The Transportation Safety Board has found that turbine oil leaking into compressor airstream and the cabin pressurization system caused smoke to fill the cabin of a Nanaimo-bound WestJet flight in March.
The leak was caused by a steel spring in the carbon seal that had disintegrated.
According to the TSB report, the Bombardier DHC-8-402 had left Vancouver International Aiport at 12:19 p.m. on March 20th with 56 passengers and four crew on-board.
As the plane neared Nanaimo about 11 minutes later, the flight crew noticed smoke in the cockpit, a cabin attendant then alerted the crew to smoke in the cabin as well.
As the plane continued towards Nanaimo, oxygen masks were deployed and an emergency was declared with Air Traffic Services.
It landed at 12:35 with ground emergency vehicles waiting, some smoke could be seen but there was no sign of fire.
The passengers and cabin crew evacuated the aircraft in 62 seconds, the pilots left soon after, and there were no injuries.
The plane’s two Pratt & Whitney Canada PW150A turboprop engines, installed new during initial construction in 2016, were sent to Montreal for inspection.
“The inspection revealed that a steel spring (wave washer) in the 2.5 bearing carbon seal had disintegrated, compromising the efficiency of the carbon seal,” the TSB report revealed.
Pratt & Whitney Canada was aware of the problem following previous failures and had issued a Service Bulletin in October 2016 and again in January 2018.
The latter called for the seal to be replaced, but recommended that the work be done when engines were disassembled for repair. The engine in this case had yet to be overhauled so the work had not yet been done.
Pratt & Whitney Canada developed new technology to help detect impending seal failures and the TSB report says that, since the incident, WestJet has implemented it on all its Q400 fleet.
The TSB report praises the work of the WestJet crew saying they “responded appropriately and rapidly during the occurrence and were able to land and evacuate the aircraft with no injuries and no damage.”
It also says Air Traffic Services and airport personnel responded in a timely manner, which contributed to the positive outcome.