In the wake of a fiery plane crash near Buffalo, New York last Thursday, National Transportation Safety Board (NTSB) investigators are focusing on whether a buildup of ice on the wings or the incorrect use of autopilot may have brought the plane down.

Investigators have been listening to recordings and looking at data from the plane’s black boxes, which were recovered a day after the crash in Clarence Center, New York.

The Dash 8 turboprop was en route from New Jersey to Buffalo when it suddenly veered out of control and dove into a house only six miles from the airport, killing all 49 people onboard and one on the ground.

The NTSB says that it’s too early to draw firm conclusions about the cause of the crash, and that it could take up to a year to complete the investigation. However, one former FAA official said that the plane’s near-vertical drop points to a mechanical failure, possibly cause by ice, which may have caused the wing flaps to deploy asymmetrically or caused the engines to put out unequal thrust.

The nearly new plane did have a state-of-the-art pneumatic de-icing system which is designed to inflate and break up ice that accumulates on the wings. The pilots, who were told to expect “light to moderate” icing conditions when they left Newark airport, appear to have turned on the de-icing system 11 minutes into the flight.  However, investigators say that they cannot be 100 percent sure that the system was working.

Furthermore, the plane appears to have been flying on autopilot up until the last couple of minutes before the crash, when the pilots switched to manual mode. If the auto-pilot is left on too long it can impede the pilot’s ability to recover from an adverse event such as heavy ice buildup on the wings, which can make a plane lose its lift and become difficult to control. FAA guidelines require pilots to fly manually when they are encountering severe icing conditions.

The fact that the plane crashed has led some to speculate that perhaps icing conditions were worse than pilots previously believed, and that they did not realize the extent of the buildup until it had already caused the plane to become functionally disabled. Audio from the cockpit revealed that the pilot and co-pilot noticed significant ice buildup on the wings of the plane in the seconds before it pitched violently toward the ground. Pilots of other planes in the area also noticed similar ice on their wings.

FAA officials say that turboprop planes are more susceptible to ice buildup than jets, because their pneumatic deicing systems are not as effective as the heated wings that jets have.

After two deadly turboprop crashes in 1994 and 1997, the FAA ordered flight crews to activate the boots at the first sign of ice accumulation, and prohibited propeller planes from functioning on autopilot in severe icing conditions.

The NTSB wants the FAA to go even further in its restrictions on flying in icy conditions, and the crash has reignited a debate between the two agencies. For years the NTSB has been calling for more stringent testing of turboprop planes and more aggressive use of de-icing boots in flight.

The FAA however has countered that they do not feel the NTSB’s recommendations were warranted and so far has not adopted them. The recommendations remain on the NTSB’s list of “most-wanted” safety improvements.

Related links: Wall Street Journal, CBS News, Associated Press

By Karen Elowitt for PeterGreenberg.com.

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