Delta plane that crashed at Pearson airport was travelling at high rate of descent, prelim report suggests

The proximity warning system aboard the Delta Air Lines flight that crashed at Pearson airport last month sent an alert indicating a high rate of descent less than three seconds before the plane touched down, according to a preliminary report. 

The report, released Thursday, is part of an ongoing investigation by the Transportation Safety Board of Canada into the  Feb. 17 crash, which sent 21 people to hospital. 

"It is too early to draw conclusions as to the causes of this accident," the board said in a news release Thursday. "A full investigation report, which will include the TSB's analysis into why the accident happened and the Board's findings, will be released in due course." 

The flight, operated by Delta Air Lines subsidiary Endeavour Air, took off from Minneapolis with 76 passengers, two flight crew members and two cabin crew members. The aircraft was a CL-600-2D24 (Regional Jet Series 900) manufactured by Bombardier Inc. in 2008. 

Prior to the crash, the flight "proceeded uneventfully," the report said. 

The first officer was the pilot flying the plane. At the time of the crash, she had around 1,422 hours total flight time, including 418.7 hours on the type of aircraft involved in the incident, the report said. 

The captain was the pilot monitoring for the flight. He had 3,570 hours total flight time at the time of the crash, including 764 hours on the same aircraft type. 

At 2 p.m, winds were gusting to 35 knots in the area, the report said. After flight crew received clearance to land at Runway 23 at Pearson airport, they flew the approach at 149 knots, "given the reported wind gusts," it said. 

Around 2.6 seconds before touchdown, a "sink rate" alert sounded, "indicating a high rate of descent," the report said.  The alert came from the plane's enhanced ground proximity warning system.

At the time the alert sounded, the plane's airspeed was 136 knots, the report said. 

Less than a second before touchdown, the aircraft's indicated airspeed was 134 knots and its ground speed was 111 knots. Around 2:12 p.m., the right main landing gear touched the runway. 

"At touchdown, the following occurred: the side-stay that is attached to the right [main landing gear] fractured, the landing gear folded into the retracted position, the wing root fractured between the fuselage and the landing gear, and the wing detached from the fuselage, releasing a cloud of jet fuel, which caught fire," the report said.

"The exact sequence of these events is still to be determined by further examination of the fracture surfaces." 

The plane then began to slide along the runway, eventually going off the right side into a snow-covered grass area and coming to rest on Runway 15L, near the intersection with Runway 23.