SL Helicopter Flying Handbook/Helicopter Flight Controls

SECTION 3. Helicopter Flight Controls

A helicopter has four primary flight controls:

• Cyclic
• Collective
• Antitorque pedals
• Throttle

1 Collective

The collective is located to the left of the pilot, and is usually a lever that can be raised and lowered. The collective increases the pitch of the blades "collectively" around the entire rotation of the blades thus increasing the total thrust developed by the rotor system. The collective is usually used to control altitude in a helicopter.

2 Throttle Control

Helicopters are designed to operate at a specific RPM, or a narrow range of RPMs. As the pilot increases or decreases the collective, the amount of engine power needed to maintain the target RPM will increase or decrease. In single engine helicopters, the throttle is usually a twist grip mounted on the collective. As the pilot increases collective, they simultaneously roll on throttle to increase engine power. When the pilot decreases the collective, they roll off throttle to prevent the rotors from overspeeding.

Many helicopters have systems to assist the pilot in controlling the throttle as described below.

2.1 Correlator

A correlator is a mechanical linkage that automatically adds throttle when the collective is increased, and reduces throttle when the collective is lowered. The adjustments from a correlator are usually approximate and must be fine tuned by the pilot.

2.2 Governor

A governor an electronic device that measures the rotor RPM, and increases or decreases the throttle through an electric servo to maintain a specific RPM. In helicopters equipped with a governor, the governor can be engaged through a switch, or may come on automatically when the RPM enters a specific range. In all cases, it is possible for the pilot to manually override the governor by manually moving the throttle.

3 Cyclic

The cyclic is a stick that can be moved like a joystick forward and back, and left and right to control the direction of thrust from the main rotor. The cyclic is usually a stick mounted on the floor between the pilot's legs, though some helicopters such as the Robinson models use a T-stick cyclic mounted in the center of the cabin with a T-bar on the top.

The control is called the cyclic because it varies the pitch of the rotor blades as a function of their angle with the rotor mast over the course of a revolution. This results in an unequal lift/thrust from the blade is it rotates causing the rotor disk to tilt in the direction the pilot pushes the cyclic. When the rotor disk tilts, it diverts some of its total thrust to a horizontal component giving the helicopter a thrust in the direction the cyclic was pushed.

5 Anti-Torque Pedals

Antitorque Pedals are located on the floor in the same position rudder pedals would be in a fixed-wing aircraft. They are typically controlled with the feet and move together, pushing one causes the other to move forward and vice-versa. In a standard single main rotor helicopter, the anti-torque pedals control the pitch of the tail rotor, and thus the thrust from the tail rotor. This causes the helicopter to yaw left or right in the direction on which the pedal was pressed.