What happened
On a flight from Sydney, Nova Scotia, to Halifax, Nova Scotia, an Air Canada Regional DHC-8-100 carrying 35 passengers and three crew members experienced two separate engine flame-outs. During the initial climb at approximately 6,000 feet, the first officer noticed ice within the right engine's air inlet duct. Shortly after, the right engine (Pratt & Whitney 120A) suffered a flame-out, though it recovered quickly once the ignition remained active. Two minutes later, the right engine experienced a second flame-out and subsequent recovery.
As the aircraft reached its cruise altitude of 14,000 feet, the left engine underwent a similar sequence of flame-out and recovery. Following these events, the crew completed necessary checklists, and the aircraft arrived at its destination without further issues.
The investigation
The investigation focused on how ice accumulated in the engine air inlet ducts. Investigators considered two primary scenarios. The first suggested that water had accumulated in the ducts while the aircraft was parked in Sydney. Because the aircraft had been stored in an unheated hangar where temperatures were slightly above freezing, any existing ice likely melted. However, because several drain holes in the right engine inlet duct were blocked, this water remained trapped. When the aircraft was moved to the ramp and exposed to freezing temperatures, this trapped water froze into a solid sheet.
An alternative scenario proposed that the ducts were clear during engine start, but ice formed within the ducts during flight. While the crew observed ice in the ducts, they also noted that the ice disappeared following the flame-outs, which could support either theory. The investigation also noted that the aircraft had been positioned on the ramp in blowing snow and freezing temperatures prior to departure.
Findings
- The engine flame-outs were caused by ice in the engine air inlet ducts lifting as a solid sheet, which interrupted the airflow required for engine operation.
- Three of the four drain holes in the right engine inlet duct were completely blocked, and the fourth was partially blocked, creating a risk of water pooling and freezing.
- It could not be determined with certainty whether the ice formed from pre-existing water in the ducts or through accumulation during flight.