High Quality Content by WIKIPEDIA articles! The MD Helicopters MD 600N is a light utility civilian helicopter designed in the United States. It is a stretched eight-seat development of the five-seat MD 520N helicopter.McDonnell Douglas Helicopter Systems first announced it was developing a stretched MD 520N in late 1994, at that time designated the MD 630N.The prototype, a modified MD 530F, had made its first flight on November 22 1994. McDonnell Douglas gave the go-ahead for the production aircraft, redesignated the MD 600N, in March 1995.McDonnell Douglas stretched the MD 520N fuselage by inserting a plug aft of the cockpit/cabin bulkhead and stretching the NOTAR tail boom. The larger fuselage allows for an extra middle row of seats. Other differences compared with the MD 520N include a new six blade main rotor and a more powerful Allison now Rolls-Royce Model 250 turboshaft.