On October 11, 1989, a Hiller UH-12E (registration N689SB) operated by West Farm Air Inc. was involved in an aviation accident near Yuma, AZ. Investigators recorded the probable cause as: Separation of the engine torsional coupling rubber mounts, which caused an overspeed that shut down the engine. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
After completing an aerial application operation, a pilot experienced engine RPM decay and performed a precautionary landing. At 100 ft, total power loss occurred; autorotation flare was too high, causing tail rotor ground strike. Investigation revealed separated torsional coupling rubber mounts led to engine overspeed and shutdown.
Accident Details
The pilot had just completed an aerial application operation at approximately 200 feet above ground level (AGL) when he observed the engine RPM decaying. He proceeded toward an open area to execute a precautionary landing. As the aircraft arrived over the open area at about 100 feet AGL, the engine experienced a total loss of power.
The pilot immediately initiated an autorotation. However, during the flare, the maneuver was performed too high, causing the tail rotor assembly to strike the ground.
Findings
Examination of the wreckage revealed that the engine torsional coupling rubber mounts had separated. This condition led to an overspeed, which ultimately resulted in the engine shutting down.
Probable cause
Separation of the engine torsional coupling rubber mounts, which caused an overspeed that shut down the engine.
What happened in the 11 Oct 1989 Hiller UH-12E accident near Yuma, AZ?
After completing an aerial application operation, a pilot experienced engine RPM decay and performed a precautionary landing. At 100 ft, total power loss occurred; autorotation flare was too high, causing tail rotor ground strike. Investigation revealed separated torsional coupling rubber mounts led to engine…
What aircraft was involved and where did it happen?
The accident on 11 Oct 1989 involved a Hiller UH-12E, registration N689SB, operated by West Farm Air Inc., at Yuma, AZ.
What was the probable cause of the accident?
Separation of the engine torsional coupling rubber mounts, which caused an overspeed that shut down the engine.
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