What happened
On July 4, 2010, at approximately 0309 EDT, a Eurocopter AS365N3 helicopter, registration N520CF, was performing an emergency medical services transport flight near Dayton, Ohio. The aircraft was en route from Lebanon-Warren County Airport (I68) to an accident scene near Huber Heights, Ohio, under visual meteorological conditions.
During the cruise phase of flight, the pilot dropped a flight manual inside the cabin. The manual struck the right front passenger door jettison handle. Although the handle was secured with safety wire, the required protective guard was not installed on the mechanism. The impact caused the handle to rotate rearward, breaking the safety wire and disengaging the upper pin of the center door. While the middle and lower pins remained engaged, the window bent outward and separated from its frame, subsequently striking the horizontal stabilizer.
The pilot aborted the mission and landed at Moraine at 0313 local time. All 3 occupants were not injured.
The investigation
Investigators examined the helicopter's door jettisoning system, which is designed to release door pins via a handle protected by a breakable cover and snapwire. The maintenance manual for the aircraft specifies that doors must be inspected every 600 flight hours or every two years, and explicitly requires the installation of a "Plexiglas protective cover" during reinstallation.
Evidence showed that the required Plexiglas guard (part number 365A87-3019-87) was missing. The operator stated that maintenance personnel had mistakenly believed a decorative plastic trim piece served as the necessary guard. The aircraft's most recent inspection, which included the area of the jettison handle, had been completed on June 23, 2010.