On May 17, 1993, a Fairchild FH-1100 (registration N5060F) operated by Sea Hawk, Inc. was involved in an aviation accident near Malina Bay, AK. Investigators recorded the probable cause as: THE INSTALLATION OF A BOGUS TRANSMISSION TO ENGINE DRIVESHAFT. THE FAILURE OF THE COMPANY MAINTENANCE PERSONNEL TO COMPLY WITH THE SERVICE BULLETINS AND LETTERS WAS A FACTOR. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
Examination of the helicopter revealed a failed engine-to-transmission drive shaft coupling with fatigue fracture surfaces. The original fracture origin could not be determined due to rotational damage. The installed shaft had mismatched stamped numbers and lacked documentation for required maintenance.
Examination Findings
Post-accident examination of the helicopter disclosed that the engine-to-transmission drive shaft coupling on the engine side had failed. Metallurgical analysis of the failed component identified fatigue fracture surfaces; however, because of subsequent rotational damage, the exact origin of the fracture could not be established. The examination also revealed that many of the stamped numbers on the shaft had been peened over and replaced with a different number. Nonetheless, the Bendix data plate remained affixed to the shaft and displayed the part number 19E49-3E.
Records Discrepancy
A review of the helicopter maintenance records indicated that a different serial-numbered shaft was supposed to be installed on the helicopter. The service record for the shaft that was actually installed showed that it had not been in service from July 1978 to March 1992. Furthermore, documentation could not be located to verify that the drive shaft had been maintained in accordance with applicable service letters and bulletins.
What happened in the 17 May 1993 Fairchild FH-1100 accident near Malina Bay, AK?
Examination of the helicopter revealed a failed engine-to-transmission drive shaft coupling with fatigue fracture surfaces. The original fracture origin could not be determined due to rotational damage. The installed shaft had mismatched stamped numbers and lacked documentation for required maintenance.
What aircraft was involved and where did it happen?
The accident on 17 May 1993 involved a Fairchild FH-1100, registration N5060F, operated by Sea Hawk, Inc., at Malina Bay, AK.
What was the probable cause of the accident?
THE INSTALLATION OF A BOGUS TRANSMISSION TO ENGINE DRIVESHAFT. THE FAILURE OF THE COMPANY MAINTENANCE PERSONNEL TO COMPLY WITH THE SERVICE BULLETINS AND LETTERS WAS A FACTOR.
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