Incident
On the day of the occurrence, at 0739:32 central daylight time, the pilot of a Beech 58 reported smoke emanating from the aircraft while at an altitude of 8,100 feet mean sea level (msl). The last radio transmission from the pilot was received at 0743:01. By 0743:14, the aircraft's altitude had descended to 3,000 feet msl.
Post-accident Findings
Examination of the aircraft revealed a resistor attached to the right cabin side wall. This resistor was similar in size, shape, and color to two resistors used in the door seal inflation system. The area around the resistor showed that a black material attached to the interior side wall was absent, and there was bubbling of both the black material and the exterior paint. Additionally, black material similar to that on the side wall was found on the bottom of the resistor.
The Beech 58 Pilot's Operating Manual, under the section for electrical smoke or fire, directs that the Battery and Alternator Switches be selected to the OFF position. The installation instructions for the resistor state that it should be mounted to metal structure for heat sink.
Simulator Evaluation
An emergency descent from an altitude of 8,000 feet msl was simulated in a flight training simulator. The descent rate achieved was approximately 6,200 feet per minute. A simulated off-airport landing was also completed in approximately 2 minutes and 15 seconds.
Airworthiness Directive
Airworthiness Directive 98-21-21 has been issued, requiring the deactivation or removal of all provisions of the inflatable door seal installation.