Anti-torque Control System

The anti-torque rotor control lets the operator control the thrust provided by the tail rotor to counteract the torque produced by the main rotor and control the yaw (heading) of the helicopter. It consists of the components that follow:

• Pilot left pedal

• Pilot right pedal

• Forward pedal jackshaft

• Aft pedal jackshaft

• Jackshaft supports

• Jackshaft-to-directional quadrant left pedal link

• Jackshaft-to-directional quadrant right pedal link

• Directional quadrant

• Directional quadrant stop

• Left forward cable

• Right forward cable

• Forward pulleys

• Mid lower pulleys

• Mid upper pulleys

• Aft pulleys

• Left aft cable

• Right aft cable

• Left aft cable directional bellcrank

• Right aft cable directional bellcrank

• Directional bellcrank left control support

• Directional bellcrank right control support

• Short rod

• Long rod

• Pitch change mechanism

• Tail rotor control tube

If the dual controls kit is installed, it also consists of the components that follow:

• Copilot left pedal

• Copilot right pedal

Pilot left pedal

The pilot left pedal lets the operator control the pitch of the tail rotor blades and the thrust the tail rotor produces. It consists of the upright tube with the adjustable pedal support and of the left pedal with its quick release pin. It is made from aluminum with the quick release pin made from corrosion resistant steel. The pedal is adjusted by pulling the quick release pin, sliding the pedal forward or aft on the support to the desired position, and pushing on the quick release pin to lock it. It is mounted on the right socket of the forward pedal jackshaft.

Pilot right pedal

The pilot right pedal lets the operator control the pitch of the tail rotor blades and the thrust the tail rotor produces. It consists of the upright tube with the adjustable pedal support and of the left pedal with its quick release pin. It is made from aluminum with the quick release pin made from corrosion resistant steel. The pedal is adjusted by pulling the quick release pin, sliding the pedal forward or aft on the support to the desired position, and pushing on the quick release pin to lock it. It is mounted on the right socket of the aft pedal jackshaft.

Forward pedal jackshaft

The forward pedal jackshaft is the pivot for the pilot left pedal and the copilot left pedal, if the dual controls are installed. It transforms the fore-and-aft motion of the pedals into a rotary motion. It is a tube made from aluminum with sockets for the pedals made from machined aluminum at both ends. It has an arm to the right of the helicopter center line to connect to the jackshaft-to-directional quadrant left pedal link. It is located aft of the forward canted bulkhead in three jackshaft supports.

Aft pedal jackshaft

The aft pedal jackshaft is the pivot for the pilot right pedal and the copilot right pedal, if the dual controls are installed. It transforms the fore-and-aft motion of the pedals into a rotary motion. It is a tube made from aluminum with sockets for the pedals made from machined aluminum at both ends. It has an arm to the left of the helicopter center line to connect to the jackshaft-to-directional quadrant right pedal link. It is located aft of the forward pedal jackshaft in three jackshaft supports.

Jackshaft supports

The jackshaft supports hold the forward and aft pedal jackshafts. They are made from carbon fiber reinforced plastic. The left jackshaft support is located between the openings for the copilot pedals, the center support is located close to the right of the helicopter center line, and the right jackshaft support is located between the pilot pedals.

Jackshaft-to-directional quadrant left pedal link

The jackshaft-to-directional quadrant left pedal link transmits the fore-and-aft motion from the arm of the forward pedal jackshaft to the directional quadrant. It is made from aluminum. It has spherical bearings at both ends to connect to the forks of the forward pedal jackshaft arm and the directional quadrant.

Jackshaft-to-directional quadrant right pedal link

The jackshaft-to-directional quadrant right pedal link transmits the fore-and-aft motion from the arm of the aft pedal jackshaft to the directional quadrant. It is made from aluminum. It has spherical bearings at both ends to connect to the forks of the aft pedal jackshaft arm and the directional quadrant.

Directional quadrant

The directional quadrant transmits the opposite fore-and-aft motions of the jackshaft-to-directional quadrant left and right pedal links to the left and right forward cables. It is made from a machined aluminum billet. It has two forks with bushings to connect to the spherical bearings of the jackshaft-to-directional quadrant left and right pedal links. It has two bearings separated by a spacer in its center to mount it to the helicopter structure. The left and right quarter-circles have slots for the left and right forward cables. The directional quadrant stop is at the back of each quarter-circle and limits the motion of the directional quadrant.

Directional quadrant stop

The directional quadrant stop limits the motion of the anti-torque control. It is a chromium plated steel bolt with a castellated nut and a washer. It is safetied with a split pin. It is located aft of the directional quadrant pivot.

Left forward cable

The left forward cable transmits the motion of the directional quadrant to the left aft cable directional bellcrank through the left aft cable. It is a cable with a swaged ball fitting at its forward end and a swaged turnbuckle fitting at its aft end made from corrosion resistant steel. It is located between the directional quadrant and the tailboom and is routed through the forward pulleys, mid lower pulleys, and mid upper pulleys.

Right forward cable

The right forward cable transmits the motion of the directional quadrant to the right aft cable directional bellcrank through the right aft cable. It is a cable with a swaged ball fitting at its forward end and a swaged turnbuckle fitting at its aft end, all made from corrosion resistant steel. It is located between the directional quadrant and the tailboom and is routed through the forward pulleys, mid lower pulleys, and mid upper pulleys.

Forward pulleys

The forward pulleys let the left and right forward cables move freely and keep them away from the structure. They are made from phenolic. They are mounted on the center frame at FS 97.0 under the cockpit floor.

Mid lower pulleys

The mid lower pulleys let the left and right forward cables move freely and keep them away from the structure. They are made from phenolic. They are mounted on the frame at FS 147.0 at the lower forward end of the control tunnel.

Mid upper pulleys

The mid upper pulleys let the left and right forward cables move freely and keep them away from the structure. They are made from phenolic. They are mounted on a bracket to the truss assembly at the top of the control tunnel.

Aft pulleys

The aft pulleys let the left and right aft cables move freely and keep them away from the structure. They are made from phenolic. They are mounted on a bracket at the front of the tailboom.

Left aft cable

The motion of the directional quadrant and the left forward cable transmits to the left aft cable. It is a cable with a swaged clevis fitting at its aft end and a swaged turnbuckle fitting at its forward end, all made from corrosion resistant steel. It also has a turnbuckle barrel made from steel to join it with the left forward cable and adjust the tension. The clips, made from corrosion resistant steel, lock the turnbuckle barrel on the cable turnbuckle fittings. It is located between the aft end of the left forward cable and the left aft cable directional bellcrank and is routed through the aft pulleys and through the tailboom.

Right aft cable

The motion of the directional quadrant and the right forward cable transmits to the right aft cable. It is a cable with a swaged clevis fitting at its aft end and a swaged turnbuckle fitting at its forward end, all made from corrosion resistant steel. It also has a turnbuckle barrel made from steel to join it with the right forward cable and adjust the tension. The clips, made from corrosion resistant steel, lock the turnbuckle barrel on the cable turnbuckle fittings. It is located between the aft end of the left forward cable and the left aft cable directional bellcrank and is routed through the aft pulleys and through the tailboom.

Left aft cable directional bellcrank

The left aft cable directional bellcrank, together with the right aft cable directional bellcrank and the short rod, transforms the opposite fore-and-aft motions of the left and right aft cables to a side-to-side motion for the pitch change mechanism of the tail rotor gearbox. It is a bellcrank made from a machined aluminum billet with a roller bearing for pivot, a spherical bearing to attach the clevis of the left aft cable, and bushings to attach the short and long rods. A hole is also provided to insert a rigging pin. It is located in the support fitting for the tail rotor gearbox and empennage on the left side.

Right aft cable directional bellcrank

The right aft cable directional bellcrank, together with the left aft cable directional bellcrank and the short rod, transforms the opposite fore-and-aft motions of the left and right aft cables to a side-to-side motion for the pitch change mechanism of the tail rotor gearbox. It is a bellcrank made from a machined aluminum billet with a roller bearing for pivot, a spherical bearing to attach the clevis of the left aft cable, and a bushing to attach the short rod. A hole is also provided to insert a rigging pin. It is located in the support fitting for the tail rotor gearbox and empennage on the right side.

Directional bellcrank left control support

The directional bellcrank left control support is the pivot of the left aft cable directional bellcrank. It is made from a machined aluminum billet. It is bolted inside the support fitting for the tail rotor gearbox and empennage on the left side.

Directional bellcrank right control support

The directional bellcrank right control support is the pivot of the right aft cable directional bellcrank. It is made from a machined aluminum billet. It is bolted inside the support fitting for the tail rotor gearbox and empennage on the right side.

Short rod

The short rod links the left and right aft cable directional bellcranks. It is fixed in length and is made from corrosion resistant steel with spherical bearings at both ends. It is located between the left and right aft cable directional bellcranks.

Long rod

The long rod transmits the side-to-side motion from the left aft cable directional bellcrank to the pitch change mechanism. It is made from corrosion resistant steel. One end is connected to the pitch change mechanism and is adjustable, the other end is connected to the left aft cable directional bellcrank.

Pitch change mechanism

The pitch change mechanism reverses the motion from the long rod and transmits it to the tail rotor control tube. It consists of the housing, boot, trunnion, trunnion bearing, levers, and idler. It is made from cast aluminum with steel bearings and a synthetic rubber boot. It is mounted on the right side of the tail rotor gearbox.

Tail rotor control tube

The tail rotor control tube transmits the side-to-side motion of the pitch change mechanism to the rotating controls of the tail rotor. It is made from steel and is located inside the tail rotor shaft. It is attached to the crosshead of the rotating controls on the left side and is attached to the trunnion bearing on the right side. It also rotates with the tail rotor shaft.

Operation

The operator pushes on the left and right pedals. The left and right pedals pivot on the pedal jackshafts. The arms of the pedal jackshafts transmit the fore-and-aft motions to the directional quadrant, which makes the pedal jackshafts and the pedals move in opposite directions. The directional quadrant stop limits the motion of the system. The left and right cables transmit the opposite fore-and-aft motions to the aft cable directional bellcranks. The assembly of the left and right aft cable directional bellcranks with the short rod and long rod transform the opposite fore-and-aft motions into a side-to-side motion, which the long rod transmits to the levers of the pitch change mechanism. The levers pivot on the idler and reverse the side-to-side motion. The trunnion then transmits the side-to-side motion to the tail rotor control tube to change the pitch of the tail rotor blades.