What happened
On 16 October 2017, an Embraer SA, ERJ 190-200 LR, registration G-FBEM, was performing a scheduled commercial flight from Cardiff to Dublin. While descending through 7,000 feet, the flight crew detected a sulfurous burning odor. The smell was confirmed by cabin crew members in the rear of the aircraft.
In response to the odor, the pilots donned their oxygen masks. This action introduced several secondary complications: the co-pilot's microphone experienced intermittent failures, making communication with Air Traffic Control (ATC) and between the pilots difficult. Additionally, the smoke goggles on the masks provided restricted visibility due to surface scratches and a layer of obscuring residue. Despite these challenges, the crew declared a 'PAN-PAN' urgency state. To manage the high workload and visibility issues, the crew utilized hand signals to complete landing checklists. The aircraft landed safely at Dublin Airport, where emergency services met the plane. There were no injuries to the 75 passengers or 5 crew members.
The investigation
The AAIU investigation established that the burning smell was not caused by an onboard fire, but rather by smoke from wildfires in Spain and Portugal that had been drawn into the atmosphere over Ireland. The investigation also examined the functionality of the crew's oxygen equipment. While the masks were inspected according to standard maintenance intervals, the investigation found that the lenses were obscured by 'blooming' and scratches that were not detectable while the masks were stowed in their containers.
Findings
- The primary cause of the incident was the smell of smoke in the cabin, which forced the crew to use oxygen masks that subsequently impaired their ability to communicate and see.
- Atmospheric smoke from Iberian wildfires contributed to the presence of the odor.
- The co-pilot's mask microphone suffered an intermittent failure during the approach.
- The oxygen mask lenses were obscured by a layer of residue and scratches, which could not be identified during routine pre-flight checks because the masks were not physically worn during those inspections.
Safety action
- The investigation recommended that the Federal Aviation Administration (FAA) review regulations regarding the pre-flight inspection of stowed oxygen equipment to ensure visibility issues are detectable.
- The aircraft manufacturer has since introduced production changes to reduce lens obscuration and issued guidance on cleaning masks.