Amateur-built VANS RV-6 accident near Vacaville, California, February 26, 1999
On February 26, 1999 at about 9:30 pm local time, a amateur-built VANS RV-6, registered N36VR, was substantially damaged in an accident near Vacaville, California. It was a personal flight under general aviation rules (Part 91). 1 person had minor injuries; 1 other was unhurt. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
The failure of the engine assembler to apply the proper torque on the connecting rods bolts, which led to fatigue cracking and ultimately fracture of the rod bolts.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- February 26, 1999 · about 9:30 pm local time
- Place
- Vacaville, California · map
- Type
- Accident
- Injuries
- 1 person had minor injuries; 1 other was unhurt.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built VANS RV-6
- Registration
- N36VR · no longer on the register · serial 24999
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
The pilot made a forced landing into rough terrain following a bang and sudden loss of engine power. The engine had accumulated about 70 hours since overhaul. The sump contained a connecting rod, a wrist pin, bearings, many pieces of metal debris, and several rod cap bolts and nuts. None of the rod cap bolts in the sump were intact. They were all bent, fractured, and separated approximately at their midpoint. The pieces were covered with oil. The connecting rods for cylinders number two and four were leaning on the camshaft. The camshaft was not discolored. The crankshaft did not show evidence of discoloration or mechanical damage. A report of metallurgical testing of various engine pieces and their fracture surfaces strongly suggested that the nuts were not tightened on the connecting rod bolts according to specifications. A bolt that corresponded to the head of the bolt from cylinder number two exhibited failure characteristics of low cycle-high stress reverse bending fatigue. Reverse bending fatigue is indicative of an under-torqued bolt. The inspection revealed additional evidence that some of the nuts were not tightened to specification. Some bolts had flattened and polished bolt threads, as well as wear marks on the bolt's outer diameters. Some nut threads had only one end flattened. No fractured bolt had a nut on it except the fatigued bolt.
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, military
- Ratings: multi-engine land; single-engine land; instructor: airplane multi-engine; instructor: instrument airplane; instrument: airplane
- Flight time: 3,479 hours in all; 67 in this make and model; 68 in the last 90 days; 26 in the last 30 days; 3,224 as pilot in command; 925 on instruments
- Medical certificate: Class 1 (valid medical--no waivers/lim.)
- Seat: left
The aircraft
- Airframe total time: 67 hours
- Last inspection: annual inspection, September 9, 1998; 67 hours since
- Maximum gross weight: 1,600 lb
- Seats: 2
- Landing gear: fixed
- Engine: Lycoming O-360 (piston); 0 hours total
The flight
- Departed from: O45 at 9:10 pm
- Flight plan: none
- Runway 0
Weather at the time
- Light: daylight
- Wind: at 3 knots
- Visibility: 25 statute miles
- Sky: broken clouds at 20,000 ft; scat at 10,000 ft
- Temperature: 57°F (14°C), dew point 43°F (6°C)
- Altimeter: 30.00 inHg
- Observation at 9:55 pm from SUU, 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.