Helicopter fire attack system

Abstract

There are provided helicopter attack systems. These systems can comprise an adjustable and / or controllable tank. In fact, the volume of the tank can be adjusted since it comprises an expandable skirt and an actuator for increasing or decreasing the distance between a bottom shell and an upper shell of the tank, thereby increasing or decreasing the tank capacity or internal volume.

Description

HELICOPTER FIRE ATTACK SYSTEMCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] The present application claims the benefit of priority of co-pending U.S. Provisional Patent Application No. 63 / 626,665, which was filed January 30, 2024, the content of which is incorporated herein by reference in its entirety.FIELD OF THE DISCLOSURE

[0002] The disclosure relates to the field of helicopter systems used for extinguishing a fire. More particularly, the disclosure relates to helicopter fire attack systems.BACKGROUND OF THE DISCLOSURE

[0003] There has been a surge in wildfires in recent years, and these cause each year billions of dollars’ worth of damage worldwide. These types of fires are often located in remote forested area and use the natural vegetation of the area as combustible. As such, wildfires are typically not easily accessible by land such that aircrafts are often required to fight them. Moreover, most wildfires usually attack large areas and make their suppression and / or control a challenge.

[0004] Both fixed-wing and rotary aircraft have been used for the purpose of wildfires firefighting and are configured to receive and drop a quantity of water. Helicopters provide greater maneuverability compared to fixed-wing. A liquid, such as water or any fire-retardant material, or combination thereof, is typically transported to a fire site by the aircraft, typically via a bucket, or airframe-mounted water tank. In the case of a tank, the liquid is typically onloaded through a semi rigid snorkel pump that extends below the aircraft is lowered from the helicopter into the liquid source, such as a body of water. When not in use, the snorkel pump is attached to the fuselage, which presents some issues with respect to the aerodynamics and handling of the helicopter.

[0005] An alternate type of the snorkel pump is a Retractable Snorkel Pump (RSP). This snorkel pump system consists of a soft hose material that can be deployed for fill operations and retracted for quicker response times to and from the fire. The retracted snorkel pump allows for increased flight speeds.

[0006] Known devices in the art include for example the Helitak systems (see FIG. 1 and FIG.2), the recoil system (see FIG.3), and the Timberline system and(see FIG.4). These systems present the disadvantages of not having any ability for ground fill operations, in part because the collapsed tanks fill the internal area.Moreover, these setups present poor water drop performance / drop pattern as shown specifically in FIG.5, where water may spill over the doors (outboard). In addition, these systems do not offer a Retractable Snorkel Pump option (RSP).Alternate approach was developed by the Applicant, as shown in FIG.6, providing a wide and thin tank, not expandable. However, this design requires the removal of the cabin access footsteps to achieve the 4000L tank volume. This tank encroaches into these steps requiring them to be removed. The tank also requires built in step accommodations. Further, the rescue hoist cannot be used when the tank is installed. The design also presented poor tank evacuations / drop performance, was difficult to manufacture and heavy (1300lbs+) since thinner, wider tanks require more support baffling and an additional keel and were difficult to install.

[0007] Accordingly, there is a need to develop improved firefighting systems that would at least overcome some of the above drawbacks.SUMMARY OF THE DISCLOSURE

[0008] It has been shown herein that the present application provides a tank configured to be connected to a helicopter, said tank comprising an actuator for controlling a capacity of said tank, wherein said actuator is disposed inside said tank.

[0009] There is provided a tank configured to be connected to a helicopter, said tank comprising an actuator for controlling a capacity of said tank and an expandable skirt.

[0010] Accordingly, the present application provides an expandable tank comprising: an upper shell; a bottom shell configured to be movable between a fully expanded position and a collapsed position; a sidewall connected to the upper and lower shells, defining a tank space therebetween configured for retaining a liquid, wherein the sidewall is expandable between the fully expanded position and the collapsed position; and at least one actuator connected to the upper shell and to the bottom shell, and configured to move the bottom shell at any position between the fully expanded position and the collapsed position such as to control a volume of the tank space, wherein the at least one actuator is disposed at least partially inside thetank space; wherein the expandable tank is configured to be mounted to a helicopter.

[0011] Also included is use of an expandable tank of the present application for firefighting applications. Further included is use of an expandable tank of the present application wherein the helicopter is landed on the ground for filing with the liquid.

[0012] The present application further includes use of at least one actuator for adjusting a volume of a tank space in an expandable tank, wherein said at least one actuator is disposed inside said tank.

[0013] The present application also provides a method for controlling a volume of an expandable tank mounted on a helicopter, comprising adjusting a bottom shell of the expandable tank with at least one actuator, wherein said at least one actuator is at least partially disposed inside said expandable tank.

[0014] Also included is a method for firefighting using an expandable tank of the present application, the method comprising: controlling the volume of the expandable tank space by actuating the at least one actuator to select a predetermined volume; filing the tank space with the liquid; and discharging the liquid at the predetermined fire location for firefighting.

[0015] The present application further provides a method for filing a bellymounted helicopter firefighting expandable tank, the method comprising: selecting a predetermined volume of the expandable tank, controlling the volume of the expandable tank to the predetermined volume; filing the expandable tank with a liquid while the helicopter is on the ground.

[0016] Further provided is a method for firefighting with a belly-mounted helicopter firefighting expandable tank, the method comprising: filing the expandable tank with a liquid when the helicopter is on the ground; taking off to a predetermined fire location; and discharging the liquid at the predetermined fire location for firefighting.

[0017] Other features and advantages of the present application will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating embodiments of the application, are given by way of illustration only and the scope ofthe claims should not be limited by these embodiments, but should be given the broadest interpretation consistent with the description as a whole.BRIEF DESCRIPTION OF DRAWINGS

[0018] The embodiments of the application will now be described in greater detail with reference to the attached drawings in which:

[0019] FIG.1 shows helicopter firefighting systems of the prior art.

[0020] FIG.2 shows a helicopter firefighting system of the prior art, in dropping mode.

[0021] FIG.3 shows a helicopter firefighting system of the prior art, in dropping mode.

[0022] FIG.4 shows a helicopter firefighting system of the prior art.

[0023] FIG.5 shows helicopter firefighting systems of the prior art, in dropping mode.

[0024] FIG.6 shows a helicopter firefighting system of the prior art.

[0025] FIG.7 shows a helicopter firefighting system mounted on the helicopter, according to exemplary embodiments of the application.

[0026] FIG.8 shows a side view of an expandable tank according to exemplary embodiments of the application.

[0027] FIG.9A shows a perspective view of an expandable tank according to exemplary embodiments of the application, and FIG.9B shows a side view of an expandable tank in collapsed position (top) and in an expanded position (bottom).

[0028] FIG.10 shows a partial side view of an expandable tank according to exemplary embodiments of the application, showing an actuator within the tank space and an enlarged view thereof.

[0029] FIG.11 shows views of an actuator according to exemplary embodiments of the application.

[0030] FIG.12 shows a truncated view of an actuator according to exemplary embodiments of the application.

[0031] FIG.13 shows a top perspective view of an expandable tank connected to a filling device, according to exemplary embodiments of the application.

[0032] FIG.14 shows a top perspective view of an expandable tank with transparency of the upper shell to show internal parts, according to exemplary embodiments of the application.

[0033] FIG.15 shows a top perspective view of an expandable tank with sidewall position control assembly, according to exemplary embodiments of the application.

[0034] FIG.16 shows a sidewall position control assembly, according to exemplary embodiments of the application.

[0035] FIG.17 shows a sidewall position control assembly, according to exemplary embodiments of the application.

[0036] FIG.18 shows a sidewall configuration, according to exemplary embodiments of the application.

[0037] FIG.19 shows a sidewall configuration, according to exemplary embodiments of the application.

[0038] FIG.20 shows a stabilization mechanism on the expandable tank, according to exemplary embodiments of the application.

[0039] FIG.21 shows a stabilization mechanism, according to exemplary embodiments of the application.

[0040] FIG .22 shows a helicopter firefighting system mounted on the helicopter, according to exemplary embodiments of the application.DETAILED DESCRIPTION OF THE DISCLOSUREI. Definitions

[0041] Unless otherwise indicated, the definitions and embodiments described in this and other sections are intended to be applicable to all embodiments and aspects of the present application herein described for which they are suitable as would be understood by a person skilled in the art.

[0042] As used in this application and claim(s), the words "comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "includes") or "containing" (and any form of containing, such as "contain" and "contains"), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0043] The term “consisting” and its derivatives as used herein are intended to be closed terms that specify the presence of the stated features, elements, components, groups, integers, and / or steps, and also exclude the presence of other unstated features, elements, components, groups, integers and / or steps.

[0044] The term “consisting essentially of”, as used herein, is intended to specify the presence of the stated features, elements, components, groups, integers, and / or steps as well as those that do not materially affect the basic and novel characteristic(s) of these features, elements, components, groups, integers, and / or steps.

[0045] The terms "about", “substantially” and “approximately” as used herein mean a reasonable amount of deviation of the modified term such that the end result is not significantly changed. These terms of degree should be construed as including a deviation of at least ±5% of the modified term if this deviation would not negate the meaning of the word it modifies or unless the context suggests otherwise to a person skilled in the art.

[0046] As used in the present application, the singular forms “a”, “an” and “the” include plural references unless the content clearly dictates otherwise. For example, an embodiment including “a component” should be understood to present certain aspects with one component, or two or more additional components.

[0047] In embodiments comprising an “additional” or “second” component, such as an additional or second components, the second component as used herein is different from the other components or first component. A “third” component is different from the other, first, and second components, and further enumerated or “additional” components are similarly different.

[0048] The term “and / or” as used herein means that the listed items are present, or used, individually or in combination. In effect, this term means that “at least one of” or “one or more” of the listed items is used or present.

[0049] The term “suitable” as used herein means that the selection of the particular components or conditions would depend on the specific steps to be performed, the identity of the components to be used and / or the specific use for the components, but the selection would be well within the skill of a person trained in the art.II. Systems of the Application

[0050] In light of the recurring low ground clearance challenges experienced in previous projects, and subsequent scrutiny of existing expandable tanks within the market, controlled expandable tank of the application was developed. Without being bound to theory, it is submitted that the expandable tank systems of the application may provide: minimal expansion allowing for potentially greater speeds during drop, ground fill capabilities, a customizable maximum fill volume for greater safety, reduced potential for overfill during different operational situations, Retractable Snorkel Pump (RSP) option allowing for potentially quicker mission turn times, superior drop pattern.

[0051] Accordingly, the present application includes an expandable tank comprising: an upper shell; a bottom shell configured to be movable between a fully expanded position and a collapsed position, a sidewall connected to the upper shell and to the bottom shell, defining a tank space therebetween configured for retaining a liquid, wherein the sidewall is expandable between the fully expanded position and the collapsed position, at least one actuator connected to the upper shell and to the bottom shell, and configured to move the bottom shell at any position between the fully expanded position and the collapsed position such as to control a volume of the tank space, wherein the at least one actuator is disposed at least partially inside the tank space, wherein the expandable tank is configured to be mounted to a helicopter.

[0052] In some embodiments, the at least one actuator connected to the upper shell and to the bottom shell refers to the actuator being fixed to or mounted on the upper shell and the bottom shell. In some embodiments, the actuator disposed at least partially inside the tank space refers to at least 50% of the length of the actuator, or at least 75%. In some embodiments, the actuator comprises a piston, an electrical drive unit and a rotational drive mechanism and at least the piston portion is inside the tank space. In some embodiments, the piston and the electrical drive unit are inside the tank space. In some embodiments, the rotational drive mechanism protrudes or is at the surface of the upper shell.

[0053] In some embodiments, the at least one actuator is configured to move the bottom shell to at least one partially expanded position. In some embodiments, inthe at least one partially expanded position, the bottom shell is in contact with the ground when the helicopter is landed. In some embodiments, in the at least one partially expanded position, the bottom shell is just above the ground when the helicopter is landed. Without wishing to be bound to theory, the configuration of the expandable tank of the application allows for the ground fill capabilities, a customizable maximum fill volume for greater safety and reduced potential for overfill.

[0054] In some embodiments, in the at least one partially expanded position, the expandable tank is configured to receive the liquid when the helicopter is landed.

[0055] In some embodiments, the upper shell is configured to be connected to the fuselage of the helicopter. In some embodiments, the expandable tank is configured to be connected to the fuselage of the helicopter such that the bottom shell is above a landing gear. In some embodiments, the expandable tank configured to be connected to the fuselage refers to fixed on or mounted on the fuselage.

[0056] In some embodiments, the upper shell and the bottom shell each comprises a composite material shell, metallic structural elements, and metallic attachments points. The metallic structural elements may serve to provide a higher level of solidity, rigidity, durability or the like, to the upper shell and bottom shell, and the metallic attachments points may serve as hardpoints for attachments / connections to other components. In some embodiments, the composite material is carbon fiber.

[0057] In some embodiments, the bottom shell comprises at least one discharge door configured to discharge, upon opening, the liquid to be retained in the tank space.

[0058] In some embodiments, the sidewall is connected to the upper shell and to the bottom shell, refers to the sidewall being fixed to or mounted on the upper shell and the bottom shell. In some embodiments, the sidewall is a flexible skirt (soft skirt), a telescopic sidewall, or a membrane. In some embodiments, the sidewall is made of a polymeric membrane. In some embodiments, the tank further comprises a sidewall position control assembly connected to the sidewall configured to guide the sidewall within the tank space when moving to the collapsed position. Without being bound to theory, such an assembly will assist in minimizing external exposure of thesidewall, for example, avoiding the sidewall flapping out when the helicopter is flying, exposure to harsh weather and the like, etc.

[0059] In some embodiments, the upper shell comprising at least one filling port for providing the liquid within the tank space when the helicopter is landed. For example, the upper shell may be provided with a water filling port, a foam filling port, etc.

[0060] In some embodiments, the expandable tank is configured to be coupled with a filling device for providing the liquid within the tank space. In some embodiments, the filling device comprises a pump. In some embodiments, the pump is provided with a connector for fitting with a complementary connector of a filling pipe, such as a retractable snorkel. In some embodiments, the retractable snorkel is configured to extend below the helicopter such that it may extract water from a body of water upon flying over.

[0061] In some embodiments, the at least one actuator is a gas-spring right angle actuator, a vertical actuator or an angled actuator. In some embodiments, the expandable tank comprises at least two actuators. In some embodiments, the expandable tank comprises at least four actuators. It will be appreciated that the number of actuators may vary depending on the size of the tank, the weight of the bottom shell, the size and power of each actuator. The selection of an appropriate number of actuators will be within the purview of a skilled person in the art.

[0062] In some embodiments, the expandable tank further comprises a controller for controlling the at least one actuator. In some embodiments, the controller reverts the bottom shell to the collapsed position upon discharge of the liquid. In some embodiments, the controller is manually or automatically controlled.

[0063] In some embodiments, the volume of the tank space is adjustable to set a maximum volume. In some embodiments, the volume of the tank space is set by the at least one actuator such that it is independent on the liquid loading weight. In some embodiments, the at least one actuator is inoperative when liquid is present within the tank space.

[0064] In some embodiments, the expandable tank further comprises a stabilization mechanism connected to the bottom shell and the upper shell configured to provide stability upon moving the bottom shell between the fullyexpanded position and the collapsed position. In some embodiments, the stabilization mechanism is a scissor-like extendable assembly.

[0065] In some embodiments, the liquid is water, a flame retardant chemical, or a combination thereof.

[0066] In some embodiments, the tank will be equipped with four right-angle actuators designed to regulate the maximum volume levels of the tank. Notably, the design negates the necessity for the actuators to function under the influence of any loading from the weight of water; their sole purpose is to adjust the lower section of the tank to establish the maximum water fill volume. Upon water evacuation from the tank, the lower portion can automatically revert to its fully collapsed position. The stop limit set by the actuators will remain in place unless a modification is initiated for the maximum volume via the controller. In some embodiments, adjustments to the tank volume will be precluded when water is present in the tank.

[0067] In some embodiments, the rotary actuator is enclosed in a waterproof enclosure, Line Replaceable Unit (LRU jcompatible, and made of all aluminum / SS construction. Without being bound to theory, the LRU allows an operator easy maintenance and replacement of a faulty actuator, without the need for the intervention of the manufactureur. For example, the actuator may be a stepper motor produced by Nanotec-Unit, but one skilled in the art will appreciate that other suitable actuators may be used.III. Uses and Methods of the Application

[0068] The expandable tank of the present application are configured for use on a helicopter chosen from Airbus Super Puma models AS332L, AS332L1 , AS332L2, and EC225LP aircraft The present applicant includes use of an expandable tank for firefighting applications.

[0069] The present application further includes use of at least one actuator for adjusting a volume of a tank space in an expandable tank, wherein said at least one actuator is disposed inside said tank.

[0070] Also provided is use of an expandable tank of the present application, wherein the helicopter is landed on the ground for filing with the liquid.

[0071] The present application also includes a method for controlling a volume of an expandable tank mounted on a helicopter, comprising adjusting a bottom shellof the expandable tank with at least one actuator, wherein said at least one actuator is disposed inside said expandable tank.

[0072] Further included is a method for firefighting using an expandable tank of the present application, the method comprising: controlling the volume of the expandable tank space by actuating the at least one actuator to select a predetermined volume; filing the tank space with the liquid; and discharging the liquid at the predetermined fire location for firefighting.

[0073] The present application also includes a method for filing a belly-mounted helicopter firefighting expandable tank, the method comprising: selecting a predetermined volume of the expandable tank, controlling the volume of the expandable tank to the predetermined volume; filing the expandable tank with a liquid while the helicopter is on the ground.

[0074] In some embodiments, controlling the volume of the expandable tank comprises adjusting a bottom shell between at any position at any position between a fully expanded position and a collapsed position, optionally at a partially expanded position when the helicopter is on the ground.

[0075] In some embodiments, controlling the volume of the expandable tank comprises adjusting a bottom shell between at any position at any position between a fully expanded position and a collapsed position with at least one actuator disposed inside the expandable tank.

[0076] In some embodiments, controlling the volume of the expandable tank comprises adjusting a bottom shell between at any position at any position between a fully expanded position and a collapsed position with at least one actuator disposed inside the expandable tank, wherein at a partially expanded position when the helicopter is on the ground.

[0077] The present application further provides a method for firefighting using an expandable tank, the method comprising: filing the expandable tank with a liquid when a helicopter is on the ground;taking off to a predetermined fire location; and discharging the liquid at the predetermined fire location for firefighting.EXAMPLES

[0078] The following non-limiting examples are illustrative of the present application and described in greater detail with reference to the attached drawings.

[0079] With reference to FIG.7, an exemplary expandable tank 10 of the application is shown, mounted to a helicopter 20, in a collapsed position. Bottom shell 30 is shown, comprising discharge doors 40, 40’. Also shown is a filling device 50, where filing pipe or snorkel 60 is retracted.

[0080] Turning to FIG.8, a side view of expandable tank 10 is shown without sidewall to show tank space 70, between the bottom shell 30 and upper shell 80. Two actuators, 90, 90A can also be seen therebetween within tank space 70. A connecting portion 100 of filling device 50 is also shown. FIG.9A is a top perspective view of expandable tank 10 showing upper shell 80. Also seen is the connecting portion 100, and upper portions of four actuators 90, 90A, 90B, 90C connected to the upper shell 80. With reference to FIG.9B, the exemplary expandable tank 10 is shown in a collapsed position (top) and an expanded position (bottom).

[0081] In FIG.10, one actuator 90 can be seen within tank space 70, between bottom shell 30 and upper shell 80 and an enlarged view of an exemplary actuator is shown (right). The sidewall 1 10 is also shown on this figure of exemplary expandable tank 10 in an expended position. Exemplary actuator 90 is further shown in FIG.11 where a gas-spring piston 120 can be seen from a perspective view (left) and a side view (middle). Actuator 90 is configured to connected to the upper shell 80 through its upper portion 130 and operatively connected to the bottom shell 30 through its lower portion 140.

[0082] FIG.12 also shows a truncated view of an exemplary actuator 90 of the application. It can be appreciated that actuator 90 is partially within the tank space 70 between the waterline A and bottom shell line B. Specifically, piston 120 and electrical drive unit 132 are inside the tank space 70. In this embodiment, upper portion 130 enclosing rotational drive mechanism 134 is shown protruding from the upper shell. It will be appreciated that the rotational drive mechanism may optionally be enclosedwithin the upper shell in alternate embodiments (not shown) or electrical drive unit be protruding from the upper shell, as long as the piston is within tank space.

[0083] Turning to FIG.13, a perspective view of expandable tank 10 is shown in a collapsed position, showing upper shell 80, connecting portion 100 of filing device 50 (enclosing a pump not shown) with filing pipe or snorkel 60 extending out, upper portions of four actuators 90, 90A, 90B, 90C connected to the upper shell 80, and further showing stabilization mechanism 150 (shown further in FIG. 20 and FIG.21). FIG.13 also shows embodiments comprising a water ground fill port 52, a foam fill port 54, drop vents 65 FIG.14 shows a perspective view of the bottom shell 30 with lower portions of four actuators 90, 90A, 90B, 90C connected to the bottom shell, and controller board 160.

[0084] Sidewall 1 10 will now be shown in further detail in FIG.15-FIG.19. FIG.15 shows sidewall 1 10 between bottom shell 30 and upper shell 80. FIG.16 illustrates an exemplary sidewall position control assembly 170 and FIG.17 is a schematic representation thereof, where assembly 170 is configured to guide sidewall 110 within the tank space 70 when returned in the collapsed position, to minimize external exposure.

[0085] FIG.18 and FIG.19 shows alternate embodiments of configurations of sidewall 1 10, where the shape will vary in function of the shape of the bottom shell and upper shell.

[0086] FIG. 20 shows an exemplary stabilization mechanism 150 mounted on the side of expandable tank 10, connected to bottom shell 30 and upper shell 80 (left) and exemplary positions of four stabilization mechanisms 150 (right), shown as positions as #1 , #2, #3 and #4. Stabilization mechanism 150 is shown enlarged in FIG.21 with upper portion 152 to be mounted to upper shell and lower portion 154 to be mounted to the bottom shell, and intermediate scissor-like portion 156. Stabilization mechanism 150 may be used to increase stability of the tank assembly upon actuation between the fully expanded position and the collapsed position, and all positions therebetween.

[0087] Finally, FIG. 22 shows exemplary expandable tank 10 of the application, mounted to a helicopter 20, in a collapsed position with filing pipe or snorkel 60 extended ready for filling.

[0088] While the applicant's teachings described herein are in conjunction with various embodiments for illustrative purposes, it is not intended that the applicant's teachings be limited to such embodiments as the embodiments described herein are intended to be examples. On the contrary, the applicant's teachings described and illustrated herein encompass various alternatives, modifications, and equivalents, without departing from the embodiments described herein, the general scope of which is defined in the appended claims.

Claims

CLAIMS:1 . An expandable tank comprising: an upper shell; a bottom shell configured to be movable between a fully expanded position and a collapsed position, a sidewall connected to the upper shell and to the bottom shell, defining a tank space therebetween configured for retaining a liquid, wherein the sidewall is expandable between the fully expanded position and the collapsed position, at least one actuator connected to the upper shell and to the bottom shell, and configured to move the bottom shell at any position between the fully expanded position and the collapsed position such as to control a volume of the tank space, wherein the at least one actuator is disposed at least partially inside the tank space, wherein the expandable tank is configured to be mounted to a helicopter.

2. The expandable tank of claim 1 , wherein the at least one actuator is configured to move the bottom shell to at least one partially expanded position.

3. The expandable tank of claim 2, wherein in the at least one partially expanded position, the bottom shell is in contact with the ground when the helicopter is landed.

4. The expandable tank of claim 2, wherein in the at least one partially expanded position, the bottom shell is just above the ground when the helicopter is landed.

5. The expandable tank of any one of claims 2 to 4, wherein in the at least one partially expanded position, the expandable tank is configured to receive the liquid when the helicopter is landed.

6. The expandable tank of any one of claims 1 to 5, wherein the upper shell is configured to be connected to the fuselage of the helicopter.

7. The expandable tank of any one of claims 1 to 6, wherein the expandable tank is configured to be connected to the fuselage of the helicopter such that the bottom shell is above a landing gear.

8. The expandable tank of any one of claims 1 to 7, wherein the upper shell and the bottom shell each comprises a composite material shell, metallic structural elements, and metallic attachments points.

9. The expandable tank of claim 8, wherein the composite material is carbon fiber.

10. The expandable tank of any one of claims 1 to 9, wherein the bottom shell comprises at least one discharge door configured to discharge, upon opening, the liquid to be retained in the tank space.11 . The expandable tank of any one of claims 1 to 10, wherein the sidewall is a flexible skirt, a telescopic sidewall, or a membrane.

12. The expandable tank of any one of claims 1 to 1 1 , wherein the sidewall is made of a polymeric membrane.

13. The expandable tank of any one of claims 1 to 12, further comprising a sidewall position control assembly connected to the sidewall configured to guide the sidewall within the tank space when moving to the collapsed position14. The expandable tank any one of claims 1 to 13, wherein the upper shell comprising at least one filling port for providing the liquid within the tank space when the helicopter is landed.

15. The expandable tank any one of claims 1 to 14, wherein the expandable tank is configured to be coupled with a filling device for providing the liquid within the tank space.

16. The expandable tank of claim 15, wherein the filling device comprises a pump.

17. The expandable tank of claim 16, wherein the pump is provided with a connector for fitting with a complementary connector of a filling pipe.

18. The expandable tank of claim 17, wherein the filling pipe is a retractable snorkel configured for extracting water from a body of water.

19. The expandable tank of any one of claims 1 to 18, wherein the at least one actuator is a gas-spring right angle actuator, a vertical actuator or an angled actuator.

20. The expandable tank of any one of claims 1 to 19, comprising at least two actuators.21 . The expandable tank of any one of claims 1 to 19, comprising at least four actuators.

22. The expandable tank of any one of claims 1 to 19, wherein disposed at least partially inside the tank space comprises at least 50% of the length of the actuator.

23. The expandable tank of any one of claims 1 to 19, wherein disposed at least partially inside the tank space comprises at least 75% of the length of the actuator.

24. The expandable tank of any one of claims 1 to 23, wherein the actuator comprises a piston, an electrical drive unit and a rotational drive mechanism.

25. The expandable tank of claim 24, wherein at least the piston is inside the tank space.

26. The expandable tank of claim 24, wherein the piston and the electrical drive unit are inside the tank space.

27. The expandable tank of any one of claims 24 to 26, wherein the rotational drive mechanism protrudes or is at the surface of the upper shell.

28. The expandable tank of any one of claims 1 to 27, further comprising a controller for controlling the at least one actuator.

29. The expandable tank of claim 28, wherein the controller reverts the bottom shell to the collapsed position upon discharge of the liquid.

30. The expandable tank of claim 28 or 29, wherein the controller is manually or automatically controlled.31 . The expandable tank of any one of claims 1 to 30, wherein the volume of the tank space is adjustable to set a maximum volume.

32. The expandable tank of any one of claims 1 to 31 , wherein the volume of the tank space is set by the at least one actuator such that it is independent on the liquid loading weight.

33. The expandable tank of any one of claims 1 to 32, wherein the at least one actuator is inoperative when liquid is present within the tank space.

34. The expandable tank of any one of claims 1 to 33, further comprising a stabilization mechanism connected to the bottom shell and the upper shell configured to provide stability upon moving the bottom shell between the fully expanded position and the collapsed position.

35. The expandable tank of claim 34, wherein the stabilization mechanism is a scissor-like extendable assembly.

36. The expandable tank of any one of claims 1 to 35, where the liquid is water, a flame retardant chemical, or a combination thereof.

37. The expandable tank of any one of claims 1 to 36, for use on a helicopter chosen from Airbus Super Puma models AS332L, AS332L1 , AS332L2, and EC225LP aircraft.

38. Use of an expandable tank of any one of claims 1 to 36, for firefighting applications.

39. Use of at least one actuator for adjusting a volume of a tank space in an expandable tank, wherein said at least one actuator is disposed inside said tank.

40. Use of an expandable tank of any one of claims 1 to 36, wherein the helicopter is landed on the ground for filing with the liquid.41 . A method for controlling a volume of an expandable tank mounted on a helicopter, comprising adjusting a bottom shell of the expandable tank with at least one actuator, wherein said at least one actuator is at least partially disposed inside said expandable tank.

42. The method of claim 41 , wherein at least partially disposed inside said expandable tank comprises at least 50% of the length of the actuator.

43. The method of claim 41 , wherein at least partially disposed inside said expandable tank comprises at least 75% of the length of the actuator.

44. A method for firefighting using an expandable tank as defined in any one of claims 1 to 36, the method comprising: controlling the volume of the expandable tank space by actuating the at least one actuator to select a predetermined volume; filing the tank space with the liquid; and discharging the liquid at the predetermined fire location for firefighting.

45. A method for filing a belly-mounted helicopter firefighting expandable tank, the method comprising: selecting a predetermined volume of the expandable tank, controlling the volume of the expandable tank to the predetermined volume; filing the expandable tank with a liquid while the helicopter is on the ground.

46. The method of claim 44 or 45, wherein controlling the volume of the expandable tank comprises adjusting a bottom shell between at any position at any position between a fully expanded position and a collapsed position, optionally at a partially expanded position when the helicopter is on the ground.

47. The method of any one of claims 44 to 46, wherein controlling the volume of the expandable tank comprises adjusting a bottom shell between at any position at any position between a fully expanded position and a collapsed position with at least one actuator disposed inside the expandable tank.

48. The method of any one of claims 44 to 46, wherein controlling the volume of the expandable tank comprises adjusting a bottom shell between at any position at any position between a fully expanded position and a collapsed position with at least one actuator disposed inside the expandable tank, wherein at a partially expanded position when the helicopter is on the ground.

49. A method for firefighting with a belly-mounted helicopter firefighting expandable tank, the method comprising: filing the expandable tank with a liquid when the helicopter is on the ground; taking off to a predetermined fire location; and discharging the liquid at the predetermined fire location for firefighting.