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Indonesian aircraft missing off Jakarta

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Indonesian aircraft missing off Jakarta

Old 18th Nov 2018, 10:44
  #1381 (permalink)  
 
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Originally Posted by wiedehopf View Post
There can't be consensus in speculation.
Read the thread for that speculation.

...............
Apart from that you will have to wait for the report.
oh yes, I've read the thread, seen all the speculation. I have trouble putting it in correct context.

I await the report, like everyone, with great interest.
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Old 18th Nov 2018, 11:05
  #1382 (permalink)  
 
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Clear 2 X, #1387. An investigation should not fall back on blaming the human at any level of organisation, regulation or design. The phrase ‘I do not understand’ should trigger the need to look elsewhere, the process, interactions, and assumptions.
A significant safety fallacy is that where a complex situation has been managed on previous flight(s) then it will be on subsequent flights; except this judgement is based on assumptions such as a covert ‘I do not understand’. (Compare with AF447, 737 AMS, 777 Asiana, CRJ Sweden)
Hindsight is a powerful bias. In your view above, it might be better ask if the operator, maintenance, or customer support had any greater knowledge of the system than the pilots may have had.

It would be unfortunate if the manufacturer’s design philosophy of keeping the ‘pilot in control’ has in this instance been translated as ‘the pilot will always manage’. If so, perhaps a poorly applied assumption or weak human factors assessment - a drift from the original safety concepts.
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Old 18th Nov 2018, 11:50
  #1383 (permalink)  
 
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Originally Posted by clearedtocross View Post
This thread contains a lot of interesting and intelligent proposals to improve pilot training, aircraft system design and certification procedures. But even with all these things still further improved (which is ok of course), modern jets like all other complex systems will go on to produce odd quirks, bugs and failures. Troubleshooting by pilots and maintenance does not get easier with added complexity and some basic failures like a malfunctioning sensor get camouflaged by quadruple redundant systems, voting algorithms, Kalman filters, Fuzzy Logic, Artificial Intelligence and you name it. We all know this.

But what I cannot understand is why an airline organisation does not prevent loading poor SLF and non-pilot crew into an aircraft that had serious problems documented on the three previous flights. This without a thorough assessment of the problem(s) on ground, corrective action and then some test flights by crews prepared for dealing with such problems. That is the real killer in this instance, and not missing pilot knowhow or design/certification flaws. Airworthiness is not only about stamps and signatures on some forms. As a lowly aircraft owner and pilot I will not take along passengers for a ride if my aircraft is plagued by unresolved troubles or untested repairs of such. And I hope the airline I buy my next ticket as a passenger will not do so either. Then I will embark with confidence, be it a Boeing, Airbus, Embraer et altera.
Unlike earlier versions of B737, the 737 MAX has an extensive and powerful troubleshooting data generated in each and are available to engineers on ground. See the link below for some of the information and screen shots. This is not for the layman of course. These pages are similar to B777 on which I have trained and worked for nearly 2 decades. Each new aircraft comes with new and additional tools for engineers. A380 is far more advanced than B777 in this area. I am sure when B777X comes out in 2020 it will go further forward.
It is one thing to have these advanced systems, but if engineers troubleshoot like older aircraft, it will be hit and miss. (As you and some others have pointed out). There lies the danger.
It is too early to say what went wrong in this case other than the fact that several holes in the cheese aligned perfectly.
Though it is harsh to comment on maintenance performed with little available info, I am compelled to say that what LION air engineers did, I would have never done. This aircraft had repeated airspeed and AoA faults. The aircraft was certified by replacing one component (ADM). The nature of this defect demand engineers to test the pitot/static system with what is called an Air-data tester, which takes the instruments through full range of a flight profile and readings are compared with a calibrated source instruments. It is commonly used in all airlines and is as old as aviation. But we are not sure if Lion air used this tester, as the tech log write-up does NOT mention it, and it means they have not used it. Similarly AoA sensor has a tester. These have to be used to confirm primary instruments on which pilots depend.
The repeat nature of defects in a vital system affecting flight controls, has to treated and dealt with differently. This was a fit case for pulling the machine from service for a thorough check and probably even a test flight before releasing to line flying. Test flights are usually done by a senior pilot qualified for it and he will be trained to expect the unexpected.You can see even in this airline, some pilots managed to assess, correct and carry-on flying. But unfortunately the last one did not succeed.

Hope what I said above makes sense. Let us wait for the complete report, it is one of those intriguing accidents on a brand new aircraft, which should never have happened.

Boeing 737 MAX Onboard Maintenance Function
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Old 18th Nov 2018, 11:59
  #1384 (permalink)  
 
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Re the video displayed by JPJP post 1381 where a 37,000 ft stall recovery is shown.

There was no mention by the instructor to his student what safe IAS should be attained in the recovery dive before any attempt is made to level out. In the video, it appears the student was trying to recover with minimum loss of height. Hence the several secondary stick shakers caused by the student trying to minimise height loss.

Using Vref 40 plus 100 knots as a safe speed to level out, the aircraft should be kept in the recovery manoeuvre (nose on the horizon or slightly lower) until that speed is attained and only then should the aircraft be gently eased out of the dive without risk of G stalling.

If the aircraft is in severe turbulence during recovery, the aircraft should be kept in the recovery dive until Severe Turbulence airspeed/.Mach is reached - then levelled out. Expect 3000 feet of height loss during recovery manoeuvre or 5000 ft loss if in severe turbulence
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Old 18th Nov 2018, 16:01
  #1385 (permalink)  
 
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Did MCAS replace STS on the max or is it another feature besides STS?
Thx
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Old 18th Nov 2018, 17:03
  #1386 (permalink)  
 
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Originally Posted by gearlever View Post
Did MCAS replace STS on the max or is it another feature besides STS?
Thx
In terms of operationally, looking for changes/differences docs I haven't seen anything that suggests STS has been removed or changed, and since MCAS wasn't documented at all...

The actual hardware or software implementation is a different matter - STS (previously implemented by the FCC) might have been replaced by something new that does STS and MCAS but the STS bit behaves the same as old STS. However, given that the intent was to change as little as possible, I think it is more likely that MCAS is an additional feature besides, either additional hardware or just software.

There does seem to have been some hardware change though - further up the thread there is an image showing that the two Trim CutOut switches have changed, both labelling and functionality. Where before there was one switch to cutout the control column trim switch and one to cutout the automatic (labelled as "autopilot" but actually the autopilot and the manual-flight STS signals used the same circuit), now there are two switches (primary and backup) which cut both. This means there have been changes, suspect related to MCAS and possibly significant in this event, to the physical architecture. What those changes are we don't yet know, from public info.
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Old 18th Nov 2018, 17:15
  #1387 (permalink)  
 
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Insler said it’s premature to say anything about the cause of the Lion Air crash. “I don’t jump to conclusions,” he said.
“The story here is not why we didn’t know about (the new system), it’s why the pilots didn’t fly the plane,” said Insler.
United pilots should be looking for another Union rep. Embarrassing.
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Old 18th Nov 2018, 17:24
  #1388 (permalink)  
 
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Originally Posted by gearlever View Post
Did MCAS replace STS on the max or is it another feature besides STS?
Thx
Both STS and MCAS are present in B737 MAX. STS is for speed stability of the aircraft as the Center of Pressure moves as aircraft speed increases. This moves the stab for an aircraft Nose Up direction.This operates on every flight as aircraft accelerates.
MCAS operates only if the AoA of aircraft is sensed as high and this moves the Stab for aircraft Nose down trim.
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Old 18th Nov 2018, 19:03
  #1389 (permalink)  
 
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It "seems: to me (please correct, or ignore, as appropriate) possible that a single sensor failure could trigger both UAS _and_ (pseudo) THS runaway, more or less at the same time. I write "pseudo" because apparently it does not run continuously ... but will come back doing it later ... perhaps making it even more difficult to identify. If true, it is my impression that there should be explicit dedicated training for that particular failure mode.
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Old 18th Nov 2018, 21:47
  #1390 (permalink)  
 
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Originally Posted by pax2908 View Post
It "seems: to me (please correct, or ignore, as appropriate) possible that a single sensor failure could trigger both UAS _and_ (pseudo) THS runaway, more or less at the same time. I write "pseudo" because apparently it does not run continuously ... but will come back doing it later ... perhaps making it even more difficult to identify. If true, it is my impression that there should be explicit dedicated training for that particular failure mode.
That’s an interesting catch. If MCAS senses (erroneous) AoA, and pilot catches the “runaway” within the first ten seconds, and starts to wind trim back, when MCAS “stops”, he will crank in unnecessary NU trim, then as MCAS begins a second cycle, well, you get the point, if the pilot is unaware of the function and intermittent cycle, he will chase the trim. FAIL TRIM induced Porpoise! Without specific knowledge of the operation’s cyclic timing, well, don’t try to tame the beast you don’t know.

The fact remains, Boeing gave no chance to the pilot group to “train” the abnormal.



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Old 18th Nov 2018, 22:21
  #1391 (permalink)  
 
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There's a well written CNN article that describes the issues surrounding this event and the lack of information around MCAS.

In particular one learns that Lion Air has ordered $21 Billion of Max 8 737 Boeing jetliners in 2011, and another 6 Billion worth of Max 9 and Max 10 this year. That's real money. One could assume that Lion Air would expect to be a priority recipient of training information concerning these airframes.

Speaking as someone who has 20 years experience as a journalist, I'd say that a lot of people in high places in the industry and regulatory agencies must be very upset about this event for CNN not to whitewash Boeing as they usually would, and take the trouble to generate this very carefully researched and written piece.

Edmund
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Old 18th Nov 2018, 23:15
  #1392 (permalink)  
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The first thing that leaps out at me from the CNN write-up is the dichotomy of views from named senior union officials. From 'a betrayal of trust' (in a professional relationship with Boeing) to 'the information was there'.

Well worth reading.
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Old 18th Nov 2018, 23:27
  #1393 (permalink)  
 
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Originally Posted by Loose rivets View Post
The first thing that leaps out at me from the CNN write-up is the dichotomy of views from named senior union officials. From 'a betrayal of trust' (in a professional relationship with Boeing) to 'the information was there'.

Well worth reading.
Mr. Rivets: How is “the information was there” a defense? It is not wrong, but unless the link to MCAS specifically is established by Boeing via the FCOM, it is deceitful....!

Boeing said that immediately, that they had referred the pilots to “established procedures”......

“A half Truth is a Whole lie....” Confucius....

Last edited by Concours77; 19th Nov 2018 at 00:13.
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Old 18th Nov 2018, 23:29
  #1394 (permalink)  
 
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Originally Posted by Loose rivets View Post
The first thing that leaps out at me from the CNN write-up is the dichotomy of views from named senior union officials. From 'a betrayal of trust' (in a professional relationship with Boeing) to 'the information was there'.

Well worth reading.
IMO- Mullenberg and a certain union president should find another job or retire. Both made BS statements- which will likely be proven to be wrong wrong wrong . . .or at the best deliberately misleading.
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Old 19th Nov 2018, 05:18
  #1395 (permalink)  
 
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Originally Posted by Loose rivets View Post
The first thing that leaps out at me from the CNN write-up is the dichotomy of views from named senior union officials. From 'a betrayal of trust' (in a professional relationship with Boeing) to 'the information was there'.

Well worth reading.
Hilarious.

The United ALPA Chairmen seems to have omitted any experience in the 737 from his extensive Bios and sunglass wearing videos. He’s apparently unable to leave ALPA politics out of a professional discussion that affects the safety of his members and their passengers. United has zero MAX 8 aircraft. Of the three U.S. airlines included in the article, United has the least experience with the aircraft. United received their first MAX9 aircraft four months ago.

MCAS wasnt included in the United Airlines MAX9 Flight Crew manuals.


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Old 19th Nov 2018, 06:46
  #1396 (permalink)  
 
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Concours, #1401. As an example of attitudes towards pilots after an accident, see the NTSB, FAA, Boeing, submission of the AMS 737 accident.
A defensive approach, resorting to the difference between what was expected, what was done, what was demonstrated in certification and that recorded in operation, accidents / incidents.
Appendix B http://reports.aviation-safety.net/2...738_TC-JGE.pdf ~ page 139

Potential similarities with this accident - concluding recommendations ~ page 13.
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Old 19th Nov 2018, 12:43
  #1397 (permalink)  
 
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Originally Posted by Concours77 View Post


That’s an interesting catch. If MCAS senses (erroneous) AoA, and pilot catches the “runaway” within the first ten seconds, and starts to wind trim back, when MCAS “stops”, he will crank in unnecessary NU trim, then as MCAS begins a second cycle, well, you get the point, if the pilot is unaware of the function and intermittent cycle, he will chase the trim. FAIL TRIM induced Porpoise! Without specific knowledge of the operation’s cyclic timing, well, don’t try to tame the beast you don’t know.
abnormal.
I'm not sure if I am totally barking up the wrong tree here, but there may be another possibility to consider as well:

What happens if MCAS and STS are both active? We have no information as to how they interact in that case, whether one system inhibits the other, whether outputs are summed or or-ed, whether the reactivation timers are identical and in-sync or not.

As I understand it, if speed (data) is increased STS will trim nose up, if AOA (data) is high MCAS will trim nose down, what if both? If the activation times are different the trim will be up then down, which might lead to a report of "sts trimming wrong way" in absence of knowledge of MCAS, no? So the pilot might be fighting an aircraft that is porpoising all on it's own. Note that this may not look like a classic "runaway trim" either, it isn't at this point running away in either direction.

Now if speed is reduced, will STS and MCAS (assuming indicated AOA remains high) both trim nose down, depending on the cyclic timing, possibly suddenly and at the same time (additive commands? - we don't know)?


But like I said, I may be totally barking up the wrong tree and have misunderstood STS/MCAS.
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Old 19th Nov 2018, 13:38
  #1398 (permalink)  
 
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Originally Posted by infrequentflyer789 View Post
I'm not sure if I am totally barking up the wrong tree here, but there may be another possibility to consider as well:

What happens if MCAS and STS are both active? We have no information as to how they interact in that case, whether one system inhibits the other, whether outputs are summed or or-ed, whether the reactivation timers are identical and in-sync or not.

As I understand it, if speed (data) is increased STS will trim nose up, if AOA (data) is high MCAS will trim nose down, what if both? If the activation times are different the trim will be up then down, which might lead to a report of "sts trimming wrong way" in absence of knowledge of MCAS, no? So the pilot might be fighting an aircraft that is porpoising all on it's own. Note that this may not look like a classic "runaway trim" either, it isn't at this point running away in either direction.

Now if speed is reduced, will STS and MCAS (assuming indicated AOA remains high) both trim nose down, depending on the cyclic timing, possibly suddenly and at the same time (additive commands? - we don't know)?

But like I said, I may be totally barking up the wrong tree and have misunderstood STS/MCAS.
YEP, looks like you have opened a a can of worms.
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Old 19th Nov 2018, 18:36
  #1399 (permalink)  
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Yes, systems in opposition are the stuff of nightmares.

I recall a vast harness coming out of an aircraft in Toulouse and being told (words to the effect) that these two brains would be talking to each other for another two days. I felt incredibly removed from those electronic minds.
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Old 19th Nov 2018, 20:24
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Originally Posted by Loose rivets View Post
The first thing that leaps out at me from the CNN write-up is the dichotomy of views from named senior union officials. From 'a betrayal of trust' (in a professional relationship with Boeing) to 'the information was there'.

Well worth reading.
Would be interesting to know if SW changing two AoA sensors was the result of crews experiencing flight anomalies prior.
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