Primary finding
Probable cause
The inflight collision with debris during takeoff.
Investigator assessment
Analysis narrative
The pilot reported that shortly after he lifted off from a helipad, a window dislodged from a nearby hangar door and impacted the helicopter’s main rotor blade from behind, which in a loss of lift and an excessive vibration. The pilot initiated an emergency landing and subsequently landed hard. One of the main rotor blades was substantially damaged. The pilot reported that there were no preimpact mechanical malfunctions or failures with the helicopter that would have precluded normal operation.