Hiller 12E accident near Poterville, California, March 16, 1986
On March 16, 1986 at about 6:02 pm local time, a Hiller 12E (helicopter), registered N90475, was substantially damaged in an accident near Poterville, California. It was a positioning flight under general aviation rules (Part 91). 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
The NTSB has not yet published a probable cause for this accident. Investigations usually take one to two years; this page updates when the final report is released.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- March 16, 1986 · about 6:02 pm local time
- Place
- Poterville, California · map
- Type
- Accident
- Injuries
- No one was hurt; 1 person was on board or involved.
- Weather
- visual conditions (good weather)
- Aircraft
- Hiller 12E
- Registration
- N90475 · no longer on the register · serial 2366
- Damage
- Substantial damage
- Flight
- Positioning flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
A HILLER 12E HELICOPTER LANDED HARD AFTER AN ENG FAILURE. THE ACFT WAS ENROUTE TO ANOTHER FIELD SITE AT APRX 100 FT AGL AND 40 KTS IAS. THE ENG QUIT ABRUPTLY AND THE ROTOR RPM DECAYED 100 RPM. THE ACFT WAS ABOUT 2,000 POUNDS GWT AT THE TIME OF THE ACCIDENT AND THE AUTOROTATIONAL RPM WAS RIGGED FOR THE MAXIMUM GWT OF 3,100 POUNDS. THE ENG MAIN CASE WAS CRACKED IN THE VICINITY OF CYL #6. DURING THE ENG TEARDOWN #6 PISTON, CONNECTING ROD AND ONE RODCAP BOLT CAME OFF WITH THE CYL. ONE ROD BOLT WAS BROKEN AND THE NUT WAS STILL ATTACHED TO THE BROKEN END. THE OTHER ROD BOLT WAS UNBROKEN AND THE NUT WAS MISSING.
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: airline transport pilot, commercial pilot
- Ratings: multi-engine land; single-engine land; instrument: airplane; instrument: helicopter; rotorcraft: helicopter
- Flight time: 6,700 hours in all; 600 in this make and model; 100 in the last 90 days; 60 in the last 30 days; 6,500 as pilot in command
- Medical certificate: Class 2 (valid medical--w/ waivers/lim.)
- Seat: ctr
The aircraft
- Last inspection: annual inspection
- Maximum gross weight: 3,100 lb
- Seats: 3
- Landing gear: fixed
- Engine: Lycoming VO-540-B1A (piston); 0 hours total
The flight
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 225° at 5 knots
- Visibility: 30 statute miles
- Sky: clear
- Temperature: 61°F (16°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.