Hiller UH-12E accident near Huron, California, March 21, 1992
On March 21, 1992 at about 7:00 pm local time, a Hiller UH-12E (helicopter), registered N93478, was destroyed in an accident near Huron, California. It was an aerial application (crop spraying) flight under agricultural flying rules (Part 137). No one was hurt; 1 person was on board or involved. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A SEPARATION OF THE CONTROL ROTOR CUFF DUE TO FATIGUE.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- March 21, 1992 · about 7:00 pm local time
- Place
- Huron, California · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Hiller UH-12E · all UH-12Es on the register
- Registration
- N93478 · no longer on the register · serial 1608
- Damage
- Destroyed
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
THE PILOT EXPERIENCED A SUDDEN VIOLENT MAIN ROTOR VIBRATION WHILE ON A SPRAY RUN OVER AN ORCHARD. WHILE MANEUVERING AT ABOUT 12 FEET ABOVE THE TREE TOPS, ONE OF THE CONTROL ROTOR BLADE ASSEMBLIES SEPARATED FROM THE ROTOR HUB. AN EXAMINATION OF THE SEPARATED CONTROL ROTOR ASSEMBLY REVEALED A FATIGUE CRACK THAT ORIGINATED AT THE ROTOR CUFF RETAINING BOLT HOLE. THE CONTROL ROTOR CUFF IS THE SUBJECT OF A 100-HOUR RECURRING INSPECTION AS A RESULT OF AN AIRWORTHINESS DIRECTIVE (AD). THE AD WAS COMPLIED WITH DURING THE LAST 100-HOUR INSPECTION. THE CUFF HAD ACCUMULATED 88.8 HOURS OF SERVICE SINCE THE LAST 100-HOUR INSPECTION.
The complete narrative as the NTSB published it. The NTSB's docket holds the report as a PDF and any photographs, statements and other documents from the investigation.
The factual record from the NTSB's investigation tables, in plain English
Pilot
- Certificate: commercial pilot
- Ratings: single-engine land; rotorcraft: helicopter
- Flight time: 5,500 hours in all; 4,000 in this make and model; 40 in the last 90 days; 40 in the last 30 days; 5,200 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: ctr
The aircraft
- Airframe total time: 5,440 hours
- Last inspection: 100-hour inspection, September 22, 1991; 89 hours since
- Maximum gross weight: 2,850 lb
- Seats: 3
- Landing gear: fixed
- Engine: Lycoming VO-540-C2A (piston); 0 hours total
- Operator: Huron AG Helicopters INC.
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 180° at 3 knots
- Visibility: 15 statute miles
- Sky: clear
- Temperature: 64°F (18°C), dew point 0°F (-18°C)
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 |
Documents from the investigation the NTSB's docket: the evidence folder behind the report
The docket, the folder of records gathered during an investigation (maintenance records, photographs, witness statements, examinations), has not been read from the NTSB for this case yet; the list appears here once it has. Open the docket at the NTSB.
Everything on this page comes from the NTSB's public records. The narrative, probable cause and findings are the NTSB's own words; the coded tables behind the report are written out in plain English, with pilots' ages, home towns and medical details left out. The documents and photographs are the NTSB's docket, shown as the NTSB released them. This site's own text never names anyone involved. A preliminary report can change; the final report usually follows one to two years later, and the page is refreshed when it does.