NTSB Identification: SEA98FA105.
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Accident occurred Thursday, June 18, 1998 in LINCOLN, MT
Probable Cause Approval Date: 01/11/2000
Aircraft: Cessna 340, registration: N88JH
Injuries: 1 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.

During preflight weather briefing, the pilot was briefed to expect rain showers and thunderstorms up to Level 6 (extreme) intensity along his route of flight. The pilot, whose aircraft was equipped with radar and Stormscope equipment, filed an instrument flight rules (IFR) flight plan and departed under IFR. Upon radar contact, ATC cleared the pilot direct to his destination. 21 minutes later, while flying on the direct (northwesterly) track to the destination, the aircraft entered a Level 4 thunderstorm cell. The pilot told air traffic control (ATC), '...[I] hit a pretty heavy cell here [I've] got lightning all around and picking up some hard ice.' The crew of another aircraft deviating to the north of the storm suggested the aircraft turn north to exit the weather. ATC relayed this suggestion, and the pilot replied he was turning to the north. The aircraft then entered a right turn; radar contact was lost after approximately 90 degrees of turn. 6 seconds after the time at the last radar position, the pilot radioed, '...[I'm] in a tremendous downdraft [I'm] losing altitude six thousand'. This was the last transmission received from the accident aircraft. A search for the aircraft was initiated; the aircraft wreckage was found approximately 11 1/2 hours later, approximately 1 1/2 miles south of the last radar position. Logbooks recovered from the wreckage indicated the pilot was not current for IFR flight.

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

The pilot's improper or inadequate use of the aircraft's weather avoidance equipment, resulting in penetration of a Level 4 thunderstorm and subsequent loss of aircraft control from which the pilot did not recover. Factors included a thunderstorm and the pilot's lack of instrument currency.

Full narrative available

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