Hiller UH-12E accident near Delano, California, May 4, 1991
On May 4, 1991 at about 2:00 am local time, a Hiller UH-12E (helicopter), registered N4414, was substantially damaged in an accident near Delano, 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
THAT THE PILOT IMPROPERLY PERFORMED THE AUTOROTATION BY MISJUDGING THE FLARE ALTITUDE. CONTRIBUTING TO THIS ACCIDENT WAS THE TOTAL FAILURE OF THE FREEWHEELING SPRAG CLUTCH DUE TO EXCESSIVE WEAR AND THE SOFT DIRT TERRAIN.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- May 4, 1991 · about 2:00 am local time
- Place
- Delano, 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
- N4414 · no longer on the register · serial 2205
- Damage
- Substantial damage
- Flight
- Aerial application (crop spraying) flight · agricultural flying rules (Part 137)
The NTSB's narrative final · quoted from the NTSB record
SHORTLY AFTER LIFING OFF A PRIVATELY OWNED AIRSTRIP THE ENGINE EXPERIENCED AN OVERSPEED CONDITION. THE PILOT EXECUTED AN AUTOROTATION INTO AN OPEN FIELD. DURING THE AUTOROTATION THE PILOT MISJUDGED THE FLARE ALTITUDE, LANDED HARD CAUSING THE MAIN ROTOR BLADES TO SEVERE THE TAILBOOM ASSEMBLY. THE HELICOPTER ROLLED OVER ONTO ITS LEFT SIDE AS THE FORWARD LEFT SKID DUG INTO THE SOFT TERRAIN.
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: 1,000 hours in all; 38 in this make and model; 58 in the last 90 days; 30 in the last 30 days; 960 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: unk
The aircraft
- Airframe total time: 12,556 hours
- Last inspection: annual inspection, April 11, 1991; 18 hours since
- Maximum gross weight: 2,750 lb
- Seats: 3
- Landing gear: fixed
- Engine: Lycoming VO-540-C2A (piston); 0 hours total
- Operator: San Joaquin Helicopters INC.
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Visibility: 15 statute miles
- Sky: clear
- Temperature: 0°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.