Sequence of Events
The pilot was descending the airplane from 23,000 feet in preparation for an instrument approach. All communications proceeded normally until the pilot acknowledged an instruction to contact approach control, after which radio contact was lost. Radar contact ceased at 11,300 feet due to difficulties in radar signal reception. The loss of contact occurred almost directly over the eventual impact site, which was situated on the eastern side of a small valley.
Witness Observations
Witnesses located on the western side of the valley reported seeing the airplane flying near them at treetop level, traveling eastbound and clear of clouds. At approximately the same time, on the eastern side of the valley—where the airplane would impact trees and then terrain—there was heavy rain.
Pilot Information
The commercial pilot held approximately 1,850 total flight hours and had completed a 'Wings III' flight proficiency program as well as an instrument proficiency program approximately two months before the accident. The pilot's father, two uncles, and a male cousin had previously suffered fatal heart attacks.
Aircraft Information
The airplane had been on a continuous maintenance program. At the accident site, all of the airplane's control surfaces were accounted for, and the engines and propellers displayed signatures consistent with being under power at the moment of impact.
Investigation Findings
There were insufficient remains to conduct an autopsy or toxicological testing on the pilot.
Probable Cause
The official probable cause was loss of control of the airplane due to pilot incapacitation following a heart attack.