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Turkish airliner crashes at Schiphol

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Turkish airliner crashes at Schiphol

Old 6th Mar 2009, 17:49
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737-800 has a different wing and longer fuselage at a minimum. To conclude that a simulation on a 737-300 replicates the 737-800 crash is premature, but it is worth investigating. And if found true on the 737-300, or the 737-800, the certification process needs to be looked at.

So far my favorite - "maybe they got distracted doing the radar altimeter failure emergency checklist".
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Old 6th Mar 2009, 17:49
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The reason for our not recovering was due to the extreme amount of trim the autopilot had applied while attempting to maintain the glide slope. The only way that we could have recovered would have been to apply extensive nose down trim during the initial recovery.
Very interesting. When practising stall recovery in the simulator we are usually in manual flight and only trim nose up a limited amount during the deliberate deceleration prior to recovery. I suspect very few B737 pilots have ever practised a stall recovery where the airplane was in-trim at stick shaker activation.
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Old 6th Mar 2009, 17:52
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worked fine for all the world for 25 years.........except for 1 flight
........and a couple of in-trim 733 SIM experiments today?
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Old 6th Mar 2009, 17:56
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We have a direct parallel here with the AB crash at PGF on the other thread. As said before, it required the reduction of power once the stall had been corrected before the nose went too high, or a wing down to stop the climb. Neither necessarily practised although both part of the Boeing 'Upset' recovery brief. This sort of stall is NOT something we practice. There is insufficient elevator authority to control the power/pitch couple which is why a limit on minimum trimmed speed is placed on air test stalls. Had these sim guys followed the Boeing training they would not have crashed either.

However, my (and the main) the focus should be on how it got to the stall, plus a salutory reminder to ALL crew to revise upset recovery.
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Old 6th Mar 2009, 18:00
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Sorry guys maybe I missed something here but looking at the plot above do we know why the a/c initially went high (at 5 - 6 miles) although on glideslope at just over 6 miles?
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Old 6th Mar 2009, 18:02
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Nice and interesting this "stall-recovery-procedure", but...

I was told and teached how to recognise and avoid such an event. (and yes I did practice stall-recovery-procedures in many types)
Sorry, but 3 pairs of eyes could and should have seen/scanned/observed the (negative) speed-trend!
And as an instructor you know this kind of flights and (for me) you are more "on-the-ball".....just my few cents
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Old 6th Mar 2009, 18:10
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I was told and teached how to recognise and avoid such an event. (and yes I did practice stall-recovery-procedures in many types)
Sorry, but 3 pairs of eyes could and should have seen/scanned/observed the (negative) speed-trend!
And as an instructor you know this kind of flights and (for me) you are more "on-the-ball".....just my few cents
testpanel, spot on!

Difference between the signs of an approaching stall versus symptoms of the full stall.

First sign of an approaching stall is decreasing airspeed, reduced control effectiveness and (often but not exclusively) high nose attitude.

This is all basic but perhaps we should also recall that whilst on approach in a swept wing jet transport the speed is below minimum drag speed. So if speed decreases, drag increases ergo more speed decrease! So even if approach power is selected you can't ignore a speed trend. And if the speed gets very low then full power will not overcome the high drag so you have to lower the nose to get some speed on but you need some height to so this.
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Old 6th Mar 2009, 18:15
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justice

The Main objective of an air crash investigationis to find out what happened.
We owe that to the people involved in the crash and future airtravelers and people who are involved in any way.

Therefore the procedures followed and rules to execute the investigation are of vital importance.

There are however special interests involved which might reduce the investigation to a blame game for the sake of money, reputation and politics.

In order to safeguard the finding of truth and justice we need independent investigation authority.

The only way to reach truth and justice is found in the cooperation of investigative bodies and information sharing to the advantage of the other.

This will require coordination between the respective authorities and it will take time.

For the sake of safety for people in the air and on the ground.

I have read a lot of smart comments in the postings on this forum.
However I doubt that any one actually has full access to the data recovered from the crash site, Air traffic control data, ILS integrity monitoring data, Weather data, Crew data, maintenance records etc.

We have to insist that the investigation is carried out in order to find truth and justice for all involved, then, now and in the future.

Obstruction in any way to this process should be considered obstuction to justice and truth.

Lymbo
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Old 6th Mar 2009, 18:19
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Sorry, but 3 pairs of eyes could and should have seen/scanned/observed the (negative) speed-trend!
Absolutely agree with this. I am very concerned about the level of automation complacency that has crept up on some professional pilots over the years. Many airlines now mandate 'maximum use of automation' rather than 'appropriate use of automation' and this doesn't help with the above problem.

It's just interesting that at stick shaker activation on the accident flight, recovery was always going to be a challenge, to put it mildly. I say 'interesting' but the whole thing is a bloody tragedy. Let's hope some very important lessons are learnt by the industry.
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Old 6th Mar 2009, 18:22
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Onset of Stall

Excuse the for sounding silly...before I get the ridicule of everyone...but in the 737/300/400/500 level D sims I used to do the controls software on, the pilots recognised the onset of stall by the buffet quite a bit before...so the stick shaker was never an issue. Is it different for a 'dirty' stall or are the sims incorrect?...or the the pilots more aware in the sim?
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Old 6th Mar 2009, 18:23
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thanx

I would also like to thank Safta and his team for the dual sim run and the results you have shared here. As one poster noted it went quiet in here for a few minutes.

As stated this needs to run on a 738 sim....and I would be very surprised if it has not with the rough data available from OpenATC as far as location, time, height, and speed. Further, part of any aircraft incident investigation is to load the FDR data into a comprable sim and run it...I would suggest Boeing has either done it or is about to.

Lastly regarding the CVR I thought that it has been established recently that public release of the full CVR tapes does not happen now like it did in the past and instead transcripts are made available...or is that a country specific ruling?.
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Old 6th Mar 2009, 18:24
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wingletflyer . . ."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...
Glueball wrote:
Don't you see a semantics problem with your statement? What logic would apply in differentiating whether RA1 or RA2 is reading correct altitude? How would RA1 "know" that its value was incorrect? How would RA2 "know" that its value was correct? I think that what you want to research is if one RA becomes inoperative [red flag] that control will be switched to the other RA?
Who said that there was a flag indicating the RA1 failed? The RA1 was simply showing -8 feet with NO FLAG! On the other hand what you say it's true. Who is checking whom with what reference..
Would be nice to have a simple miscompare feature build in RA system..
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Old 6th Mar 2009, 18:33
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Posted by lymbo:

I have read a lot of smart comments in the postings on this forum.
However I doubt that any one actually has full access to the data recovered from the crash site, Air traffic control data, ILS integrity monitoring data, Weather data, Crew data, maintenance records etc.
I agree with your post but relatives should and deserve to know that as it looks right now, this a/c had: 2 wings, a fuselage, 2 WORKING engines, no problems with primary nor secondary flight-controls, 3 pair of eyes in the flight-deck, etc etc, they "only" had a R.A. problem.....and they crashed (a for the rest complete perfect a/c)
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Old 6th Mar 2009, 18:48
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Several people have made reference to Professional pilots ...

Commercial Pilot does NOT EQUAL Professional Pilot (unfortunately)
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Old 6th Mar 2009, 18:54
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This thread is positively overflowing with helpful and well-intentioned comments of "adding a few lines of code" here and there, "improved system logic" etc...

The results of such efforts would be:

- More complicated systems. Already, pilots are just barely able to keep track of all details of every system; it has already gone so far that systems descriptions are removed from the pilots' manuals, on the basis that they neither need, nor indeed can, understand how the plane works.

- More design errors. Not only the pilots, but indeed the engineers, can no longer keep track of how the systems work. I'm not tallking about "simple bugs", but system design failures and unpredicted behavior.

- More bizarre failure modes. This is the result of the previous points; when the systems get increasingly complex, they will also fail in more complicated ways. Cascading faults, and redundant, error-monitoring systems switching each other off, resulting in systems shutting down or acting strange that would appear to be unrelated to the original error.

- Increased cockpit confusion. Systems that nobody fully understands, failing in ways that nobody can quite predict, probably even providing "helpful" error messages explaining that they just went offline... Or, equally bad, failing to a degraded mode without telling the pilots, meaning the pilots have no way of knowing what state the aircraft really is in, and therefore how it would react to any further system degradation. Aircraft reacting differently to the same event on different days, depending on whether some particular computer is in "Degraded state 2" or "Degraded state 4" while another computer is in "Secondary Alternate", or not.

- Increased revenue for software design companies.

Thanks, but no thanks!
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Old 6th Mar 2009, 19:06
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RadAlts - post 1596

Please read my post 1212. As many have said a radalt is a luxury to help the pilot not replace a function of him/her.
However a system that feeds verifiable erronious information to the system, (by system I mean the pilots and automation that together fly the plane), is ridiculous. if the radalts disagree they should both be discounted and the "system" told to disregard their inputs. if they disagree due to flying over mountains or whatever, then fine, they drop out: they are only a luxury. There are only of use during the landing phase in any event.
I don't have an axe to grind here, I've never flown anything with any form of automation not even engine control - well ok a governor - but what I am sure about is that airliner automation will become more and more sophisticated, the pilots job will be further de-skilled during the 99.99% of the flight, due to the continuous financial pressures on the industry the quality of the intake into the flying schools will gradually drop, the expectations and acceptance of "perfect automation" will increase and the new generation pilots won't know what the hell is going wrong when it does. it's therefore vital that the automation is constantly improved to fail safer, and communicate it's failure to the crew in a simpler way.

I'm not saying it's Boeing's fault; it's just another item that can be improved through experience to make the likelyhood of the cheese holes lining up less likely.

James
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Old 6th Mar 2009, 19:13
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Rainboe wrote:

and have produced a system that has worked fine for all the world for 25 years.........except for 1 flight.
and he misses the point. This was not a random event, not a 'stray bit in a stream of good data'.

The circumstances here were predictable based on the design of the systems. A proper evaluation of the system - as designed - would have revealed the opportunity for a malfunctioning radio altimeter to cause a reduction to idle thrust in flight.

After the final specification stage, bad fortune was all that was necessary to place this link in the chain of causes.

So, yes, those developers (and again, he does not recognise that the tasks he mentions go far beyond mere 'software development') did get it wrong. Until that 737 began its approach at AMS, they were lucky, not expert.

Lymbo,

Another interesting first post. Investigator or wannabe?

You mentioned
the finding of truth and justice
. If you wish to write so expertly about your chosen topic, you would do well to learn that while 'truth' is at the heart of the topic, 'justice' is for the courts. You, in the Netherlands, probably suffer as much as we do here in France when people confuse justice and safety.
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Old 6th Mar 2009, 19:18
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Stick shaker too late

safta's experiment shows a big hole in the cheese. If normal recovery won't work, then I submit the stick shaker is coming on too late. Mind you the software revisions to account for trim state bodes to be complex. More likely is a revision to stick shaker recovery procedure when the trim is way back. We also have the Buffalo crash to consider.

Up to a couple months ago, nobody would believe that a crew would just sit there while the A/P wound the trim back until the stick shaker came on.

As far as minding the store, usually PF minds the instruments and PM is dividing his time between looking outside and and crosschecking the instruments. But here we have a teaching situation. Possibly a critical portion of those 100 seconds while the speed was deteriorating were consumed by PM giving teaching such that all attention by the junior pilots was focused upon a PM who was not monitoring.
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Old 6th Mar 2009, 19:19
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I used to fly the B737-200 a very long time ago. I seem to remember that one exercise during flt sim refreshers/base checks involved trimming forward (to counter the effects of rising airspeed and thrust induced pitch-up) whilst accelerating, using G/A thrust, from an in-trim, S&L condition at very low airspeed and that during this manoeuvre the tailplane trim jack would stall due high aerodynamic loads generated by the elevator, thus preventing continued nose-down pitch trim operation (a feature of the actual aircraft). To counter this, forward stick pressure would be eased, thus reducing load on the trim jack and hence allowing nose-down trimming to be reapplied. Forward stick pressure would then be resumed to control pitch-up as the aircraft continued to accelerate and the process would have to be repeated a further two or three times, producing a “porpoising” effect, before normal trimming, in concert with forward stick pressure, could be continuously maintained.

Perhaps current and experienced B737 Classic/NG pilots would advise whether my distant memory of this phenomenon is correct and if so is it also a feature of the B737-800? If correct and applicable to the -800, perhaps this unfortunate crew’s finally attempted stall recovery was hampered and ultimately thwarted by a series of accelerated stalls associated with the “porpoising” manoeuvre? I would be very interested to hear the views of experienced B737 pilots on this matter.

PS. If this has been covered previously, please indulge me as I haven’t time for a detailed trawl through the 1660 posts to date.
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Old 6th Mar 2009, 19:23
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safta

We allowed the 8 seconds based on the probability that the crew would have been surprised by the stick shaker and may not have reacted immediately. However, when we attempted recovery we did so with max available thrust but pitch was limited by the available elevator control due to the immense amount of nose up trim.

We were somewhere around 1200 to 1300 feet AGL when we initiated the recovery.
One thousand, two thousand, three thousand, four thousand, five thousand, six thousand, seven thousand, eight thousand. Still seems a long time to allow for the deer in the headlights aspect and the recovery altitude would tend to suggest you did not have anywhere near the same amount of excess speed to bleed off as the accident crew, so being slower you managed to incur enough nose up trim to guarantee an accelerated stall on recovery a lot quicker and higher on the approach than they did.

I wonder if anyone else attempting this could confirm if it is possible to fly the aircraft out of the stall with something less than full power but sufficient to arrest the descent against the nose up trim yet without using so much power that the nose pitches up beyond the capacity of the trim system to maintain a level attitude?
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