What happened
On the morning of June 18, 1998, a Fairchild-Swearingen Metro II, registration C-GQAL, departed Dorval / Montréal International Airport for Peterborough, Ontario. Shortly after takeoff, the crew reported a drop in hydraulic pressure and requested to return to Dorval. During the return flight, the crew observed an engine fire in the left engine and subsequently shut it down.
As the aircraft prepared for an emergency landing at Mirabel / Montréal International Airport, the crew reported that flames were visible from the engine nozzle. During the final approach to Runway 2 and 4L, the crew noted that the fire had re-ignited. Upon extending the landing gear, the left wing suffered a structural failure, breaking upwards. The aircraft rotated violently, inverted, and struck the runway, where it caught fire. All 11 occupants, including two pilots and nine passengers, were killed.
The investigation
Investigators examined the aircraft's engines, propellers, and landing gear components. The right engine showed evidence of normal operation, while the left engine showed no signs of developing power. Examination of the left landing gear revealed that it had separated from the aircraft during the breakup and showed significant signs of overheating.
Technical analysis of the brake system focused on the possibility of residual pressure. It was noted that in this aircraft type, the parking brake can remain partially engaged even when the control knob is set to the off position, necessitating manual pressure on the pedals to ensure a full release. The investigation also looked into the use of hydraulic fluids, noting that the use of MIL-H-5606 instead of the required MIL-H-83282 could increase fire risks due to a lower flashpoint.
Findings
- The crew performed the takeoff without realizing that residual hydraulic pressure was causing the left brake to drag throughout the taxi and takeoff roll.
- The friction from the dragging brake generated extreme heat, leading to the failure of brake seals and a subsequent hydraulic fluid leak.
- This leak ignited in the wheel well, creating a fire that eventually caused the structural failure of the left wing.
- The left engine propeller was found to be non-rotating at the time of impact, having been bent back under the engine during the crash.