What happened
On 22 May 2014, a BAE Systems Avro 146-RJ85, registration EI-RJH, departed Dublin Airport for London City Airport. Approximately five minutes into the flight, the flight crew noticed smoke and fumes permeating the cockpit. The cabin crew simultaneously reported similar conditions within the passenger cabin.
In response to the deteriorating air quality, the crew donned oxygen masks and smoke goggles while executing emergency checklists. The pilot declared a PAN alert to Air Traffic Control and initiated an immediate return to Dublin. During the approach, the crew utilized ram air ventilation to clear the cabin, and the smoke eventually dissipated. The aircraft landed safely on Runway 28 without zero injuries to the 48 passengers or 4 crew members, and no damage was sustained by the aircraft.
The investigation
Following the emergency landing, maintenance personnel inspected the aircraft's air conditioning packs. While no direct contamination was found in the packs themselves, a distinct odor remained present when the second air conditioning pack was operated using APU air.
Engine inspections revealed oil accumulation around the forward ecology drain of the No. 4 engine. The engine was subsequently removed and sent to a maintenance facility for a detailed examination. During the disassembly of the high-pressure turbine, investigators identified a leak within the diffuser. Specifically, a fractured plate near the oil inlet pipe to the No. 2 bearing housing had shifted, making contact with the inlet pipe. Pressure testing confirmed that the leak originated from this oil inlet pipe.
Findings
- The primary cause of the smoke and fumes was an oil leak from the oil supply pipe in the No. 4 engine.
- This leak allowed oil to contaminate the bleed air supply, which is utilized by the aircraft's air conditioning packs.
- The fractured plate in the diffuser area facilitated the leak by contacting the inlet pipe.
- The location of the oil supply pipe makes it impossible to perform routine visual or borescope inspections of the specific area where the failure occurred.