Fuselage dynamic features of skid helicopter ground resonance

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Journal of Vibration and Shock ›› 2019, Vol. 38 ›› Issue (21) : 216-220.

WU Jing HU Guocai LIU Xiangyi

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Abstract

A finite element (FE) model of helicopter fuselage supported by skid landing gear was established to study effects of non-proportional damping on fuselage dynamic features of a skid helicopter with damper.The FE calculation methods for helicopter fuselage natural frequencies and equivalent mass, stiffness, and damping from fuselage to rotor center were derived.Complex eigenvalues of the equivalent proportional damping system and the actual non-proportional damping system were the same.The effects of non-proportional damping on fuselage modal frequency and damping were analyzed.It was shown that due to non-proportional damping, modal frequencies increase with increase in damper’s damping; when damper’s damping is larger, modal damping may be decreased to be unfavorable to stability of helicopter ground resonance; after considering the nonlinear relation between damper’s damping and its velocity, fuselage modal frequencies increase firstly and then decrease with increase in damper velocity; modal damping doesn’t change according to variation trend of damper’s damping with variation of damper velocity, it may have a process with 2 increases and one decrease; modal damping has 2 peak values, one appears before damper constant pressure valve opening and one does after.

Key words

helicopter / skid landing gear / hydraulic damper / ground resonance / natural frequency / modal damping / non-proportional damping

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WU Jing HU Guocai LIU Xiangyi. Fuselage dynamic features of skid helicopter ground resonance[J]. Journal of Vibration and Shock, 2019, 38(21): 216-220

References

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