Cessna 172N accident near Thermal, California, June 8, 1991
On June 8, 1991 at about 11:55 pm local time, a Cessna 172N, registered N6230D, was substantially damaged in an accident near Thermal, California (Thermal airport). It was a personal flight under general aviation rules (Part 91). 2 people had minor injuries; 2 others were unhurt. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
THE PARTIAL FAILURE OF THE ENGINE/POWERPLANT FROM A WORN INTAKE VALVE AND THE FAILURE OF COMPANY/OPERATOR MANAGEMENT TO PERFORM AN OVERHAUL ON THE ENGINE WITHIN THE TIME FRAME RECOMMENDED BY THE ENGINE MANUFACTURER.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- June 8, 1991 · about 11:55 pm local time
- Place
- Thermal, California · Thermal · map
- Type
- Accident
- Injuries
- 2 people had minor injuries; 2 others were unhurt.
- Weather
- visual conditions (good weather)
- Aircraft
- Cessna 172N · all 172Ns on the register
- Registration
- N6230D · registry record · serial 17272648
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
A CESSNA 172N NOSED OVER IN SOFT SOIL DURING LANDING ROLL AFTER A FORCED LANDING. THE PILOT INDICATED THAT THE ENGINE WAS RUNNING ROUGH AND LOSING POWER. THE PILOT LANDED THE AIRPLANE ON AN AIRPORT, BUT WAS UNABLE TO MANEUVER THE AIRPLANE TO A RUNWAY. THE AIRPLANE DECELERATED TO ABOUT 20 MPH DURING THE GROUND ROLL ON DIRT. THE AIRPLANE NOSED OVER AFTER THE NOSE GEAR STRUCK A 15 TO 18 INCH HIGH DIRT BANK. THE ENGINE WAS EXAMINED BY AN A&P MECHANIC. THE A&P FOUND THE NUMBER THREE CYLINDER INTAKE VALVE WAS 'TULIPED.' ACCORDING TO THE AIRPLANE'S MAINTENANCE RECORDS, THE ENGINE HAD ACCRUED 2,850 HOURS OF OPERATION WITHOUT OVERHAUL. FORTY FOUR HOURS OF OPERATION BEFORE THE ACCIDENT, THE ENGINE'S CYLINDER COMPRESSION CHECKED 'OK' DURING A LEAK TEST. THE ENGINE MANUFACTURER RECOMMENDED TIME BETWEEN OVERHAULS IS 1,500 HOURS. DURING OVERHAUL THE VALVES ARE REMOVED AND VISUALLY CHECKED FOR WEAR.
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: private
- Ratings: single-engine land
- Flight time: 90 hours in all; 8 in this make and model; 9 in the last 90 days; 9 as pilot in command
- Medical certificate: Class 1 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 4,949 hours
- Last inspection: annual inspection, April 9, 1991; 125 hours since
- Maximum gross weight: 2,220 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming O-320 H2AD (piston); 0 hours total
- Operator: Consair Flying Club
The flight
- Departed from: L77 Chiraco Summit CA at 11:30 pm
- Flight plan: none
- Runway 3, 4,993 ft by 100 ft
Weather at the time
- Light: daylight
- Wind: from 190° at 9 knots
- Visibility: 25 statute miles
- Sky: scat at 10,000 ft
- Temperature: 100°F (38°C), dew point 27°F (-3°C)
- Altimeter: 29.00 inHg
- Observation at 11:53 pm from TRM, 1 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 2 | 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.