On April 24, 1984, a Hiller UH-12E (registration N9740C) was involved in an aviation accident near Pocahontas, AR. Investigators recorded the probable cause as: Engine failure during a low-altitude swath run caused by fatigue failure of the dowel pins and screws securing the starter and accessory drive gears, which had sheared after six hours of operation since a major overhaul. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
Aircraft crashed after engine failure during a low-altitude swath run. Investigation revealed sheared dowel pins and screws in the starter drive gear caused by fatigue.
What happened
The aircraft experienced an engine failure while conducting a swath run at an altitude of 20 feet above ground level, resulting in a crash.
The investigation
A post-acc examination of the engine revealed that three dowel pins and six screws securing the starter drive gear and the accessory drive gear had sheared. Metallurgical analysis confirmed that these components failed due to fatigue. At the time of the incident, the engine had been in operation for six hours since its last major overhaul.
Findings
The primary cause was fatigue failure of the fasteners holding the drive gears.
Probable cause
Engine failure during a low-altitude swath run caused by fatigue failure of the dowel pins and screws securing the starter and accessory drive gears, which had sheared after six hours of operation since a major overhaul.
What happened in the 24 Apr 1984 Hiller UH-12E accident near Pocahontas, AR?
Aircraft crashed after engine failure during a low-altitude swath run. Investigation revealed sheared dowel pins and screws in the starter drive gear caused by fatigue.
What aircraft was involved and where did it happen?
The accident on 24 Apr 1984 involved a Hiller UH-12E, registration N9740C, at Pocahontas, AR.
What was the probable cause of the accident?
Engine failure during a low-altitude swath run caused by fatigue failure of the dowel pins and screws securing the starter and accessory drive gears, which had sheared after six hours of operation since a major overhaul.
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