What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
(-23) The pilot was performing an engine run up when after bring the throttles back the left engine began to run rough. He advanced the throttles and the engine began to run smoothly, again the throttles were returned to idle and the engine quit. At this point the pilot attempted to restart the left engine, but it wouldn't start. The pilot primed the engine, restarted and again it failed to start. Feeling that the engine maybe flooded the pilot pulled the left mixture lever to cutoff and attempted another restart as the engine cranked over he advanced the mixture lever at this point there was an explosion in the left engine nacelle. Inboard and outboard hinged nacelle doors departed the cowling. The top cowling was blown into an upside down "v" shape and the bottom cowling had wrinkle damage. Inspection of the inside of the nacelle area revealed no evidence of a fire. The engine itself revealed no visible evidence of a fire. The engine and its major components were intact with the exception of the oil filler cap and the intake filter. The oil filler cap though still attached to the engine filler neck was deformed due to pressure from within the crankcase. The air filter housing cover showed evidence of internal pressure because the seals had been blown from their correct position. The intake air filter also showed evidence of damage due to being partially blown from its housing in the opposite direction of normal operation. privacy data omitted The owner had a mechanic remove the spark plugs and perform a cylinder compression checks, all cylinders were found to be acceptable. Owner elected to try to run the engine, it started and ran with out incident. Owner stated that he was going to contact teledyne Continental for further inspection criteria. Note: enclosed in this package is a disk of photographs.
As the FAA filed it
(-23) THE PILOT WAS PERFORMING AN ENGINE RUN UP WHEN AFTER BRING THE THROTTLES BACK THE LEFT ENGINE BEGAN TO RUN ROUGH. HE ADVANCED THE THROTTLES AND THE ENGINE BEGAN TO RUN SMOOTHLY, AGAIN THE THROTTLES WERE RETURNED TO IDLE AND THE ENGINE QUIT. AT THIS POINT THE PILOT ATTEMPTED TO RESTART THE LEFT ENGINE, BUT IT WOULDN'T START. THE PILOT PRIMED THE ENGINE, RESTARTED AND AGAIN IT FAILED TO START. FEELING THAT THE ENGINE MAYBE FLOODED THE PILOT PULLED THE LEFT MIXTURE LEVER TO CUTOFF AND ATTEMPTED ANOTHER RESTART AS THE ENGINE CRANKED OVER HE ADVANCED THE MIXTURE LEVER AT THIS POINT THERE WAS AN EXPLOSION IN THE LEFT ENGINE NACELLE. INBOARD AND OUTBOARD HINGED NACELLE DOORS DEPARTED THE COWLING. THE TOP COWLING WAS BLOWN INTO AN UPSIDE DOWN "V" SHAPE AND THE BOTTOM COWLING HAD WRINKLE DAMAGE. INSPECTION OF THE INSIDE OF THE NACELLE AREA REVEALED NO EVIDENCE OF A FIRE. THE ENGINE ITSELF REVEALED NO VISIBLE EVIDENCE OF A FIRE. THE ENGINE AND ITS MAJOR COMPONENTS WERE INTACT WITH THE EXCEPTION OF THE OIL FILLER CAP AND THE INTAKE FILTER. THE OIL FILLER CAP THOUGH STILL ATTACHED TO THE ENGINE FILLER NECK WAS DEFORMED DUE TO PRESSURE FROM WITHIN THE CRANKCASE. THE AIR FILTER HOUSING COVER SHOWED EVIDENCE OF INTERNAL PRESSURE BECAUSE THE SEALS HAD BEEN BLOWN FROM THEIR CORRECT POSITION. THE INTAKE AIR FILTER ALSO SHOWED EVIDENCE OF DAMAGE DUE TO BEING PARTIALLY BLOWN FROM ITS HOUSING IN THE OPPOSITE DIRECTION OF NORMAL OPERATION. ^PRIVACY DATA OMITTED^ THE OWNER HAD A MECHANIC REMOVE THE SPARK PLUGS AND PERFORM A CYLINDER COMPRESSION CHECKS, ALL CYLINDERS WERE FOUND TO BE ACCEPTABLE. OWNER ELECTED TO TRY TO RUN THE ENGINE, IT STARTED AND RAN WITH OUT INCIDENT. OWNER STATED THAT HE WAS GOING TO CONTACT TELEDYNE CONTINENTAL FOR FURTHER INSPECTION CRITERIA. NOTE: ENCLOSED IN THIS PACKAGE IS A DISK OF PHOTOGRAPHS.