Canadian investigators have yet to determine the origin of an apparent engine fire which prompted a Bombardier Q400 to return to Saskatoon shortly after departure.

But the Transportation Safety Board of Canada has pointed out that the Jazz aircraft had been de-iced prior to its departure.

It had taken off on a service to Calgary on 17 February when a passenger and cabin crew observed flames from an aft pipe on the left-hand Pratt & Whitney Canada PW150A engine.

The cabin crew notified the pilots, who had not received any fire warnings or indications, and they did not shut the engine down.

But the crew opted to return to Saskatoon and landed on runway 27 before ordering a "rapid deplanement" of the turboprop, says a TSB bulletin.

Firefighters checked the aircraft with thermal cameras but determined there was neither a fire nor excessive heat in the engines.

"The operator's maintenance subsequently inspected the aircraft and found no signs of a defect or source for the flames," adds the bulletin.

But the aircraft had been de-iced, to remove accumulated ice from a previous flight, before departure.

While investigators have not specifically indicated a causal link, pooled de-icing fluid has previously been linked to fires and damage to engines and auxiliary power units.

Source: Cirium Dashboard