angle of each main rotor blade independently, depending on its position in the cycle. The pitch is changed so that each blade will have the same angle of incidence as it passes the same point in the cycle, changing the lift generated by the blade at that point and causing each blade to change its angle of incidence, that is, to rotate slightly along its long axis, in sequence as it passes the same point. If that point is dead ahead, the blade pitch increases briefly in that direction. Thus, If the pilot pushes the cyclic forward, the rotor disk tilts forward, and the helicopter is drawn straight ahead. If the pilot pushes the cyclic to the right, the rotor disk tilts to the right. Any rotor system has a delay between the point in rotation where the controls introduce a change in pitch and the point where the desired change in the rotor blade's flight occurs. This difference is caused by phase lag, often confused with gyroscopic precession. A rotor is an oscillatory system that obeys the laws that govern vibration—which, depending on the rotor system, may resemble the behaviour of a gyroscope. Collective The collective pitch control, or collective lever, is normally located on the left side of the pilot's seat with an adjustable friction control to prevent inadvertent movement. The collective changes the pitch angle of all the main rotor blades collectively (i.e., all at the same time) and is independent of their position in the rotational cycle. Therefore, if a collective input is made, all the blades change equally, and as a result, the helicopter increases or decreases its total lift derived from the rotor. In level flight this would cause a climb or descent, while with the helicopter pitched forward an increase in total lift would produce an acceleration together with a given amount of ascent. If a helicopter suffers a power failure a pilot can adjust the collective pitch to keep the rotor spinning, generating enough lift to touch down and skid in a relatively soft landing. The collective pitch control in a Boeing CH-47 Chinook is called a thrust control, but serves the same purpose, except that it controls two rotor systems, applying differential collective pitch. Throttle Helicopter rotors are designed to operate at a specific rotational speed. The throttle controls the power of the engine, which is connected to the rotor by