From the AP:
The plane was about six miles from the runway when it started lurching dramatically, pushing passengers into their seats with twice the normal force of gravity, and was only about 1,600 feet above the ground, too low and possibly too slow to regain control, according to preliminary information from investigators.
Icing on the windshield and the front edges of the wings, which was reported by the crew, is suspected of having been a factor but is far from proved.
Continental Connection Flight 3407, from Newark Liberty International Airport, crashed into a house in Clarence Center, N.Y., killing all 49 people on board and one man inside the home.
Closer examination of the cockpit voice recorder and the flight data recorder from the plane, a twin-engine turboprop Bombardier Dash 8 Q400, shows that 26 seconds before the recordings were stopped by the impact, a warning alerted the crew that the plane might lose lift and fall out of the sky, and an automatic system tried to push the nose down to gain airspeed. But soon the nose climbed to 31 degrees, far steeper than the steepest normal climb. Suddenly, the nose plunged to a downward angle of 45 degrees, almost like a fighter plane breaking off to dive. Then it rolled to the right, beyond 90 degrees, all the way to 106 degrees.
Steven Chealander, the member of the safety board assigned to the investigation, also said that the crew had turned on the plane’s sophisticated de-icing system shortly after leaving Newark, long before the crash. Such systems can sometimes be ineffective if they are turned on too late, but that does not appear to have been the case here.
And the weather conditions, as they were described to the crew before takeoff and as the captain and first officer discussed en route, did not appear atypical for a winter night in the Buffalo area. “We don’t know that it was severe icing,” Mr. Chealander said. “They didn’t say that it was severe icing,” he said, referring to the cockpit crew, and “the weatherman didn’t say that it was severe icing.”
If the trouble began with a huge upward jump of the nose, then another hazard of turboprop aircraft, ice buildup on the tail, was probably not an issue.
Sometimes ice limits the ability of the tail to perform its main function, which is to control the up-and-down movement of the nose. Normally the tail exerts a downward force, moving the nose up as pushing down on one end of a seesaw will raise the other end. Sometimes if ice builds up, the tail will still function well enough for a plane to cruise in flight, but will not work well enough when the crew makes a change in the configuration of the airplane, by, for example, lowering the flaps before landing.
The plane started losing control as the crew lowered the flaps and the landing gear.
Asked why the nose rose, Mr. Chealander said, “There’s a lot of possibilities.” The safety board usually takes a year to 18 months to reach a conclusion, although often within a few days of a crash, the general outlines are clear. That is not yet the case here.
The accident was the first fatal crash of a scheduled airline flight in the United States since 2006, and the deadliest since November 2001, when American Airlines Flight 587 crashed in Belle Harbor, Queens, killing 265 people.
The crash of Flight 3407, particularly because the crew had reported icing conditions, has reignited a debate about the use of the autopilot. The safety board, following a crash in 1994, pointed out that using the autopilot in icing conditions can mask the problem. The plane can fly along the desired path without giving any sign that the controls are becoming sluggish or hard to manipulate, both signs of icing. A human who was flying the airplane manually might feel those effects.
The Continental Connection crew used the autopilot until it shut itself off, about 26 seconds before impact.
But Mr. Chealander on Sunday read from the airplane flight manual, written by the manufacturer, Bombardier, and adopted by Colgan Air, the operator that Continental contracted with. It allows for use of the autopilot unless the plane faces “severe icing conditions.”
“Thus far we haven’t determined that it was severe icing,” he said. A weather team is examining that question.
Another issue for regional airlines like Colgan is that they tend to employ entry-level airline pilots. Mr. Chealander said the captain, Marvin Renslow, 47, had 3,379 hours of flying experience, which is fairly high, but he had been flying the Dash 8 only since December. The first officer, Rebecca Lynne Shaw, 24, had 2,244 hours, which Mr. Chealander said was “experienced as well.” She had 774 hours in the Dash 8.