On July 15, 1984, a Hiller UH-12E (registration N4030A) operated by San Francisco & Fesno Land CO was involved in an aviation accident near Orcutt, CA. Investigators recorded the probable cause as: The terminal pin was installed beneath the terminal tee instead of through it, contrary to manual instructions. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
During a post-maintenance test flight, a helicopter lost collective control and rolled over after a roll-on landing. Examination found a terminal pin installed incorrectly, bypassing the terminal tee.
Accident Details
A maintenance test flight was initiated to check the tracking of the main rotor blades. While the pilot was hover taxiing, collective control was lost and rotor RPM decreased. The pilot was able to execute a roll-on landing, but the helicopter subsequently rolled over and sustained damage.
Examination Findings
An examination of the lower collective center control housing revealed that the terminal pin had been placed through the outer housing but was installed beneath the terminal tee rather than through the tee. The maintenance manual emphasizes that the pin must pass through the terminal tee, but it contained no provisions to verify that the pin had been installed through the terminal tee.
Conclusion
The improper installation of the terminal pin resulted in the loss of collective control during the test flight.
Probable cause
The terminal pin was installed beneath the terminal tee instead of through it, contrary to manual instructions.
What happened in the 15 Jul 1984 Hiller UH-12E accident near Orcutt, CA?
During a post-maintenance test flight, a helicopter lost collective control and rolled over after a roll-on landing. Examination found a terminal pin installed incorrectly, bypassing the terminal tee.
What aircraft was involved and where did it happen?
The accident on 15 Jul 1984 involved a Hiller UH-12E, registration N4030A, operated by San Francisco & Fesno Land CO, at Orcutt, CA.
What was the probable cause of the accident?
The terminal pin was installed beneath the terminal tee instead of through it, contrary to manual instructions.
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