Process Improvements for the Ah-64 Tail Rotor Vibration Analysis : 9781286861424 : 01 Oct 2012 : The Apache was the first helicopter of its kind to fly with the tail rotor blade offset by 55 degrees as opposed to the traditional 90 degrees. Current balancing methods approximate the rotor system as a traditional 4 bladed, same plane system with different weight sensitivity coefficients for each set of blades. The Apache tail rotor computer model was built using the Rotorcraft Comprehensive Analysis System (RCAS) program. The objective was not to develop solutions for the sensitivity coefficients, but to identify predictive trends that result from the tail rotor blade location. Currently, sensitivity coefficients applied to the adjustment algorithms of the Aviation Vibration Analyzer (AVA) processor are broken down into an outer blade coefficient and an inner blade coefficient. Evidence from the computer simulation results computed in this research showed that the sensitivities depended