GB2146603A - Auxiliary wings for rotary-winged aircraft - Google Patents

Abstract

Cantilever aerofoil shaped abutments for rotary winged aircraft which preferably house the main wheel undercarriages and which because of aerodynamic loads tend towards the horizontal on chordwise hinges in fast flight and may be locked in a substantially vertical position for landing. The abutments, when horizontal, serve as auxiliary wings to reduce the rotor loading at high forward speeds. The nose wheel may be mechanically or hydraulically connected to the abutments to be retracted when the abutments rise to the horizontal.

Description

SPECIFICATION Provisional specification improvements in or relating to rotary winged aircraft This invention relates to rotary-winged aircraft, and more particularly to those having autorotating wings, such as autogyros. These provide an unstallable wing at low airspeeds; even though the aircraft may not maintain height it will be controllable.

However, at high forward speeds the rotary wing runs into increasing problems caused by the differential of effective airspeed between the advancing and retreating blade or blades. Afurther problem can be caused by the increasing drag of the lower portions of the airframe, such as the alighting gear undercarriage legs and wheels, resulting in a nosedown pitch of the fuselage at speed. This compounds the problems in that the propulsion system thrust line is deflected downwards, effectively increasing the weight of the fuselage and adding to the loads on the rotor blades.

It has long been known that the attachment to a rotorcraft of a fixed wing will relieve the rotor system of some loads in high-speed flight. Such a fixed wing has the disadvantage of increasing the width of the aircraft, hence the space required for storage. Nor does it overcome the problems of undercarriage drag, and the resultant fuselage attitude changes.

It is the object of this invention to provide a rotorcraftwith a fixed wing for fast forward flight, at no increase in floor-spaced needs, and to reduce undercarriage drag at speed.

According to the invention, the aircraft is provided with two cantilever mainwheel undercarriage legs, and a rectractable nose-wheel. The mainwheel legs are of a suitable lifting aerofoil section, set at an appropriate angle of attack to the relative airflow.

The main-wheels will preferably be enclosed in a suitable streamlined fairing. This fairing may be of a suitable cross-section such as to reduce the tip losses of the aerofoil by acting as an end-plate, winglet, or other such means of reducing the drag and loss of lift at the wing-tip, in fast forward flight.

The cantilever main undercarriage legs will be attached to the fuselage by hinges essentially parallel to the line of flight. The hinges will allow the legs to move from the angled down position of the landing and ground configuration to a substantially horizontal position as of a fixed wing.

When in the landing configuration the undercarriage legs will be held in that position by appropriate locking pins, or the like. The nosewheel leg will also be retained in the down and locked position by lock-pin or other means.

When in flight, as the airspeed increases, the main under carriage legs will be subject to aerodynamic forces such as to force them outward and lift them upward. Thus, if at such speeds the locks retaining the legs in the landing configuration are released, the legs will hinge outward and rise until restrained at a substantially in-line or horizontal position by suitable stops.

Further, by a simple mechanical, hydraulic or other connection to the nosewheel leg, this, too, may be raised by the aerodynamic lift applying to the main undercarriage legs, until it is in the fuselage, thus reducing drag.

Once the undercarriage legs are in the raised position they will remain there as long as the forward speed of the aircraft produces sufficient airflow, and they will provide lift, thus unloading the autogyro rotor blades.

When in the raised position the legs, which have then become small wings, may be locked in that position. Alternatively, they may be held there purely by aerodynamic forces, such that, if the forward speed of the aircraft is reduced until the aerodynamic lift is insufficient they will drop until spring-loaded down-locks again engage. The nosewheel leg would be lowered as a result of its interconnection with the main legs, and its downlock would also re-engage. An indication of all undercarriage locks engaged would be provided for the pilot, as with other aircraft having retractable undercarriages. The aircraft would then be ready for landing.

The invention is not confined to an autogyro or other rotary-winged aircraft in the form described, that is an autogyro having a tricycle undercarriage with a single nosewheel and cantilever mainwheel legs. It could equally be applied to a tail-wheel design, orto strut or wire-braced main undercarriage legs.

1. Cantilever aerofoil shaped abutments for rotary winged aircraft hingedly attached to the fuselage which at low speeds will tend towards the vertical and at high speeds due to the aerodynamic characteristic of the aerofoil will tend towards the horizontal to form an auxiliary wing.

2. Cantilever aerofoil shaped abutments for rotarty winged aircraft wherein the main wheel undercarriages of the autogyro are enclosed within the aerofoil shaped abutments.

3. Cantilever aerofoil shaped abutments for rotary winged aircraft as claimed in claim 1 wherein the main wheels are enclosed within the aerofoil shaped abutments.

4. Cantilever aerofoil shaped abutments for rotary winged aircraft wherein the nose wheel folds into the fuselage and the control is operated from the action of the aerofoil shaped abutments.

5. Cantilever aerofoil shaped abutments for rotary winged aircraft wherein the aerofoil shaped abutments are locked in the up and down positions at high speed and low speed respectively.

6. Cantilever aerofoil shaped abutments for rotary winged aircraft substantially as described herein.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (6)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Provisional specification improvements in or relating to rotary winged aircraft This invention relates to rotary-winged aircraft, and more particularly to those having autorotating wings, such as autogyros. These provide an unstallable wing at low airspeeds; even though the aircraft may not maintain height it will be controllable. However, at high forward speeds the rotary wing runs into increasing problems caused by the differential of effective airspeed between the advancing and retreating blade or blades. Afurther problem can be caused by the increasing drag of the lower portions of the airframe, such as the alighting gear undercarriage legs and wheels, resulting in a nosedown pitch of the fuselage at speed. This compounds the problems in that the propulsion system thrust line is deflected downwards, effectively increasing the weight of the fuselage and adding to the loads on the rotor blades. It has long been known that the attachment to a rotorcraft of a fixed wing will relieve the rotor system of some loads in high-speed flight. Such a fixed wing has the disadvantage of increasing the width of the aircraft, hence the space required for storage. Nor does it overcome the problems of undercarriage drag, and the resultant fuselage attitude changes. It is the object of this invention to provide a rotorcraftwith a fixed wing for fast forward flight, at no increase in floor-spaced needs, and to reduce undercarriage drag at speed. According to the invention, the aircraft is provided with two cantilever mainwheel undercarriage legs, and a rectractable nose-wheel. The mainwheel legs are of a suitable lifting aerofoil section, set at an appropriate angle of attack to the relative airflow. The main-wheels will preferably be enclosed in a suitable streamlined fairing. This fairing may be of a suitable cross-section such as to reduce the tip losses of the aerofoil by acting as an end-plate, winglet, or other such means of reducing the drag and loss of lift at the wing-tip, in fast forward flight. The cantilever main undercarriage legs will be attached to the fuselage by hinges essentially parallel to the line of flight. The hinges will allow the legs to move from the angled down position of the landing and ground configuration to a substantially horizontal position as of a fixed wing. When in the landing configuration the undercarriage legs will be held in that position by appropriate locking pins, or the like. The nosewheel leg will also be retained in the down and locked position by lock-pin or other means. When in flight, as the airspeed increases, the main under carriage legs will be subject to aerodynamic forces such as to force them outward and lift them upward. Thus, if at such speeds the locks retaining the legs in the landing configuration are released, the legs will hinge outward and rise until restrained at a substantially in-line or horizontal position by suitable stops. Further, by a simple mechanical, hydraulic or other connection to the nosewheel leg, this, too, may be raised by the aerodynamic lift applying to the main undercarriage legs, until it is in the fuselage, thus reducing drag. Once the undercarriage legs are in the raised position they will remain there as long as the forward speed of the aircraft produces sufficient airflow, and they will provide lift, thus unloading the autogyro rotor blades. When in the raised position the legs, which have then become small wings, may be locked in that position. Alternatively, they may be held there purely by aerodynamic forces, such that, if the forward speed of the aircraft is reduced until the aerodynamic lift is insufficient they will drop until spring-loaded down-locks again engage. The nosewheel leg would be lowered as a result of its interconnection with the main legs, and its downlock would also re-engage. An indication of all undercarriage locks engaged would be provided for the pilot, as with other aircraft having retractable undercarriages. The aircraft would then be ready for landing. The invention is not confined to an autogyro or other rotary-winged aircraft in the form described, that is an autogyro having a tricycle undercarriage with a single nosewheel and cantilever mainwheel legs. It could equally be applied to a tail-wheel design, orto strut or wire-braced main undercarriage legs. CLAIMS

1. Cantilever aerofoil shaped abutments for rotary winged aircraft hingedly attached to the fuselage which at low speeds will tend towards the vertical and at high speeds due to the aerodynamic characteristic of the aerofoil will tend towards the horizontal to form an auxiliary wing.

2. Cantilever aerofoil shaped abutments for rotarty winged aircraft wherein the main wheel undercarriages of the autogyro are enclosed within the aerofoil shaped abutments.

3. Cantilever aerofoil shaped abutments for rotary winged aircraft as claimed in claim 1 wherein the main wheels are enclosed within the aerofoil shaped abutments.

4. Cantilever aerofoil shaped abutments for rotary winged aircraft wherein the nose wheel folds into the fuselage and the control is operated from the action of the aerofoil shaped abutments.

5. Cantilever aerofoil shaped abutments for rotary winged aircraft wherein the aerofoil shaped abutments are locked in the up and down positions at high speed and low speed respectively.

6. Cantilever aerofoil shaped abutments for rotary winged aircraft substantially as described herein.