Radio-controlled helicopter
A radio-controlled helicopter (also RC helicopter) is model aircraft which is distinct from a RC airplane because of the differences in construction, aerodynamics, and flight training. Several basic designs of RC helicopters exist, of which some (such as those with collective pitch control) are more maneuverable than others. The more maneuverable designs are often harder to fly, but benefit from greater aerobatic capabilities. Flight controls allow pilots to control the collective (or throttle, on fixed pitch helicopters), the cyclic controls (pitch and roll), and the tail rotor (yaw). Controlling these in unison enables the helicopter to perform the same maneuvers as full-sized helicopters, such as hovering and backwards flight, and many other maneuvers that full-sized helicopters cannot, such as inverted flight (where collective pitch control provides negative blade pitch to hold heli up inverted, and pitch/yaw controls must be reversed by pilot). The various helicopter controls are effected by means of small servo motors, commonly known as servos. A solid-state gyroscope sensor is typically used on the tail rotor (yaw) control to counter wind- and torque-reaction-induced tail movement. Most newer helicopters have gyro-stabilization on the other 2 axis of rotation (pitch and roll) as well. Such 3-axis gyro is typically