MD Helicopters, Inc. (MDHI) today announced its fleet of NOTAR helicopters have clocked more than 1,000,000 flight hours since MDHI’s exclusive NOTAR anti-torque technology was introduced in 1991. MD Helicopters’ MD 520N, MD 600N and MD Explorer helicopters use and validate this technology.
“NOTAR continues to perform to expectation and this is a significant milestone,” said Carl Schopfer, Vice President of Engineering MD Helicopters, Inc. “The technology is still leading-edge even though it has been in the market for some time. Today, no one else can offer this technology at the moment which allows MD Helicopters, Inc. to provide a technologically advanced offering to customers that they cannot obtain anywhere else.”
The NOTAR anti-torque system helps MDHI provide a fleet of the safest, quietest helicopters available. It provides a responsive FOD-resistant directional control system using the natural characteristics of helicopter aerodynamics. An enclosed variable-pitch 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 right side, causing a boundary-layer control called the “Coanda Effect.” The result is that the tail boom essentially becomes a “wing,” flying in the downwash of the rotor system, producing up to 60 percent of the anti-torque required in a hover. The balance of the directional control is accomplished by a rotating direct jet thruster.
In forward flight, the vertical stabilizers provide the majority of the anti-torque; however directional control remains a function of the direct jet thruster. The NOTAR anti-torque system eliminates all of the mechanical disadvantages of a tail rotor, including long drive shafts, hanger bearings, intermediate gearboxes and ninety-degree gearboxes.
NOTAR provides a number of safety advantages as well including no hull damage from tail rotor-related accidents, no dramatic center of gravity shift with loss of gearbox, reduced pilot workload and better concentration on mission, less sensitivity to wind direction, enhanced safety in confined areas, elimination of the danger of an almost invisible tail rotor, and no driveshaft, hangar bearings or 90 degree gear boxes.