Eurocopter AS 350 N354PA accident near Fort Greely, Alaska

Probable cause

Failure of the door lock due to interference between the door and a cargo box.

NTSB analysis

While in cruise flight, at about 700 ft above ground level and 110 kts, a “sudden loud bang” and associated left yaw was experienced as the sliding left side cabin door vacated the helicopter from the closed position. The door impacted a main rotor blade during the separation sequence, which resulted in substantial damage. Subsequently an emergency landing was made to a nearby grass area with no further incident.

Airbus Helicopters has two Alert Service Bulletins (ASB) out for the cabin doors on the AS350-B3. The operator reported that the ASBs from the helicopter manufacturer regarding the cabin doors had not been complied with prior to the accident.

During a post-accident examination, the FAA inspector reported that he was not able to find any definitive reason for the departure of the door. He added that the door rollers were displaced and were not recovered, and a partial slide piece on the lower rail was not recovered either. Since the door rollers were not recovered, they were not able to be examined, and therefor their condition and function could not be tested.

Airbus Helicopters has two Alert Service Bulletins (ASB) published in response to door seperations that occurred as a result of door roller failures on AS350-B3 helicopters. The operator reported that these ASBs had not been complied with prior to the accident. Because the affected components were not recovered, the investigation could not determine if compliance with these ASBs could have prevented the accident.

Airbus noted that the damage was consistent with the door lock not being effective due to the presence of a cargo box that was stored in the cabin that interfered with the door, which resulted in the door opening and separating in flight due to the interference load introduced by the cargo box in the cabin.

Although some affected components were not recovered and examined, the accident is consistent with the door lock failing inflight, likely due to interference between the door and the cargo box.

Text from the NTSB. Open the NTSB docket for ANC20LA089 for the full record.