No-Tail-Rotor helicopter

In the early 1980s, DARPA nurtured the development of No-Tail-Rotor (NOTAR) technologies, resulting in significantly quieter helicopters that could operate with a lower chance of detection. 

DARPAs support helped to show the operational advantages of the NOTAR flying demonstrator led to a NOTAR series of helicopters used by government agencies and the commercial sector. 

The NOTAR system was considered to be the first successful fundamental configuration change to the single-rotor helicopter since the incorporation of the turbine engine in the late 1950s and early 1960s.