NTSB Identification: CHI02LA218.
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Accident occurred Saturday, July 27, 2002 in Copemish, MI
Probable Cause Approval Date: 04/28/2004
Aircraft: Cessna TR182, registration: N756CS
Injuries: 2 Serious,1 Minor.
NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.
The airplane was destroyed during an on-ground fire following an emergency descent/landing due to an in-flight fire. The pilot reported that he smelled smoke followed by the cabin filling with heavy black smoke. The pilot stated flames began to enter the cockpit as he maneuvered the airplane for a landing in an agricultural field. The airplane nosed over during the landing. The left exhaust stack assembly contained a fatigue fracture adjacent to the main collector welded joint. The fracture was in both the heat affected zone and parent material. The fracture initiated in multiple locations on the outside surface of the tube and progressed through a fatigue mechanism. Energy dispersive spectroscopy (EDS) confirmed that both the weld and tube material met design specifications. The weld profile contained no apparent flaws. The left exhaust stack assembly had accumulated approximately 100 hours since new. The design of the Cessna supplied left exhaust stack assembly differs from the comparable Knisley PMA assembly. The Cessna assembly has a two-piece main collector. The two halves are stamped-out and joined together with a seam weld. The weight of the turbocharger assembly is supported in part by the left exhaust stack assembly. The Knisley main collector is manufactured by welding several tube sections together. Knisley issued a mandatory service bulletin that called for the removal of their left exhaust stack assembly and its replacement with the current Cessna assembly or FAA approved equivalent. The service bulletin states that the replacement was instituted because the Knisely assembly was not designed to carry the load of the turbocharger and compressor.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The in-flight engine and cabin fire caused by a fatigue fracture of the left exhaust stack assembly. An additional cause was the part's inadequate design by the aftermarket part manufacturer. A factor to the accident was the soft field in which the emergency landing was made.
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