NTSB Factual Report

On December 17, 2006, at 1454 eastern standard time, a Scharnhorst RV-4 experimental airplane, N360WS, registered to a private owner, operating as a 14 CFR Part 91 personal flight, had a loss of engine power in cruise flight, and made a forced landing to an open field near Hoschton, Georgia. Visual meteorological conditions prevailed and no flight plan was filed. The airplane received substantial damage. The commercial pilot and one passenger reported minor injuries. The flight originated from Winder Barrow Airport, Winder, Georgia, on December 17, 2006, at 1415.

The pilot stated he was in cruise flight at 2,500 feet en-route to his destination airport when the engine lost power. The pilot attempted an engine restart with negative results. The pilot made a forced landing to an open field and observed terraces on final approach. The airplane touched down, collided with a terrace, and nosed over inverted.

The aircraft logbooks were not located at the accident site and were provided to the FAA by the registered owner. The last condition inspection was conducted on June 14, 2006, at 251.7 hours. The airplane has flown 26.2 hours since the annual inspection. The engine was assembled by an Airframe and Power Plant Mechanic using a garage repair order on May 5, 1999, and had 0 hours since major overhaul. The engine and airframe has 340 total hours.

Review of Airflow Performance Inc., invoice No. 99-C4740 revealed a fuel injection system was shipped to the registered owner on July 30, 1999. The registered owner noticed a fuel stain on the engine block below the flow divider on November 22, 2002. The registered owner tested the fuel system for leaks, and a leak was present in the flow divider. The flow divider was removed by the registered owner and sent to Airflow Performance on November 27, 2002.

Review of Airflow Performance, Inc Invoice No. Y2-C6753, dated December 6, 2002 states:

"1 Purge Valve/Flow Divider (AP-486) Assembly

Flow Test Flow Divider, Repair And Flow Test

1 Replace Diaphragm"

The Work No. 3249, Job Progress Sheet, dated December 4, 2002 states:

"1 Replace Diaphragm and Test." The description was signed off by CW.

"Relock Wire" The description was signed off by CW.

The assembly was returned to the registered owner and reinstalled on the engine by the registered owner on December 15, 2002.

The engine logbook revealed the engine/aircraft was stored from March 1, 2004, to May 10, 2005. The complete fuel injection system was sent to the manufacturer for recalibration in January 2005.

Airflow Performance Work Order 3597, dated January 13, 2005, does not indicate the lock wire was reinstalled and signed off by the technician with the initials KD, as required by the systems installation and service manual. The complete assembly was sent back to the registered owner on January 18, 2005. The registered owner reinstalled the assembly on the aircraft on May 12, 2005.

Review of "AIRFLOW PERFORMANCE HIGH PERFORMANCE FUEL METERING SYSTEMS INSTALLATION AND SERVICE MANUAL" states on page 28, paragraph 3-41 Purge Valve Installation Procedures…." Leak check all connections and plumbing before starting engine. Lock wire all hardwire. Make sure to lock wire the stop screw." Appendix I of the Purge Valve Installation states on page I-1, paragraph 2, "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." A WARNING in AIRFLOW PERFORMANCE FUEL METERING INSTALLATION AND SERVICE MANUAL states,... "Your unit has been lock wired and sealed. Do not remove the seal as this will result in changing the calibration."

The registered owner stated, "During installation or removal of the Flow Divider/Purge Valve assembly, it is not necessary to remove the safety wires in the Purge Valve mounting bolts or the stop screw. At no time did the builder ever remove the safety wire from the Purge Valve mounting bolts or stop screw."

Airflow Performance stated in a e-mail to the NTSB that "all components that left their shop were assembled, tested and tested in limits as well as lock wired. The customer had to install these components and hook up the appropriate linkages and hoses on the engine. The parts were received from the customer assembled. The only part we took apart to repair was the flow divider to install a new diaphragm on December 4th, 2002. All other parts were just tested as received." Airflow Performance did not mentioned the maintenance activity that was performed on January 13, 2005, Work Order No. 3597 in their e-mail.

Examination of the airplane revealed the engine mounts were bent and the firewall was damaged. The upper and lower engine cowling were damaged. The propeller remained attached to the crankshaft propeller flange. The composite spinner was destroyed and neither propeller blade was damaged.

The cabin area was not damaged except for the canopy, which was broken out and the roll bar was bent down. The throttle and mixture control was at mid range. The fuel selector valve was in the both position. The ignition switch was in the off position. The Airflow Performance High Performance Fuel Metering System Purge Valve was in the open position. Continuity of the flight controls was confirmed from the forward control stick aft to all flight control surfaces. The aircraft registration and airworthiness certificate was in the airplane. The left and right main landing gear remained attached to the airframe.

The right wing remained attached to the airframe and was not damaged. The right aileron was attached to its attachment points and the flaps were not extended. The right fuel tank was not ruptured. The right fuel cap was removed and had a tight seal. Fifteen gallons of fuel was present in the right fuel tank.

The empennage was damaged about two feet forward of the vertical fin. The top of the vertical fin and rudder was crushed downward about six inches. The rudder assembly remained attached at all hinge points and the rudder balance weight remained intact. The left and right horizontal stabilizers were not damaged. The left elevator remained attached to the horizontal stabilizer and was bent upward. The left aileron trim remained attached to the left elevator. The right horizontal stabilizer was not damaged. The right elevator was not damaged and remained attached to the horizontal stabilizer. The right elevator was bent upwards and remained attached to the right horizontal stabilizer. The tail wheel remained attached to the empennage. The ELT had activated and was turned off.

The left wing remained attached to the airframe and pushed aft. The wing tip was bent downward. The left aileron was attached to its attachment points and the flaps were not extended. The left fuel tank was not ruptured. The left fuel cap was removed and had a tight seal. Eleven gallons of fuel was present in the left fuel tank.

The airplane was recovered by Atlanta Air recovery to Griffin, Georgia. An engine run was conducted on December 21, 2006, under the supervision of the FAA with the engine still installed on the airplane. The airplane engine controls, propeller system, battery source, and electric fuel pump were used. An alternate fuel source was supplied. Several attempts to start the engine were unsuccessful.

Examination of the purge valve/flow divider revealed the assembly was mounted to the engine with two-quarter inch bolts, two spacers, and two lock nuts through the top of the engine case halves. An aluminum bracket was bolted to the top of the distribution block/flow divider and the four mount screws were safety wired.

Further investigation revealed the Airflow Performance Fuel Injection Purge Valve stop screw was loose, not safetied, and the valve body had migrated out approximately one-eighth of an inch. The purge valve was removed from the system by rerouting the fuel line from the purge valve directly to the flow divider/distribution block. The engine was started, ran at idle power, was advanced to a high power setting, and shut down with the mixture control.

The airplane was released to Atlanta Air Recovery on December 21, 2006. The FAA maintained custody of the aircraft logbooks and Airflow Performance Fuel Injection Purge Valve.

NTSB Probable Cause

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.