Incident Overview
On 2 January 1996 at 1100 UTC, a Crossair SAAB 2000, registration HB-IZA, was on approach to Geneva Airport from Marseille during flight LX 731. While established on the ILS for runway 23, a cabin crew member detected a smell reminiscent of cigarette smoke and observed smoke emanating from a gap in the floor near the first row of forward seats. The flight crew was notified, and the commander, seated on the left, saw a small hole in the floor with a glowing ember emitting gray-white smoke. With the aircraft 1.5 nautical miles from the runway threshold, the commander decided to continue the landing. The copilot reported a smoke problem to the tower and requested fire services.
Sequence of Events
The lead flight attendant (F/A 1) informed her colleague via the public address system and discharged a Halon extinguisher onto the smoking area. Smoke spread quickly throughout the cabin. After landing, the crew vacated the runway via taxiway Charlie and initiated an evacuation through the main door. The commander shut down the engines and batteries. The copilot assisted the cabin crew in evacuating all 47 passengers and 4 crew members, which proceeded calmly as firefighters arrived. The crew left the aircraft as smoke and odor became intense. The hole in the floor measured approximately 5 cm in diameter. Firefighters boarded and removed the floor panel, stopping the smoke production. All passengers and crew were reported uninjured or slightly injured; some passengers suffered from smoke inhalation.
Findings
The aircraft was properly licensed and within weight and balance limits. The pilots held valid licenses and were not affected by health issues; duty and rest periods were respected. The smoke was caused by a heating mat installed between the carbon-fibre cabin floor and the rubber mat near the main door. This heating system, powered by 28 volts and protected by a 6.3-amp fuse, had been activated by the lead flight attendant in Vienna and remained on during the Vienna–Geneva–Marseille–Geneva route. Investigators determined that defective insulation of the heating mat allowed a leakage current of less than 6.3 amperes to flow into the carbon-fibre floor layers. The resistivity of the carbon fibres limited the current but caused localized heating to incandescence, which then charred the rubber mat and produced smoke. The exact cause of the insulation defect could not be determined.
Cause
The incident was caused by a short circuit in the cabin floor due to defective insulation of the heating system. Following the event, an Alert Airworthiness Directive was issued on 18 January 1996 by Swedish authorities, grounding the system until a permanent fix. The manufacturer later replaced the floor panel with insulating material lacking carbon fibres. Additionally, cabin crew received further training on heating system operation and emergency communication procedures.