Accident Overview
On January 24, 2012, at 1552 Pacific standard time, an experimental amateur-built Nemesis NXT, French registration F-WNXT, sustained substantial damage during a forced landing in a plowed field near Camarillo Airport, Camarillo, California. The partial loss of engine power prompted the landing. The airplane was registered to Dopic, Paris, France, and operated by the pilot under 14 Code of Federal Regulations Part 91 as a performance evaluation flight. The airline transport pilot sustained minor injuries. Visual meteorological conditions prevailed, and no flight plan had been filed.
Flight History
The pilot departed Camarillo at 1430, intending to measure fuel consumption and performance parameters for a transcontinental speed record attempt. The aircraft had been serviced to capacity with Jet-A fuel two days earlier. The first hour of flight was uneventful with normal engine parameters. At 18,000 feet mean sea level, the pilot detected an airframe vibration, initially attributed to the propeller. Reducing manifold pressure lessened but did not eliminate the vibration. The pilot elected to return to Camarillo but found the airplane could not maintain altitude, with manifold pressure approximately 20 percent lower than cruise. The engine monitoring system indicated a drop in exhaust gas temperature for one cylinder.
Approaching Camarillo at about 6,000 feet, the pilot began a circling descent. On the downwind leg for runway 26, the landing gear lever was lowered, but the three green "down" lights did not illuminate. The pilot attempted emergency extension but still received no down indication. Air traffic control tower personnel visually confirmed that the landing gear was partially extended. The pilot initiated a go-around but could not maintain altitude during a left crosswind turn. Fearing an inability to return to the airport, he performed an off-field landing in an adjacent plowed field.
The airplane touched down approximately 3,400 feet south of the approach end of runway 26. During the landing roll, it struck a berm about 500 feet beyond the initial touchdown point. The impact caused the wings, landing gear, and sections of the horizontal stabilizer to separate. The fuselage came to rest on its left side, preventing the pilot from opening the canopy. He shut down all systems and pulled circuit breakers while awaiting rescue. A witness arrived minutes later and assisted the pilot in exiting the airplane.
Aircraft and Engine Information
The Nemesis NXT was an experimental amateur-built aircraft. It had been transported from France to the United States in August 2011 to participate in the Reno Air Races as part of the Big Frog Pylon Racing Team. After a conditional inspection, it flew in the races and was subsequently flown to California. The Federal Aviation Administration issued a non-US special flight authorization on January 19, 2012, valid for 11 days, restricting operations to a 40-mile radius of Camarillo Airport.
The airplane was equipped with a three-blade MT Propeller and a Societe de Motorisations Aeronautiques (SMA) prototype engine based on the SR305-230-1, four-cylinder, turbocharged diesel series. Modifications included SR305-230E engine pistons, turbocharger, and revised intake and exhaust manifolds, as well as adjusted fuel injection pump timing. The engine, manufactured in 2010, had accrued 30 flight hours since installation on the airframe in August 2011. The airframe had a total of 75 flight hours at the time of the accident.
Emergency Landing Gear Issue
The emergency landing gear extension system required deactivating both a 5-amp and a 20-amp electrical circuit breaker located in the center console of the instrument panel. The pilot stated that during the attempted activation, he recalled pulling both circuit breakers. However, after the accident, he found that the 20-amp breaker was not in the open position. He surmised that the thickness of his gloves prevented him from positively tripping this breaker during flight.
Examination Findings
Performance data from the MGL Avionics Voyager EFIS was analyzed. The wiring for cylinder head temperature sensors had been transposed between cylinders one and four, so the displayed temperature for cylinder one actually represented cylinder four. The data showed that for the first 35 minutes, all cylinder heads remained between 175 and 200 degrees Celsius. The temperature for cylinder four then dropped about 10 degrees, remaining there for 19 minutes, before a more pronounced divergence to 60 degrees for the final 12 minutes of flight.
The airframe examination revealed no anomalies that would have precluded normal operation. The landing gear and underside sustained extensive fragmentation, preventing determination of the initial gear failure mode.
The engine was examined at SMA Engines facilities in Grand Prairie, Texas. The high-pressure fuel injection line for cylinder four was found loose at the fuel injection pump fitting; the swaged nipple had separated from the line. Multiple areas of contact between the fuel lines and carbon fiber baffling, electrical wires, pneumatic sensor lines, and control cables were noted. Specifically, the air shutoff control cable rested on top of the number four line about 8 inches forward of the pump. Chafing was observed on the upper surface of line four adjacent to that cable. The failed surface exhibited fatigue features with curving crack arrest lines. The maintenance manual cautioned that high-pressure fuel lines must not be distorted, strained, or allowed to rub against other engine parts.
No other anomalies precluding normal operation were identified.