Magnetorheological fluid and elastomeric lag damper for helicopter stability augmentation

The feasibility of utilizing a composite magnetorheological fluid plus elastomeric (MRFE) damper is assessed. To emulate the loading conditions for a helicopter lag damper, the MRFE damper emulation was subjected to single frequency (lag/rev) and dual frequency (lag/rev and 1/rev) sinusoidal loading, and equivalent viscous damping was used to compare the MRFE damping characteristics with a conventional elastomeric damper. The preliminary MRFE damper showed nonlinear behavior damping was reduced as displacement amplitude increased. Upon application of a magnetic field, the damping level was controlled according to a specific damping objective as a function of the excitation amplitude. Under dual frequency conditions, damping degradation at lag frequency due to 1/rev motion was also mitigated by magnetic field input to the MR damper.