DESIGN AND DEVELOPMENT OF THE MODEL 412 HELICOPTER

Using multibladed rotor technology developed with the Model 654 rotor, a four-bladed, soft-inplane rotor system has been developed for the Model 212 helicopter. The new rotor was designed to permit an increase in the allowable gross weight of the 212 and to eliminate airspeed restrictions caused by vibrations and rotor loads. The four-bladed system was chosen in lieu of a new two-bladed rotor/nodal beam combination because fewer fuselage modifications were required and retrofit was easier. In eight months of developmental flying, the Model 412, as the new configuration is designated, has accumulated over 200 flight hours, including high altitude and cold weather tests. Measurements during the preliminary flight load survey to speeds of 162 knots and maneuvers to 2.3g indicate the design objectives have been achieved. Predicted weight and performance improvements have been verified, and the helicopter is ready for FAA certification testing. This paper summarizes the development tests and reviews the results in light of Model 412 program goals and objectives.