Incident Overview
The aircraft broke up in flight when the left wing and tail section separated. Post-accident examination of the wreckage revealed a progressive rupture of the right engine main fuel supply line. Only trace amounts of fuel were found in the fuel lines, and there was no rotational damage to the right engine. Evidence of a long-term fuel leak surrounded the ruptured line. The right propeller was not feathered.
Structural Findings
The left wing D-tube rib at station 127 exhibited compressive buckling. The left wing fractures were oriented upward, while the horizontal stabilizer deformation was downward. These patterns indicate structural overload.
Pilot Background
The pilot had experienced an actual loss of engine power in the same airplane 17 months prior to this accident; during that event, he feathered the incorrect propeller. A mechanic and an FAA safety counselor who were familiar with the pilot described him as prone to disorientation and reliant on GPS for navigation. Five months before the accident, the pilot stated that he did not feel his instrument flying skills were proficient and desired training.
Weather and Flight Intent
On the day of the accident, weather conditions were visual meteorological conditions (VMC) with layered clouds above 2,200 feet mean sea level. The pilot stated to the FAA weather briefer that he wanted to make the flight under visual conditions. The flight route and altitude were unknown.
Probable Cause
The National Transportation Safety Board determined the probable cause(s) of this accident to be: The rupture of the right engine fuel supply line as a result of inadequate inspection by the pilot/mechanic, and the pilot's excessive pull up which resulted in exceeding the design stress limits of the airplane. Factors were the improper emergency procedures and failure to feather the propeller.