What happened
On 18 June 1998, a Propair 420 Fairchild-Swearingen Metro II (registration C-GQAL) departed from Dorval, Quebec, bound for Peterborough, Ontario. During the initial takeoff roll on Runway 24L, the aircraft exhibited a tendency to veer left, necessitating significant right rudder input to maintain alignment. Shortly after climbing to 16,000 feet, the crew reported a drop in hydraulic pressure and requested an immediate return to Dorval.
During the subsequent descent and turn, the crew experienced several escalating issues. An engine overheat light illuminated on the left wing, which briefly extinguished before a visible fire developed in the left engine nacelle. The crew shut down the left engine and diverted toward Mirabel airport. As the aircraft approached for landing, the crew reported flames exiting the engine nozzle and noted increasing difficulty controlling the aircraft's roll.
During the final approach to Runway 24L, the crew attempted to extend the landing gear, but only two indicators illuminated. As the aircraft neared the runway threshold, the left wing suffered a structural failure. The Fairchild-Swearingen Metro II rolled more than 90 degrees, inverted, and impacted the runway. The impact triggered a large fire that caused the aircraft to slide 2500 feet. There were 3 fatalities among the occupants.
Findings
Investigations determined that the left brakes had been dragging since takeoff due to an unidentified pressure locking issue. This dragging caused the brake components to overheat, leading to a hydraulic fluid leak. The leaking fluid ignited upon contact with the hot brakes, creating an intense fire in the left nacelle that eventually compromised the main hydraulic system.
The fire weakened the structural integrity of the left wing, causing it to fail during the landing approach. Contributing factors included the crew's failure to recognize that the takeoff deviation was caused by brake overheating and a lack of specific information in the aircraft manual regarding brake overheat symptoms or preventative measures. Additionally, the mixing of two different hydraulic fluids lowered the fluid's ignition temperature, making it more susceptible to catching fire.