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TU154 out of Sochi is missing.

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TU154 out of Sochi is missing.

Old 29th Dec 2016, 11:18
  #201 (permalink)  
 
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for some reason they were unable to build up speed and altitude , either the engines did not develop rated thrust or they had massive drag ( e.g spoilers , speedbrake extended by malfunction ) , maybe also severe overloading or extreme wrong cg . i believe they retracted flaps as quick as possible to reduce drag intentionally. i believe the word "flaps" was a last desperate call when the captain realized he is down to a speed where he will stall in clean config for sure to keep control for at least a ditching and not crashing into water. the next second they stalled and crashed. with a flap retraction right after liftoff and a resulting stall they would not make 70 seconds airborne time.

heavy cargo shifted back forcing such an aft cg he ran out of elevator authority ?
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Old 29th Dec 2016, 11:49
  #202 (permalink)  
 
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aerobat77, have you ever flown a swept wing airliner?

If high devices are retracted below the +1G buffet boundary, there will only ever be one result.

Last edited by BEagle; 29th Dec 2016 at 15:35.
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Old 29th Dec 2016, 17:07
  #203 (permalink)  
 
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and this result would have happen at the end of the runway in this scenario, not 70 seconds later...
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Old 29th Dec 2016, 18:02
  #204 (permalink)  
 
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We don't know that the aircraft was airborne for 70 seconds.

It's quite possible that the reported 70s flight duration was measured from the start of roll. In that case much, if not most, of it would be the takeoff ground run.
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Old 29th Dec 2016, 18:09
  #205 (permalink)  
 
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aerobat77, have you ever flown a swept wing airliner?

If high devices are retracted below the +1G buffet boundary, there will only ever be one result.
Are you eluding to a stall or a crash there Beagle? I'm sure a configuration stall or a 'premature high-lift device retraction' has occurred many times. If you're accelerating enough you may well get away with it, which is why they don't all end in a Staines-Trident type event. In addition, if you spot the 'inadvertent' retraction in time and reverse it, you'll fly away. Indeed G-ARPI was not doomed the instant the leading edge droops were retracted. Had the selection been reversed in time then they would have safely flown away.

And this result would happen at the end of the runway in this scenario, not 70 seconds later...
Well not necessarily. I'm not familiar with the TU154 slat/flap system, but certainly on other types with a combined slat/flap lever you may well be accelerating quickly enough not to stall until the slats start retracting. That will often be after the flaps have fully retracted and so perhaps 20 seconds or so after the initial slat/flap lever operation. If the call to raise the 'gear' was quite leisurely then an inadvertent slat/flap retraction could well result in an impact only a mile or so from the airfield.
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Old 29th Dec 2016, 18:20
  #206 (permalink)  
 
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70 seconds airborne, max height of 250m and 10 seconds of catastrophic situation don't add up. If you deduce a questimated takeoff roll it makes much more sense.
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Old 29th Dec 2016, 18:44
  #207 (permalink)  
 
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Let's make a simple calculation.
Rw length is 2890 meters - run +air distance =45 sec
Departure End Runway to coastline - apprx 1500 m = 18 sec
The debris were found 1500 meters from coastline = 10-12 sec more
Here are 70 sec
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Old 29th Dec 2016, 18:56
  #208 (permalink)  
 
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https://www.youtube.com/watch?v=buQvb0CVuSA

take-off, gear, flaps..

https://www.youtube.com/watch?v=8qTiR7hraf0

https://www.youtube.com/watch?v=IkExVUJ0ciI

50 sec from rolling to gear retraction
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Old 29th Dec 2016, 19:35
  #209 (permalink)  
 
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In the last video 60 seconds to 250 meters seems spot on. No flap retraction of course in neither video at that point. Surely there are many variables and different procedures. Equal or better TO performance than in the videos, if flap retraction speed was achieved.
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Old 29th Dec 2016, 21:34
  #210 (permalink)  
 
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Flap retraction on that Alrosa video is absolutely fine, - have flown on TU loads of times.
The a/c was probably MTOW too in view of the useage.
I think it's the last 2, flying, and have seen them sitting outside DME a few times on arrival.
(lots of Russian airports currently look like huge scrapyards).

About 40secs to rotate from standing (longer than a typical A320/737) flaps retract at about 70 secs....so what's the story?
Looks perfectly normal.
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Old 29th Dec 2016, 21:48
  #211 (permalink)  
 
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Originally Posted by up_down_n_out View Post
About 40secs to rotate from standing (longer than a typical A320/737) flaps retract at about 70 secs....so what's the story?
Looks perfectly normal.
As alluded to by a previous poster, Google "Papa India" if you want to understand why flaps aren't necessarily the whole story.
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Old 29th Dec 2016, 21:54
  #212 (permalink)  
 
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Anyone who is old enough would remember the media frenzy on that day.
The M4 wasn't that old either.

Pretty well everyone knows what happened, but here an experienced crew, well maintained a/c low hrs, an excellent safety record, good weather etc....
Doesn't add up.
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Old 30th Dec 2016, 04:22
  #213 (permalink)  
 
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Earlier post showed the " not ready for T/O" config warning.. Wondering, is it possible for it to test OK but not function properly? Never flown TU, so I'm not familiar with their procedures in that regard. Wondering perhaps if this aircraft might not have been configured in the first place... and perhaps the warning systems weren't functioning properly. It might explain the "flaps" comment previous pages if, say, they reached up to raise the gear and saw the flap lever incorrectly positioned....
I'm wondering if the flight profile here might be similar to the Northwest DC9 in Romulus Michigan...
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Old 30th Dec 2016, 10:56
  #214 (permalink)  
 
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70 seconds duration illustrated here.

1500m impact location from shore.

6.800m from the beginning of the runway requires average speed of 350kph to cover the distance in 70 seconds which means that a/c shouldn't have a problem with lack of speed considering zero velocity at the beginning of the take off run.

4300m from runway threshold would require app. 220kph average speed which seems much more applicable for the stall scenario. I conclude we talk about 70 seconds time when airborne excluding t/o run.

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Old 30th Dec 2016, 11:04
  #215 (permalink)  
 
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Quote:
"4300m from runway threshold would require app. 220kph average speed which seems much more applicable for the stall scenario. I conclude we talk about 70 seconds time when airborne excluding t/o run."

Thanks Pali. But 220 kph is only about 110 kt (ground speed). Not sure that would be sustainable as an average from airborne, assuming little headwind. I don't know the Tu 154, but I imagine the Vr would have been considerably greater than that?

Last edited by Chris Scott; 30th Dec 2016 at 11:15. Reason: Error
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Old 30th Dec 2016, 11:13
  #216 (permalink)  

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You're looking at a double failure there. Firstly the crew not configuring properly, then the warning not working. Unlikely IMO
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Old 30th Dec 2016, 11:37
  #217 (permalink)  
 
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It is safe to assume that plane was not on the runway until the last meter. Also, military pilots are tend to execute much more aggressive take-off procedures by the way.
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Old 30th Dec 2016, 13:23
  #218 (permalink)  
 
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Quote:
"Also, military pilots are tend to execute much more aggressive take-off procedures by the way."

Fascinating. Please tell us more...
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Old 30th Dec 2016, 13:59
  #219 (permalink)  
 
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Well this is part of the training. When you operating in combat zone the normal procedure is to go as high as possible as fast as possible. Sure, you don't have the freedom to barrel roll the a-320 but the past always infect the present. Actually, the plane was heading to Syria, the exact place where you will have all chances to encounter some rather unpleasant manpad experience. I am kinda sure the captain mindset was already "switched" to Latakia take-off and landing.
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Old 30th Dec 2016, 14:09
  #220 (permalink)  
 
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Originally Posted by PashaF View Post
Well this is part of the training. When you operating in combat zone the normal procedure is to go as high as possible as fast as possible.
But we already know that the maximum height achieved was only 250 m (830 ft).
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