Serious incident Eurocopter AS 350 BA N4010K,
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ASN Wikibase Occurrence # 370261
 
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Date:Wednesday 28 March 2007
Time:11:45 LT
Type:Silhouette image of generic AS50 model; specific model in this crash may look slightly different    
Eurocopter AS 350 BA
Owner/operator:Mauiscapes Helicopters, Inc.
Registration: N4010K
MSN: 2841
Year of manufacture:1995
Total airframe hrs:15794 hours
Engine model:Turbomeca Arriel 1B
Fatalities:Fatalities: 0 / Occupants: 7
Aircraft damage: Minor
Category:Serious incident
Location:Kahului, HI -   United States of America
Phase: En route
Nature:Unknown
Departure airport:Kahului Airport, HI (OGG/PHOG)
Destination airport:(KOGG)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
While in cruise flight at 2,800 feet mean sea level (msl) approximately 100 knots airspeed, the pilot experienced an uncommanded left yaw. The pilot pressed each rotor pedal and "found they were not functioning." The pilot turned back to the airport and declared an emergency. The pilot attempted a run-on landing. During the landing, the helicopter "wanted to turn left as the airspeed slowed." Subsequently, the helicopter twice spun to the left and came to rest upright partially on the runway and adjacent grass. The loss of tail rotor control was due to the lower support yoke arm bushing being loose in the lower support yoke arm. During operation of the tail rotor controls, the looseness transferred the cyclic operational stresses, via the expansion pin assembly, to the upper support yoke arm, which failed in fatigue. Under continued operation, the pitch control input rod then translated upwards into the path of the rotating tail rotor gearbox input flange. The pitch control rod wore down until the input rod no longer transmitted operational forces and it separated with the sequential loss of tail rotor control. During a recent 500-hour inspection, a visual check on the expansible pin was performed; however, only one end of the expansion pin assembly appeared to have been visually checked. The manufacturer's maintenance manual does not specify how the installation check should be performed.

Probable Cause: The loss of tail rotor control due to wear damage to the pitch control input rod that resulted ultimately in the fatigue failure of the upper support yoke arm. Contributing factors were the improper maintenance inspection of the expansion pin assembly and the loose bushing in the lower support yoke arm.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: LAX07IA115
Status: Investigation completed
Duration: 1 year and 3 months
Download report: Final report

Sources:

NTSB LAX07IA115

Revision history:

Date/timeContributorUpdates
25-Mar-2024 08:49 ASN Update Bot Added

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