NTSB Identification: CHI98FA349.
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Accident occurred Wednesday, September 16, 1998 in OAKDALE, WI
Probable Cause Approval Date: 11/17/1999
Aircraft: Beech 58, registration: N4574Q
Injuries: 3 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.

At 8,100 feet mean sea level (msl), the pilot reported smoke coming from the aircraft at 0739:32 central daylight time. At 0743:14, the aircraft altitude was 3,000 feet msl. The last received transmission by the pilot was at 0743:01. The Beech 58 Pilot's operating manual, states, under ELECTRICAL SMOKE OR FIRE, that the Battery and Alternator Switches are to be selected in the OFF position. A resistor, similar in size, shape and color to two of the resistors in the door seal inflation system was found attached to the right cabin side wall. The area surrounding the resistor revealed that a black material attached to the interior side wall was absent. There was bubbling of the black material and outside paint. Black material similar to the material on the side wall was also present on the bottom of the resistor. Installation instructions referencing the resistor, state, 'mount to metal structure for heat sink'. An emergency descent from an altitude of 8,000 feet msl was performed in a flight training simulator and a descent rate of approximately 6,200 feet per minute was obtained. A simulated off airport landing, in a simulator, was completed in approximately 02:15 minutes. Airworthiness Directive 98-21-21 has been issued for the deactivating or the removing of all provisions of the inflatable door seal installation.

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

The installation of the door seal inflation system by company personnel. An additional cause was the emergency procedures not followed by the pilot-in-command. A contributing factor was the trees.

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