Amateur-built TR-4 accident near Davis, California, December 24, 1996
On December 24, 1996 at about 9:05 pm local time, a amateur-built TR-4, registered N91RT, was substantially damaged in an accident near Davis, California. It was a personal flight under general aviation rules (Part 91). 2 people had minor injuries. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The fatigue fracture and separation of one rod end cap bolt. A factor in the accident was the nature of the terrain for the forced landing.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- December 24, 1996 · about 9:05 pm local time
- Place
- Davis, California · map
- Type
- Accident
- Injuries
- 2 people had minor injuries.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built TR-4
- Registration
- N91RT · no longer on the register · serial 401
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The aircraft was in cruise at 3,500 feet when a slight engine vibration became apparent to the pilot. The engine oil pressure and temperature were normal; however, as a precaution he turned toward a nearby airport. One minute later, a severe vibration began shaking the aircraft. The pilot could not make the airport and landed in a marshy field. The engine ran the entire time from vibration onset until just before ground contact. The engine was factory new 2.5 years and 358 hours prior to the accident. During recovery of the aircraft, no oil film was observed on the aircraft or in the engine compartment. Significant quantities of clean oil were found in the oil filter canister, and the undamaged oil pump. No metal contamination or scoring was observed to the oil pump housing or impeller rotors. Complete engine disassembly revealed that the number 3 connecting rod was separated from the crankshaft journal, with severe peening noted to both the rod end and crankshaft journal. No significant heat distress or scoring signatures were noted on any bearing or journal. The battered number 3 rod end cap and the two associated bolts were found in the oil sump. One bolt was found fractured just below the head. The second bolt was bent about 20 degrees, with severe battering noted to the bolt threads and a portion of the nut. The direction of bend in the distorted bolt was observed to be 180 degrees from the center of the rod cap. Metallurgical examination of the fractured bolt revealed a fatigue crack with multiple plane origins in the radius between the head shoulder and the decreased diameter portion of the bolt. Hardness tests disclosed values in the acceptable range according to Lycoming specifications.
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, military
- Ratings: multi-engine land; single-engine land; instrument: airplane
- Flight time: 2,000 hours in all; 20 in this make and model; 50 in the last 90 days; 10 in the last 30 days; 1,800 as pilot in command; 300 on instruments
- Medical certificate: Class 3 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 358 hours
- Last inspection: annual inspection, July 1, 1996; 80 hours since
- Maximum gross weight: 2,300 lb
- Seats: 4
- Landing gear: fixed
- Engine: Lycoming O-360-A4M (piston); 0 hours total
The flight
- Departed from: Q96 Sacramento CA at 8:30 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: from 330° at 5 knots
- Visibility: 70 statute miles
- Sky: broken clouds at 20,000 ft; not recorded
- Temperature: 54°F (12°C), dew point 0°F (-18°C)
- Altimeter: 30.00 inHg
- Observation at 7:47 pm from SMF, 13 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.