GB2257477A

GB2257477A - Auxiliary power equipment

Info

Publication number: GB2257477A
Application number: GB9114895A
Authority: GB
Inventors: Ian Robert Bennett
Original assignee: Smiths Aerospace Gloucester Ltd
Current assignee: Smiths Aerospace Gloucester Ltd
Priority date: 1991-07-10
Filing date: 1991-07-10
Publication date: 1993-01-13
Anticipated expiration: 2011-07-10
Also published as: GB2257477B; GB9114895D0

Abstract

A ram air turbine (2) is deployable in an emergency from a stowed position within an aircraft fuselage (5) into the slipstream. The rotary motion is passed by a gear train (11, 12, 13, 14, 15, 16, 17) to a hydraulic pump (6) to generate hydraulic power for control the aircraft. The RAT (2) has a single blade (8) balanced by a counterweight (9) making the equipment more compact than multi-bladed arrangements. In another arrangement the turbine has two blades wherein one blade is longer than the other. <IMAGE>

Description

AUXILIARY POWER EQUIPMENT This invention relates to auxiliary power equipment for use on aircraft.

US 4676458 discloses auxiliary power equipment which comprises a power unit deployable from a stowed position, in which it is shielded from the airflow, to a deployed position in which it is exposed to the airflow. The space available on aircraft for carrying equipment is limited and present auxiliary power equipment is bulky. It is an object of the present invention to provide auxiliary power equipment which is more compact.

Accordingly, the present invention provides auxiliary power equipment characterised in that the power unit has a single blade rotor.

By providing the power unit with a single blade rotor, the auxiliary power equipment is more compact than conventional multi-bladed arrangements. Whilst to maintain the power output it may be necessary to have a blade which is slightly larger than blades of conventional arrangements, the blade does not have to be twice as long. The space saving is thus potentially considerable. It will be appreciated that the same advantage will be achieved by using more than one blade, one blade being made shorter than the other. The rotor may be a turbine designed to be driven by the airflow or a propeller designed to be driven to produce thrust.

The power unit may be an internal combustion engine or electric motor to give propulsive force, for example, in a glider, or may be a unit such as a ram air turbine (RAT) designed to be used in conjunction with a power generator to generate electrical or hydraulic power as the airflow drives the rotor.

In order to reduce undesirable vibrations as the single blade rotor rotates, preferably, the propeller includes a blade counterweight and balance weight is included.

Preferably, the blade is rotatably mounted about an axis substantially parallel to the length of the blade to permit the pitch of the blade to be varied according to give the required power output.

The pitch may be changed to be coarser or finer as required but where the power unit is designed to generate power from the airflow, preferably, the pitch will be made coarser to prevent damage due to overspeeding.

Conveniently, the counterweight may be mounted diametrically opposite the blade and preferably, in order to give a more direct load path, the counterweight will be mounted about an end of an extension of a shank of the blade.

A specific embodiment will now be described, by way of example only, with reference to the drawings in which: Figure 1 is a side view of auxiliary power equipment in accordance with the invention in stowed and deployed positions; and Figure 2 is a frontal view of part of the equipment shown in Figure 1.

With reference to Figure 1, there is shown auxiliary power equipment 1 comprising a ram air turbine (RAT) 2 rotatably mounted to a strut 3.

The strut 3 is pivotably mounted by a pivot 4 to an aircraft fuselage 5. Fixed to the upper end of the strut 3 is a hydraulic pump 6.

The RAT 2 comprises three major components a hub 7, a single blade 8 and associated counterweight 9. The counterweight 9 is located on an extension of a shank 10 of the blade 8 to give a direct load path. The rotation of the RAT 2 is transmitted to the pump 6 by means of a drive train located within the strut 3 comprising an RAT Stub Shaft 11, intermeshing bevel gears 12 and 13, drive shaft 14, intermeshing bevel gears 15 and 16 and pump stub shaft 17. Hydraulic fluid flow is coupled into and out of the pump 6 by means of hydraulic fluid swivel couplings 18, 19 and 20 in a manner well known.

In the event of an emergency, such as an engine failure, the auxiliary power equipment is deployed from a compartment 21 in the fuselage 5 through a hatch 22 by an ejector jack 23. The deployment may be made under manual or automatic command.

Under the action of the ejector jack 23, the auxiliary power equipment swings about the pivot point 4 in an arc 24 from the stowed position to the deployed position in which the RAT 2 is exposed to the airflow past the fuselage 5. The airflow acts upon the blade 8 to rotate the RAT 2 and the motion is passed via the drive train to the hydraulic pump 6 where it is converted to hydraulic power. The power is coupled to the aircraft system by the swivel couplings 18, 19 and 20 and used to control the aircraft for the duration of the emergency.

In order to prevent overspeeding of the RAT 2, the pitch is controlled by a pitch control mechanism which is housed in the strut 3 (not shown). The counterweight mass distribution is used to compensate for the blade mass distribution and thus reduce centrifugal twisting moments on the blade assembly, hence reducing control forces required.

To stow the equipment 1, the RAT 2 is stopped, in a manner well known, with the blade 8 extending in the direction of the strut 3. The ejector jack 23 is then actuated to swing the strut 3 forwards and upwards until the equipment is within the compartment 21. The hatch 22 is then reclosed.

Since the blade 8 is aligned with the strut 3 and there is no second blade extending from the hub 7 the equipment 1 occupies less space than conventional arrangements In alternative embodiments of the invention the hydraulic pump may be located in different positions for instance it may be incorporated into the strut, fuselage or RAT. Where it is desired to generate electrical rather than hydraulic power the pump may be replaced with an electrical generator or, where both types of power are required, both a pump and electrical generator may be driven.

Claims

1. Auxiliary power equipment for use on an aircraft comprising a power unit deployable from a stowed position, in which it is shielded from the airflow about the aircraft, and a deployed position in which it is exposed to the airflow characterised in that the power unit has a single blade rotor.

2. Equipment as claimed in claim 1 wherein the power unit is a ram air turbine.

3. Equipment as claimed in claim 2 wherein the ram air turbine drives a power generator.

4. Equipment as claimed in claim 1 wherein the power unit is a motor unit to provide propulsive force for the aircraft.

5. Equipment as claimed in any preceding claim wherein the blade is rotatably mounted about an axis substantially parallel to the length of the blade to vary its pitch.

6. Equipment as claimed in any preceding claim wherein the propeller includes a blade counterweight.

7. Equipment as claimed in claim 6 wherein the counterweight is located diametrically opposite the blade.

8. Equipment as claimed in claim 7 wherein the counterweight is fixed to an extension of a shank of the blade.

9. Equipment as claimed in any preceding claim wherein the counterweight has a mass distribution to produce a blade pitch changing force when the equipment rotates.

10. Equipment as claimed in claim 9 wherein the force acts to rotate the blade to a coarser pitch.

11. Auxiliary power equipment substantially as hereinbefore described with reference to the drawings.

12. Auxiliary power equipment comprising a power unit deployable from a stowed position, in which it is shielded from the airflow about the aircraft, and a deployed position in which it is exposed to the airflow characterised in that the power unit has a rotor having two blades one blade being longer than the other.

Amendments to the claims have been filed as follows 1. Auxiliary power equipment for use on an aircraft comprising a power unit deployable from a stowed position, in which it is shielded from the airflow about the aircraft, and a deployed position in which it is exposed to the airflow characterised in that the power unit has a single blade rotor or a rotor having at least two blades one blade being longer than the other.

2. Equipment as claimed in claim 1 wherein the power unit is a ram air turbine.