NOTAR - Concept

Concept

Although the concept took over three years to refine, the NOTAR system is simple in theory and works to provide some directional control using the Coandă effect. A variable pitch fan is enclosed in the aft fuselage section immediately forward of the tail boom and driven by the main rotor transmission. This fan forces low pressure air through two slots on the right side of the tailboom, causing the downwash from the main rotor to hug the tailboom, producing lift, and thus a measure of directional control. This is augmented by a direct jet thruster and vertical stabilisers.

Benefits of the NOTAR system include increased safety (the tail rotor being vulnerable), and greatly reduced external noise. NOTAR-equipped helicopters are among the quietest certified helicopters.

  • 1 Air intake 2 Variable pitch fan 3 Tail boom with Coandă Slots 4 Vertical stabilizers 5 Direct jet thruster 6 Downwash 7 Circulation control tailboom cross-section 8 Anti-torque lift

  • Diagram showing the movement of air through the NOTAR system.

  • MD 900

  • Aerotécnica AC-14, Ducted exhaust and rudders detail

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