What happened
On 15 April 2000, a Finnair McDonnell Douglas MD 83, registration OH-LPH, was performing a scheduled commercial flight when the crew reported smoke and an electrical odor in the cabin. The incident occurred during the initial climb and turn toward Zurich while the aircraft was departing from Zurich Airport. The flight crew immediately decided to return to the airport, performing a successful landing on runway 16. There were no injuries to the 66 occupants on board, and all passengers disembarked safely.
The investigation
The Swiss Federal Aircraft Accident Investigation Bureau (SUST) conducted a technical investigation in coordination with SRTechnics and Finnair maintenance staff. The investigation involved the analysis of the Cockpit Voice Recorder and a detailed examination of the aircraft's electrical components. Investigators focused on the area above the hat rack in row 18, where the smoke originated. Upon opening the ceiling panel and the access door to the sidewall light ballast, investigators located a burned connector.
Findings
Technical examination of the removed connector revealed that while the external housing showed no signs of external heat damage, the internal components were significantly impacted. Specifically, a melted pearl of metal was found at contact "A" within the socket part of the connector, and the forward part of pin "A" was missing. The remaining copper on the pin exhibited severe blistering, which is a characteristic sign of high temperatures typically generated by an electric arc.
Safety action
Investigators determined that the incident was caused by increased electrical resistance at the contact point between the aircraft wiring and the specific interconnect cable (P/N C773-10-450) used for the ballast. This rise in resistance led to a temperature spike, resulting in the observed smoke and electrical odor.