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Atlas Air 767 down/Texas

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Atlas Air 767 down/Texas

Old 6th Mar 2019, 18:14
  #321 (permalink)  
 
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Originally Posted by DaveReidUK
Yes, though that doesn't seem to be relevant to what actually happened.

A "zero G" descent (or indeed a descent at any constant vertical acceleration value) follows a parabolic profile (ask any trainee astronaut). The actual descent profile, as far as it's possible to ascertain from FR24, was at an almost constant flightpath angle.
Well, I am not arguing this or that beeing the cause of the crash, I am only speculating as to the effect of an free floating HS.

With that said I really thought the vertical speed increased significantly all the way down to the ground?
If it was at an almost constant flight path angle, then the transition from more or less level flight about 20 sec prior to the aircraft hitting the ground, to the constant nose down angle must have happened extremely quickly and hence required a very high value of negative G for a few sec
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Old 6th Mar 2019, 18:32
  #322 (permalink)  
 
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Taking a step back it appears to me that something quite dramatic occurred to rapidly transition this airplane from relatively stable, level flight to a very steep dive that took it from 6000' to the water in less than half a minute. We can postulate all sorts of root causes - hopefully the combination of CVR, FDR, and examination of key portions of the wreckage will shed light on what actually went wrong. This event happened so quickly that I don't see how it could be associated with stabilizer motion at rates that the jack screw is capable of generating. It is possible that elevator hard over (both sides) could have led to this result. I would hope that the time histories of the tail surface positions, pitch attitude, roll attitude, and normal acceleration are made public sooner than later.

For now I think that it would be prudent for current 767 operators to make sure that they are up to date on all maintenance and inspections associated with horizontal stabilizer and elevator control. The 767 has a very extensive and solid history of safe operation so I would be very surprised to see design listed as a cause of this loss.
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Old 6th Mar 2019, 18:44
  #323 (permalink)  
 
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767 may, of course, have different structural geometry - tdracer would probably know.
Sorry, but my expertise is in propulsion/engines - I'm not very knowledgeable about the structural aspects or details of how the flight controls work.

Pretty much all I can add in that respect is that I was on the Boeing Safety Review Board (SRB) for many years - in the aftermath of the Alaska MD-80 jackscrew crash Boeing did a study to determine if any of the Boeing models had a similar susceptibility and determined that the Boeing designs were still safe. But I don't recall any meaningful details.

BTW voyageur9 - I have worked with the NTSB on several occasions and have the highest respect for the people I worked with. Yes, they do tend to get information and reports out quickly - especially when things are reasonably clear cut. Just saying that the NTSB releasing information to the public is not a priority unless they believe there is some safety aspect that should be quickly addressed.
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Old 6th Mar 2019, 18:45
  #324 (permalink)  
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Originally Posted by FCeng84
Taking a step back it appears to me that something quite dramatic occurred to rapidly transition this airplane from relatively stable, level flight to a very steep dive that took it from 6000' to the water in less than half a minute. We can postulate all sorts of root causes - hopefully the combination of CVR, FDR, and examination of key portions of the wreckage will shed light on what actually went wrong. This event happened so quickly that I don't see how it could be associated with stabilizer motion at rates that the jack screw is capable of generating. It is possible that elevator hard over (both sides) could have led to this result. I would hope that the time histories of the tail surface positions, pitch attitude, roll attitude, and normal acceleration are made public sooner than later.

For now I think that it would be prudent for current 767 operators to make sure that they are up to date on all maintenance and inspections associated with horizontal stabilizer and elevator control. The 767 has a very extensive and solid history of safe operation so I would be very surprised to see design listed as a cause of this loss.
Take a look at post 97, some type of roll cloud or wind rotation could be the trigger to an aircraft structural failure or improper response by either the autoflight system or crew.
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Old 6th Mar 2019, 18:56
  #325 (permalink)  
 
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Originally Posted by FCeng84
This event happened so quickly that I don't see how it could be associated with stabilizer motion at rates that the jack screw is capable of generating.
I don't think anyone will disagree with that. A screwjack/ballnut failure, on the other hand, could be implicated.
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Old 6th Mar 2019, 19:09
  #326 (permalink)  
 
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Originally Posted by mustangsally
We lost three fellow airman, may they rest in peace.
Not in any way trying to detract from the technical discussion, here is a blog post about a moving tribute to the jumpseat rider.

United Airlines Presents Flight 3591 Widow with Wings and Epaulets, Leaves Indoc Seat Vacant

thepilotwifelife/ 6 comments

On February 23, 2019, tragedy shocked the aviation world when Atlas Flight 3591 went down in Trinity Bay just outside of Anahauc, TX just before 12:45 pm CST. The flight was a cargo transport from MIA to IAH for Prime Air using a twin-engine Boeing 767 and had three people aboard – Captain Ricky Blakely, FO Conrad Aska, and Mesa jumpseater Sean Archuleta. There were no survivors.

When tragedy strikes the aviation world, it affects all of us. We are a tight-knit family, and we are all only a few degrees from the incident. If we did not know those involved, we know those who did. We all pray, hope, and believe that these types of events will never rock our world, but when they do we stand together as one family, regardless of type rating, airline affiliation, or even country of origin. Even though the media did not feel like it was a ‘big story’ and it quickly fizzled out because the jet was cargo and there apparently weren’t enough people aboard to warrant wide coverage, to us it is our family. It affects us all to the core and leaves us with an empty hole in our hearts and in our extended family.

Captain Archuleta was, by all accounts, a standup guy who was easy to be around and who cared immensely for others. “I was friends with and flew with Sean,” states Captain Cole Goldenberg. “He would’ve been the first person there for everyone else in a tragedy like this. He is a very special guy.”
Captain Archuleta (R) as remembered by his friend and fellow pilot Cole Goldenberg (L). Photo with permission.

Just before the tragic accident that took his life, Captain Archuleta had been hired by United Airlines (UAL) and had already been assigned his class date – he was on his way to the majors! This is a celebratory event that we all look forward to as we move through the life of aviation, and it was not different for the Archuleta family. However, fate took away their moment and left a PW sister behind with her young children to figure out how to face another day without her Captain.

In a gesture of kindness, respect, and utmost class, United Airlines is doing something incredible. During Sean’s Indoc class on March 12th, they will leave his seat vacant in memory of the great loss that rocked the aviation world and the hole that is left in all of our hearts. What an incredibly honorable and classy gesture!

Furthermore, they presented his widow with UAL wings and epaulets. As told by UAL Captain Gunn:

“An update regarding Captain Sean Archuleta. He was the jumpseat rider on the prime Atlas/Prime Air crash who had a class date to begin at United, this week I believe. I operated flight 1009 to Bogota on Friday March 1st. Prior to heading to the airport, I was contacted by the IAH Chief Pilot and informed that his widow would be on our flight returning to Colombia where she currently lives. He asked if I could deliver a package to her from United. Of course I agreed to help in any way that I could. United had her booked in First Class and escorted her to the Polaris Club before the flight with plans for a personal escort to the airplane for departure. I coordinated to have her escorted to the plane and be in her seat about 5 minutes prior to general boarding. His wife Titania speaks only Spanish and although I speak some Spanish it’s definitely not conversational. I offered my condolences on behalf of United Airlines and all United pilots. The circumstances were difficult especially considering that I had never met her. I delivered a stack of condolence cards form both United and Mesa Airlines (his current employer) as well as a set of United wings and Epaulets. She was a very lovely lady but she broke down when I gave her the wings/epaulets. It was clearly very emotional for her to receive the wings. However, I could tell that she was very moved and it meant a great deal to her. Through the interpretation of the flight attendant, she told me that she would save these for her children to see and so that they would know that he was a United pilot. I simply said that it would have been a pleasure and and honor to fly with her husband. She thanked me and told me that United had been very good to her and that she was grateful for their support. It appears that United stepped up and treated her with respect and helped an already tragic situation.”

Hats off for an awesome gesture of kindness, respect, and utmost class. I think the fact that they did not feel the need to publicize their act of kindness as even more upstanding and honorable. There is enough negativity in the world. There is enough hatred and stereotyping to fill up volumes. The media often clings to those things that are certain to up readership and line pockets. However, THIS is the stuff we should make viral, friends!

Well played UAL, well played.



https://thepilotwifelife.com/united-...c-seat-vacant/


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Old 6th Mar 2019, 19:35
  #327 (permalink)  
 
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Originally Posted by PJ2
CONSO, this indicates a "proposed" rule-making. Was the AD actually published and is it in force today? Tx.
I'm sure those more familiar with proposed versus final AD, and how to trace can find or give a definitive answer- especially on this forum. I posted it for a link to related information on 767 horiz stab jackscrew and the mention of ballscrew versus MD " NUT" issues.

I have found a bit further related information at

https://www.federalregister.gov/docu...-767-airplanes

and I'll let the experts- and those most familiar with either maintainance records of a given airframe follow up with links if possible to factual data on that 767.
FWIW-around 1982 I had a small task to quickly make a manufacturing ' tool ' to drive the 767 horiz stabilizer during factory checkout before installation of any electrical or hydraulics. I was able to use a piece of 1/4 inch airhose, two screw band type clamps , one on hose over drive spline and one on hose over a 1/8 socket attached to a a low speed 1/4 hp air nutrunner. That kluge was used for a few months until a nicely fitting female match to the spline drive was made attached to a low speed nut runner to move the stabilizer thru its full motions after mounting and basic installation. Of course with no air-loads it was VERY easy and required very little torque. Sort of like your car steering wheel with front wheels off ground- which also uses a ball screw- jack type mechanism.
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Old 6th Mar 2019, 19:48
  #328 (permalink)  
 
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Correct me if I'm wrong, but we only know it was uncontrollably the last 18 seconds but not before that. Was there a problem already or not? So we can do the math with G forces or not, nobody knows at this time.
One thing I think we can scratch is if it was deliberate because than it would have been controlled.
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Old 6th Mar 2019, 20:31
  #329 (permalink)  
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Thank you, DaveReidUK & CONSO for info on the AD.
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Old 6th Mar 2019, 21:08
  #330 (permalink)  
 
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Hotel Tangop

Originally Posted by Hotel Tango
mustanfsally, there's nothing wrong with venting ideas as long as it comes from those sufficiently qualified to make comment (though admittedly that's not always the case). That's what PPRuNe is all about didn't you know? If it upsets you, I guess it's best just to ignore this thread.
HT, you miss read me. But, that is OK, my wife does the same. But frequently the comments posted come from someone with little knowledge of 767 systems and how they relate to this accident. I personally have over thirty five years as a crew member but have zero 767 experience. So I don't speculate on what happened or the cause and effect. If we could weed out the rift raft and get those with good understanding of the specific aircraft systems then I would agree with you. But that just does not happen in this pprune world. Just go back and reread the discussion on elevator trim and pivot points of such, jack screws and nuts et all. Maybe that is why I only look at this web sight for entertainment with a couple of pints.

Cheers
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Old 6th Mar 2019, 21:40
  #331 (permalink)  
 
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If the aircraft was in free fall, it would be accelerating at 1 g, and experiencing 0 g. Two different things.
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Old 6th Mar 2019, 23:10
  #332 (permalink)  
 
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Originally Posted by CAP A330
If the aircraft was in free fall, it would be accelerating at 1 g, and experiencing 0 g. Two different things.
If by "two different things" you mean two different frames of reference, then yes. File under "interesting, but irrelevant".

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Old 7th Mar 2019, 00:56
  #333 (permalink)  
 
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Another video of the crash.

https://www.chron.com/news/houston-t...68603.php#next
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Old 7th Mar 2019, 01:35
  #334 (permalink)  
 
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In the video clip posted above by, Old Boeing Driver, in the zoomed in part of the video, 0:15s onwards, the rate/angle of descent moments before impact seems to decrease slightly, perhaps control was regained and a pull out of the dive was being attempted? Or maybe it's just an anomaly in the video footage?

-RP
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Old 7th Mar 2019, 04:48
  #335 (permalink)  
 
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In the second video it does look to me as well as if the plane begins to pull up a little. At that speed of descent such a manoeuvre would likely tear the wings off if the ground had not intervened first.
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Old 7th Mar 2019, 16:15
  #336 (permalink)  
 
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Without access to the Alert Service Bulletins mentioned in the AD it's difficult to determine how much of the content is applicable and the compliance times. The Bulletins would also indicate the means of terminating inspections and any other closing actions. Given that Wear Measurement and Lubrication are involved it's quite likely
that the repetitive actions have been included in the aircraft's Maintenance Program by now.
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Old 7th Mar 2019, 16:21
  #337 (permalink)  
 
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Originally Posted by McGinty
At that speed of descent such a manoeuvre would likely tear the wings off if the ground had not intervened first.
Utter rubbish...again.
The rate of change determines the forces on the airplane. Do you even know what the V-speeds mean?
You can easily recover from a Vne dive if you do not exceed load limitations.
So nothing “tearing off”.
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Old 7th Mar 2019, 17:32
  #338 (permalink)  
 
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Two halves of the same thing:

A pull-out with careful attention to avoiding load limitations won't pull the wings off - it may very well also not be possible in the altitude/time available (BAD)
A pull-out with a hard enough pull to avoid the ground in the altitude/time available may very well exceed the load limitations (also BAD). Or produce an accelerated stall (see Hawker Hunter air show crash - also BAD)

Takes fine judgement and ingrained knowledge of an aircraft's capabilities to thread that needle - in the middle of a "startle" event.
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Old 7th Mar 2019, 17:38
  #339 (permalink)  
 
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Originally Posted by pattern_is_full
Two halves of the same thing:

A pull-out with careful attention to avoiding load limitations won't pull the wings off - it may very well also not be possible in the altitude/time available (BAD)
A pull-out with a hard enough pull to avoid the ground in the altitude/time available may very well exceed the load limitations (also BAD). Or produce an accelerated stall (see Hawker Hunter air show crash - also BAD)

Takes fine judgement and ingrained knowledge of an aircraft's capabilities to thread that needle - in the middle of a "startle" event.

This ^^^
People please read it again and again.
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Old 7th Mar 2019, 19:33
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Originally Posted by B2N2



This ^^^
People please read it again and again.
Yes. And you can start your self reading it.

When I was reading reply #336 by McGinty I was reading and understanding that reply exactly like pattern_is_full explaines it in reply #339; " A pull-out with a hard enough pull to avoid the ground in the altitude/time available may very well exceed the load limitations (also BAD)."
And i was reading it like that even with my very limited cognitive ability. Some here with claimed better cognitive ability seemingly was not able to read reply #336 that way...
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