TU154 out of Sochi is missing.
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It's military, so no public acess to investigation papers.
Except this short notice: https://ria.ru/inquest/20110513/374115628.html
And this pathetic article (summarized rumors, leaks and some forum discussions): Tu-154
Translate with Google.
In short, there was some wrong wires connection at EFCS which cause inversion of pitch and roll compensation signals.
PS: A bit reminds this one: https://en.wikipedia.org/wiki/China_...es_Flight_2303 and this: https://ru.wikipedia.org/wiki/%D0%9A...86%D0%BA%D0%B5
Except this short notice: https://ria.ru/inquest/20110513/374115628.html
And this pathetic article (summarized rumors, leaks and some forum discussions): Tu-154
Translate with Google.
In short, there was some wrong wires connection at EFCS which cause inversion of pitch and roll compensation signals.
PS: A bit reminds this one: https://en.wikipedia.org/wiki/China_...es_Flight_2303 and this: https://ru.wikipedia.org/wiki/%D0%9A...86%D0%BA%D0%B5
Thanks for those links, Kulverstukas. (The Google translations are hilarious...)
Regarding the videoed dutch-roll incident, you mention crossed-wiring in the EFCS. We can presumably rule-out that being done at Sochi.
Re EFCS, I think this aircraft design predates fly-by-wire flight control systems, so we are simply talking about a dedicated yaw-damper system. Most if not all western swept-wing airliners have had yaw dampers - certainly since the 1960s. No doubt some need them more than others. The anhedral of the Tu-154 is said to reduce the tendency to dutch-roll, but it would be interesting to know how the aircraft behaves in the absence of yaw damping.
Regarding the videoed dutch-roll incident, you mention crossed-wiring in the EFCS. We can presumably rule-out that being done at Sochi.
Re EFCS, I think this aircraft design predates fly-by-wire flight control systems, so we are simply talking about a dedicated yaw-damper system. Most if not all western swept-wing airliners have had yaw dampers - certainly since the 1960s. No doubt some need them more than others. The anhedral of the Tu-154 is said to reduce the tendency to dutch-roll, but it would be interesting to know how the aircraft behaves in the absence of yaw damping.
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Originally Posted by Kulverstukas
In short, there was some wrong wires connection at EFCS which cause inversion of pitch and roll compensation signals.
Correct connection:
http://cdn.fishki.net/upload/post/20...29291/5_10.jpg
Actual connection at RA-85563:
http://cdn.fishki.net/upload/post/20...29291/4_11.jpg
"Mildly" Eccentric Stardriver
There are pictures of wrong terminal connection available on the internet.
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I think he means color codes. I saw same way of engineering at color coding power connections for submersible Grundfos pumps, leading to same (albeit less deadly) results.
Back to Tu-154, if I recall correctly, it's power wiring of damping motors and they must work in antiphase to input signals, so they used cheap solution. IIRC there was a Tupolev's bulletin to remark them after this "dance".
Back to Tu-154, if I recall correctly, it's power wiring of damping motors and they must work in antiphase to input signals, so they used cheap solution. IIRC there was a Tupolev's bulletin to remark them after this "dance".
"Mildly" Eccentric Stardriver
Thanks, Kulverstukas. Yes, the colours "connect the green terminal to the red terminal, and the red terminal to the green one." Somebody a bit tired, or rushed, and we can see the result.
I still don't understand this fully. Did the transposition of the wiring also stop the crew from simply turning the yaw damper off?
Is there an ON/OFF switch? Failing that, is there a CB?
Is there an ON/OFF switch? Failing that, is there a CB?
Thanks K,
So that's the starboard-side and fuselage wreckage laid out within a rough outline of the aircraft. It would be interesting to see what they've got on the port side.
So that's the starboard-side and fuselage wreckage laid out within a rough outline of the aircraft. It would be interesting to see what they've got on the port side.
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Concerning dancing plane - the plane was stored for almost ten years. My experiences allow me to imagine a scenario that from time to time somebody went to "borrow" spare parts from the plane. They could return it to the cannibalised machine after original part came. It is very dangerous moment, non standard operation, without checks.
The colour code surely has its logic for electric engineers.
The colour code surely has its logic for electric engineers.
Last edited by Karel_x; 29th Jan 2017 at 10:30.
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The colour code surely has its logic for electric engineers.
Speaking from experience, cannibalization of an aircraft greatly increases the risk of maintenance error, even when a serious attempt is made to control the resulting maintenance.
Once an aircraft is perceived to be a wheeled parts bin, it is easy to create an attitude that permits uncontrolled removals of equipment thus creating colorful experiences for the crews flying the aircraft when an attempt is made to return it to service.
Hi Machinbird,
Unfortunately, we still have no information on the dutch-rolling characteristics of the Tu-154 with the yaw damper system simply turned off. I was hoping a Tu-154 pilot might comment.
Unfortunately, we still have no information on the dutch-rolling characteristics of the Tu-154 with the yaw damper system simply turned off. I was hoping a Tu-154 pilot might comment.
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There is a month old report that appears to hint at a specific failure that we have not been discussing:
Preliminary Findings Point to Flap Problem in Tu-154 Crash | Defense News: Aviation International News
There is a background statement that may be relevant:
So what would be the result of overspeeding extended but deactivated trailing edge flaps? Could that be a reason the aircraft did not climb significantly?
Preliminary Findings Point to Flap Problem in Tu-154 Crash | Defense News: Aviation International News
There is a background statement that may be relevant:
An SPZ-1A sensor device is used to monitor whether the flaps move symmetrically; if they do not, it de-activates the hydraulic actuator and issues a warning to the crew to assume manual control. The Tu-154B-2 flight manual and other documents prescribe using an electrically-controlled stabilizer and control yoke to offset the diving force that the flaps generate should they have not retracted. Crews are required to perform simulator training to deal with such a situation. If the failure of the flaps retraction mechanism is discovered in a timely manner, the pilots are instructed to land at the nearest airfield while maintaining a relatively low speed. They are also instructed to keep the throttles at a low setting so that the engine thrust does not further complicate the issue of aircraft stability and controllability.
Hi Machinbird,
To be fair, I think other posters have previously speculated on both slat/flap asymmetry and premature retraction of slats and/or flaps.
I'd be interested to hear your opinion, but it seems to me that the paragraph you quote was written by someone with limited knowledge - probably a journalist doing his/her best. It's partly incoherent.
However, I'm guessing that, in the event the crew detects asymmetry during retraction, there may be a way of freezing the surfaces in their present position. That could explain the extra switches on the overhead panel shown in this photo posted by Kulverstukas:
http://www.pprune.org/rumours-news/5...ml#post9621956
I refer to the switches just to the left of the L/G lever. Perhaps Kulverstukas will comment.
To take an admittedly distant example, and IIRC, the B707 has override switches for the inner and outer T/E flaps that freeze the flaps hydraulically, but enable them to be moved electrically.
Obviously IAS has to be limited if slats and/or flaps remain partially extended. That in itself should not compromise initial climb performance, but the stated necessity to limit thrust certainly would.
To be fair, I think other posters have previously speculated on both slat/flap asymmetry and premature retraction of slats and/or flaps.
I'd be interested to hear your opinion, but it seems to me that the paragraph you quote was written by someone with limited knowledge - probably a journalist doing his/her best. It's partly incoherent.
However, I'm guessing that, in the event the crew detects asymmetry during retraction, there may be a way of freezing the surfaces in their present position. That could explain the extra switches on the overhead panel shown in this photo posted by Kulverstukas:
http://www.pprune.org/rumours-news/5...ml#post9621956
I refer to the switches just to the left of the L/G lever. Perhaps Kulverstukas will comment.
To take an admittedly distant example, and IIRC, the B707 has override switches for the inner and outer T/E flaps that freeze the flaps hydraulically, but enable them to be moved electrically.
Obviously IAS has to be limited if slats and/or flaps remain partially extended. That in itself should not compromise initial climb performance, but the stated necessity to limit thrust certainly would.
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Chris, switch left of gears lever (partly crossed by red circle) is auto/manual/off switch for flaps. Far left cluster is landing lights.
@Machinbird, figures from this article (like 500 kmh) were dismissed later by officials. Also last joint report from IAC-Defence commission states that there was no malfunctions found at flight data.
@Machinbird, figures from this article (like 500 kmh) were dismissed later by officials. Also last joint report from IAC-Defence commission states that there was no malfunctions found at flight data.
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Originally Posted by Chris Scott
Hi Machinbird,
...However, I'm guessing that, in the event the crew detects asymmetry during retraction, there may be a way of freezing the surfaces in their present position. That could explain the extra switches on the overhead panel shown in this photo posted by Kulverstukas...
...However, I'm guessing that, in the event the crew detects asymmetry during retraction, there may be a way of freezing the surfaces in their present position. That could explain the extra switches on the overhead panel shown in this photo posted by Kulverstukas...
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CVR and FDR readouts doesn't help much with investigation of the accident. Defence ministry doesn't agreed yet with version about crew error (particularly flaps instead of gears retraction) as the case of crash. MAK and Central Aerohydrodynamic Institute (TSAGI) will make mathematical model of the flight, which will help calculate two still unknown figures - TOW and centering, source told "Kommersant" newspaper.
Last edited by Kulverstukas; 9th Feb 2017 at 08:25.
