NTSB: Icing Effect on Colgan Q400’s Stall Speed ‘Minimal’

 - March 25, 2009, 9:33 AM

Preliminary airplane performance modeling and simulation conducted by the NTSB show that icing had a minimal effect on the stall speed of the Colgan Air Bombardier Q400 that crashed outside Buffalo on February 12, killing all 49 occupants and one person on the ground, the Safety Board said today.

Information from the airplane’s flight data recorder (FDR) indicates that the stick shaker activated at 130 knots, a speed consistent with an engaged de-icing system. FDR data further indicates that when the stick shaker activated, the control column experienced a 25-pound pull force, followed by an up elevator deflection and increase in pitch, angle of attack and g forces. The data indicates a likely separation of the airflow over the wing and ensuing roll two seconds after the stick shaker activated, while the aircraft slowed through 125 knots and while at a flight load of 1.42 gs. 

The NTSB has voted to conduct a public hearing on the accident on May 12 to May 14 in Washington, D.C. The agenda includes icing’s effect on the airplane’s performance, cold-weather operations, sterile-cockpit rules, crew experience, fatigue management and stall-recovery training. 

“The tragedy of flight 3407 is the deadliest transportation accident in the United States in more than seven years,” said acting NTSB chairman Mark Rosenker. “The circumstances of the crash have raised several issues that go well beyond the widely discussed matter of airframe icing, and we will explore these issues in our investigative fact-finding hearing.”

The NTSB’s Operations & Human Performance group has conducted further interviews with flight-crew members who had recently flown with and or provided instruction to the accident crew, as well as personnel at Colgan Air responsible for providing training of flight crews and overseeing the management and safety operations at the airline. The group also conducted interviews with FAA personnel responsible for oversight of the Colgan certificate, which included the Principal Operations Inspector (POI) and aircrew program manager for the Q400. The team also continues to review documentation, manuals and other guidance pertaining to the operation of the Q400 and training materials provided to the Colgan Air flight crews.