Accident Overview
On June 28, 2013, about 1930 Pacific daylight time, a Quicksilver MXL-II light sport airplane, registration N2812, was substantially damaged during a forced landing following a partial loss of engine power near Newbury Park, California. The light sport pilot and his sole passenger sustained serious injuries. Visual meteorological conditions prevailed for the local flight, which was conducted under 14 CFR Part 91 without a flight plan. The flight departed Camarillo Airport (CMA), Camarillo, California, about 1900.
Pilot Report
In a post-accident interview with the National Transportation Safety Board investigator-in-charge, the pilot reported that the purpose of the flight was to check the operation of the engine, as it had been missing and running rough on a previous flight. During the flight, the engine began to run rough, and when the pilot could not obtain an increase in power with the throttle and extra electric fuel pump, he elected to make an emergency landing. After landing on uphill sloping terrain, the airplane nosed over and came to rest inverted.
Engine Examination
On July 18, 2013, under the supervision of an FAA aviation safety inspector, a Rotax field technician performed a detailed examination of the engine—a Rotax 503, twin-cylinder, two-stroke, fan-cooled engine with dual carburetors, dual ignition, and a reduction gearbox. The examination revealed the engine remained attached to the airframe. The exhaust muffler and Warp Drive propeller had been previously removed and placed nearby. The exhaust system was the correct type but in very poor condition with previous weld repairs and several cracks. The technician noted that while Rotax does not prohibit welding or repairing exhaust mufflers, they do not provide instructions for such repairs. The technician stated that an exhaust system with an existing leak and multiple prior crack repairs should be replaced. The technician referred to the Rotax Operators Manual, which warns to repair all discrepancies before flight and to inspect exhaust for cracks, security, and spring condition.
Exhaust System Findings
The technician reported that during handling, the exhaust sounded like it contained broken baffles. Any broken internal baffles could affect engine reliability by potentially blocking the exhaust system, leading to immediate engine failure or power loss. After cutting the exhaust open, internal baffles were observed to be in very poor condition, with several broken components. The technician concluded that broken baffles could shift during different flight attitudes and block exhaust flow, causing a loss of power. The internal and external examination showed the system was unsuitable for flight.
Logbook Review
Engine logbook entries showed the engine was installed on February 12, 2013, at a Hobbs reading of 2,268.3 hours. On June 23, 2013—five days before the accident and at a Hobbs time of 2,323.7 hours—the spark plugs and exhaust gaskets were changed.
Follow-up Pilot Interview
The pilot reported in a follow-up interview that the exhaust system had been inspected for cracks about 20 hours before the accident flight, with none observed. The system was completely removed and reinstalled after that inspection. The pilot stated that the welds noted in the investigation were not done after his club purchased the system, and he had no knowledge of when, where, or by whom they were performed. He added that when an anomaly is detected, the exhaust system is removed and replaced.
Engine Test Runs
The engine was test-run twice. For the first run, a secondary fuel container was used because the aircraft's fuel tank was breached. The battery was connected in its original location. The original exhaust muffler was not installed. The engine started and ran without issues; RPM was manipulated via throttle cables, and then the engine was shut off. No anomalies were noted.
For the second test run, the original exhaust muffler was installed. The engine started and ran for several seconds before being manually shut down, again with no anomalies noted.