A cockpit voice recorder transcript shows Renslow and Shaw discussing careers and her lack of experience flying in icy conditions during the plane's final minutes, even after they had noticed a buildup of ice on the windshield and wings.
Dismukes agreed that the voice recorder shows the two were distracted, not realizing their danger until a stall warning system that violently shakes the pilot's control column went off. He said that probably grabbed Renslow's full attention and he may not have realized even then how low the aircraft's speed had dropped.
Asked by Hersman if pilots might benefit from an audible low-speed warning system, Dismukes said: "Absolutely, you want a very distinctive alert, but not one that is so dramatic. That's well worth looking at."
Hersman said the stickshaker warning came too late and was too sudden.
"I think this crew went from complacency to catastrophe in 20 seconds," she said. "The room is on fire at that point."
Seven seconds after the stick shaker went off, with Renslow apparently still wrestling with the control column, the plane's stickpusher kicked in, a second system that automatically points the aircraft's nose downward in response to an aerodynamic stall, which means the plane lost lift. The plane rocked back and forth and then plunged into a house below, killing all 49 aboard and one man on the ground.
The board recommended to the Federal Aviation Administration in December 2003 that regulators study whether an audible low-speed warning system designed to grab a pilot's attention should be required. FAA responded in 2006 that it had formed a team to study the issue and hoped to have results in 2007.
The board made the recommendation in response to a 2002 air crash in Minnesota in which Sen. Paul Wellstone and his family were killed. The board concluded in that crash that the flight crew of the charter plane failed to realize that the King Air A100, a small twin-engine turboprop, had slowed to a dangerously slow speed in preparation for landing. The low speed caused an aerodynamic stall, resulting in that crash.
Some aircraft already have audible low-speed warning systems that say "speed, speed, speed ..." The Bombardier Dash 8-Q400 in the Buffalo crash didn't have an audible warning system, although it had low speed "barber pole" warning system that changes color.
The NTSB's three days of hearings this week have raised a slew of safety issues involving pilot training, hiring and pay. Renslow, 47, and Shaw, 24, were based at Newark Liberty International Airport in New Jersey, but he commuted from his home near Tampa, Fla., and she lived with her parents near Seattle. NTSB investigators said the pair may not have been able to afford to live in the New York metropolitan area on their salaries and may been fatigued by their commutes and long work schedules.
Dismukes said studies show pilots are more vulnerable to distraction when they are fatigued.
New York Reps. Chris Lee, Louise Slaughter and Brian Higgins said Thursday they will push for a congressional investigation of all commercial airline pilot training and certification programs.
Sen. Charles Schumer, D-N.Y., sent a letter Thursday to Transportation Secretary Ray LaHood urging him to ensure that the FAA reevaluates its pilot training requirements and curriculum.
"NTSB's hearings have indicated that lack of hands-on training of a stick-pusher may have played a role in the crash of Flight 3407, and I wonder what other important training exercises may be left of out of curricula," Schumer wrote.
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Associated Press Writer Kimberly Hefling contributed to this report.
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