Colgan Air has submitted a formal report to the US National Transportation Safety Board (NTSB) explaining the carrier believes the fatal February 2008 crash of one of is Bombardier Q400 aircraft was loss of situational awareness by pilots, whose failure to follow company procedures led to a loss of control of the aircraft.
The accident occurred in 12 February as the aircraft was approaching Buffalo airport enroute from Continental's Newark hub. Colgan operates 14 Q400s as Continental Connection primarily from Newark.
Subsequent NTSB hearings triggered a significant amount of scrutiny of US regional airline operations after questions arose over adequate training, pilot commuting and fatigue.
Colgan tells the NTSB it has determined the crew failed to follow the airline's training regarding proper response to a stick shaker stall warning. "Rather release back pressure as he was trained to do, the captain pulled back from the yoke," says Colgan. The airline also states that runs performed by NTSB in a Q400 simulator showed that if the accident flightcrew had performed according to Colgan training on approach to stalls, the stall would have been avoided.
The Air Line Pilots Association (ALPA) believes the Q400's design does not include a minimum manoeuvring low speed alert, which the union in its analysis submitted to NTSB says would have provided the crew with an additional visual or aural cue of the aircraft's rapid deceleration.
Highlighting the low-speed cue on the Q400 provides only a visual display, ALPA explains: "Once the airspeed is at that cue the autopilot will disconnect and the stick shaker will activate, potentially leading to a surprised crew needing to handle an emergency situation."
ALPA believes Colgan's training was inadequate, and argues the airline's use of training on tailplane stalls through a NASA video as icing training was incomplete. "There was no discussion of the fact that a stick shaker is only indicative of a wing stall, not a tailplane stall."
The aircraft was operating in icing conditions from shortly after takeoff until the accident on final approach, says Colgan.
In its analysis ALPA explains Bombardier on the Q400 has added a new element to the aircraft's stall protection system called reference speeds swtich, which is used when operating in icing conditions.
A reference speeds switch on the aircraft is designed to increase stall margins supplied by stall protection systems when the "INCR" position is selected. The system uses a lower angle of attack threshold for stick shaker activation, which effectively supplies a stall warning at higher speeds than normal conditions.
Colgan states the crew operating the accident aircraft correctly positioned the reference speeds switch to the correct position for icing, but it errantly set another speed indicator to a normal approach speed for 50 feet above the runway. Ultimately the stick shaker activated at higher speed than was set by all speed indicators, "which most likely surprised the crew", says Colgan. "And they may not have properly analyzed the stick shaker activation."
Colgan tells NTSB that setting one speed indicator to normal approach speeds when other speed measurements are set for icing conditions does not trigger a visual or aural warning in the Q400. The carrier explains the aircraft does not supply feedback to crews indicating that specific speed indicator combination could trigger a stall warning at speeds above regular low speed cues.
Colgan cites that lack of warning in the aircraft as a contributing factor to the accident. Bombardier was not immediately available for comment regarding the speed alerts.
The carrier also highlighted "non-pertinent" conversation between the pilot and first officer that garnered a lot of public attention during hearings earlier this year as a contributing factor to the accident.
"The accident crew flight crew violated Colgan Air policy and FAA regulations by breaking sterile cockpit during the descent to Buffalo," the carrier states.