Piper PA-32R-301T N4175A accident near Groveland, California

Probable cause

The pilot's continued flight into night instrument meteorological conditions during the landing approach, which resulted in an in-flight loss of aircraft control due to spatial disorientation.

NTSB analysis

The instrument-rated pilot departed at night without obtaining a weather briefing or filing an instrument flight plan. Radar track data revealed no deviations of heading or altitude for the en route segment, indicative of consistent autopilot usage. For a portion of the flight, the pilot was in communication with air traffic control (ATC) and was receiving flight following. As he approached the airport he reported to ATC that the airport was not in sight and that he would return if it was covered in a fog layer. The radar data indicated that the airplane continued to overfly the runway and begin a series of rapid altitude and heading changes. Multiple witnesses reported hearing an airplane flying with high engine speeds in the vicinity of the airport subsequent to its collision with the ground.

The wreckage path, instrument indications, and damage to surrounding trees were indicative of a high-speed, 80-degree-right-bank, and 45-degree-nose-down collision with terrain. The pilot, having flown only two instrument approaches in the preceding 6 months, was not current to fly an instrument approach. He had limited experience landing at the accident airport at night and had never performed an instrument approach into the airport in actual instrument meteorological conditions (IMC). The airplane was equipped with an autopilot and instruments suitable for flight in IMC. Impact damage and postaccident fire prevented a determination of the operational status of these systems. Examination of the remaining wreckage revealed no evidence of premishap or mechanical malfunctions of the engine and airframe.

An hour prior to the accident, another pilot reported performing a missed approach at the arrival airport due to limited visibility, followed by a diversion to an alternate airport. Witnesses and en route weather reporting facilities reported low clouds, fog, and precipitation in the vicinity of the airport. The weather conditions and operation at night were conducive to the onset of pilot spatial disorientation as indicated by the airplane's multiple rapid descents, ascents, and heading changes after the airplane passed over the airport.

Text from the NTSB. Open the NTSB docket for WPR10FA142 for the full record.