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ASN Wikibase Occurrence # 184043
Last updated: 19 September 2020
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Time:14:56 LT
Type:Silhouette image of generic B105 model; specific model in this crash may look slightly different
MBB Bo 105CBS-5
Owner/operator:Sejin Aviation
Registration: HL9617
C/n / msn: S-874
Fatalities:Fatalities: 1 / Occupants: 1
Other fatalities:0
Aircraft damage: Written off (damaged beyond repair)
Location:Moak-mountain, Geumsan-myeon, Gimje-si -   South Korea
Phase: Approach
Nature:Fire fighting
Departure airport:RKTA
Destination airport:Geumsan-ri 112, Geumsan-myeon, Gimje-si, Jeonlabookdo, South Korea
Investigating agency: ARAIB
A privately owned firefighting helicopter, hired by local government of Jeolla province (Jeollabuk-do) to observe forest fires, crashed in a forest near a temple on a mountain after rotating several times before it impacted the mountainside. The pilot (61) died in the crash.

In the morning of crash, at 08:50 a.m., captain(pilot) of Sejin Aviation submitted and approved the flight plan: Flight purpose: forest fire monitoring; Departure point: Taean airfield(RKTA), Landing point: Geumsan-ri 112, Geumsan-myeon, Gimje-si, Jeonlabookdo.

Captain of accident helicopter arrived to office of Taean airfield at 08:30 a.m. using his car and prepared the flight plan up to 12:00 p.m. And captain performed the external check of helicopter at hangar and apron to 14:15 p.m., without finding any defects. Maintenance worker also performed the check with pre-flight inspection checklist and don't find any problems or defects.

After the pre-flight inspection, the aircraft logbook for the aircraft should be filled out or signed according to Article 124 (Aviation Log) of the Enforcement Regulations of the Aviation Act, but there was no sign of the mechanic or pilot.

HL9617 took off from Taean airfield at 14:15 and flwon to the Moaksan Park via Galsan, Boryeong, Dongseo-chun, and Dongsan-gun. HL9617 arrived the Moaksan Park at 14:50. Shortly before landing, at 30~40m altitude, HL9617 suddenly performed 360-degree turn about 10 times, and crashed into mountain vertically after lost its balance.

After investigation, it has been established that maintenance worker assembeld the tailrotor gearbox without fixing screw in the T-bolt.

Cause (computer translation from Korean report, assisted by native Korean)
1. Due to improper maintenance, the T-bolt of the tail rotor was fallen apart from the HL9617 so bell crank and pitch control sleeves were separated, resulting in a loss of directional controllability and subsequent crash.
2. In addition, when the HL9617 lost its directional controllability during flight, the captain could not perform the appropriate emergency procedure.

As a contributing factor to this accident,
1. Sejin Aviation has performed inadequate maintenance such as installing an unusable gear box due to loss of airworthiness and failing to confirm the tightening of the T-bolt fixing screw.
2. Sejin Airline was unable to carry out proper emergency procedures in case of emergency due to insufficient emergency training for pilots.

Sources: (photos)
AZ: BFU16-0094-DX

Accident investigation:
Investigating agency: ARAIB
Status: Investigation completed
Duration: 2 years 1 month
Download report: Final report


Photo of tail, South Korea ARAIB

Revision history:

30-Jan-2016 08:13 gerard57 Added
30-Jan-2016 08:21 harro Updated [Aircraft type, Registration, Total fatalities, Total occupants, Other fatalities, Source, Damage]
30-Jan-2016 08:58 gerard57 Updated [Nature, Source, Narrative]
30-Jan-2016 11:51 CTYONE Updated [Registration, Cn]
30-Jan-2016 13:53 Aerossurance Updated [Time, Aircraft type, Cn, Operator, Narrative]
30-Jan-2016 15:31 Black Typhoon Updated [Time, Aircraft type]
30-Jan-2016 18:05 TB Updated [Aircraft type, Cn, Operator]
22-Sep-2016 09:43 Aerossurance Updated [Time, Operator, Source, Narrative]
09-Oct-2016 15:55 TB Updated [Operator, Narrative]
11-Oct-2016 16:18 TB Updated [Time, Operator, Location, Phase, Source, Narrative]
11-Oct-2016 16:32 TB Updated [Location, Source, Narrative]
11-Oct-2016 19:26 TB Updated [Operator]
29-Mar-2018 19:39 harro Updated [Narrative]
19-Sep-2018 18:52 Anon. Updated [Location, Departure airport, Destination airport, Narrative, Photo]
10-Dec-2018 18:36 TB Updated [Location]

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