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Turkish airliner crashes at Schiphol

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Turkish airliner crashes at Schiphol

Old 27th Feb 2009, 05:27
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PJ2,

You have all my respect and admiration for your wise words, technical knowledge and pointing out the morbid in some of our colleagues....
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Old 27th Feb 2009, 06:15
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Marsh Hawk asked: how instrumental was the muddy field in increasing the survivability of this accident? It seems to me that the yielding dirt cushioned the vertical forces just enough to make this accident survivable for most

I remember some tests done by US Authorities years ago using actual airframes which determined that - contrary to what one might think - impact on soft ground results in higher G forces as the aircraft tends to dig in and stop; on hard surfaces the aircraft tends to slide. I don't think this is particularly relevent in this case, however, just giving an answer to a query.
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Old 27th Feb 2009, 06:20
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Once again looking at the ADS-B Google Earth track plot,

assuming the 370 ft altitude correction mentioned in my previous post is correct, it appears the plane remained on the glideslope all the way to the second last data point at 9:25:53 which is 1.3 NM from the threshold. The ADS-B plot shows a height of 445 ft (75+370) at that point. This fits well with the approach chart descent profile which says 355 ft at 1 NM from the threshold.

Did the autopilot "pull" the plane to remain on the glideslope, while the power was insufficient, causing it to slow down until it stalled? In that case a very similar-looking scenario to BA038... ???

Assuming the above is correct, the next interesting question is then whether the autothrottle was engaged. FDR will answer that. Please correct if you find this theory impossible....

Last edited by snowfalcon2; 27th Feb 2009 at 12:25. Reason: added last paragraph; fixed link error (thanks for the heads-up ;)
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Old 27th Feb 2009, 07:16
  #564 (permalink)  
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Originally Posted by Markle
BTW Here's the pic where the rescue squad got into the cockpit. It doesn't look like the roof is hacked any more than it was with the piece of support popping out. It does look like the cockpit and first class acted like a ground anchor. That's what, 5 feet of crush and 10 feet out of alignment?
The roof was hacked by the fire and rescue team.

Early on there was TV coverage showing a rescuer on the roof attacking the fuselage with an axe. The shot was from the starboard side.

It seemed odd at the time that they had not tried entry through a side window; had there been sign of life it is perhaps more likely that a window would have been used for entry or exit.
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Old 27th Feb 2009, 07:20
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Engines stalled on finals

A report in the Times of London - link below - states that one of the Netherlands aviation authorities suggests that both engines stalled on finals.

Engines stalled before Turkish Boeing plunged into Schiphol field - Times Online
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Old 27th Feb 2009, 07:24
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Originally posted by DingerX
Oh, and forgetting to set the altimeter? We're not talking about the Thunderbirds here.
It has happened before, and depending on the actual QNH it can make a significant difference in altitude reading. But in that case the aircraft wouldn't have followed the normal glide path before things went wrong, so probably irrelevant here.

Last edited by Moira; 27th Feb 2009 at 08:08.
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Old 27th Feb 2009, 07:51
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Times item

Stalled engines were identified yesterday as the likely cause of the crash that killed nine people when a Turkish Airlines flight plummeted into a field on its approach to Schiphol airport.

The chief investigator, Pieter van Vollenhoven, said that the Boeing 737-800 had fallen suddenly from the sky, suggesting that both engines had stalled as the aircraft slowed on its descent to the runway south of Amsterdam.
That appears to be the product of a journalist who has failed to understand the distinction between aerodynamic and engine stalls.
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Old 27th Feb 2009, 08:00
  #568 (permalink)  
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I'm only a PPL so can someone estimate what the landing speed should have been, roughly? Looking at those OpenATC screenshots I find it strange how they went from a normal -700ft/min descent at 09:24:23 to -1344ft/min and -1216ft/min at 09:24:38 and 09:24:53, respectively. They then recover this descent back to a normal rate after that, though with an increasing loss in speed. Am I right in thinking they were above the glidescope initially, then tried to reintercept it, which seems to be when the problems started. So maybe the question is why were they high initially, and did they just do a bad job of flying the rest of the approach?


Please read the thread. This was asked and answered earlier on.

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Old 27th Feb 2009, 08:06
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Basically, Vref should be around 120KIAS. Plus or minus depending on weight and flap setting.
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Old 27th Feb 2009, 08:22
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I read the Times article by David Charter.
He doesn't seem to have done any research at all. He picked up the word stall as a possibility and made up the headline " Engines stall "

Just remember when you read an article about a subject your not familiar with it's written by idiots like him, with even less knowledge.
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Old 27th Feb 2009, 08:42
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Why is no one discussing the possible recurrence of one of the malfunctions (such as master caution light) that occurred previously?

Do you just trust that it was repaired properly?
 
Old 27th Feb 2009, 08:49
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Originally Posted by Pontious Navigator
The roof was hacked by the fire and rescue team.
Originally Posted by Pontious Navigator
Early on there was TV coverage showing a rescuer on the roof attacking the fuselage with an axe. The shot was from the starboard side.
It seemed odd at the time that they had not tried entry through a side window; had there been sign of life it is perhaps more likely that a window would have been used for entry or exit.


The rescuer was hacking at the structure protruding through the crown skin probably in an attempt to release the flight deck door not to gain entry directly.
I don't recall if there is an external release for the dv window on the 737. I think you may have to cut in through the skin and release the window at the top.
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Old 27th Feb 2009, 08:56
  #573 (permalink)  
 
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yeah but when the last data burst goes out during touchdown it clearly doesn't transmit the last air speed... Most probably the cockpit was the last part of the aircraft that stayed intact and thus could still send data while the aircraft had "landed" already!
As previously pointed out, ADS-B doesn't transmit airspeed at all - only groundspeed (and the GS values are near-real-time, not averaged)

It's also highly unlikely that the speed readouts were from the aircraft once it was on the ground. Mode S uses 1090MHz, which makes it even more line-of-sight than VHF - unless the enthusiast with the Mode S receiver was very close, they would only have received transmissions while the aircraft was airborne and above their radio horizon (as indeed the height readouts indicate).
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Old 27th Feb 2009, 09:02
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there IS an external release for the R/H DV window. however with that much damage on the airframe it might have been blocked.
===
John R:
there might be not a lot of (actively flying) airliners that do not have any entries in the tech log within a week!
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Old 27th Feb 2009, 09:22
  #575 (permalink)  
 
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A bit of graph paper and google earth + open ATC =

4.2 D 150' above the glide correcting 159 gs.(wind was reported as 210/10 so lets use 8 head for airspeed that gives 167kt
3.6 D 30' above 156kt

2.9D on glide 153kt
2.4D on glide 137kt
1.8D on glide 126kt
1.4 D on glide 94kt
1.2D wrekage

with a gs of 86kts as the last known speed thats 11 seconds for the last 450'

This really looks like the jet captured the glide and decelerated until sometime after 1.4D where it stopped flying and hit the deck 1/4 of a mile later.
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Old 27th Feb 2009, 09:41
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Visual illusion

Dear readers / collegues,

First of all I would like to apologize for not reading every posting here. I did read about 50% though.

I have 16 years of 737 experience, of which most as test-pilot and instructor.

I 've seen no reactions so far regarding possible visual illusion during cloud break. Low cloudbase at 700' and visibility of 4000m tempo 2500m can give a momentary impression of extreme low pitch. This is a scary sensation when you are at low altitude. An agressive reaction to this sensation could have been an agressive pitch-up, resulting in an accellerated stall. A pitch down movement would be normal after such a stall, this is per aeodynamic 'stable' design. As an instructor, you would have no options left to counteract such an act of your student....
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Old 27th Feb 2009, 10:08
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@AstonMartin

Very sensible suggestion but unlikely. The last thing any pilot would on gaining visual contact from a stabilised approach is to punch the AP out and make a sudden pitch input. I'm not convinced.

I am now getting rather fed up with the number of 'experts' posting here. There are a great number of contributors who pose as ATPL holders whose theories and suggestions give away the fact they have no experience whatsoever in aviation.

Seriously considering not contributing here anymore.
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Old 27th Feb 2009, 10:39
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Now the mods have a better grip on this thread, could I ask that posts which imply negligence by dead pilots be reviewed also? Rainboe's 'suggestion' that wing fuel 'mismanagement' may have caused the crash are, I think, offensive.

Some points on that process:-

a) It has been an 'approved' procedure at some airlines for a while on the 737NG
b) I was given to understand it had a 'no objection' from Boeing which is the right side of 'don't do it'.
c) We do not know if THY approved the procedure or not
d) There are several considerations in use:-
1) ZFM limits (for wing bending relief)
2) Competent crews ensure a sufficient div fuel in the wings on approach in case of centre tank feed issues.
3) Trim issues are insignificant
e) IF the flight return tanked from IST there was no option for 'ground transfer'
f) Several warnings would have to have been 'ignored' by the crew. and this is where I baulk at this suggestion without evidence
1) Wing tanks reducing below expected
2) Low fuel warnings (906 or 403kg per side depending on setting ) - still enough on approach to land.
g) I have done it many times and it is a 'no problem' techiqueAll the recorders will tell us whether there was 'negligence' or not, and we should not rush to speculate.

I am lost in the crud here on this thread, but has one possible cause been mentioned ie wind shear/downdraft? It looks extremely unlikely from the TAF but................
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Old 27th Feb 2009, 10:40
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Aston martin,

Good and well put suggestion.

I would imagin though looking at the data on top of this page that a control input like that would have thrown them well above the glide at such a low altitude (very sensitive needles that close in) and it doesn't seem to show such above?

Any thoughts?

N
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Old 27th Feb 2009, 10:46
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A report in the Times of London - link below - states that one of the Netherlands aviation authorities suggests that both engines stalled on finals.
It seems that the report ACTUALLY suggests the engines were not delivering power- as would happen if the engines were at idle.

And of course, as soon as the word "Stall" appears in the lexicon, journalists relate it to there mini-metros and assume engine failure.

One of the most challenging things to do in a Boeing (and I would assume other makes) is do an Auto-pilot on GS capture from above.

SOPs almost always mean the Platform Altitude is set in the MCP. Descend in VNAV SPD or FLCH with the GS armed and reach the MCP altitude fiirst, the aircraft captures the alt and levels off, putting it FURTHER above the glide.

I've seen this many times, both Aircraft and Sim. Already hot, high and loaded, the pilot is suddenly faced with an aircraft not heading down, with TLs increasing thrust.

One (Pefectly valid) reaction is to disconnect AP and increase descent rate to capture the GS. In 737s, many operators SOPs require (and, indeed, Boeing reccomends) that AP off means AT off as well.

I'm a couple of years off the NG, but I seem to think that in the above senario, there would be no Autothrottle Wake Up if speed decayed. Is that correct?
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