refined and the concept was on solid ground, I felt there had to be more to the story. The only production helicop­ ters utilizing NOTAR®


and learn more about the tech­


are built by MD.


Having spent a career flying aircraft with conventional TRs (tail rotors), an invitation from MD to come fly with NOTAR®


nology was irresistible. According to MD, 20% of accidents /


incidents are related to the TR via com­ ponent failure, TR strikes, and LTE (Loss of TR Effectiveness). They also state that NOTAR®


is 30% quieter than most


conventional TRs. With its recent gross weight increase to 6,770 lbs. (3,070 kgs.), twin P&W 207E engines, and large aft cabin, the MD 902 Explorer seems to be the perfect fit for the light twin­engine EMS helicopter market. The added safety margin of NOTAR®


,


and lower noise signature, are icing on the cake.


HOW IT WORKS Using natural characteristics of heli­


copter aerodynamics, the NOTAR® sys­


tem provides safe, quiet, responsive, FOD­resistant directional control. An enclosed variable­pitch, composite­ blade fan produces a low pressure, high volume of ambient air to pressurize the composite tail boom. The air is expelled through two slots,


which run the length of the tail boom on the starboard (right) side, causing a boundary­layer control called the "Coanda Effect". The result is that the tail boom becomes a "wing", flying in the down­ wash of the rotor system, producing up to 60 percent of the anti­torque required in a hover. A rotating direct jet thruster accomplishes the balance of the directional control. In forward flight, the vertical stabilizers provide the majority of the anti­torque, howev­ er directional control remains a func­ tion of the direct jet thruster. The NOTAR®


anti­torque system eliminates


all of the mechanical disadvantages of a tail rotor, including long drive shafts, hanger bearings, intermediate gear­ boxes and ninety­degree gearboxes.


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