EP0785809A1

EP0785809A1 - Process and device for fighting fires from the air

Info

Publication number: EP0785809A1
Application number: EP96938907A
Authority: EP
Inventors: Winfried Rosenstock; Egon Karp
Original assignee: Karp Egon; Rosenstock Winfried
Current assignee: Karp Egon; ROSENSTOCK, WINFRIED
Priority date: 1995-08-14
Filing date: 1996-08-13
Publication date: 1997-07-30
Also published as: DE19680698D2; AU7617596A; AU724899B2; WO1997006858A3; CA2202486A1; WO1997006858A2

Abstract

A container with a wall capable of bursting (in particular a drop-shaped or bubble-shaped bag made of a thin plastic film) and filled with extinguishing water is used to fight fires from the air, in particular forest fires. A bursting charge with a fuse is arranged inside the extinguishing water. The bag is brought to the fire source by a helicopter. The bursting charge is then ignited closely above the fire source, spraying the extinguishing water into a misty cloud of microscopic droplets that abruptly extinguishes the fire source. The bag is preferably dropped by the helicopter at a higher level above the fire source and the bursting charge is ignited during its free fall shortly before the bag hits the fire source, either by remote radio control or by means of a time fuse that can be adjusted to a predetermined height. The time fuse may be activated at the same time as the bursting bag is dropped from the helicopter by an igniting source located in the helicopter and linked to the time fuse by an igniting cable that is detachable from the helicopter.

Description

Fire fighting method and apparatus from the air

In recent years there has been a steady increase in the number of forest and wildfires registered worldwide. Simultaneously with this trend, the size of the destroyed area per fire is increasing steadily. Regions in the northern hemisphere of the world are particularly affected, in particular the boreal coniferous forests of Canada and the tundra of the Eurasian landmass, and the pine stands in the Mediterranean area are less pronounced. The global, harmful emissions from forest fires are now estimated to be around 50% of the total.

The common methods of fighting large fires, above all forest fires, which have a strongly chaotic character and spread out front-like at high speed, are still insufficient to extinguish the corresponding fires quickly and completely. In the most favorable case, forest fires have so far only been contained. The reasons for this are extremely complex. The ground-based control of large fires is carried out in principle with the same equipment and in the same way as a fire-fighting operation on buildings within a residential area that is fully developed in terms of infrastructure. In the case of forest fires, however, is usually neither of an adequate water supply, a sufficient number and sufficiently developed access routes for the fire engines. The latter defect often goes hand in hand with general inaccessibility of the source of the fire and in any case requires a selective approach against the front-like fire and prevents it from being extinguished completely.

Fire fighting from the air, which has been in existence for a long time, improves the accessibility of the source of the fire, but has so far not contributed to decisive progress. The raining or dropping of water from the air by means of airplanes or helicopters has proven to be inefficient despite high financial expenditures, because on the one hand this type of control takes place only extremely selectively and on the other hand it is associated with a very pronounced inaccuracy in the aim of dropping is. Due to the strong smoke development and turbulence, there are always obstacles to the use of air, which makes a sufficient approach to the fire from the air and in many cases an extinguishing success impossible.

A fundamental problem, which is particularly disadvantageous in view of the scarcity of water when fighting forest fires, is the inadequate efficiency of the use of extinguishing water, since according to the methods which have been customary to date, only about 10% of the extinguishing water also has a fire-extinguishing effect. A large part of the water used seeps away unused in the ground or remains in the form of large pools inaccessible to the ground for every further extinguishing operation. This applies to the use of air support as well as that of fire engines.

The object of the invention is to improve fire fighting from the air in such a way that both a significantly higher extinguishing effect of the water used and a considerable increase in the fire area extinguished with such a single use of air are achieved, in detail with an inherent immanent improved target accuracy and the possibility of guaranteeing the extinguishing personnel required for air operations a maximum security standard.

This object is achieved by the method according to the invention in that the extinguishing water is introduced into the source of the fire by means of aircraft, preferably helicopters, by passing it just above the source of the fire Blasting into a cloud-like mist from microscopic droplets being atomized. This method is preferably practiced in such a way that a container filled with the extinguishing water with a burstable wall, in which an explosive charge with a detonator is arranged inside the extinguishing water, is blown up just above the source of the fire. The container is preferably a teardrop-shaped or bubble-shaped sack made of plastic, which is also referred to below as an “explosive sack”.

The explosive bag can be brought to the site of the explosion just above the source of the fire by means of the helicopter hanging from a long tether and then detonated. However, it is exposed to the heat of the fire for a relatively long time, with the risk that it can be damaged and lose water even before the ignition. Fundamental safety regulations can also conflict with the detonation of a load hanging on the helicopter. It is therefore advisable to uncouple the explosive bag hanging from the helicopter with the tether on the helicopter in a safe position far above the source of the fire, to let it fall towards the source of the fire in free fall and then to ignite just above the source of the fire.

The invention places airborne fire fighting on a completely new basis. In contrast to all known methods in which the extinguishing water is ultimately introduced "as a mass" into the source of the fire, in the invention the extinguishing water is introduced in finely divided form. By igniting the explosive charge, high pressures (e.g. of several thousand bars) are created within the homogeneous medium of water in the explosive sack, through which the explosive sack bursts and the water bursts into the surroundings in microscopic droplets at high initial speeds (e.g. of over 5000 m / sl) is thrown. These droplets are slowed down after a short time by dissipation of the pressure wave formed during the explosion, by the air resistance and possibly by the impact on obstacles located in the vicinity of the detonation site, so that a completely fogged extinguishing area is formed, in the center of which the explosive bag was. Because of the enormously large number of smallest water droplets and the associated enormously large total surface area of these droplets in the immediate vicinity of the burning substances, there is an immediate heat transfer between the evaporating water droplets and the fire, which takes place within a few fractions of a second instead of. Heating the water Drops on their boiling temperature, the boiling process that consumes high heat of evaporation and the further heating of the water vapor produced draw such high amounts of energy from the burning environment that the temperature drops suddenly by several hundred degrees. In addition, a considerable proportion of the atmospheric oxygen initially still present in the detonation environment is displaced from the extinguishing area by the amounts of water vapor that arise.

The resulting lack of oxygen in the extinguishing cloud has a suffocating effect on the fire. Since the temperature in the area of the suddenly nebulized fire is simultaneously forced to a comparatively low value, the formation of flammable vapors, for example from essential oils, resins or other outgassing of the wood, is brought to a standstill and the ignition temperature is reduced to ( Backfiring of these vapors or combustible organic materials (wood) falls below. Together, this leads to a spontaneous extinguishing success, which enables ground-based extinguishing personnel to enter the extinguished source of fire and carry out post-extinguishing work, for example to knock out remaining fire nests with fire slips.

In order to illustrate the excellent extinguishing efficiency of the method according to the invention, the following calculation example is given:

If one assumes the use of a 1000 1 water-containing explosive bag and doses the explosive charge in such a way that a water cloud with a radius between 20 and 30 m forms in the center of the bag after detonation, this cloud has a volume of 33,500 to approx. 113,000 m ³ . The heat of evaporation of water is 539 kcal / kg, for 1000 l of water this results in a heat of evaporation of about 2,256,000 KW / s. To extinguish a 100 m long, 6 m wide and 6 m high burning log forest, a sudden withdrawal of a heat quantity of 100 KW / s was calculated. This corresponds to approximately 0.17 KJ / m ² . A water cloud of 30 m radius wets a floor area of approximately 2,800 m ² , which corresponds to an average heat of evaporation of approximately 789 KJ / m ² required for the evaporation of the water. It can therefore be assumed that there is a disproportionately large excess of heat that can be absorbed by the finely atomized water, which leads to a sudden extinction of almost 3000 m ^{2 of} burning forest, if one also considers that heat is also required to heat the water to boiling temperature. Such a large extinguishing efficiency is not yet known. There is no risk of danger to people and material if the method according to the invention is handled appropriately. 3 kg of a highly explosive and high-dose explosive are required to atomize the quantity of 1000 l of water assumed in the calculation example, "explosive" generally being understood to mean an explosive charge which generates a detonation wave with a propagation speed of over 5000 meters per second, and A "high-dose" explosive charge is present when more than two kilograms of explosives are used per 1000 liters of water. The detonation pressure of such an explosive charge dissipates so strongly that it is only about 0.063 kp / cm ^{2 at a} distance of 30 m from the detonation site. A risk to the helicopter and its crew can thus be excluded. To illustrate this low detonation pressure, it should be mentioned that a person standing upright at a distance of 10 m from the detonation site only feels a strong rain gust and is not thrown to the ground or even injured.

A highly explosive, modern explosive is preferably used for the explosive charge, which is water-resistant, can be stored almost indefinitely and is hardly combustible. The latter property is important for use in the immediate vicinity of the fire. Such modern explosives also tolerate strong mechanical influences and are therefore insensitive to knocks and bumps even in rough operation. In addition, they have good handling safety so that the risk of accidents due to unintentional, early ignition can almost be excluded. In an experiment, an explosive sack filled with 1000 l of water and provided with 3 kg of such a highly explosive explosive charge was dropped from a height of 150 m from a helicopter without prior activation of the detonator, without the explosive detonating on impact. A danger to extinguishing personnel and the environment is thus avoided with such an unwanted, early release of the explosive bag.

The enormously high extinguishing efficiency, the execution of the extinguishing action provided with a high security standard for people and material, as well as the possibility of using the extinguishing medium in a very precise manner are not the only advantages that the method according to the invention offers.

The use of the method according to the invention in combating forest and wildfires is ecologically harmless. The extinguishing insert leaves hardly any traces, on the other hand, due to the high extinguishing efficiency, the destruction of biological substance that is completely avoidable in no forest or wildfire is reduced to a minimum. There is no additional impairment of the eco-system, such as, for example, due to soil damage when using ground explosive devices.

The shortage of water that often occurs on site and the often inaccessible location of the fire, combined with the lack of infrastructure in forest areas, is optimally counteracted with the method according to the invention. Because of the great mobility and speed of the helicopters used, the uptake of the water-filled detonating bags can considerable distance from the location of the fire, at locations containing natural water or at locations which are easily accessible for fire engines. In addition, the previously required filling times of helicopter tanks with water are eliminated, with the helicopter previously only having to be forced to land. In the method according to the invention, it is sufficient if the helicopter flies down to a sufficient height in order to be able to hang the explosive bag on the helicopter. The equipment of the explosive bags with extinguishing water, explosive charge, detonator and tether, as well as the setting of the detonator can be made in the absence of the helicopter "in stock" and at a safe distance from the fire site, so that, on the one hand, the time for an operation on the pure flight ¬ time and the very short loading time is limited, on the other hand maximum safety is guaranteed for the firefighters working on the ground.

The quick, problem-free loading of the helicopter with an explosive bag has a particularly advantageous effect in forest fires, for which a relatively narrow fire front that extends over longer lengths is typical. This is because even a single helicopter can effectively extinguish sections of the fire front lengthways in short intervals. Of course, it is even faster if two or more helicopters extinguish in sections in the rolling, i.e. get consecutive use. Alternatively, two or more helicopters at a distance of an effective range can simultaneously release their detonation load and detonate them, preferably coordinated by radio, whereby an effective range is understood to mean the mean diameter of the extinguishing cloud which arises during the detonation.

The application of the method according to the invention is not only limited on forest and wildfires, but can take place with all imaginable, combatable fires. Because of the very high extinguishing efficiency and the high safety standard of the method, use is particularly advantageous in the case of very dangerous and difficult to extinguish fires. These can be, for example, fires from fuel tanks, oil tower fires or fires which occur in the case of aircraft crashes, without wishing to restrict the application of the invention to these cases. It is advisable to use a water volume of 500 liters (bush fire, buildings, warehouses), 1000 liters (forest fires) or 2000 liters (tank, refinery, oil rig fires) for the respective fire fighting operation.

The water used for extinguishing does not have to be pure water, but can also contain retarders. These are chemical substances that inhibit or at least delay the ignition of flammable solid materials and that are blown into the fire material together with the water when the fire-fighting bag is detonated. A later re-ignition of the suddenly extinguished fire material by possibly still existing embers nests is at least less likely in the presence of a retarder. Different types of retarders are known and work in different ways depending on their composition. Retarders based on salt form a crust on the fire material which on the one hand inhibits its outgassing and on the other hand prevents the oxygen in the ambient air from accessing the fire material. Other retarders, like a gelling agent, absorb large amounts of water and store it. A fire that is finely covered with such water reservoirs "runs dead". However, especially in the case of forest fires, such retarders are normally not required and, because of the soil pollution that is inevitably associated with them, are also not recommended. With other fires, however, they can have a positive effect.

The invention is explained in more detail in exemplary embodiments with reference to the drawings. Show

1 schematically shows an explosive sack hanging from a helicopter, FIG. 2 shows schematically the dropping of the explosive sack onto a source of fire, FIG. 3 shows schematically the triggering of a fire cloud, and FIG. 4 shows an example of an ignition device. 1-3, the sequence of an extinguishing attack on the flame front of a forest fire is illustrated schematically. A water-filled drop-shaped explosive bag 1 is attached to the load hook 7 of a helicopter 10 (FIG. 1) by means of a tether 4 made of plastic (eg Nylon) or steel, the length of which can be 3 - 50 m. The explosive bag has a capacity of around 1000 liters of water and consists of thin-walled plastic (for example polypropylene), the wall thickness of which is sufficient to carry the water, but is low enough to burst when blown up.

Within the water 3 in the detonating bag, and preferably in the middle, there is an explosive charge 2 provided with a delay detonator, which is appropriately shaped like a teardrop or bubble in accordance with the detonating bag and is held in position by a short rope 5. The lower side of the explosive bag facing the fire can be coated with a heat protection layer 8, e.g. be provided with an aluminum foil which is intended to prevent the explosive bag from being destroyed locally by the fire in the event of excessive heat and the extinguishing water being largely lost to the action of the subsequent detonation.

The tether 4 can be designed differently such that it is either dropped together with the detonating bag 1 or remains on the helicopter. In the example of FIGS. 1 and 2 it is assumed that the tether is released from the load hook 7 and dropped together with the detonating bag. In this case, it should be provided with a spliced claw at the upper end located on the load hook in order to prevent twisting of the tether under load on the load hook of the helicopter, since this could possibly prevent the hook from being thrown off. Under no circumstances should the shackle itself be used to take up the load, since the relatively heavy shackle overtakes the detonating bag in free fall after detaching it from the hook, thus causing the latter to rotate undesirably by 180 ^* . For even better stabilization during the fall, it is advisable to fix one or two small brake parachutes 6 to the tether immediately below the upper end (FIG. 2), which are dimensioned such that they do not brake the falling movement of the explosive bag, but only the tether prevent the explosive bag from destabilizing in position while falling.

Alternatively, the tether 4 can also be - 9 - nem (only schematically indicated) remote-controlled load hook 18, which allows the detonating bag from the helicopter to be detached from the tether and thrown off by itself. As a result, the tether remains on the helicopter and is available for renewed use. Load hooks controlled remotely from the helicopter are known and are used, for example, in forestry for game feeding.

When the helicopter reaches the scene of the fire and has placed the explosive bag at a predetermined height above the source of the fire, the explosive bag (with or without a rope) is dropped and moves in free fall towards the source of the fire (Fig. 2). As soon as he has reached a height just above the source of the fire (e.g. a few meters above the tree top), the blasting is triggered. This can be done by remote ignition, which is triggered by the load helicopter 10 or a special fire helicopter or a ground-based observation station by radio signal. Since remote ignition requires high concentration and responsiveness of the operator in view of the high falling speed of the detonating bag, it is generally more expedient to cause the detonating charge in the detonating bag to be ignited by means of a delay detonator which is activated simultaneously with the dropping off of the detonating bag and one predetermined time after the drop, when the explosive bag is at the desired height above the source of the fire, the explosive charge ignites.

Delay igniters with double security are preferably used here in order to comply with the aviation safety regulations. These U-detonators, which are manufactured today by factory technology, have tolerances of only a few milliseconds, so that the required discharge height for the explosive charge can be calculated very precisely and maximum security is provided for the air operations personnel. For example, a detonator has proven to be very suitable, which can be set in up to 18 intervals of 250 milliseconds each, so that fall times until detonation after activation of the detonator are specified from 0.25 to 4.5 seconds can, which, if the air resistance is neglected, corresponds to a drop height of half a meter to almost one hundred meters. The height of the helicopter above the detonation site at the moment the explosive bag is dropped is made up of this drop distance plus the length of the tether. 4 shows an example of a triggering of the delay fuse which is particularly acceptable in terms of safety. From the delay fuse, a two-wire ignition cable 11 is guided out of the explosive bag 1 along the tether 4 to the bottom of the helicopter 10. The ignition cable is connected there via a plug connection 12, for example consisting of a flat plug (at the end of the ignition cable) and a flat socket (firmly fixed to the bottom of the helicopter), with a DC voltage source 17 located in the helicopter and serving as an ignition source. A toggle switch 13 is arranged in the line between the flat socket and the ignition source. After a relatively short distance, the ignition cable is provided with a further switch 16 slightly below the flat plug, which contains two contact springs which are separated from one another by a plastic flat wedge and come into contact with one another by removing the plastic flat wedge. The plastic flat wedge, which is hooked into the load hook 7 or another hook on the helicopter by means of a short pull cable 14, is inserted into the switch 16 and thus interrupts the electrical connection of the delay fuse with the ignition source. The ignition cable is fastened to the tether 4 with a clamp 15 just below the switch 16. During the approach of the helicopter from the receiving point for the extinguishing sack to the discharge point, the connection between the ignition source 17 and the plug connection 12 is also interrupted by the toggle switch 13 in order to prevent the detonator from accidentally slipping out of the plastic surface wedge from switch 16 is activated early.

If the helicopter is at the location provided for the drop in the height corresponding to the length of the tether, the duration of the delay for the detonator and the desired detonation height above ground, the plug connection 12 is first energized by actuating the toggle switch 13. Then the tether 4 is released on the load hook 7 of the helicopter. Because of the fixing of the ignition cable to the tether by means of the clamp 15, the plastic flat wedge, which is held back by its connection to the helicopter, is first pulled out of the switch 16 by the falling movement. This establishes the electrical contact between the ignition source and the delay fuse, and the fuse is activated. A short time later, due to the continuous falling movement, the flat plug is pulled out of the flat socket, so that the so-called in-cockpit component, consisting of the ignition source, toggle switch, line and flat socket, is not mechanically stressed by the release and immediately for the next extinguishing operation again is available. It is only important to ensure that the pull cable 14 for fastening the plastic flat wedge is chosen to be so short that the plug contact is only released after the wedge has been pulled out of the contact terminal. Otherwise there would be no electrical activation of the detonator and thus the desired detonation of the detonating bag.

As already described, the detonation of the explosive charge in the detonating bag creates a mist, also known as an extinguishing cloud, from finely divided water droplets. This quenching cloud spreads essentially spherically. A movement of water droplets away from the source of the fire is generally not desired, and an essentially hemispherical extinguishing cloud, in which all water droplets are directed downwards towards the source of the fire and its surroundings, is much more effective. Such an essentially hemispherical extinguishing cloud is illustrated schematically in FIG. 3, it can be achieved by extinguishing the extinguishing water 3 inside the explosive bag 1 with a thin film 9 made of plastic, paper or the like. is covered (Fig. 1). This film can be placed loosely on the extinguishing water, but it can also be attached point by point to the explosive bag in such a way that sufficient opening remains in the explosive bag for filling the extinguishing water.

Claims

Expectations

1.) Process for fighting fire from the air, by putting extinguishing water by means of aircraft, preferably helicopters, into the source of the fire, characterized in that the extinguishing water is atomized shortly above the source of the fire by blowing up to form a cloud-like mist of microscopic droplets.

2.) Method according to claim 1, characterized in that a container filled with the extinguishing water with burstable wall, in which an explosive charge with detonator is arranged within the extinguishing water, is blown up just above the source of the fire.

3.) Method according to claim 2, characterized in that a highly explosive explosive is chosen as the explosive charge in a quantity which is sufficient to give the water droplets an initial speed of at least 5,000 m / s.

4.) Method according to claim 2 or 3, characterized in that the container is dropped from a helicopter above the source of the fire and that the explosive charge is detonated just above the source of the fire during free fall.

5.) Method according to claim 4, characterized in that two or more helicopters at the same time throw off a container and detonate it at a distance of one effective width of the extinguishing cloud, preferably coordinated by radio.

6.) Device for carrying out the method according to one of claims 1 to 5, characterized by an explosive bag (1) made of thin-walled plastic in the form of a bubble or a drop for receiving the extinguishing water (3) and one approximately in the middle of the Extinguishing water held, also bubble or drop-shaped explosive charge (2) with detonator, the detonating bag can be detachably attached to a helicopter (10) by means of a tether (4).

7.) Device according to claim 6, characterized in that a reflective heat protection layer (12) is attached to the lower, fire-prone side of the explosive bag (1).

8.) Device according to claim 6 or 7, characterized in that the extinguishing water (3) within the explosive bag (1) is covered with a thin film (9).

9.) Device according to one of claims 6 to 8, characterized gekennzeich¬ net that the detonator of the explosive charge (2) is an adjustable to a predetermined drop height delay detonator, which is detachable from the helicopter ignition cable (11) with an ignition source ( 17) connected in the helicopter and can be activated simultaneously with the dropping of the explosive bag (1).

10.) Method according to one of claims 6 to 9, characterized gekennzeich¬ net that near the upper end of the tether (4) at least one small Brems¬ parachute (6) is attached to the tether, which prevents the tether during the fall phase, to overtake the explosive bag.