The commuter plane that crashed near the northern US city of Buffalo, killing 50 people, was on autopilot as it descended to earth, in violation of federal safety recommendations, a federal investigator said Sunday.
National Transportation Safety Board (NTSB) investigator Steven Chealander said a preliminary review of the flight data and cockpit voice recorders revealed that the plane was on autopilot for part of its approach to the Niagara International Airport in Buffalo, New York.
Chealander said the plane's de-icing system was activated 11 minutes after departure from Newark, New Jersey and remained on for the duration of the flight. The aircraft's stall-protection equipment was also activated.
Continental Airlines Flight 3407 dropped 244 metres in five seconds shortly before it crashed into a house in Clarence Center, New York, killing all 49 people on board and one person in the house.
Chealander described a sickening ride in the plane's last 26 recorded seconds.
The plane pitched and rolled violently before dropping and crashing belly down on the house, finally facing the opposite direction it was heading in.
Federal investigators have suggested that ice build-up may have contributed to the crash.
Black box recordings showed the crew was concerned about the weather and low visibility due to snow and mist as they approached Buffalo. They asked to drop to 11,000 feet, but began to see a problem with ice.
The NTSB has "recommended that in icing conditions it might be best to disengage the autopilot and fly the plane manually so that you have the manual feel for what might be changing in your flight regime because of the ice," Chealander said.
The Federal Aviation Administration (FAA), a regulatory body that can enforce safety recommendations, has followed the NTSB's recommendation but has not yet made it into regulation.
"The FAA sees things a little differently than we do[...] They see that for some reasons, that you may need to be flying with the autopilot," Chealander said, citing workload as one of the reasons.
US media reported that Colgan Air, which was operating the flight for Continental Airlines, had recently started following NTSB's recommendation about disengaging the autopilot in icy conditions.
The flight manual for the Bombardier Dash 8 Q400 turboprop plane asks that the pilot "disengage the autopilot in severe icing conditions," Chealander added, while warning that the NTSB so far "has not determined that it is severe icing. So, so far, we see that everything seemed to be normal in using the autopilot."
He also stressed that "it is normal and you are encouraged to use the autopilot to help with the work loads of these intense - high intense weather situations that we fly into all the time."
Landing gear was down at the time of the crash, he added, indicating that the autopilot was disengaged just before ‘stick shaker’ and ‘stick pusher’ aerodynamic stall protection system was activated before the crash, warning the pilot that there was not enough airflow over the wings to maintain lift.
Forensic teams were still in ‘recovery mode’, recovering victims and parts of the aircraft from the site, Chealander said.
Examination of the two engines so far indicates that "the airplane doesn't seem to have lost anything prior to impact," he added.
Witnesses reported an unusual loud noise coming from the plane, which crashed about five minutes before it was due to land in Buffalo.
Despite the massive heat and wall of flames created by the crash, no other houses in the neighborhood sustained any damage, officials said.