On March 19, 1987, a Bell 47G (registration N13766) was involved in an aviation accident near Wassaic, NY. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A Bell 47G helicopter crashed after the red main rotor blade separated from the blade grips in flight. Examination revealed that the blade had been repaired non-compliantly years earlier.
Accident Overview
A Bell 47G helicopter was conducting an aerial survey of buried telephone cable when the red main rotor blade separated from the blade grips while in flight. Subsequently, the main rotor hub and the attached main rotor blade separated from the transmission, and the helicopter crashed.
Examination Findings
Investigators found no evidence that the accident involved a blade strike at the time of the event. Examination of the failed main rotor blade disclosed that it had sustained a blade strike years prior. That damage was repaired, and the blade was returned to service. During the examination, a large gap near the blade grips was discovered, which had been filled with epoxy.
Maintenance Non-Compliance
Both the earlier blade strike repair and the filling of the gap with epoxy were determined to be not in compliance with the Bell 47 Maintenance and Overhaul Manual.