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-   -   Indonesian aircraft missing off Jakarta (https://www.pprune.org/rumours-news/614857-indonesian-aircraft-missing-off-jakarta.html)

LaissezPasser 29th Oct 2018 20:01


Originally Posted by ZAZ (Post 10296047)
Its a conglomeration of everything as noted in the tables whether official or members receiver number.


In this case, flightaware's ADS-B data came from Tangerang/Budiarto Airport, Pondok Cabe Airport, Halim Perdanakusuma International Airport, and Soekarno-Hatta International Airport.

clark y 29th Oct 2018 20:06

Thanks for the answers with regard to the data.
Time to follow 7478ti's advice and wait for more info.

cjad100 29th Oct 2018 20:13


Originally Posted by gums (Post 10295770)
Salute!

Great point Volume.

Besides the stab trim issue, which bothers me a lot, the air data "tubing" or lines are of interest. A combination of erroneous air data with trim operating backwards would be "interesting" to fly, huh?

Gums sends...

I agree. The altitude data and speed data seems to me to show an aircraft that was over-correcting in pitch over the sort of timescales I'd expect if a pilot was establishing S&L, then getting deviated away from it again by inappropriate trim inputs from the automatic systems on the aircraft, which needed manual correction, and so on.

With a good attitude indicator and stable trim and power settings, you should easily be able to maintain S&L flight to within a smooth 100 foot tolerance using manual flying. So, either:

a) The elevator trim was constantly and unpredictably changing
b) The power settings were constantly and unpredictably changing
c) Some other aircraft configuration was constantly and unpredictably changing (flap damage, other gradual airframe damage)
d) The pilots were so unused to hand flying that they struggled to maintain S&L flight at 5,000 feet on a clear day

Of those, and given the reference to stabiliser trim moving in the wrong direction, (a) seems likely and matches the kind of bad but "just about" control we see in the aircraft prior to LOC.

One thing that hasn't been mentioned by anyone is an explosive device which partially but not completely damaged the ability of the aircraft to be flown. Not all explosive devices will have sufficient power to destroy an aircraft mid-flight. However, I would have thought the pilots would have mentioned any loud bang or decompression to ATC.

flash8 29th Oct 2018 20:13


Originally Posted by Auxtank (Post 10295961)
It surely would have been.

The copy posted earlier and now gone (good move) was the pink/ purple copy which would have been for the office.

It looked very much like a photo from a cellphone which has then been disseminated as the image shown looked like it was a photo of that photo being displayed on another device if that makes sense, so traceability might be difficult/impossible. Before we viewed it it likely had been through many hands.

Switchbait 29th Oct 2018 20:22

STS - Speed Trim System.
There are times when the STS “appears” to run in reverse when it is functioning correctly, this can depend on what the pilot is trying to achieve and whether or not they are pushing or pulling...

The STS trims to try to return the aircraft the the “trimmed” speed.

Feel Diff Press light illuminating with an Airspeed Disagree and Alt Disagree sounds reasonable to me due to the elevator pitot input to the system.

as someone else mentioned, the airplane is in a depth that is easily reached so hopefully the DFDR is recovered soon and we will know more.....

RIP to those in the machine.

HolyMoley 29th Oct 2018 20:23


Originally Posted by A Squared (Post 10295815)
The probability of forgetting to remove the pitot covers on a day after there was a write up for Unreliable Airspeed is identical to the probability of forgetting to remove the pitot covers on a day after there was no write-up for UAS.

It most certainly is not. It is the chance of a UAS happening to an aircraft (much less than 1 ie a very small number) multiplied by the chance of an aircraft taking off with the pilot covers on (also a very small number, less than 1) multiplied by the chance of that happening to the same aircraft (another small number less than 1) multiplied by the chance of it happening in the same 24 hour period (one more very small number less than 1).

tdracer 29th Oct 2018 20:44


Originally Posted by groundbum (Post 10296055)
does the Boeing MAX generate ACARS maintenance messages back to base that will therefore be available pretty much immediately? As in the assorted Airbus incidents these give a pretty good idea of the timeline of system failures...

G

It would have that capability - however the operator has to sign up for it (ACARS costs money). No idea of Lion would have such a feature enabled.

DaveReidUK 29th Oct 2018 20:47


Originally Posted by HolyMoley (Post 10296099)
It most certainly is not. It is the chance of a UAS happening to an aircraft (much less than 1 ie a very small number) multiplied by the chance of an aircraft taking off with the pilot covers on (also a very small number, less than 1) multiplied by the chance of that happening to the same aircraft (another small number less than 1) multiplied by the chance of it happening in the same 24 hour period (one more very small number less than 1).

You are both correct, because you are describing different probabilities.

A Squared 29th Oct 2018 21:01


Originally Posted by HolyMoley (Post 10296099)


It most certainly is not. It is the chance of a UAS happening to an aircraft (much less than 1 ie a very small number) multiplied by the chance of an aircraft taking off with the pilot covers on (also a very small number, less than 1) multiplied by the chance of that happening to the same aircraft (another small number less than 1) multiplied by the chance of it happening in the same 24 hour period (one more very small number less than 1).

Umm, no, you're falling prey to a common fallacy; That previous, unrelated events somehow affect the probability of something happening. It is what leads people to erroneously conclude that the probability of a fair coin toss coming up heads is different if the previous coin toss came up heads. It's not. The probability of any single fair coin toss coming up heads is .5, it doesn't matter that the previous coin toss was heads, it doesn't matter that the previous 5 coin tosses were heads, when you toss that coin, the chances are still 50/50 heads/tails. Whether or not the flight crew removes the pitot cover on any given day is like a single coin toss. There's a certain probability that it will be forgotten, and that probability is not affected by an unrelated event whcih occurred the previous day. The probability of 2 consecutive coin tosses both coming up heads is 0.5 X 0.5 = 0.25, but that is not the same question as the probability that the next coin toss will be heads; regardless of what happened on the last coin toss, the next coin toss will have a .5 probability of heads.

ShenziRubani 29th Oct 2018 21:04


Originally Posted by ZAZ (Post 10296041)

Get real man, parents and relatives come to these pages.
You have no information except some radar traces.
stick to flying mate let atsb do their stuff.
MH speculation all over again!
opinions are like backsides!

It's still not a "news" website and it is still purely a pilot forum where pilots come discuss, comment, express their opinions; and this is what we do every time some of ours get involved in a fatal, or not, accident. We are Monday-morning-quaterbacks, we will comment right away, we want to know, we want to discuss. So Birdstrike737 was right, people shouldn't come here expecting answer to what happened to their loved ones, it's a pilot forum where pilots shoot the breeze and exchange ideas on aviation things. It is natural, sadly, that we comment, theorize, discuss on a crash that just happened. This is an "opinion" place, it's an Internet forum, and this board is Rumors & News. Everyone will let ATSB, NTSB, CAA and else do their job, but we will discuss it on here if we choose to. It's the Internet. Those who don't want to discuss, don't want to read it, don't have to.

RifRaf3 29th Oct 2018 21:06

Not all probabilistic events are independent. You need to read up on Bayesian probability which played a large part in determining the flight path of MH370.

LaissezPasser 29th Oct 2018 21:06


Originally Posted by flash8 (Post 10296079)
It looked very much like a photo from a cellphone which has then been disseminated as the image shown looked like it was a photo of that photo being displayed on another device if that makes sense, so traceability might be difficult/impossible. Before we viewed it it likely had been through many hands.

Jon Ostrower has an interesting analysis over at The Air Current which notes that there are at least three different versions of that Aircraft Flight & Maintenance Log circulating in social media:

The chilling concern of this is not only that documents are changing in different iterations on social media but that a signed maintenance document might’ve been modified in some fashion to include a corrective action after the fact.

Jwscud 29th Oct 2018 21:15

From my old B738 FCOM, the speed trim is inhibited if the control column is moved in the opposite direction to which the trim is running. I am assuming that the system in the max is similar?

The FZ accident at Rostov showed it was possible for a crew to get the aircraft horribly out of trim manually at low altitude and lose control.

RifRaf3 29th Oct 2018 21:22

Re tech logs:
On a single seat aircraft, you had the privilege of viewing the tech log BEFORE you did the walk-around and this allowed for discussion with the ground crew so that you could pay extra attention to pertinent items during that inspection. This saved my bacon more than once.

Transit to B747 and it was not until after the walk-around and battling through pax queues and climbing two floors that you got to see the tech log. If the pitot/static system had been worked on you were unlikely to go back down and have a second look.

Perhaps with modern technology, the person signing off the tech log could simply transmit an image back to flight ops for the crew to peruse before doing the walk-around.

HolyMoley 29th Oct 2018 21:28


Originally Posted by A Squared (Post 10296138)
Umm, no, you're falling prey to a common fallacy; That previous, unrelated events somehow affect the probability of something happening. It is what leads people to erroneously conclude that the probability of a fair coin toss coming up heads is different if the previous coin toss came up heads. It's not. The probability of any single fair coin toss coming up heads is .5, it doesn't matter that the previous coin toss was heads, it doesn't matter that the previous 5 coin tosses were heads, when you toss that coin, the chances are still 50/50 heads/tails. Whether or not the flight crew removes the pitot cover on any given day is like a single coin toss. There's a certain probability that it will be forgotten, and that probability is not affected by an unrelated event whcih occurred the previous day. The probability of 2 consecutive coin tosses both coming up heads is 0.5 X 0.5 = 0.25, but that is not the same question as the probability that the next coin toss will be heads; regardless of what happened on the last coin toss, the next coin toss will have a .5 probability of heads.

I see your point, and I don’t want to get embroiled in a statistical discussion, but what you are saying is that the chance of flipping two different coins one after another and having them both come up heads is the same as flipping one on it’s own coming up heads. Am I right?

No Idea Either 29th Oct 2018 21:31

i’ll rephrase my response for clarification. You can experience ‘high speed buffet’ in any high speed capable aircraft at a high IAS. It’s called......wait for it......high speed buffet (compressibility effects) and you can experience ‘low speed buffet’ in any aircraft. That one is low speed buffet (classic critical angle exceedance). In my work they are referred to as just that, low and high speed buffet. They are both a stall, brought on by different aerodynamics but both produce loss of lift across the wing. I should have specified the difference earlier. I was just unsure as people were barking on about not be8ng able to have a LOC due to a ‘stall’ at a relative high speed. It only takes a few degrees of attitude applied too abruptly and bang your in it. I never mentioned EAS v IAS at any altitude. Rant over.

das Uber Soldat 29th Oct 2018 21:31

This doesn't feel like vanilla unreliable speed to me. It may have been a contributing factor, but you don't lose control of a 737 doing over 300 knots in day vmc. You fly it level. Maybe you end up too slow and stall, but that clearly isn't what happened here. From the data it looks like a very high speed, extreme nose down attitude.

Either something mechanical has failed, or after a contributing factor, such as unreliable speed that has been mishandled, structural damage has occurred that has culminated in the final catastrophic dive.

JanetFlight 29th Oct 2018 21:34

The similarities between this sad accident and those at "recent" Saratov An148 are pretty scary and terrifying, IMHO.
Just after take off, "almost new type on the fleet", unreliable speed and altitude infos, unusual flight/climb profile...
The main difference remains the WX, Russia = Cold&Iced, Indonesia=Good Asian Weather:
However very interesting to follow up,,,my deepest condolences to all who lost their loved ones.

Piper_Driver 29th Oct 2018 21:53


Originally Posted by RVman (Post 10295957)
The tech log seems factual, not sure why it is such a bother that it is available online. At least it guards against fake news.
So far as I can understand from the photo the resolutions read as:
REF IFIM 34-20-00-810-801 REV 15/07/2018 PERFORMED FLUSHING LH PITOT ADM AND STATIC ADM (AIR DATA MODULE) OPS TEST ON GROUND FOUND SATISFIED
REF IFIM 28-34-00-810-803 REV 15/07/2018 PERFORMED CLEANED ELECTRIC. C???. PLUG OF ELEVATOR FEEL COMPUT?R C/O TEST ON GROUND FOUND OK

Question to tech guys - any chance monkeying around with a connector on the Elevator Feel Computer could have caused issues with elevator control? An intermittent maybe that worked OK when first plugged in. I don't work on aircraft, but have seen my share of issues with electrical faults in 40+ years of electrical engineering (20 on cars).

Vessbot 29th Oct 2018 22:07

As I was coming home and getting ready to check the thread again, I was just thinking it needed more blowhard "it can stall at any airspeed" posts, and when I refreshed it I was not disappointed.

In more serious matters, I saw Wiedhopf's plot of the granular FR24 speed and altitude data, and it gave me the idea to grab the spreadsheet myself and calculate the Total Energy and add it to the plot, to see if it might reveal anything. I converted the columns to meters per second (speed) and meters (altitude) for consistency of units and made a new cell that contains .5*speed^2+9.807*altitude, which is kinetic plus potential energy without the mass, which is approximately constant. (The result is divided by 5 anyway, to make the graph height roughly match the others. So it's an arbitrary unit, but we get to see the changes and trends.) There's also vertical speed from FR24, which I assume it auto generated from altitude over time. The black and blue colors for altitude and speed are preserved from Wiedhopf's graph, the VS is in green, and the TE in orange.

https://cimg4.ibsrv.net/gimg/pprune....f769683b9f.png

So what do we see in the TE? During the main steady-state climb, the TE is evenly increasing with a constant slope, just as we'd expect. And where there's the first big altitude dip and speed rise, there's barely a change in the TE slope, which is what we would expect for an even airspeed-altitude tradeoff (i.e., no significant thrust or drag changes, be it from a drag device or significant maneuvering.) A closer look does actually show a slight decrease, which matches a speed (i.e., drag) rise significantly above best L/D. So far so good, the plot is "sane."

Anyway, the small amount of downward kink in that slope, I think, allows us to calibrate our eye for further kinks later on. Once the main climb is done and they level off, all the altitude and VS meanders are smaller than during the original -2500 fpm dip, but the TE meanders are bigger. That shows to me, drag or thrust changes. I think we can rule out drag changes from drag devices as it would be unlikely any would be deployed for any reason, and we can also rule out drag changes from maneuvering, as the track plot shows more or less straight ahead, and the vertical meanders are all smaller than the first -2500 fpm one. By process of elimination, that leaves thrust changes, which is consistent with the present speculation of the crew trying to fly the airplane with degraded instrumentation or control difficulty.


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