GB2263675A

GB2263675A - Propulsion system for braking aircraft.

Info

Publication number: GB2263675A
Application number: GB9226405A
Authority: GB
Inventors: Andrew Charles Pickard; Edward Stafford Hadaway
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1992-01-28
Filing date: 1992-12-18
Publication date: 1993-08-04
Also published as: GB9226405D0; GB9201768D0

Abstract

A propulsion system for an aircraft 10 comprises a plurality of main propulsion engines 14 which are mounted on the wings 16 of the aircraft 10 and which in operation provide a thrust to propel the aircraft 10 forward. An at least one further power plant, 18 (or 24), facilitates braking of the aircraft 10 and is mounted on the aircraft fuselage 12 remote from the main propulsion engines 14 in such a way as to cause insignificant drag during cruise. Use of additional power plants 18 (24), remote from the main propulsion engines 14, to provide the thrust necessary to effect braking of the aircraft 10 eliminates the need to provide thrust reversers on the main propulsion engines 14. This eliminates constraints imposed on the design of the engine and cowling of the main propulsion engines 14. The additional power plants may be rocket motors or gas turbine engines. The additional power plants 18 may be mounted on the inner face of rear fuselage doors 20 which, when extended to allow operation of the power plants, themselves form air brakes. Power plants (24) may serve as auxiliary power units and may selectively provide forward thrust for propulsion or reverse thrust for braking. <IMAGE>

Description

PROPULSION SYSTEM FOR BRAKING AIRCRAFT The present invention relates to a propulsion system for an aircraft and in particular to an arrangement of power plants mounted on an aircraft to effect braking of the aircraft.

On conventional aircraft a proportion of the braking is achieved by reversing the thrust from the engines which propel the aircraft forwards. Thrust reversal is effected by the provision of doors pivotally mounted to the engine cowling. During normal operation when the aircraft is being propelled forward the thrust reverser doors are in the stowed position and form an continuation of the engine cowling and do not impede the engine efflux. When thrust reversal is required the doors are displaced so that they obstruct the engine efflux and divert it forwards to effect braking of the aircraft.

A problem with providing thrust reversers on the main propulsion engines is the additional drag caused by the doors when in the stowed position during normal operation.

Further the provision of the thrust reverser as an integral part of the engine leads to constraints being imposed on the engine and cowling design.

The present invention seeks to provide a braking system on an aircraft in which the aforementioned problems are minimised.

According to the present invention a propulsion system mounted on an aircraft to effect braking of the aircraft comprises an at least one main power plant mounted from the aircraft which in operation provides a thrust to propel the aircraft forward and an at least one further power plant mounted on the aircraft remote from the at least one main power plant, the at least one further power plant in operation providing a thrust to facilitate braking of the aircraft.

In one embodiment of the present invention the at least one further power plant is mounted on an at least one door provided in the aircraft fuselage which pivots away from the aircraft fuselage to expose the at least one further engine when braking of the aircraft is required, pivoting of the at least one door increases the drag and provides a further braking force on the aircraft.

Preferably the at least one further power plant is mounted in the fuselage at the tail of the aircraft.

In a second embodiment of the present invention the at least one further power plant provides a thrust, in addition to the thrust provided by the main propulsion engine, which propels the aircraft forwards, means being provided to redirect the thrust when braking of the aircraft is required.

The means for redirecting the thrust from the at least one further power plant to effect braking of the aircraft comprises a plurality of doors mounted on the tail fuselage of the aircraft adjacent the at least one further power plant, the doors in normal operation form an extension of the tail fuselage and are displaced to redirect the thrust of the at least one further power plant when braking of the aircraft is required.

Alternatively the means for redirecting the thrust from the at least one further power plant to effect braking of the aircraft comprises ducting in the tail fuselage of the aircraft through which efflux from the at least one further power plant is selectively directed to exhaust forward of the at least one further power plant when braking of the aircraft is required.

The at least one further power plant may provide electrical and mechanical power and cabin air to the aircraft.

The main propulsion power plant may be a gas turbine engine and the at least one further power plant may be a rocket engine.

The present invention will now be described with reference to the accompanying drawing in which, Figure 1 is a pictorial view of an aircraft provided with a propulsion system in accordance with one embodiment of the present invention.

Figure 2 is a pictorial view of the tail fuselage of the aircraft shown in figure 1.

Figure 3 is an view along arrow A in figure 2 when braking of the aircraft is effected.

Figure 4 is a pictorial view of the tail fuselage of an aircraft provided with a propulsion system in accordance with a second embodiment of the present invention.

Figure 5 is a view along arrow B in figure 4 when braking of the aircraft is effected, the actuation mechanism is not shown in the interest of clarity.

Referring to figure 1 an aircraft, generally indicated at 10, has a propulsion system mounted from the aircraft. The propulsion system comprises two power plants 14, which are preferably gas turbine engines, mounted on the wings 16 of the aircraft 10. The gas turbine engines 14 provide the thrust which propel the aircraft 10 forward. Two further power plants 18, which may be motors, rockets, gas turbine engines or any combination of these, are mounted on the fuselage 12 at the rear of the aircraft 10 and provide a thrust which effects braking of the aircraft 10.

The power plants 18 are mounted on the inner surface 19 of doors 20 which are pivotally connected to the rear of the aircraft fuselage 12. In normal operation, when the aircraft 10 is being propelled forwards by the gas turbine engines 14 mounted on the wings 16, the doors 20 are in their stowed position and the power plants 18 are concealed within the aircraft fuselage 12. In the stowed position the doors 20 form an extension of the aircraft fuselage 12, figure 2.

When braking of the aircraft 10 is required the doors 20 pivot outwardly, away from the fuselage 12 of the aircraft 10 to the position shown in figure 3. Pivotable movement of the doors 20 is initiated by an actuation system, not shown, which may be for example a ram mechanism or any other form of well known actuation system.

The power plants 18, mounted on the inner surface 19 of the doors 20, are revealed when the doors 20 are deployed. The efflux from the power plants 18 is directed forward to provide a thrust on the aircraft 10 which effects braking of the aircraft 10. When the doors 20 are deployed they produce an additional drag and act as an air brake which assists in the braking of the aircraft 10.

Figure 4 shows a further embodiment of the present invention in which the same reference numerals have been used for integers which are common to all the embodiments of the present invention. The propulsion system of the aircraft 10 comprises two gas turbine engines 14 mounted on the wings 16 of the aircraft (not shown) and which propel the aircraft 10 forwards. A further gas turbine engine 24 is mounted in the tail fuselage 22 of the aircraft 10 and provides electrical and hydraulic power as well as cabin air at all times or when the main engines 14 are not operational. Doors 26 are pivotally mounted on the tail fuselage 22 adjacent the gas turbine engine 24.

In normal operation when the aircraft 10 is being propelled forward the doors 26 in the aircraft fuselage 12 are in the stowed position and form an extension of the aircraft tail fuselage. When braking of the aircraft 10 is required the doors 26 are pivoted to direct the efflux from the engine 24 forwards. This provides a thrust to effect braking of the aircraft 10.

Pivotable movement of the doors 26 is initiated by an actuation system, not shown, which may be for example a ram mechanism or any other form of known actuation system.

It will be appreciated by one skilled in the art that rather than employing doors 26 in the tail 22 of the aircraft fuselage 12 to direct the efflux of the engine 24 forwards ducting which extends forward of the engine 24 could be used. The efflux of the engine 24 would be selectively directed through the ducting when thrust reversal is required by for example a valve mechanism.

By using additional power plants 18 and 24, which are mounted on the aircraft fuselage 12 remote from the main propulsion engines 14, to provide the thrust necessary to effect braking of the aircraft 10 there is no need to provide thrust reversers on the main propulsion engines 14. By eliminating the need to provide a thrust reverser integral with the main propulsion engine 14 any design constraints are removed.

Claims

Claims:

1. A propulsion system mounted on the fuselage of an aircraft to effect braking of the aircraft comprising an at least one main power plant mounted from the aircraft which in operation provides a thrust to propel the aircraft forward and an at least one further power plant mounted on aircraft remote from the at least one main power plant, which in operation provides a thrust to facilitate braking of the aircraft.

2. A propulsion system as claimed in claim 1 in which the at least one further power plant is mounted on an at least one door provided in the aircraft fuselage which pivots away from the aircraft fuselage to expose the at least one further engine when braking of the aircraft is required, pivoting of the at least one door increases the drag and provides a further braking force on the aircraft.

3. A propulsion system as claimed in claim 1 or claim 2 in which the at least one further power plant is mounted in the fuselage at the tail of the aircraft.

4. A propulsion system as claimed in claim 1 in which the at least one further power plant provides a thrust, in addition to the thrust provided by the main propulsion engines which propels the aircraft forward, means being provided to redirect the thrust of the at least one further power plant when braking of the aircraft is required.

5. A propulsion system as claimed in claim 4 in which the means for redirecting the thrust from the at least one further power plant comprises a plurality of doors mounted on the tail fuselage of the aircraft adjacent the at least one further power plant, the doors in normal operation form an extension of the tail fuselage and are displaced to redirect the thrust of the at least one further power plant when braking of the aircraft is required.

6. A propulsion system as claimed in claim 4 in which the means for redirecting the thrust from the at least one further power plant comprises ducting in the fuselage of the aircraft through which efflux from the at least one further power plant is selectively directed to exhaust forward of the at least one further power plant when braking of the aircraft is required.

7. A propulsion system as claimed in any preceding claim in which the at least one further power plant provides electrical and mechanical power and cabin air to the aircraft.

8. A propulsion system as claimed in any preceding claim in which the main propulsion power plant is a gas turbine engine.

9. A propulsion system as claimed in any preceding claim in which the at least one further power plant is a rocket engine.

10. A propulsion system as hereinbefore described with reference to and as shown in the accompanying drawings.