NTSB Identification: LAX04LA251.
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Accident occurred Monday, June 28, 2004 in Perris, CA
Probable Cause Approval Date: 07/07/2005
Aircraft: SOCATA TB-20, registration: N110U
Injuries: 5 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 airplane collided with ground obstructions during a forced landing following a catastrophic engine failure due to oil exhaustion during cruise flight. Just after achieving cruise altitude the pilot was scanning the cockpit gauges and he noticed the oil pressure gauge indicating a loss of pressure, with the oil warning light flickering intermittently. About 5 minutes later, the engine started to vibrate, and subsequently seized, making a loud bang. The airplane began to descend about 1,000 feet per minute, and the pilot selected a dirt field to perform an emergency landing. During the landing roll, the airplane impacted a berm. An engine examination revealed that the inside top of the engine cowling showed a concentration of oil near the firewall on the left side, which is the approximate location of the vacuum pump. Removal of the vacuum pump revealed an oily film on both sides of the pump gasket, which is seated between the vacuum pump flange and the engine accessory case flange. The vacuum pump had been installed about 0.5 hours prior to the accident. The mechanic who installed the pump said he used the gasket that was supplied with the pump. The manufacturer of the vacuum pump reported that they supply a gasket (part number AS3491-01) with their pump. In the TB-20 parts manual, the airplane manufacturer specifies that the gasket required is part number Z00.N7423254013, which they cross-reference with Textron Lycoming part number 8313. The investigation was unable to cross-reference or establish an equivalency between the AS3491-01 gasket supplied by the pump manufacturer with either the Lycoming or Socata specified gasket.

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

A loss of engine power due to oil exhaustion as a result of the mechanic's use of an incorrect gasket during the installation of the vacuum pump.

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