The Transportation Safety Board of Canada (TSB) has found that an error in an engine oil feed tube seal led to a turbine rotor failure and subsequent fire during Bombardier’s ground tests at the Montréal International (Mirabel) Airport in Quebec.

On 29 May 2014, sudden power loss was experienced in the left engine during testing, which was followed by rotor failure. The crew immediately shut it down, then declared an emergency after finding smoke and fire.

Although personnel on board were evacuated safely, the engine and aircraft were damaged substantially.

"Although personnel on board were evacuated safely, the engine and aircraft were damaged substantially."

A probe found that as the engine was immediately shut down following high-power operation, it did not leave sufficient time for internal temperatures to reduce, which led to seal failure and allowed engine oil to mix with the turbine rotor’s cooling air flow.

As a result, fire broke causing the entire turbine rotor stage to fail. This led to major damage to the engine, nacelle, and wing.

The probe also found that while Bombardier’s ground personnel put out the fire successfully in this instance, the engine’s extinguishing system had not been activated. This means when the craft is in use, there is an increased risk of spread in the event of a fire, if the nacelle’s fire bottles are not deployed or if ground-fire extinguishers are not located for quick access.

Bombardier had grounded the C Series test aircraft fleet until the cause was clearly established.