GB2105668A

GB2105668A - Autogyros

Info

Publication number: GB2105668A
Application number: GB08126478A
Authority: GB
Inventors: Kenneth Horatio Wallis
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-09-01
Filing date: 1981-09-01
Publication date: 1983-03-30
Also published as: GB2105668B

Abstract

The invention comprises a method of substantially eliminating resonance in an autogyro free control system caused by rotor induced vibration. The method comprising the fitment of a damping means to the control system in such a manner that the completely free movement of the control is prevented by the dampers but sufficient freedom remains so that natural "control column free" stability of the aircraft is retained. Preferably adjustable friction dampers are positioned approximately midway along two long control rods to the rotor head.

Description

SPECIFICATION Improvements in or relating to autogyro aircraft 1. It is a characteristic of a well-designed aircraft supported in flight by an auto-rotating rotary wing, i.e., an autogyro, that it will be naturally stable in flight. Such aircraft can be trimmed by applying a spring bias to a free control system such that the aircraft will maintain a selected speed and will fly continuously without need for correcting movements through the pilot's manual controls.

2. This natural stability is of great use in an autogyro being used for aerial work, in that it frees the pilot to attend to a primary task, such as looking through the viewfinders of cameras, aiming remote sensors, studying thermal images, and the like.

3. Unfortunately, all rotary winged aircraft suffer from some degree of rotor induced vibration. In a light autogyro, when under manual control, the pilot's controlling hand will effectively damp down any such vibration in the control system. However, when freed from the damping influence of the pilot's hand, the free control system may resonate with the rotor vibrations, causing an irritating vibration at the control column.

4. This invention is concerned with a method of preventing such resonance in the free control system.

5. According to the invention, friction or hydraulic dampers are fitted to the control system, such that the completely free movement of the control is prevented by the dampers but sufficient freedom remains so that the natural "control column free" stability of the aircraft is retained.

6. In a prefered form of the invention, an autogyro having a rotor head controlled by two push-pull control rods has adjustable friction dampers positioned roughly mid-way along the rods. The friction dampers are iightly springloaded, and the spring-loading on each damper can be adjusted in flight. Thus, while the aircraft is being flown "hands-off" the dampers can be adjusted until any resonance in the control system is damped, while the spring pressure on the dampers is the minimum required. By this means the control system remains essentially free, and the natural "stick-free" stability of the aircraft is not lost.

6. An additional benefit of this system is that the friction dampers can be designed to act as a steady in the middle of the long control rods, thus increasing their resistance to bending under compression loads, and reducing any bending resonance along the length of the rods.

7. Although a friction damped and adjustable system has been described, a similar result could be obtained by the use of hydraulic or other dampers. Further, although a system that can be adjusted in the air during "hands-off" flight is described, is an aircraft having a known and reproduceable rotor and control system suitably chosen fixed dampers could be employed.

8. Further, although linear dampers acting axially with the control rods are described, a similar result could be obtained with dampers concentric with the axes of the rotor head gymbal spindles or otherwise connected to the rotor control system.

Claims (Filed on 1 Sep 1982) 1. A method of preventing resonance in an autogyro free control system comprising, damping means fitted to the control system in such a manner that the completely free movement of the control is prevented but sufficient freedom remains so that the natural "control column free" stability of the aircraft is retained.

2. A method of preventing resonance in an autogyro free control system as claimed in Claim 1 wherein said damping means are operable on a component of said control system.

3. A method of preventing resonance in an autogyro free control system as claimed in Claim 2 wherein said damping means are friction dampers.

4. A method of preventing resonance in an autogyro free control system as claimed in Claim 2 wherein said damping means are hydraulic dampers.

5. A method of preventing resonance in an autogyro free control system as claimed in Claim 2 wherein said damping means comprises any means of reducing undesired fluctuations.

6. A method of preventing resonance in an autogyro free control system as claimed in any of Claims 3 to 5 wherein said damping means is operable on a component of the control system.

7. A method of preventing resonance in an autogyro free control system as claimed in Claim 6 wherein said component is a control rod.

8. A method of preventing resonance in an autogyro free control system as claimed in Claim 7 wherein said damping means further acts as a steady for said control rod.

9. A method of preventing resonance in an autogyro free control system as claimed in any previous Claim wherein said damping means is pre-set before flight.

10. A method of preventing resonance in an autogyro free control system as claimed in any of Claims 1 to 8 wherein said damping means is adjustable in flight.

11. A method of preventing resonance in an autogyro free control system substantially as described in the specification herewith.

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Improvements in or relating to autogyro aircraft 1. It is a characteristic of a well-designed aircraft supported in flight by an auto-rotating rotary wing, i.e., an autogyro, that it will be naturally stable in flight. Such aircraft can be trimmed by applying a spring bias to a free control system such that the aircraft will maintain a selected speed and will fly continuously without need for correcting movements through the pilot's manual controls. 2. This natural stability is of great use in an autogyro being used for aerial work, in that it frees the pilot to attend to a primary task, such as looking through the viewfinders of cameras, aiming remote sensors, studying thermal images, and the like. 3. Unfortunately, all rotary winged aircraft suffer from some degree of rotor induced vibration. In a light autogyro, when under manual control, the pilot's controlling hand will effectively damp down any such vibration in the control system. However, when freed from the damping influence of the pilot's hand, the free control system may resonate with the rotor vibrations, causing an irritating vibration at the control column. 4. This invention is concerned with a method of preventing such resonance in the free control system. 5. According to the invention, friction or hydraulic dampers are fitted to the control system, such that the completely free movement of the control is prevented by the dampers but sufficient freedom remains so that the natural "control column free" stability of the aircraft is retained. 6. In a prefered form of the invention, an autogyro having a rotor head controlled by two push-pull control rods has adjustable friction dampers positioned roughly mid-way along the rods. The friction dampers are iightly springloaded, and the spring-loading on each damper can be adjusted in flight. Thus, while the aircraft is being flown "hands-off" the dampers can be adjusted until any resonance in the control system is damped, while the spring pressure on the dampers is the minimum required. By this means the control system remains essentially free, and the natural "stick-free" stability of the aircraft is not lost. 6. An additional benefit of this system is that the friction dampers can be designed to act as a steady in the middle of the long control rods, thus increasing their resistance to bending under compression loads, and reducing any bending resonance along the length of the rods. 7. Although a friction damped and adjustable system has been described, a similar result could be obtained by the use of hydraulic or other dampers. Further, although a system that can be adjusted in the air during "hands-off" flight is described, is an aircraft having a known and reproduceable rotor and control system suitably chosen fixed dampers could be employed. 8. Further, although linear dampers acting axially with the control rods are described, a similar result could be obtained with dampers concentric with the axes of the rotor head gymbal spindles or otherwise connected to the rotor control system. Claims (Filed on 1 Sep 1982)

1. A method of preventing resonance in an autogyro free control system comprising, damping means fitted to the control system in such a manner that the completely free movement of the control is prevented but sufficient freedom remains so that the natural "control column free" stability of the aircraft is retained.