Experimental modal analysis of a rotating tendon-loaded helicopter blade demonstrator

A novel concept which uses an internal tendon to apply a compressive force on the blades for resonance avoidance of rotorcraft, so-called ‘active concept’, was put forward recently. This research enhances active further toward its basic experimental validation in rotating operational conditions. To progress this direction, new fully dynamically instrumented demonstrator combined with displacement-based axial load application system is developed and assessed experimentally non-rotating conditions rotor speeds ranging from 0 rpm 500 loads N N. The identified modal dynamics used validate comprehensive reduced-order model subsequently support interpretation results where applied methods lacked resolution range. It observed that features anticipated form centrifugal stiffening softening beam-dominated modes, whilst tendon-dominated modes display rapid effects loads. As result these opposing trends, interactional phenomena such as veering are model-predicted results. One consistently mode extend range observations beyond those supported by models damping characterisation throughout interactions complex strain analysis. presented work confirm behaviour suggest systems can be influenced through controllable preloads state rotation. Additional vibration control opportunities arise emergent tunable between primary beam or blade secondary augmented preload system.