Serious incident Swearingen SA227-AC Metro III N191AF, Saturday 29 October 1994
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Date:Saturday 29 October 1994
Time:07:45 LT
Type:Silhouette image of generic SW4 model; specific model in this crash may look slightly different    
Swearingen SA227-AC Metro III
Owner/operator:Ameriflight
Registration: N191AF
MSN: AC-491
Year of manufacture:1981
Total airframe hrs:22395 hours
Engine model:GARRETT TPE-331-11U
Fatalities:Fatalities: 0 / Occupants: 1
Other fatalities:0
Aircraft damage: None
Category:Serious incident
Location:Oakland, CA -   United States of America
Phase: Initial climb
Nature:Unknown
Departure airport:(KOAK)
Destination airport:Reno, NV (KRNO)
Investigating agency: NTSB
Confidence Rating: Accident investigation report completed and information captured
Narrative:
THE PILOT EXPERIENCED A LOSS OF AILERON CONTROL SHORTLY AFTER TAKEOFF. THE PILOT RETURNED TO THE AIRPORT AND LANDED WITHOUT FURTHER INCIDENT. EXAMINATION OF THE AIRPLANE REVEALED THE CABLE BROKE NEAR ITS 90-DEGREE ATTACH PULLEYS. THE SAFETY BOARD MATERIALS LABORATORY CONDUCTED A METALLURGICAL EXAMINATION OF THE CABLE'S FRACTURED SURFACES. THE EXAMINATION REVEALED THE CABLE SEPARATED DUE TO HIGH-STRESS/LOW-CYCLE FATIGUE CRACKING. MOST WIRE ENDS IN THE VICINITY OF THE SEPARATION WERE SEVERELY BENT. SUCH DAMAGE WOULD MOST LIKELY BE PRODUCED BY A KINK IN THE CABLE. A CABLE KINK CREATES VERY HIGH TENSILE STRESSES ALONG THE OUTSIDE OF THE KINK AND WOULD GENERATE PREMATURE HIGH-STRESS FATIGUE CRACKING. THE 15 HOURS OF TIME SINCE INSTALLATION IS CONSISTENT WITH SOME SORT OF SEVERE CONDITION SUCH AS A KINK. THE MECHANIC MOST LIKELY INSTALLED THE CABLE WITH ONE END TWISTED COMPARED WITH THE OTHER END.

Probable Cause: the company maintenance personnel's improper installation of the aileron cable.

Accident investigation:
cover
  
Investigating agency: NTSB
Report number: LAX95IA027
Status: Investigation completed
Duration: 11 months
Download report: Final report

Sources:

NTSB LAX95IA027

Revision history:

Date/timeContributorUpdates
15-Mar-2024 12:51 ASN Update Bot Added

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