No Tail Rotor

A helicopter that does not have a tail rotor. This technology was first developed by McDonnell Douglas Helicopters. In this system, instead of a tail rotor, a large fan is used at the beginning of the tail boom, which sends a large volume of low-pressure air to the end of the tail boom. In the middle of the tail boom, there are two relatively long and downward grooves through which part of the air driven by the fan passes and create two boundary layers around the tail boom and create the Coanda effect, at this time a part of the air that is pushed downwash by main rotor is attached and stick to the boundary layers , which creates anti-torque force.
A rotating drum in is also designed at the end of the tail, which adjusts the thrust direction and rotation of the tail to achieve the directional yaw control.
This rotating cylinder, called the " direct jet thruster", is attached to the cockpit pedals, and the pilot changes the tail direction by pressing the pedals. 
Advocates of NOTAR believe the system offers quieter and safer operation over a traditional tail rotor.