Loss of control Accident Bell 206-L4 N720RL,
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ASN Wikibase Occurrence # 289991
 
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Date:Thursday 6 June 2013
Time:10:15 LT
Type:Silhouette image of generic B06 model; specific model in this crash may look slightly different    
Bell 206-L4
Owner/operator:T
Registration: N720RL
MSN: 52027
Year of manufacture:1993
Total airframe hrs:7133 hours
Engine model:Rolls Royce 250-30 SER
Fatalities:Fatalities: 0 / Occupants: 2
Aircraft damage: Substantial
Category:Accident
Location:Abbeville, Louisiana -   United States of America
Phase: Manoeuvring (airshow, firefighting, ag.ops.)
Nature:Cargo
Departure airport:Abbeville, LA (KIYA)
Destination airport:Abbeville, LA (KIYA)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
The helicopter was on its first flight after extensive maintenance. As the pilot approached a canal at an altitude of about 20 feet, he heard a noise and then a loud "pop." The helicopter then started to spin to the right and the pilot was unable to stop the spin. After about two revolutions, the pilot reduced engine power to idle, and the helicopter collided with terrain and water.

Examination of the helicopter revealed that the connection between the tail rotor drive shaft and the tail rotor gear box was partially separated. Of the two bolts that connected the drive shaft to the coupling on the gear box, one remained secured by its associated nut; however, the other bolt had backed out of the drive shaft, but remained in the coupling, and its corresponding nut was missing. The helicopter had accrued about 0.7 flight hours since its most recent maintenance, which included removing and reinstalling the tail rotor gear box. It is likely that the maintenance personnel did not ensure adequate torque of a tailrotor drive shaft coupling bolt, which allowed it to be back out of the drive shaft.

Probable Cause: Failure of maintenance personnel to ensure adequate torque of a tailrotor drive shaft coupling bolt, which resulted in the partial disconnection of the drive shaft.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: CEN13LA321
Status: Investigation completed
Duration: 5 months
Download report: Final report

Sources:

NTSB CEN13LA321

Location

Revision history:

Date/timeContributorUpdates
06-Oct-2022 06:36 ASN Update Bot Added

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