WO2018165699A1

WO2018165699A1 - Airborne water scoop

Info

Publication number: WO2018165699A1
Application number: PCT/AU2018/000036
Authority: WO
Inventors: Andrew Scott DAVEY; Samuel Robert MCCABE
Original assignee: Rapid Response Systems Pty Ltd
Priority date: 2017-03-17
Filing date: 2018-03-16
Publication date: 2018-09-20

Abstract

Disclosed is a water scoop for attachment to an aircraft having an associated water storage hopper. The water scoop is used for scooping water from a body of water. The water scoop has a boom pivotably attached and depending from the underside of the flying aircraft while the boom assembly is partially submerged in a body of water. There is a water inlet located at a lower region of the body of the boom assembly for drawing water from the body of water. There is a water communication arrangement carried by the body of the boom assembly for communicating water from the water inlet to the water storage hopper. There is a hydrofoil located adjacent the water inlet and shaped such that, in use, when passing through the body of water, the inlet of the boom assembly is positioned below the surface of the water body. There is also at least one projection depending from the boom assembly located and sized to enter the water before the water inlet enters the water, wherein the projection stabilises the boom assembly as it scoops water from the body of water.

Description

AIRBORNE WATER SCOOP

FIELD OF THE DISCLOSURE

[0001] The disclosure relates to a water scoop for a fixed-wing aircraft that can be used to fill a water storage tank while the aircraft flies above a body of water for later controlled dumping of the collected water over a fire-stricken area.

BACKGROUND

[0002] It is known for suitable aircraft to have a water scoop structure. For helicopters, it is sufficient for the scoop to comprise a flexible hose lowered from the hovering craft until it enters the water. For fixed-wing aircraft the scoop structure is pivoted at a forward end to the underside of the aircraft's fuselage to allow the free end of the scoop structure to be lowerable into the water body. The scoop structure includes a water carrying duct incorporated into the scoop structure to carry water from the free end of the scoop structure to a water storage tank mounted in the fuselage of the aircraft. When the aircraft is flying close enough to the surface of a body of water, the water scoop structure can be lowered so that the scoop at the free end of the boom assembly enters into the water body to thereby scoop up water into the water carrying duct, which carries that water to the water storage tank. There is a water inlet located at the free end of the scoop structure and the effectiveness of the placement of the scoop into the body of the water is very much up to the skill of the aircraft pilot, who determines to a large degree the ability of the aircraft to fly at the required height. Other concurrent considerations include: to maintain control at the required height despite wind conditions; increases in weight as the water tank/s fill with water; the drag of the scoop (since once a scooping run is established there will be changes in scoop drag which are directly related to the depth of the boom assembly in the water and the additional weight of the aircraft as water is taken on via the scoop structure); changes associated with small height changes of the aircraft and the effect that has on placement of the end of the scoop into and out of the water body; and the speed of the aircraft to maintain flight while having the aircraft engine output enough power to maintain the necessary flight speed while both the drag of the scoop structure and the total weight of the aircraft changes as water is forced into the tank/s through the water carrying duct.

[0003] However, a need exists for an arrangement and method of operation to lessen the burden of the pilot to effectively and safely control the aircraft during the scooping of water from a water body for loading water for fire-fighting purposes. BRIEF DESCRIPTION OF ASPECTS OF THE DISCLOSURE

[0004] In an aspect there is a water scoop for attachment to an aircraft and an associated water storage hopper, for scooping water from a body of water. The water scoop comprises, at least, a boom assembly having a body. The body is pivotably attached and depending from the underside of the flying aircraft while the boom assembly is partially submerged in a body of water. The body of the boom assembly further comprises, a water inlet located at a lower region of the body of the boom assembly for drawing water from the body of water; a water communication arrangement carried by the body of the boom assembly for communicating water from the water inlet to the water storage hopper; a hydrofoil located adjacent the water inlet and shaped such that, in use, when passing through the body of water, the inlet of the boom assembly is positioned below the surface of the water body; and at least one projection depending from the boom assembly located and sized so as to enter the water before the water inlet enters the water, wherein the at least one projection stabilises the boom assembly.

[0005] In a further aspect there is a method to adjust the drag force of a boom assembly depending from the underside of a flying aircraft while the boom assembly is partially submerged in a body of water, the boom assembly having: a water inlet for drawing water from the body of water; a water outlet for providing water to a water hopper located on the aircraft; an hydrofoil located adjacent the water inlet and shaped such that, in use, when passing through the body of water, the inlet of the boom assembly is positioned below the surface of the water body; a water communication structure located between the water inlet and water outlet; and an adjustable water flow regulator arrangement adjustable between a first state of no change to the water flow along the water communication structure and a second state of at least partially redirecting the water flow out of the water

communication structure, the method comprising the step of adjusting the drag force of the boom assembly, in use, by adjusting the state of the adjustable water flow regulator arrangement.

[0006] In addition to the aspect previously described, the method comprises the further steps of: measuring the angle of attack of the flying aircraft; comparing the current angle of attack of the aircraft against a predetermined angle of attack at which the stall occurs; and controlling the adjustment of the drag force of the water by adjusting the state of the adjustable water flow regulator apparatus so as to maintain a predetermined margin between the current angle of attack and the predetermined angle of attack at which the stall occurs.

[0007] In a further aspect there is a boom assembly for mounting to the underside of an aircraft having a water storage hopper, for storing water, in use, the aircraft being flown over a body of water, the boom assembly comprising: a body structure; a water inlet for, in use, drawing water from the body of water located at the free end of the body structure; a water outlet for, in use, providing water to the water storage hopper located at the aircraft end of the body structure; a hydrofoil located adjacent the inlet shaped such that, in use, when passing through the body of water the inlet of the boom assembly is positioned below the surface of the body of water; a water communication structure located between the water inlet and water outlet; a gimbal located between the body structure and the aircraft for pivotably connecting the body structure to the aircraft; and an adjustable water flow regulator arrangement adjustable between a first state, in use, of no change to the water flow along the water communication structure between the water inlet and the water outlet, and a second state, in use, of restricting the water flow along the water communication structure between the water inlet and the water outlet to adjust, in use, the drag force of the boom assembly.

[0008] Further to the prior aspect of the boom assembly, wherein the adjustable water flow regulator is a waste water outlet and a valve arrangement, located adjacent the water inlet, wherein the valve arrangement is adjustable between a first state of no change to the water flow along the water communication structure between the water inlet and the water outlet, and a second state of at least partially directing the water flow out of the water communication structure between the water inlet and the water outlet by directing waste water out of the boom assembly.

[0009] Yet further to the prior aspect of the boom assembly, wherein the adjustable water flow regulator is arranged to direct water to flow substantially from the water inlet.to the waste water outlet.

[0010] Yet further to a prior aspect of the boom assembly, wherein the adjustable water flow regulator is an adjustable valve arranged to be adjustable between a first state of no change to the flow of water into the water inlet and a second state of restricting the flow of water into the water inlet.

[0011] In a further aspect of the boom assembly there comprises a control arrangement for controlling the state of the adjustable water flow regulator arrangement comprising: a means to adjust the drag force of the boom assembly, in use, by adjusting the state of the adjustable water flow regulator arrangement.

[0012] In a further aspect of the boom assembly, wherein the means to adjust the drag force of the boom assembly comprises: a means to measure the angle of attack of the flying aircraft; a means to measure the current speed to the flying aircraft; a means to compare the current speed of the aircraft against a predetermined stall speed for the measured angle of attack; and a means to adjust the the drag force of the boom assembly by adjusting the state of the adjustable water flow regulator apparatus to as maintaining a predetermined margin between the current speed and the predetermined stall speed. [0013] Throughout this specification and the claims that follow unless the context requires otherwise, the words 'comprise' and 'include' and variations such as 'comprising' and 'including' will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

[0014] The reference to any background or prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that such background or prior art forms part of the common general knowledge.

[0015] Suggestions and descriptions of other embodiments may be included within the disclosure, but they may not be illustrated in the accompanying figures or features of the disclosure may be shown in the figures but not described in the specification.

[0016] It should be appreciated that the present disclosure can be implemented in numerous ways, including as a process, an apparatus, a system, or a computer-readable medium such as a computer- readable storage medium or a computer network wherein program instructions are sent over wireless, optical, or electronic communication links. It should be noted that the order of the steps of disclosed processes may be altered within the scope of the disclosure.

[0017] The use of "e.g.," "etc.," "for instance," "in an example" and "or" and grammatically related terms indicate non-exclusive alternatives without limitation unless otherwise noted. The use of "optionally" and grammatically related terms means that the subsequently described element, event, feature, or circumstance may or may not be present or occur and that the description includes instances where said element, event, feature, or circumstance occurs and instances where it does not. The use of "attached" refers to the fixed, releasable, or integrated association of two or more elements and/or devices. Thus, the term "attached" includes releasably attaching or fixedly attaching two or more elements and/or devices. The use of "diameter" refers to the length of a straight line passing from side to side through the center of a body, element, or feature, and does not impart any structural configuration on the body, element, or feature.

[0018] A detailed description of one or more preferred embodiments is provided below along with accompanying figures that illustrate by way of example the implementation of those embodiments. The scope of the disclosure is limited only by the appended claims and the disclosures encompass numerous alternatives, modifications, and equivalents. For example, numerous specific details are outlined in the following description to provide a thorough understanding of the presented

implementations. The present disclosures may be practiced according to the claims without some or all of these specific details. For clarity, technical material that is known in the respective technical fields has not been described in detail so that the present disclosure is not unnecessarily obscured.

BRIEF DESCRIPTION OF THE FIGURES

[0019] Figure 1 depicts a fire-fighting aircraft scooping water from a river;

[0020] Figure 2 depicts a fire-fighting aircraft scooping water from an ocean;

[0021] Figure 3 depicts a fire-fighting aircraft dumping water on to a fire-stricken area;

[0022] Figure 4 depicts a perspective view of an embodiment of a boom assembly;

[0023] Figure 5 depicts a perspective cross-sectional view of an embodiment of the blade portion of the boom assembly being part of the water scoop of Figure 4;

[0024] Figure 6 depicts a perspective front side view of an embodiment of a water-scooping fitting;

[0025] Figure 7 depicts a perspective rear side view of an embodiment of the water scooping fitting of Figure 6;

[0026] Figure 8 depicts a perspective view of an embodiment of a hydrofoil;

[0027] Figure 9 depicts an embodiment of an adjustable waste gate actuation arrangement;

[0028] Figure 10 depicts a perspective view of an embodiment of a hydrofoil;

[0029] Figure 11 depicts an alternative hydrofoil assembly;

[0030] Figure 12 depicts a front perspective view of the hydrofoil assembly of Figure 11;

[0031] Figure 13 depicts a rearward perspective view of the hydrofoil assembly of Figure 11 ;

[0032] Figure 14 depicts an embodiment of a gimbal comprising a mounting frame arrangement, a base plate and a circular plate;

[0033] Figure 14A depicts an alternative boom assembly attachment arrangement; [0034] Figure 14B depicts the gimbal in an exploded view of the alternative boom assembly attachment arrangement of Figure 14A;

[0035] Figure 15 depicts a perspective side view of an embodiment of a retracted (up) boom assembly attached to the gimbal where the gimbal is located against the undercarriage of an aircraft;

[0036] Figure 16 depicts a perspective side view of an embodiment of a retracted (up) boom assembly against the undercarriage of an aircraft;

[0037] Figure 17 depicts an embodiment of a winch unit;

[0038] Figure 18 depicts various plots from a simulation along a common time line of variations of gross weight verses air-speed, water flow verses angle of attack and weight of water in the hopper verses pipe flow for a known condition;

[0039] Figure 19 depicts various wheel heights above the water body and consequent boom assembly angle effects on water flow percentages;

[0040] Figure 20 depicts the desired length of the blade as determined by the minimum height condition of the aircraft flying over the water body;

[0041] Figure 21 depicts the change in the position of the center of gravity as a percentage of the Mean Dynamic Chord of the aircraft;

[0042] Figure 22 depicts alternatives for boom assembly location along the airframe undercarriage;

[0043] Figure 23 depicts the preferable angle that the boom assembly hangs relatively to the horizontal;

[0044] Figure 24 depicts a flow diagram of the steps of adjusting the drag force of the boom assembly; and

[0045] Figure 25 depicts an embodiment of a control module. DETAILED DESCRIPTION OF EMBODIMENTS

[0046] There are many intersecting requirements that make the design of a water scoop system for attachment and safe working with a firefighting aircraft which can preferably deliver practical refill capability across a wide range of conditions. Safety and performance are desired in operating environments starting at standard sea level up to 6,000 feet altitude, and International Standard Atmosphere at + 30 degrees Celsius, in calm air or with 30-knot winds. The design is preferably not sensitive to choppy surface conditions and should be useable over sheltered or calm ocean water.

[0047] In an embodiment, a water-scooping and delivery boom assembly is 6.3 meters long and is used at what is considered a safe scooping height where the wheel height above the water body surface is between just above zero (not recommended) to as high as 3.7 meters above the water body.

[0048] It is desirable in typical conditions that the overall system can be used to refill the aircraft fitted water storage tanks/hopper (a water tank in firefighting aircraft is sometimes referred to as a hopper) within a flying distance of about 2,500 meters over the water body, which would preferably take about 60 seconds. This distance is readily accommodated by most significant water bodies. Turns as tight as 1 km radius are possible during scooping without reducing safety margins, expanding the list of available options. In North American operations where higher altitudes are common, larger water bodies are more readily available.

[0049] The performance described is preferably achieved using stock engine power and minimal airframe modification. Total installation weight of the boom assembly but not the loaded water is preferably lighter than 200 kg, most of which is readily removable when the scoop is not required so that the same aircraft can be loaded with water on land and used for distribution of the loaded water over a fire-stricken area. Compared to the water scoop currently available for an AT-802F Fire Boss, an embodiment of a water scoop as described herein is around 900 kg lighter and has a negligible impact on flight performance. This weight difference can be used to carry more water, retardant and fuel while having the capability for better performance when more lightly loaded allows faster ferry and greater manoeuvrability.

[0050] Preferably, an existing aircraft system should not be affected by the installation of the water scoop which includes a boom assembly, and in particular groundwater refill, water dump and vent systems will function normally, and the aircraft may be operated the same as one without a scoop if used as a water bomber that is required to land to be refilled. [0051] Figure 1 depicts a fire-fighting aircraft scooping water from a river, Figure 2 depicts a fire- fighting aircraft scooping water from an ocean and Figure 3 depicts a fire-fighting aircraft dumping water onto a fire-stricken area.

[0052] An embodiment of a boom assembly of a water scoop is depicted in Figure 4. The

construction is mostly of aluminium alloy for reasons of weight and corrosion resistance, with stainless steel in areas that require strength and corrosion resistance and bronze for other parts.

Assembly of the various parts can use fasteners (screws, bolts, etc.) having, where required, suitable corrosion resistance, tensile and shear strength. In a preferred embodiment, the boom assembly is 5.3m long.

[0053] The boom assembly 40 of a water scoop at one end is to be attached to the under-carriage of an aircraft using a cast aluminium alloy fitting 41 the shape of which is adapted to accommodate the longitudinal shaft of a mounting bolt that, once fitted between spigots, can be incorporated into the under carriage of the aircraft, and thus allow the fitting (and boom assembly) to rotate about the longitudinal axis of the bolt so that the boom assembly can pivot about the fitting point, and thus be raised, and lowered in use. The articulation provided is but one degree of freedom of the boom assembly with respect to the airframe of the aircraft. A gimbal assembly will be described later in the specification that provides for movement of the boom assembly to compensate for the yawing moment of the airframe.

[0054] The fitting 41 is also shaped to accommodate the end of a pipe 42 of stock aluminium alloy tube. In this embodiment the pipe, part of a water communication structure located between the water inlet located at one end of the boom assembly and a water outlet located at the other end of the boom assembly, allows for the communication of water up the boom assembly from the inlet and into the boom assembly, in this embodiment a scoop portion (to be described later) through the fitting 41 and into a flexible pipe (not shown) attached to the fitting, which thus communicates the water to the tank or tanks therein. The connectedness of all the parts being described need not necessarily be water tight, but minimisation of water loss is preferred. The water communication structure located between the water inlet and the water outlet can be of many connected parts, or it may comprise a continuous tube located internal of the various parts described herein, this being a description of an embodiment only.

[0055] A hollow joiner fitting 43 of cast aluminium alloy adapts the circular profile of the pipe 42 to the wedge-shaped longitudinally hollow blade 44 portion of the boom assembly, being part of the water scoop, by being shaped to attach at one end to the pipe and the other end to the blade portion also part of the water communication structure located between the water inlet and water outlet. The blade is hollow to accommodate communication of water up the boom assembly during the scooping process and also part of the water communication structure. At least some of the length of the blade will be submerged, at speed, in the water body, so the wedge of the blade is shaped and orientated to minimise drag while maintaining a stable path through the upper level of the water body as well as preventing cavitation damage and erosion. These parts are exemplary only as there will be many ways and parts that can achieve the function required with different weights and materials both heavier and lighter, flexible and stiffer, stronger and weaker depending on the desired functionality and requirements.

[0056] In an embodiment, the outside of the blade 44 supports a hydraulic ram 45 (to be described in greater detail later) which operates an optional gate 46 (also to be described in greater detail later and referred to herein as a waste gate) as the water that passes an open or partially open (adjustable state) gate during a scooping action and out of the boom assembly back to the water source is referred to as waste water.

[0057] The blade 44 extends from the joiner fitting 43 towards the free end of the boom assembly. A hollow scoop fitting 46 of cast stainless steel is shaped to fit, over and adapted to be fitted to, the open end of the blade, and is in this embodiment the water inlet. The scoop fitting includes an opening shaped and orientated to scoop water from the body of water while being immersed in the top of the water body at speed, and to communicate that water to the blade, and then through the pipe 42 then into the water storage tank in the aircraft. More will be described about the scoop fitting later. The previously mentioned and optional adjustable waste gate 47 (being one part of an embodiment of a waste water outlet) is located in the body of the scoop fitting and arranged to allow water being scooped by the scoop fitting to exit the scoop fitting before entering the blade. More about the adjustable waste gate, and how and when it is adjustable to be open (partially or fully) or closed, will be described later in the specification.

[0058] The hydrofoil 80 is but one embodiment of a hydrofoil disclosed in this specification, and is located on the free end of the water scoop^'s boom assembly 40 fitted in this embodiment to the body of the scoop fitting 46 and shaped so as to, when passing through the water at speed, draw the free end of the boom assembly 40 down into the water body but once at speed submerged in the water the hydrofoil is in equilibrium, such that there is no longer any tendency to drive the free end of the boom assembly lower or higher in the water. Hydrofoils are better known in the reverse configuration, arranged thereby to force a vessel fitted with them to rise out of the water as the vessel is propelled forward at speed. In a preferred embodiment, a super-cavitation hydrofoil as depicted in Figure 7 is attached to the free end of the boom assembly. Simulations, testing hundreds of sizes (of and configurations) of the scoop fitting depicted, determined the balance of water drawing capacity to drag factor was suitable for one of the embodiments described (which is comparatively heavier than other of the embodiments), and as will be described later in the specification there are alternative shapes, weights, strength and materials for a hydrofoil element as well as the boom assembly.

[0059] Figure 5 depicts a perspective cross-sectional view of an embodiment of a portion of the blade 44 of the boom assembly 40 which is preferably constructed of aluminium alloy extrusion. The leading edge 50 of the blade and a rear-cavity shape provides zero cavitation tendencies across the fore body at high speed, preventing cavitation damage and erosion, as a portion of the boom assembly may enter the water body at speed. The features of this embodiment of the boom assembly include two spars 52 and 54, one internal and the other one forming a portion of the outer wall, each 16 mm thick to provide stiffness, strength, and material for attachment of various features (end fittings, rear mounted pushrod, etc.), as illustrated by the holes 56. Both longitudinal cavities 58a and 58b may carry water. The wall thickness is 4 mm, the chord length is 228 mm, the maximum thickness is 50 mm, and the blade portion weighs 8.5 kg per lineal metre. Different designs and materials can be chosen for this portion of the boom assembly to allow for the weight consideration to be primary.

[0060] Figure 6 depicts a perspective front side view of an embodiment of a scoop fitting 46 wherein the scoop fitting is separate from the hydrofoil and the blade but in this embodiment is part of the boom assembly. The scoop fitting having an opening 62 (approximately 35 mm wide and 100 mm tall and aligned to the leading edge 50 of the blade 44) and portions of the scoop fitting housing 66 adapted to provide for the fitment of the scoop fitting to the blade and carry, when fitted in a particular embodiment, the hydrofoil depicted n Figure 7 in this embodiment. However, there may also be other hydrofoil shapes fixable to the free end of the boom assembly and thus to become part of the boom assembly. There is also the option of fitting an adjustable waste gate arrangement depicted in Figures 7, 8 and 9. In the arrangement depicted, there is a forward facing profile 64 which is shaped to minimise cavitation and which is also shaped much the same as the leading edge 50 of the blade.

[0061] The preferred material for the scoop fitting 46 is stainless steel, and in this embodiment, the total weight of the scoop fitting is 7.3 kg. However, various different shapes and sizes will result in various different weights. Various fixing apertures are depicted in the upper portion of the scoop fitting, and they are used for the fixing of the scoop fitting to the free end of the blade 44.

[0062] Figure 7 depicts a perspective rear side view of the scoop fitting 46 of Figure 6, in particular illustrating an aperture 74 suitable for fitment of an embodiment of an adjustable waste gate which is an optional element of the scoop fitting.

[0063] An optional adjustable waste gate arrangement, forming a waste water outlet, could be located elsewhere on the boom assembly, for example, along the blade 44, the pipe 42 or possibly the hydrofoil or any of the fittings, indeed any location intermediate the end of the boom assembly 40 and its free end.

[0064] An embodiment of the adjustable waste gate fitted to the scoop fitting 46 comprises gate 76 (appearing, in one embodiment, as being planar but the gate could also be non-planar in shape more like that depicted in Figure 8). The gate is sized to fit between the sides of an internal rear portion of the scoop fitting housing 66 and adapted, along at least a portion of the longer sides of the gate, to fit within and slide into, and slide within the slot 72, thus making the state of the gate adjustable, between a closed state, and an open state. The degree of openness of the gate is also adjustable. These two elements are an embodiment of an optional waste water outlet arrangement which is adjustable between a closed condition and an open condition. The embodiment described is but one arrangement.

[0065] The material of the optional waste gate is bronze, as it needs to have strength enough to resist the pressures involved. The slot is formed by continuous walls 72a, 72b and 72c formed in the scoop fitting housing 66 and those walls extend down the inside of the scoop fitting housing, as depicted, and continue across the inside of the base surface of the scoop fitting housing (not shown) and then extend up the inside of the scoop fitting housing (not shown). The slot is continuous and configured by way of its depth to provide sufficient material with sufficient strength to support the forces applied on the gate by water entering and flowing up towards the blade 44 or through the opening created as the gate slides and thus is adjusted in position along the slot.

[0066] Water entering the forwardly located scoop opening 62 is directed upward (relative to the end of the scoop fitting 46 connected to the hydrofoil) and into the connected blade 44 when the gate is closed. In this embodiment, the closed position/status of the gate is achieved when the gate is located at the lowest position it can take in the slot 72, as that seals against the egress of the water from the scoop fitting or past the gate. The sealing need not be water tight, but it will likely be so since the pressure of water on the inside surface of the gate will force the sides of the gate within the slot against the wall 74a of the slot and also those portions of the gate adjacent the side of the opening 62.

[0067] Water entering the forwardly located scoop opening 62 is directed outward (relative to the end of the scoop fitting 46 connected to the hydrofoil) and through the opening created when the gate is open. In this embodiment, the open position/status of the gate is achieved when the gate is located anywhere above the lowest position it can take in the slot. In this embodiment of the scoop fitting, the portion of the gate within the slot will continue to at least partially seal against the egress of the water from the scoop fitting past the gate itself, but the opening created will allow a portion of the water entering the scoop fitting to escape back to the source of that water. [0068] The material of the scoop fitting housing 66 is stainless steel, and the material of the optional adjustable waste gate is bronze to also facilitate a smooth slide of the bronze waste gate along the slot 72 formed by walls 72a, 72b and 72c in the stainless steel scoop fitting housing.

[0069] Control of the degree of opening (adjustment) of the waste gate position provides the effect of adjusting the drag created by the boom assembly 40 while a portion of the boom assembly is within the water body, and this can be critical when the scoop arrangement, boom assembly and fittings are heavy relative to other embodiments described in this specification.

[0070] Control of the closed state and degree of opening (adjustment) of the adjustable waste gate 76 is achieved by way of an actuation arrangement, in one embodiment, a hydraulic ram (not shown in Figures 6 or 7) and a mechanical connection (not shown in Figures 6 or 7) between the ram and the top of the gate 76a (Figure 8). The connection is rigid so that the operation of the ram will move the gate along the slot 72. In another embodiment (not depicted), the gate is biased closed or open, and the actuator is arranged to open or close against the bias as required.

[0071] Figure 8 depicts an embodiment of an optional adjustable waste gate for fitment to the scoop fitting 46 depicted in Figures 6 and 7. The waste gate 76 incorporates a curved portion 82 to redirect the flow of water entering the scoop fitting forward facing aperture 62 of the scoop fitting 46 and up (along the path of the illustrated arrow) into the blade 44. A lug 84 located intermediate the ends of the elongate waste gate body incorporates an aperture 88 for fixing of one end of an actuator, in this embodiment one end of a rigid connection between the lug and a ram (not shown). The lug also incorporates tabs 86 (one shown on the visible side of the lug and one not shown on the opposite side of the lug), and each tab is sized to slide along the slot 72. At the nominal lower end of the adjustable waste gate, there are further tabs 87 (one shown on the visible side of the lug and one shown on the opposite side of the body of the waste gate), and each tab is sized to slide along the slot. The nominal upper end of the waste gate is elongate and sized to slide into a slot located internal to the blade and not shown in Figure 5 relating to the blade. The weight of the bronze waste gate is 1.8 kilograms.

[0072] Figure 9 depicts an embodiment of a portion of an optional adjustable waste gate actuation arrangement, being in this embodiment a hydraulic ram 90 (not shown) and connection rod 92. In an embodiment, the ram is a Bosch CDL2 -series actuator being a 25 mm bore version that has sufficient strength to drive the adjustable waste gate at a sufficiently high speed. It has a maximum pressure rating of 2,300 psi, so a pressure reducer will be required for use if an Air Tractor AT-802 firefighter aircraft is used since the Air Tractor AT-802 includes a 3,000 psi hydraulic system. The hydraulic ram is located high on the blade (not shown in Figure 9 but may be visible with close inspection in Figure 4) so that the ram is clear of the water most of the time. The connection rod of the ram is sized and of sufficient tensile strength so that it won^'t buckle if the adjustable waste gate is jammed. The connection rod is connected at one end to the aperture 88 of the lug 84, with the connection being one that allows there to be rotation with respect to both parts relative to the other but it does not need to. The waste gate 76 is secured in a slot 72 by tabs 86 and 88 partway along and at the bottom of the waste gate, so that the waste gate will not kick over and jam as the ram operates to slide the adjustable waste gate from a closed state (as shown) to an open state, the size of the opening created being controlled by the retraction of the hydraulic ram in terms of degree and speed of travel.

[0073] Figure 10 depicts a perspective view of an embodiment of a hydrofoil 80 wherein the hydrofoil includes super-cavitation sections 82 that perform appropriately up to 120 knots. The sharp leading edge 84 of the hydrofoil forces separation of the water over and above the hydrofoil but primarily above, thereby reducing drag, and preventing micro-bubbles from forming. The hydrofoil is manufactured in high-strength steel and, as depicted, has the widest span of 200 mm and weighs 4.1 kg. The orientation of the hydrofoil with respect to the blade is determined by the angle of the base shape of the scoop fitting 46 (refer to Figure 7) and the upper surface 86 of the hydrofoil. Attachment of the hydrofoil to the scoop fitting is achieved using ½ inch bolts which are attached to the hydrofoil at the locations 88 indicated from within the scoop fitting housing 66.

[0074] Figure 1 1 depicts an alternative hydrofoil assembly 200 formed in part by a body 202. The forward facing opening 204 is an entrance provided into the body 202 through which water enters the submerging or submerged hydrofoil assembly, as it is being dragged along at speed through the water. Water entering the body 202 is then diverted into the suspended boom assembly (which is, in one embodiment, of the type described previously in the specification or it may be a similarly constituted arrangement, but possibly of different material, shape, width, length, weight and flexibility). After travelling up the boom assembly, the water is eventually deposited in the water holding tank of the aircraft (not shown). The volume of the cavity within the body 202 into which the water enters through the opening 204, is partly related to size of the boom assembly structure from which is fixed, wherein the depth of the boom assembly structure (front to rear), and the width (side to side), determines to some degree the size of the cavity as well as the open top of the cavity through which water flows from the cavity into the lower portion of the boom assembly structure. The aperture 206 in the upper portion of the body 202 comprises all the aperture openings 206a, 206b, 206c, and 206d through which water flows into the lower portion of the boom assembly (not shown) to which the hydrofoil arrangement is fixed. The projectile like shape of the body assists to minimise the drag of the body through the water, which is also related to the various hydrodynamic properties of the body preferably arranged to reduce cavitation and eddies of the water flowing over the outside of the body 202. The internal shape of the body 202 is also shaped to minimise drag and eddies internal of the body as water enters the body and exits the body at great speed. The rate of water lift through the combination of hydrofoil assembly and the boom assembly will be affected by the size of the opening, the ease of transition and resistance to flow of the water entering into the boom assembly and it travels via the boom assembly up to the aircraft mounted tank. One such rate of water collection is 1.9 litres per meter (of travel of the aircraft) and another rate is 0.8 litres per meter (of travel of the aircraft). These rates are measured rates during testing and provided as illustrative examples only.

[0075] Figure 1 1 also depicts one configuration of hydrofoil blades 208, and in this embodiment, each hydrofoil is of the same shape, and one such hydrofoil is located opposite lateral sides of the body 204 with the opening 202 centrally located. Earlier described features of the shape and angle of disposition in the water, at speed, of the hydrofoil, are applicable to the shape depicted in Figure 1 1.

[0076] Figure 1 1 also depicts lugs 210a and 210b located on the trailing end of the hydrofoil assembly integrated, for the depicted embodiment, with the bod)' 202. However, those lugs may be fixed as separate lugs by way of welding and other suitable forms of fixing to the body 202 of the hydrofoil arrangement 200.

[0077] Figure 12 depicts a front perspective view of the hydrofoil assembly 200 of Figure 1 1, fixed to the end of a boom assembly 212 (the boom assembly may be of similar construction to that described previously in this specification). Figure 12 also depicts two projections 214a and 214b attached to the previously described lugs 210a and 210b respectively connected. The manner of connection in the depicted embodiment is by threaded bolts 216b (heads of which are depicted in Figure 1 1) which pass- through apertures in the projections and fix to apertures 216a located in the lugs (or are fixed relative to the lugs using nuts not shown). The projections 214a and 214b are arranged by way of their orientation to lie almost to the vertical (with respect to the water through which the hydrofoil assembly travels). Apparent to the eye is the slight angle to the vertical of the projections, such that the projections are closer at their attached end than their free ends. This slight splaying of the projections (relative to each other and the vertical longitudinal axis of the boom assembly) can have the effect of assisting stabilisation as the water flows about and past the projections but the primary role of one or more of the projections is to stabilise (minimise the lateral (right-to-left) movement with respect to the linear forward path of the boom assembly and hydrofoil assembly) as the lower end region of the boom assembly and the hydrofoil assembly enters and is then dragged through the water. The stability assistance is especially critical as a precursor to the hydrofoils as they first break the waters^" surface. At that stage of the process, of scooping water, the effect of the hydrofoil is at a minimum, and the resistance of the partial submersion of the opening with partial entry of water into the interior of the body 202 can result in uneven (as well as turbulent) flows, that if impinging with force to one or other of the sides of the depending boom assembly, can tend the free end of the boom assembly and hydrofoil arrangement to deviate laterally from the substantially straight path that the aircraft is tracking. The reaction of the depending boom assembly will be to resist those temporary lateral forces once the elastic limits of the total boom assembly is reached and any give in the means of attachment of the boom assembly (at the to be described gimbal attachment arrangement) on the aircraft, means there will be an opposite force applied to the free end of the boom assembly which is mainly caused by the interplay between the hydrodynamic stability of the lower end of the boom assembly and the gimbal, which is at the upper region of the boom assembly. A yet further dynamic may be caused by a change in the flow of water into and through the body 202. The speed of submersion can lessen the time for these adverse oscillations/deviations to occur, but the forces involved can still result in lateral oscillation of the boom assembly, in the region of 1 to 4 cycles per second. However, the lateral forces applied along the full length of the boom assembly can result in undue stress and risk permanent damage or failure at relatively weak portions (joins, etc.) of the boom assembly.

[0078] The projections 214a and 214b are sized and located so as to enter the water surface first before the rest of the hydrofoil assembly, and since the substantially vertical and elongate shape of the projections is tracking the flight path first, later entry of the hydrofoil blades 208 is guided and further stabilised once any adverse water flows are encountered during the initial stages of submersion of the opening 204 and the full length of the blades 208. The path (depth and direction) taken by the free end region of the boom assembly, in particular, the hydrofoil assembly, as it travels through and below the surface of the water, is determined by some factors. Those factors include: the effect of the hydrofoil blades 208 in dragging the boom assembly deeper into the water but eventually to achieve an equilibrium state of not moving up or down in the water; the linear and vertical speed of the aircraft; the height of the aircraft above the water surface; the angle of the boom assembly relative to the aircraft; the angle of the aircraft to the level surface of the water body; and the direction of flight (since the boom assembly will track that direction within the ability of the submerged end of the boom assembly to stay true to the direction of travel).

[0079] The weight of the boom assembly and associated hydrofoil assembly can contribute to or lessen the stability of the boom assembly, as it enters and moves through the water at speed. Thus lower (relative weights) of the boom assembly and connected hydrofoil assemblies can adversely contribute to a lack of stability, which in most cases is the result of less downward force exerted by the freely hanging boom assembly, less rigidity/flexibility of the boom assembly (making the boom assembly easier to be caused to deviate laterally/sideways in its path through the water), or elastically return, or not return, from any lateral forces that impinge on that lower (free end) region of the lesser weight boom assembly during the time it is submerging or submerged, and the consequences of a series of oscillations sideways (relative to the path of the flight of the aircraft) movements, that can ultimately damage the boom assembly, sometimes to failure. Thus the importance of determining a way to increase stability at the critical time of entry to the water while maintaining a weight which if low allows for more water to be held in the aircraft mounted tanks, instead of the weight of a heavier boom assembly, boom assembly attachment arrangement and hydrofoil arrangement.

[0080] The shape and location of the projections depicted in Figure 12, is one embodiment of the possible shapes and position of an element which can provide stability during the entry of the lower portion of the boom assembly and hydrofoil arrangement in the water and during the time the hydrofoil arrangement is submerged and scooping water. In the depicted embodiment, the projections are sized and located such that the centre of pressure of the lowest 150 mm of the boom assembly is behind both the axis of the centre of mass of the boom assembly section (when full of water), running along the length of the boom assembly; and the elastic axis of the boom assembly, running along the length of the boom assembly. Therefore the projections are large compared with the depth of the hydrofoil assembly and located relatively far aft (the rear) of the hydrofoil assembly, that is slightly extended away from the rearmost portion of the body 202. As detailed previously, the two projections are not disposed vertical but tilted in line with the boom assembly as it depends from the undercarriage of the aircraft (notionally 45 degrees to the plane of the underside of the fuselage of the aircraft). Two projections were used, side by side, rather than a deeper single projection (i.e. which doubles their effect) but there can be embodiments where a single projection is possible. The portion of the projection located directly the rear of the hydrofoil blade is not as effective since it is then closer to any cavitation of the water that forms close to the hydrofoil blade. The net result is that the lower end of the boom assembly is stabilised and oscillations of the connection mechanism of the boom assembly to the undercarriage of the aircraft (such as for example, a gimbal arrangement) are convergent rather than divergent.

[0081] Different shapes for the projection/s being determined by way of calculation and reasonable experiment take into account speed, length (effective depth), total weight of the boom assembly, with other relevant factors to determine the most suitable length (effective depth) relative to the body 202 (how much lower does it or they (could be more than two projections) need to project), their size (from front to back), the angle from the vertical the projections should have in predetermined direction/s if two or more projections are used, etc. The embodiment of each of the projections depicted in Figure 12 have a single trailing edge, however, there may be various shapes of the trailing edge which induce or lessen the creating of cavitation, etc. The projections of the embodiment are each a single element, but there could be multiple parts arrayed to provide the shape required. The leading edge of each of the projections depicted in Figure 12 is linear, but the leading edge could be curved. The fixing arrangement depicted is an embodiment. The projections and the tabs could be a single element, as could the combination of the body 202, and projections 214a and 214b. The material from which the body and projections is made can be the same or different, but in this embodiment, the material is the same as described previously for the hydrofoil. [0082] Figure 13 depicts a rearward perspective view of the hydrofoil assembly 200 of Figure 11 with the projections 214a and 214b of Figure 12.

[0083] The total boom assembly will preferably be designed to withstand the following conditions: a. Maximum water speed:

1. Hot and high atmospheric conditions;

2. Nil headwind;

3. Maximum flying speed (intend to set to 120 KIAS, per maximum flap extension speed); b. Maximum depth; and

c. Maximum flow.

[0084] A 10% margin is applied to the maximum speed, and a 1.50 factor is added to the derived load to define the load for physical breakage.

[0085] From the above, the ultimate load for the boom assembly (a tension load) is determined to be about 100 dlo Newtons (kN), (22,500 lbs). The boom assembly and its fittings are in a preferred embodiment designed for this load. However, in service, the typical load on the boom assembly is expected to be about 26 kN (5,850 lbs). A boom assembly that can withstand the ultimate load conditions should be robust in service.

[0086] Figure 14 depicts one embodiment of a gimbal 110 (comprising a mounting frame arrangement 112 and a base plate 114, a circular plate 116 mounted to permit rotation relative to the base plate and a bracket 118 fixed to the circular plate) mounted to the underside of an aircraft 119. The bracket is adapted to permit the fixing of an end of the boom assembly 40. In an embodiment the aircraft is an Air Tractor AT-802 Firefighter in which case, the mounting location is behind the water storage hopper, in the area where there is currently an accumulator, the ground refill pipe and aft bubble of the adjustable gate box. Each aircraft to which the apparatus disclosed herein will require an inspection to determine the ability to fit the gimbal to its underside, but the concept is shown in Figure 14. The gimbal is designed to allow ranges of movement in pitch and yaw of the boom assembly 40.

[0087] Figure 14A depicts an alternative boom assembly attachment arrangement comprising a mounting bracket 300 having two mounting points arranged evenly about the center line of the aircraft^'s longitudinal center line further supported and fixed by rod-like brackets 302a and 302b. This assembly supports the attached end of the boom assembly 40, which is depicted as upper boom assembly member 304 pivotably attached to the mounting bracket 300. A pivot arrangement, referred to as a gimbal, is depicted in exploded view in Figure 1 IB. The gimbal permits freedom of the attached boom assembly with respect to the aircraft undercarriage in pitch and yaw. Relative movement of the boom assembly to move towards and away from the undercarriage is achieved by providing a pivot 309 about which the attached end of the boom assembly can depend from the underside of the aircraft undercarriage at angles varying between almost 0 to the undercarriage (parallel to the undercarriage for stowage during taxiing, landing and take-off) to about 40 to 50 degrees to the undercarriage (allows pitch variability), so that the free end of the boom assembly can enter the water during the scooping process. The connection to the mounting bracket also permits the boom assembly to pivot 310 laterally of the longitudinal axis of the body of the aircraft (allows for yaw). The allowable movement is constrained and controlled by the operation of two hydraulic pistons 312a and 312b connected pivotally at the cylinder end at 314a and 314b and also pivotally connected to mounting bracket 300 at the end of rods 306a and 306b of the hydraulic cylinder. The hydraulic cylinders are used to suppress pitching oscillations of the boom assembly particularly around the time at which the hydrofoil enters the water. This is to ensure a 'positive^" water entry which is predictable for the pilot, rather than skipping and eventual water entry at a time not readily anticipated, as well as stabilise the lateral movement of the boom assembly but only assist the suppression of that type of movement, since stabilisation of the free end submerged end of the boom assembly is primarily achieved by the use of one or more projections associated with the body of the hydrofoil assembly as described by way of embodiments in the specification.

[0088] Figure 15 depicts the boom assembly 40 attached to the gimbal 110 and in a retracted state, such that the boom assembly is located next to the underside of the aircraft 120. When the boom assembly is being retracted by a winch (not shown), a guide element 120 comprising a metal bracket projecting downward from the underside of the aircraft guides the boom assembly to the left side of the undercarriage as it is raised into the retracted position, so that the free end of the boom assembly does not foul on the tailwheel, which may occur depending on the length of the aircraft behind the fixing point of the gimbal and/or the boom assembly. The leftward orientation (with respect to a top view of the aircraft) of the free end of the boom assembly is facilitated by the rotational movement allowed by the gimbal 110. The guide element is sized to be clear of the ground but also to guide the boom assembly under the most adverse conditions. A side view of the retracted boom assembly is shown in Figure 16. In one embodiment, water will be conveyed from the end of the boom assembly to the water storage hopper using a 15.24 cm (6") diameter flexible hose (not shown) wherein the flexibility of the tube is required since that end of the boom assembly moves relative to the aircraft.

[0089] The winch installation 140 (not shown) located internal or external of the fuselage of the aircraft in an embodiment is a Warn Systems winch unit. The unit depicted in Figure 17 has a mechanical brake and a suitable load rating. The winch unit weighs 5.7 kg. The winch is installed in the rear portion of the fuselage. The boom assembly 40 will be held in the stowed position by the winch^'s mechanical brake, wherein the winch cable is pulled tight against a sprung stopper. The winch will lower the boom assembly to hang below the underside of the aircraft at about 50 - 60 degrees to the underside surface of the aircraft in-flight, so there is no requirement to drive the boom assembly deployed (down), it being sufficient to drive the winch to unwind thus lowering the boom assembly under its weight. The coupling shown at the end of the winch cable is not illustrative of the type of coupling between the cable and the boom assembly.

[0090] The vent system for permitting water to flow into the water storage hopper in the aircraft is preferred. Thus in an embodiment, an actuator linked to the boom assembly extend/retract switch is used to open the vent in preparation for scooping.

[0091] Thus the weights of elements of one of the heavier embodiments of the overall arrangement are as follows: boom assembly 80 kg; gimbal 20 kg; winch and guide element 14 kg; vent system 12 kg; hydraulics and control system (yet to be described) 14 kg, which totals 140 kg.

[0092] Airframe structural strength is a consideration, and with flaps down (e.g. lOdegree flap, as is planned for scooping) the manoeuvring load limit is 2.0 g. At 120 KIAS, in hot/high conditions with nil wind, the scoop would be capable of generating the equivalent of about 0.5 g. Therefore the boom assembly will be well within the wing strength limit. Overloading is thus not anticipated.

[0093] The flow rates for the embodiment described in detail above can be used to determine the distance to be flown with the scoop in the water body. In this regard, the scoop is sized to be capable of filling the water storage hopper over a 2,000 m flying distance. At full flow, this means the flow rate is a little more than 100 L/s at normal scooping speed. However, the achievable flow rate is limited by aircraft performance (specifically, excess thrust). The amount of water that can be taken on board with the scoop in the water for 2,500 m has been determined by simulation.

[0094] Simulations have been run across a range of conditions, varying headwind, temperature and altitude. The simulations make some assumptions:

a. The aircraft has a full water storage hopper when it reaches Maximum Take Off Weight (MTOW - being the heaviest weight at which the aircraft has been shown to meet all the airworthiness requirements of that aircraft);

b. Power is take-off power from a PT6A-67AG (1,350 horsePower (hP));

c. Flaps are set to 10 degrees, ready for climb-out; and

d. The aircraft wheel height is 1.7 m (5.6 feet) on average above the substantially level surface of the water body, which allows for a 0.5 -metre variation up or down without affecting operation. [0095] The pipe flow, being the amount of water flowing up the pipe, is affected by the size of the pipe. In practice, a larger pipe allows a smaller inlet opening which will have lower drag. However, a larger pipe also requires a larger blade, and the blade is the primary source of drag in the water. It can be shown, that the pressure losses in the system mainly come from the internal friction in the blade. Thus in the embodiment described the upper sections of the boom assembly use a 15.24 cm (6"(inch)) (inner) diameter pipe, which is sized to have a negligible effect on the pressure drop. The pressure drop associated with the height over water is variable both in absolute terms and relative to the flow- induced pressure drop. The performance of the system is not very sensitive to pipe flow performance. In typical conditions, reducing the pipe flow loss factor by 50% cuts the filling distance by around 13%.

[0096] In one embodiment, the control of the operation of the waste gate is for the purposes of control linked to angle of attack of the aircraft, and since that is the case, it becomes a one means of protecting against low-speed hazards. Figure 18 depicts a simulation indicating how control or the waste gate operates. The simulation assumes the aircraft is operating at 2,000 feet altitude there is a 15-knot wind and an International Standard Atmosphere (ISA) of + 15 degrees Celsius and the engine is set to takeoff power for the duration of the scoop. As aircraft weight increases, the minimum flying speed also increases and the excess thrust available decreases. When the aircraft weight reaches a level where the thrust is inadequate to support minimum flying speed, the waste gate opens to reduce the flow rate. Lower flow rates also create less drag and therefore allow the aircraft to maintain a safe flying speed.

[0097] Aircraft angle of attack is chosen as a reference parameter because, unlike airspeed, it gives a true indication of proximity to stall. The stall angle will be the same regardless of weight, ground effect, manoeuvring load factor, etc. In Figure 15 the 'ACL^" plot is analogous to angle of attack. When the ACL = 0, then the target angle of attack has been achieved, and the system controls the operation of the waste gate to taper off the flow.

[0098] A further variable is the scooping height, wherein the maximum wheel height is determined by the power of the hydrofoil and its ability to overcome the drag forces on the boom assembly. This determines the boom assembly angle. Because flow rate affects drag, the waste gate position also affects the maximum height. The hydrofoil size and angle are designed such that the boom assembly holds at approximately 45 degrees for the most relevant flight conditions. At this angle, the hydrofoil is also operating in the most efficient range. Figure 19 depicts various wheel heights above the water body and consequent boom assembly angle effects on water flow percentages. Wheel height is the remaining distance after subtracting a minimum depth and the height difference between the wheels and the pivot. This arrangement is illustrated in Figure 20 and where the desired length of the blade is determined by the minimum height condition. [0099] A yet further variable is the position and weight of the boom assembly, and thus the effect that has on weight distribution and then on the Center of Gravity (C.G.) of the whole aircraft most noticeable while the boom assembly is in the raised position and the aircraft has a full load of stored water. The boom assembly installation will add approximately 140 kg located at station 3,080 mm and will, therefore, move the C.G. about 60 mm aft when the aircraft is at maximum weight. This C.G. movement will probably require some ballast to be fitted to allow practical operations up to a maximum weight. Such a condition would require 135 kg installed above the engine to counteract the C.G. movement associated with the boom assembly installation. However, the addition of weight may not be necessary, if the aircraft has some margin to aft C.G. already.

[00100] Figure 21 provides a depiction of the change in the position of the C.G. as a percentage of the Mean Dynamic Chord (MAC) which is a specific chord line of a tapered wing. At the mean aerodynamic chord, the center of pressure has the same aerodynamic force, position and area as it does on the rest of the wing and for some aircraft, the center of gravity is expressed as a percentage of the length of the MAC of that particular aircraft. Figure 18 shows that alternatively, more forward locations could be found for some items of mass such as the hydraulic manifold and winch. The single almost vertical line shown lying within the envelope line is the new forward limit when the boom assembly is stowed (up).

[00101] When the boom assembly is deployed (down) or stowed (up), the C.G. will move somewhat. Figure 21 shows a new forward C.G. limit. If the aircraft is loaded aft of this limit with the boom assembly up, the C.G. will remain within the certified envelope when the boom assembly is lowered, to a deployed condition.

[00102] As noted elsewhere the boom assembly induces forces of comparable magnitude to the weight of a full water storage hopper while scooping water. The location at which these forces act on the aircraft affects aircraft handling. The boom assembly pivot is preferably situated such that the force vector from the boom assembly passes through the aircraft aerodynamic centre thus the minimal effect on aircraft handling. Issues include limiting any pitch-down tendency on entry to the water and ensuring adequate elevator travel to achieve stall speed. See Figure 22 illustrates the various alternatives for boom assembly location along the airframe undercarriage. As can be noted the boom assembly angle to the surface of the water body is 45 degrees, while in Figure 20 the angle is shown as 50 degrees. However, that is when the aircraft is at maximum height while the free end of the boom assembly is entering the water body and there is zero water flow up the boom assembly.

[00103] Handling of the aircraft is the main issue, and a 30=knot (kt) crosswind could generate sideslip angles (relative to the water) of around 20 deg. To permit some margin for manoeuvring, turbulence and/or unbalanced flight, at least 30 degrees of yaw capability is required at the gimbal. However, since the yaw pivot is very close to the C.G., no problem is expected with rudder travel. In an extreme circumstance, up to 15% of rudder deflection may be required to hold the aircraft at zero sideslip. About 10 degrees of roll will be required to balance the side force, and this may be the limiting factor in crosswind operations. All these parameters are known to the pilot, and they are responsible for flying in the conditions and the decision to scoop from the particular body of water.

[00104] The airborne trail angle, which is the angle that the boom assembly hangs at relative to the horizontal, is variable between the stages of the scooping process. The boom assembly should naturally hang below the aircraft at quite a steep angle (i.e. greater than 55 degrees to the horizontal), steeper than when it is in the water (refer to Figure 23). When the free end of the boom assembly first touches the water, it may skip a little because the aircraft is too high for the hydrofoil to keep the scoop in the water but the projections depicted in Figures 1 1, 12 and 13 are arranged to enter the water first and will minimise this possibly mode of reaction to water entry. No special control system is required to lower the boom assembly, except for the lengthening of the cable available from the winch as described previously or by using a hydralic source to drive one or more hydrallic pistons operable between the aircraft undercarriage or a frame attached to that undercarriage and the attached end of the boom assembly, since the action of the aircraft being lowered towards the surface of the water body, and the action of the hydrofoil as it penetrates the surface of the water body, will ensure the appropriate angle for scooping is achieved. The winch would never be engaged while scooping, due to having to overcome the hydrofoil, inducing a pitch moment on the aircraft and excessive pilot workload. Figure 23 depicts that the range of angles that will provide for the scoop to be located at a minimum depth into the water body being between 40 degrees and 50 degrees below horizontal.

[00105] The speed controller holds the aircraft at the most efficient scooping speed while protecting a safe margin above the stall, all the while delivering the maximum possible flow rate into the water storage hopper. There is more to the process than just controlling the waste gate to admit water at a rate which presumably the pilot considers "desired", and what is proposed, is a controller which is capable of working with the measured angle of attack to indicate to the pilot what the optimal flying speed is with reference to the angle of attack at that time.

[00106] Therefore, the approach uses three features:

1. A way to identify the optimal flying speed (note: the stall 'speed^" varies with aircraft weight, ground effect, flap position, and other variables);

2. A way to vary the balance between thrust and drag on the aircraft to make it accelerate or decelerate toward the optimal flying speed; and

3. A system or a skilled pilot to actively manage these features in real time. [00107] In one aspect there is a method to adjust the drag force of a boom assembly depending from the underside of a flying aircraft while the boom assembly is partially submerged in a body of water, relying on the boom assembly having: a water inlet for drawing water from the body of water and a water outlet for providing water to a water hopper located on the aircraft. As well as the above requirement, the hydrofoil located adjacent the water inlet located on the boom assembly is shaped such that, in use, when passing through the body of water, the inlet of the boom assembly is positioned below the surface of the water body. This is the case since the actual speed through the water and articulation of the boom permits there to be an angle change until the hydrofoil is in equilibrium, such that there is no longer any tendency to drive the free end of the boom lower or higher in the water. The water communication structure, for directing the scooped water into the water hopper, is located between the water inlet and water outlet and within the boom assembly.

[00108] In an aspect, there is a method involving the controlled adjustment to the adjustable water flow regulator arrangement between the first state of no change to the water flow along the water communication structure and a second state of at least partially redirecting the water flow out of the water communication structure.

[00109] In an aspect there is a method involving the step of adjusting the drag force of the boom assembly 414, in use, by adjusting the state of the adjustable water flow regulator arrangement. In an embodiment, referring to Figure 24, the steps of the method comprise: measuring the angle of attack of the flying aircraft 410; comparing the current angle of attack of the aircraft against a predetermined angle of attack at which the stall occurs 412, and if the angle of attack is within the predetermined range return to step 410, and if not, controlling the adjustment of the drag force of the boom assembly, by adjusting 416 the state of the adjustable water flow regulator apparatus. As the adjustment is made, the method returns to step 410, and if step 412 requires further adjustment with step 414, further adjustment is made and the process returns to step 210, so as to maintain a predetermined margin (as used in the comparison step 412) between the current angle of attack and the predetermined angle of attack at which the stall occurs.

[00110] In an embodiment, the adjustment signal that is generated is the output of the method disclosed herein and depicted in Figure 24. The signal is generated by a control module as depicted in Figure 25. The control module 422, in an embodiment, comprises: a Central Processing Unit (CPU) 224 for performing the method or any other suitable method to adjust the drag force of the boom assembly 414 apparatus, an embodiment of which is disclosed herein, the CPU having at least two signal inputs 1 relating to the disclosed method. A signal 426 from the angle of attack sensor is taken from the aircraft^'s equipment and provided to an input pin of the CPU. A signal from a hydraulic pump 428 (being the motive force to actuate a ram 230 which controls the state of the waste gate 432 is also provided to an input of the CPU, as is an embodiment, if possible a signal which provides the actual state of the water gate (where there is no real necessity for that signal since the action of the increase of decrease of drag effects by the operation of the waste gate is just as directly detected since it affects the angle of attack, which is already being detected. Various other signals are provided to the CPU: one being a failsafe signal from the hydraulic pump which indicates its lack of operation; and others not listed, but which may be included to increase the oversight of the various control elements and sensors on the aircraft. There are other signal outputs from the CPU: a failsafe signal from the CPU which orders the hydraulic control module 434 to control the waste gate to a closed state, to minimise drag at an instant in time when aircraft flying conditions require that.

[00111] The control module 422 also includes, in an embodiment, a signal conditioner 436 which provides an interface from the low current low voltage output of the CPU to the relatively high current and high voltage requirement to control or power aircraft equipment, which can have 24 or 48 volt systems and equipment.

[00112] The control module 422 also includes, in an embodiment, a memory 438 (nonvolatile). The control memory can store for reference by the CPU 424: aircraft parameters (unique to the actual aircraft to which the control module and other apparatus is fitted (including the variable of the aircraft stall speed for the aircraft condition, a predetermined margin for the angle of attack as known for the aircraft and its operating conditions)); and other information and data, pre-stored or stored and used during the operation of the aircraft generated by the CPU or various on-board sensors.

[00113] By way of an example only, the waste gate can be arranged to have a failsafe normally closed (NC) state which can only be changed by positive action against the NC bias by, in an embodiment, a rod connected to a hydraulic ram, which also has, in an embodiment, a normally open (NO) (normally extended) state.

Claims

1. A water scoop for attachment to an aircraft and an associated water storage hopper, for

scooping water from a body of water, the water scoop comprising:

a. a boom assembly having a body, the body pivotably attached and depending from the underside of the flying aircraft while the boom assembly is partially submerged in a body of water, the body of the boom assembly further comprising:

i. a water inlet located at a lower region of the body of the boom assembly for drawing water from the body of water;

ii. a water communication arrangement carried by the body of the boom

assembly for communicating water from the water inlet to the water storage hopper;

iii. a hydrofoil located adjacent the water inlet and shaped such that, in use, when passing through the body of water, the inlet of the boom assembly is positioned below the surface of the water body; and

iv. at least one projection depending from the boom assembly located and sized so as to enter the water before the water inlet enters the water;

wherein the at least one projection stabilises the boom assembly.

2. A water scoop for attachment to an aircraft according to claim 1 wherein there are two

projections and they are splayed laterally with respect to the longitudinal axis of the aircraft.

3. A method to adjust the drag force of a water scoop according to claim 1, the boom assembly depending from the underside of a flying aircraft while the boom assembly is partially submerged in a body of water, the boom assembly having: a water inlet for drawing water from the body of water; a water outlet for providing water to a water storage hopper located on the aircraft; a hydrofoil located adjacent the water inlet and shaped such that, in use, when passing through the body of water, the inlet of the boom assembly is positioned below the surface of the water body; a water communication structure located between the water inlet and water outlet; and an adjustable water flow regulator arrangement adjustable between a first state of no change to the water flow along the water communication structure and a second state of at least partially redirecting the water flow out of the water communication structure, the method comprising the step of:

a. adjusting the drag force of the boom assembly, in use, by adjusting the state of the adjustable water flow regulator arrangement.

4. The method according to claim 3 comprising the further steps:

b. measuring the angle of attack of the flying aircraft;

c. comparing the current angle of attack of the aircraft against a predetermined angle of attack at which the stall occurs;

d. controlling the adjustment of the drag force of the water by adjusting the state of the adjustable water flow regulator apparatus to maintain a predetermined margin between the current angle of attack and the predetermined angle of attack at which the stall occurs.

5. A boom assembly for mounting to the underside of an aircraft having a water storage hopper, for storing water, in use, the aircraft being flown over a body of water, the boom assembly comprising:

a body structure;

a water inlet for, in use, drawing water from the body of water located at the free end of the body structure;

a water outlet for, in use, providing water to the water storage hopper located at the aircraft end of the body structure;

a hydrofoil located adjacent the inlet shaped such that, in use, when passing through the body of water the inlet of the boom assembly is positioned below the surface of the body of water;

a water communication structure located between the water inlet and water outlet;

a gimbal located between the body structure and the aircraft for pivotably connecting the body structure to the aircraft;

an adjustable water flow regulator arrangement adjustable between a first state, in use, of no change to the water flow along the water communication structure between the water inlet and the water outlet, and a second state, in use, to at least partially redirecting the water flow out of the water communication structure between the water inlet and the water outlet to adjust, in use, the drag force of the boom assembly.

6. A water scoop according to claim 5 wherein the adjustable water flow regulator is a waste water outlet and a valve arrangement, located adjacent the water inlet, wherein the valve arrangement is adjustable between, a first state of no change to the water flow along the water communication structure between the water inlet and the water outlet, and a second state of at least partially redirecting the water out of the water communication structure between the water inlet and the water outlet by directing waste water out of the waste water outlet.

7. A water scoop according to claim 5 wherein the adjustable water flow regulator is an

adjustable valve arranged to be adjustable between a first state of no change to the flow of water into the water inlet and a second state of restricting the flow of water into the water inlet.

A water scoop according to claim 5 further comprising:

a control arrangement for controlling the state of the adjustable water flow regulator arrangement comprising:

a means to adjust the drag force of the boom assembly, in use, by adjusting the state of the adjustable water flow regulator arrangement.

A water scoop according to claim 5 wherein the means to adjust the drag force of the boom assembly comprises:

a means to measure the angle of attack of the flying aircraft; a means to measure the current speed to the flying aircraft; a means to compare the current speed of the aircraft against a predetermined stall speed for the measured angle of attack;

a means to adjust the the drag force of the boom assembly by adjusting the state of the adjustable water flow regulator apparatus to substantially maintain a predetermined margin between the current speed and the predetermined stall speed.