WPR15FA016 · Sonex SONEX TRIGEAR
Sonex SONEX TRIGEAR · Accident: loss of control in flight while maneuvering
From Big Bear City Airport (L35) to Falcon Field (FFZ)
Event
- NTSB case
- WPR15FA016
- Event typeAccident: someone killed or seriously injured, or the aircraft substantially damaged (NTSB definition). Incident: an occurrence that affected or could have affected safety, short of that. Glossary
- Accident
- InvestigationHow far the investigation had got when the record was published: preliminary, ongoing, final or completed. Unknown where the source does not say. Glossary
- Completed
- API-reported fatalities
- 1 · all aircraft and ground
- Ground fatalities
- Unknown
- OperationWhat kind of flying it was, grouped by the rules it flew under: airline (US Part 121), air taxi and commuter (Part 135), general aviation (Part 91 and similar), military or government. Glossary
- General aviation
- WeatherVisual meteorological conditions (VMC): good enough to fly by looking outside. Instrument conditions (IMC): cloud or low visibility, flying by instruments. Glossary
- Visual Meteorological Cond
Sonex SONEX TRIGEAR
- Aircraft type
- Sonex TRIGEAR
- Category
- Airplane
- RegistrationThe aircraft's tail number, such as N12345 or G-ABCD. Registrations are reissued, so the same one years apart can be a different aircraft. Glossary
- N91922
- Operator
- Unknown
- Onboard fatalities
- Unknown
- Route
- From Big Bear City Airport (L35), Big Bear, CATo Falcon Field (FFZ), Mesa, AZ
- Aircraft age
- About 7 years (built 2007)
- Flight rulesThe regulations the flight operated under: in the US, Part 91 (general aviation), Part 121 (airlines), Part 135 (air taxi and commuter) and others; for flights abroad, the NTSB's coarser commercial or non-commercial code. Glossary
- Part 91: General Aviation
- Phase of flightThe stage of the flight when things started to go wrong: standing, taxi, takeoff, initial climb, en route, maneuvering, approach or landing. Glossary
- Maneuvering · low-altitude flying
- Defining eventThe single coded event the NTSB judges best describes what happened (records from 2008 on). Older records name the first occurrence in the sequence instead. Glossary
- Loss of control in flight
- DamageDestroyed: beyond practical repair. Substantial: damage that affects the structure, performance or handling and normally needs major repair. Minor: less than that. Glossary
- Substantial
Cause areas
- Aircraft › Aircraft oper/perf/capability
- Personnel issues › Action/decision
- Personnel issues › Task performance
Approximate · Coordinates as recorded by the NTSB; no uncertainty radius is established.
NTSB narrative
The sport pilot had purchased the airplane 2 days before the accident and was returning it to his home airport. Witnesses observed the airplane shortly after takeoff over a lake near the departure airport, and noted that the airplane was below the elevation of the surrounding terrain. As the airplane approached a cove, it banked left to almost 90 degrees. The nose dropped to a nearly-vertical attitude, and the airplane descended to ground contact.
A postaccident examination of the airframe and flight controls revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. Examination of the engine determined that one of the four cylinders was carbon-fouled, which was likely the result of an overly rich fuel/air mixture due to the valve adjustment in that cylinder. Given the condition of the cylinder, the 80-horsepower (hp) engine was most likely producing only about 60 hp before the accident. The airplane was not equipped with wheel pants or fairings, which increased drag and further degraded the airplane's performance. Additionally, the density altitude at the time of the accident was over 8,200 ft.
Although the pilot had a history of sleep apnea, he was using continuous positive airway pressure (CPAP) therapy, and it is unlikely that his sleep apnea contributed to the accident. Toxicological testing detected citalopram, a prescription medication used to treat depression and panic disorder. The investigation did not determine a definitive psychiatric diagnosis, but no operational evidence of pilot impairment was identified, and it is unlikely that the pilot's use of this medication contributed to the accident.
The combination of high density altitude, airplane configuration, and cylinder fouling resulted in significantly decreased performance. It is likely that the airplane's margin above stall speed was minimal as the pilot attempted to climb the airplane after takeoff, and in his attempt to maneuver away from the rising, mountainous terrain, the pilot exceeded the airplane's critical angle of attack, which resulted in an aerodynamic stall/spin.
Probable cause
The pilot's failure to maintain airspeed after takeoff, which resulted in an exceedance of the airplane's critical angle of attack and a subsequent aerodynamic stall/spin at low altitude. Contributing to the accident was the airplane's reduced climb performance due to a carbon-fouled engine cylinder, the airplane's lack of wheel pants and fairings, and the high density altitude conditions.
Verbatim NTSB analysis and probable cause from the NTSB dataset
Sources
NTSB record WPR15FA016
- Event ID
- 20141020X44147
- Case number
- WPR15FA016
- Dataset
- full-current
- Source SHA-256
- 5cf380f0061817c0331a6b2d8cc7e0ee3a79bea469a1001dc5c10e56f35f5ab3
Source notes (4)
- Unreviewed is an editorial label, not an investigation status. API-sourced is not report-checked or human-reviewed. Explicit event totals are used without summing aircraft injury tables; onboard allocation is withheld. Unknown values remain unknown. The operation category is mapped from the NTSB-reported FAR part and has not been reviewed.
- Filled from the NTSB case API where the bulk record had no value: investigation status. Values present in the bulk record are kept.
- The date is the local date, which is the same as the UTC date the NTSB stores.
- API snapshot SHA-256: 882a297281477654383d7e13d4b1a8b0069abe0415cb9fd176166ce8547f61e4; retrieved 2026-09-14T17:27:40.273Z.