Narrative:

The problem arose on a flight from sjc to mammoth airport. It was a morning flight and the aircraft was filled with 4 passenger. The passenger in the front seat was a pilot with 1700 hours of flight time. About 15 mi west of mariposa yosemite airport I began a 500 FPM climb. When the aircraft was approaching 5500' from 3500', the right engine began to vibrate. Seconds later the cylinder blew completely off the engine block. The pilot was extremely startled by the explosion, and almost automatically began a mental engine out checklist. The problem was feathered and the fuel was shut off. A couple mins later the smoke from the oil on the hot manifold and exhaust began filling the cockpit through vents and openings. This was the most exciting thing that happened, due to the fact that it began to get so thick that it was hard to breathe. The pilot/passenger on the right opened a side window and the pilot/left seat dropped the landing gear once an airport was sighted. The dropping of the gear aided in blowing the smoke from the engine compartment. As the smoke cleared the cockpit the pilots felt much more at ease and made a safe single engine landing at mariposa airport. In examining the right engine, it was noticed that one of the main bolts holding the cylinder on the engine block had loosened and came off. This caused the vibration and the eventual failure. Lowering the landing gear allowed much of the smoke to escape and helped clear the cockpit. Altitude permitting, this is a wise consideration.

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Original NASA ASRS Text

Title: ACFT EXPERIENCED ENGINE FAILURE AND SMOKE IN COCKPIT CABIN. DIVERTED AND MADE EMERGENCY LNDG.

Narrative: THE PROB AROSE ON A FLT FROM SJC TO MAMMOTH ARPT. IT WAS A MORNING FLT AND THE ACFT WAS FILLED WITH 4 PAX. THE PAX IN THE FRONT SEAT WAS A PLT WITH 1700 HRS OF FLT TIME. ABOUT 15 MI W OF MARIPOSA YOSEMITE ARPT I BEGAN A 500 FPM CLB. WHEN THE ACFT WAS APCHING 5500' FROM 3500', THE RIGHT ENG BEGAN TO VIBRATE. SECS LATER THE CYLINDER BLEW COMPLETELY OFF THE ENG BLOCK. THE PLT WAS EXTREMELY STARTLED BY THE EXPLOSION, AND ALMOST AUTOMATICALLY BEGAN A MENTAL ENG OUT CHKLIST. THE PROB WAS FEATHERED AND THE FUEL WAS SHUT OFF. A COUPLE MINS LATER THE SMOKE FROM THE OIL ON THE HOT MANIFOLD AND EXHAUST BEGAN FILLING THE COCKPIT THROUGH VENTS AND OPENINGS. THIS WAS THE MOST EXCITING THING THAT HAPPENED, DUE TO THE FACT THAT IT BEGAN TO GET SO THICK THAT IT WAS HARD TO BREATHE. THE PLT/PAX ON THE RIGHT OPENED A SIDE WINDOW AND THE PLT/LEFT SEAT DROPPED THE LNDG GEAR ONCE AN ARPT WAS SIGHTED. THE DROPPING OF THE GEAR AIDED IN BLOWING THE SMOKE FROM THE ENG COMPARTMENT. AS THE SMOKE CLRED THE COCKPIT THE PLTS FELT MUCH MORE AT EASE AND MADE A SAFE SINGLE ENG LNDG AT MARIPOSA ARPT. IN EXAMINING THE RIGHT ENG, IT WAS NOTICED THAT ONE OF THE MAIN BOLTS HOLDING THE CYLINDER ON THE ENG BLOCK HAD LOOSENED AND CAME OFF. THIS CAUSED THE VIBRATION AND THE EVENTUAL FAILURE. LOWERING THE LNDG GEAR ALLOWED MUCH OF THE SMOKE TO ESCAPE AND HELPED CLEAR THE COCKPIT. ALT PERMITTING, THIS IS A WISE CONSIDERATION.

Data retrieved from NASA's ASRS site as of August 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.