NTSB Identification: LAX96LA005.
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Accident occurred Monday, October 09, 1995 in TUCSON, AZ
Probable Cause Approval Date: 04/29/1996
Aircraft: PIPER J3C-65, registration: N59931
Injuries: 1 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.

During the takeoff initial climb, the engine lost power and the airplane collided with trees short of the intended forced landing area. Examination of the airplane revealed that it was using automotive gasoline. During a test run the engine operated at full rpm, then began to lose power output (300 to 400) rpm. Carburetor heat was applied, and the engine gained partial return of power. When the carburetor heat was removed, the engine returned to the previous running condition. A float level problem was suspected, and the carburetor was sent out for analysis at an overhaul shop. The aircraft owner subsequently decided to replace the carburetor with a different type, and the accident carburetor was lost in the overhaul process. Information Letter 8401 (12/15/84) from the EAA advises of a long standing problem with rubber tipped needle valves which swell when exposed to automotive fuels. The letter states that slow degeneration of in-flight engine power has been observed when the rubber needle valve tips swell and decrease the orfice size at the carburetor inlet. Sudden losses of power have also been reported during takeoffs in aircraft following a long period of inactivity.

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

fuel starvation due to swelling of the carburetor needle valve tip, which restricted the fuel flow to the carburetor inlet. A factor in the accident was the use of automotive gasoline.

Full narrative available

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