In-Flight Cylinder Separation and Fire During Air Taxi Flight Leads to Crash Landing (N4839S)

Accident Details

An airplane operating under Part 135 as an on-demand air taxi flight experienced a physical separation of the No. 3 cylinder and piston assembly while in flight. This event led to an in-flight fire. The aircraft subsequently crash landed on terrain near the shoreline of a body of water. Of the four occupants on board, one survived the crash. The surviving passenger was unable to recall the events leading up to the accident.

Maintenance History

Maintenance records indicated that the No. 3 and No. 4 cylinder assemblies had been installed approximately 220 flight hours before the accident. This maintenance was performed without removing the engine from the airplane. No problems with the airframe or engine were recorded following the cylinder change.

Engine Examination

Post-accident inspection of the engine revealed fatigue cracks in the engine case beneath the No. 3 cylinder. Magnified inspection of the case showed wear and deformation damage at the location where the cylinder's holding flange and inner skirt would normally be positioned, consistent with movement of the cylinder relative to the case. Additionally, mechanical damage was evident on the threads of the studs and both through-bolts.