History of Flight
On October 20, 2014, about 1045 Pacific daylight time, an experimental amateur-built Sonex Tri-gear, N91922, collided with terrain near Fawnskin, California. The pilot/owner was operating the airplane under 14 Code of Federal Regulations Part 91. The private pilot sustained fatal injuries, and the airplane sustained substantial damage. The cross-country personal flight departed Big Bear City Airport, Big Bear, California, about 1035 with a planned destination of Mesa, Arizona. Visual meteorological conditions prevailed, and no flight plan was filed.
The pilot departed from runway 26; the airport was located about 1 mile east of Big Bear Lake. Witnesses observed the airplane about 200 feet above ground level over Big Bear Lake, but noted that this was below the level 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 until ground impact.
Personnel Information
A review of Federal Aviation Administration (FAA) airman records revealed that the 60-year-old pilot held a private pilot certificate with a rating for airplane single-engine land. He held a third-class medical certificate issued on March 8, 2005, with the limitation that he must have glasses available for near vision. The accident airplane was a light sport model, which does not require a medical certificate to operate. The pilot also held a light sport repairman certificate.
No personal flight records were located for the pilot. The National Transportation Safety Board investigator-in-charge (IIC) obtained aeronautical experience from FAA medical records. On his most recent medical application, the pilot reported a total time of 500 hours with 6 hours logged in the previous 6 months.
Aircraft Information
The pilot purchased the airplane 2 days prior to the accident.
The airplane was a low wing, experimental amateur-built Sonex Tri-gear, serial number 811; the cowling was fiberglass; the remainder was metal. A review of logbooks revealed it was manufactured in 2007. Total airframe time was 98.6 hours at the most recent conditional inspection on July 27, 2014. A logbook entry dated October 8, 2007, noted speeds during Phase 1 testing: Vso 40 mph, Vx 80 mph, and Vy 94 mph at a gross weight of 1,100 pounds and center-of-gravity at 68 inches aft of datum.
The engine was a Volkswagon 2180 Aerovee, serial number 270, rated at 80 horsepower. The last maintenance recorded was an oil change on October 18, 2014, at a total time of 11.2 hours.
Examination of maintenance and flight department records revealed no unresolved maintenance discrepancies prior to departure.
Fueling records at Big Bear Airport established that the airplane was last fueled prior to the accident with the addition of 9.1 gallons of 100-octane low lead aviation fuel.
Meteorological Information
An automated surface weather observation at Big Bear (KL35) (elevation 6,752 feet msl, 6 miles northeast of the accident site) was issued 10 minutes prior to the accident. It indicated wind from 290 degrees at 4 knots, visibility 10 miles or greater, temperature 16°C, dew point 2°C, and an altimeter setting of 30.18 inches of mercury.
Wreckage and Impact Information
The IIC and FAA inspectors examined the wreckage on site the day of the accident. The airplane came to rest in a dry lakebed on a northeasterly heading. All components remained with the main wreckage, and in position; a few pieces of plexiglass surrounded the main wreckage. There were no ground scars leading to the wreckage. The principal impact crater was under the propeller and fuselage.
The nose of the airplane and the wing's leading edges exhibited up and aft crush damage. The engine partially separated but maintained its position on the airframe. One of the wooden propeller's blades splintered near the hub, with pieces buried in the ground; the other blade splintered about halfway to the tip. All flight controls remained in place and connected.
The wreckage was recovered to a secure location for further examination.
Medical and Pathological Information
A postmortem examination conducted by the San Bernardino County Medical Examiner listed the cause of death as blunt force injuries.
The NTSB medical officer reviewed the pilot's certified medical records, toxicology report, autopsy report, accident report, and interviewed the FAA medical case review physician.
According to the FAA medical case review, the pilot reported on his 2005 medical application that he had sleep apnea treated with continuous positive airway pressure (CPAP) therapy and had carpal tunnel surgery the prior year. He reported no medication use, and the examining physician noted no abnormal findings. Sleep apnea was first diagnosed and treated with CPAP in February 2003, and the pilot provided diagnostic and treatment records demonstrating successful treatment. The records did not identify additional chronic medical issues, and the pilot was issued a third-class medical special issuance certificate not valid for operations requiring a medical certificate after March 31, 2007. The IIC interviewed a family member who stated that the pilot regularly used the CPAP machine and that it greatly enhanced his well-being.
The autopsy did not identify any significant natural disease. The medical examiner's investigation identified a black bag containing a possible sleep apnea machine.
The FAA Forensic Toxicology Research Team performed toxicological testing. Analysis found no carbon monoxide or volatiles; tests for cyanide were not performed. Citalopram was detected in liver and blood (cavity), and N-desmethylcitalopram was detected in liver and blood (cavity). The San Diego County Forensic Toxicology Laboratory identified 0.43 mg/l citalopram in cavity blood. Citalopram is a prescription medication (Celexa) used to treat depression and panic disorder. The therapeutic level is 0.030 to 0.400 mg/l. The FAA will consider a special issuance for depression after 6 months of treatment if the applicant is stable on one of four approved medications (citalopram, escitalopram, fluoxetine, sertraline).
Tests and Research
The IIC examined the wreckage at Air Transport, Phoenix, Arizona, on October 26, 2014. Control continuity for all flight controls was established. No mechanical anomalies were identified on the airframe.
The engine had partially separated but maintained its position. No holes on the top of the crankcase or cylinders. No liquid streaks were observed. The crankshaft was manually rotated via the propeller; it rotated freely, and the valves moved approximately the same amount of lift. Gears in the accessory case turned freely. Thumb compression was obtained on all cylinders.
Spark plugs were removed; gaps were similar, and electrodes had no mechanical deformation. All electrodes were gray and clean except the top and bottom plugs for cylinder number two, which contained heavy, black soot, as did the inside of the combustion chamber. Gray color corresponds to normal operation per Champion Aviation Check-A-Plug AV-27 Chart; heavy, black soot indicates carbon fouling.
A Garmin GPSMAP 296 was recovered, and the NTSB Vehicle Recorder Division extracted data for 71 track logs including the accident flight. Data indicated one aborted takeoff from runway 26 prior to the accident takeoff. During the aborted takeoff, the maximum derived groundspeed was 41 knots. The accident departure was about 3 minutes after the aborted takeoff. The data recorded about 4 minutes of flight; the last data point was at a GPS altitude of 7,011 feet (the highest recorded) and a ground speed of 59 knots (73 was the highest recorded). Due to buffering, data recording may have ended before the accident event.
Additional Information
Using the ambient weather conditions, the computed density altitude was 8,222 feet.
Sonex provided owners with a flight manual containing areas for recording climb performance data in Section 6. No manual was recovered for this airplane, and the data was not available.
The flight manual noted that slight engine roughness could be caused by one or more spark plugs becoming fouled by carbon or lead deposits. A Sonex technical representative reported that the engine should have been developing about 60 horsepower under the encountered conditions. The representative opined that the heavy, black soot indicated a rich fuel mixture, and since it was confined to one cylinder, a reasonable cause would be valve adjustment/operation for that cylinder. The representative noted that the airplane should have been able to stay airborne if properly built, tuned, faired, and piloted; this airplane did not have wheel pants or fairings on any wheel. Sonex conducted flight testing on an airframe without wheel pants and fairings on just the main gear. With wheel pants and gear fairings installed, speed was 140 mph at 2,600 feet and wide open throttle at 3,400 rpm; the speed was 127 mph at 2,600 feet at a cruise power of 3,100 rpm. Lack of wheel pants resulted in a 3 mph loss of cruise speed, and lack of wheel fairings resulted in an additional 10 mph loss. They indicated that no pant or fairing on the nose wheel could result in additional performance loss.