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Indonesian aircraft missing off Jakarta

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Indonesian aircraft missing off Jakarta

Old 7th Dec 2018, 01:22
  #2041 (permalink)  
 
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Originally Posted by Roger_Murdock View Post
Sure enough. Is that statement based on interview with the crew?
My assumption is they were debriefed. The whole flight is described in detail in a little over one page - 18.1 PK-LQP Previous Flight.
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Old 7th Dec 2018, 01:23
  #2042 (permalink)  
 
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Originally Posted by arba View Post

Why didnít they get this ?
Suspect it was a delete option- not a standard display... If my memory of earlier discussion in this thread is correct ...
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Old 7th Dec 2018, 06:10
  #2043 (permalink)  
 
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When I first saw the column force charts on FDR data, one thing that impressed me was the force applied was very ragged toward the end of the flight.


Control Column Force Applied

Then there was this comment by birdspeed which prompted an examination of the breakout mechanism which separates the two control columns if one side becomes jammed.
What perhaps happens is a breakout of the control yokes just before the dive. FDR shows a difference in the applied control force on the yokes. I believe when elevator breakout occurs there is sudden loss of elevator effectiveness. This would cause a sudden bunt over, with a wtf moment and the pilots stopped any sustained opposite trim.
There was then an interesting NTSB Safety Recommendation A-11-7 through -11 dated February 2010 which discussed several control jam incidents and indicated that the 737NG (and MAX I assume) had some additional features not found on the earlier 737-300 through 737-500 aircraft. and were
improved by the addition of several mechanical override mechanisms
. One form of these mechanical override mechanisms is called a POGO. See this link for an explanation Pogo Load Limiter; Pogos are spring loaded linkages that act as a rigid link until a sufficiently high level of force is reached. Then the spring begins to allow motion and effectively disconnects mechanisms downstream of the POGO (which would normally have to be jammed for sufficient force to be generated.)

When you pull back on the control column inflight, you are not actually pulling back against the air loads on the elevator. That surface is being moved by an irreversible hydraulic cylinder. What you actually are working against is the elevator feel and centering unit. that applies force (torque) on the Elevator PCU input torque tube and which is actuating two elevator Power Control Unit hydraulic cylinders. One for the right elevator and the other for the left elevator. Both elevators are synchronized by the elevator torque tube. There is a pogo unit going to each elevator PCU control valve. Normally, the input valve force needed is rather light but should the PCU control valve jam, then its POGO will allow the rest of the input mechanism to move so that you can still actuate the opposite PCU control valve.

One thing I have not yet been able to establish is whether there are additional POGO-like devices installed between the individual control columns and the PCU input torque tube. If each column was connected directly to the PCU input torque tube, then activation of the breakout mechanism would seem to have minimal ability to free up a jam on one side of the control system forward of the elevator PCU input torquel tube since the control cables would back drive the opposite control column. I speculate that there are indeed POGO-like override mechanisms between the control columns and that they are set to a rather high force differential that would not be normally encountered. (More on this in a minute)

The elevator feel and centering unit applies its force profile on the PCU iinput torque tube by means of a linkage. As we can see from the force applied by the JT610 crew, they applied in excess of 100 lb force to the column during the final seconds. Suppose this level of force was sufficient to override the POGO unit on that side of the control pathway. leading to the elevator PCU input torque tube. If that happened, pulling further back on the control column would do nothing more! Remember, the trim had just reached full nose down. Could that be what the JT610 crew was trying to figure out by moving the controls, trying to find a spot that would "grab" and increase g? It would have felt like a control disconnect. Not the kind of thing that they would have had time to figure out once the nose began to drop.
For links to two more detailed posts on this subject in Tech Log see:Cockpit End Discussion and Elevator System Discussion

Last edited by Machinbird; 7th Dec 2018 at 15:13. Reason: Add links to Tech Log discussion
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Old 7th Dec 2018, 13:05
  #2044 (permalink)  
 
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Suastiastu: noting the comparatively stable vertical speed (in terms of error band) that you point to, is it your idea that something new happened (maybe something broke) in the last half of a minute? When I look at the match up of the reported radio conversation between the aircraft and ATC as they were arranging their return, the impression I was left with was that the aircraft was more or less controllable, and then all of a sudden it wasn't.

This discussion takes me to a related incident that did not include a failure in the air (ILS Glide Slope gone bad) that has to do with corporate culture and even industry culture.

The previous crew who hand flew this bird back (whether or not they diagnosed the problem right) may have had a slightly different mind set, informed by company and industry culture, than the subsequent crew. In discussing the choice to hand fly the approach once the GS and the assisted approach has gone south, or to go around and try another approach, the following question is asked (in hindsight) for the recent approach that went around after their approach went unstable due G/S signal being bad.
Jet Jockey A4 : If you know there is a possible problem with the G/S signal and no other type of approach is available, why not hand fly the aircraft?
Capn Bloggs : You just never know when the technology is going to try to kill you! Jet Jockey, you'll be put in the sinbin for suggesting that.




Granted, that interchange is light hearted, but I think it gets at an issue regarding mind set in any given crew who are confronted with "eh, it's not working right ..." Those mind sets, or operating assumptions, are informed by organizational culture.
I am sure that discussions will continue regarding "why not turn it off and hand fly?" in this case, after the fact, but I note that crew in the bad ILS being discussed in the other thread didn't do that. (For my money, that close to the ground if things get unstable Go Around is something we were all taught in the beginning: no approach is too perfect that it can't be waved off ...)

How comfortable were these two pilots Lion Air with hand flying?
How comfortable were they with shutting systems off and flying the bird by hand? (The previous crew may have had a different comfort zone than the crew on this fateful day).
How much sim time, or flight time, did they have doing that hand flying thing?

Or, did something else break as the crew were dealing with "all this" and the investigators have not yet hit upon that failure as they go through their difficult and demanding tasks? I am reminded of the difference in the understanding of the AF 447 crash before and after the boxes, and their information, came to light.

We humans tend to do what we are comfortable with, though training can help us broaden our comfort zone. When the CVR is found, a lot of what I am wondering about in this accident will get answered, I think.

Last edited by Lonewolf_50; 7th Dec 2018 at 13:23.
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Old 7th Dec 2018, 15:31
  #2045 (permalink)  
 
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Originally Posted by MickG0105 View Post
That statement neatly sidesteps the fact that on the B737, AOA data had never previously been used to directly inform 'the pitch trim system'.
Mmm, might want to check with respect to the NG. Maintenance manual (don't have FCOM but be interested to know what is in it on this) says:

Near stall, the speed trim function trims the stabilizer to a nose down condition to allow for trim above the stickshaker AOA and idle thrust. The trim continues until the stabilizer gets to its limits or the aft column cutout position is exceeded
Note: FCC / speed trim functional diagram labels this function "stall detection circuit".

MCAS is different in several ways (not least that various folk are saying earlier in the thread that MCAS is not about stall or stall detection). I doubt that this NG "stall detection" (and action) is still part of speed trim function in the MAX, I suspect that MCAS has replaced it (and probably evolved from it). One or more of the MCAS differences must account for the fact that Boeing and the FAA both appear to believe that JT610 cannot happen on an NG, and that may also be the key to understanding it, but I'm not convinced we even understand all the differences yet.
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Old 7th Dec 2018, 17:48
  #2046 (permalink)  
 
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Originally Posted by Turbine70 View Post
I think it's a fair distinction to raise but feel this presentation is disengenous.

As far as we can tell, MCAS is intended to provide a more consistent and predictable handling response in incipient stall conditions.

How does an intermittent and unadvertised control input, of complex algorithmic intensity, every 5 seconds, provide that?
'

Turbine70 - the "intermittent and unadvertised control input" that the JT610 crew experienced was a result of the AOA sensor failure combined with MCAS. I agree with your questioning how that could provide "consistent and predictable handling response in incipient stall conditions." It would not. With a properly functioning AOA sensor, MCAS will only take action when AOA is high, approaching stall and thus provide a tendency for the airplane to lower its nose and thus aiding with recovery from the high AOA condition.
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Old 7th Dec 2018, 20:16
  #2047 (permalink)  
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Lonewolf 50:
noting the comparatively stable vertical speed (in terms of error band) that you point to, is it your idea that something new happened (maybe something broke) in the last half of a minute? When I look at the match up of the reported radio conversation between the aircraft and ATC as they were arranging their return, the impression I was left with was that the aircraft was more or less controllable, and then all of a sudden it wasn't.
That is precisely what I've been getting at - not least of all because of the last minuet huge increase in fuel flow.

My comment earlier about a standard reaction to stabilizer runaway, intentionally disregarded the different symptoms the pilots would have been subjected to on the MAX. I'm trying to get into the pilot's minds and the comment was based on up to date training having been denied them and their mindset locked to an age-old operating procedure. Surely, even then, they would have gone for the cut-out switches, and if they did not, it was because something entirely different was also confusing the issue. By that I mean in addition to the five-second delays etc.

Indeed. Just imagine not knowing.

How does an intermittent and unadvertised control input, of complex algorithmic intensity, every 5 seconds, provide that?
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Old 7th Dec 2018, 20:41
  #2048 (permalink)  
 
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Originally Posted by FCeng84 View Post
'

Turbine70 - the "intermittent and unadvertised control input" that the JT610 crew experienced was a result of the AOA sensor failure combined with MCAS.
That is true, but from the descriptions I have read of the MCAS, my understanding is that this is exactly the way the MCAS would behave in an actual high AoA situation, intermittent adjustments of stabilizer position. In other words, the "intermittent" part wasn't a result of the bad AoA data, the erroneous AoA data was consistently and continuously high, and the MCAS was responding as it was designed to respond to a high AOA.
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Old 7th Dec 2018, 21:47
  #2049 (permalink)  
 
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Originally Posted by A Squared View Post
That is true, but from the descriptions I have read of the MCAS, my understanding is that this is exactly the way the MCAS would behave in an actual high AoA situation, intermittent adjustments of stabilizer position. In other words, the "intermittent" part wasn't a result of the bad AoA data, the erroneous AoA data was consistently and continuously high, and the MCAS was responding as it was designed to respond to a high AOA.
With correct AOA supplied to the MCAS function, it will begin automatic nose down stabilizer insertion when AOA first exceeds the MCAS activation AOA threshold. The amount of stabilizer motion that MCAS will command is a function of speed and the degree to which AOA exceeds the MCAS activation threshold. The flight deck effect is that the pilot will find that as AOA increases, the airplane has and ever increasing tendency to lower the nose to recover. Keep in mind that the stick shaker will also activate giving the pilot both auditory and tactile cues that AOA is above the normal range. Once AOA has dropped below the activation point, MCAS will remove the stabilizer increment that it has inserted. If a maneuver to higher AOA is started from a trim point at a lower, more normal AOA, MCAS will run the stabilizer nose down to aid in recovery and then once recovered to lower AOA will run the stabilizer back nose up so that it ends up close to where it started with the airplane back in trim at the condition from which it started the maneuver.
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Old 7th Dec 2018, 23:21
  #2050 (permalink)  
 
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Originally Posted by FCeng84 View Post
With correct AOA supplied to the MCAS function, it will begin automatic nose down stabilizer insertion when AOA first exceeds the MCAS activation AOA threshold. The amount of stabilizer motion that MCAS will command is a function of speed and the degree to which AOA exceeds the MCAS activation threshold. The flight deck effect is that the pilot will find that as AOA increases, the airplane has and ever increasing tendency to lower the nose to recover. Keep in mind that the stick shaker will also activate giving the pilot both auditory and tactile cues that AOA is above the normal range. Once AOA has dropped below the activation point, MCAS will remove the stabilizer increment that it has inserted. If a maneuver to higher AOA is started from a trim point at a lower, more normal AOA, MCAS will run the stabilizer nose down to aid in recovery and then once recovered to lower AOA will run the stabilizer back nose up so that it ends up close to where it started with the airplane back in trim at the condition from which it started the maneuver.
What would be the "steep turn" envelope of the MCAS? Would 250KIAS and 45 degree bank trigger it. Or min clean and some other angle of bank?
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Old 7th Dec 2018, 23:26
  #2051 (permalink)  
 
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Originally Posted by FCeng84 View Post
With correct AOA supplied to the MCAS function,
There is the problem right from the very first assumption, correct AoA data.

I don't think there is any disagreement about the need, intent and function of the MCAS. The issue appears to be this, on the surface its looks like a "quick and dirty" hack to compensate for an issue that cropped up in certification and testing, with the engineering failure mode analysis appearing to be deeply flawed. It was eminently foreseeable that one or both AoA sensors could provide erroneous or missing data due to mechanical or maintenance failure or physically by a birdstrike.

If you look at the Airbus (BTW, not a Bus fanboy, they had their own issues), there is clear guidance to to what happens to the flight controls with failure(s). A good example is the QRH flight control architecture reconfiguration diagram in the QRH, it tells you how the flight control system has reconfigured itself. On the other hand, the MCAS functionality looks to have been buried, with almost no references anywhere, it is almost as if Boeing had gone out of their way to deliberately obscure knowledge of this subsystem. Why? Because we don't want to overwhelm the pilots with information? Really?

Is it mentioned in the engineering manuals anywhere? If the maintenance staff had known about the interconnection between the AoA running the stab forward on it's own, would they have signed it off for a line flight? Was there a warning in the maintenance manual about the consequences of incorrect maintenance of the AoA probe? So many questions about this buried functionality that clearly has deep implications for the safe operations.


Source: Online copy of an old A32x family showing flight control reconfiguration with failure cases. A32x flight controls overview
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Old 8th Dec 2018, 00:08
  #2052 (permalink)  
 
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Originally Posted by CurtainTwitcher View Post
There is the problem right from the very first assumption, correct AoA data.

I don't think there is any disagreement about the need, intent and function of the MCAS. The issue appears to be this, on the surface its looks like a "quick and dirty" hack to compensate for an issue that cropped up in certification and testing, with the engineering failure mode analysis appearing to be deeply flawed. It was eminently foreseeable that one or both AoA sensors could provide erroneous or missing data due to mechanical or maintenance failure or physically by a birdstrike.

If you look at the Airbus (BTW, not a Bus fanboy, they had their own issues), there is clear guidance to to what happens to the flight controls with failure(s). A good example is the QRH flight control architecture reconfiguration diagram in the QRH, it tells you how the flight control system has reconfigured itself. On the other hand, the MCAS functionality looks to have been buried, with almost no references anywhere, it is almost as if Boeing had gone out of their way to deliberately obscure knowledge of this subsystem. Why? Because we don't want to overwhelm the pilots with information? Really?

Is it mentioned in the engineering manuals anywhere? If the maintenance staff had known about the interconnection between the AoA running the stab forward on it's own, would they have signed it off for a line flight? Was there a warning in the maintenance manual about the consequences of incorrect maintenance of the AoA probe? So many questions about this buried functionality that clearly has deep implications for the safe operations.


Source: Online copy of an old A32x family showing flight control reconfiguration with failure cases. A32x flight controls overview
Iberia had a hull loss in Bilbao because below a certain height (not disclosed in the AOM) there was less pitch authority, and they smacked the nose while trying to go around. I think Airbus changed the control inputs afterwards. Just because we have a pretty diagram I don't really trust the bus any better.
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Old 8th Dec 2018, 01:28
  #2053 (permalink)  
 
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We are in fierce agreement hans.
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Old 8th Dec 2018, 01:39
  #2054 (permalink)  
 
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Salute!

Be careful, CT, about assuming failure models are straightforward to develop when dealing with software that does more than put nice graphics on your screen or play music. The physical world has its own rules and failure modes. So when a software doofer that can control your physical machine, the failure modes get complicated. Feedback paths can be real tricky, and we are seeing a classic example with this example.

Additionally, the regression diagram for the early AB FBW model presented does not show the various flight control laws that are inhibited or modified or flat out fail. jez saying,

Gums sends..
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Old 8th Dec 2018, 14:07
  #2055 (permalink)  
 
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Pages and pages of discussion have still not satisfactorily explained the problem. It is more and more starting to look like a questionnaire on an application form for the ETPS (with a caveat – do NOT try this until you have done the course).

Maintenance manuals, hidden functionality, include a diagrammatical description of flight control metamorphoses, oh, and remember, if you try to trim manually, the whole process might start again with moved goal posts – and all this whilst struggling with an aircraft which has taken on a mind of its own.

I have been there and done that. The last thing I wanted at the time was to try to read all about it in a book. The why’s and the wherefores are up to the Accident Investigators. A line crew should never have been exposed to this.

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Old 8th Dec 2018, 14:33
  #2056 (permalink)  
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A very, very small pin's head and and angels being crushed to death in the guessing games.

Back when there is more actual data and facts whether from a preliminary report, proper software details from Boeing, or hopefully, CVR data.

Rob
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Old 19th Dec 2018, 12:24
  #2057 (permalink)  
 
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Lion Air 610 update

In the search for the CVR Lion Air has hired a professional private company from the Netherlands using the vessel MPV Everest to map/investigate the LKP area. The ship will probably arrive in the area on December 19th.

According to a Lion Air press statement in Bahasa translated with Google.

Last edited by A0283; 19th Dec 2018 at 15:35. Reason: Mentioning the source.
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Old 19th Dec 2018, 13:39
  #2058 (permalink)  
 
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Originally Posted by A0283 View Post
In the search for the CVR Lion Air has hired a professional private company from the Netherlands using the vessel MPV Everest to map/investigate the LKP area. The ship will probably arrive in the area on December 19th.
A professional private company? As the Zen Master said, "We'll see."

Lion Air (and the notion that the airline, rather than the investigative authority, has engaged a search and recovery service is extraordinary in its own right!) has contracted with Maritime Construction Services (MCS), a company that has only been around for only 3 years. MCS has a three page company website and currently operates just one vessel, the MPV Everest. They've had the Everest for less than 12 months. MCS bill themselves as 'an independent Dutch entity and exclusive partner of MRTS Group'. MRTS (Mezhregiontruboprovodstroy) is a Russian subsea construction company specialising in oil and gas pipelines.

Near as I can tell neither MCS or MRTS have ever conducted a subsea search or recovery operation anywhere at any time for anything! The MPV Everest is fitted with a pair of Triton XLX ROVs and a Forum Comanche ROV. None of those ROVs are particularly useful for survey or search work unless they intend to conduct the whole search effort visually; in the context of finding the CVR they're really only useful for conducting visual inspections of previously identified points of interest and some light recovery work. The Everest's apparent only qualification for this sort of operation was that it was handy; it was in Singapore last week. It also has a heavy lift capability not that that is likely to be called upon given the apparent break up of the aircraft on impact.

For the Lion Air 610 contract MCS has announced that they will form a consortium with two local Indonesian companies, Alliance Energy Solutions and PT NADI MARIN SUBSEA. Of that pair, AES is the only one with any sort of subsea sonar search capability via a Kongsberg Hugin AUV.

The whole thing looks like a bugger's muddle to me.
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Old 21st Dec 2018, 08:35
  #2059 (permalink)  
 
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The effort to search for and recover Lion Air PK-LQP's CVR is well underway...


Search for cockpit voice recorder of crashed Lion Air resumes in Indonesia
...A ship equipped with sophisticated technology resumed search for the cockpit voice recorder and the remains of victims of a fatal flight of Lion air JT 610, investigator said here on Thursday...

...A MPV Everest ship operated by a Dutch firm, which is hired by Lion Air, kicked off the search on Thursday morning, said Haryo Satmiko, deputy chairman of the committee.

"The MPV Everest arrived at the crash site on Wednesday night and resumed search this morning," he said.

The mission is undertaken around the clock and will last for ten days. If the mission fails in finding the cockpit voice recorder, a further evaluation will be carried out, Satmiko added.

The fuselage of the aircraft and the remains of 64 victims who have not been recovered would also be the targets of the mission, he said...

Excerpt from from Xinhua news.
===========================================

It's a bit strange - a rather quiet happening- that even local news outlets don't seem to pay any attention to this important undertaking.
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Old 21st Dec 2018, 10:44
  #2060 (permalink)  
 
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During the initial dives that found the fdr memory, the lead diver indicated that the seafloor was covered by a layer of mud of at least 80centimeters. Later 1 meter was mentioned. So they need to have both a clear mapping and a ground/mud penetration capability for that. Does anyone here know what kind of side scan/ multi beam system has that capability, or if there are underwater ground penetration radar systems for such soft toplayers?

If they are not successful this way they might end up having to remove the toplayer. There is some technology development in that field, but... Normal dredging methodologies seem a bit 'rough' for this purpose.
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