The H-76 FANTAIL Eagle anti-torque system helicopter was jointly developed by Boeing Helicopters and Sikorsky Aircraft as a part of the risk reduction effort associated with their light helicopter (LH) design. The LH contract was awarded to the Boeing Sikorsky ""FIRST TEAM"" on April 5, 1991. The LH will be called the ""Comanche."" The aircraft will be referred to as the RAH-66. The FANTAIL was flight tested on a modified Sikorsky H-76 Eagle aircraft that had its tail rotor assembly replaced with a ducted fan design. This paper will discuss the H-76 FANTAIL demonstrators schedule, design, flight test results, and its weight and balance. The ""before and after' aircraft weight empty will be compared. Weight estimating techniques for determining FANTAIL component weights will be presented and compared to the actual aircraft component weights. The demonstrator represents a non-optimized proof of concept type configuration. Weight projections for an advance technology FANTAIL design are presented in order to show the relative comparison for advanced tail rotor designs.