At the conclusion of an evaluation flight, the left seat pilot taxied the airplane to the hangar area under the direction of the right seat pilot. After reaching the hangar area, the left seat pilot initiated a 180-degree turn in order to better position the airplane for post-flight ground handling. During the turn, the right side of the horizontal stabilizer struck one of the hangar’s support beams, resulting in substantial damage to the horizontal and vertical stabilizers, as well as the empennage. Following the accident, the operator instituted a new policy dictating that they will utilize the aid of an external spotter when maneuvering in the vicinity of obstacles.