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Atlas Air 767 down/Texas

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Atlas Air 767 down/Texas

Old 12th Mar 2019, 20:07
  #481 (permalink)  
 
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Originally Posted by SamYeager View Post
The phraseology in part of that link now reads

The airplane then pitched nose down over the next 18 seconds to about 49 in response to nose-down elevator deflection. The stall warning (stick shaker) did not activate.
Previously the bolded part said "a control input".
Actually it said:

then rapidly pitched nose down to about 49 in response to column input.
Curiouser and curiouser…
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Old 12th Mar 2019, 20:16
  #482 (permalink)  
 
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So, it seems that the gist of this now is that the AP got haywire thinking the aircraft was a Stuka bomber attacking some ground forces. And the crew was not able to or didnt succed in disconnection the AP.
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Old 12th Mar 2019, 20:22
  #483 (permalink)  
 
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Originally Posted by SteinarN View Post
So, it seems that the gist of this now is that the AP got haywire thinking the aircraft was a Stuka bomber attacking some ground forces. And the crew was not able to or didnt succed in disconnection the AP.
Even then, what pushed up the autothrottles to max? Both autopilot and autothrottles can normally easily be disconnected and/or overpowered.
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Old 12th Mar 2019, 20:35
  #484 (permalink)  
 
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I wouldn't make too much of that wording change.

Maybe it was a reaction to people saying they were blaming the pilots.

I mean they should have the column forces on the FDR readout.
Would surprise me if the person writing "in response to column input" didn't check the column force before writing it.
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Old 12th Mar 2019, 20:46
  #485 (permalink)  
 
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On the contrary, Im inclined to think that if they went to the trouble of changing the wording itd because it is in some way significant. Curiouser indeed.
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Old 12th Mar 2019, 20:49
  #486 (permalink)  
 
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Originally Posted by wiedehopf View Post
I mean they should have the column forces on the FDR readout.
AFAIK, control column deflection and control force aren't mandatory FDR parameters per Annex 6.

So it may be that it was inferred from the elevator deflection (which is of course a mandatory parameter) and the inference subsequently corrected.

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Old 12th Mar 2019, 20:56
  #487 (permalink)  
 
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Does full power on the 767 generate much pitch up. In other words if you had run out of ideas to raise the nose might you try it? Clutching at straws here......
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Old 12th Mar 2019, 21:09
  #488 (permalink)  
 
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A question for 767 knowledgeable crew/engineers. If one of the (two?) autopilots is engaged, and the control columns are pulled fairly/very hard, does the AP disengage at some level of force or does it require positive selection of a button or switch?

I'm thinking of the Eastern Tristar that crashed in the Everglades, in that case gentle pressure on one column was enough to disengage altitude hold but I don't know if that caused the autopilot to release all control surfaces or if it was in one axis. I recall reading that there was a quiet chime that wasn't noticed when this happened whereas I thought that an AP disengaging is indicated in a louder and more attention-getting manner.

I saw up thread that an investigator commented that the Atlas crew "fought the automation" but logic suggests that significant control movement is clearly different from wanting the AP to keep doing what it was previously commanded to do.
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Old 12th Mar 2019, 21:13
  #489 (permalink)  
 
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Descending In IMC, receives sudden W/S warning. Throttles goes to the stops, aircraft pitches up. Spatially disorientated pilot notices airspeed not building, pushes control column forward and holds it until things 'start feeling right'. Realises what's going on, hauls back on column but too late.

Don't know, just an idea.
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Old 12th Mar 2019, 21:24
  #490 (permalink)  
 
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Originally Posted by ASRAAMTOO View Post
Does full power on the 767 generate much pitch up. In other words if you had run out of ideas to raise the nose might you try it? Clutching at straws here......
Absolutely and certainly an option if you've run out of nose up pitch authority.
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Old 12th Mar 2019, 21:27
  #491 (permalink)  
 
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Originally Posted by Feathers McGraw View Post
A question for 767 knowledgeable crew/engineers. If one of the (two?) autopilots is engaged, and the control columns are pulled fairly/very hard, does the AP disengage at some level of force or does it require positive selection of a button or switch?

I'm thinking of the Eastern Tristar that crashed in the Everglades, in that case gentle pressure on one column was enough to disengage altitude hold but I don't know if that caused the autopilot to release all control surfaces or if it was in one axis. I recall reading that there was a quiet chime that wasn't noticed when this happened whereas I thought that an AP disengaging is indicated in a louder and more attention-getting manner.

I saw up thread that an investigator commented that the Atlas crew "fought the automation" but logic suggests that significant control movement is clearly different from wanting the AP to keep doing what it was previously commanded to do.
Yes the AP's will disengage. Something to remember if you inadvertently ground engage the AP's on a 777 and wonder why it won't rotate at VR
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Old 12th Mar 2019, 21:44
  #492 (permalink)  
 
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Originally Posted by LookingForAJob View Post
On the contrary, Im inclined to think that if they went to the trouble of changing the wording itd because it is in some way significant. Curiouser indeed.
Not really. Shortly after the NTSB posted the original update with the "control column input" reference, several individuals on their twitter feed started pointing to "an intentional act." Subsequently, the update got updated again with the "column input" deleted. Just another example of social media leading the narrative vs the people who actually know.
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Old 12th Mar 2019, 22:38
  #493 (permalink)  
 
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Originally Posted by wrench1 View Post
Not really. Shortly after the NTSB posted the original update with the "control column input" reference, several individuals on their twitter feed started pointing to "an intentional act." Subsequently, the update got updated again with the "column input" deleted. Just another example of social media leading the narrative vs the people who actually know.
It's more likely that nobody knows. The NTSB didn't say that there was an absence of control column input. That suggests that they can't actually tell control column deflection from the FDR.
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Old 12th Mar 2019, 22:43
  #494 (permalink)  
 
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Originally Posted by pattern_is_full View Post
This is not even speculation, just a "scenario" that might fit that reported throttle and control-input reading.

Massive incapacitation of PF (bird through the windscreen, medical, other), body pitches forward onto both column and (hand) throttle levers. Nose-over forces make it impossible for the other pilot and jumpseater to clear the controls until too late (that possible last-second attempt to get the nose up).

EDIT: I see I'm not alone - but it would certainly require a "Black Swan" event.
Pattern, I've been thinking sudden incapacitation for a couple of weeks (early on I postulated a large bird through the forward bulkhead as a possibility if you go back enough pages) - or something acute such as a massive heart attack could pitch the PF forward into the controls (granted, also moving the throttles makes it somewhat less likely - but SOP is to have a hand on the throttles during approach so not impossible). 18 seconds is not much time to overcome the startle factor, recognize and react to something completely unexpected - especially with a 200 lb. pilot laying on the yoke. In short, it wouldn't need to be deliberate, just sudden and unexpected.

AFAIK, control column deflection and control force aren't mandatory FDR parameters per Annex 6.
This was an early 1990s build aircraft - and as digital memory was getting cheaper the number of non-mandatory items on the DFDR really exploded in that time frame. Both a benefit and a curse when you were reviewing incident data - with so much data available it could make it a real challenge to sift the wheat from the chaff...

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Old 12th Mar 2019, 22:50
  #495 (permalink)  
 
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Originally Posted by tdracer View Post
This was an early 1990s build aircraft - and as digital memory was getting cheaper the number of non-mandatory items on the DFDR really exploded in that time frame. Both a benefit and a curse when you were reviewing incident data - with so much data available it could make it a real challenge to sift the wheat from the chaff...
Are you saying that control column deflection was in fact an FDR parameter for the accident flight?
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Old 12th Mar 2019, 23:12
  #496 (permalink)  
 
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Originally Posted by SMT Member View Post
Descending In IMC, receives sudden W/S warning. Throttles goes to the stops, aircraft pitches up. Spatially disorientated pilot notices airspeed not building, pushes control column forward and holds it until things 'start feeling right'. Realises what's going on, hauls back on column but too late.

Don't know, just an idea.
Pretty sure all wind shear warnings are inhibited at that altitude.
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Old 12th Mar 2019, 23:40
  #497 (permalink)  
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Originally Posted by DaveReidUK View Post
Are you saying that control column deflection was in fact an FDR parameter for the accident flight?
PMFJI, it could be a parameter, along with the force in pounds depending upon the data frame. The B737-400's -5 data frame has control column and control wheel position. This aircraft's data frame will likely have those parameters, and possibly also control column/wheel force in pounds.
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Old 12th Mar 2019, 23:41
  #498 (permalink)  
 
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Originally Posted by flyingchanges View Post
Pretty sure all wind shear warnings are inhibited at that altitude.
I think they are inhibited above 1500 feet AGL on the classic 767. Also, you wouldn't get an EGWPS alert at 6000 feet over East Texas. But like everybody else, I'm pulling at straws trying to think of why you would go to max thrust before the pitch over.

I suspect that the NTSB has a good guess between the CVR and FDR but need to be cagey in their public release of information until they have confirmation.

From today's NTSB update:

A cockpit voice recorder (CVR) group was convened and will complete a transcript of the entire event. The CVR transcript will be released when the public docket is opened.
Unfortunately, it is usually months before the public docket is opened in a major investigation.
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Old 13th Mar 2019, 00:07
  #499 (permalink)  
 
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Having worked in a bureaucracy, the most likely explanation is that someone accidentally posted a version of the press release that didn't include all the edits from the review process (and then corrected their mistake). It seems hard to believe that NTSB is both nimble enough to revise its press release in response to speculation on Twitter, and at the same time stupid enough to think that the revision would make things better.

It also seems hard to believe that those words would have made it into any version unless the FDR data showed column deflection and/or force. Maybe NTSB decided it should formally eliminate any other possible explanation for those readings before publishing the conclusion that there was actual control column input. Or it just didn't want to feed too much speculation ahead of the report (but accidentally did so anyway).
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Old 13th Mar 2019, 00:19
  #500 (permalink)  
 
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Column, elevator... Whatever the intended edited version went out, I think the Human Behavior team is very busy at this time.
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