On November 13, 1993, a Hiller UH-12E (registration N149HA) was involved in an aviation accident near Salinas, CA. Investigators recorded the probable cause as: The main rotor head paddle assembly fracturing and separating due to an overload failure mode during a maneuvering turn while loaded with chemicals. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter suffered a main rotor head fracture during a maneuvering turn while carrying chemicals, leading to loss of control at low altitude due to overload failure.
What happened
The pilot was operating a helicopter loaded with chemical materials when the aircraft lost control. This incident occurred during a maneuvering turn at an altitude of approximately 35 feet above the ground. Prior to the loss of control, the main rotor head paddle assembly fractured and separated from the aircraft.
The investigation
A metallurgical examination was conducted on the fractured components to determine the nature of the failure. The analysis revealed that the fracture exhibited an overload failure mode, indicating that the structural integrity of the rotor head was compromised by excessive stress rather than fatigue or manufacturing defects.
Probable cause
The main rotor head paddle assembly fracturing and separating due to an overload failure mode during a maneuvering turn while loaded with chemicals.
What happened in the 13 Nov 1993 Hiller UH-12E accident near Salinas, CA?
A helicopter suffered a main rotor head fracture during a maneuvering turn while carrying chemicals, leading to loss of control at low altitude due to overload failure.
What aircraft was involved and where did it happen?
The accident on 13 Nov 1993 involved a Hiller UH-12E, registration N149HA, at Salinas, CA.
What was the probable cause of the accident?
The main rotor head paddle assembly fracturing and separating due to an overload failure mode during a maneuvering turn while loaded with chemicals.
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