What happened
On July 11, 2023, an Airbus A330-343, registration HB-JHL, operating a flight from Zurich to Newark, experienced an unusual odor during cruise flight over the English Channel. The incident began during the initial climb, when the flight crew noticed a smell resembling hot bitumen in the cockpit. As the aircraft reached flight level 340, the odor intensified in the cabin, described by crew members as smelling like "dirty socks" or a "damp cellar."
In response to the unidentified odor, the cockpit crew donned oxygen masks. Several cabin crew members attempted to use Protective Breathing Equipment (PBE) to manage the situation. However, the crew encountered significant difficulties with the equipment, including struggles with unpacking, unfolding, and activating the hoods. There were also technical defects identified in several PBE units, rendering them partially or entirely non-functional.
The investigation
An investigation by the Swiss Transportation Safety Investigation Board (SUST) examined radar records, crew statements, and data from the aircraft manufacturer and the PBE manufacturer. The inquiry focused on the technical performance of the Collins Aerospace PBE (part number 119003-21) and the effectiveness of crew training. Testing revealed that the PBE units exhibited technical deficiencies that could bypass standard maintenance inspections. Furthermore, the investigation found that the training provided to crew members relied on simplified training replicas that did not accurately represent the complexities of the functional units, such as the difficulty of removing them from vacuum packaging or the physical challenges of breathing and communicating while wearing the active equipment.