On June 4, 1988, a Fairchild Hiller FH-1100 (registration N53EP) was involved in an aviation accident near Lihue, HI. Investigators recorded the probable cause as: FATIGUE FAILURE OF THE ENGINE TO TRANSMISSION DRIVE SHAFT ENGINE COUPLING DUE TO AN ANGULAR MISALIGNMENT OF THE DRIVE SHAFT. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During cruise flight, the engine stopped driving the rotor system due to a ruptured Bendix coupling. The pilot performed an autorotation and landed hard on a reef in shallow water. Metallurgical examination found a fatigue fracture in the coupling disk.
Event Summary
The pilot reported that the aircraft was in normal cruise flight when the engine ceased driving the rotor system. The pilot entered an autorotation and extended the glide slightly to reach a suitable landing area on an offshore reef. The helicopter made a hard landing on the reef in approximately one foot of water.
Investigation Findings
On-site examination by FAA airworthiness inspectors revealed that the Bendix coupling on the engine-to-transmission shaft had ruptured at the engine end of the shaft. Metallurgical analysis of the failed coupling identified a fatigue fracture oriented circumferentially on the coupling disk.
Maintenance Background
The drive shaft couplings are subject to a recurring Airworthiness Directive (AD) that mandates alignment measurements of the drive shaft every 100 hours. The last alignment check was performed approximately 60 hours before the accident.
What happened in the 4 Jun 1988 Fairchild Hiller FH-1100 accident near Lihue, HI?
During cruise flight, the engine stopped driving the rotor system due to a ruptured Bendix coupling. The pilot performed an autorotation and landed hard on a reef in shallow water. Metallurgical examination found a fatigue fracture in the coupling disk.
What aircraft was involved and where did it happen?
The accident on 4 Jun 1988 involved a Fairchild Hiller FH-1100, registration N53EP, at Lihue, HI.
What was the probable cause of the accident?
FATIGUE FAILURE OF THE ENGINE TO TRANSMISSION DRIVE SHAFT ENGINE COUPLING DUE TO AN ANGULAR MISALIGNMENT OF THE DRIVE SHAFT.
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