On September 1, 1987, a Hiller UH-12E (registration N236HA) operated by San Tan Dusters Inc. was involved in an aviation accident near Scottsdale, AZ. Investigators recorded the probable cause as: The helicopter's collision with terrain due to the failure of the main rotor hub, which resulted from high-cycle fatigue that originated at a point in the hub pin bore where intergranular corrosion had occurred. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter suffered a catastrophic main rotor hub failure during an aerial application flight, resulting in a collision with terrain due to intergranular corrosion.
What happened
The accident occurred while the pilot was conducting an aerial application flight. The aircraft was engaged in agricultural operations when the pilot initiated a turn-around maneuver. As he began to prepare for another swath run, he reported hearing a loud bang. Immediately following this event, the helicopter lost control and collided with the terrain.
The investigation
A subsequent inspection of the main rotor head and pin assembly revealed that the hub had failed due to high-cycle fatigue. Further analysis determined that the fatigue originated from a specific point within the hub pin bore. This failure was exacerbated by intergranular corrosion present at that location.
Findings
The mechanical failure of the main rotor hub was the primary factor in the accident. The root cause was identified as high-cycle fatigue originating from intergranular corrosion in the hub pin bore.
Probable cause
The helicopter's collision with terrain due to the failure of the main rotor hub, which resulted from high-cycle fatigue that originated at a point in the hub pin bore where intergranular corrosion had occurred.
What happened in the 1 Sept 1987 Hiller UH-12E accident near Scottsdale, AZ?
A helicopter suffered a catastrophic main rotor hub failure during an aerial application flight, resulting in a collision with terrain due to intergranular corrosion.
What aircraft was involved and where did it happen?
The accident on 1 Sept 1987 involved a Hiller UH-12E, registration N236HA, operated by San Tan Dusters Inc., at Scottsdale, AZ.
What was the probable cause of the accident?
The helicopter's collision with terrain due to the failure of the main rotor hub, which resulted from high-cycle fatigue that originated at a point in the hub pin bore where intergranular corrosion had occurred.
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