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TU154 out of Sochi is missing.

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TU154 out of Sochi is missing.

Old 28th Dec 2016, 12:26
  #161 (permalink)  
 
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The BBC article is suggesting that the flaps did not retract in sync .. that "they are not moving together" ... although quite how they got to that conclusion from the CVR is not clear ...

As normal practice is to retract in stages, I would have thought the imbalance would have become obvious before it became fatal, by the time you have a bootfull of rudder and the stick hard over, you would not be calling for another stage of flap retraction, you'd be thinking "hmm, that does not seem to have gone well" ...
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Old 28th Dec 2016, 12:30
  #162 (permalink)  
 
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Sounds a bit like flap retraction instead of gear retraction, with predictable consequences.

There was a Io-co in the UK that had the same problem. The standard accelleration call was "FLAPS UP SPEED". A procedure that was utterly crasy, and I told them so. Well, after two aircraft staggered away with a lack of flaps at very low speed, the accelleration call was finally changed.

Basic rule of aviation .... if it can happen, it will happen. And you can bet your bottom dollar it will happen on the fourth flight at 03:00, when everyone is dogtired and half asleep. So try and make your procedures as buIIet-proof as possible. Unfortunately, some of these new-entrant airlines were run by beginners, who were always reinventing a very old wheel.
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Old 28th Dec 2016, 13:25
  #163 (permalink)  
 
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Asymmetric flap?
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Old 28th Dec 2016, 14:22
  #164 (permalink)  
 
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From russian "pprune" (forumavia.ru):
If the takeoff to be completed with flaps28 - they should be retracted with 2 steps: speed 300 km/h - set flaps15, after acceleration to 330 km/h - set flaps up.
According info leaks somebody in the cockpit told : "speed 300.... f*ck, flaps!!! "
That's why there is a version that one of pilots selected flaps from 28 to 0 inadvertently.
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Old 28th Dec 2016, 14:32
  #165 (permalink)  
 
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CVR transcript can be authentic, but a time stamping is missing. Flaps problem may arise some 1-2 min later after gears up.
IF ... big if ... the CVR is authentic, then unless edited it appears to contain no command to move the 'flaps'. So either it's all continuous, and the gear statement is associated to the 'flaps', or a 'flaps' problem occurred without them being commanded. The latter sounds unlikelier.
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Old 28th Dec 2016, 15:03
  #166 (permalink)  
 
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The BBC report looks credible and clearly refers to the FDR readout (NOT CVR), and clearly mentions "flaps not movng together". Sounds like flaps assymetry induced LOC.
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Old 28th Dec 2016, 15:13
  #167 (permalink)  
 
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Surely flap asymmetry would simply cause a flap lock-out?

It certainly sounds like a configuration error caused the accident, whether as the result of system failure or aircrew mis-selection. How are the slats and flaps 'automatically' interconnected? Are the slats still extended when the flaps move from 28 when 15 flap is selected?
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Old 28th Dec 2016, 16:18
  #168 (permalink)  
 
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Flap asymmetry can be a very big problem.

Recall the UA DC-10 at Chicago when significant items were damaged when the engine came off the pylon. And then there's the one I had in a Viper long ago.



In my case, the FBW flight controls helped me a lot! The assymetry brake sensor was outboard, and my failure was with the connection to the flap drive motor in the fuselage. The "brake" couldn't work because the flap was not connected to any control mechanism. Duh.

My understanding of the flap control surfaces on this plane is that they are independent from side-to-side. So as with my "problem", one side could fail and the other worked per normal.

At slow speed and with assymetrical flaps you could have a serious inpact on total lift for the plane and also have roll problems due to more lift on one wing than the other. My problem happened after I was above the minimum control speed so I mainly had a lot of drag and used all but 1 pound of stick authority to keep control( according to data recorder we had on early Vipers).

Unless those guys pushed forward right away and reduced AoA/pitch to gain speed, they were doomed.
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Old 28th Dec 2016, 16:27
  #169 (permalink)  
 
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I don't think it will take them long to confirm if it was either assymetric slat/flap or a configuration stall. I don't buy the smooth sea, dark night, high acceleration somatogravic illusion.
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Old 28th Dec 2016, 16:44
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The BBC report looks credible
No it's not

and clearly refers to the FDR readout (NOT CVR)
No CVR or FDR readout was officially announced yet. The BBC "report" is a mixed reprint of Life.ru and other Russian media and web forums, based on "expert" interviews, "source leaks" and wild guesses.
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Old 28th Dec 2016, 16:50
  #171 (permalink)  
 
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As far as I can filter info from noise, it was stall, caused by takeoff misconfiguration, but what was a source of it still unclear.
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Old 28th Dec 2016, 16:58
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Wing:



FDR



Engine

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Old 28th Dec 2016, 17:01
  #173 (permalink)  
 
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Main gear

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Old 28th Dec 2016, 17:01
  #174 (permalink)  
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Kulverstukas, do you know if this FDR's medium is digital (chips), optical or tape?
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Old 28th Dec 2016, 17:06
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Quote:
The BBC report looks credible
No it's not
...and repeat...
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Old 28th Dec 2016, 17:10
  #176 (permalink)  
 
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The question is who or what is the BBC's source? From previous experiences with accident reporting by the BBC I would wait for an official announcement by the authorities!
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Old 28th Dec 2016, 17:10
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Tape



CVR MARS-BM 70A-11 left, FDR MLP-14-5 right
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Old 28th Dec 2016, 17:13
  #178 (permalink)  
 
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BBC headline:

The main flight recorder from the Russian jet that crashed into the Black Sea on Sunday has revealed that faulty flaps were to blame, Russian media say.
So, the BBC are, by their own admission, only reporting what the Russian media has reported. Therefore, no credibility whatsoever!
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Old 28th Dec 2016, 17:26
  #179 (permalink)  
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Kulverstukas, many thanks!

One more item if I may - do we know what parameters and sample rates there are with this kind of an installation? I'm not expecting thousands of parameters as may be available on modern transports, but I'm wondering if it is more than we might see on B737-200/300/400 types, for example, (~80 to 250 parameters depending on data frame and legal requirements).
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Old 28th Dec 2016, 17:30
  #180 (permalink)  
 
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http://lms.aeroflot.ru/data/tu_154_systems/tm14.pdf

48 analog channels and 32 single events channels. 3 analog channels are 8Hz, rest are 2Hz.
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