On July 20, 1996, a Hiller UH-12E (registration N124HA) was involved in an aviation accident near Healdsburg, CA. Investigators recorded the probable cause as: The failure of the pilot to confirm a loss of power before entering autorotation after reading an erroneous instrument indication on the helicopter's dual tachometer. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A helicopter struck trees after entering autorotation over steep terrain upon observing split rotor/engine tachometer needles. A previous rotor-tach generator failure was tied to a loose electrical connection.
Accident Sequence
The pilot initiated an autorotation after observing split needles on the rotor/engine tachometer. The maneuver was conducted over unsuitable steep terrain, and the helicopter subsequently struck trees.
Previous Maintenance Issue
The helicopter had experienced a prior failure of the rotor-tach generator. That failure was attributed to a loose electrical connection and was reportedly repaired by the previous owner.
Component Condition
Examination of the electrical connection revealed that it produced intermittent and inaccurate instrument readings when the wire bundle was moved or flexed. The potting material within the electrical connector was found to be in poor condition.
Frequently asked questions
What happened in the 20 Jul 1996 Hiller UH-12E accident near Healdsburg, CA?
A helicopter struck trees after entering autorotation over steep terrain upon observing split rotor/engine tachometer needles. A previous rotor-tach generator failure was tied to a loose electrical connection.
What aircraft was involved and where did it happen?
The accident on 20 Jul 1996 involved a Hiller UH-12E, registration N124HA, at Healdsburg, CA.
What was the probable cause of the accident?
The failure of the pilot to confirm a loss of power before entering autorotation after reading an erroneous instrument indication on the helicopter's dual tachometer. Factors in the accident were the erratic instrument, and maintenance personnel who failed to properly repair the system after the discrepancy was…
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