What happened
On March 6, 2001, a SAAB SF 340A, registration SE-KUT, was operating a scheduled flight from Sundsvall/Härnösand to Luleå/Kallax. Shortly after climbing to a flight level of 210, the flight crew and a cabin attendant detected a pungent odor resembling burning plastic. Although no visible smoke or fire was present, the crew treated the situation as a serious emergency.
The pilots donned oxygen masks and notified Air Traffic Control of smoke in the cabin, requesting an immediate descent and diversion to the nearest airport. The aircraft was vectored for an approach to Umeå airport. During the descent, the co-pilot attempted to follow the emergency checklist for electrical smoke or fire; however, he found the procedures difficult to apply to the specific situation and eventually transitioned to the normal checklist to avoid shutting down essential systems needed for the approach.
The investigation
An investigation by the Swedish Accident Investigation Authority (SHK) focused on the source of the odor and the crew's response. Technical inspections of the aircraft's electrical systems were conducted by the airline and the manufacturer. While initial troubleshooting did not immediately reveal the source, the investigation eventually localized the smell to a specific control unit, the Flat Panel Control Display Unit (FPCDU).
Findings
- The flight crew acted correctly by donning oxygen masks and declaring an emergency.
- The aircraft was airworthy and the pilots were properly qualified.
- The incident was caused by overheated electronics within the FPCDU control unit.
- A type-related fault in the FPCDU was identified as the source of the burning odor.
- The manufacturer, Universal Avionics, subsequently issued service bulletins to address this component failure risk through retrofits and enhanced functional testing.