On April 17, 2003, a Cessna 320D (registration N4178T) was involved in an aviation accident near Mazama, WA. Investigators recorded the probable cause as: The pilot's failure to maintain clearance from terrain while maneuvering. Mountainous terrain, trees and mountain obscuration were factors. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
After four months, the wreckage of a missing twin-engine aircraft was discovered by a helicopter pilot fighting fires. The plane crashed into mountainous terrain in low cloud conditions, with no mechanical failure found.
Discovery
The aircraft had been missing for four months when its wreckage was spotted by a helicopter pilot engaged in firefighting operations. The wreckage was located on the east wall of a north-south running valley at the 5,000-foot level.
Investigation Findings
On-site documentation indicated that the aircraft was traveling in a northerly direction when it collided with several trees before impacting the steep mountainous terrain. No evidence of a mechanical failure or malfunction was found. At the time of the accident, low clouds and mountain obscuration were present in the area.
Flight Details
Two pilots flying in the area north of the departure airport had observed a twin-engine aircraft flying in a northerly direction between 200 and 500 feet above ground level. Data extracted from the onboard GPS unit indicated that the destination may have been an airport in Canada. The last recorded coordinates and altitude matched the accident site location and elevation. The last recorded speed was 197 knots. No flight plan had been filed, nor was there evidence of a weather briefing from flight services. Family members were unable to verify the purpose of the flight or its destination.