NTSB Identification: ATL07LA028.
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Accident occurred Sunday, December 17, 2006 in Hoschton, GA
Probable Cause Approval Date: 04/25/2007
Aircraft: Scharnhorst RV-4, registration: N360WS
Injuries: 2 Minor.
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 stated he was in cruise flight at 2,500 feet when the engine lost power. He attempted an engine restart with negative results, and made a forced landing in a field. During landing, the airplane collided with a terrain terrace/berm and nosed over. The airplane was recovered, and an engine run was conducted under the supervision of the FAA. The airplane's engine controls, propeller system, battery source, and electric fuel pump were used, and an alternate fuel source was supplied to the engine. Several attempts to start the engine were unsuccessful. An examination of the Airflow fuel injection system was found to be missing the necessary safety wire on the purge valve stop screw. The stop screw had migrated out of the purge valve housing approximately one-eighth of an inch. The purge valve was isolated from the fuel system by routing the fuel supply line directly to the fuel flow divider/distribution block. The engine was started, ran at idle power, advanced to a high power setting, and shut down with the mixture control. Examination of the airplane log books, additional documents maintained by the registered owner, and work orders from the manufacturer, revealed the purge valve and distribution block had been returned to the manufacturer as a complete assembly on two occasions by the registered owner. The purge valve and distribution block were repaired, sent back to the registered owner as a complete assembly, and installed on the airplane by the registered owner. The manufacturer's installation and service manual states, "Leak check all connections and plumbing before starting engine. Lock wire all hardware. Make sure to lock wire the stop screw. If removal of the valve is necessary make sure to relock wire the purge valve stop screw. Failure to do so will result in sudden stoppage of the engine if the screw backs out." The registered owner stated he did not remove the safety wire from the purge valve mounting bolts or stop screw. The manufacturer stated all components that left their shop were assembled, tested, and tested in limits, as well as lock wired. Review of the Work Order/Job Progress Sheet used by the manufacturer during the assembly of the purge valve on December 4, 2002, revealed the relock wire had been signed off by the technician as having been completed. The Work Order/Job Progress Sheet used by the manufacturer during the assembly of the purge valve by the technician during the last repair on January 13, 2005, was not signed off by the technician as having been safety wired as required by the manufacturer's installation and service manual.
The National Transportation Safety Board determines the probable cause(s) of this accident to be: The failure of the manufacturer to safety wire the purge valve stop screw during maintenance resulting in a total loss of engine power in cruise flight due to fuel starvation. This resulted in a forced landing, on-ground collision with a berm/terrace, and subsequent nose over. Full narrative available
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