Cessna T210N accident near Mariposa, California, January 24, 2006
On January 24, 2006 at about 5:51 pm local time, a Cessna T210N, registered N4791C, was substantially damaged in an accident near Mariposa, California (Mariposa-Yosemite airport). It was a business flight under general aviation rules (Part 91). 1 person had minor injuries; 1 other was unhurt. The weather was instrument conditions (cloud, fog or low visibility).
The NTSB's probable cause their words, unchanged
The failure of the maintenance personnel to follow the procedures in the TCM maintenance manual and adequately torque the engine through-bolts, which led to the separation of the No. 6 cylinder and the catastrophic failure of the engine.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- January 24, 2006 · about 5:51 pm local time
- Place
- Mariposa, California · Mariposa-Yosemite · map
- Type
- Accident
- Injuries
- 1 person had minor injuries; 1 other was unhurt.
- Weather
- instrument conditions (cloud, fog or low visibility)
- Aircraft
- Cessna T210N · all T210Ns on the register
- Registration
- N4791C · registry record · serial 21063627
- Damage
- Substantial damage
- Flight
- Business flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The aircraft collided with multiple obstacles during a forced landing in rough terrain following a catastrophic engine failure. While en route about 6,000 feet mean sea level, one cylinder in the engine indicated a loss of exhaust gas and cylinder head temperature. Thereafter, an increasingly strong vibration was felt, oil dispersed onto the front windscreen, and all engine power was lost. During the landing flare, the airplane impacted an oak tree, a fence, and a rock outcrop. The engine was found separated from the airplane's firewall. Also, the number 6 cylinder was observed broken from the engine case. The engine was torn down and the case was opened. The evidence of the torque values found on all the engine through-bolts, combined with the fretting signature at the base of the number 6 cylinder, and the oil residue at the union of the case halves, indicates that when the cylinders were installed on the engine their respective bolts were inadequately torqued. During an interview with the mechanic who had replaced the 6 cylinders on the engine, he reported that he followed the instructions in TCM's maintenance manual when he had replaced the cylinders in May 2005. He said he torqued the nuts on the cylinders to about 500 inch pounds. According to TCM's maintenance manual, 1989 edition, the required torque for the through-bolts was 690 to 710 inch pounds. By 1996, TCM had revised its manual by issuance of service bulletin 96-7. In that bulletin the required torque was increased to between 790 to 810 inch pounds.
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; instrument: airplane
- Flight time: 2,136 hours in all; 942 in this make and model; 44 in the last 90 days; 2,136 as pilot in command
- Medical certificate: Class 3 (with waivers/limitations)
- Seat: left
- Injury: minor injuries
The aircraft
- Airframe total time: 4,046 hours
- Last inspection: annual inspection, February 1, 2005; 208 hours since
- Maximum gross weight: 3,800 lb
- Seats: 6
- Landing gear: retractable
- Engine: Continental TSIO-520 (piston); 0 hours total
The flight
- Departed from: VIS Visalia CA at 5:12 pm
- Destination: MPI Mariposa CA
- Flight plan: none
Weather at the time
- Light: daylight
- Visibility: 0.2 statute miles
- Sky: vv at 100 ft
- Temperature: 39°F (4°C), dew point 39°F (4°C)
- Altimeter: 30.12 inHg
- Observation at 5:53 pm from MCE, 20 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Crew | 1 | |||
| Passengers | 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.