# Accident 19981024040399A: Hiller UH12C, Clinton, IA, October 24, 1998

- Type: FAA accident report (Accident/Incident Data System), as reported
- Date: October 24, 1998, 11:30 local time
- Place: Clinton, IA
- Damage: Substantial damage
- Phase of flight: Autorot Descent (Rotorcraft)
- Operating rules: General operating rules (Part 91)
- Location: 41.8395° N, 90.2293° W: From the FAA, an estimate near the named town, within about 3 miles
- Nearby events: https://openairdocs.org/map.md?lat=41.8395&lon=-90.2293&mi=10
- Aircraft: N9739C, registered now (https://openairdocs.org/aircraft/N9739C) (OpenAirDocs)
- Registry model: Hiller UH-12C (registry code 4360116, https://openairdocs.org/model/hiller-uh-12c) (OpenAirDocs)
- Registry engine: Franklin 6V4 series (registry code 27033, https://openairdocs.org/engine/franklin-6v4-series) (OpenAirDocs)
- Reported make and model: HILLER UH12C
- People aboard: 2
- Fatal injuries: 0
- Pilot flight hours: 475 total, 173 in this make and model, 8 in the last 90 days
- NTSB investigation: [NTSB CHI99LA012](https://openairdocs.org/ntsb/CHI99LA012) (OpenAirDocs)
- FAA source: FAA Aviation Safety Information Portal (https://asip.faa.gov/)
- Page: https://openairdocs.org/incident/19981024040399A

## Narrative

As the FAA filed it, in capitals; the FAA replaces private details with ^PRIVACY DATA OMITTED^.

(-23) WHILE IN CRUISE FLIGHT, THE PILOT WAS UNABLE TO MAINTAIN ALTITUDE AND HEADING. AN EMERGENCY LANDING WAS INITIATED WHICH RESULTED IN LOSS OF CONTROL APPROXIMATELY TEN FEET ABOVE THE LANDING AREA. (.4) DURING CRUISE FLIGHT THE HELICOPTER SUFFERED A LOSS OF TAIL ROTOR AUTHORITY.  THE PILOT INITIATED AN AUTOROTATIONAL LANDING; HOWEVER, DURING THE APPROACH HE LOST ALL CONTROL OF THE AIRCRAFT.  AN INSPECTION OF THE TAIL ROTOR GEARBOX AFTER THE ACCIDENT REVEALED A FAILURE OF THE 90 DEGREE GEARBOX.  THE LOG BOOKS INDICATED AN OVERHAUL 195 HOURS PRIOR TO THE ACCIDENT WITH NO OTHER MAINTENANCE ON THE GEARBOX NOTED.  AN INSPECTION OF THE HELICOPTER WAS CONDUCTED ONE MONTH PRIOR TO THE ACCIDENT AND THE HELICOPTER HAD ACCUMULATED ABOUT 33 HOURS SINCE THAT INSPECTION.

## The NTSB's investigation of this event (1)

From the NTSB's public API. Aircraft are matched to registry aircraft by N-number and event date, checked against the reported serial number, make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model.

- [NTSB CHI99LA012](https://openairdocs.org/ntsb/CHI99LA012), Oct 24, 1998: Hiller UH-12C (N9739C), Clinton, IA, substantial damage. Probable cause: the failure of the 90 degree gearbox for reasons undetermined. Factors were the failure of the gearbox, and it not being possible for the pilot to maintain control of the aircraft.

## Other reports on N9739C (1)

Matched to the same aircraft by N-number and date.

- [Incident 19781020029159I](https://openairdocs.org/incident/19781020029159I), Oct 20, 1978: Hiller UH12C (N9739C), Carbondale, IL, Minor damage. Student delayed in leveling after a practice autorotation. Tail rotor struck the ground.

From the FAA Accident/Incident Data System. Reports are matched to registry aircraft by N-number and event date, checked against the reported make and model; the registry's history has gaps, so older matches can be wrong. Compare the reported make and model. For accidents, the NTSB's own investigation is the fuller record.

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