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Turkish airliner crashes at Schiphol

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Turkish airliner crashes at Schiphol

Old 26th Feb 2009, 11:32
  #341 (permalink)  
 
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There are lots of speculations (and that is normal) but also a lot of untruths which can easily be disproved.

This crash landing was relatively soft. If an aircraft stalls only a very few feets above the ground, it disintegrates completly, normaly stalling first over the wings, it falls into a spiral and the wing impacts first. This is clearly not the case.

It is therefor no stall, it just landed into soft ground. You can also easily determine from the traces of debries that it had a relatively long ground "roll" distance of several hundreds of meters.

Problem is just that an aircraft like this cannot support a landing into soft ground: first the gear collapses and gets sheared off, then the engines, then the rest of the lower body parts.

If there would have been a stall, most probably nobody would have survived.

I want to reiterate (as in the Hudson River thread) that Airbus has somewhat some advantages over a 737 in this crash scenario because with its fly-by-wire suit it is much easier to be controlled close to ground and stall speed. What saved all lives in NYC may have cost 9 in AMS. Also BA's 777 accident in LHR might have profited from its speed control regime.

Dani
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Old 26th Feb 2009, 11:40
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If im correct then I believe the 777 is FBW but even so this is not relevent.

As to the comparison of the Hudson incident and this one Im not totally convinced that they can be compared due to the circumstances.

Two different stages of flight, two different configurations, two different aircraft and more importantly two different surfaces on which they landed.

With regards to the stall situation, I believe it has already been stated that the impact is regarded to be at relatively low velocity and there for a SHORT ground run. As for spinnig, with full flap and LED's deployed I believe the spin is highly improbable.

N
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Old 26th Feb 2009, 11:48
  #343 (permalink)  

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i couldn't find this although it may have been posted from the mode S info. At what distance from touchdown did the flight intercept the ILS and at what angle, height and IAS?
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Old 26th Feb 2009, 11:51
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For those who find the 'rumour' nature of this website distasteful, you would be better viewing elsewhere. This is a rumour website and that is therefore what you get!

There is an interesting 'eye-witness' account from a Dutch journalist on CNN who claims to have spoken to a number of passengers. They apparently described some turbulence (stall?) immediately prior to impact and all believe the aircraft ran out of fuel. Even though the passengers are clearly not 'expert witnesses', they were nonetheless very close to the event and their views are certainly ones that attract my attention.

There are, of course, many reasons why the crew could have faced fuel starvation, if indeed they did. It should be pointed out that if fuel starvation in some form turns out to be a factor here, I am not in any way ascribing blame to the crew. Many crews have faced challenging situations like this and it may transpire that they did very well in getting the aircraft down at all.
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Old 26th Feb 2009, 11:53
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I believe the usual intercept is around 30 degrees,

There was some information from the mode s giving a heading of around 260 at 189knts ish and a few miles have to look back to confirm but around 2000'

N
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Old 26th Feb 2009, 11:55
  #346 (permalink)  
 
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According to The Telegraph online, 4 Boeing employees were passengers.

may well be some worthwhile important witnesses....


Not if Rainbow see's it...those boeing people might not even have a Cessna 152 licence...rainbow doesn't like people even if they have experience through learning about 737's on their own back...in their house...he wants a 737 qualified person to give us the info...

But in my opinion...everyone who has true info..is just as good...whether its the passenger in the aircraft...he's not likely to lie about what he feels in his seat...
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Old 26th Feb 2009, 12:00
  #347 (permalink)  
 
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AutoThrottled again?

Synopsis:
A Reconstruction animation (not entirely accurate as it shows an attitude change (pitch-up) but no actual zoom): YouTube - blenderpedia's Channel
.
Stick-shaker suddenly alerted pilots (at around 110kts) that they were approaching the stall (due autothrottle [A/T] not engaged/inadvertently disengaged). Surprised pilots added max power and the aircraft then pitched up violently. Cause of this scenario and outcome (as per the Colgan Q400 accident) is two-fold:
.
a. If autothrust isn't present on a captured glideslope, the speed will gradually and insidiously bleed off (depending upon the power set at the moment of A/T disconnect and any subsequent-to-disconnect gear/flap down selections). The autopilot's auto-trim function will attempt to maintain the "captured" ILS 3 degree glideslope by trading speed for a height-loss regulated to the standard 600fpm rate of descent. (justification for this is a recorded lowest speed on finals of a pre-impact low-point of 88kts recorded on GPS for THY Flt TK1951 ). The record shows 88kts GroundSpeed at 420ft and a last recorded position N52 22.8 E004 42.8 (right where the impact occurred). 88kts GS was the final recorded value in the software log from a guy with a Radarbox Mode-S receiver who is fairly near EHAM, and has coverage of aircraft on the ground there so he would be able to receive the Mode-S from where TC-JGE was just before impact. Naturally because the position, speed and height transmissions are not all sent at the same time you can't say the three things are coincident, but they will be within a second or so
.
b. Because of the cumulative effect of near-to-full pitch backtrim (stabilizer and elevator trim movement towards nose-up as speed decreased) AND the strong nose-up pitching couple of max power at a low IAS, adding full power at near to stall speed caused an abrupt nose-up pitch, a stick-shaker

....and then a stick-pusher input, a pilot throttle-back at the apex of the zoom and, soon thereafter, a panicky pilot's hard PULL (for post-stall ground avoidance). It's a nasty and confusing sequitur that's never ever trained for in a simulator. Justification for this scenario is the witness reports (inclusive of the "turbulence buffeting" felt pre-impact and the pre-impact pitch oscillations (on the way down from its zoom-climb) -as observed by the qualified witness on the adjacent freeway).
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Causation: When you become used to the auto-throttle "taking care of" the aircraft's approach speed (per the FMS bug-set), there's no perceived (or real) need to monitor it closely for any required power adjustments, post-configuration increments etc. It (the IAS) and even the pitch attitude just "drops out of" the pilot's active scan..... and/or he/they become distracted anyway by a third member in the cockpit or another task (FMS keypadding etc). The type of scanning done nowadays is very passive and detached (i.e. no input required or feedback loop involved) rather than the old-school active pilot-involved-in-the-control-loop scan ("oops, I'm a bit low and slow - must add power/raise nose/trim and fine-tune that heading"). This automotive disassociation leads to a lack of due deference - and opens the door to any passing/insidious technical upcocks. We've not seen the end of these type accidents (and many have occurred to date - but never been acknowledged as such). So forget birdstrikes - in this instance. Inattention may be the real enemy
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Old 26th Feb 2009, 12:15
  #348 (permalink)  
 
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Originally Posted by funfly
It would be a terrible decision to make within a fraction of a second if you had to decide whether to impact a road/trees or take the risk of stalling while trying to 'lift' over.
The ground was basically flat for a great distance in every direction. There was no need to make any decision to clear the road/trees. That was a very minor obstacle to a 737-800.

What happened here is the aircraft stalled while on approach for some unknown reason. The recovery was either incorrect or incomplete.

The pilots didn't make a decision to avoid the trees. They were just along for the ride at that point.
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Old 26th Feb 2009, 12:17
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The eye witness accounts of a lack of engine noise do seem to be quite consistent in this accident. Included in that is the fact that surviving passengers seem to be convinced that the aircraft ran out of fuel. Now clearly the passengers would have no idea of the fuel state of the aircraft and possibly wouldn't recognise a double engine failure in any case but I would have expected them to notice a last minute application of go-around thrust and at least subconsciously associate that with running engines. These reports do suggest that there was no application of go-around thrust before impact.

I find this very strange if both engines were running. I can see how an aircraft could get low and slow and get well behind the drag curve without technical failure but I find it hard to accept that the pilots would get it so far out of shape as to contact the ground without shoving the thrust levers fully forward. I can see that they might do this too late to save the aircraft but an aircraft producing full thrust makes a lot of noise and the witness comments from within the aircraft and from the ground seem to indicate that no such noise was heard. I'm not making any rash judgements by this observation just that I find it strange that go around thrust does not appear to have been selected prior to impact based on the various witness statements released thus far.

Mmmayday38:-

Please don't take offence at this but I find it very hard to believe that you are who you say you are. PPRuNe is of course an anonymous forum where anyone can pretend to be anyone else. I'm not saying that you are not the Captain of the crashed BA 777 at LHR but we have no way of knowing either way and this forum does attract some strange people. You have only just registered on PPRuNe with a user name relating to that incident and it seems very unlikely to me that the true Captain of that crashed aircraft would just pop up on PPRuNe after all this time in this way. I doubt British Airways would allow it in any case. If you are who you say you are then respect to you but I suspect very much that you are not.
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Old 26th Feb 2009, 12:18
  #350 (permalink)  
 
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MahatmaKote is almost right with his analysis, apart from a centre-of-gravity matter. If the CoG is closer to the tail than nose, the acceleration of the nose after initial impact will be greater than 2*g.

Sorry; an academic point in a difficult and sad thread.
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Old 26th Feb 2009, 12:24
  #351 (permalink)  
 
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Nick, of course the 777 is FBW. That's why I mentioned it and in this context it is worth to see that everyone survived in LHR. The ground was also a bit harder, he had it nearly to the runway.

As for stall characteristics of airliners you are wrong: You can stall every aircraft, be it in whatever configuration. The stall speed goes down with leading edge devices (LED) extended, that doesn't mean you cannot stall it.

Except an Airbus in normal law, where it's impossible (some French tried it in Habsheim).

If you speak of low speed, that is also relative. If you hear expert opinions about speeds, they may certainly confirm that this accident happened in low speed. In opposition to an aircraft stalling in the air and falling from the skies with high speeds or like an aircraft crashing in cruising configuration. Let me reassure you that this THY aircraft crash landed with relatively normal landing speed, around reference speed. The investigators will certainly confirm that as soon as they have the results.

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Old 26th Feb 2009, 12:30
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737 approach procedure

There have been a few 737 low speed on approach events over the last few years (eg Thomson at bournemouth, circling at BOD) This may or may not be a factor in this.

Up till a few years ago, the Boeing procedure when flying manually on approach was to call for " speed off" (pushing the speed switch on the MCP) so the autothrottle no longer actively controlled thrust but was available in case of go around and provided low speed protection ( a bit like alpha floor on the bus)

This was changed, recommending having it completely disarmed (I believe because of unwanted autothrottle during the flare)

Perhaps this should be reviewed possibly clicking it out totally as thrust is reduced in the flare?
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Old 26th Feb 2009, 12:31
  #353 (permalink)  
 
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Respectfully,

The ground was basically flat for a great distance in every direction. There was no need to make any decision to clear the road/trees. That was a very minor obstacle to a 737-800.
there was a six lane motorway across the flighpath and also some (industrial?) buildings along that road, about 10 sec prior to where the airplane came down.

I agree the trees should not have been a factor, but a packed highway may be different.
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Old 26th Feb 2009, 12:33
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I was referring to the spin, the inboard LED's are designed to promote root stall and therefore negate the spin. I am fully aware you can stall every aircraft if you try hard enough.

If you look back there are reports from a mode s reciever giving the moment before impact 88knts groundspeed, that is NOT anywhere near Vref for the 800. Id like to see your evidence supporting this argument...

N
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Old 26th Feb 2009, 12:35
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nick14: I think Lon More has pretty well known that - it wasn't really the question


I don't really know about this A/T disc theory - if you go below the GS you'll get the GPWS alert straight away, so I guess you'll notice it, don't you? Not talking about the altitude alerts of the GPWS.

I don't want to speculate, but for me it looks like if it was a normal landing and they just missed the runway. So I would take the possibility of an ILS/GS problem into consideration as well - on both sides, but I'm sure the investigators will check on that.
To be honest it reminds me to the AEA incident at EPKK - they were just lucky enough to make it to the rwy after having destroyed the landing lights... Can't recall though if I've read anything about the reasons of that one.
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Old 26th Feb 2009, 12:39
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If as so many are assuming this is a stall with high AOA and little forward speed, why can't I see in the debris field or poking through the tops of the wings, and sign of the undercarriage here.
I was refering to the BA 777 incident, where at least one bogey sheared off and was in the "debris field", and the other was quite visibly seen in the wing root.
Here I can't see any sign, or I need to put my glasses back on for reading.
For the fuel starvation wolf-pack
Was the gear selected down, maybe trying to save on what little fuel they had, and it didn't work
and for the conspiracy theorists
did they forget to put the gear down, on a training flight, aka the three man crew (perhaps only guessing) did the trainee panic on the sounding of the EPGWS and pull back hard... just a theory thats all...

but my main point is still where is the gear.... - up, destroyed, detached, crumpled, why not as expected in heavy estimated 9G landing they weren't pushed up, or was the ground too soft..... probably just answered my own question but still puzzled.....
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Old 26th Feb 2009, 12:40
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Do we know if the gear was down?

Normally in accidents like they were do see parts ofn the gear in the side as its torn away, but in the pictures we have seen so far there is nothing to indicate that is was deployed and torn off.

This possibly points to 2 scenarios:

*Gear was not down and the crew were in real trouble.

*The a/c went stright into the ground with very little forward momuntum and the gears were burried.
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Old 26th Feb 2009, 12:49
  #358 (permalink)  
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Old 26th Feb 2009, 12:51
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http://www.nu.nl/slideshow/1877725/popup.html#


Photo number 4 shows a landing gear
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Old 26th Feb 2009, 12:52
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Dani -
I want to reiterate (as in the Hudson River thread) that Airbus has somewhat some advantages over a 737 in this crash scenario because with its fly-by-wire suit it is much easier to be controlled close to ground and stall speed.
That is an interesting remark. Would you care to explain that?
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