NTSB Factual Report

On September 6, 2013, about 1445 eastern daylight time, an experimental amateur-built Sonex, N293SX, was substantially damaged during a forced landing following a total loss of engine power near Waxhaw, North Carolina. The private pilot incurred minor injuries. Visual meteorological conditions prevailed, and no flight plan was filed for the flight, which had originated from Anson County Airport (AFP), Wadesboro, North Carolina, about 1400, and was destined for Triple Tree Airport (SC00), Woodruff, South Carolina. The personal flight was conducted under the provisions of Title 14 Code of Federal Regulations Part 91.

Following an uneventful first flight of the day from Cox Airport (NC81), Apex, North Carolina, to AFP, the pilot serviced the airplane with 5.6 gallons of 100LL aviation fuel before preparing to depart for SC00. The pilot and a friend flying a second amateur-built experimental airplane then departed and climbed to 3,000 feet msl. After establishing the airplane at the cruise altitude, the pilot leaned the engine's fuel mixture, initially reaching a high exhaust gas temperature of 1,415 degrees Fahrenheit, and ultimately to temperatures between 1,325 and 1,350 degrees. About 15 to 20 minutes later, the pilot noticed that the engine rpm had dropped from the previously established 2,600 to 1,800. The engine continued to operate at this reduced power setting for between 30 and 60 seconds before it ceased producing power completely.

The pilot began diverting to a nearby airport, and during the descent attempted to restart the engine 3 times to no avail. About 2 miles from the diversionary airport, the pilot realized that the airplane did not have sufficient altitude available to reach the runway, so he began to slow the airplane to an airspeed just above the stall speed in preparation for impact with the trees below. About 5 feet above the trees, the airplane stalled and the right wing dropped and contacted the trees, resulting in substantial damage to the airframe. After coming to rest, the pilot utilized a handheld radio to contact the pilot of the other airplane to request assistance.

The experimental amateur-built airplane was equipped with a Jabiru 3300L engine, which had been modified with the installation of a Simple Digital System EM-5 electronic fuel injection system. The airplane's airworthiness certificate was issued on October 17, 2008, and the pilot/builder/owner/repairman completed its most recent condition inspection on April 25, 2013. At the time of the accident, the airframe and engine had accumulated 189 total hours of operation.

The engine was not able to be test run following the accident due to impact-related damage. A detailed examination of the engine revealed that the insulation of the fuel injection system's crankshaft position sensor cable had melted, and the sensor's power wire had electrically shorted to the engine block. When power was applied to the fuel injection system, it immediately entered a "safe shut-down" state. When the damaged cable was disconnected from the system and removed, the system powered normally, but reported the missing sensor. Finally, the cable was replaced, and a subsequent test of the system found that it operated normally when rotating the propeller by hand.

The pilot stated that he believed that the failure of the cable's insulation was precipitated by its proximity to the engine exhaust system. He further added that it was not customary for him to allow the exhaust gas temperature to reach 1,415 degrees, and that during this flight the brief temperature excursion combined with the cable's proximity to the exhaust system ultimately lead to the rapid breakdown of the insulation.

NTSB Probable Cause

The pilot/owner/builder’s improper routing of the engine’s crankshaft position sensor cable next to the engine’s exhaust system, which resulted in a total loss of engine power in flight.