Rotorcraft Flying Menu > Introduction to the Helicopter  >Antitorque Systems > NOTAR®

The NOTAR® system is an alternative to the antitorque rotor. The system uses low-pressure air that is forced into the tailboom by a fan mounted within the helicop-ter. The air is then fed through horizontal slots, located on the right side of the tailboom, and to a controllable rotating nozzle to provide antitorque and directional control. The low-pressure air coming from the horizon-tal slots, in conjunction with the downwash from the main rotor, creates a phenomenon called “Coanda Effect,” which produces a lifting force on the right side of the tailboom. [Figure 1-5]

Figure 1-5. While in a hover, Coanda Effect supplies approxi-mately two-thirds of the lift necessary to maintain directional control. The rest is created by directing the thrust from the controllable rotating nozzle.