Piper PA-34-200T N31743 accident near Johnstown, New York

Probable cause

The pilot's loss of control due to spatial disorientation in instrument meteorological conditions, which resulted in an exceedance of the airplane's design stress limitations, and a subsequent in-flight breakup.

NTSB analysis

The volunteer medical transport flight was established on course toward an en route navigational fix. Upon reaching the fix, the flight was expected to continue toward the initial approach fix at the destination airport in preparation for an instrument approach; however, about 5 miles southeast of the en route fix, the airplane began to deviate off course. When asked by an air traffic controlller about the reason for the deviation, the pilot stated that the airplane had turned "the wrong way" and indicated that he had incorrectly loaded the instrument approach into the airplane's GPS. The controller provided a vector to the pilot to return the airplane to the previously established course, and the pilot acknowledged. About 1 minute later, radar contact with the airplane was lost.

Radar data indicated that the airplane entered a rapidly-descending left turn in the final moments of the flight during which it reached an estimated 80-degree left bank, lost about 3,700 feet of altitude in 36 seconds, and accelerated to an airspeed of about 240 knots before breaking up. All fracture surfaces exhibited failure characteristics consistent with overload. Examination of the engines revealed no anomalies. Analysis of weather information for the area of the accident site indicated that the airplane was likely operating in instrument meteorological conditions at the time of the accident but that icing conditions likely were not present in the immediate vicinity.

The restricted visibility, turbulence, the airplane's unexpected off-course turn, the pilot's resulting distraction with the operation and configuration of the GPS, and possibly his sudden need to fly the airplane without the aid of the autopilot would have been conducive to the development of spatial disorientation. The resulting ground track, rapid turning descent, and breakup were consistent with a loss of control as a result of spatial disorientation.

Text from the NTSB. Open the NTSB docket for ERA13FA253 for the full record.