Incident Summary
On December 20th, 2023, a SAS Scandinavian Airlines Airbus A321-200N, registration SE-DMS, operating positioning flight SK-9228 from Copenhagen (EKCH) to Oslo (ENGM), experienced an electrical odour during climb. The flight, with only two crew members on board, declared a Mayday and returned safely to Copenhagen Airport for inspection.
Sequence of Events
1. Pre-Flight Observations
• Prior to departure, the flight crew observed an unexpected fuel distribution issue. The ACT (Additional Center Tank) still contained fuel, which the crew expected to be empty.
• The Electronic Centralized Aircraft Monitor (ECAM) displayed a fuel message: “ACT XFR FAULT”.
• The crew followed standard procedures to resolve the fault by manually transferring fuel to the center tank.
2. In-Flight Events
• During climb-out, at around 5,000 feet, the ECAM fuel message reappeared. The crew repeated the associated procedure to clear the fault.
• Passing FL250, the first officer noticed an electrical burning odour and alerted the commander.
• The commander confirmed the smell and decided to don oxygen masks and immediately return to Copenhagen. A Mayday was declared.
3. Emergency Procedures
• Sweden Control directed the aircraft to descend to FL180 and route inbound to the LAMOX waypoint for an approach to runway 22L.
• The commander consulted the Quick Reference Handbook (QRH) for “Smoke/Fumes/AVNCS smoke” and the first officer squawked emergency code 7700.
• The flight landed safely on runway 22L, where emergency services awaited.
4. Post-Landing Inspection
• The fire brigade conducted external checks and found no visible smoke or fire.
• Upon opening the avionics compartment under the cockpit, a strong electrical burning odour was detected but no fire or smoke was observed.
Onsite Examination Findings
• Maintenance inspected the avionics compartment and identified damage in the contactor box 107VU. Specifically:
• A GFI relay (124QH) had a burnt hole in its plastic housing and black soot deposits.
• The adjacent relay (17QA) showed minor soot deposits but no damage.
• The aircraft wiring and mating installation remained intact.
• No circuit breakers were found open.
Interim Safety Observations
1. The electrical odour was isolated to the cockpit and the avionics compartment.
2. The malfunctioning GFI relay (124QH) is the likely source of the burning smell.
3. The flight crew followed proper emergency protocols, including declaring a Mayday and donning oxygen masks.
Preliminary Conclusion
The serious incident resulted from a burnt-out GFI relay in the avionics compartment, causing an electrical odour in the cockpit. There was no evidence of fire or smoke, and the crew’s quick decision to return ensured safety.
Denmark’s Havarikommissionen (HCL) is conducting a full investigation into the incident to determine any underlying causes and safety recommendations.
Note: This article is based on all available facts at the time of writing.
