NTSB Identification: LAX06CA191.
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Accident occurred Sunday, June 04, 2006 in Alpine, CA
Probable Cause Approval Date: 10/03/2006
Aircraft: Piper PA-28R-200, registration: N4438T
Injuries: 2 Uninjured.

NTSB investigators used data provided by various entities, including, but not limited to, the Federal Aviation Administration and/or the operator and did not travel in support of this investigation to prepare this aircraft accident report.

The airplane lost oil pressure in flight and was damaged in an encounter with rough terrain during a forced landing. The oil sump quick drain valve was replaced the day of the accident. On the first flight following the replacement, 2 quarts of oil were lost. The aviation maintenance technician retorqued the valve and the maintenance test flight was successful. The instructor departed on a local instructional flight with a student and about 50 minutes into the flight, oil pressure decreased and the engine revolutions per minute were fluctuating. The instructor shut down the engine and force landed the airplane. The installed oil sump quick drain valve, a Safe-Air 5000, had an extension of 1.9 inches. The approved Piper quick drain valve (Piper part number 492-172V) has an extension of 0.21-inch. Airworthiness Directive 81-11-02 R1 states that unapproved drain valves can cause inadvertent draining of oil when the gear is retracted and that only Piper approved parts should be used for the oil sump quick drain installation in this airplane model.

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

a loss of engine power due to the aviation maintenance technician's failure to install the correct oil sump quick drain, which resulted in the inadvertent draining of engine oil during flight.

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