Dynamic Stability of Low Effective Flap Hinge BMR Concepts

A wind tunnel test has been conducted to determine the feasibility of a five percent effective flap hinge offset and to establish the aeroelastic stability of this new development in the Bearingless Main Rotor concept. Two configurations: a dual beam and a single flex strap, were examined in this program. Testing was conducted in hover and in forward flight to examine the total flight regime. A five percent effective flap hinge offset was achieved and an acceptable level of stability was demonstrated. The addition of an elastomeric damping layer proved very successful by increasing the measured stability. Further development of this concept must be pursued to capitalize on the reduced weight and part count and advancement of technology development.