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Turkish airliner crashes at Schiphol

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Turkish airliner crashes at Schiphol

Old 6th Mar 2009, 08:16
  #1461 (permalink)  
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rhythm method - please read my POST!!!! The answer is there.

No, I have no knowledge of radalt switching. NB The tech manuals we get are skimpy at best! You need the AMM to find out. 737AVEng is on the case, I think.

Rasper - that does not sound like a 737 - what was it? NB There is no mention of a gear horn in the report.
Originally Posted by MB
What a pity that these pilots didn't appear to look up and out for just a second.
- perhaps better to say 'DOWN and IN ' for a second?

Last edited by BOAC; 6th Mar 2009 at 08:28.
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Old 6th Mar 2009, 08:17
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stickyb, yes. The thrust levers come back until they physically cannot move any more. It is not an aircraft like the RJ or 146 which has a flight idle baulk which withdraws on touchdown to a ground idle position with about 10% N1 difference.

Last edited by rhythm method; 6th Mar 2009 at 08:27. Reason: Better terminology
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Old 6th Mar 2009, 08:24
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Cyberstreak,
If what you have posted is true any advancement in flight safety in Turkish Airlines is going to be jeopordised by an orgy of lies & self-denial ( "it was too late to do anything once the speed dropped below 250kmh / there was no fault with the A/T on the previous 8 flights" . . . . . yeah, and like they said immediately after the accident ,nobody has been killed. . . right ? )
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Old 6th Mar 2009, 08:30
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Here's a thought for the REAL 737 drivers out there. If, as it appears, we really do have to cater for lack of speed monitoring, why not push for an immediate change to min speed rev to allow it on a coupled GP, down, say to 100' (as I understand AB) or to FLARE active?
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Old 6th Mar 2009, 09:13
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Had a similar fault myself

Between six and twelve months ago, I flew an 800 that displayed some similar issues.

On the first take off, the left rad alt continued to indicate -8 feet until passing about 2500'. This left the A/T stuck in TOGA and prevented the engagement of LNAV. Solution? Disconnect the A/T and fly the SID in raw data. Briefly confusing, but not a crisis.

On both arrivals back to the same airport, the left RA again read -8' (intermittently, rather than continuously), and the config horn sounded while down wind at 5-6000' decelerating from 250kts to clean speed. It also sounded the 50, 40, 30 calls of the flare while still at 5000'. At no point did the amber RA flag appear on the PFD, suggesting that the avionics did not recognise it as a false reading.

Did we bend the aeroplane? No - we just flew it normally. If you monitor what the aircraft is doing, such failures make virtually no difference to the flight. Before anyone asks, yes, the occurrences were reported in detail to the engineers, and no, I don't know what the causes of the intermittent error in the RA were. It was, however, restricted from Cat III ops until rectified.

My interpretation of the initial report is that a minor malfunction combined with the crew's failure to monitor the aircraft resulted in CFIT. The malfunction should certainly not have been enough to even mildly jeopardise the flight, had the crew been paying attention at a critical stage of flight. I will, however, remain open to new information regarding crew incapacitation or massive distractions from other problems.
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Old 6th Mar 2009, 09:24
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To further NoD's comments, while the pilot's inattention seems to be the main cause of the accident, the failure of an input system was the initial trigger for the chain of events. Given that this failure cause erroneous indications on the PFD and erroneous actions by the automatics, rather than being detected, bringing up a warning flag and causing the data to be invalidated from the AFDS, this shows how vital it is to have a human brain (two or more, actually) monitoring and controlling the overall show. Human brains have the capability to look at all the different parameters and determine what is actually happening, but automatics can't always do that. As for the comparison to Airbus, from what I gather, never having flown one, they're great until things start going awry, at which point mode confusion becomes a really big problem. I prefer everything to be kept relatively simple, with as many cues to the pilots as possible with regard to what the aircraft is doing - not just visual or aural, but tactile too (I don't like the idea of the throttles and stick not moving on the Bus). The important thing, regardless of type, is that the pilots monitor the aircraft properly and have a good knowledge of how it works.
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Old 6th Mar 2009, 09:26
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BOAC, you haven't missed anything. With a radio altimeter inoperative the autopilot will disconnect 2 sec after LOC/GS capture.
Are you are sure you aren't getting mixed up with autothrottle disengagement 2 seconds after touchdown?

BOAC, I am not sure if you are B737 or not, if you are, have you found anything in the manuals regarding the A/T logic of switching from left RA to right RA with a failure?
The above statement is correct. In dual mode the autopilot will disconnect 2 sec after in case RA1 lost. Vice versa you can not engage the second autopilot in case RA1 failed.
I am also searching a clue suggesting that the A/T system was designed to switch to the correct RA in case of false reading. So far nothing... When checking the schematics can not see much in this direction while the above mentioned switching might have been a hidden circuit.
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Old 6th Mar 2009, 09:27
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Whippersnapper's posts summarize everything so well, that until more information is posted about CVR, FDR and the other possible distractions that possibly unveil during the course of investigation, this thread could easily be locked and tucked away for the time being.

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Old 6th Mar 2009, 09:42
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"Dutch press (ANP): Turkish Airlines stated that "if you read the report carefully, you conclude the pilots are not to blame". "When the speed is less than 250 km/h, there is nothing you can do. They were already at 178 km/h" according their spokesman. Turkish arlines say the Boeing 737's equipment was faulty. "There was nothing found wrong with the altimeter in the previous eight flights. Doing the maintenance inspections we followed Boeing regulations." (translated from Dutch)"

What the F...

I thought the yanks captured Bagdad Bob long ago? Can it be his brother?

Every airline can have a disaster, I would never throw the first stone on them for that, but it's the way they handle it that shows the difference in safety culture.
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Old 6th Mar 2009, 09:49
  #1470 (permalink)  
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Man/woman machine interface.

It is incumbent on the pilot of any aircraft to monitor airspeed and altititude. No amount of automation can replace this duty. Obviously we still don't know what happened in this tragic case but appeals for further intrusive alarms and electronic intervention seem to miss this point. We seem to be pushing the pilot futher and further out of the loop thereby making the human interface the most crucial, yet the weakest, link in the control and management chain.
 
Old 6th Mar 2009, 09:57
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whippersnapper
My interpretation of the initial report is that a minor malfunction combined with the crew's failure to monitor the aircraft resulted in CFIT.
I don't think the "C" applies here...
Given that this failure cause erroneous indications on the PFD
True or false? I think the indications were probably correct (I am not 737 rated) - unexpected at that height perhaps, but not erroneous.
As for the comparison to Airbus, from what I gather, never having flown one, they're great until things start going awry, at which point mode confusion becomes a really big problem.
Perhaps you should go and work for Airbus and help them fix the really big problem? Oh, sorry, I didn't notice that you've never flown one.
(I don't like the idea of the throttles and stick not moving on the Bus).
They are THRUST LEVERS, they do move, as do the sidesticks - the difference is that they are not backfed by the automatics. In this accident moving throttles do not appear to have made any difference to the crews' S/A.
The important thing, regardless of type, is that the pilots monitor the aircraft properly and have a good knowledge of how it works.
Agreed.
TP
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Old 6th Mar 2009, 10:18
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Michael Birbeck,

Allow me to disagree. Since the Wright bros there has to be someone flying the plane, because the plane doesn't know how to fly itself no matter how sophisticated the machine is. Automation just helps to "freeze" a clear intention of a pilot, like "stay on the g/p" or "keep my speed at X" allowing time for other tasks to be performed. If you tell the machine "help me on this" you have to keep an eye on what is going on, just in case the machine drops the ball, and if drops you already know what needs to be done (otherwise you wouldn't be qualified to operate it). Airplanes are so damn reliable these days that I suspect some pilots sometimes forget that they can malfunction at any given time, Murphy’s' law and all that.

GD&L
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Old 6th Mar 2009, 10:27
  #1473 (permalink)  
 
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Lock the thread?

Tero,
Though I understand your point (as I'm sure most pprune readers do) I think we gain a great deal on this site through the occasional gem that shines through the detritus on this, and similar, threads (i.e. Airbus at Perignan, BA at LHR, etc).

I would suggest that some very enlightening and engaging online "workshops" have taken place on this thread as a result of posters bringing up notions in the context of this event. Examples (IMO at least) are: OFSO's comments on man-machine interface, discussion of the apparent increase in "loss of control" accidents, and CFIT issues.

If someone (or a mod) wants to creat a new thread on any issue arising, that would be fine of course, but if that new thread is not somehow tied to "Rumours and News" it seems to be easily missed.

So . . . in that vein, I propose the following (for discussion purposes):
In my opinion this is not a CFIT event. The ICAO definition of CFIT (accepted and used by JAR) assumes that controlled flight into terrain means that a servicable aircraft is flown into the ground (or water) with no time, or insufficient time, from the point of realisation for recovery to occur. From what we now know it seems there was sufficient time for recovery.

Does it matter? Maybe not, except for somebody's statistical review of aircraft accidents. What I do believe is that this tragedy will become an oft discussed and reviewed event in future classes/discussions/papers on flight safety issues.

Grizz
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Old 6th Mar 2009, 10:33
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Nothing you can do ????

When the speed is less than 250 km/h, there is nothing you can do. They were already at 178 km/h" according their spokesman. Turkish arlines say the Boeing 737's equipment was faulty.


Not 100% true.

In the past some earlier Airbus A/C, namely A310, had some low speed and low altitude incidents. Cause by automation / flight crew confusion.

Some that survived used non standard, seat of the pants flying skills to recover. Even from much lower IAS than this Turkish aeroplane and very high pitch attitudes.

Some years ago DXB ATC witnessed a spectacular manouvre as they were rapidly escaping from the TWR

My 1/2 pence..

Last edited by Capt Groper; 6th Mar 2009 at 12:35.
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Old 6th Mar 2009, 10:33
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the fact surely remains that as with the Helios 737 crash this event could apparently have been avoided by clearer, more distinct and less ambiguous warning system design by Boeing.
No,I dont agree.As 737 pilots have pointed out,theres no data about the effect of #1RA status on AT operation in the pilots OM manual,only in the MEL and AMM.They dont think as a pilot you need to know this.Why?Because failure of #1RA might disengage the AT or engage it in the inappropiate mode but it will never obviate the pilot's responsibility to monitor the A/S.They mention it in the MEL and warn the pilot to use manual thrust in case of RA#1 anomalies.(unfortunately,the recurring RA problem was never put in the Tech Log,a fact that will figure highly in the report Im sure)If the pilot wishes to gain a deeper understnding of his systems,he may self-educate himself by getting hold of a copy of the AMM.Probably way too complex for a mere pilot anyways.

Rhythm method,
Wouldnt you say its safe to say that BOAC is/or has been a 737 pilot?I think its pretty obvious.

BOAC,
I think its possible that the Turkish TC knew that #1RA would affect AT operation without having to consult his MEL (ie he did know his aircraft in theory) but that he just didnt apply that knowledge in practice due to the fact:
i)approach may have been rushed..failed to check FMA status
ii)the AT physically engaged..or didnt disengage..and as it remained engaged he assumed hed get his alpha floor too
iii)never seen a RA false reading before,only a failure
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Old 6th Mar 2009, 10:35
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Man/woman machine interface.

GD&L

I guess we are forcefully agreeing. Automation is a tool and like any tool can be misused or abused. What with the advent of the glass cockpit I believe we are pushing the crew into the areas of cognitive overload in high stress situations. Too many modes, too many codes. Fact is that the fallible human is still crucial but flawed.
 
Old 6th Mar 2009, 10:38
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There's a world of difference between 'failure' and outputting an incorrect value, in a system without checks and balances.
Of course a system that outputs an incorrect value is failing! it is a form of 'automation complacency' to state it is not. Whether or not the system signals its 'own' failure is an entirely different story. The subsystem that checks whether there is a failure can fail as well (for example by not taking into account all possible failures)!
This is an old principle:
Quis custodiet ipsos custodes?
(Who will watch the watchers themselves?)

The guiding principle should be to always crosscheck available data (all radio altimeters, speed indicators, etc etc) and bail out to human intelligence when things do not make sense.

I notice it seems to be difficult for many to separate the analysis of causes from appointing blame. A path in a causality graph is simply a 'chain of events'. Each item in this chain exists, for if it would not the chain would break and the accident would not happen (in this way). That's all there is to it. It exists. It does not have the property 'importance' or 'blame'. All items in this chain are equivalent in the sense that they deserve study.

Many issues have become clear:
- aircraft with recurring defect
- failure not signalled
- source of good data ignored
- no data crosscheck / system bailout at next higher level hence no warning
- non-intuitive design of system (RH AP, AT uses LH RA, AP/AT not single system)
- no crosscheck at next next level for mode confusion between AP and AT hence no warning
- regarding as unimportant the gear warning / RA failure
- not monitoring primary flight parameters by crew
- late reaction on stall by crew

Many others might be hypothesized at this point.
One should objectively look at these.
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Old 6th Mar 2009, 10:40
  #1478 (permalink)  
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Originally Posted by wingletflyer
The above statement is correct.
- of course it is, but the context in which it was used in relation to THIS accident was not. Please re-read airbusa330's original incorrect statement (around 1347) and my reply at 1501. I am merely trying to ensure that those posting know what we are told actually happened, not what they made up, otherwise this thread becomes even more of a farce.
Originally Posted by MB
I believe we are pushing the crew into the areas of cognitive overload
- absolutely right, and the 'cleverer' the a/c gets the worse that situation becomes. B2 crash and latest AB at PGF I would propose as supporting that plus the early AB accidents. The situation is aggravated when pilot experience no longer has any 'feel' for the a/c and it is 'sanitised' (like autotrim in the 320), and we really do need to either ensure we have PERFECT FLAWLESS auto systems or we improve training.
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Old 6th Mar 2009, 10:47
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If you're in the fast lane of the freeway and your cruise control drops out, don't be suprised if you get tail-ended. The vital lesson to be learned is why didn't you notice you were slowing down.
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Old 6th Mar 2009, 10:51
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There has been so much 737-techie stuff lately on this thread and whether this is linked to that or something else dropping out will annunciate what ...

While I cannot comment on such debate as I am not 737-qualified, I am a Boeing (747) man and surely, the basics are:

1) An automatic approach must always be monitored against the raw data by the PF (indeed I favour shadowing the stick & thrust levers)
2) Any failure should result in PF hand flying (if necessary) until the fault is corrected
3) If there is time, the automatics can be re-instated by PNF, otherwise
4) Revert to a hand-flown approach and landing, or
5) Accomplish a manual go-around.

One thing appears to me to be coming through time and time again - practically an obsession with getting the automatics back "in" to avoid a manual landing. Why? Is it really because many pilots are losing their basic skill set and are prepared to almost risk the safety of the aircraft trying to re-instate A/P A/T ILS LAND, rather than take what should be a welcome opportunity to manually fly and even manually (shock! horror!) land their own aircraft ... ?

I have always believed (and trained) that automatics are there as an aid to the pilots - not as an end in themselves.

... or is it just that I am getting more like Victor Meldrew every day ...


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