Compound helicopter and powerplant therefor

[54] COMPOUND HELICOPTER AND POWERPLANT THEREFOR

[75] Inventor: John D. Sibley, Watford, England

[73] Assignee: Rolls-Royce Limited, London, England

[21] Appl. No.: 632,825

[22] Filed: Jul. 20, 1984

[30] Foreign Application Priority Data

Jul. 22, 1983 [GB] United Kingdom 8319783

[51] Int. Q." B64C 21/04; B64C 27/26

[52] U.S. CI 244/12.5; 244/6;

244/207; 244/23 D

[58] Field of Search 244/207, 213, 212, 215,

244/216, 217, 23 D, 12.5, 110 B, 6, 7 R

[56] References Cited

U.S. PATENT DOCUMENTS

2,940,691 6/1960 David .

3,332,644 7/1967 Whittley .

3,368,778 2/1968 Wilde et al 244/6

3,375,997 4/1968 Gist, Jr. .

3,432,123 3/1969 Conway et al. .

3,442,470 5/1969 Farbridge et al 244/217

3,478,988 11/1969 Roed 244/216

3,503,572 3/1970 Hafner 244/7 R

3,678,690 7/1972 Shoket et al. .

3,721,406 3/1973 Hurlbert 244/217

3,776,491 12/1973 Oulton 244/213

3,884,433 5/1975 Alexander 244/207

4,044,971 8/1977 Pharris .

4,175,385 11/1979 Nash 244/12.5

FOREIGN PATENT DOCUMENTS

81338 7/1963 France .

980608 1/1965 United Kingdom .

1024969 4/1966 United Kingdom .

1079296 8/1967 United Kingdom .

1108454 3/1968 United Kingdom .

1120658 7/1968 United Kingdom .

Primary Examiner—Galen Barefoot
Attorney, Agent, or Firm—Parkhurst & Oliff

[57] ABSTRACT

A compound helicopter shown in FIG. 1 of the drawings has wings 12 in addition to a helicopter rotor 14 and has twin powerplants 16 each including a low pressure compressor 18, a gas generator 20, a power turbine 22 driven by the gas generator and connected through a gearbox 32 to drive the helicopter rotor, and a variable area final propulsion nozzle 24 which receives the exhaust from the power turbine. Augmentor wing flaps 28 are provided on the wings and fed with air from the low pressure compressor for providing additional lift and thrust from the wings. The flaps 28 are pivotally mounted on the trailing edge of the wing and are movable to a position where the trailing edges of the flaps 28 obturate the flow through the gap between the flaps 28. In this position the flaps provide a means of decelerating the forward speed of the aircraft.

8 Claims, 3 Drawing Figures

COMPOUND HELICOPTER AND POWERPLANT
THEREFOR

BACKGROUND AND SUMMARY OF THE 5
INVENTION

This invention relates to aircraft which can take-off and land vertically (VTOL aircraft) and aircraft having a short take-off and landing capability (STOL aircraft). The invention is particularly concerned with VTOL and STOL aircraft that are also equipped with a lift augmented wing (hereinafter called an augmentor wing).

By "augmentor wing" it is meant a wing of the type J5 in which pressurised air is blown through openings in the wing to induce an air flow over the lift developing surfaces of the wing. The air which is induced to flow over the wing augments the lift and such a wing is useful when the forward speed of the aircraft is low. 2Q

A well known example of a fixed wing aircraft having an augmentor wing is the De Havilland of Canada aircraft known as the Buffalo.

The present invention is relevant to a fixed wing aircraft or to helicopters 25

In our co-pending British Patent Application No. 8234318 there is disclosed a helicopter which includes a gas turbine engine having a core gas generator, a power turbine driven by the exhaust of the gas generator and connected to drive the helicopter main lifting rotor, and 30 a variable area final propulsion nozzle for controlling the power to the rotor. This application corresponds to U.S. patent application Ser. No. 555,090, filed Nov. 25, 1983. A compressor of the engine is used to supply pressurised air to an augmentor wing. By varying the 35 area of the propulsion nozzle, it is possible to reduce the power to the main lifting rotor and simultaneously increase the forward thrust which is developed by the engine as a turbo jet reaction. Hence it will be possible to achieve very high forward speeds than currently 40 attainable and operate the helicopter in a mode where the main lift is developed by the wings and not by the lifting rotor.

One of the problems envisaged with such a compound helicopter is that of decelerating the forward 45 speed of the helicopter. At very high speeds it will be impractical to tilt the rotor or pitch the nose of the helicopter upwards in the conventional way because the aerodynamic loads on the main lifting rotor would be too high. In any case, even at lower speeds, when the 50 majority of lift is taken by the main rotor, it would be undesirable to pitch the nose of the helicopter upwards. To do so would expose the underside of the helicopter to the ground fire of an enemy position and obscure the pilot's view of the enemy positions. The pilot would 55 also be unable to aim his armaments at the enemy ground positions until a horizontal attitude had been regained.

There is, therefore, a need to be able to decelerate the helicopter without having to rely on conventional 60 methods and at the same time enable the helicopter to assume a level attitude.

Although the primary object is to provide a means of decelerating helicopters that are equipped with a blown augmentor wing, it is also relevant to decelerating fixed 65 wing aircraft which have an augmentor wing.

The invention as claimed uses the flaps that are provided as part of the augmentor wing and enables these

flaps to be moved into the ambient airstream and thereby decelerate the aircraft.

BRIEF DESCRIPTION OF THE DRAWINGS

An example of the invention will now be more particularly described with reference to the accompanying drawings in which:

FIG. 1 shows the top part of a twin-engined compound helicopter of the invention with its helicopter rotor, augmentor wing, and gas turbine engine power plants.

FIG. 2 is a view on arrow A of FIG. 1, and,

FIG. 3 depicts a further embodiment of the invention.

DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENTS

Referring now to the drawings, there is shown a compound helicopter 10 having wings 12, one on each side, and a helicopter rotor 14. Two gas turbine engine powerplants 16 are provided each having a low pressure compressor 18, a core gas generator 20 which drives the low pressure compressor, a power turbine 22 which is driven from the exhaust of the core engine, and a variable area final nozzle 24.

The arrangement of the parts of each of the powerplants are as follows: At least a part of the air flow compressed by each core engine is passed to the wings 12 via ducting 26, and the wings have augmentor flaps 28 at the trailing edges thereof. The augmentor wing is known per se and its operation is not described here in detail. It is sufficient to say that the air from the ducting 26 passes to atmosphere through the flaps 28 and induces air flowing over the aircraft wing to pass between the flaps and to stick to the top flap to increase the wing lift. The flaps 28 are also pivotable between the position shown in full lines, which provides additional downwardly directed thrust to add to the lift generated by the rotor 14, and the position shown in dotted lines which provides forward thrust. The compressed air from the two engines is supplied to opposite sides of a diaphragm 27 which divides the ducting 26 longitudinally. Thus both engines supply air to the flaps 28 along the whole length of the wing and, failure of one engine will not affect the flow from the other one. The core gas generator 20 produces power to drive the compressor 18, and the exhaust from the gas generator passes through the power turbine 22. A shaft 30 and gearbox 32 interconnect both of the power turbines 22 with the helicopter rotor 14 to drive the rotor. The exhaust from each of the power turbines passes to atmosphere through the variable area final nozzle, which, in this example, is shown pointing rearwards all of the time, but which could, if desired, be vectorable to direct the exhaust gases downwardly, for increasing lift, or sideways for attitude control.

The operation of the compound helicopter is as follows:

For take-off each of the gas turbine powerplants is run at maximum power with the variable area final nozzle in its maximum area position. This provides the greatest pressure drop across the power turbine and hence maximum drive to the rotor 14 which generates most of the lift, and minimum propulsive thrust from the final nozzle. Additional lift is generated by the compressed air from the low pressure compressor passing through the augmentor flaps 28 which are pivoted to direct the air downwardly. Thus, the helicopter can take off vertically with only a very minor part of the