What happened
On 4 August 2005, a Bombardier DHC-8-400, registration G-JECE, was operating a passenger flight from Birmingham to Edinburgh when an oily odour was detected on the flight deck. Shortly after the aircraft began its descent, smoke began to accumulate in both the flight deck and the passenger cabin. The cabin crew reported that the forward toilet area was filled with white smoke, prompting the crew to don smoke masks.
Due to the rapid increase in smoke levels, the commander declared a 'MAYDAY' and diverted the aircraft to Leeds Bradford International Airport. During the descent, the flight crew focused on executing emergency checklists, which limited their ability to communicate with the cabin crew. The aircraft landed at approximately 0 and an emergency evacuation was subsequently carried out via the airstairs and exits. There were no injuries to the 4 crew members or 56 passengers on board.
The investigation
Investigators examined the No 2 engine and found that a one-inch piece of the Inner Compressor Support (ICS) ring had broken off due to fatigue cracking. This detached material caused an imbalance in the Low Pressure compressor rotor, which in turn damaged an oil seal. This failure allowed engine oil to leak into the gas path and enter the bleed air supply for the air conditioning units, creating the visible smoke and odour.
Technical analysis also revealed that the cabin crew faced significant communication hurdles. The use of smoke hoods made verbal communication difficult due to changes in volume and the noise of the wearer's own breathing. Furthermore, the high workload of the flight crew during the diversion delayed their response to cabin emergency calls, causing concern among the cabin crew.