A search helicopter on a control platform with four degrees of freedom, inspired by the official Lego sets 8485 and 9396. Each position control on the remote activates only one motor. The pitch motor moves the rear actuator only, the roll motor moves the two side actuators in opposite directions and the elevation motor (the XL) moves all three actuators in the same direction. An adder-subtractor system based on three differential gears ensures that the motors' geartrains do not interfere with each other, and that the actuators all move at the same speed. The fourth motor turns an 8t gear inside the turntable's inner ring to allow the chopper to yaw.

The main rotor is built on a swashplate giving it full cyclic and collective pitch control. The rotor blades' pitch levers are connected by flex cables to the platform's base, so the blades automatically adjust to the chopper's position relative to the platform and do what they would do in real life for the chopper to take on that position. At the same time, they are also connected to the flight sticks in the cockpit, which follow the changes in the rotor blades as the helicopter moves on the platform. The helicopter can also be removed from the platform, with the flight sticks used to control the blade pitch directly.

A fifth motor inside the helicopter is used to power the rotors and to raise or lower the landing wheels, with a transmission ring switching between the two functions. The rotor geartrain uses a unidirectional ratchet similar to 9396, which ensures that the rotor blade angles always correspond to the right positions. The tail rotor spins at a 25:9 ratio with the main rotor.

Some other facts:

- The collective movement of the swashplate is based on the fact that the white 5.5L axles have weaker clutch power than most other axles, so the grooved ball can slide over it with little friction.
- The remote has a 4-way stick for the pitch and roll controls, built on top of a steering arm with a ball joint receptacle.
- The model uses mostly classic Technic parts but several modern 16t gears. Using only the old ABS 16t gears wears down the teeth and a fine powder appears on them after a while, while alternating between the modern and old ones (or using modern ones only) in a geartrain prevents this.
- Yes, the minifig is supposed to be controlling it. :)

See video here:
http://www.youtube.com/watch?v=6T6_LgpfIqw