ANC20LA089

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.

On September 6, 2020, about 0905 Alaska daylight time, a Eurocopter AS350 B3, N354PA, was substantially damaged when it was involved in an accident near Fort Greely, Alaska. The pilot and one crew member were not injured. The helicopter was operated as a Title 14 Code of Federal Regulations Part 91 ferry flight. The pilot reported that 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 left passenger door vacated the helicopter. 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. The pilot added that the door had not been used other than to check it for security for preflight purposes and was checked by both himself and the mechanic by habit before flight. Airbus Helicopters has two Alert Service Bulletins (ASB) in response to sliding cabin door separations on AS350-B3 model helicopters, ASB No. AS350-52.00.53 and ASB No. AS350-52.00.54. Compliance with ASB No. AS350-52.00.53 results in the addition of a label on the sliding cabin door and states in part: Airbus Helicopters was informed that the LH rear support that attaches the rear intermediate roller of the sliding door was found cracked. After investigation, it was confirmed that pushing on the rear part of the rear support was the root cause of the crack appearance. Airbus Helicopters thus makes it mandatory not to push on the rear part of the LH and/or RH rear support covers when closing the door. Compliance with this ALERT SERVICE BULLETIN consists in checking the LH and/or RH rear supports to make sure that there are no cracks, before adding a label that prohibits any pushing in this area. The ALERT SERVICE BULLETIN is to be complied within 6 months from receipt of the ALERT SERVICE BULLETIN that was issued on 06-18-2020. ASB No. AS350-52.00.54 covers the inspection of the upper rail and roller of the left and/or right cabin sliding doors and states in part: The purpose of this ALERT SERVICE BULLETIN is to make sure that the upper rail and roller of the LH and/or RH sliding doors device are in good condition. Compliance is mandatory. The reason for the ALERT SERVICE BULLETIN was the loss of a door that was locked in the open position during flight, the analyses of the degradations found on the fixed parts of the helicopter and on the sliding door indicated that the loss of the sliding door resulted from the disengagement of the roller from the upper rail, which led to the separation of the door. The ALERT SERVICE BULLETIN is stated to need to be complied with by either 165 flight hours or 13 months and 6 days (the first limit reached is applicable). The ALERT SERVICE BULLETIN was issued on 06-18-2020. The last event that led to the release of the SIN 3441-S-52 was in 2019 with a loss of a sliding door. Airbus Helicopters reported they are aware of 11cases of sliding door loss events over the past 28 years and reported the reasons for those loss of doors was for maintenance (incorrect installation/check) or operational (incorrect lock of the door) reasons. The operator reported that the ASBs from the helicopter manufacturer regarding the cabin doors had not been complied with prior to the accident. A Federal Aviation Administration aviation safety inspector examined the helicopter. He noted the door rollers were displaced and were not recovered, and a partial slide piece on the lower rail was not recovered either. He added that the door hinges all looked normal, minus the two areas where the door slides had separated. He also stated that two witnesses confirmed the cabin door was closed prior to the takeoff. A post-accident examination of the door indicated that the latches and locking finger were found undamaged. The rubber seal around the door was perforated at the locking finger level. It was noted there was a cargo box in the cabin that was close to the door, and the cargo box had witness marks (white marks) corresponding to contact with the door. There was no visible damage to the forward upper fitting rail; the lower forward fitting was found deformed; the aft median rail showed deformation; and the lower rail also showed interference. Airbus helicopters 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.