NTSB Identification: SEA96FA024.
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Accident occurred Saturday, November 25, 1995 in BOZEMAN, MT
Probable Cause Approval Date: 11/11/1996
Aircraft: Beech C24R, registration: N3729T
Injuries: 2 Fatal.

NTSB investigators either traveled in support of this investigation or conducted a significant amount of investigative work without any travel, and used data obtained from various sources to prepare this aircraft accident report.

The flight was on an instrument flight rules (IFR) flight plan and had been cleared by air traffic control (ATC) for an instrument landing system (ILS) approach. The aircraft owner, along with the flight instructor, who completed the pilot's instrument training as well as his checkout in the accident aircraft, stated that they had instructed the pilot not to fly the accident aircraft in IFR conditions. The airplane was flown at an altitude of 13,000 feet for 32 minutes before commencing the approach, and it was not equipped with supplemental oxygen or cabin pressurization. The pilot failed to follow the specified ground track for the approach, and the airplane impacted mountainous terrain about 13-1/2 nautical miles north-northeast of the airport in heavy snow conditions. The accident site was approximately 15-1/2 nautical miles beyond the point where a turn onto the localizer was specified on the approach procedure. The airport did not have a control tower or approach control radar, and the airplane was not in radar contact with ATC at the time of the accident. A hunter near the accident site saw an airplane fly over his position at low altitude in heavy snowfall. He heard a loud metallic 'clank' about 20 to 30 seconds after the airplane disappeared from his view. Also, he noted the time on his watch, which corresponded to the estimated time of the accident.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

failure of the pilot to follow the specified approach track (proper IFR procedure), and his associated failure to maintain altitude or clearance from mountainous terrain. Factors relating to the accident were: the pilot's failure to abide by the aircraft owner's (dispatch) procedures, heavy snowfall, mountainous terrain, and possible pilot impairment from altitude hypoxia.

Full narrative available

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