1964 Hughes flight-tested the XV-9A Hot Cycle research aircraft. To power the helicopter, engine exhaust gases of 1,200 degrees Fahrenheit were forced through the rotor. The experimentalprogram yielded vital information about helicopters that fly without tail rotors -- a development that Hughes pursued further in the late 1970s and early 1980s.
TODAY The result: the NOTAR® anti-torque system, which is in production on the MD 520N, the MD 600N, and the MD Explorer. Helicopters equipped with the NOTAR system have no tail rotors, which makes them the safest and quietest helicopters flying today. They are particularly well suited to serve as air ambulances, in law enforcement, and as scenic-tour vehicles in environmentally sensitive areas.