NTSB Identification: LAX96LA180.
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Accident occurred Sunday, April 28, 1996 in MAMMOTH LAKES, CA
Probable Cause Approval Date: 01/17/1997
Aircraft: Cessna 320, registration: N5752X
Injuries: 3 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 performed a static engine run-up, and with no discrepancies noted, he commenced the takeoff. Upon reaching between 25 and 50 feet above the runway during the initial climb, the normal 35 inches of manifold pressure (MP) was observed being produced by the left engine. However, the right engine only produced between 18 and 20 inches of MP. The airplane veered right and settled into the rough/uneven terrain near the airport. The airport's elevation is 7,128 feet mean sea level, and the calculated density altitude was over 8,200 feet. An examination of the right engine's turbocharger assembly revealed the absolute pressure controller was set lower than the manufacturer's specifications required. Also, the wastegate butterfly valve was mechanically binding in its housing and would not fully close.

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

the partial failure of the right engine turbocharger wastegate butterfly valve to fully close due to mechanical binding and the low setting of its associated absolute pressure controller. A related factor was the high density altitude which reduced the engine's ability to produce adequate manifold pressure.

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