What happened
On December 3, 2017, a Nordic Regional Airlines flight from Helsinki-Vantaa to Gothenburg, operated by Finnair, was diverted to Turku Airport following a technical malfunction. The aircraft, an Embraer 190-100LR, was carrying 100 passengers and four crew members. Shortly after takeoff, the flight crew noticed fluctuations in the pressurization system and elected to fly at a lower altitude as a precaution.
During the flight, the crew detected a burning smell, which intensified until the captain declared an emergency due to smoke in the aircraft. While the crew was maneuvering for landing, smoke also became visible in the cockpit, prompting the pilots to don oxygen masks. The aircraft landed on runway 26 at Turku at 16:54 local time.
After exiting the runway, the crew observed that the smoke in the cabin had increased. The captain initiated an emergency evacuation on taxiway E. Passengers utilized emergency exits and slides to egress. Some passengers initially attempted to exit via the wing exits but were advised by rescue personnel to return to the aircraft and use the slides to avoid injury from jumping from the wing height.
The investigation
The investigation examined the sequence of events, the technical failure of the aircraft systems, and the effectiveness of the emergency response. Investigators analyzed the aircraft's air conditioning unit, specifically the Air Cycle Machine (ACM), and conducted a technical examination of the component at a laboratory in the Netherlands. The investigation also reviewed the coordination between Air Traffic Control (ATC), the emergency center, and rescue services, as well as the functionality of the smoke hoods (PBE) used by the crew.
Findings
- The primary cause of the smoke was a failure within the air conditioning unit's Air Cycle Machine (ACM).
- A crew member attempted to use a smoke hood (PBE), but the protective pouch failed to open.
- There were discrepancies in how the emergency was classified; while the captain declared an emergency, the ATC notification was processed by the emergency center as an "aviation accident hazard" rather than an "aviation accident," which influenced the level of the emergency response.
- Differences in terminology and instructions between ATC alert procedures and emergency center response protocols created ambiguities in the coordination of rescue operations.