Tue, Feb 17, 2009 - Page 7 News List

Experts analyzing voice recorders from Buffalo crash


The sounds of the last desperate minutes in the cockpit aboard Flight 3407 could be clues to the cause of a crash that came violently and suddenly, with the doomed plane dropping steeply and pitching and rolling like a rollercoaster.

Investigators in Washington and Buffalo huddled on Sunday at the start of an in-depth study of the plane’s voice cockpit and voice data recorders. Hours later, National Transportation Safety Board member Steve Chealander released facts illustrating how the Continental Connection flight disappeared from radar late on Thursday, plunging into a house and killing 50 people.

Chealander said information from the plane’s flight data recorder indicated that the aircraft pitched up at an angle of 31 degrees in its final seconds, then pitched down at 45 degrees.

The plane rolled to the left at 46 degrees, then snapped back to the right at 105 degrees — 15 degrees beyond vertical.

Radar data shows Flight 3407 fell from 550m above sea level to 309m in five seconds, he said.

Passengers and crew would have experienced G-forces up to twice as strong as on the ground.

The plane crashed belly first on top of a house about 10km short of Buffalo Niagara International Airport, two to three minutes from when it should have touched down on the runway.

Just before they went down in a suburban neighborhood, the pilots discussed “significant” ice buildup on their wings and windshield.

Other aircraft in the area told air traffic controllers they also experienced icing around the same time.

Chealander said in an interview that the pilot may have rejected federal safety recommendations and the airline’s own policy for flying in icy conditions by leaving the autopilot on even after he notified air traffic control that the flight crew had spotted ice on the leading edge of the wings and the windshield.

The Dash 8 Q400 plane, operated by Colgan Air, was equipped with a “stick shaker” and “stick pusher” mechanism that rattles the yoke to warn the pilot if the plane is about to lose aerodynamic lift, a condition called a stall. If not corrected in time, the mechanism automatically pushes the stick forward to avert a stall.

Chealander said the plane was on autopilot until the “stick shaker” and “stick pusher” kicked in, automatically putting the plane back in the pilot’s hands.

At some point, the pilot switched on an anti-stall device that increases the speed of the plane by 20 knots and gives a pilot more margin to recover from a stall if it occurs.

Chealander was careful not to be critical of the pilot: “Everything that should have been done was done, so we keep looking.”

By Sunday, authorities had recovered the remains of 15 people from the wreckage as crews raced to finish their work before a storm expected later in the week.

Recovery crews could need as much as four days to remove the remains from the site.

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