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Atlas Air 767 down/Texas

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Atlas Air 767 down/Texas

Old 26th Mar 2019, 00:47
  #741 (permalink)  
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Originally Posted by Old Boeing Driver View Post
Regarding this GA button issue. From what I have read here, the button is only armed when flaps are not "0"

I assume that selection of flaps 1 causes the LED's to extend.

If that is so, surely they would have been blown off the airplane by the time it reached 425 knots going down.

However the NTSB said they found a very small debris field and there has neen no mention of parts and pieces being found elsewhere.
RA <2500 Feet
Flaps out of "up"
Glide slope capture.
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Old 26th Mar 2019, 01:21
  #742 (permalink)  
 
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Originally Posted by 568 View Post
RA <2500 Feet
Flaps out of "up"
Glide slope capture.
If that is the case, then the GA button would have done nothing at 6,000 feet and no GS capture even if the flaps were not "0".

Thanks for the info.
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Old 26th Mar 2019, 01:37
  #743 (permalink)  
 
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Originally Posted by Old Boeing Driver View Post
If that is the case, then the GA button would have done nothing at 6,000 feet and no GS capture even if the flaps were not "0".

Thanks for the info.
It's not particularly uncommon for RA to give temporary false readings due to reflections off of clouds.

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Old 26th Mar 2019, 01:44
  #744 (permalink)  
 
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Originally Posted by tdracer View Post
It's not particularly uncommon for RA to give temporary false readings due to reflections off of clouds.
I'll take your word for the RA part, although I have never seen that.

But, what about the GS capture part?
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Old 26th Mar 2019, 02:03
  #745 (permalink)  
 
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Originally Posted by megan View Post
The Northwest Boeing 720 accident I mentioned earlier they reached -2.8
Actually the CAB accident report said that the negative acceleration increased to a mean value of about - 2.8 g so the peak before the aircraft broke up may have been even higher.




https://en.wikisource.org/w/index.ph...705.pdf&page=4

Here are FDR plots from NW705 as published in the CAB report:



Looking at the plots, maybe the -2.8 g number came from the average of the last two data points on the coarse foil technology FDR record.
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Old 26th Mar 2019, 02:30
  #746 (permalink)  
 
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Their indicated airspeed to reach those negative G values were in excess of 400 knots. Not possible to get anywhere near those numbers at 210 to 230 knots. The first generation jets were also stronger and had higher VNE limits. We regularly cruised the 727 at 380 knots IAS at 16,000 feet on shuttle flights. VNE was 405. The A330 has a VNE around 330 knots and the 767 about 355.
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Old 26th Mar 2019, 03:07
  #747 (permalink)  
 
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Originally Posted by Sailvi767 View Post
Their indicated airspeed to reach those negative G values were in excess of 400 knots. Not possible to get anywhere near those numbers at 210 to 230 knots.


From the NTSB Investigative Update on March 12, 2019:

FDR, radar, and ADS-B data indicated that the airplane entered a rapid descent on a heading of 270°, reaching an airspeed of about 430 knots.


https://www.ntsb.gov/investigations/Pages/DCA19MA086.aspx
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Old 26th Mar 2019, 08:43
  #748 (permalink)  
 
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Originally Posted by Airbubba View Post
From the NTSB Investigative Update on March 12, 2019:
https://www.ntsb.gov/investigations/Pages/DCA19MA086.aspx
Indeed. But that would be towards the end after they descended at steep angle and where they started pulling positive g's. I wouldn't be surprised to see >+4g somewhere in the readouts. The alleged -4g would have been at the beginning of the event. And that is where they were at ~230kts.

In the trace of the 720 accident you can see that at 220kts it produced ~ -2g, increasing to -2.8g @ ~280kts. The 720 had a ~20 - 25% lower wing loading than the 767, so should be able to produce ~25 - 30% more g at the same speed (especially in negative direction where no flaps/slats and tricked- out profiles will help).

When we extrapolate this data from the 720 accident we still end up with something around -2 to -2.5g maximum. We'll see the exact figures once the traces are published.
But I would expect something around -2g and +4 - 4.5g as maximum values.
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Old 26th Mar 2019, 15:56
  #749 (permalink)  
 
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Originally Posted by Airbubba View Post
Actually the CAB accident report said that the negative acceleration increased to a mean value of about - 2.8 g so the peak before the aircraft broke up may have been even higher.
Originally Posted by Sailvi767 View Post
Their indicated airspeed to reach those negative G values were in excess of 400 knots. Not possible to get anywhere near those numbers at 210 to 230 knots.
Originally Posted by henra View Post
In the trace of the 720 accident you can see that at 220kts it produced ~ -2g, increasing to -2.8g @ ~280kts.
One of you may be right, I'm not so sure that wing loading at max gross weight is what determines the negative g capability of an airliner. The -4 g claim may indeed be from a typo in a forum posting.

It looks to me like the Atlas 767 must have been very light to climb to FL400 immediately over the Gulf of Mexico.

Freighters continue to crash at a significantly higher rate than passenger planes at U.S. carriers as we have often observed here over the years.

There are a lot of B-763's still flying, I would think that if there was an early indication of a mechanical failure in this Atlas mishap, the NTSB would say something by now.

Last edited by Airbubba; 27th Mar 2019 at 00:47.
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Old 26th Mar 2019, 22:40
  #750 (permalink)  
 
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sudden updrafte, attempt to hold altitude..( vs attitude), hold that column forward...a bit longer than necessary
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Old 27th Mar 2019, 00:31
  #751 (permalink)  
 
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Originally Posted by Old Boeing Driver View Post
If that is the case, then the GA button would have done nothing at 6,000 feet and no GS capture even if the flaps were not "0".

Thanks for the info.
The maintenance manual and my 767 engineering training notes show no reference to the radio altimeters. Also, the logic for flaps and G/S capture is "or", not "and".

Most references show "flaps out of up" (although I do have one reference which says flaps >1).
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Old 27th Mar 2019, 01:12
  #752 (permalink)  
 
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Originally Posted by Airbubba View Post
One of you may be right, I'm not so sure that wing loading at max gross weight is what determines the negative g capability of an airliner. The -4 g claim may indeed be from a typo in a forum posting.

It looks to me like the Atlas 767 must have been very light to climb to FL400 immediately over the Gulf of Mexico.

Freighters continue to crash at a significantly higher rate than passenger planes at U.S. carriers as we have often observed here over the years.

There are a lot of B-763's still flying, I would think that if there was an early indication of a mechanical failure in this Atlas mishap, the NTSB would say something by now.

Yep, cargo drivers are forced to work longer and harder than the pax ones cause the FAA had the guts to treat cargo pilots as less "precious" . Absolutely astounding that they were allowed to differentiate....
And Amazon trying to push its shipping cost down by "operating" cargo ac from cheap labor holdings will just raise the chance for another crash with a loaded cargo plane full with dangerous goods, into a densely populated area.......corporate American greed has taken air safety hostage, Boeing, FAA, cheap cargo operators etc

Sometimes wondered when rolling down rwy 09 MIA, on our B747-4 cargo fully loaded with dangerous goods, and downtown MIA just beyond the rwy.....
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Old 27th Mar 2019, 03:19
  #753 (permalink)  
 
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Originally Posted by ironbutt57 View Post
sudden updrafte, attempt to hold altitude..( vs attitude), hold that column forward...a bit longer than necessary
Your observation there pointed my brain to the SFO crash of the 777 a few years back and some discussions on contributing factors.
Granted, this is a 767.
Is there a possible link to FLCH (or similar feature in 767), or, was this flight not close enough to IAH for that feature to be a contributing factor?
Reference article and discussion
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Old 27th Mar 2019, 06:17
  #754 (permalink)  
 
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Originally Posted by NSEU View Post
The maintenance manual and my 767 engineering training notes show no reference to the radio altimeters. Also, the logic for flaps and G/S capture is "or", not "and".

Most references show "flaps out of up" (although I do have one reference which says flaps >1).
The Flap/Slat Control Units on the 767 are relatively crude by current standards (not surprising - the basic design being nearly 40 years old). They put out analog discretes for 'flaps not stowed' - true anytime the flaps are not fully 'up', and 'flaps in landing' - true when flaps are ~23 degrees or greater (there may well be others - those are the ones that get used by the propulsion systems) - as well as digital outputs for use by systems such as EICAS. If anyone cares, on the engine side 'flaps not stowed' turns on continuous ignition, 'flaps in landing' selects approach idle - both via analog circuits (on newer aircraft this all gets done digitally).
There are two FSCU - Left and Right. Not sure about other systems, but the engines use left to left and right to right - so an FSCU failure only effects one engine.

IMHO the inadvertent TOGA selection is feasible, but this all remains conjecture until the NTSB releases something official.
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Old 27th Mar 2019, 11:26
  #755 (permalink)  
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Are the control cables rerouted / pullies repositioned on this conversion as in the -200 IAI/Bedek conversions?
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Old 27th Mar 2019, 22:45
  #756 (permalink)  
 
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Originally Posted by tdracer View Post
The Flap/Slat Control Units on the 767 are relatively crude by current standards (not surprising - the basic design being nearly 40 years old). They put out analog discretes for 'flaps not stowed' - true anytime the flaps are not fully 'up', and 'flaps in landing' - true when flaps are ~23 degrees or greater (there may well be others - those are the ones that get used by the propulsion systems) - as well as digital outputs for use by systems such as EICAS.
There are also FSPM's (Flap/Slat Position Modules) providing data directly to the AFDS & TMS, including position, not just (flaps out of up, etc) discretes. The leading edge flap position indication system also send signals to the PSEU (Proximity Switch Electronics Unit) for use with other systems. It's difficult to know which box does what.

Regarding your comment...

If anyone cares, on the engine side 'flaps not stowed' turns on continuous ignition.
Wiring schematic 74-31-01 shows an input into the ignition system from the Proximity Switch Electronics Unit (with a gate marked "SLATS RETracted"). However, the flight idle signal definitely comes from the FSEU.

There are also some lesser-known microswitches on the flap lever itself (at 1 unit) which input into the Thrust Management Computer and Flight Control Computers.

These switches are actuated in the flaps 1 detent position.
When actuated, the thrust management computer estimates the slats
moving to the flaps 1 position linearly in 5 seconds.
My training notes use this terminology in relation to GA Thrust Limit Mode:

The thrust limit mode transitions to GA when:
1) TO/GA is pressed on the TMSP (i.e. MCP) in the air
2) In air and the thrust limit mode is not in TO and the FCC signals GS Capture.
3) In the air and the thrust limit mode is not in T/O and flaps transition from zero to one.

The thrust limit mode will be locked in GA for flaps greater than 23.
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Old 28th Mar 2019, 07:41
  #757 (permalink)  
 
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Originally Posted by Havingwings4ever View Post
Sometimes wondered when rolling down rwy 09 MIA, on our B747-4 cargo fully loaded with dangerous goods, and downtown MIA just beyond the rwy.....

I would imagine the conflagration from a fully fuelled B747 would overwhelm most dangerous goods being carried.

Last edited by Lord Farringdon; 29th Mar 2019 at 08:54. Reason: Correct quote attribution
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Old 28th Mar 2019, 13:00
  #758 (permalink)  
 
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Originally Posted by Lord Farringdon View Post
I would imagine the conflagration from a fully fuelled B747 would overwhelm most dangerous goods being carried.
No doubt about that.
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Old 28th Mar 2019, 18:11
  #759 (permalink)  
 
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Originally Posted by Lord Farringdon View Post
I would imagine the conflagration from a fully fuelled B747 would overwhelm most dangerous goods being carried.
Interesting that you edited to 'correct quote' - when I most certainly did not post what's quoted (hint, it was Havingwings4ever)
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Old 28th Mar 2019, 22:29
  #760 (permalink)  
 
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Originally Posted by Lord Farringdon View Post
I would imagine the conflagration from a fully fuelled B747 would overwhelm most dangerous goods being carried.
OTOH, the dangerous goods could cause a conflagration that would not have otherwise occurred, e.g., UPS 6 Dubai, and Asiana 991 in the Sea of Japan...
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