GB2152461A

GB2152461A - Autogyros

Info

Publication number: GB2152461A
Application number: GB08400475A
Authority: GB
Inventors: Kenneth Horatio Wallis
Original assignee: Individual
Current assignee: Individual
Priority date: 1984-01-10
Filing date: 1984-01-10
Publication date: 1985-08-07
Also published as: GB8400475D0; GB2152461B

Abstract

A means of providing a range of stable airspeeds above and below that of the naturally stable airspeed of a rotary winged aircraft having auto rotating rotors by applying a bias to the control system. Spring bias means 6 acting on control rods 1,2 to the rotor head mount 3 are adjustable by levers 9 acting via cables 8. <IMAGE>

Description

SPECIFICATION Improvements in or relating to rotary winged aircraft This invention relates to the control system of rotary winged aircraft and more particularly, though not exclusively, to those having auto-rotating rotors mounted on a rotor head on the lines of that described in G.B. Patent No 925,302 published in May 1963.

It is characteristic of the rotor head geometry and rotor blade design that an aircraft employing these features will assume stable airspeed of about 65 knots, if the control system is entirely free and unbiased.

The exact speed at which the aircraft stabilises will be determined by the centre of gravity and allup weight pertaining at the time.

The stable speed will be maintained regardless of the thrust being provided by the propulsion system. Thus, at high engine thrust, the aircraft will climb at the stable speed, while, if the engine fails, the aircraft will assume a stable glide at the same speed. This natural stability is a special feature of this design of aircraft. It eases pilot work load and increases safety.

However, there is need for some form of bias to be applied conveniently to the control system, if it is to be possible to fly the aircraft hands-off at lower and higher speeds than the naturally stable speed.

According to the invention this is achieved by applying a downward or upward bias to each of the push-pull control rods which control movement from the pilot's control column to the rotor head.

These rods, acting together provide movement in pitch and acting differentially, cause movement in the rotor head in the rolling plane.

The bias is applied to each rod by means of a tension spring or springs fastened at one end to the control rod, and arranged essentially parallel to it. The free end of the spring is attached to a flexible cable which passes through a suitable guide tube or fairlead to a friction-locked hand lever, such that aft movement of the lever will tension the spring and cause a downward bias on the control rod.

Thus, by releasing the control column, and adjusting the two friction-locked hand levers the aircraft may be controlled and adjusted for stable flight at a speed different from the natural trimmed speed.

Pulling the two levers back, will slow the aircraft, and differential movement may be used to counter any changes of torque reaction from the propulsion system.

Spring biases may be used to provide a handsoff speed higher than the naturally stable speed, by providing some upward bias to the control rods. However, the required hands-off range of useful speeds will generally be met without providing the upward bias to the control rods.

The position of the trimmer hand-levers should be such that they can be easily reached without the need for the pilot to change his normal position, and hence the C.G. of the aircraft. Usual position would be at the same height and general position as the control column hand-grip.

In a preferred form of the invention the bias springs are of the close coiled tension variety over part of their length, but have a portion of their length with the coils free. This allows considerable freedom of the natural and stabilising movements of the control system, while applying the appropriate over-all bias.

According to the invention we provide a method of applying a downward or upward bias to each push-pull control rod of the control system of a rotary winged aircraft which control movement from the pilots' control column to the rotor head and which when acting together provide movement in pitch and acting differentially cause movement of the rotor head in the rolling plane, said method comprising the operation of controls to adjust spring reaction on the push-pull rods.

According to a further aspect of the invention we provide a means for applying bias to the control system of a rotary winged aircraft said means comprising a hand lever for both control rods, sited in the vicinity of the pilots cockpit control column, a spring rigidly fixed at one end to each of the control rods and a connecting means between the free end of each spring and its appropriate hand lever so that the tension of each spring may be individually adjusted.

The invention will now be described, by way of example only, in conjunction with the accompanying illustration.

Referring to the illustration two control rods (1) and (2) pivotally located between a rotor head mount (3), shown dotted, and control column linkage (4) each have a bracket (5) fixed thereto. Preferably the positioning of the brackets (5) is adjustable for initial setting of the bias. Referring to one side only as both sides are the same, except for handing, a spring (6) is fixed at one end to the bracket (5). A flexible cable (7) fixed at the opposite end of the spring and routed via a guide tube or fairlead (8) is connected at its opposite end to a hand lever (9) located in the pilots cockpit in the vicinity of the cockpit control column where it is easily accessible without too much movement on the part of the pilot but at the same time does not interfere with the control column operation. Preferably the hand levers (9) are friction locked.

A preferred shape of spring (6)' is drawn separately.

Although one method of applying the trim bias for pitch and roll control is described, it is to be understood that the invention is not confined to this method, but could be achieved by other methods which apply a spring bias adjustable in the pitching and rolling plane.

1. A method of applying a downward or upward bias to each push-pull control rod of the control system of a rotary winged aircraft which

**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 rotary winged aircraft This invention relates to the control system of rotary winged aircraft and more particularly, though not exclusively, to those having auto-rotating rotors mounted on a rotor head on the lines of that described in G.B. Patent No 925,302 published in May 1963. It is characteristic of the rotor head geometry and rotor blade design that an aircraft employing these features will assume stable airspeed of about 65 knots, if the control system is entirely free and unbiased. The exact speed at which the aircraft stabilises will be determined by the centre of gravity and allup weight pertaining at the time. The stable speed will be maintained regardless of the thrust being provided by the propulsion system. Thus, at high engine thrust, the aircraft will climb at the stable speed, while, if the engine fails, the aircraft will assume a stable glide at the same speed. This natural stability is a special feature of this design of aircraft. It eases pilot work load and increases safety. However, there is need for some form of bias to be applied conveniently to the control system, if it is to be possible to fly the aircraft hands-off at lower and higher speeds than the naturally stable speed. According to the invention this is achieved by applying a downward or upward bias to each of the push-pull control rods which control movement from the pilot's control column to the rotor head. These rods, acting together provide movement in pitch and acting differentially, cause movement in the rotor head in the rolling plane. The bias is applied to each rod by means of a tension spring or springs fastened at one end to the control rod, and arranged essentially parallel to it. The free end of the spring is attached to a flexible cable which passes through a suitable guide tube or fairlead to a friction-locked hand lever, such that aft movement of the lever will tension the spring and cause a downward bias on the control rod. Thus, by releasing the control column, and adjusting the two friction-locked hand levers the aircraft may be controlled and adjusted for stable flight at a speed different from the natural trimmed speed. Pulling the two levers back, will slow the aircraft, and differential movement may be used to counter any changes of torque reaction from the propulsion system. Spring biases may be used to provide a handsoff speed higher than the naturally stable speed, by providing some upward bias to the control rods. However, the required hands-off range of useful speeds will generally be met without providing the upward bias to the control rods. The position of the trimmer hand-levers should be such that they can be easily reached without the need for the pilot to change his normal position, and hence the C.G. of the aircraft. Usual position would be at the same height and general position as the control column hand-grip. In a preferred form of the invention the bias springs are of the close coiled tension variety over part of their length, but have a portion of their length with the coils free. This allows considerable freedom of the natural and stabilising movements of the control system, while applying the appropriate over-all bias. According to the invention we provide a method of applying a downward or upward bias to each push-pull control rod of the control system of a rotary winged aircraft which control movement from the pilots' control column to the rotor head and which when acting together provide movement in pitch and acting differentially cause movement of the rotor head in the rolling plane, said method comprising the operation of controls to adjust spring reaction on the push-pull rods. According to a further aspect of the invention we provide a means for applying bias to the control system of a rotary winged aircraft said means comprising a hand lever for both control rods, sited in the vicinity of the pilots cockpit control column, a spring rigidly fixed at one end to each of the control rods and a connecting means between the free end of each spring and its appropriate hand lever so that the tension of each spring may be individually adjusted. The invention will now be described, by way of example only, in conjunction with the accompanying illustration. Referring to the illustration two control rods (1) and (2) pivotally located between a rotor head mount (3), shown dotted, and control column linkage (4) each have a bracket (5) fixed thereto. Preferably the positioning of the brackets (5) is adjustable for initial setting of the bias. Referring to one side only as both sides are the same, except for handing, a spring (6) is fixed at one end to the bracket (5). A flexible cable (7) fixed at the opposite end of the spring and routed via a guide tube or fairlead (8) is connected at its opposite end to a hand lever (9) located in the pilots cockpit in the vicinity of the cockpit control column where it is easily accessible without too much movement on the part of the pilot but at the same time does not interfere with the control column operation. Preferably the hand levers (9) are friction locked. A preferred shape of spring (6)' is drawn separately. Although one method of applying the trim bias for pitch and roll control is described, it is to be understood that the invention is not confined to this method, but could be achieved by other methods which apply a spring bias adjustable in the pitching and rolling plane. CLAIMS

1. A method of applying a downward or upward bias to each push-pull control rod of the control system of a rotary winged aircraft which control movement from the pilots control column to the rotor head and which when acting together provide movement in pitch and acting differentially cause movement of the rotor head in the rolling plane, said method comprising the operation of controls to adjust spring reaction on the push-pull rods.

2. A means for applying bias to the control system of a rotary winged aircraft said means comprising a hand lever for both control rods, sited in the vicinity of the pilots cockpit control column, a spring rigidly fixed at one end to each of the control rods and a connecting. means between the free end of each spring and its appropriate hand lever so that the tension of each spring may be individually adjusted.

3. A means for applying bias to the control system of a rotary winged aircraft as claimed in Claim 2 wherein the hand levers are friction locked.

4. A means for applying bias to the control system of a rotary winged aircraft substantially as described and claimed herein in conjunction with the accompanying illustration.