Preliminary data based on the notification from the United States authorities:
While in cruise at about 2,000 mean sea level, noticed a low rotor rpm warning horn with no associated caution light. The crew noted a decrease in turbine and main rotor speed, and pilot was able to maintain engine speed with collective at 7 on First Limit Indicator (FLI). The pilot decided to make an precautionary landing because the engine and main rotor speed continued to decrease; however, while on final approach to a suitable field the main rotor speed further decreased and autorotation was made into a residential backyard short of the intended field.
And on final approach Rotor Speed drooped further during entry into auto‐ rotation and landed in residential area short of first selected field. The main rotor struck the tail boom, the fenestron struck the ground, and the main landing gear skids were displaced.