Author Topic: Atlas flight 3591 crash  (Read 364 times)

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Offline Omni

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Atlas flight 3591 crash
« on: February 26, 2019, 11:22:59 am »
I saw a video yesterday that outlined the final events of this flight based on radar traces. It showed this 767 descended for the last ~12 seconds @25000 ft/min. Just to confirm, 25000 was not a typo. No wonder it broke up when it hit but what would cause that kind of dive.

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Offline MH

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Offline Omni

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Re: Atlas flight 3591 crash
« Reply #2 on: February 26, 2019, 02:07:57 pm »
I've seen a couple of those too but they don't tell ya much about what the hey happened. I have an idea but I guess we'll have to weight for the black boxes to get the data.

Offline ?Impact

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Re: Atlas flight 3591 crash
« Reply #3 on: February 26, 2019, 03:58:47 pm »
I saw a video yesterday that outlined the final events of this flight based on radar traces. It showed this 767 descended for the last ~12 seconds @25000 ft/min. Just to confirm, 25000 was not a typo. No wonder it broke up when it hit but what would cause that kind of dive.

That is 284mph. That is certainly faster than the terminal velocity of a level airplane, I suspect even if it was in an unpowered nose dive that would be too fast. 12 seconds is 5000 feet above the water level, and I understand it turned when it was at about 8000 feet.

Offline Omni

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Re: Atlas flight 3591 crash
« Reply #4 on: February 26, 2019, 04:12:34 pm »
That is 284mph. That is certainly faster than the terminal velocity of a level airplane, I suspect even if it was in an unpowered nose dive that would be too fast. 12 seconds is 5000 feet above the water level, and I understand it turned when it was at about 8000 feet.

284 mph is well below the Vne for a 767 but it is way faster than it would ever even approach in a normal descent. One question I would be asking in this case would be to the load sheet since this was a strictly cargo aircraft. what was the cargo and where was it loaded? A load shift on descent could throw the C of G far enough forward to put the plane into an uncontrollable dive.   

Offline ?Impact

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Re: Atlas flight 3591 crash
« Reply #5 on: February 26, 2019, 04:32:44 pm »
284 mph is well below the Vne for a 767 but it is way faster than it would ever even approach in a normal descent. One question I would be asking in this case would be to the load sheet since this was a strictly cargo aircraft. what was the cargo and where was it loaded? A load shift on descent could throw the C of G far enough forward to put the plane into an uncontrollable dive.

I thought we were talking about descent rate, not Vne.

Agreed on heavy cargo shifting as a potential cause of the problem.

Offline Omni

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Re: Atlas flight 3591 crash
« Reply #6 on: February 26, 2019, 04:57:48 pm »
I thought we were talking about descent rate, not Vne.

Agreed on heavy cargo shifting as a potential cause of the problem.

Yeah a normal descent rate would be ~1500-2000 ft.min. From what I've seen/heard so far the plane was in one piece when it went in, but was in a nose dive according to an eye witness. Put the nose down to begin descent and a heavy portion of the load slides forward, the C of G could easily move far enough forward to overcome control inputs. And then perhaps the nose slides even further. She's all over but the paperwork.

Offline wilber

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Re: Atlas flight 3591 crash
« Reply #7 on: February 27, 2019, 01:43:12 pm »
That is 284mph. That is certainly faster than the terminal velocity of a level airplane, I suspect even if it was in an unpowered nose dive that would be too fast. 12 seconds is 5000 feet above the water level, and I understand it turned when it was at about 8000 feet.

Normal speed below 10,000 is 250 kts then slowing to 210 kts prior to extending flaps and gear and slowing to its final approach speed. This is really strange.
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Offline Omni

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Re: Atlas flight 3591 crash
« Reply #8 on: February 27, 2019, 03:07:39 pm »
Normal speed below 10,000 is 250 kts then slowing to 210 kts prior to extending flaps and gear and slowing to its final approach speed. This is really strange.

According to the radar trace I saw there was a line of t-storms between them and the airport but they crashed before they got into that so it seems wx wasn't a contributor. I'm still interested in the possibility of load shift. Hard to tell that from this type of wreckage but the FDR might provide a clue with control positions.

Offline wilber

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Re: Atlas flight 3591 crash
« Reply #9 on: February 27, 2019, 03:35:54 pm »
According to the radar trace I saw there was a line of t-storms between them and the airport but they crashed before they got into that so it seems wx wasn't a contributor. I'm still interested in the possibility of load shift. Hard to tell that from this type of wreckage but the FDR might provide a clue with control positions.

Ya but what a strange place for a load shift, no high body angle, no heavy acceleration or deceleration. Normally load shifts happen on takeoff where you have a high nose up body angle and acceleration at the same time. Guess it could have happened on descent though.

The video shows the elevators full nose down but that must be just be part of the program used to make it.
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Offline Omni

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Re: Atlas flight 3591 crash
« Reply #10 on: February 27, 2019, 03:49:22 pm »
Ya but what a strange place for a load shift, no high body angle, no heavy acceleration or deceleration. Normally load shifts happen on takeoff where you have a high nose up body angle and acceleration at the same time. Guess it could have happened on descent though.

The video shows the elevators full nose down but that must be just be part of the program used to make it.

My little attempt at speculation would have the fwd portion of the load not properly secured, so on takeoff it would be held in place by pallets aft that were secured. Then a combination of nose down deck angle/deceleration starts a slow slide fwd during the step down approach that the radar shows, finally resulting in steep nose down attitude/high ROD. Just a guess at this point, and hopefully they get the "boxes" so whatever happened can be revealed.

Offline Omni

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Re: Atlas flight 3591 crash
« Reply #11 on: February 27, 2019, 05:03:57 pm »
Ya but what a strange place for a load shift, no high body angle, no heavy acceleration or deceleration. Normally load shifts happen on takeoff where you have a high nose up body angle and acceleration at the same time. Guess it could have happened on descent though.

The video shows the elevators full nose down but that must be just be part of the program used to make it.

Not sure if you've seen this one but that's not much of a debris trail for a 767. Suggests a lot more vert. vel. than horiz. I'd say.

https://www.foxnews.com/us/search-at-texas-cargo-plane-crash-site-for-third-body-black-box-continues

Offline ?Impact

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Re: Atlas flight 3591 crash
« Reply #12 on: February 27, 2019, 05:35:22 pm »
Normally load shifts happen on takeoff where you have a high nose up body angle and acceleration at the same time.

I assume the load is secured from moving in multiple directions, depending on the items in the load. I could see the case where a strap holding the load from moving forward was improperly attached, or perhaps failed in transit.

That being said, I did hear one statement that the load contained no large items like vehicles being transported. Most of the items were probably in containers, or on palettes. I would assume those lock into rails in the aircraft body, although how those locks work I have no idea; they might also be subject to directional forces.

Offline Omni

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Re: Atlas flight 3591 crash
« Reply #13 on: February 27, 2019, 05:49:54 pm »
I assume the load is secured from moving in multiple directions, depending on the items in the load. I could see the case where a strap holding the load from moving forward was improperly attached, or perhaps failed in transit.

That being said, I did hear one statement that the load contained no large items like vehicles being transported. Most of the items were probably in containers, or on palettes. I would assume those lock into rails in the aircraft body, although how those locks work I have no idea; they might also be subject to directional forces.

In a cargo aircraft the palettes do lock into rails on the deck which holds them in place. However that doesn't stop the load on top from moving if not properly strapped down.

Offline wilber

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Re: Atlas flight 3591 crash
« Reply #14 on: February 27, 2019, 07:57:18 pm »
In a cargo aircraft the palettes do lock into rails on the deck which holds them in place. However that doesn't stop the load on top from moving if not properly strapped down.

Pallets or containers. If containers the locks would have to be not set or failed, if pallets, yes the cargo would have to be secured properly.  Lots to learn here, need those recorders, also wonder what is on the ATC tapes.
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