History of Flight
On August 17, 2012, at approximately 1425 Pacific daylight time, a Cessna T210N, registration N6493N, experienced an in-flight fire shortly after departing from Meadows Field Airport in Bakersfield, California. The airplane was substantially damaged by the fire. The pilot was operating under 14 Code of Federal Regulations Part 91. The certified flight instructor and two passengers were not injured. The flight was a local personal flight destined for Redlands Municipal Airport, Redlands, California. Visual meteorological conditions prevailed, and no flight plan had been filed.
The pilot reported that after departure, he banked the airplane to enter the right crosswind of the traffic pattern for runway 30R. Smoke entered the cockpit, and the engine began producing only partial power. The pilot decided to return to the airport and configured the airplane for landing on runway 30R. Due to the power degradation, he could not reach the runway and landed in a field outside the airport's perimeter.
The pilot further stated that the fire resulted from a clamp failure on the turbocharger, which appeared to be the origin of the fire. The firewall was damaged by fire.
Aircraft Information
The Cessna T210N, serial number 21063067, was manufactured in 1978. It was equipped with a Teledyne Continental Motors TSIO-520R9B engine. According to the maintenance logbooks, the last annual inspection was completed on May 1, 2012, at a tachometer time of 3,931.0 hours.
Tests and Research
The turbocharger clamp pieces were collected and sent to the National Transportation Safety Board Materials Laboratory for examination. The V-band exhaust clamp had a 2-segment retainer (the "V" portion) and was installed on the turbocharger exhaust gas outlet. The band (flat outer strap) was fractured near the end of the wrap for the t-bolt assembly. Two circumferential cracks were observed in the retainer extending from the gap opposite the t-bolt. Each retainer segment contained one circumferential crack. The clamp was generally covered in oxides and sooty deposits.
The fracture occurred at the edge of a spot weld attaching the band to the retainer, and the fracture surface was on slant planes. Slant-plane fracture features were observed from the edges of the spot weld out to the edges of the band and were consistent with ductile overstress fracture. Reduced width of the band associated with necking deformation was observed adjacent to the fracture. The edges of the band were deformed radially inward. Similar necking deformation with edges deformed radially inward was observed at the mirror opposite side of the band.
In the vicinity of the spot weld, fracture occurred partly in a flat transverse plane, but slant-plane fracture was also observed. The flat plane fracture was near the middle of the thickness, and a slant fracture was observed near the outer surface. Slant fracture was also observed at the inner edge of the band across most of the spot weld except for an area near the middle of the weld that appeared granular but was not in the transverse plane.
A piece of the band containing the t-bolt side of the fracture was separated from the rest of the clamp by cutting the band at the wrap for the t-bolt assembly. The flat fracture region had an intergranular appearance mixed with ductile tear ridges. A piece of the band away from the fracture was cut for hardness testing, which did not reveal any anomalies.
No part number or identifying information was found on the V-band clamp. According to the Parts Catalog for Cessna model 210 and T210 airplanes, one of two part number clamps may be used.