Design of the BK 117 medium twin-engine helicopters was started in 1977 as a joint effort between MBB GMBH in Germany and Kawasaki Heavy Industries in Japan. MBB (now Eurocopter) had responsibility for design and manufacturing of the dynamic system, the tail boom, landing gear, and various systems integration. Kawasaki had responsibility for the fuselage, transmission and various systems. Final assembly was at two locations, one at Donauworth, Germany, and one at Gifu, Japan.
It is an 8- to 11-place medium twin-engine turbine helicopter that is characterized by a large combined passenger cabin and luggage compartment that extends the full length of the fuselage. Clamshell doors at the back of the fuselage allow access to this combined passenger and luggage compartment that has an unobstructed length of over 9 feet. The standard seating configuration has a pilot and one passenger seat up front and two or three rows of three seats in the back. Alternatively, two litters can be loaded through the clamshell doors and placed side by side on the flat floor. In this configuration, there is also room for two or three medical attendants.
The drivetrain of the BK 117C1 uses two Turbomeca Arriel 1E2 engines and a rigid, hingeless, four-bladed rotor based on the Bo 105 design. The main rotor blades are made of composite construction, as are the two tail rotor blades. The tail rotor is mounted at the top of the vertical fin, which provides unobstructed access to the rear clamshell doors. The primary fuselage structure is constructed of aluminum alloy. Secondary fuselage structures are made of Kevlar and other composites.
The first flight of the BK 117 took place in 1979 and certification to the standards of FAR 29 was obtained in 1983. Certification for Category A operations and single-pilot IFR operations was also obtained. First deliveries were made in 1983. The BK 117 C1 was certificated in 1992 and was in production until 2003.