Semiactive Coulomb Friction Lead-Lag Dampers

Abstract

Lead–lag dampers are present in most rotor systems to provide the desired level of damping for all flight conditions. These dampers are critical components of the rotor system and also represent a weight and drag penalty together with a major source of maintenance costs. The performance of semiactive Coulomb friction based lead–lag dampers is examined in this study. First, conceptual designs of semiactive friction dampers for rotorcraft applications are briefly presented. Next, the concept of adaptive damping is discussed: by adjusting the normal contact force at the frictional interface, the energy dissipation characteristics of the device can be tailored, providing “damping on demand.” The behavior of friction dampers in both ground resonance and forward flight is simulated for the UH-60 aircraft and compared with that of present hydraulic dampers. The approach used for modeling the frictional process is presented in detail. The final part of this paper explores the concept of selective damping, in which the energy dissipation capacity of semiactive devices is targeted to a specific mode. Practical implementation of this concept is shown to face many challenges.