Eurocopter AS365N3 N520CF incident near Dayton, Ohio

Probable cause

The unintentional movement of the jettison handle in-flight due to the pilot’s dropping of a manual that impacted the handle and released the door window, which then impacted the horizontal stabilizer. Contributing to the accident was the jettison handle guard not being installed by maintenance personnel.

NTSB analysis

The emergency medical services transport helicopter sustained minor damage when a door window separated in-flight. The pilot dropped a flight manual during cruise flight that impacted the right center door jettison handle, allowing the window to separate and impact the horizontal stabilizer. The required jettison handle guard was not installed. The helicopter’s maintenance manual directs that the crew and passenger doors be checked every 600 hours of flight time or every two years. The manual requires the following steps to reinstall the doors, "Install the Plexiglas protective cover." Subsequent to the accident, the helicopter manufacturer issued Safety Information Notices which described the incident and reminded mechanics that while performing routine maintenance procedures, in particular assembly procedures, “it is important to strictly comply with all applicable maintenance procedures, including the most basic and simple ones, to ensure proper helicopter performance and flight safety.”

Text from the NTSB. Open the NTSB docket for CEN10IA372 for the full record.