This paper presents the design and preliminary control of an indoor coaxial helicopter ”CoaX” based on a concept of hybrid active and passive control. The robot is capable of passive roll and pitch stabilization against small disturbances while actively stabilizing the yaw and the altitude. We achieve omnidirectional horizontal motion by shifting the center of gravity. The structure is made out of lightweight polyurethane and carbon ffber. Preliminary tests show that ”CoaX” is able to hover for short moments and the lateral control is effective.