In 1988, McDonnell Douglas announced development of a new light twin-engine eight-place helicopter. Prior to receiving the designation of MD 900, this helicopter was known as the MDX. This helicopter is a joint effort with a number of international partners and is a brand new design that incorporates numerous technological advancements. Among these are the NOTAR tail for directional control and a low noise signature, extensive use of composites and a bearingless main rotor. Shortly after the MD 900 received certification, an upgrade was announced with various performance improvements, as well as Category A certification. This improved model is the MD 902. All improvements were available for retrofit on the MD 900.
The NOTAR is a patented method of directional control that was flown in prototype form in 1981 on a U.S. Army OH-6 test bed. The NOTAR uses cool, low-pressure air emerging through two Coanda slots on the side of the tail boom, as well as through steering louvers, to obtain directional control. The air blown through the Coanda slots counters the main rotor torque. The steering slots at the end of the tail boom provide the directional control and movable fins mounted on the horizontal stabilizer also assist. An engine-driven variable pitch fan at the head of the large hollow tail boom supplies the low-pressure air. This method of directional control has two significant advantages: first, it eliminates the tail rotor; and second, it is much quieter. The Army test program was successfully concluded in 1986. The first two commercial applications of the NOTAR technology were the MD 520N and the MD 900.
The MD 902 is a light twin-engine turbine helicopter. It uses a five-bladed, bearingless rotor with composite blades. The transmission is a new design and is approved for dry running for 30 minutes at 50 percent power. The engines used are the Pratt & Whitney Canada PW 206E with FADEC. A NOTAR system provides directional control and the fuselage is constructed of composites and rests on a skid gear. The cabin is divided into two compartments—the forward pilot compartment seats two on energy attenuating seats and the passenger cabin seats six in two facing rows of three energy-attenuating seats. The aft fuselage has a clamshell door that provides access to the baggage compartment and the entire cabin, if desired. Alternatively, the cabin will accommodate one or two stretchers and one or two medical attendants.
The first flight of the MD 900 took place in 1992 and certification to the standards of FAR 27 was received in 1994. JAA certification was obtained in 1996. The MD 902 was announced in 1996 and certification, including IFR and Category A, was obtained in 1997. Deliveries started the same year and the 902 is currently in production.
