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Indonesian aircraft missing off Jakarta

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Indonesian aircraft missing off Jakarta

Old 28th Nov 2018, 13:10
  #1741 (permalink)  
 
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Originally Posted by phil gollin View Post
That confuses me. When the PIC transferred control to the SIC SURELY the runaway trim should have stopped as the SIC's controls would be using the input from the correct AoA sensor ?

Why did it continue ?

.
This confuses me. The 737 (all versions) has direct mechanical flight controls (hydraulically assisted). They have no provision for "using" air data of any kind, except for the strength of the artificial feel system, which depends on airspeed (measured by an independent system.)

Even in the fly-by-wire A320 the flight control computers don't really care who makes the inputs. All computers evaluate inputs from both sticks and air data from all available sensors (indirectly via the ADIRUs).

The MCAS is also completely independent of pilot inputs (except trim inputs, but that only inhibits it for 5 seconds), and no system (except possibly force sensors at the control columns themselves) "knows" which pilot is making inputs. Sometimes both do, especially in cases of a badly mis-trimmed aircraft.

Bernd
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Old 28th Nov 2018, 13:10
  #1742 (permalink)  
 
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Originally Posted by AGBagb View Post
From the Synopsis (quoted above) of today's Interim Report, about the previous flight:

The PIC noticed the aircraft was automatically trimming AND. The PIC moved the STAB TRIM switches to CUT OUT and the SIC continued the flight with manual trim without auto-pilot until the end of the flight.
​​​​​​And here's a good example of the problem with relying on synopses, executive, summaries and the like; sometimes they leave really important stuff out.

In the body of the report between 'The PIC noticed that as soon the SIC stopped trim input, the aircraft was automatically trimming aircraft nose down (AND).' and '... the PIC moved the STAB TRIM switches to CUT OUT.' there is, inter alia, this line;

After three automatic AND trim occurrences, the SIC commented that the control column was too heavy to hold back.
(My bolding)

If you look at the version of FDR data presented to the Indonesian parliament (but curiously not in the preliminary report) it details control column force measurements. At the onset of JT43's MCAS event the control column forces rise rapidly to around 85 (out of 100) of whatever the units of measure are (can someone comment on that parameter and the units of measure?). In normal flight the forces bounce around in the 5 - 15 range so I'm assuming that 85 is, well, attention grabbing. For JT610, until the terminal 90 seconds or so, the forces never get above 50 units and tend to bounce around the 25 mark. I suspect that it was the control column forces that prompted the STAB TRIM switches being moved to CUT OUT on JT43, something that probably didn't occur on JT610 until the terminal (too late) phase.

It is one of a couple of differentiating factors that you can put down to JT43's decision to maintain their climb while dealing with their problem and JT610's decision to level off at 5,000 feet to deal with theirs. I strongly suspect that the latter was part of a briefed plan to deal with a possible UAS on take-off. I don't think that it is happenstance that JT610 '... requested approval to the TE controller “to some holding point”' as well as advising '... the TE controller that the intended altitude was 5,000 feet.' and that they re-retracted flap at 5,000 feet. There is level flight pitch and power data for holding, flaps up at 5,000 feet in the Flight With Unreliable Airspeed tables. In fact, 5,000 feet is the lowest altitude for which there is data for level flight.
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Old 28th Nov 2018, 13:25
  #1743 (permalink)  
 
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Originally Posted by Rated De View Post
Precisely.

Given the CVR has not been recovered the only two people that definitively know exactly what transpired cannot defend themselves, is it not wiser to resist the arrogance afforded by 100% hindsight and wait for the CVR to be found?
Thank you Semreh, far more eloquently put.
By that reasoning a conclusion and probable cause is not possible without recovery of a readable CVR.
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Old 28th Nov 2018, 13:33
  #1744 (permalink)  
 
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Originally Posted by DaveReidUK View Post
There's no explicit mention of the flying spanner in the Preliminary Report, suggesting that he/she was not on the flight in any kind of pre-assigned troubleshooting role.
Maybe this was the engineer, logged as a crew member....

Originally Posted by AGBagb View Post
The Preliminary Report (78 pages) linked to above is a very slow download this morning. ........

4 SAFETY RECOMMENDATIONS
The KNKT acknowledges the safety actions taken by Lion Air and considered that the safety actions were relevant to improve safety, however there still safety issue remain to be considered. Therefore, the KNKT issued safety recommendations to address safety issues identified in this report.
4.1 Lion Air Lion AirLion Air
04.O-2018-35.1
Refer to the CASR Part 91.7 Civil Aircraft Airworthiness and the Operation Manual part A subchapter 1.4.2, the pilot in command shall discontinue the flight when un-airworthy mechanical, electrical, or structural conditions occur.
The flight from Denpasar to Jakarta experienced stick shaker activation during the takeoff rotation and remained active throughout the flight. This condition is considered as un-airworthy condition and the flight shall not be continued.
KNKT recommend ensuring the implementation of the Operation Manual part A subchapter 1.4.2 in order to improve the safety culture and to enable the pilot to make proper decision to continue the flight.
04.O-2018-35.2
According to the weight and balance sheet, on board the aircraft were two pilots, five flight attendants and 181 passengers consisted of 178 adult, one child and two infants. The voyage report showed that the number of flight attendant on board was six flight attendants. This indicated that the weight and balance sheet did not contain actual information.
KNKT recommend ensuring all the operation documents are properly filled and documented.
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Old 28th Nov 2018, 13:37
  #1745 (permalink)  
 
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It is very unusual for Boeing to comment on this report given the investigation is ongoing?

https://www.flightglobal.com/news/ar...minary-453970/
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Old 28th Nov 2018, 13:54
  #1746 (permalink)  
 
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I'm long retired and although I flew earlier models of the 737, I'm certainly not in the loop with this version. I have not had a chance to go through the full report. I read in one of the posts that the speed was 300+ kts and unless I've missed previous comments about this I'm surprised no one appears to have observed on this..... with a flight control problem the problems are greatly increased with so much speed and I would have thought they would have slowed to a more manageable speed. I know there was a lot going on and the numerous warnings going non-stop can be very distracting, but reduced IAS would have greatly reduced the control forces that they needed to use . I do understand that they were getting stall warnings and I would presume the stick shaker was active, but setting a thrust that would give a speed for arguments sake of 250 or so might have bought them more time and a better resolution to this might have been achieved....
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Old 28th Nov 2018, 13:57
  #1747 (permalink)  
 
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Originally Posted by climber314 View Post
It is very unusual for Boeing to comment on this report given the investigation is ongoing?

https://www.flightglobal.com/news/ar...minary-453970/
Yes, it might have something to do with Boeing having just had their worst three week's trading in probably the past decade. In the two weeks from the FAA's release of their emergency AD on 7 November their share price was down about 14.5 per cent and they lost over $31B in market capitalisation. That sort of thing tends to galvanise Boards.

They've recovered some of that over the past three days to be down around 12.7 per cent since the 7th.
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Old 28th Nov 2018, 13:59
  #1748 (permalink)  
 
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Originally Posted by AGBagb View Post
The Preliminary Report (78 pages) linked to above is a very slow download this morning. And many press reports of it are - imho - based on the press releases accompanying it, not the text itself. So, here's the Synopsis section of the English version of the original document (p. vii), followed by the Safety Recommendations (p.27). .......

4 SAFETY RECOMMENDATIONS
The KNKT acknowledges the safety actions taken by Lion Air and considered that the safety actions were relevant to improve safety, however there still safety issue remain to be considered. Therefore, the KNKT issued safety recommendations to address safety issues identified in this report.
4.1 Lion Air Lion AirLion Air
04.O-2018-35.1
Refer to the CASR Part 91.7 Civil Aircraft Airworthiness and the Operation Manual part A subchapter 1.4.2, the pilot in command shall discontinue the flight when un-airworthy mechanical, electrical, or structural conditions occur.
The flight from Denpasar to Jakarta experienced stick shaker activation during the takeoff rotation and remained active throughout the flight. This condition is considered as un-airworthy condition and the flight shall not be continued.
KNKT recommend ensuring the implementation of the Operation Manual part A subchapter 1.4.2 in order to improve the safety culture and to enable the pilot to make proper decision to continue the flight.
.......
What a strange recommendation. Leaving aside the fact that this aircraft flew multiple sectors with similar defects and whether this should have resulted in diversions or not, how can any pilot make a proper decision to continue on a flight based on this guidance? As the flight crew cannot measure 'airworthiness', then any mechanical, electrical or structural condition on the aircraft will lead to a diversion. Genny tripped off? => divert; lightning strike? => divert; UAS? => divert

Surely that is what the QRH is for - if it tells the crew to 'land as soon as possible' then Boeing consider the airworthiness is at stake. If the QRH leads to the condition being manageable, then why question the airworthiness?
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Old 28th Nov 2018, 14:22
  #1749 (permalink)  
 
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Re Boeing Comment, Flight Global, #1753
A somewhat disingenuous response from Boeing, typical of an attempt to downplay the validity of a formal report and offload responsibility to operators and crew (cf 737 AMS report Annex B).

The comments about AoA vanes are irrelevant, because even with the changed part the problem remained. Are there differences between new and refurbished parts? Does the Max use a different version? Do operators know?

Boeing introduces MCAS into the situation as though it were a known feature. Then refers to the runaway trim drill as though this advice should have been ‘deduced’ as relating to MCAS, but that information was only published after the accident.
Pilots did not know about MCAS; did the engineers, is there any specific trouble shooting guide for multiple disagree messages and trim problems, and relating this to MCAS?
There is no reference to a tech fault log for ‘MCAS FAULT’ as there are for Speed Trim, or Mach Trim; does such a parameter exist?
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Old 28th Nov 2018, 14:56
  #1750 (permalink)  
 
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Originally Posted by FiveGirlKit View Post
What a strange recommendation. Leaving aside the fact that this aircraft flew multiple sectors with similar defects and whether this should have resulted in diversions or not, how can any pilot make a proper decision to continue on a flight based on this guidance? As the flight crew cannot measure 'airworthiness', then any mechanical, electrical or structural condition on the aircraft will lead to a diversion. Genny tripped off? => divert; lightning strike? => divert; UAS? => divert

Surely that is what the QRH is for - if it tells the crew to 'land as soon as possible' then Boeing consider the airworthiness is at stake. If the QRH leads to the condition being manageable, then why question the airworthiness?
I don't want to be that guy that said "that would never happen to me", I just hope I would be able to handle the problem. As a flight crew you should be trained/have experience to "measure airworthiness" in cases where there is no direct guidance from the QRH. Lightning strike but all electronics remained online and all systems still work: continue, Gen tripped off but I have 2 or 3 more: continue, or only one remaining for night flight without close diversion airport: divert, UAS with stick shaker and un-commanded trim inputs: DIVERT. Just last week I heard a B737 declare an emergency due to airspeed disagree, and divert back, luckily there was nothing in the news so I can assume they landed without problems, but to continue with the stick shaker going of IMHO isn't good (yes, that crew did a great job saving the plane, but I do feel they made it harder for the next crew by not grounding the airplane and continuing).
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Old 28th Nov 2018, 15:06
  #1751 (permalink)  
 
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Originally Posted by Stone69 View Post
I'm long retired and although I flew earlier models of the 737, I'm certainly not in the loop with this version. I have not had a chance to go through the full report. I read in one of the posts that the speed was 300+ kts and unless I've missed previous comments about this I'm surprised no one appears to have observed on this..... with a flight control problem the problems are greatly increased with so much speed and I would have thought they would have slowed to a more manageable speed. I know there was a lot going on and the numerous warnings going non-stop can be very distracting, but reduced IAS would have greatly reduced the control forces that they needed to use . I do understand that they were getting stall warnings and I would presume the stick shaker was active, but setting a thrust that would give a speed for arguments sake of 250 or so might have bought them more time and a better resolution to this might have been achieved....
That would be the logical thing to do. Recognizing that repeated uncommanded trim movements occurring in a regular pattern are indeed "continuous" would be another. Both actions would require logical thinking and what we used to call "flying by the seat of one's pants." Reading this thread it appears these concepts have died in favor of computers and checklists.

Is "it wasn't done because there's no checklist for it" a valid defense strategy? It appears Boeing's "Legal Eagles" are chomping at the bit to test that line in court with a long line of expert witnesses. First in that line will be the surviving Lion Air crew that took the appropriate action on the previous flight(s). The depositions would make compelling reading and something we are unlikely to ever see if the case even gets that far.

Once cockpit control is ceded to the realm of 1's and 0's, pilots become obsolete. Be careful what you wish (advocate) for.
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Old 28th Nov 2018, 15:50
  #1752 (permalink)  
 
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Originally Posted by PEI_3721 View Post
bsieker, #1759
Perhaps ‘changed sides’ refers to earlier discussions, to be confirmed, that the ‘side’ of AoA input changed automatically between flights after WoW operation.
If this is so then perhaps there would have been a change in MCAS behaviour between flights, vice the apparent ‘single side’ problems of speed display and stick shake, which could be into separate FCCs.
Over to tech log; would maintenance checks reset this feature
From NG AMM, FCC BITE test would appear to set/reset the master "side", other BITE tests might do too. I don't think we can say for sure that the maintenance checks done would have reset it, but we can't rule it out.
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Old 28th Nov 2018, 15:55
  #1753 (permalink)  
 
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Stone69, climber314,
The speed increase would be more likely (logical) where the focus of attention was towards the indications of low / min speed and stickshake, and possibly UAS.

Re ‘continuous’, no doubt the lawyers will play with words, but MCAS’s 10 sec on and 5 sec off is not continuous - it’s cyclic.
The preceding flight associated the trim movement with STS, a normal function, but the crew did identify an incorrect direction; thus after investigation, flap cycling, the trim was disabled. Tech log ‘logicaly’ associated the STS problem with speed disagree.
There is nothing in these actions, lines of thought, which would be given to the accident crew, who effectively started agin after maintenance on speed / AoA related issues.

In all of the flights the MCAS was operating as designed. It was the failure of a system input (AoA) which caused inappropriate trim movement, and several significant alerts which distracted from the problem.
Technology worked as designed, but the design did not work for the pilot in the event of a minor, un-annunciated input failure.

Furthermore, these issues could be reflected in maintenance. All reports and crew discussion guided fault finding towards speed / AoA, feel, and Speed/Mach trim. The relevant systems were checked/changed.
Ground test would be difficult; MACS trim only operates in the air, with flaps up, with the controls powered, and the control column unloaded. AoA input depends on the vane position, logically identical on the ground/no airflow, thus MCAS could have tested as designed (we don’t yet know if the physical vanes were split or just the electrical signal).
And who would know about MCAS? Pilots have a differences course; no new/changed drills or actions - info only, except there was none. Does maintenance have a difference course, is this mandated, what information would it convey?

Thanks iff789, - reset, if so then a ‘standard practice’ of swapping / changing sensors to aid fault finding would be worthless - self defeated by the BITE check ( which presumable did not provide and help). A ‘wicked problem’ to solve.



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Old 28th Nov 2018, 16:10
  #1754 (permalink)  
 
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Interesting that the Safety recommendations criticise the pilots of the flight before the final one for continuing to destination, but approve Lion Air's actions leading up to that flight and the next, not offering any advice as to whether the airline should have continued flying through four successive dangerous flights.
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Old 28th Nov 2018, 16:47
  #1755 (permalink)  
 
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Originally Posted by vaneyck View Post
Interesting that the Safety recommendations criticise the pilots of the flight before the final one for continuing to destination, but approve Lion Air's actions leading up to that flight and the next, not offering any advice as to whether the airline should have continued flying through four successive dangerous flights.

Is it possible that the between flights maintenance was not based on FDR analysis but instead solely on the brevity of the previous crews report ?
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Old 28th Nov 2018, 17:53
  #1756 (permalink)  
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I mentioned back in #1714 that the pitch up with the large fuel flow may have been a distraction in those last moments, but is it conceivable that they applied a mass of power to do exactly that, given that other things weren't working?

Indonesian aircraft missing off Jakarta

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Old 28th Nov 2018, 18:35
  #1757 (permalink)  
 
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Originally Posted by climber314 View Post
It is very unusual for Boeing to comment on this report given the investigation is ongoing?

https://www.flightglobal.com/news/ar...minary-453970/
I suspect Boeing cleared the press release with the NTSC prior to release (remember, Boeing is party to the investigation so there is ongoing communications). And it really doesn't say anything new - just reiterates whats in the report.

Mick, I wouldn't read much into Boeing's stock performance - the last month has been pretty rough on the market as a whole - Apple for example is down much worse than Boeing (on a percentage basis). I no longer have any Boeing stock in my small portfolio, and as of yesterday my portfolio was down over 10% in the last month (I sold off the last of my Boeing stock when it hit 390 ).
Plus, Boeing is still well above where it was 12 months ago (270) - the recent retreat was from an all time high...
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Old 28th Nov 2018, 18:46
  #1758 (permalink)  
 
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In all the string of maintenance actions prior to the accident flight, who was analysing and determining the steps required. Did the operator contact Boeing Support for advice for a repeated problem not being solved after following the standard procedures. There must have been a considerable cost in labour and parts in doing all the preceding actions, on a brand new airframe which is presumably still under manufacturers' warranty.
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Old 28th Nov 2018, 20:11
  #1759 (permalink)  
 
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FDR of previous flight

Can someone please explain to me how to following can be possible:

The report says that during the flight previous to the accident flight, "The PIC moved the STAB TRIM switches to CUT OUT and the SIC continued the flight with manual trim without auto-pilot until the end of the flight." That’s clear enough.
Now look at the FDR record for the manual and automatic trim input, and the actual trim position.

The actual trim position increases without any manual or automatic trim increase (in the upward direction) with the CUT OUT in operation. The only automatic and manual inputs are down, but the trim position moves up. Or am I reading everything backwards?
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Old 28th Nov 2018, 20:18
  #1760 (permalink)  
 
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Originally Posted by PickyPerkins View Post
Can someone please explain to me how to following can be possible:

The report says that during the flight previous to the accident flight, "The PIC moved the STAB TRIM switches to CUT OUT and the SIC continued the flight with manual trim without auto-pilot until the end of the flight." That’s clear enough.
Now look at the FDR record for the manual and automatic trim input, and the actual trim position.

The actual trim position increases without any manual or automatic trim increase (in the upward direction) with the CUT OUT in operation. The only automatic and manual inputs are down, but the trim position moves up. Or am I reading everything backwards?


The FDR doesn't record manual trim input if its you moving the trim wheel by hand. What it records are trim switch inputs.

What I think you are seeing is the stab moving in response to the wheel, not the "manual trim" switch.

It's down to the exact meaning of "manual" trim - a human manually commanding the trim motor through a switch, or a human manually applying physical effort himself to the trim wheel to move the stab.
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