You may have seen this. A Prime Air (Amazon) flight went down in TX yesterday, depending on your local value of yesterday. Briefly, it looks to me like the thing suffered a catastrophe at altitude. Good comms were in evidence leading up to the loss, but no communications were heard from the plane as it began a descent that can be described as free-fall modified by the aerodynamics of a broken airplane.
The plane is a 25-year-old 767 which spent decades in the care of several non-US airlines, including two years in storage before being picked up by Atlas, who held the lease (wet/dry unknown) while operated for (or by) prime Air.
Good job DocLor for the link to Flight-Aware, which has the majority of this puzzle laid out.
I followed up on the aircraft’s report “descending via the LINKK”. See the linked approach plates, absolutely necessary to follow what comes next: https://flightaware.com/resources/airport/IAH/STAR/LINKK+ONE+(RNAV)/pdf
When the pilot reports “descending via the link”, the readout gives his altitude as 17.9K ft, speed 320Kts, (indicates he is a (H)eavy), and descending in excess of 1,000 fpm, which is normal. Descent rates, especially in IFR, vary between 1,000 fpm at a minimum (well either we’re descending or not, right?) and 2,500 fpm.
I don’t actually know where any of these named navigation waypoints are — I’m just fitting the evidence to the approach cards. So I could be off about the location og GILLL. There’s some talk on the forums about the right turn being for weather avoidance. But I still think that this is the programmed right turn at GILLL.
It looks to me that the aircraft followed route JEPEG / GIRLY / BBQUE / LINKK / GILLL, and at last turned for GARRR. Per the approach plates, this suggests an (ATC) intended set-up to approach for a landing at RWY 26L or 26R. [Yup, they were directed in the audio to follow thr transitions for 26L] Critically, the aircraft would be limited to between 10K and 8K feet as it crossed GILLL, and should have been doing 240kts.
Now, the approach plates are advisory. ATC instructions are STRONGLY advisory, and the Captain at all times retains discretion over what his aircraft does. So it may be that prior conversations or known schedule issues affected the speeds flown — facts not yet in evidence. That said:
The aircraft is on a course consistent with the 269 required inbound to LINKK, slowing from over 300kts to somewhere between 290 and 300kts at LINKK. His airspeed* crossing LINKK should have been down to 250kts per the approach plates.
The aircraft is required to cross LINKK between 15kft and 12kft altitude at 250kts, and to turn right to course 301, continue descent or maintain to cross GILLL between 10kft and 8kft at speed 240kts.
We see him cross GILLL at time mark 1:06 in this video. He turns consistent with the expected transition from a course of 301 (LINKK to GILLL) to a new heading of 325 (GILLL to GARRR). His speed was not 240, but 290kts. he came across right at the top limit of altitude for GILLL, which is 10kft.
This to me is where the story gets interesting. He is now high and hot, as they say (not in the airfield sense, but flight profile sense), and he needs to lose both altitude and airspeed.
This is assuming that he does not wish for some reason to keep the additional speed for scheduling reasons, but at this point he is close enough to the airport that excess speed no longer helps even in a time crunch. The faster you go close to the airport, the more time you’re going to spend trying to bleed off the excess energy. It’s challenging to lose airspeed and altitude at the same time, as it’s naturally a trade-off.
But I believe that this story begins with getting too high and too fast, and then trying to come down from that.
Just before the pilot reported “descending via the LINKK”, there is a controlled descent from 13:26 to 13:30 in which the aircraft never lost LESS THAN 2500 fpm, but maintained speed, and in the last minute (13:29 to 13:30), actually dumped 30 kts while shedding very nearly 4kft. There’s only one way to shed that much energy, and that’s aerodynamics.
Just after he crosses GILLL and turns right, in the minute from 13:27:00 to 13:28:00, the aircraft dumps another 50 kts while losing 2000 feet. he has gotten his speed down to 250kts (or so), which is the max speed for the initial deployment of flaps on the 767. If the previous hard-braking descent stressed components of the airframe, this is where they finally let go.**
More to follow.
This weather radar picture (swiped from https://www.airlinepilotforums.com/cargo/120196-atlas-767-went-down-houston-3.html) tells a different story than the wx in the video above:
The time in this one is supposed to be 13:20, and the system is moving west to east. That makes this line of weather significantly ahead of the one seen in the video, (last seen still far west of the bay by 13:40). This line doesn’t show up on the video at all.
It could be a time sync issue; latency in availability of web products somehow. Or maybe there was nothing wrong with the plane except for being configured to lose altitude and airspeed and then running out of both in a wind shear. At their altitude, the first thing they would experience hitting a line like this would be a massive tailwind, and a massive updraft. If it hit them hard enough, it could have caused an aerodynamic stall on an aircraft already doing its best not to fly very well. This would be consistent with the unexpected left turn — typically one wing stalls before the toehr and drops, causing an uncommanded turn. This is also consistent with the brief climb indicated on Flight Aware. They may have gotten the wings level without being able to restore level flight, which would be consistent with the rest of the story.
The dog not barking but biting very hard would be an unseen line of weather. If the wx radar is right at the airport or a little northwest of it, the smarty systems might have decided it was an echo of the obvious line just east of the city and blanked it out. Hold this thought.
There’s a comment on a forum from a guy who says that he was in the air, in the area at the time, heard the calls, saw the wx. Said it was mostly “false ground returns”. Except that maybe it wasn’t after all.
I can’t get to mp3 files from where I am now, but check this out: https://forums.liveatc.net/atcaviation-audio-clips/23-feb-2019-atlas-air-(amazon-prime-air)-3591-down-near-kiah/msg71969/?PHPSESSID=r4pqruvut4nmq9j2ukfcot0323#msg71969
I agree with the “Pull Up!” observation noted at that link.
*actually, the approach plates may be spec’d in kts over ground, as opposed to KIAS (Kts Indicated AirSpeed), as they deal with distances between fixed physical features. I won’t be finicky for now.
** In the mudflats video somewhere, there’s a shot of the “smirk” showing that the rudder was with the aircraft when it hit. So it’s unlikely that they ripped it off the way that one Airbus went in in 2001 or so.