Amateur-built SWEARINGEN SX300 N3ZX accident near Milford, Iowa

Probable cause

A loss of control for undetermined reasons.

NTSB analysis

The accident occurred during the instrument rated pilot's return flight home after an avionics upgrade, including the installation of flat panel flight displays. The pilot conducted a test flight the day prior to the accident flight with only minor discrepancies noted. There was no record of a preflight weather briefing associated with the accident flight. Radar track data showed the accident airplane on a southwest course at 8,600 feet mean sea level (msl). About 15 minutes prior to the accident, the airplane made a course adjustment to the west, before returning to a southwest course. During this time, the aircraft began a descent to 7,000 feet msl. The final radar data point was located about 1 mile southeast of the accident site. Witnesses reported hearing an airplane flying in a southwest direction. About 2 minutes later, they heard the sound of the engine increase, followed by a "big boom" and then nothing. The accident site was located in an open agricultural field. A postaccident examination of the wreckage did not reveal any anomalies consistent with a preimpact failure or malfunction. Weather data indicated the presence of an overcast cloud layer at 2,300 feet above ground level (agl), with additional cloud layer(s) between 4,000 feet msl and 8,500 feet msl, in the vicinity of the accident site.

Text from the NTSB. Open the NTSB docket for CEN11LA066 for the full record.