What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
Operator experienced engine fire upon start up which caused minor damage to the engine compartment.
The aircraft had been flown recently and was hot when pilot tried to start engine. When initially started the engine ran rough for a few seconds and then shut down.
Another attempt to start the engine was unsucessful and the pilot waited half a minute to try running starter again. Upon third attempt to start engine observers on the ramp yelled that there was fire.
The pilot shut down engine and controls while the second pilot exited the aircraft and was able to extinguish the flames coming from the engine cowling area with the aircraft fire extinguisher.
Aircraft was inspected by FAA inspector and operator maintenance personnel. After inspecting the engine compartment it became apparent that the fire was caused by fuel weeping from the area around carburetor fuel inlet screen gasket.
No fuel was visible with aircraft sitting with fuel selector turned on and no pressure on the engine fuel system. However, when the aircraft electrical engine fuel pump was activated fuel began to weep between the copper locking gasket under the seat of the carburetor fuel inlet screen and the carburetor housing.
While disassembling the fuel inlet filter screen there was found to be an interference fit between the copper (lock) gasket and the fuel inlet screen when it was threaded into the mounting boss. This interference allowed the copper gasket to bend and stopped the fuel inlet screen from fully tightening against the carburetor boss face. The interference was not visible nor able to be physically determined until fuel pressure was applied to the system.
As the FAA filed it
OPERATOR EXPERIENCED ENGINE FIRE UPON START UP WHICH CAUSED MINOR DAMAGE TO THE ENGINE COMPARTMENT.
THE AIRCRAFT HAD BEEN FLOWN RECENTLY AND WAS HOT WHEN PILOT TRIED TO START ENGINE. WHEN INITIALLY STARTED THE ENGINE RAN ROUGH FOR A FEW SECONDS AND THEN SHUT DOWN.
ANOTHER ATTEMPT TO START THE ENGINE WAS UNSUCESSFUL AND THE PILOT WAITED HALF A MINUTE TO TRY RUNNING STARTER AGAIN. UPON THIRD ATTEMPT TO START ENGINE OBSERVERS ON THE RAMP YELLED THAT THERE WAS FIRE.
THE PILOT SHUT DOWN ENGINE AND CONTROLS WHILE THE SECOND PILOT EXITED THE AIRCRAFT AND WAS ABLE TO EXTINGUISH THE FLAMES COMING FROM THE ENGINE COWLING AREA WITH THE AIRCRAFT FIRE EXTINGUISHER.
AIRCRAFT WAS INSPECTED BY FAA INSPECTOR AND OPERATOR MAINTENANCE PERSONNEL. AFTER INSPECTING THE ENGINE COMPARTMENT IT BECAME APPARENT THAT THE FIRE WAS CAUSED BY FUEL WEEPING FROM THE AREA AROUND CARBURETOR FUEL INLET SCREEN GASKET.
NO FUEL WAS VISIBLE WITH AIRCRAFT SITTING WITH FUEL SELECTOR TURNED ON AND NO PRESSURE ON THE ENGINE FUEL SYSTEM. HOWEVER, WHEN THE AIRCRAFT ELECTRICAL ENGINE FUEL PUMP WAS ACTIVATED FUEL BEGAN TO WEEP BETWEEN THE COPPER LOCKING GASKET UNDER THE SEAT OF THE CARBURETOR FUEL INLET SCREEN AND THE CARBURETOR HOUSING.
WHILE DISASSEMBLING THE FUEL INLET FILTER SCREEN THERE WAS FOUND TO BE AN INTERFERENCE FIT BETWEEN THE COPPER (LOCK) GASKET AND THE FUEL INLET SCREEN WHEN IT WAS THREADED INTO THE MOUNTING BOSS. THIS INTERFERENCE ALLOWED THE COPPER GASKET TO BEND AND STOPPED THE FUEL INLET SCREEN FROM FULLY TIGHTENING AGAINST THE CARBURETOR BOSS FACE. THE INTERFERENCE WAS NOT VISIBLE NOR ABLE TO BE PHYSICALLY DETERMINED UNTIL FUEL PRESSURE WAS APPLIED TO THE SYSTEM.
Other reports on N4133K · 1
Matched to the same aircraft by N-number and date.