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Emirates B777 gear collapse @ DXB?

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Emirates B777 gear collapse @ DXB?

Old 6th Aug 2016, 18:20
  #521 (permalink)  
 
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Can anyone tell me at what point the EECs go from approach to intermediate or minimum idle as all my FCOM says is "after touchdown"? If the engines had gone to a lower idle the difficulty could be greatly exacerbated.

It's standard Boeing design practice to hold the engines at approach idle for 5 seconds after the air/ground transition, although the specific implementation varies with the different aircraft models. The older aircraft (e.g. 747-400 and 767) do it with time delay relays, newer models do it in software.
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Old 6th Aug 2016, 18:50
  #522 (permalink)  
 
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Some points which haven't eben discussed

1. flap Setting seems to be 15! Why this??

2. the tail has traces from a tailstrike.

3. speedbrakes not extended!

there has To ne more than simple pilots error
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Old 6th Aug 2016, 19:07
  #523 (permalink)  
 
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1. Maybe the flaps only appear to be at 15.

2. Perhaps there was a tail strike.

3. Spoilers would not deploy if the gear were not down and conditions met.

4. Don't know of any generic malfunction that would lead to all the above.
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Old 6th Aug 2016, 19:37
  #524 (permalink)  
 
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I truly feel for the moderators, they must be sorely tempted to shut this thread down. Please think before you post.......treat your post like a rant to your boss....sleep on it, read it again in the morning and then send it if you think it makes sense.
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Old 6th Aug 2016, 20:10
  #525 (permalink)  
 
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Impressions based on available video and photo material:

A. Righthandwing top panel:
At one stage in the video’s there is a major explosion on the right hand wing side. A large dark object is seen flying/blasted away. Some suggested that this was an escape slide.

Looking at the present state of photo and video material, my impression is that it is far more likely that it is a significant ‘part’ of the ‘top panel’ of the righthand wing. This ‘part’ roughly running outward from the wing root in spanwisedirection upto the middle of the second slat right from the right-hand engine. Fuselage-lengthwise this ‘top panel part’ running roughly between rear and front spar. The outer slats probably not even ‘hit’ during the explosion. So all in all a very large ‘toppanel’ (meaning top skin(s) sections with stiffeners and other attached systems and structural materials).
From the photos you expect the panel tearing near the wing root and rotating up from that root with a ‘hinge’ line roughly running through the end of the second outer slat position. You can see an upward bent top panel edge, still attached to the‘outer’ wing, at that line.

On one of the photos taken from above you see a large top (black) section missing from the wing.
During the explosion you see the flames ‘following’ and ‘shielded by’ the dark object. Which I would not expect if it was an escape slide.

There is a photo of a large piece of flat panel lying topside down on the runway/taxiway area, with what may be yellow tape/hose draped round it. Striking that it is not covered in soot or burned.

B. Enginebreak away:

For this item the video material is incomplete. Of low quality and dynamic. And starts only when a crash situation was clear. But to try to figure out what happened ...with what we have ... the plane rotates around the right hand engine so to speak, after it broke away. This happened in such a manner that it cut fuellines and (partially) ruptured fuel tanks. With probably the fire running from the engine to that fuel pool. Fire in the engine is visible at the start of the break away video segments.

A+B =combining these two items:

If the initial fire started around the righthand engine, which was away from the centertank. And assuming that the center tanks content had been consumed first during the trip, giving them a more explosion prone gas/fuel mixture (at least compared to that of a fuel filled tank). Next, the fuel pool fire may have heated up that center tank volume from the outside, leading up to the explosion that we discussed under item A. This explosion (further) opening up the righthand center upper fuselage. Which would explain the fact that the right hand side fuselage shows far more damage than the left. While cargo holds appear to show minimal soot. And maybe also offer some explanation of why most slides were initially deployed on the right hand side at the start of the evacuation. And passengers later escaping via the left hand slide aft.

I am not familiar with the engine break away design scenario’s of the 777. But this case will surely be used to review them. I wonder if the sequence of events of this accident will turn out to be one of the 'foreseen' scenario's, either a design one or even a certification one.

Sorry for the long post.
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Old 6th Aug 2016, 20:15
  #526 (permalink)  

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AO283 excellent.
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Old 6th Aug 2016, 20:19
  #527 (permalink)  
 
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Heard from a former EK Pilot, this particular tail number was known as the "pig!"
(An old and heavy -300 with the -200 engines!)


Complete and utter drivel. Never heard that about any plane at EK. -200 engines, it would never get off ground.... Utter tosh.

SyB
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Old 6th Aug 2016, 21:02
  #528 (permalink)  
 
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Best post ever on PPRuNe or aviation forums in general
Originally Posted by fdr View Post
climb requirements are pretty simple.

14 cfr part 25.121(d) requires the plane to be able to achieve 2.1% gradient in the conditions, with a critical engine failed, with the gear retracted.

Part 25.119 covers landing climb, all engines operating. Gradient requirement of 3.2%. That is in landing config, e.g., f30, gear down. The sub para (a) is pertinent on some aircraft, (the pw4098 was one that could be a long time between wanting and getting, but well within the required periods).

The gradients for the aircraft cover therefore approach configuration engine out, and all engines in full landing configuration. That is rational and works well.

Any assumption that after some millions of hours of operating we suddenly get a plane that cannot achieve a gradient would have to assume some extenuating circumstance well outside of normal operations. High temps are an issue, the reported temp and local temp of an airmass that the aircraft passes by are different, but you will likely find that that is not a big issue in this case. Wind shear equates directly to a change in the cas as the energy state of the aircraft alters with a time domain delay due to inertia, either increasing it or reducing it depending on the sequence of encounter. In these conditions, again they would have to be rather severe to critically affect the energy state of the aircraft. Increasing tailwind, or reducing headwind result in loss of cas. Modest shear will alter the performance outcome from an expected outcome such as a pitch attitude that is selected, the flight path then is reduced where cas is lower than expected. That may seem pretty obvious, but when you rotate you are not necessarily looking at pertinent data, and routine standards evals show that the same is true for the pm case, what they are looking at during the change in flight path is not necessarily what you may expect. Bottom line, pitching up and assuming that the plane will achieve a certain performance is human nature, reinforced by the routine expectancy being matched by reinforcing outcomes, (we don't get surprises that often, fortunately).

On any day, proceduralizing of our processes in the cockpit act as much as a threat to the operation as an enhancement. How often is a checklist item answered without the actual condition being confirmed... "clear left/right!... Without anyone looking, standard callouts being made without the requisite action being taken that is supposed to be verified/reinforced by the callout. Sucks to be human, but then humans also can do things that computers cannot do, so it really sucks to be walk-on freight. You get what you pay for...

Emirates is a compliant airline; look at any iosa audit and you will find that in fact most are. (in fact, almost all are, and that should make one ponder for a moment, and then the moment will be lost in time). Emirates has a public image that is one of competence. Airlines are obliged to balance safety and economics, no matter what pr may say, that is not just the air transport industry, that is every human endeavour, in fact every system in nature that has a choice of actions. We are likely to find not very much was out of the ordinary here; we tend to forget due to the amazing reliability of the global air transport system that very flight involves an extraordinary confluence of things going right, with great demands for perfection. A failure can occur when a number of conditions are just sufficiently outside of normal to act together in concert to result in an unanticipated outcome. Such a failure mode comes from the reality of complex systems having potential for resonance to occur, where stochastic system behaviour of various inputs results in something that is outside of the expected occurring. Such a failure doesn't need active failures, it can occur with a number of within limit conditions just ending up at the wrong place at the wrong time. Sometimes, it just sucks. If that sounds depressing to people that may gain succour from linear or quasi linear causation, it need not be. It indicates that the most important thing we can have in operations is situational awareness, and that means, knowing when it likely to be compromised hints at how to get serious about maintaining system integrity. But, it is much easier to shoot the messenger, that cures the problem immediately, and everyone is satisfied that both justice, and system safety has been satisfied. Unfortunately, the world is not linear, nor quasi linear, and so a similar event will not be avoided.

Wonder how the emirates management will respond, insight or pavlovian responses.

If resonance appears a strange concept, one should consider their daily experience, or read up on complex systems failures as ladkin or hollnagel consider. Aircraft losses are brutal, so is a nuclear power station loss, and similar critical coupled systems.

Flight crew are not served well by rigid sops that end up affecting sa. Losing sa is just being human, yet our systems tend to belt the stuffing out of our crews for merely being so.

Never dull
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Old 6th Aug 2016, 21:10
  #529 (permalink)  
 
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Or stalled in to the ground

Either way, the crux of this fortunate (barring the fire fighter who died, may he RIP) was the wheels up decision. Not good. Alas some poor sod pushed the lever...
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Old 6th Aug 2016, 21:52
  #530 (permalink)  
 
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This typer of designRE AO283 POST 531 "
I am not familiar with the engine break away design scenario’s of the 777. But this case will surely be used to review them. I wonder if the sequence of events of this accident will turn out to be one of the 'foreseen' scenario's, either a design one or even a certification one.
SUGGEST you take a look at posts 260 thru 290 around page 14 re a short discussion and response re strut design parameters started by myself ( CONSO ) short version is the strut system is designed to fail such that engine pivots up over the wing to protect frontspar etc. Also dry bay on each side of strut assembly. Normally for a straight ahead landing failure or in air failure. What happens with side loads as shown by video becomes a bit more problamatical.

This type of design parameter has been standard for decades at least at Boeing

Last edited by CONSO; 6th Aug 2016 at 21:55. Reason: correct post number- added parameter comment
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Old 6th Aug 2016, 22:23
  #531 (permalink)  
 
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what conso said. The engine and pylon assembly is designed to come off on impact without compromising wing box/fuel tank integrity. by that I don't mean damage or leaks, but without catastrophic failure of the wing primary structure.

To my mind the first thing that needs to be ruled out as the cause of the "explosion" are the right MLG wheels and tyres, assuming the gear was still roughly somewhere between rear spar and LG beam after the aircraft stopped. They are a known explosion hazard and the fusible plugs may not have popped in time.
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Old 6th Aug 2016, 23:57
  #532 (permalink)  
 
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Originally Posted by Sheikh Your Bootie View Post
Heard from a former EK Pilot, this particular tail number was known as the "pig!"
(An old and heavy -300 with the -200 engines!)

Complete and utter drivel. Never heard that about any plane at EK. -200 engines, it would never get off ground.... Utter tosh.

SyB

Taken from FAA Certification Data Sheet
B777-200
2 Rolls-Royce Turbofan Model: RB211-Trent 875-17, RB211-Trent, 877-17, RB211-Trent 884-17, RB211-Trent 892-17, or RB211 Trent 892B-17, RB211 Trent 895-17


777-300
2 Rolls-Royce Turbofan Model: RB211-Trent 884-17, RB211-Trent 884B-17, or RB211-Trent 892-17
========================
777-31H 28680, 28687, 29062-29064, 29067, 29395-29397, 32699, 32700, 32702


A6-EMW Serial # 32700

Not so sure what to say more....
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Old 7th Aug 2016, 00:22
  #533 (permalink)  
 
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Looking at the video of the removal of the aircraft, it appears that the nose gear is not fully retracted (or extended for that matter). I know that aircraft with gear doors on the main gear suffer from increased drag during the gear cycle, so perhaps they were climbing when the gear was selected up & the extra drag, coupled with other factors, caused it to lose altitude & settle back onto the runway.


If the PF was increasing attitude in order to try & prevent the altitude loss, the aircraft may have struck tail first, explaining the damage to the underside of the rear fuselage. The aircraft would then rapidly pitch nose down. If the right wing was slightly down, then most of this force would be brought to bear on the right engine nacelle & may have exceeded the design strength of the engine mounts & pylon, causing the right engine to separate, different to what happened with the BA & LOT crashes.


Lots of speculation. The final report, if we ever get to see it, will make for interesting reading.
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Old 7th Aug 2016, 01:40
  #534 (permalink)  
 
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In the EVAC video I distinctly heard a PA call - "CABIN CREW.......unintelligible".

Presuming the video was only started after some time had passed following the stop (everybody was already in the aisles and grabbing bags) it strikes me as odd that the F/D crew would wait so long to make the PA if indeed it was the F/D crew. If it was the cabin crew making the PA then it seems even more odd. I'm especially bothered that I did not hear any non PA cabin crew voices until well into the video, very near the end. Perhaps those voices were in fact there but not in English so I missed them? If they were only communicating in English then that obviously is a problem in itself , not to mention that those voices should have been heard loud and clear much sooner.

Last edited by nnc0; 7th Aug 2016 at 01:50.
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Old 7th Aug 2016, 03:32
  #535 (permalink)  
 
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I once did a go-round where the moment I pushed the TOGA switches the Autothrottle dropped out. You then have to firewall the thrust levers manually. Possible scenario here?
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Old 7th Aug 2016, 04:59
  #536 (permalink)  
 
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Looking at the video of the removal of the aircraft, it appears that the nose gear is not fully retracted (or extended for that matter)
I asked myself whether this earlier photo suggested that the nose gear door was open.

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Old 7th Aug 2016, 08:09
  #537 (permalink)  
 
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I was taught from about day one in the Sim to know how far forward the thrust levers were at TOGA on the 777. It was about Arms length from memory and anytime I needed to select TOGA I always made sure my Arm was nearly straight.

If the Thrust levers weren't moving forward quick enough they got a big shove.......

Still anything can happen when the shit hits the fan and humans do funny things under stress when tunnel vision sets in.......
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Old 7th Aug 2016, 08:26
  #538 (permalink)  
 
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I apologise if this has been mentioned earlier, but it might be hidden in 28 pages.
There was speculation about a late ATC call for GA; there was speculation about a GA after a bounced landing; there was speculation about a late WS induced GA. Has the real reason for what appears to be an attempted GA been established?
Much of the debate seems to be about why/what went wrong during such an attempt.
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Old 7th Aug 2016, 09:16
  #539 (permalink)  

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I apologise if this has been mentioned earlier, but it might be hidden in 28 pages.
There was speculation about a late ATC call for GA; there was speculation about a GA after a bounced landing; there was speculation about a late WS induced GA. Has the real reason for what appears to be an attempted GA been established?
Much of the debate seems to be about why/what went wrong during such an attempt.
Assuming the eventual report is factual then we will learn the sequence of events and the reasons for the crash. Until then all the postings here, the majority of them complete nonsense, are utterly pointless.

Quite why so many people wish to contribute their pet theory, often identical to an earlier poster's theory, is beyond me.

I currently teach both B777 and B787 conversion courses. I have a thorough knowledge of how the aircraft behave and have observed many interesting pilot actions in given situations but what purpose would it serve for me to try and guess what happened?

The moderators are doing a good job removing the majority of the more outlandish and pointless rubbish.
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Old 7th Aug 2016, 09:46
  #540 (permalink)  
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B777 TO/GA Switch op's.

1. GA mode is inhibited on ground
2. TO mode is inhibited in the air (and >50 knots on ground)
3. Speed brakes, if armed, require air ground inputs and MLG tilt press inputs to deploy - Tilt pressure is so a "bounce" won't deploy them.
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