At about 0935 Pacific time, the helicopter was destroyed after impacting terrain during an uncontrolled descent while maneuvering near Arlington, Wash. The flight instructor and the pilot-rated student sustained fatal injuries. Visual conditions prevailed for the local flight that departed the Arlington Municipal Airport, Arlington, Wash., at approximately 0930. Numerous witnesses saw the helicopter flying over the area before it impacted the ground. One witness reported hearing the helicopter …make a loud bang, then watched it fall from the sky. Another witness reported seeing the helicopter flying north from AWO, …and as it disappeared into the distance I heard a large prolonged shuddery boom, and then no more helicopter engine noise. Debris was observed scattered over an area of approximately 2000 feet in length and 500 feet in width.