Incident Overview
While cruising at 4,500 feet MSL on a dark night cross-country flight, a passenger seated in the right rear seat of the 4-place airplane complained to the pilot that her seat cushion was hot and she smelled something burning. The pilot subsequently noticed that his instrument lights had dimmed and his radios were intermittently cutting out. Within minutes, the leather seat cushion started to smoke, and the passengers attempted to control the in-flight fire with a blanket and some bottled water.
Emergency Landing
The pilot elected to make an emergency landing on an Interstate highway. He extended full flaps and touched down on the centerline of the northbound lane. He guided his three passengers out of the burning airplane onto the shoulder of the road.
Fire and Damage
The cabin of the airplane and all combustible material within the cabin were consumed by the fire.
Examination Findings
Examination of the wreckage revealed that the required 1/2-inch thick plywood plate, intended to be installed on the bottom of the right rear cushion to isolate the battery posts from making contact with the seat springs, was not installed. The one-time Airworthiness Directive (AD) and Service Bulletin requiring the installation of the plywood board had been complied with on February 17, 1982. The aircraft interior had been refurbished twice since the application of the AD. The airplane was not equipped with a portable fire extinguisher.