NTSB Identification: LAX92FA374.
The docket is stored on NTSB microfiche number 48326.
Accident occurred Wednesday, September 02, 1992 in CONCORD, CA
Probable Cause Approval Date: 09/14/1993
Aircraft: PIPER PA-23-160, registration: N4305Y
Injuries: 2 Fatal.
NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.
The following Brief was modified on April18, 2007, as a result of new information provided to the NTSB.
THE AIRCRAFT COLLIDED WITH A BRIDGE WHILE TRYING TO RETURN TO THE AIRPORT AFTER REPORTING AN EMERGENCY DURING THE PREVIOUS TOUCH AND GO LANDING. WITNESSES INDICATED BOTH ENGINES SOUNDED LIKE THEY WERE RUNNING AND BOTH PROPELLERS WERE TURNING. THE LEFT ENGINE PROPELLER WAS FOUND FEATHERED AFTER THE ACCIDENT. INVESTIGATION REVEALED A 1.75 INCH OD PLUG INSTALLED IN THE CRANKSHAFT TO SEPARATE OIL PRESSURE FROM THE PROPELLER GOVERNOR AND THE ENGINE CRANKCASE WAS BLOWN AFT DAMAGING THE NUMBER ONE ROD CONNECTING JOURNAL OIL TRANSFER TUBE. EXAMINATION OF THE PLUG DISCLOSED THAT IT WAS INSTALLED BACKWARDS.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The following Probable Cause was modified on April18, 2007, as a result of new information provided to the NTSB.
THE IMPROPER INSTALLATION OF THE 1.75 INCH OD PLUG IN THE CRANKSHAFT BY UNKNOWN MAINTENANCE PERSONNEL WHICH RESULTED IN AN INADVERTENT FEATHERING OF THE LEFT ENGINE PROPELLER.
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