Airworthiness Directives; Burkhart GROB Luft-und Raumfahrt GmbH Model G 109B Gliders

This amendment adopts a new airworthiness directive (AD) that applies to certain Burkhart GROB Luft-und Raumfahrt GmbH (Grob) Model G 109B gliders. This AD requires inspecting the elevator and trim tab for water, and assuring that the necessary drain holes are installed and existing drain holes are open. This AD also requires drilling any necessary drain holes and opening any existing drain holes that are closed; and, if a significant amount of water (more than \1/2\ liter) is found in the elevator, assuring that the elevator's weight and residual momentum and the glider's center of gravity (C.G.) are within the limits specified in the flight manual, and adjusting the elevator's weight and residual momentum and the glider's C.G., as needed. This AD is the result of mandatory continuing airworthiness information (MCAI) issued by the airworthiness authority for Germany. The actions specified by this AD are intended to prevent water from penetrating the elevator and trim tab because of inadequate drainage, which could result in a delaminated elevator and trim tab structure with consequent elevator imbalance and flutter.