What happened
On June 5, 2000, a McDonnell Douglas DC-9-83, registration HB-IUM, operated by Crossair AG, was taxiing at Geneva Airport when cabin crew detected a strong electrical burning odor. The crew immediately notified the flight deck, and the captain requested to return to the boarding gate. After waiting briefly behind another aircraft to perform a 180-degree turn on the runway 23 holding point, the aircraft proceeded to gate 63.
During the taxi, cabin crew confirmed the presence of a strong odor and light smoke in the forward galley area. The captain notified the passengers via the aircraft's announcement system and summoned the airport fire service. Once the aircraft arrived at the gate, passengers were safely evacuated with their hand luggage. Firefighters subsequently inspected the cabin using infrared equipment but found no active fire.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) conducted an inquiry, which included the examination of the flight data recorder and cockpit voice recorder. Investigators focused on the electrical components near the galley area. The investigation revealed that the aircraft had recently undergone significant maintenance, including a D-check and C-3 check in December 1999, which involved various modifications and the relocation of some power cables in zone 51.
Investigators removed and analyzed the terminal board and associated cable ends. While the connection between the cable and the contact showed no thermal damage and remained secure, the terminal board itself showed significant signs of overheating. Analysis of the protective insulation and wire fragments confirmed that temperatures had risen significantly.
Findings
- The investigation identified the source of the smoke and odor as a localized overheating event near terminal board S3-25.
- The primary cause was increased electrical resistance resulting from insufficient pressure between contact number 7 and terminal S3-25.
- This resistance caused temperatures to escalate to an estimated range between 800°C and 1000°C.
- The damage to the protective sheath and nearby cable heads was determined to be secondary to the heat generated by the high-resistance connection.
- No electrical arcing was observed during the event.