Williams, CA, USA
N123ST
ST CLAIR LANCAIR 360
Having leveled off at cruise altitude, the passenger began to smell an electrical burning odor in the experimental airplane's cabin. Smoke then began to stream from the lower center console to the right of the pilot’s footwell. The passenger attempted to locate the source of the smoke while the pilot initiated an emergency descent. Shortly before landing, the footwell became engulfed in flames. During the landing flare, the airplane struck a group of trees and collided with a berm. The majority of the airplane was consumed by fire; however, examination of the electrical wiring revealed arcing damage to one of the primary electrical supply lines in the area where the passenger reported the first traces of smoke. The wire connected the master solenoid to the airplane’s main system bus. It is most likely that the wire’s insulation had become compromised, leading to its electrical conductor coming into contact with a metallic airframe component, resulting in a short circuit and fire. The pilot shut off the master solenoid during the descent, which would have halted the short circuit; but by then the fire had most likely already spread, possibly igniting the fuel supply components in that area. The fact that the master solenoid was off also negated the possibility that the short circuit occurred during the ground impact sequence. The airplane’s construction consisted of automotive electrical wire and household PVC tubing for electrical conduit. Additionally, the battery and associated master solenoid wiring had been relocated three times since the airplane’s completion; however, it could not be determined if this construction or modification caused or contributed to the short circuit.
HISTORY OF FLIGHT On February 12, 2013, about 1130 Pacific standard time, an experimental amateur-built Lancair 360, N123ST, landed hard during an emergency landing following an in-flight fire near Williams, California. The pilot/registered owner was operating the airplane under the provisions of 14 Code of Federal Regulations Part 91. The private pilot and his pilot rated passenger sustained serious injuries. The airplane sustained substantial damage during the accident sequence, and was subsequently destroyed by fire. The cross-country flight departed Ukiah Municipal Airport, Ukiah, California, about 1100 with a planned destination of Minden-Tahoe Airport, Minden, Nevada. Visual meteorological conditions prevailed, and no flight plan had been filed. The passenger reported that after the airplane leveled off at 9,500 feet mean sea level (msl), he began to smell a “burning electrical” odor. Smoke then began to stream from the lower center console to the right of the pilot’s footwell. The passenger unbuckled his seat belt and attempted to look for the source of the smoke. The pilot initiated an emergency descent, and shutoff the master switch. The intensity of the smoke dwindled temporarily, and then increased. As the airplane approached about 1,000 feet above ground level (agl), intense flames began to erupt from the footwell. The pilot attempted to land the airplane on a raised dirt road, however, during the flare, the left wing struck a group of trees, and the airplane collided with a berm. The passenger reported that the engine continued to operate during the descent. AIRCRAFT INFORMATION The single engine, low wing airplane, was comprised primarily of composite material. It was powered by a Lycoming IO-360 fuel injected engine. FAA Records revealed that construction of the airplane was completed in September 1992. A few months later, the airplane was issued a special airworthiness certificate with Phase I operating limitations of 40 flight hours, which were to be completed within 1 year. The certificate subsequently expired, and another was issued in January 1996 with similar Phase I limitations. Phase I flight tests were subsequently completed, and the airplane was issued its final special airworthiness certificate in November 2000, having accumulated a total of 63.5 flight hours. The airplane was purchased by the pilot on August 24, 2012. Review of the airplane’s maintenance logbooks revealed that the most recent annual inspection was completed on August 6, 2012. At that time, the airframe had accrued a total of 126.3 flight hours. The airplane was equipped with a “header” fuel tank, located behind the instrument panel. The fuel selector valve and associated fuel lines were located in the center console, just to the right of the pilot’s footwell. WRECKAGE AND IMPACT INFORMATION The airplane came to rest along the side of a raised road, adjacent to a grove of fruit trees. The debris field consisted of the fragmented left wing, the lower engine cowling, aft cabin, and all the landing gear doors. The sections of wreckage in the debris field did not exhibit thermal damage or oil contamination. The remaining airplane structure came to rest about 60 feet beyond the initial impact point. The entire structure with the exception of the firewall, engine, and right horizontal stabilizer tip, had been consumer by fire, with only charred composite weave fragments remaining. TESTS AND RESEARCH Engine The engine came to rest inverted, and sustained thermal damage to its lower side and associated ancillary components. All fuel and oil lines were either tight at their fittings, or had been consumed by fire. The oil cooler remained attached to the firewall, and was free of cracks. Both the exhaust manifold and its associated pipe sustained crush damage, and were removed. No cracks were noted, and the corresponding lower cowling in the area adjacent to the exhaust pipe did not exhibit any burn signatures. The magnetos and both the engine driven, and auxiliary fuel pumps were partially consumed by fire. The upper surface of the engine exhibited black sooting, but was largely undamaged. The fuel flow divider remained attached to the crankcase, and all fuel injection nozzles and lines were free of damage. No anomalies were noted with the engine which would have precluded normal operation. Cabin The battery was located in the upper footwell of the right seat, and had sustained extensive thermal damage, with only remnants of its inner plates remaining. All the electrical wiring for the alternator, battery, and engine starting systems had been charred, with most of their insulating material burned away. The wires were examined, and the 4-AWG copper conductor, which directly connected the master solenoid output to the main system bus, had sustained breakage to 11 of its 19 strands, 33 inches from the master solenoid terminal. The area of the damage was located in a position roughly adjacent to the center console in the footwell area. Closer examination of the damaged area revealed that the wire separation surfaces exhibited gray glass-like coatings, and globular melting patterns consistent with fusion and electrical arcing damage. The input side of the master solenoid remained attached directly to the battery’s positive terminal. All remaining electrical wires were examined, and exhibited sooting and brittle fractures, consistent with thermal exposure and subsequent movement during the airplane's recovery from the accident site. ADDITIONAL INFORMATION Original Lancair construction documentation called for the battery to be installed on the rear side of the aft cabin bulkhead, just behind the right seat. The documentation further stated that moving the battery location is permissible in order to achieve the correct airplane weight and balance. Examination of maintenance logbooks revealed that the battery was relocated on three occasions between April 1993 and September 1998. The final placement of the battery would have required rerouting and/or replacement of the master bus electrical wire. Examination of the unburned airplane remnants revealed extensive use of automotive electrical wires and PVC tubing to route wiring through the wing structure. No electrical wiring diagram was recovered for the airplane, however, the configuration of the primary electrical system components appeared to match the manufacturer's “Basic Wiring Diagram” schematic. The schematic did not require a fused link between the battery and master solenoid, rather, the solenoid was controlled by a master switch in the cabin.
An in-flight fire due to an electrical short circuit.
Source: NTSB Aviation Accident Database
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