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Indonesian aircraft missing off Jakarta

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Indonesian aircraft missing off Jakarta

Old 29th Oct 2018, 13:14
  #101 (permalink)  
 
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Originally Posted by TURIN View Post
Also, is anyone else a little disturbed that a photo of the log book is available to read on the internet. Unless the log book has been discovered, dry and undamaged from the wreckage site that has to have been taken before the flight. Why? Who has released it? If that was my name on the log book I think I would be barricading the doors now. Relatives with pitchforks anyone?
Aircraft mechanic here. And yes i am a Little bit disturbed that a leak like this happened. Shouldn’t be because there are names of flight crew and mechanics. Apart from that there are more than one copy of the report. As you can read on the bottom of said report. The pink we got is meant to stay with the technical Departement. So it’s just fine this way.
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Old 29th Oct 2018, 13:14
  #102 (permalink)  
 
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Originally Posted by Icarus2001 View Post
Again, how do you know they were "doing" 300 knots. Airspeed versus groundspeed...
Are you seriously unable to reason your way through this? OK, I'll lead you though it a step at a time. Yes, airspeed is not the same as groundspeed. Everyone understands that. However, they are not unrelated. At 5000 ft, and standard temps, a 300 knot groundspeed would equate to a still air IAS of 275 knots in round numbers. Even if we hypothesize a 30 knot tailwind, that's still an IAS of 245 knots. Stalling a 737 at 245 knots IAS, while not impossible, is unlikely.

Last edited by A Squared; 29th Oct 2018 at 13:54.
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Old 29th Oct 2018, 13:15
  #103 (permalink)  
 
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You can't stall a 737 at 300kts
You can stall a 737 at 300kts groundspeed, as this value ignores desity (temperature, altitude) and wind speed.
300kts groundspeed can easily be 100kts EAS any day, which allows a 737 to be stalled.

The second item of the log mentions a FEEL DIFF PRESS ? What is this? Artificial feel? Or am I misreading it?
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Old 29th Oct 2018, 13:28
  #104 (permalink)  
 
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I'm absolutely astonsihed to see copies of the flight/maintenance log published here, this is company-confidential stuff at the best of times but when related to an accident it seems utterly beyond belief. Although it is illuminating to us it must be causing the company and particularly the engineer/s involved considerable anguish to have thos sort of info and identification published.

I hate to think what will happen to who dunnit if/when caught. Doubtless he had a motive and it may well be a valid one if his beef is about maintenance or operational standards but it's a pretty extreme action to take.

Having gone this far he might do well to voice his beef here and at least remove any speculation about his motives or his take on the significance of these documents.
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Old 29th Oct 2018, 13:35
  #105 (permalink)  
 
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Originally Posted by Volume View Post
300kts groundspeed can easily be 100kts EAS any day, which allows a 737 to be stalled.
At 5000 feet?
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Old 29th Oct 2018, 13:42
  #106 (permalink)  
 
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Originally Posted by Volume View Post
You can stall a 737 at 300kts groundspeed, as this value ignores desity (temperature, altitude) and wind speed.
300kts groundspeed can easily be 100kts EAS any day, which allows a 737 to be stalled.
Yeah, we're not discussing an airplane whcih was flying in conditions where a 300 knot groundspeed and an EAS of 100 knots are simultaneously possible. We're discussing the Indonesian 737 which crashed a day ago. That airplane was no higher than about 5000 ft MSL Neglecting winds, a 300 knot groundspeed equates to about 275 knot IAS at that altitude. Winds in excess of 20-30 knots at 5000 ft are unlikely unless there was some fairly unusual weather going on. I haven't heard any mention of extraordinarily strong winds in this accident, have you? No? So if we assume a tailwind at the upper end of that range, we're still probably looking at an IAS greater than 245 knots, if an airplane at 5000 ft is showing a groundspeed of 300 knots.

In order to get a 300 knot groundspeed with an EAS of 100 knots you'd have to be somewhere around 40,000 ft with a 100 knot tailwind. Were you under the impression that this airplane in this accident that we're discussing here, today, in this thread, was at 40,000 ft, with a 100 knot tailwind? No? If not, what on earth is your point in even mentioning that? What relevance do you imagine that brings to this discussion?

Last edited by A Squared; 29th Oct 2018 at 19:43.
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Old 29th Oct 2018, 13:48
  #107 (permalink)  
 
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Originally Posted by TURIN View Post
If the defect was on the last flight, even the night before, surely the crew should be aware of all maintenance log entries before accepting the aircraft. Is it not SOP to review the log back to the previous flight? My own experience tells me this is so.

Also, is anyone else a little disturbed that a photo of the log book is available to read on the internet. Unless the log book has been discovered, dry and undamaged from the wreckage site that has to have been taken before the flight. Why? Who has released it? If that was my name on the log book I think I would be barricading the doors now. Relatives with pitchforks anyone?
Anyone who has been involved in accident investigation is quite disturbed about it.
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Old 29th Oct 2018, 14:02
  #108 (permalink)  
 
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Originally Posted by Volume View Post
You can stall a 737 at 300kts groundspeed, as this value ignores desity (temperature, altitude) and wind speed.
300kts groundspeed can easily be 100kts EAS any day, which allows a 737 to be stalled.
Not at 5000 ft it can't.
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Old 29th Oct 2018, 14:06
  #109 (permalink)  
 
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Well its all speculation but thats what we're here for so..lets start with what we know:
A/C had known UAS event day before but it was controlled by crew and they landed safely.It is written up and signed
off as cleared.
A/C takes off again next day and suffers another UAS event,this time proving unrecoverable.
Conclusion: diagnosis and/or rectification work by maintenance failed to clear problem or worse still exacerbated problem.
What else do we know?
Flightradar uses ADS-B and we have the readout showing unusually high speed after takeoff well
below 10000 feet(normal altitude for speed restriction).Its GPS derived and we can trust it.
We also know(using logic) that this is not what the flightcrew saw.They saw something entirely different.
What did they see?What would cause them to overspeed,climb erratically and eventually lose control?
They must have seen the direct opposite....low airspeed,stall warning,spurious windshear warning,stuck altimeters maybe etc
Now the flightcrew are aware of the previous UAS event and they have presumably briefed each other on what to do
following UAS after takeoff.They will presumably be alert to the possibility of UAS and have reviewed the QRH and
reiterated the importance of the 80knot call and the need to cross-check all 3 airspeeds.So which scenario would let them
get airborne with no indication of a pitot static fault on the takeoff roll?
Its not pitot but static...static vent blocked.Airspeed will indicate normally on takeoff but underread in climb.Altimeters will
remain stuck after takeoff.Its a nasty little scenario and could easily lead to confusion.The subsequent loss of control could be explained by the high speeds with flaps still down(crew distraction and onset of panic).
If it happens(altimeters dont show climb after liftoff,you get windshear warning(false) and.or stick shaker(false) you have to
climb to 1500' on RADIO ALTIMETER, level off, set 60% N1,ignore the warnings and LAND immediately,either visually or on vectors.
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Old 29th Oct 2018, 14:10
  #110 (permalink)  
 
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Who said anyone was pulling? There are plenty of examples...
How else do you increase AofA?
What if... a failure led to that degree of back pressure?

I am not for one minute suggesting that in this case just pointing out to the "it did not stall" brigade that, yes it could have and also that FR data is fraught with errors. i have watched it plot an aircraft landing as I saw the aircraft turn during a missed approach, it has predictive algorithms so the speed and direction you see is not always what the aircraft is doing.

I am happy to wait for the FDR/CVR. If that data leaks as quickly as the tech log, I will not have to wait long.
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Old 29th Oct 2018, 14:32
  #111 (permalink)  
 
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I note that in the tech log the answer to the question 'return to service?' had a tick in the 'no' box in all three sections. Does this mean that further action/investigation was required before signing off the aircraft as serviceable?
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Old 29th Oct 2018, 14:41
  #112 (permalink)  
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There was earlier talk of pitot covers not being removed. Then a suggestion that they would not have been fitted overnight. Then that the system may have been maintained over night.

But there are other possible problems are there not? Could there be water in the system? Has there been significant rainfall around these two flights?
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Old 29th Oct 2018, 14:43
  #113 (permalink)  
 
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Static air intakes covered. That would explain the correct airspeed reading during take off roll.
As soon as you are airborn, all parameters will be wrong.
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Old 29th Oct 2018, 14:48
  #114 (permalink)  
 
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Originally Posted by sdelarminat View Post
Static air intakes covered. That would explain the correct airspeed reading during take off roll.
As soon as you are airborn, all parameters will be wrong.
That’s also my educated guess from everything I’ve read and seen so far. Hopefully not another human factor by a mechanic who forgot to take off some high speed tape or some test equipment is still fitted on the static port. But i will place my bets in this direction.
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Old 29th Oct 2018, 15:03
  #115 (permalink)  
 
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Flightradar uses ADS-B and we have the readout showing unusually high speed after takeoff well
below 10000 feet(normal altitude for speed restriction).Its GPS derived and we can trust it.
I would not say that "we can trust it", but with a grain of salt (and using the wind from the METAR) it allows a rough estimation of the speed range the aircraft was in, and allows to exclude certain scenario.

And I agree that speed was higher than what you would normally expect, however taking into account the unreliable airspeed, it is still within the safe range, and if in doubt a bit more is better than not enough speed, so it would be understandible if the pilot selects pitch and power figures at the higher end of the speed range, and would round up a few memory numbers...

A/C had known UAS event day before but it was controlled by crew and they landed safely.It is written up and signed
off as cleared.
A/C takes off again next day and suffers another UAS event,this time proving unrecoverable.
Conclusion: diagnosis and/or rectification work by maintenance failed to clear problem or worse still exacerbated problem.
It is not uncommon, that the first step of troubleshooting is unsuccessful.
You find a lot of "if the problem persists" wording in troubleshooting manuals, this is why it is not calles troublesolving manual...
There should always be enough redundancy and safety margin to encounter any problem a second time.

Flying the 737 Classic series solely on standby flight instruments is a most demanding exercise in instrument flying - especially in IMC.
This accident happened in VMC in daylight conditions. Returning to an airport under those conditions should not be too demanding for any licensed pilot on a modern certified aircraft.

Is the 737 known for issues with water in the pneumatic instrument lines? Did the aircraft experience severe rain recently? Does the 737 Max pitot/static system differ significantly from the NG ("Smart probes" instead of pipes...)?
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Old 29th Oct 2018, 15:18
  #116 (permalink)  
 
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Could be completely wrong but if the tech log image is real it would suggest it was a problem on just one side (probably the Captains side).
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Old 29th Oct 2018, 15:46
  #117 (permalink)  
 
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I’m not a supporter of the fake news crowd, but having just listened to a CNN guest state that “there must have been something wrong with the engines because the flight wasn’t as high as it would normally be”.... I’m in disbelief. If you’re reading this CNN, show us where your professionalism is. That was nothing short of a shocking sound bite from someone seeking air time.
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Old 29th Oct 2018, 15:52
  #118 (permalink)  
 
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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?

Are the sensors independent of any pneumatic connections to the cockpit, or do they measure at their location and transmit data via a mux bus or wires? Most of we old farts remember when we tapped on the gauges in front of us sometimes to determine if they were stuck!!

Contamination in the lines is a real problem especially in the tropics. USAF lost a very expensive B-2 at Guam because moisture in the lines caused bad air data and the plane "dug in"/pitched up just as gear came up. Great videos of that crash. Turned out a better procedure for clearing the lines resulted. I tink there was also an incident whereby an insect had decided to make a home in a pitot tube.

Too much talk about a stall at any speed and such. Good grief, I would hope most folks here know all about AoA, EAS/CAS/TAS versus ground speed at various altitudes, etc. I know there are aviation afficianoados here that have little or no experience in the "wild blue" or have never flown any "high performance" planes, but sheesh. Rant off.....

And BTW, I have had my aileron-rudder-interconnect wired backwards one day, and have had pitot-static system failure.

Gums sends...
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Old 29th Oct 2018, 16:08
  #119 (permalink)  
 
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Originally Posted by Icarus2001 View Post
. i have watched it plot an aircraft landing as I saw the aircraft turn during a missed approach, it has predictive algorithms so the speed and direction you see is not always what the aircraft is doing.
And an hour later, did it *still* show the airplane having landed, or had it replaced the data predicted in error with the correct data as received? I would expect the latter. But more to the point, I could see perhaps an writing an algorithm which predicts an airplane to have landed, when it notes that it is on a straight descending path pointed right at a runway, and if the airplane goes missed instead, it might take a few received data points and some data processing by the software to discover that the landing prediction was in error, and correct that. It seems a lot less likely that someone would write a predictive algorithm which would "predict" an airplane maintaining 5000 ft MSL and 300 knots, plus or minus random excursions either side of both parameters, for 6-ish minutes, when in fact the airplane did something completely different.
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Old 29th Oct 2018, 16:11
  #120 (permalink)  
 
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Originally Posted by Pontius Navigator View Post
There was earlier talk of pitot covers not being removed. Then a suggestion that they would not have been fitted overnight. Then that the system may have been maintained over night.

But there are other possible problems are there not? Could there be water in the system? Has there been significant rainfall around these two flights?
Unless they were still on from the flight that reported the initial problem, and remarkably and however improbable this might be, no-one noticed prior to the second flight.
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