What are the causes of the crash:
The following analysis is the summary of the findings made by the NTSB in their report available on their website.
I want the readers to know that my goal by writing this article is not to judge the crew. I just want to learn from what happened to become a better pilot.
Here are the elements the NTSB studied:
– Flap anomaly
Even if the plane was having a flap asymmetry problem, the NTSB concluded that the plane was still flyable and didn’t directly caused the accident even if it’s one element of it.
Nevertheless, the fact that the crew got distracted by the anomaly caused the First Officer not to focus on the airspeed leading to a stall warning activation.
Also, the crew didn’t follow the Procedure that deals with a flap anomaly. If the crew did so, most likely they would have gone around, hold for a bit to get the time needed to accomplish the checklist dealing with the problem and come back for landing.
The investigators studied the effect of ice on the accident. The way I understood it, ice leads to a higher stalling speed but the crew was aware of it, took the necessary actions to counter it and set the minimum airspeed right, taking into consideration the higher stalling airspeed.
As wether the ice led to the freezing of the flaps actuator, it is not precisely determined during the investigation because the concerned actuator was badly damaged by the fire and because the history of the plane shows that some repairs were needed in the flap system. The actuators might have been weakened in the past already.
Since the plane was not in a stabilized approach, the crew should have gone around.
The NTSB reminds pilots that if the plane is not in a stabilized state before landing, a misapproach procedure must be initiated.
Here are the elements to qualify an approach as non stabilized. You must go around when excessive deviation from glide path, when sink rate is higher than 1000 ft/min, when airspeed is lower than the required approach speed, when there’s a flap anomaly, when there’s stall warning and stick shaker activation, when terrain collision awareness activates and other warning systems.
The crew faced many of those elements and didn’t go around.
The NTSB noticed that the airspeed deviation was not called out and that inappropriate response was given to the stall warnings.
– First Officer assertiveness
The FO asked the Captain if they should go around. The Captain quickly dismissed her request by a no. Since the Captain was a very experienced pilot, she didn’t challenge his decisions even if she felt that was the right thing to do.
– Human fatigue
The investigation found out that the Captain might have some sleep debt prior to the flight. This is open to discussion because the Captain’s sleep debt was not obvious and because it differs from one pilot to an other.
– Rescue operation
The NTSB pointed out that after the crash, rescue had no way to know if there were still people inside the plane. Consequently, the rescue took unnecessary risks. This is due to the fact that the crew had to flee the burning plane and they didn’t have time to report by radio that they were going out.
The NTSB’s PROBABLE cause for the accident is the failure by the crew to maintain a safe airspeed during the approach