Collective Control System

The collective control system changes the amount of lift provided by the main rotor disk. The position of the collective control is also monitored by the power control so the engine always provides the necessary power . It consists of the components that follow:

• Pilot collective stick and grip

• Pilot collective jackshaft

• Collective friction assembly

• Collective balance spring

• Collective transducer

• Jackshaft-to-reversing bellcrank control tube

• Collective reversing bellcrank

• Collective reversing bellcrank support

• Reversing bellcrank-to-lever control tube

• Collective lever

• Lever-to-actuator support bellcrank control tube

• Collective actuator support bellcrank

• Collective boosted link

• Collective boosted bellcrank

• Collective boosted bellcrank support

• Collective boosted rod

• Copilot jumper

If the dual controls kit is installed, it also consists of the copilot collective stick and grip and the copilot collective jackshaft. Refer to Dual Controls Kit for details.

Pilot collective stick and grip

The pilot collective stick and grip is the collective control for the operator. It is a tube made from aluminum with a plastic grip. It is located on the left side of the pilot seat. The grip has the pilot throttle switch and the landing lights switch. A quick-disconnect connector connects its harness to the helicopter wiring harness under the floor.

Pilot collective jackshaft

The pilot collective jackshaft is the pivot for the collective stick. It is a tube made from aluminum with supports at both ends. A machined aluminum socket is the receptacle for the lower end of the collective stick. It has two arms at its left end. One is the output to the jackshaft-to-reversing bellcrank control tube and the other mounts the collective transducer. It is located under the cockpit floor left of the pilot seat and under the copilot seat. Its left support is mounted on the left keel beam and its end is protruding on the left side for the copilot jackshaft in the dual controls kit.

Collective friction assembly

The collective friction assembly is on the right support of the pilot collective jackshaft. It is made from machined aluminum. It’s forward side is cut and it has a friction handle that adjusts the friction on the supported surface of the jackshaft. It is mounted on a bracket forward of the center frame at FS 110.0 with three bolts.

Collective balance spring

The collective balance spring counteracts the weight of the pilot collective stick and grip assembly, and also, if it is installed, of the copilot collective stick and grip. It is made from corrosion resistant steel. One end of the balance frame is connected to a bracket on the output arm of the collective jackshaft and the other end to an adjustable eyebolt mounted on the center frame at FS 97.

Collective transducer

The collective transducer monitors the position of the collective for the Engine Control Unit (ECU). It is a linear variable resistor mounted in a rugged case. The wiper shaft is connected to an arm of the pilot collective jackshaft and the case is connected to a bracket mounted on the left keel beam. It is connected to the ECU through the helicopter wiring harness.

Jackshaft-to-reversing bellcrank control tube

The jackshaft-to-reversing bellcrank control tube transmits the collective position from the pilot collective jackshaft to the collective reversing bellcrank. It is a fixed length aluminum tube with spherical bearings at both ends.

Collective reversing bellcrank

The collective reversing bellcrank reverses and slightly amplifies the movement of the collective and transfers it to the reversing bellcrank-to-lever control tube. It is made from a machined aluminum billet. It has two bushings at one end to attach to the jackshaft-to-reversing bellcrank control tube and a spherical bearing at the other end to attach to the reversing bellcrank-to-lever control tube. Its bearing, near the center, pivots on the reversing bellcrank support.

Reversing bellcrank support

The reversing bellcrank support is the mount for the collective reversing bellcrank. It is made from a machined aluminum billet. It has two bushings for mounting the collective reversing bellcrank pivot. It is mounted aft of the center frame at FS 128.0 under the cabin floor.

Reversing bellcrank-to-lever control tube

The reversing bellcrank-to-lever control tube transmits the collective position from the collective reversing bellcrank to the collective lever assembly. It is a fixed length aluminum tube with a spherical bearing at one end and a fork at the other end. The fork has two bushings to attach to the spherical bearing of the collective reversing bellcrank.

Collective lever

The collective lever transmits the collective position from the reversing bellcrank-to-lever control tube to the lever-to-actuator support bellcrank control tube. It also mixes the collective input to the cyclic position by supporting the cyclic mixer. It is made from a machined aluminum billet. Its main pivot has two bearings and is mounted horizontally to the frame at FS 147.0 at the bottom of the controls tunnel. It has two arms, a small one to the left extending down, and a large one to the right extending back. The small arm has a fork with two bushings to connect to the spherical bearing of the reversing bellcrank-to-lever control tube. The large arm has a small fork at the top with tow bushings to connect to the spherical bearing of the lever-to-actuator support bellcrank control tube. It also has a large fork with two bushings for the upper universal joint of the cyclic mixer.

Lever-to-actuator support bellcrank control tube

The lever-to-actuator support bellcrank control tube transmits the collective position from the collective lever to the collective actuator support bellcrank. It is an aluminum tube with a fixed end with a spherical bearing and an adjustable end with a spherical bearing.

Collective actuator support bellcrank

The collective actuator support bellcrank transmits the collective position from the collective lever to the trunnion of the collective 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 lever-to-actuator support bellcrank control tube. Its pivot has two bearings and is mounted on the collective servo-actuator support. The other end connects to the collective servo-actuator trunnion with bearings, washers, spacers, and safetied nuts.

Collective boosted link

The collective boosted link transmits the boosted collective position to the collective 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 collective servo-actuator and on the collective boosted bellcrank.

Collective boosted bellcrank

The collective boosted bellcrank transmits the boosted collective position from the collective boosted link to the collective 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 an inverted fork to connect to the spherical bearing of the collective boosted rod.

Collective boosted bellcrank support

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

Collective boosted rod

The collective boosted rod transmits the boosted collective position from the collective boosted bellcrank to the rotating controls. It is made from machined corrosion resistant steel and has spherical bearings at both ends. It lifts and lowers the swashplate according to the position of the collective stick.

Copilot jumper

The copilot jumper provides a ground to the avionics for the copilot throttle switch when the dual controls are not installed. It simulates the idle position of the throttle switch to let the engine operate normally. It is a connector installed under the left cockpit floor supported by a clamp.

Operation

The operator controls the collective pitch of the main rotor by lifting and lowering the pilot collective stick and grip, or by lifting and lowering the copilot collective stick and grip if the dual controls are installed. The weight of the collective sticks and grips is balanced by the collective balance spring. The pilot collective jackshaft transforms the up and down motion of the collective stick into a circular motion. The arm connected to the jackshaft-to-reversing bellcrank control tube and the arm connected to the collective transducer change the circular motion into a linear motion. The collective transducer gives the position of the collective to the ECU. The jackshaft-to-reversing bellcrank control tube pushes and pulls on the collective reversing bellcrank. The collective reversing bellcrank pivots on the support and reverses the movement, amplifying it slightly. The reversing bellcrank-to-lever control tube pushes and pulls on the collective lever. The collective lever pivots on the frame and transforms the fore-and-aft motion into an up-and-down motion for the lever-to-actuator support bellcrank control tube. The cyclic mixer is also mounted on the collective lever and is moved up-and-down at the same time. The lever-to-actuator support bellcrank control tube pushes and pulls on the collective actuator support bellcrank. The collective actuator support bellcrank pivots and controls the collective servo-actuator, which boosts the motion and transmits it horizontally to the collective boosted link. The collective boosted link pushes and pulls on the collective boosted bellcrank. The collective boosted bellcrank pivots on the collective boosted bellcrank support and transforms the horizontal motion from the collective boosted link to a vertical motion for the collective boosted rod. The collective boosted rod moves the swashplate up and down according to the position of the collective stick and grip.