March 14, 2019
The NTSB has released an initial report on the crash of the Atlas Air flight 3591 which crashed on February 23, 40 miles away from Houston’s George Bush Intercontinental Airport.
The report shows that the plane did, in fact, hit a front of extreme weather.
The report shows from ADS-B data that the plane was following a normal descent and arrival procedure into the airport moments before the accident took place.
The data shows the plane descending through 13,800 feet at which point the controller in charge of the aircraft advised the crew of light to heavy precipitation front that was moving along their initially planned flight route and so they should expect to be given vectors around the weather for their arrival.
The pilots were then asked if they would like to be vectored to the north or the west of the weather for their arrival into the airport on runway 26L.
The data shortly after this new approach was agreed shows the plane continuing to descend through 12,000 feet with a ground speed of 290 knots, which the report states are consistent with the arrival procedure of the airport.
A few minutes later the pilots were instructed by ATC to turn to a heading of 270 degrees, the ADS-B data shows that this command was followed out by the crew and at the point of taking the heading the plane was still in a decent passing through 8,500 feet.
The ADS-B data goes on to show that the plane and pilots were complying with all ATC instructions.
It was at 12:38 the data shows that the aircraft levelled off at 6,200 feet and then started a slight climb to 6,300 feet. The Flight Data Recorder, says the report, “indicated that some small vertical acceleration is consistent with the airplane entering turbulence”.
While there is no confirmation from the NTSB on what caused the crash, the data from the FDR and the ADS-B both imply that the aircraft entered turbulence, which was consistent with the pilots’ input to push the throttles to full power, this is a standard procedure for all pilots when they enter turbulence and the planes steady climb of 4 degrees nose up is consistent with this input.
The data also shows, however, that very shortly after that the plane pitched nose down to around 49 degrees in 18 seconds and the planes speed of 430 knots, there has been no confirmation from the NTSB on whether or not this was a deliberate input or if the aircraft had experienced an extreme downforce, what is clear in this initial report however, is that the stall warner (the stick shake) did not activate.
In the report, a still image is attached from a security camera which caught an image of the aircraft in a 20-degree nose down pitch moments before it made contact with the ground, this image is consistent with the data taken from the FDR which shows that the plane was gradually pulling out of its steep descent.
At this time there has been no comment from the NTSB on what the final cause of the crash was, or what caused the plane to pitch nose down.