CEN19LA055

The accident pilot was in cruise flight in a single-engine airplane when he declared "mayday" on the radio, stating the airplane's engine was on fire. The accident airplane impacted a field, crossed a road, and came to rest upright. A postcrash fire consumed the majority of the airframe. The airplane was equipped with a turbo-charged reciprocating engine and propeller that had been converted under a Supplemental Type Certificate (STC). The engine had accumulated 412.2 hours between the last overhaul and the last annual inspection. The last inspection was about three months before the accident. An examination of the engine revealed fire damage and limited rotation. Disassembly of the engine revealed a broken camshaft and crankshaft. Metallurgical examination of the crankshaft revealed crack arrest marks in the crankshaft, consistent with fatigue, which initiated in the fillet radius at the forward end of the number 6 connecting rod journal. Multiple crack origins and prominent crack arrest lines were consistent with a relatively high stress associated with crack initiation. However, a reason for the high stress or fatigue initiation could not be determined based on the limited airplane records and the damage to the airplane.

On January 17, 2019, about 1650 central standard time, a Beech A-36 airplane, N2021T, was destroyed when it impacted terrain in Fredericksburg, Texas. The pilot was fatally injured. The airplane was operated as a Title 14 Code of Federal Regulations Part 91 personal flight. The airplane was flying from Bulverde Airpark, San Antonio, Texas, to Gillespie County Airport (T82), Fredericksburg, Texas, when another pilot reportedly heard a Bonanza (Beech A-36) pilot announce a "mayday" call on the common traffic advisory frequency, indicating the airplane's engine was on fire. A review of aircraft records revealed the pilot had purchased the airplane in October 2018 and had flown the airplane on two flight that month for a flight time of 5.0 hours. The records noted that the engine was last overhauled on December 9, 2010, at a tachometer time of 1,585.1 hours and had accumulated 412.2 hours at the time of the October 2018 annual inspection. The airplane was equipped with a Lycoming TIO-540 reciprocating engine and a Hartzell propeller under Supplemental Type Certificate SA762NW, Machen Inc. engine and propeller conversion. The airplane's initial impact point was the edge of a field about 1 mile north of T82; the airplane then impacted a slightly elevated country road and came to rest upright. A post-crash fire consumed a majority of the airframe. The airplane was initially recovered to an impound yard. After the government shutdown, the wreckage was then moved to aircraft salvage facility near Lancaster, Texas, where an examination was conducted by the National Transportation Safety Board (NTSB) Investigator-in-Charge (IIC), and technical representatives from the engine and airframe manufacturers. A postaccident examination revealed that the engine exhibited fire damage. An attempt to manually rotate the engine was limited due to internal binding. Disassembly of the engine revealed a broken camshaft and crankshaft. The broken parts, along with the cylinders and pistons were sent to the NTSB Material Laboratory for examination. The laboratory noted crack arrest marks in the crankshaft, consistent with fatigue. The examination also noted that the fatigue initiated in the fillet radius at the forward end of the number 6 connecting rod journal. Multiple crack origins and prominent crack arrest lines were consistent with the relatively high stress associated with crack initiation.