The operator, Southern Airways Express, reported the following. Flight 246 from Washington Dulles International Airport (IAD), Dulles, Virgina to Lancaster Airport (LNS), Lancaster, Pennsylvania, departed from runway 30. During the initial climb after takeoff, about 600 ft above ground level, the flight crew noticed that the standby power light in the cockpit illuminated. Shortly thereafter, there was a sudden, shattering noise and vibrations coming from the engine area.
The pilot, who was at the controls, instructed the copilot to declare an emergency and initiate procedures to return to IAD. During the turnback, it became evident that the engine was unresponsive and the airplane was rapidly losing altitude. The pilot made the decision to land the airplane on highway 606, near the perimeter of IAD. During the landing, the airplane touched down on the paved surface of the road and collided with a steel guardrail before coming to a stop. The flight crew secured the airplane and the crew and passengers were met by first responders.
NTSB Preliminary Incident Report - N1983X