Date: 201408
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Flight conditions: IMC
Light: Night
Aircraft: A330
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Climb; Cruise
Airspace: Class A ZZZ
ATC / advisory: Center ZZZ
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Not Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP)
Human factors: Situational Awareness; Distraction; Physiological - Other; Time Pressure; Troubleshooting
Anomaly: Flight Deck / Cabin / Aircraft Event Illness / Injury; Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor
Detector: Person Flight Crew; Person Flight Attendant; Person Passenger
When detected: In-flight
Result: Aircraft Equipment Problem Dissipated; Flight Crew Landed in Emergency Condition; Flight Crew Returned To Departure Airport; Flight Crew Took Evasive Action; General Flight Cancelled / Delayed; General Maintenance Action; General Declared Emergency
Contributing factors: Aircraft; Human Factors; Weather
Primary problem: Weather

Narrative: Climbing to FL370; about 50 minutes into flight; the First Officer and I noticed a hot; electrical smell.  We queried the flight attendants and they also smelled it.  No smoke was visible and none reported. We had the engine anti-ice on and saw a lot of St. Elmo's fire on our windscreens. The Relief Pilot (IRO) came forward from the crew-rest seat as he also noticed the smell.  The flight attendants and IRO walked through the cabin to try to localize the source; especially the galleys; with no results.  The First Officer and I were on oxygen as a precaution.  We leveled off clear of clouds and static and turned off the engine anti-ice.  The smell seemed to dissipate some.  The flight attendants reported passengers expressing concern with some complaining of minor eye irritation.  As pilot monitoring; I contacted Dispatch and Maintenance Control.  Maintenance suggested some steps to localize the source when the Lead Flight Attendant reported that the one Flight Attendant was feeling poorly and going on oxygen.  I then told Dispatch we were diverting and they requested we return to the departure airport.  I did not consider that it was necessary to divert to the nearest airport as there was no smoke and the smell seemed to be diminishing.  We turned toward the departure airport and in the descent through clouds; the smell seemed to increase again so we declared an emergency with ATC to receive priority handling and high speed descent.  The smell again seemed to decrease.  I assumed pilot flying duties and made a normal landing in VFR weather.  As requested; paramedics met us at the gate.  We asked passengers to remain seated so those wanting assistance (3 flight attendants and 2 passengers) could be seen to.  Four flight attendants went with the paramedics for tests/observation.  I filled out the odor report form; made a lengthy entry in the FDML and spoke to a Maintenance Supervisor.  The First Officer; IRO and I felt no ill effects other than possible mild eye irritation. Electrical smell from unknown source.

Callback: The reporter stated that in the climb and descent when the odor was detected both the engine anti-ice was ON and flight was in very heavy St. Elmo's fire. During the short cruise flight period the odor dissipated but again returned as the flight descended through the weather with engine anti-ice ON in St Elmo's conditions. Maintenance did fly a test flight but found nothing. They did not fly the aircraft in weather conditions similar to those in which the anomaly occurred. The Reporter stated that the St Elmo's fire was the most spectacular he has experienced in his 30 plus years flying commercial aircraft.



Synopsis: An A330 in heavy St Elmo's fire with engine anti-ice on developed a strong electrical odor which crew and passengers reacted to; so the flight returned to the departure airport. Maintenance discovered no anomalies and suspected a weather related phenomenon.