GB2082519A - Agricultural aircraft - Google Patents

Abstract

An agricultural aircraft has control ailerons (12) and, along the full length of the trailing edge of each wing, a number of auxiliary airfoil flaps (13). The flaps incorporate internal ducts (14, 15) through which material to be sprayed is supplied from a hopper (8) to branch ducts (16) and spray nozzles (17). Spoilers may be used instead of ailerons. A centrifugal pump in the hopper (8) feeds the ducts (14, 15). <IMAGE>

Description

SPECIFICATION Agricultural aircraft The invention relates to agricultural aircraft, by which is meant aircraft fitted with a reservoir for liquid or particulate material and a spraying system for spraying the material downwards from the aircraft in flight. Such aircraft are primarily used for spraying and top dressing crops or ground under cultivation with, for example, pesticides and fertilizers, but may obviously also be used for other purposes, such as the spraying of oil polluted water with an oil dispersing agent.

The spraying system normally involves a fixed boom extending along beneath each wing and provided with longitudinally spaced spray devices, such as nozzles or rotary atomizers. Material is supplied to the booms from a reservoir and discharged downwards from the devices.

The provision of the external booms adds to the drag of the aircraft which results in a requirement for more power and an increased fuel consumption of the aircraft engine. The arrangement also suffers from the disadvantage that it is desirable to broadcast the sprayed material into a downwardly directed air flow or "downwash" from the aircraft wings, to control the distribution of the sprayed material, particularly its penetration into crops being sprayed. This downwash has previously been produced by flying the aircraft in a nose up attitude so that the wings present a high angle of attack but the nose can then obscure the pilot's vision which is dangerous as the aircraft will usually be flying closely above the ground.

It has previously been proposed to incorporate the booms, which carry the material from the reservoir to the spray devices within airfoil flaps pivotally mounted at the trailing edge of the wing. This overcomes to some extent the problem of drag but in practice restricts the broadcasting of the material to the inboard portions of the wing. This is because the trailing flap sections at the outboard portions of the wings act as ailerons which must be quickly and differentially movable to provide lateral stability of the aircraft. It is unlikely that an air worthiness certificate would be obtainable if these outboard aileron flaps incorporated any part of the booms as the booms could well incorporate at any time an uncertain mass of the spray material and this would prevent the necessary precise static balancing necessary to avoid unacceptable flutter of the ailerons.

In accordance with the present invention, an agricultural aircraft has wings provided with readily reversibly movable control surfaces positioned adjacent to the outboard ends of the trailing edges of the wings for lateral control of the aircraft, and with auxiliary airfoil flaps extending substantially fully along the trailing edges of the wings behind the control surfaces; and a spraying system incorporating ducts which extend along within the flaps and are connected to a material reservoir and to spray devices which project from the flaps.

With this construction the control surfaces, which may be spoiler surfaces on the wings, or ailerons let into recesses in the trailing edges of the wings adjacent to their outboard ends, may be precisely balanced statically, thereby avoiding any danger of flutter. The auxiliary airfoil flaps, which will usually be irreversibly movable, that is to say only slowly extendable or retractable via gearing such as worm gearing, will provide variable lift. As these flaps are not required for lateral control, they can then extend along the full length of each wing, incorporating the spraying system ducts and thus enabling the material to be broadcast of the full wing span. The internal ducts, which replace the conventional external booms, provide no drag other than the small component provided by the projecting spray devices.The spray devices, which will normally project from the flaps on stalks spaced along the flaps, therefore follow the movement of the flaps and, at any tilted position of the flaps, will broadcast the sprayed material close to the flaps in the air flow passing over and under the flaps and the direction of which is closely dictated by the attitude of the flaps.

During spraying the flaps will be tilted to a downwardly drooping position to provide extra lift so that the aircraft can be flown at low speed with the cockpit in a substantially horizontal attitude in which the pilot has good visibility. In this position the flaps will provide a significant downwash to carry the sprayed material downwards in a controlled fashion.

The ducts of the spraying system may be stainless steel tubes along which the material, particularly in liquid form, is pumped from the reservoir. The nozzles, rotary atomizers or other spray device can readily be positioned in relationship with the flaps so that the spray discharged will not impinge upon the flaps but will generally follow the line of airflow around the flaps.

An example of an aircraft constructed in accordance with the present invention is illustrated in the accompanying drawings, in which: Figure 1 is a front elevation; Figure 2 is a side elevation; Figure 3 is a plan; Figure 4 is an underneath plan of part of one auxiliary airfoil flap; Figure 5 is a section taken on the line V-V in Fig. 4; and Figure 6 is a diagrammatic perspective view of a hopper at the inner end of the port wing.

The illustrated aircraft has a fuselage 7 incorporating an integral hopper 8, which forms the subject of our copending Application 8126014 of even date, reference GJE5079/058, an engine 7, a cockpit 10, and wings 11 each incorporating at its outboard end a pair of ailerons 1 2 and four auxiliary airfoil flaps 1 3 extending along the full length of the trailing edge of the wing behind the ailerons 12.

As shown in Fig. 3, the flaps of each wing incorporate two supply ducts 1 4 and 1 5 which are provided with branches 1 6 terminating at their rear ends in spray nozzles 1 7.

The duct 1 4 supplies nozzles at the outboard half of the wing and duct 1 5 the nozzles at the inboard half of the wing.

The spray ducts and nozzles are shown more clearly in Figs. 4 and 5. Each flap has a longitudinal cavity 1 8 of substantially trapezium-shaped section, closed at the bottom of the flap by a hinged door 1 9 which, for clarity, is omitted in Fig. 4. The main supply ducts 14 and 1 5 are pipes accommodated in the cavity 1 8. The branch ducts 1 6 are pipes extending from the respective pipes 14 or 1 5 rearwardly from the cavity 1 8 through shaped portions 20 of the door 19, and beneath the flap to which they are supported by straps 21.

The lengths of pipe 1 4 and/or 1 5 in each flap are rigid and are connected end to end with a corresponding pipe sections in the adjacent flap via flexible sleeves which allows the composite pipes 14 and 1 5 to follow the wing flexure. At the inner end of each wing, the pipes 1 4 and 1 5 are connected via flexible hoses 22 to a Y coupling 23 which supplies the spray nozzles of both wings from a common centrifugal spray pump 24 at an outlet from the hopper.

The number of nozzles may be increased by replacing a nozzle 1 7 by a T-piece and connections to two further nozzles.

The ailerons 1 2 are quickly and differentially adjustable for flight control. In contrast all the flaps 1 3 are raised and lowered slowly together, carrying the spray pipes and nozzles with them so that the spray material is always broadcast in the air flow passing closing beneath the flaps. The movement of the pipes 14 and 1 5 with the flaps, relatively to the hopper 8, is accommodated by the flexible hoses 22.

Claims (4)

1. An agricultural aircraft having wings provided with readily reversibly movable control surfaces positioned adjacent to the outboard ends of the trailing edges of the wings for lateral control of the aircraft, and with auxiliary airfoil flaps extending substantially fully along the trailing edges of the wings behind the control surfaces; and a spraying system incorporating ducts which extend along within the flaps and are connected to a material reservoir and to spray devices which project from the flaps.

2. An aircraft according to claim 1, in which the control surfaces are ailerons let into recesses in the trailing edges of the wings adjacent to their outboard ends.

3. An aircraft according to claim 1 or claim 2, in which the spray devices comprise branch ducts extending from the ducts within the flaps rearwardly below the flaps and terminating in spray nozzles.

4. An aircraft according to claim 1 substantially as described with reference to the accompanying drawings.