On October 12, 1993, a Hughes 269A (registration N7032U) operated by Brooks Aero, Inc. was involved in an aviation accident near Coldwater, MI. Investigators recorded the probable cause as: The tailboom support strut attachment lug failed due to fatigue. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter student pilot executed a successful hovering autorotation after a fatigue-induced failure of the tailboom support strut attachment lug, resulting in loss of directional control.
Incident Overview
During a training flight, a certificated helicopter pilot receiving dual instruction was at the controls while the helicopter was in a hover. Both the student pilot and the certified flight instructor (CFI) reported hearing a sudden bang, immediately followed by a loss of directional control. The student pilot promptly performed a hovering autorotation, which was executed successfully and brought the helicopter to a controlled landing.
Investigation Findings
Post-incident examination revealed the failure of the tailboom support strut attachment lug at the left aft cluster fitting. The failed component was subjected to metallurgical analysis, which determined that the fracture was caused by fatigue cracking. The fatigue initiated and propagated over time until the lug could no longer sustain the operational loads, resulting in the sudden failure.
Conclusion
No other contributing factors were identified. The incident was solely attributed to the fatigue failure of the tailboom support strut attachment lug.
Probable cause
The tailboom support strut attachment lug failed due to fatigue.