From the NY times, Feb 18, 2009:
Buffalo Crash Inquiry Sees Signs of Crew Error
By MATTHEW L. WALD
A re-creation of the last moments of the plane that crashed in Buffalo Thursday night, based on data from the “black boxes,” shows that the crew may have overreacted to an automatic system that was trying to protect the aircraft from flying too slowly and crashing from an aerodynamic stall.
By using the data to create a computer animation of the flight’s final seconds, investigators have developed a theory that after the automatic system pointed down the nose of the plane to generate speed, the crew may have overreacted by yanking back on the yoke and pointing the nose too high, according to a person familiar with the animation. The nose then plunged, and the airplane rolled and crashed into a house outside Buffalo, killing all 49 people on board and one man on the ground. The Wall Street Journal reported on its Web site on Tuesday evening that the investigators were looking at crew action as a possible cause of the crash.
The plane, Continental Connection Flight 3407, from Newark to Buffalo, was flying on auto-pilot. In that aircraft, a Bombardier Dash 8 Q400, that device can control altitude and course, but not the throttle, according to aviation experts. According to the National Transportation Safety Board, when the “stick-pusher,” which takes control of the plane and points the nose down, activated and the autothrottle kicked off, the crew tried to increase power. Apparently there was not enough altitude or time to recover control, however.
The stick-pusher may have activated at a speed higher than normal because it added a margin of safety to account for icing conditions, investigators say.
Investigators believe that the pilot at the controls was the captain, Marvin Renslow, who had begun flying the Dash 8 only in December. He previously flew a smaller turboprop, the Saab 340. That plane is subject to a problem in bad weather called tail plane icing, in which the airplane’s tail suddenly ceases to function in its role of applying downward pressure at the back to the plane, and holding the nose up. He may have been alert to the possibility of the nose dropping in icing for that reason. But Safety Board personnel at the crash scene said that the Dash 8 is not susceptible to the tail plane problem.