Amateur-built Sonex FR1 accident near Paso Robles, California, March 25, 2009
On March 25, 2009 at about 5:40 pm local time, a amateur-built Sonex FR1, registered N1006N, was substantially damaged in an accident during enroute near Paso Robles, California (Paso Robles Municipal Airport). It was a personal flight under general aviation rules (Part 91). 1 person was seriously injured. The weather was visual conditions (good weather).
The NTSB's probable cause their words, unchanged
A total loss of engine power during cruise flight due to the pilot/builder’s failure to follow the engine manufacturer’s maintenance instructions and apply the correct torque to the rocker arm nuts during maintenance.
Source: NTSB aviation accident database, copy made October 5, 2026. Docket and reports at the NTSB.
What the record shows
- Date
- March 25, 2009 · about 5:40 pm local time
- Place
- Paso Robles, California · Paso Robles Municipal Airport · map
- Type
- Accident
- Injuries
- 1 person was seriously injured.
- Weather
- visual conditions (good weather)
- Aircraft
- Amateur-built Sonex FR1
- Registration
- N1006N · no longer on the register · serial 001
- Damage
- Substantial damage
- Flight
- Personal flight · general aviation rules (Part 91)
The NTSB's narrative final · quoted from the NTSB record
During cruise flight the engine of the experimental amateur-built airplane began to run rough and then lose all power. The pilot/builder then performed a forced landing in a vineyard. During the landing sequence, the airplane struck a trellis and sustained substantial damage to the firewall and right wing. Postaccident examination of the engine revealed that the valve clearance for three of the cylinder head rocker arms was beyond adjustment tolerances; additionally, one of the pushrods was loose within the cylinder head and did not make contact with its associated rocker arm. The pilot performed maintenance about 24 flight hours prior to the accident flight which included adjusting the rocker arm valve clearance. The pilot noted in the engine logbook that the valves were gapped at the manufacturer’s recommended setting. The pilot was not aware of the engine manufacturer's requirement to apply a specific torque to the valve rocker adjustment nuts during adjustment, and as such, did not tighten the nuts to the recommended torque level.
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
What happened, in order
- Aircraft maintenance event during prior to flight
- Loss of engine power (total) during enroute defining event
- Off-field or emergency landing during emergency descent
- Collision with terrain or object (not controlled flight into terrain) during landing
The NTSB's findings
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip eng cyl section › Incorrect service/maintenance
- cause Aircraft › Aircraft power plant › Engine (reciprocating) › Recip eng cyl section › Failure
- cause Personnel issues › Task performance › Maintenance › Scheduled/routine maintenance › Pilot
- cause Personnel issues › Task performance › Use of equip/info › Use of manual › Pilot
Pilot
- Certificate: sport pilot
- Ratings: single-engine land
- Flight time: 116 hours in all; 3 in this make and model; 5 in the last 90 days; 3 in the last 30 days; 3 as pilot in command
- Last flight review: October 20, 2008
- Medical certificate: None
- Seat: left
- Injury: serious injuries
The aircraft
- Airframe total time: 50 hours
- Last inspection: condition inspection, February 14, 2008; 23 hours since
- Maximum gross weight: 1,100 lb
- Seats: 2
- Landing gear: fixed
- Engine: Aerovee (piston); 0 hours total
The flight
- Departed from: PRB Paso Robles CA at 5:10 pm
- Destination: PRB Paso Robles CA
- Flight plan: not recorded
Weather at the time
- Light: daylight
- Visibility: 10 statute miles
- Sky: clear
- Temperature: 55°F (13°C), dew point 43°F (6°C)
- Altimeter: 30.00 inHg
- Observation at 5:53 pm from PRB, 3 miles away
Injuries
| Fatal | Serious | Minor | None | |
|---|---|---|---|---|
| Flight 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.