Cyclic Control System

The cyclic control system changes the amount of lift of the main rotor disk around its rotation plane, effectively changing the direction where this lift is applied. This lets the operator control the pitch and roll of the helicopter. It consists of the components that follow:

• Pilot cyclic stick and grip

• Pilot cyclic stick base fitting

• Copilot cyclic stick base fitting

• Cyclic stick torque tube

• Cyclic balance spring

• Cyclic main torque tube

• Cyclic tube

• Cyclic mixer

• Left mixer-to-actuator support bellcrank control tube

• Right mixer-to-actuator support bellcrank control tube

• Left actuator support bellcrank

• Right actuator support bellcrank

• Left boosted link

• Right boosted link

• Left boosted bellcrank

• Right boosted bellcrank

• Left boosted bellcrank support

• Right boosted bellcrank support

• Left boosted rod

• Right boosted rod

If the dual controls kit is installed, it also consists of the copilot cyclic stick and grip.

Pilot cyclic stick and grip

The pilot cyclic stick and grip lets the operator control the cyclic pitch of the main rotor to control the flight of the helicopter. It is an aluminum tube with a plastic grip assembly. It is mounted on the pilot cyclic stick base fitting in front of the pilot seat. It has the Intercommunication System (ICS) trigger switch. A quick-disconnect connector connects its harness to the helicopter wiring harness under the floor.

Pilot cyclic stick base fitting

The pilot cyclic stick base fitting supports the pilot cyclic stick and grip and transmits its motion to the cyclic stick torque tube. It is an assembly of machined aluminum, corrosion resistant steel, and carbon fiber reinforced plastic. It consists of the base bolted to the floor in front of the pilot seat. The lower lever extends above and below the base. The lower lever is mounted on a spherical bearing with a slotted race that lets you adjust the friction of the cyclic. The spherical bearing is held in the base from below by the cyclic stop and a spacer. The cyclic stop limits the motion of the lower lever. The hand wheel lets the operator adjust the cyclic friction by the tension the threaded shaft and the threaded wedge apply to the spherical bearing race through the thrust wedge. A socket on the top end of the lower lever receives the bottom end of the pilot cyclic stick. Two ball bearings in the bottom end of the lower lever connect to the cyclic stick torque tube.

Copilot cyclic stick base fitting

The copilot cyclic stick base fitting supports the copilot cyclic stick and grip when the dual controls are installed. It is an assembly made from machined aluminum and corrosion resistant steel. It consists of the support bolted to the floor in front of the copilot seat, a spherical bearing is mounted in the support with a retaining ring, and the lower lever connects to the left end of the cyclic stick torque tube. The inside threads at the top of the lower lever provide the mounting location for the copilot cyclic stick and grip.

Cyclic stick torque tube

The cyclic stick torque tube links the pilot and the copilot base fittings and transmits their motion to the cyclic main torque tube. It is an aluminum tube with a fork on the right to connect to the lower lever of the pilot cyclic stick base fitting. It has a fork with two ball bearings on the left to connect to the lower lever of the copilot cyclic stick base fitting. It also has a bracket in the center to connect it to the cyclic main torque tube.

Cyclic balance spring

The cyclic balance spring counteracts the weight of the pilot cyclic stick and grip and the copilot cyclic stick and grip when the dual controls are installed. It is a spring made from high-carbon steel. Its aft end is connected to a bracket mounted in front of the cyclic stick torque tube on the copilot side. Its forward end is connected to an adjustable eyebolt mounted on a bracket under the floor.

Cyclic main torque tube

The cyclic main torque tube transmits the fore and aft motion of the cyclic stick torque tube to the cyclic mixer and transforms the side-to-side motion of the cyclic stick torque tube into a rotary motion, that it also transmits to the cyclic mixer. It is an aluminum tube with a fork at its aft end to connect to the cyclic mixer through a universal joint. It has a doubler at its forward end that contains a ball bearing to which is mounted a swivelling rod end made from corrosion resistant steel with a spherical bearing that connects to the bracket in the center of the cyclic stick torque tube. A lever, at the aft end of the doubler, connects to the cyclic tube and lets the cyclic main torque tube rotate when the cyclic stick torque tube moves from side to side.

Cyclic tube

The cyclic tube lets the cyclic main torque tube move fore and aft freely and is the pivot on which the arm of the cyclic main torque tube rotates when it moves from side to side. It is an aluminum tube with fixed rod ends made from corrosion resistant steel. It has spherical bearings at both ends. It is located under the cockpit floor in front of the copilot seat. It is connected to the arm of the cyclic main torque tube in the center of the helicopter and to a bracket under the cockpit floor on the left side.

Cyclic mixer

The cyclic mixer takes the fore and aft and the rotary motions of the cyclic main torque tube, transforms them into up and down motions, and transmits them to the left and right mixer to the actuator support bellcrank control tubes. It also mixes the position of the collective with the cyclic motion. It is made from a machined aluminum billet. It is connected to the cyclic main torque tube through a universal joint at its bottom end. It is mounted on the collective lever with another universal joint at its top center. Two arms extend laterally forward, with the fork at their ends connected to the spherical bearings at the bottom ends of the left and right mixer-to-actuator support bellcrank control tubes.

Left mixer-to-actuator support bellcrank control tube

The left mixer-to-actuator support bellcrank control tube transmits the up and down motion from the cyclic mixer to the left actuator support bellcrank. It is an aluminum tube with rod ends made from corrosion resistant steel with a spherical bearing. The bottom rod end is fixed and the top end is adjustable. It is located in the controls tunnel, where its bottom end is connected to the left arm of the cyclic mixer and its top end is connected to the left actuator support bellcrank.

Right mixer-to-actuator support bellcrank control tube

The right mixer-to-actuator support bellcrank control tube transmits the up and down motion from the cyclic mixer to the right actuator support bellcrank. It is an aluminum tube with rod ends made from corrosion resistant steel with a spherical bearing. The bottom rod end is fixed and the top end is adjustable. It is located in the controls tunnel, where its bottom end is connected to the right arm of the cyclic mixer and its top end is connected to the right actuator support bellcrank.

Left actuator support bellcrank

The left actuator support bellcrank transmits the left cyclic motion from the cyclic mixer to the trunnion of the left cyclic servo-actuator. It is made from a machined aluminum billet. A fork with two bushings connects to the spherical bearing on the adjustable end of the left mixer-to-actuator support bellcrank control tube. Its pivot has two bearings and is mounted on the left cyclic servo-actuator support. The other end connects to the left cyclic servo-actuator trunnion with bearings, washers, spacers, and safetied nuts.

Right actuator support bellcrank

The right actuator support bellcrank transmits the right cyclic motion from the cyclic mixer to the trunnion of the right cyclic servo-actuator. It is made from a machined aluminum billet. A fork with two bushings connects to the spherical bearing on the adjustable end of the right mixer-to-actuator support bellcrank control tube. Its pivot has two bearings and is mounted on the right cyclic servo-actuator support. The other end connects to the right cyclic servo-actuator trunnion with bearings, washers, spacers, and safetied nuts.

Left boosted link

The left boosted link transmits the boosted left cyclic motion to the left boosted bellcrank. It is a fixed length link made from machined corrosion resistant steel. It has forks with bushings on both ends to connect to spherical bearings on the left cyclic servo-actuator and on the left boosted bellcrank.

Right boosted link

The right boosted link transmits the boosted right cyclic motion to the left boosted bellcrank. It is a fixed length link made from machined corrosion resistant steel. It has forks with bushings on both ends to connect to spherical bearings on the right cyclic servo-actuator and on the right boosted bellcrank.

Left boosted bellcrank

The left boosted bellcrank transmits the boosted left cyclic motion from the left boosted link to the left boosted rod. It is made from machined corrosion resistant steel. It has a spherical bearing to connect to the collective boosted link, it pivots on a ball bearing, and it has another spherical bearing to connect to the fork of the left boosted rod.

Right boosted bellcrank

The right boosted bellcrank transmits the boosted right cyclic motion from the right boosted link to the right boosted rod. It is made from machined corrosion resistant steel. It has a spherical bearing to connect to the left boosted link, it pivots on a ball bearing, and it has another spherical bearing to connect to the fork of the right boosted rod.

Left boosted bellcrank support

The left boosted bellcrank support is made from a machined aluminum billet. It is bolted to the front left of the main gearbox case and has the pivot of the left boosted bellcrank.

Right boosted bellcrank support

The right boosted bellcrank support is made from a machined aluminum billet. It is bolted to the front right of the main gearbox case and has the pivot of the right boosted bellcrank.

Left boosted rod

The left boosted rod transmits the boosted left cyclic motion from the left boosted bellcrank to the rotating controls. It has a tube made from aluminum, a fixed fork at its top end, and an adjustable fork at its bottom end. Both forks are made from corrosion resistant steel. It lifts and lowers the left horn of the fixed swashplate according to the position of the cyclic stick.

Right boosted rod

The right boosted rod transmits the boosted left cyclic motion from the left boosted bellcrank to the rotating controls. It has a tube made from aluminum, a fixed fork at its top end, and an adjustable fork at its bottom end. Both forks are made from corrosion resistant steel. It lifts and lowers the right horn of the fixed swashplate according to the position of the cyclic stick.

Operation

The operator controls the cyclic pitch of the main rotor by moving the pilot cyclic stick and grip or by moving the copilot cyclic stick and grip if the dual controls are installed. The weight of the cyclic sticks is balanced by the cyclic balance spring. The motion of the cyclic sticks is transmitted to the cyclic stick torque tube by the lower levers of the cyclic stick base fittings. The fore and aft motion is transmitted directly by the cyclic main torque tube to the collective mixer that transforms it to an up and down motion. The side-to-side motion makes the cyclic main torque tube rotate on the pivot made by the arm and the cyclic tube. This rotary motion makes the cyclic mixer pivot on the universal joint connected to the collective lever and makes its left and right arms move up and down opposite to each other. The cyclic mixer takes the collective position and mixes it with the cyclic motions, transforming them into up and down motions for the left and right mixer-to-actuator bellcrank control tubes. The left and right mixer-to-actuator bellcrank control tubes transmit their up and down motions to their respective actuator support bellcranks. The left and right actuator support bellcranks pivot and control their respective servo-actuator, which boost the motions and transmits them horizontally to the left and right boosted links. The left and right boosted links push and pull on the left and right boosted bellcranks. The left and right boosted bellcranks pivot on the left and right boosted bellcrank supports and transforms the horizontal motions from the left and right boosted links to vertical motions for the left and right boosted rods. The boosted rods move the left and right horns of the fixed swashplate according to the position of the cyclic stick and grip.