NTSB Identification: LAX91LA347.
The docket is stored on NTSB microfiche number 44885.
Accident occurred Sunday, August 04, 1991 in NAPA, CA
Probable Cause Approval Date: 05/27/1993
Aircraft: EXPERIMENTAL RV4, registration: N835B
Injuries: 2 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

THE PILOT SAID THE AIRCRAFT WAS IN CRUISE FLIGHT WHEN THE OIL PRESSURE SUDDENLY DROPPED. THE ENGINE BEGAN TO RUN ROUGH, THEN SEIZED ALTOGETHER. THE AIRCRAFT WAS CLOSE TO A PRIVATE AIRSTRIP AND THE PILOT WAS ATTEMPTING A FORCED LANDING ON THE AIRSTRIP. THE AIRCRAFT LANDED SHORT OF THE RUNWAY IN A GRAPE VINEYARD. RESPONDING SHERIFF'S DEPUTIES REPORTED THAT THE ENTIRE BELLY OF THE AIRCRAFT WAS HEAVILY COATED WITH OIL. FAA AIRWORTHINESS INSPECTORS EXAMINED THE AIRCRAFT AND FOUND THAT AN AUTOMOTIVE FRAM OIL FILTER WAS INSTALLED ON THE ENGINE, WITH SOME PLUMBING CHANGES. THE INSPECTOR STATED THAT THE OIL FILTER FAILED TO BYPASS OIL. THE OUTSIDE CASE OF THE FILTER WAS FOUND TO HAVE EXPANDED TO ABOUT 125 PERCENT OF NORMAL SIZE AND WAS LEAKING OIL.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

THE INSTALLATION OF A NON COMPATIABLE OIL FILTER AND SYSTEM PLUMBING CHANGES WHICH INDUCED THE OIL EXHAUSTION EVENT RESULTING IN A FORCED LANDING AND IN FLIGHT COLLISION WITH TERRAIN.

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