GB2163710A - Aircraft with water scoop - Google Patents

Abstract

An aircraft (1) has a boom (2) pivoted at its forward end to the underside of the aircraft's fuselage (4) and having at its rear end a scoop (11) connected via a duct (10) in the boom (2) to a water storage tank (14) mounted in the fuselage (4). When the aircraft (1) is flying closely above the surface (35) of a body of water (36), means (7,8) for lowering the boom may be used to dip the scoop (11) into the water to thereby refill the tank (14). The water may be jettisoned from the aircraft (1) by opening a dump door (15) built into the tank (14). <IMAGE>

Description

SPECIFICATION Aircraft Float aircraft, amphibious aircraft or aircraft with flying boat hulls, are often used for fire bombing operations around the coasts and in lakeland districts because it is possible for them, after dropping a load of water on a fire, to touch down on the surface of a body of water and, whilst maintaining speed close to takeoff speed, to scoop up a full water load, and then to apply full power to rise again, so reducing to a minimum the time required to replenish the water storage tank in the aircraft. When conventional land based aircraft are used for fire bombing, it has conventionally been assumed that these must return to a land base, come to a complete stop, and have their water storage tank recharged via a pressure hose prior to takeoff and return to the scene of the fire.

The object of the invention is to provide a system which enables a fire bombing aircraft to replenish its water storage tank without landing on land or water, and is therefore applicable to land based aircraft.

In accordance with the present invention an aircraft comprises a fuselage which contains a water storage tank provided with a dump door; a rearwardly extending boom which is pivoted at its forward end to the underside of the fuselage and which carries at its rear end a scoop connected via a duct in the boom to the tank; and means for lowering the rear end of the boom; whereby the tank may be replenished by flying the aircraft closely above the surface of a body of water with the scoop dipping into the water.

With this arrangement the water tank of the aircraft may be replenished quickly by flying the aircraft low over a lake or sea and lowering the boom so that the scoop scoops up water at a dynamic pressure which causes the water to ascend the duct and enter the tank.

When the tank has been refilled, the scoop will be lifted out of the water, by flying the aircraft upwards or by raising the boom, and with the boom in its raised position, the aircraft will be flown to the site of the fire where the dump door of the tank will be opened to deposit the charge of water quickly onto the fire. Thereafter the dump door will be reset in the closed and sealed position, for example by means of a fluid operated ram, ready for the aircraft to return to the body of water for replenishing the tank again.

There will be an inevitable sudden drag of the scoop as it contacts the water. In addition there will be a momentum drag resulting from the dynamic pumping of the water up the boom and indeed the mass of the boom itself will change when it fills with water. These effects will provide a reaction on the aircraft which produce potential pitching moments, making it difficult for the pilot to dip the scoop into the water with precision. In order to alleviate this problem, the centreline of the boom preferably passes substantially through the centre of gravity of the aircraft when the boom is in its lowered position.

In order to prevent the immersed scoop from twisting the boom when, for example, a cross wind causes the track of the aircraft over the water to be on a different bearing to the bearing defined by the longitudinal centreline of the aircraft, the scoop may be pivoted on the boom or the boom pivoted on the fuselage to allow the scoop to deviate from the bearing defined by the longitudinal centreline of the aircraft to adopt the bearing of the track of the aircraft over the water.

The boom may be telescopically extensible for water scooping and retractable for storage against the underside of the fuselage, but this is not usually necessary as it is acceptable for the rear end of the boom to project a little way behind the aircraft tail when stored for takeoff, normal flight or landing.

The boom may be lowered and raised by means of gravity and a controllable aerofoil mounted on the boom. However, it is preferable if the boom is lowered in a more controlled manner by the crew, for example utilizing a cable and winch or a ram. These devices can be arranged to limit the maximum degree to which the boom is lowered, for example at 45" to the horizontal when the aircraft is in level flight. However it is desirable if the support of the boom is slack in the sense that the boom can rise freely as a result of reaction with the water or flotsam on the water whereby any reactions on the aircraft producing pitching moments are transferred to the pivotal connection between the boom and the aircraft fuselage.

In order to ensure that the scoop dips into the surface of the body of water to an appropriate extent, the scoop may carry a fin, such as a triangular shaped vane or hydrofoil, which is inclined with a negative angle of attack to the water such that it draws the scoop down into the water. However, to prevent the fin causing the scoop to immerse itself beyond the point which brings the scoop into efficient contact with the water, the scoop is preferably provided, above the fin, with a curved shoe which is arranged to ride on the surface of the body of water like a waterski. The combined action of the fin and shoe then automatically control the depth of immersion of the scoop, provided that the aircraft is lower enough for the scoop to reach the surface of the water.

In order to avoid the scoop fouling driftwood or other flotsam on the surface of the body of water from which water is being scooped, a safety wire or the equivalent may be provided, extending upwards from a forwardly projecting portion of the scoop to a part of the boom. If the wire hits any flotsam, it will tend to bounce the boom backwards and upwards, so that the scoop rides over the obstruction, before dipping back into the water again.

It may be desirable to provide the aircrew with a warning that the aircraft is flying unnecessarily and dangerously low above the body of water during scooping. Such a warning may be dependent upon the angle at which the boom is currently making with the horizontal datum of the aircraft with the scoop dipping into the surface of the water. For example, if the angle reduces below a minimum acceptable angle, a visual or audible alarm may be sounded, such as upon operation of a microswitch.

It is desirable for there to be some means for indicating to the aircrew when the tank has been refilled. In the simplest form, this may comprise a window or sight glass associated with the tank, and any necessary illumination, so that the aircrew can monitor visually the level of water in the tank. It is also desirable for there to be some automatic means for avoiding overfilling and possibly bursting of the tank. This may comprise a blow off valve, and the squirt of water ejected by the valve may be in a position visible to the aircrew, thus also providing the indication that the tank is full. Alternatively, the tank may incorporate a valve, such as a conventional float operated valve, which closes when the level of water in the tank has risen to the necessary height. The valve will of course interrupt the flow of water along the duct from the scoop to the tank.

A different valve in the duct may be controlled by the aircrew for terminating the flow of water along the duct to the tank. The momentum drag on the aircraft, associated with accelerating the water, which has been scooped up, from rest to the aircraft speed, may be controlled by adjusting the partial closure of this valve to restrict the flow of water along the duct to a desired rate.

An example of an aircraft constructed in accordance with the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic side view showing the aircraft with its boom in the lowered position whilst flying closely above the surface of a body of water; Figure 2 is an enlarged side view of the aircraft of Figure 1 showing the general layout of the components used in scooping, storing and jettisoning the water; Figure 3 is an underneath plan view of the boom; Figure 4 is an enlarged side view of part of the scoop shown in Figure 2; Figure 5 is a section on the line V-V of Figure 4; Figure 6 is a section on the line VI-VI of Figure 4; Figure 7 is an enlarged side view of a flexible joint; and, Figure 8 is a plan view of the flexible joint of Figure 7.

The aircraft 1 shown in Figures 1 and 2 is converted from a light crop-spraying single piston-engined aircraft and it has a boom 2 mounted, at its front end, by pivotal connections 3 to the underside of its fuselage 4. As can clearly be seen in Figure 1, the centreline 5 of the boom 2 passes, when in its lowered position, through the average centre of gravity 6 of the aircraft 1 so that any forces acting along the length of the boom 2 do not produce any pitching moments. The boom 2 is raised and lowered by means of a winch 7 mounted within the fuselage 4 acting on a cable 8 attached adjacent to the midpoint of the boom 2 to thereby allow the boom 2 to be moved between the lowered position (see Figure 1) drawn in full lines and the raised position drawn in dash-dot lines.

The boom 2 has a tripod-like configuration and has three main tubular members, the side tubes 9 which are pivoted at their forward end to the underside of the fuselage 4 to form the pivotal connections 3 and a feed tube 10 which is in communication at the rearward end with the scoop 11 and at the forward end, via a flexible pipe 12 and inlet valve 13, with a water storage tank 14. This water storage tank 14 is provided with a dump door 15 pivoted at its forward end and openable under the control of a fluid operated ram 16 operated by the pilot so that any water in the reservoir 14 may be jettisoned.

It should be noted that the feed tube 10 serves a dual purpose since, apart from allowing water to be fed from the scoop 11 into the reservoir 14, it also acts as a main structural member of the boom 2, which is also provided with a number of cross tubes 17 and brace tubes 18 in order to improve its rigidity.

Referring to Figures 4, 5 and 6, the scoop 11 has a main tube 19 shaped like a shepherd's crook which is connected at its forward end, via a flexible coupling 20 (shown in Figure 2), to the feed tube 10 of the boom 2.

The rearward part of the tube 19 is curved so that the rearward end, on which a nozzle 21 is mounted, faces, when the boom 2 is lowered in the water, the oncoming flow of water, some of which is collected by the nozzle 21. The curved rearward part of the scoop 11 is strengthened by a substantially Vshaped plate 22 fixed to the inside of the curve. This plate 22 presents a substantially blunt (see Figure 5) leading edge over most of its length but, at the base of the V, the leading edge (see Figure 6) has been sharpened to form a knife portion 22 capable of breaking up some of the flotsam which works its way into the base of the V. In order to help deflect water past the tube 19, two substantially semicircular shaped plates 24 are fixed one on each side of the rearward part of the plate 22.

In order that the scoop 11, when immersed, may be allowed to deviate from the bearing defined by the longitudinal centreline of the aircraft 1 to adopt the bearing of the track of the aircraft 1 over the water to reduce the sideways moment applied to the aircraft 1 by the boom 2, the scoop 11 is mounted on the boom 2 via the flexible coupling 20 whose pivotal axis is substantially perpendicular to the centreline 5 of the boom 2 and passes through the centreline of the aircraft 1. As shown in Figure 7 and 8, the flexible connection 20 comprises two flange plates 25 mounted one each on the rearward ends of the tubes 9 and 10 of the boom 2 and the forward end of the tube 19 of the scoop 11.

The feed tube 10 and the tube 19 project through their respective flanges 25 into the gap 26 separating the flanges and their adjacent ends are connected via a flexible pipe 27 which may be moulded from Flexane. The flanges 25 are held apart from one another and allowed to pivot relative to one another by means of plates 28 projecting from the boom 2 side of the coupling being pivotally connected via threaded fasteners 29 to flanges 30 projecting from the scoop 11 side of the coupling. The coupling 20 is self-centering as a result of the threaded rods 31 and springs 32 mounted on and between the flanges 25.

Allthough it is not shown in the drawings, a safety wire may be strung between the flange 30 on the scoop 11 side of the flexible connection 20 and a lug 33 (see Figure 4) fixed to the top of the intake nozzle 21 in order that, if this wire hits some flotsam, the boom 2 will ride up and over it.

Normally, the boom 2 is only lowered by the winch 7 when it is desired to scoop up some water in order to refill the reservoir tank 14. When it is desired to achieve this, the aircraft 1 is flown with its wheels 34 a height of approximately ten feet above the surface 35 of a body of water 36, (see Figure 1, in which this height is denoted by the letter H).

At the height H, the centreline 5 of the boom 2 subtends an angle A which is approximately equal to 45 with the surface 35. The forward motion of the aircraft 1 relative to the water 36 forces water into the nozzle 21, along the tube 19, through the flexible coupling 20, along the feed tube 10, through the flexible tube 12 and the inlet valve 13 and into the reservoir 14. Once sufficient water has entered the reservoir 14, the inlet valve 13 will close and the pilot should then operate the winch 7 to raise the boom 2 prior to travelling to a site upon which water is to be dropped.

Upon reaching this site, the pilot activates the fluid operated ram 16 to open the dump door 15, upon which opening, the water within the tank 14 is jettisoned. The pilot may then return to the body of water 36 in order to repeat the whole process.

Our preliminary calculations show that starting the scoop at a speed of about 125 knots and with the speed eroding to about 90 knots, approximately two tons of water (400 gallons) can be uplifted in a matter of 45 seconds, assuming a forward pointing nozzle in the scoop with a diameter of substantially 34 mm.

Claims (13)

1. An aircraft comprising a fuselage which contains a water storage tank provided with a dump door; a rearwardly extending boom which is pivoted at its forward end to the underside of the fuselage and which carries at its rear end a scoop connected via a duct in the boom to the tank; and means for lowering the rear end of the boom; whereby the tank may be replenished by flying the aircraft closely above the surface of a body of water with the scoop dipping into the water.

2. An aircraft according to claim 1, in which the centreline of the boom passes substantially through the centre of gravity of the aircraft when the boom is in its lowered position.

3. An aircraft according to claim 1 or claim 2, in which the scoop is pivoted on the boom or the boom pivoted on the fuselage to allow the scoop to deviate from the bearing defined by the longitudinal centreline of the aircraft to adopt the bearing of the track of the aircraft over the water.

4. An aircraft according to any of the preceding claims, in which the boom is telescopically extensible for water scooping and retractable for storage against the underside of the fuselage.

5. An aircraft according to any of the preceding claims, in which the boom is lowered and raised by means of gravity and a controllable aerofoil mounted on the boom.

6. An aircraft according to any of claims 1 to 4, in which the boom is lowered by a cable and winch or a ram.

7. An aircraft according to any of the preceding claims, in which the scoop carries a fin which is inclined with a negative angle of attack to the water such that it draws the scoop down into the water.

8. An aircraft according to claim 7, in which the scoop is provided, above the fin, with a curved shoe which is arranged to ride on the surface of the body of water like a waterski.

9. An aircraft according to any one of the preceding claims, in which a safety wire or the equivalent is provided, extending upwards from a forwardly projecting portion of the scoop to a part of the boom.

10. An aircraft according to any of the preceding claims, in which a visual or audible alarm is sounded if the angle at which the boom is currently making with the horizontal datum of the aircraft with the scoop dipping into the surface of the water reduces below a minimum angle.

11. An aircraft according to any of the preceding claims, in which the water storage tank is provided with a blow off valve positioned so as to be visible to the aircrew, whereby, upon the tank having been refilled, a squirt of water is ejected by the valve.

12. An aircraft according to any of the preceding claims, in which a valve controllable by the aircrew is provided in the duct to enable the flow of water along the duct to be restricted to a desired rate by adjusting the partial closure of the valve.

13. An aircraft substantially as described with reference to the accompanying drawings.