What aircraft was involved and where did it happen?

The accident on 2011-02-14 involved a aircraft, at Serious incident to an aircraft of type Boeing 777-300ER, SE.

What was the probable cause of the accident?

The investigation could not establish a definitive cause for the sulfurous and rubber-like odor reported in the cabin.

Unidentified Odor Leads to Diversion of Emirates Boeing 777

An Emirates Boeing 777-300ER diverted to Stockholm after cabin crew reported a strong smell of burning rubber and sulfur during a flight from Dubai to New York.

What happened

On 14 February 2011, an Emirates Boeing 777-300ER, registration A6-ECE, was operating a scheduled passenger service from Dubai International Airport to New York's John F. Kennedy International Airport. During the cruise phase of the flight, cabin crew members alerted the flight deck to a pungent odor in the aft section of the cabin, described as smelling like sulfur or burning rubber, with some noting a rotten egg scent.

Due to the uncertainty regarding the source of the smell and the potential for safety risks, the commander elected to divert the aircraft to Stockholm Arlanda Airport. The aircraft landed at its maximum landing weight without further incident. Following maintenance interventions at the destination, the aircraft continued its subsequent flight sectors.

On a subsequent flight, the odor reappeared shortly after the aircraft leveled off at 30,000 feet. To mitigate the issue, the flight crew consulted maintenance control and deactivated the right pack to isolate the ozone system. This action caused the smell to subside, allowing the flight to proceed normally.

The investigation

The investigation, conducted by the UAE General Civil Aviation Authority (GCAA) with assistance from the Swedish Accident Investigation Authority (SHK), focused on identifying the source of the chemical odor. Investigators examined several components of the Environmental Control System (ECS), including the heat exchanger and the condenser/reheater.

Laboratory analysis using Fourier Transform Infrared (FTIR) Spectroscopy was performed on the ozone converter. This analysis identified the presence of silicone, which was determined to be a common silicone oil used as an installation aid and not a source of the odor. Extensive inspections of the air conditioning components revealed no foreign contamination or mechanical defects that could account for the sulfur-like smell.

Findings

The aircraft was airworthy and maintained in accordance with all regulations.
The crew managed the situation effectively using established crew resource management (CRM) protocols.
The investigation was unable to determine the specific cause of the disturbing odor in the passenger cabin.
While the ozone converter was a suspected source because the odor diminished when the system was bypassed, no definitive cause was found within the unit itself.