What happened
On March 22, 1998, a scheduled SAS flight from Stockholm/Arlanda to Kiruna was interrupted when cabin crew reported a burning smell originating from the forward galley. The captain confirmed the odor, noting it resembled burning electrical components, and observed hot air escaping from a cabin wall vent.
As the aircraft approached Kiruna, the crew transitioned to emergency power, which necessitated disengaging the engine-driven generators. This action also deactivated the aircraft's automatic braking system (ABS) and Anti-Skid System. During the landing on runway 03, the first officer applied the brakes carefully; however, without the anti-skid functionality, the four main wheels locked, causing three of the tires to deflate. Following the touchdown, smoke enveloped the aircraft, prompting the captain to order an emergency evacuation. During the process, one emergency evacuation slide failed to deploy automatically and required manual activation.
The investigation
The Swedish Board of Accident Investigation (SHK) examined the electrical systems, the braking performance, and the emergency procedures used during the incident. The technical investigation focused on the galley' and the water boiler control unit. Investigators also reviewed the cockpit's use of emergency checklists and the functionality of the aircraft's evacuation equipment.
Findings
- The primary cause of the odor was an overheating integrated circuit (IC) and its retainer within the water boiler control unit.
- This overheating was likely triggered by the simultaneous installation of an incorrect circuit breaker (a 2A fast type instead of the required 1A slow type) and an incorrect LED bulb within the same electrical circuit.
- The loss of the Anti-Skid System during the landing directly led to the wheel lock-up and subsequent tire punctures.
- One emergency slide failed to deploy automatically due to an incorrectly installed firing lanyard.
- The existing emergency checklists for "smoke or fumes" were found to be insufficiently user-oriented for high-stress situations, and the instructions for landing without anti-skid assistance were deemed incomplete.
Safety action
SHK issued recommendations to the Swedish Civil Aviation Administration to ensure that emergency checklists for large aircraft provide comprehensive guidance for landings without anti-skid systems and are redesigned to be more intuitive for pilots managing smoke or fire odors.