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Indonesian aircraft missing off Jakarta

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Indonesian aircraft missing off Jakarta

Old 8th Nov 2018, 23:18
  #861 (permalink)  
 
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Originally Posted by Ken V
I agree this note in the manual is likely not related to this accident. All the data available indicates the accident aircraft was well above stall airspeed for the pressure altitude they were operating in and thus there was plenty of elevator authority available.
I would surmise that with full nose down stab, there is no way any nose-up elevator input would overcome it at normal speeds. The faster you go, the worse it would become. Probably why this aeroplane crashed the way it did. Or do you think the crew just let the nose drop while being occupied with something else?

Originally Posted by Ken V
Agreed, this is unrelated to this accident. All the available data indicate the accident aircraft was well above 1G stall for the pressure altitude and thus they had plenty of elevator authority. Further, that same data does not indicate the engines were at a "high power" setting.
I don't know about your aeroplane, but if I set mine up at low level with the clean UA config power setting, the thing will shortly be going like a rocket.

Last edited by Capn Bloggs; 9th Nov 2018 at 00:58.
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Old 9th Nov 2018, 00:47
  #862 (permalink)  
 
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Originally Posted by Vessbot View Post
The circumstances around this discussion are making me feel glad for the trim cutout buttons being on the yokes on my plane instead of somewhere else you have to reach....
Not a problem for a properly trained crew. For the captain it is close to his right hand and drilled into him in training. For the F/O who has the yoke in his right hand, his left hand is close by to the cutout switch.

This has been working on thousands of 707s, 727s, and 737s, for eons.
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Old 9th Nov 2018, 01:01
  #863 (permalink)  
 
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Originally Posted by gums View Post
@hans

No problem, man. I can take it, as my call sign was assigned to me and I did not choose it.

I opine when not having reams of data, testimony or having been the principle pilot in the incident. So will continue to designate opinion and theory versus asserting facts or lecturing the newbies and non-pilots, as some here do. We have the Tech Log for education as well as opinion and theories.

I have never told a poster “if you had read.......”. I have never brought up the ethnic or religious background of a crew in an accident, and I will bet I have taught more pilots to fly from more countries than you! So there! I got personal, but back to analysis and opinion and experience in these matters to hope we have no more like this one.

out,




Haha! I'm confirming a kill right there Gums. Maintenance have been authorized to record it on the side of your Viper!
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Old 9th Nov 2018, 01:24
  #864 (permalink)  
 
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Originally Posted by DaveReidUK View Post
Yes, that the same defect apparently persisted through four consecutive sectors, and successive crews were in effect testing the outcome of failed rectification attempts, is inexcusable.

That said, an "inherent and unknown programming defect" (in any software environment, not just aerospace) by definition requires a specific, unforeseen combination of factors (possibly including other defects) in order to trigger it. It's entirely possible that the required combination of factors never emerged during the certification process.

If there had been precursors to this issue, while we might not have heard about them prior to the crash, they would undoubtedly have emerged in the last 10 days. AFAIK, none have.
Thank you for some sanity! Late 70's our organization reviewed Airbus testing procedures for FBW SW under development. I'm going purely on dated memory here, but as I recall AB contracted out 3 separate test beds in three countries, none of whom knew of the other's existence, to independenly test FBW software. Each were expected to develop their own test procedures. We reviewed the test results and the rationale for their strategy (not for AB but for an independent program). AB expected that each location would find different 'bugs'. It didn't turn out that way. Well over 90% were identical findings with very little if any (I don't remember any at least) unique critical FBW bugs discovered. That is not the result that they expected.

There were also early and persistent concerns of deep stall potential with the F-16 at high AoA (unrelated to FBW). So I'll ask this question. Did Boeing put in some additional 'safeguards' to prevent a potential reoccurence of AF 447?
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Old 9th Nov 2018, 01:47
  #865 (permalink)  
 
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Originally Posted by aterpster View Post
Not a problem for a properly trained crew. For the captain it is close to his right hand and drilled into him in training. For the F/O who has the yoke in his right hand, his left hand is close by to the cutout switch.

This has been working on thousands of 707s, 727s, and 737s, for eons.
In the possible scenario where it suddenly takes 4 hands to hold the nose up (like what is being speculated here) it would certainly still be a problem.
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Old 9th Nov 2018, 02:33
  #866 (permalink)  
 
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Iím still wondering about the stab trim brake and if it is still in the 737NG.
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Old 9th Nov 2018, 02:55
  #867 (permalink)  
 
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Originally Posted by Vessbot View Post
In the possible scenario where it suddenly takes 4 hands to hold the nose up (like what is being speculated here) it would certainly still be a problem.

There seems to be a reluctance in the industry to realistically quantify the expectation that a crew will be able to follow a recovery procedure.
Human failures whether due to cognitive overload, lack of training, too many sectors, or baby cried last night, are holes in the Swiss cheese exactly like mechanical faults.

The mechanical failures are quantified, while in some strange way maybe connected to liability and legal engineering, crew ability is expected to be perfect.
And if the pointy end can't cut faultless on that day, too bad, they won't make it - nor will the paying freight in the cylindrical end.
But the fact that there was a procedure, however improbable that it can work outside the sim, negates liability. Beancounters happy.

I don't think that the industry is only recruiting clones of Sully.
And btw Sully dealt with a clear mechanical failure, he didn't need to psychoanalyze and then lobotomize HAL in real time.

If real pilots can't RELIABLY deal with dangerously misbehaving automation then maybe the automation needs improving.
Someone over there where they make rules and profits, should be forced to accept that real pilots fly planes.

And the way to make things improve - in the US system - is by attaching liability to a process which only the best or luckiest can follow.

Edmund

Last edited by edmundronald; 9th Nov 2018 at 03:17.
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Old 9th Nov 2018, 03:45
  #868 (permalink)  
 
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Where y'at, Edmund? Hans can figure that greeting out, maybe.

The following is not 100% directed to the Lion crash, but at Edmund's views.

Some great points, and some of us here talked a lot about the AF447 sequence of events and the procedures and many other aspects of that sad story. One thing that seemed to come up over and over was the confusing reversion of control laws. See the thread for more disussion.

My personal view was the 'bus folks tried too hard to preserve "nice" features of the prime control laws as each reversion layer came to be required. So the system did not go from highly automated and protective mode to a basic "manual" set of control laws. In other words, something resembling "hand flying". We pilots should not have to memorize and obey 5 layers of control laws and such when things go awry. A backup law and maybe one more with zero "help" from Hal could be a realistic approach. But to see a buncha layers, go see the Airbus sequence.

/opinion/ Unless your plane is a pure FBW, unstable design such as I flew, then it seems to me we should have some means to quickly and effectively revert to a pure "hand flying" machine if it passes all the agency certification requirements. Otherwise, go as far as you can, but no intermediate steps as we saw in AF447. /opinion off/

Gums...
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Old 9th Nov 2018, 04:42
  #869 (permalink)  
 
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Originally Posted by DaveReidUK View Post
Yes, that the same defect apparently persisted through four consecutive sectors, and successive crews were in effect testing the outcome of failed rectification attempts, is inexcusable.

That said, an "inherent and unknown programming defect" (in any software environment, not just aerospace) by definition requires a specific, unforeseen combination of factors (possibly including other defects) in order to trigger it. It's entirely possible that the required combination of factors never emerged during the certification process.

If there had been precursors to this issue, while we might not have heard about them prior to the crash, they would undoubtedly have emerged in the last 10 days. AFAIK, none have.
This is nonsens. Certification is a desktop exercise. You go through the aircraft systems schematics and make a risk analysis about what if then. It is not about trying to let something emerge.
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Old 9th Nov 2018, 04:48
  #870 (permalink)  
 
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KNKT states AoA sensor replaced on 28TH Oct prior to JT43 flight to Jakarta . but that flight still had issues . So was the sensor probe not the core issue . Could it have been an issue with the mounting . Or something else beyond this . Could the sensor that was replaced be a different part type to the origional . Just asking those of better understanding .
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Old 9th Nov 2018, 04:54
  #871 (permalink)  
 
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There were also early and persistent concerns of deep stall potential with the F-16 at high AoA (unrelated to FBW). So I'll ask this question. Did Boeing put in some additional 'safeguards' to prevent a potential reoccurence of AF 447?
How is Airbus FBW and associated "laws" relevant to discussion about a Boeing 737 crash?
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Old 9th Nov 2018, 04:56
  #872 (permalink)  
 
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Originally Posted by b1lanc View Post
Thank you for some sanity! Late 70's our organization reviewed Airbus testing procedures for FBW SW under development. I'm going purely on dated memory here, but as I recall AB contracted out 3 separate test beds in three countries, none of whom knew of the other's existence, to independenly test FBW software. Each were expected to develop their own test procedures. We reviewed the test results and the rationale for their strategy (not for AB but for an independent program). AB expected that each location would find different 'bugs'. It didn't turn out that way. Well over 90% were identical findings with very little if any (I don't remember any at least) unique critical FBW bugs discovered. That is not the result that they expected.

There were also early and persistent concerns of deep stall potential with the F-16 at high AoA (unrelated to FBW). So I'll ask this question. Did Boeing put in some additional 'safeguards' to prevent a potential reoccurence of AF 447?
This software scenario is not applicable in this case. This is an aircraft systems design issue as simple as: two out of two sensors show different data. This has nothing to do with software. It is a conceptional issue. Anything in an aircraft that is able to drive primary control elements should never be able to be triggered by a non-majority vote. This is simple basics.

It is also very surprising that an AOA difference display is on the list of options only. This is a pure up-selling concept to make more profit. It has nothing to do with incremental costs during manufacturing.

The whole "the aircraft design is safe", "the manufacturer did a good job", "well trained pilots would have recovered", "maintenance did a bad job", "third world habits" is arrogant and very biased to say the least. This accident happened in the aviation world of FAA certification processes that cost taxpayers and aircraft buyers millions.
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Old 9th Nov 2018, 04:57
  #873 (permalink)  
 
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Old 9th Nov 2018, 05:14
  #874 (permalink)  
 
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Perhaps I am missing something here as this technical discussion is quite esoteric but Boeing advise ...."failure condition that can occur during manual flight only." The bolding from Boeing.

So all this discussion around pilots being under skilled and not being able to sort out an issue after disconnected the AP becomes even more interesting as the FCOM bulletin suggests that if the AP was flying the issue would have been resolved? Perhaps there is more significant information to come, perhaps once the FDR information has been released. At this stage it is about PR departments getting in with their version to bias the discussion to suit corporate aims.
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Old 9th Nov 2018, 05:17
  #875 (permalink)  
 
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How can "Automatic disengagement of autopilot" be an effect from AOA disagree, if the failure condition "can occur during manual flight only"?
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Old 9th Nov 2018, 05:19
  #876 (permalink)  
 
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Originally Posted by Icarus2001 View Post
Perhaps I am missing something here as this technical discussion is quite esoteric but Boeing advise ...."failure condition that can occur during manual flight only." The bolding from Boeing.

So all this discussion around pilots being under skilled and not being able to sort out an issue after disconnected the AP becomes even more interesting as the FCOM bulletin suggests that if the AP was flying the issue would have been resolved? Perhaps there is more significant information to come. perhaps once the FDR information has been released. At this stage it is about PR departments getting in with their version to bias the discussion to suit corporate aims.
The failure condition evolved in manual flight right after take-off. The bulletin states: "Inability to engage AP"
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Old 9th Nov 2018, 05:43
  #877 (permalink)  
 
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The failure condition evolved in manual flight right after take-off.
How do you know this ? Or are you just surmising from the FR data?
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Old 9th Nov 2018, 05:44
  #878 (permalink)  
 
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Originally Posted by threemiles View Post
How can "Automatic disengagement of autopilot" be an effect from AOA disagree, if the failure condition "can occur during manual flight only"?
When you fly on autopilot. AoA disagree causes autopilot to disengage. It won't engage back so you are now in manual flight only. Then, stab trim runs away in manual flight only.
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Old 9th Nov 2018, 05:57
  #879 (permalink)  
 
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Ever since AF447, 'IAS Disagree' has been front and centre of emergency training. Quite possibly on this flight the AOA issue generated an IAS Disagree message and the crew (quite reasonably) carried out the IAS Disagree checklist. The first step of which is to disconnect the autopilot and fly manually. Now the door is open for the uncommanded stab trim problem to rear it's ugly head.
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Old 9th Nov 2018, 06:07
  #880 (permalink)  
 
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Bleve,

And my belief is that when the crew started to fly manually they might well have found themselves having to cope with the 'yo-yo' manoeuvres described by Centaurus in a previous post (I quote him in italics below) while perhaps also being distracted by multiple warnings as described in the recent Boeing bulletin.

"Excessive air loads on the stabilizer may require effort by both pilots to correct mis-trim. In extreme cases it may be necessary to aerodynamically relieve the airloads to allow manual trimming."

To relieve airloads, the crew must momentarily release all backward pressure on the elevator then rapidly wind the stabilizer trim backwards manually or electrically. In turn, this allows more effective elevator control. In other words, a yo-yo manoeuvre. The crew needed to react instantly and correctly to relieve air loads in this manner. Unfortunately, the Lion Air crew did not have the altitude to successfully recover before impact.


If that was the case, I wonder how well many of us would have coped in that situation.
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