capacity, and the number of fire extinguishing agents carried in one flight is also large, so that the forest fire field that can be covered by the spray extinguishing agent is also large.

( 3 ) Firefighters are relatively safe compared to entering fires directly.

2.2 Inadequate forest fire extinguishing technology

2.2.1 Insufficient forest firefighting

( 1 ) Aviation spraying is not effective. After the disaster, the forest fire has a very wide range of space. The general height reaches 10 to 20m , and the length of the fire line in the forward direction can reach 50m and the temperature can reach 900 °C . Due to the need to ensure the safety of the aircraft, the aircraft can only operate at a certain height above the fire when the fire is extinguished. This leads to a high watering height and the water is affected by the intense heat flow over the fire field during the landing. Part of the fire extinguishing agent (liquid extinguishing agent) ) In the process of landing on the fire, it is heated and blown out of the fire. As a result, the amount of fire extinguishing that really acts on the fire is small and the fire extinguishing effect is not good.

( 2 ) The utilization rate of aviation sprinkler water is relatively low and the cost is relatively high. The water utilization rate is too low, which results in poor fire extinguishment in single flight. Therefore, it is difficult for forest aviation fire fighting to be popularized as a conventional fire extinguishing method.

( 3 ) The fire extinguishing effect depends on the aircraft's carrying capacity. The area where an aircraft sprays fire extinguishes is proportional to the amount of water it carries. Theoretically, the more the fire extinguishing agent the aircraft carries, the better, but this will in turn lead to high development and flight costs for large-capacity aircraft.

( 4 ) The location of the airport is usually far away from the fire site and it is inconvenient to add fire extinguishing agents. After a flight is extinguished, the aircraft needs to return to a specific place (airport or water source) to supplement the fire extinguishing agent, and these sites are often far from the fire, which reduces the aircraft's extinguishing efficiency.

2.2.2 The lack of airborne firefighting bombs

After analyzing the current technology of airborne fire extinguishers at home and abroad, the author finds that these fire extinguishers are less effective in extinguishing forest fires. Most of the existing airborne fire extinguishing bombs are triggered by fire explosions or touchdowns. They are initiated at or near the ground or are still above the fire. The detonation over the fire field is equivalent to spraying fire extinguishing agent and the fire extinguishing effect is not good. The detonation caused by touching the ground causes the fire extinguishing agent to spread close to the ground and only acts on the surface fire within a few meters from the ground. When the forest fire expands, the fire will become a three-dimensional fire structure consisting of underground fires, surface fires, and crown fires. Among them, canopy fires are the most dangerous, and fire extinguishing bombs that detonate close to the ground cannot effectively extinguish canopy fires.

2.2.3 Use of forest fire extinguishing agents

( 1 ) Use of chemical extinguishing agents. Some of the above-mentioned airborne fire extinguishing bombs and firefighting aeroplanes use chemical extinguishing agents such as liquid extinguishing agents and dry powders, and the large-scale use of chemical extinguishing agents will cause environmental pollution in forest areas. For example, in 1987 , Switzerland used a large amount of extinguishing agents to extinguish a fire in a warehouse, and the extinguishing agent raffinate flowed into nearby rivers and caused all fish to die. In 1969 , the United States used 330,000 gallons of fire extinguishing agent in a forest fire in Alaska. When the fire was cleared, many of the frogs in the river near the fire were killed. In addition, the use of fire extinguishing agents in the air or on the ground may be in direct contact with firefighters who subsequently enter the fire scene. Some of the medicaments are toxic and may cause irritation to the skin on the skin, and may cause serious poisoning and death.

( 2 ) Use of water. Most existing forest aviation fire fighting technologies use direct spray water. Such a fire extinguishing method not only fails to extinguish the fire, but also wastes water and raises the cost of extinguishing the fire.

3 Forest Aviation Extinguishing Technology Outlook

In view of the deficiencies of the current forest aviation fire fighting technology, the author believes that the future forest aviation fire fighting technology should develop in the following directions.

3.1 water fire

Because chemical fire extinguishing agent pollutes the environment and water has an infiltrating effect on the firewood, the use of water to extinguish forest fires is the best choice. Today, with the emphasis on harmonious development of the ecological environment and human beings, water will be the development direction of forest fire extinguishing agents.

3.2 Fine water mist extinguishing

In response to the problems of low utilization rate and poor fire extinguishing effect of existing air-showing sprinkler water, the water can be turned into a fine mist to extinguish the forest fire.

Water mist technology is developed on the basis of the last ten years from the American scientific community, the business community and the fire department administrative application of water mist fire suppression in the 1940s on environmentally friendly fire extinguishing technology. Water mist fire extinguishing has the following outstanding advantages compared with other fire extinguishing agents:

( 1 ) Advanced fire extinguishing mechanism and good fire extinguishing effect. Water mist fire extinguishing has both the role of cooling and anaerobic. For canopy fires with a temperature of up to 900 °C , the volume of water vapor can expand by more than 1,700 to 5,800 times due to the large surface area of ​​the water mist and the vaporization rate . Vaporized steam can enclose and cover the entire forest fire field combustion area. The forest fire extinguishes due to lack of oxygen; on the other hand, the rapid cooling after water vaporization, the vaporization speed of the water mist is rapid, and a large amount of heat can be absorbed from the surface of the forest fire, the cooling rate is 10 times faster than the conventional spraying , and the temperature of the fire source can be increased. A sudden drop to achieve the purpose of fire fighting.

( 2 ) High water utilization rate. Water mist fire extinguishing has very little water consumption. The fire extinguishing water consumption is only 1 % to 5 % of the traditional firefighting measures , and the fire extinguishing efficiency is 2,000 to 3,000 times that of traditional fire extinguishing methods , which greatly improves the fire extinguishing efficiency of water and overcomes The disadvantage of difficult water supply in forest firefighting can relieve the contradiction between aircraft firefighting effect and flight cost while increasing the utilization rate of firefighting water in forest firefighting.

( 3 ) It can absorb smoke and poisonous gas, providing security for the entry of ground firefighters.

( 4 ) Safety, environmental protection, cheap, no harm.

The fire extinguishing effect and the effect on the environment after extinguishing the fire are the best fire extinguishing materials, and the fine water mist is the best mode of action.

For the problem that the airport is usually far away from the fire, small helicopters can be used as forest aviation fire fighting aircraft, and a simple helicopter airport can be deployed near the forest. Before filling the tanks and buckets before the disaster, the aircraft can be supplemented with fire extinguishing agents after fire extinguishing. Fill water, or directly make an airborne fire extinguisher, and replace the water tank or load the fire extinguishing bomb directly after the aircraft returns to the fire.

In summary, when a forest fire occurs, an aircraft is used as a delivery platform, water is used as an extinguishing agent, and fine water mist is the best combination of choice as its mode of action. The use of a detonation fire extinguishing bomb can produce a fine mist, and it is easy to supplement. This will also be the development direction of forest fire extinguishing technology.

4 New Type of Airborne Fire Extinguisher

Stereoscopic forest fires that have already formed disasters are spreading rapidly and causing great harm. In order to control fires in time and avoid even greater losses, the use of aviation fire extinguishing is almost the only means. The fine water mist has a good effect of extinguishing the fire, the water utilization rate is also high and there is no pollution, and it can carry more water under the limited aviation carrying capacity, which can increase the extinguishing efficiency and save valuable time. Therefore, in combination with the principle of water mist extinguishing and the rapid maneuverability of aircraft, detonation is used to generate fine water mist and distribute it throughout the fire space, and a new type of air-launched fire extinguishing bomb is developed to combat the forest after the disaster. The fire and the reduction of disaster losses have important practical significance.

New types of airborne firefighting bomb research should include the following aspects:

( 1 ) Selection of detonation location. Through the simulation of the fire field, select the appropriate spray location and distribution pattern of fine water mist to achieve the best fire extinguishing effect.

( 2 ) Detonation mode selection. Special design fuze to ensure that the airborne fire shells can be in an ideal standoff detonate, so that after the initiation of water mist fire shells to achieve the desired distribution effect.

( 3 ) Selection of storage and transportation methods. Explore ways of storing, transporting and throwing fire extinguishing bombs to ensure that the fire extinguishers are in good condition and have the best overall efficiency.

5 Conclusion

The current methods of extinguishing forest aviation at home and abroad were studied. The advantages and disadvantages were analyzed. Combined with the characteristics of water mist extinguishing theory and forest fire, the fire extinguishment technology of airborne water mist extinguishers was introduced. This article proposes a new type of fire extinguishing ideas, hoping to provide a certain reference for future research and design of airborne water mist fire extinguishing bombs.

This article comes from Volume 41 of "Forestry Machinery and Woodworking Equipment".