Helicopter rotary and fixed system dynamics during hover and high speed flights

This paper uses linear power spectral analysis to quantify servo-flap helicopter vibratory data measured from multiple locations of the rotor blade system and the fuselage. Vibration is the most important performance index in helicopter design and this paper compares helicopter vibrations during hover and high-speed cruising flights. In particular, we compared vibratory data measured from three locations of the rotating system: servo-flap mid-span bending, rotor blade chord-wise rod axial load, rotor blade flatwise bending and from the fixed system instrument panel and the central gravity of the fuselage in lateral, longitudinal, and vertical directions. Vibratory energy were computed and recorded from the 1^st to the 6^th harmonics of fundamental rotation frequency. The results provided a quantitative delineation of the vibratory behavior of the rotor blade and the fuselage under different flight conditions and, more importantly, allowed us to verify system performance conformed to servo-flap helicopter design specifications during blade tuning process and fault detection testing.