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Indonesian aircraft missing off Jakarta

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Indonesian aircraft missing off Jakarta

Old 4th Nov 2018, 00:34
  #521 (permalink)  
 
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https://theaircurrent.com/aviation-s...-social-media/
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Old 4th Nov 2018, 01:04
  #522 (permalink)  
 
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Extract from the Aeroperu Boeing 757 CVR 1996 crash with static vents blocked (English translation)
https://web.archive.org/web/20030427.../183038-1.html
One wonders if the Lion Air crew found themselves in the same state of confusion. Sensory overload can overwhelm rational actions every time.
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Old 4th Nov 2018, 01:07
  #523 (permalink)  
 
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Originally Posted by D Bru View Post
As concerns the cause, it would seem to me relatively rare for several pitot systems to fail simultaneously. To note that the ias/alt pitot system is separate from the elevator pitot system, the first being located at the front of the A/C, the second on each side of the front base of the V/S. (Repeated) Simultaneous failure of both systems would IMO indicate something more structural then the pitots themselves.

As to the effect, in particular the "FEEL DIFF PRESS LT ILL" could be of particular relevance. The elevator feel computer provides simulated aerodynamic forces using airspeed (from the said elevator pitot system) and stabilizer position. Feel is transmitted to the control columns by the elevator feel and centering unit. To operate the feel system the elevator feel computer uses either hydraulic system A or B pressure, whichever is higher. When either hydraulic system or elevator feel pitot system fails, excessive differential hydraulic pressure is sensed in the elevator feel computer and the FEEL DIFF PRESS light illuminates.

I stand to be corrected, but if (barring hydraulic problems) the elevator feel and centering unit enters into a condition that triggers the FEEL DIFF PRESS annunciation (for whatever reason, either pitots or a more systemic failure, since in this case also the "main" pitot system could have been affected simultaneously), it would mean that particularly in manual flight the elevator inputs through the control columns could have a much different (greater) effect than normal. It would be interesting to know whether such inputs with a "dysfunctional" feel and centering unit could lead to upsets with an ultimate loss of control, which at relatively low altitude would be difficult to recover from in time.
Thanks Bru, am also operating on the assumption that the maintenance logs are genuine and the faults on the previous flight point are likely factors on the accident flight.

The FEEL DIFF PRESS light from the elevator feel system is very puzzling because (as you said) the pitot system is separate, and to my knowledge totally isolated from the ports/ADMs/ADIRUs at the front of the aircraft. I am assuming an actual large hydraulic pressure difference between systems A and B would lead to more fault indications than just the FEEL DIFF PRESS. One thing I can't find out is the static source for the elevator feel pitots, but this system should be in an unpressurised part of the plane and hence could just sample it's ambient surrounds to pair with it's pitot. So how could these problems be related?

On thing to consider is whether the STS (if operating on bad airspeed data) could effectively contaminate the feel system operation via the changes it makes to the stab trim. Stab trim position is an input to the elevator feel system along with airspeed from it's dedicated pitot system (which should have been working even with issues with the nose airspeed sensing systems). In this case the operation of the STS with bad airspeed is the major issue, with likely alteration of elevator feel a secondary (but likely very unhelpful) issue.
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Old 4th Nov 2018, 01:10
  #524 (permalink)  
 
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Do the stats show that the Children of Magenta are crashing planes due to lack of manual flying skills? Are planes crashing on stormy 30 knots cross wind approaches? I would argue that that the pilots who flew AF447, Emirates 521, AA 8501, etc. could fly manual just fine. The problem was that they had no idea what the automation was doing when problems crop up. It's the sheer complexity of modern aircraft. Excellent in increasing air safety to unprecedented levels but has become incredibly complex for both "old school" and "magenta" drivers.
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Old 4th Nov 2018, 01:56
  #525 (permalink)  
 
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AF447, Emirates 521, AA 8501, etc. could fly manual just fine. The problem was that they had no idea what the automation was doing when problems crop up.
Well let's look at the Emirates B777 go round from touch down. Do you need a two day course to tell you to push the thrust levers forward if they do not move forward on their own? Or to check the engine gauges to confirm that the engines are spooling up after pressing TOGA? That is fundamental "pilot stuff" surely?

Isn't the point that if " they had no idea what the automation was doing" then they should hand fly? As you say "they could fly manual just fine".

I agree it is not too difficult to occasionally "get lost" in the automation modes, that is why there are disconnect buttons.
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Old 4th Nov 2018, 01:57
  #526 (permalink)  
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If a pitot cover had been left on it should have been very obvious to the crew before they even got to 80kts on the take-off roll, surely?
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Old 4th Nov 2018, 01:59
  #527 (permalink)  
 
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"I would argue that that the pilots who flew AF447, Emirates 521, AA 8501, etc. could fly manual just fine."

The fact that these perfectly flyable aircraft crashed voids your statement.
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Old 4th Nov 2018, 02:25
  #528 (permalink)  
 
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Thanks for setting me straight you guys. No, I don't deal with airliners, but I learned a lot following the entire, sorry AF447 thread! Sorry for my ignorant remarks, I meant well.
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Old 4th Nov 2018, 02:29
  #529 (permalink)  
 
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Originally Posted by FL11967
I would argue that that the pilots who flew AF447, Emirates 521, AA 8501, etc. could fly manual just fine.
?? Do you know what "flying" actually is or what it entails? It means looking at the flight and engine instruments, checking that the aeroplane is doing what you want, and if it is not, intervening with your hands, and feet to make it so. "Flying" also means being able to do it when startled or caught unawares. That did not happen in any of those prangs. That fact that you cannot see that, even with NO systems knowledge, each of those accidents would have not occurred had the PF just employed basic flying techniques indicates to me you do not understand the job.

Originally Posted by 1624
The fact that these perfectly flyable aircraft crashed voids your statement.
No it doesn't. If pilots "could fly manual just fine" they wouldn't have crashed. That's the whole point. It is clear that some of you have no idea of the modern cockpit operates.

Originally Posted by Golden Rivit
As for that, anybody who has half an idea (which is obviously not "Theaircurrent") would realise that all those docs, as shown, are legit but at various stages of the defect reporting and the rectification process. In other words, that whole article is a meaningless waste of time and effort. Please stop posting this stuff.
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Old 4th Nov 2018, 03:14
  #530 (permalink)  
 
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Originally Posted by 1624The fact that these perfectly flyable aircraft crashed voids your statement.
No it doesn't. If pilots "could fly manual just fine" they wouldn't have crashed. That's the whole point. It is clear that some of you have no idea of the modern cockpit operates.


That was my point.
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Old 4th Nov 2018, 03:20
  #531 (permalink)  
 
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Originally Posted by parabellum View Post
If a pitot cover had been left on it should have been very obvious to the crew before they even got to 80kts on the take-off roll, surely?
https://www.ntsb.gov/_layouts/ntsb.a...03IA005&akey=1
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Old 4th Nov 2018, 03:26
  #532 (permalink)  
 
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If a pitot cover had been left on it should have been very obvious to the crew before they even got to 80kts on the take-off roll, surely?
Just like the Malaysia A330 on 18 July 2018 at Brisbane that became airborne with the covers on.

Which of course begs the questions...100 knots check? V1 Rotate? The crew acknowledged they had red SPEED flags on their PFD.

https://www.atsb.gov.au/publications...r/ao-2018-053/
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Old 4th Nov 2018, 03:36
  #533 (permalink)  
 
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A summary of ATC discussions was posted on Tempo. My translation of what was published as follows.

06:21:23 Pilot made first contact with ATC. [Altitude 900ft]

06:21.53 Pilot reported flight control problems and asked for holding position at 5000ft. ATC gave permission.

06:22:57 Pilot asked the speed of the aircraft from ATC. ATC responded 332knots.

(Note: no mention of ground or air speed, the bahasa is "speed of the aircraft")

06:29:39 Recorded data that the aircraft left 5000 feet.

(Note: It isn't clear whether this is ATC comms or just an observation)

06:29.55 Pilot given permission to return to arrival using runway 25 because of the flight control problem.

06:31:35 Pilot requested return to point ESALA because of weather and not sure about the altitude of the aircraft. Pilot requested 3000ft clearance with other aircraft.

06:32:00 ATC asked whether the pilot was ready to return to the runway. There was no response.

06:33.30 ATC contacted Batik Air 6401 to look for the position of Lion Air.
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Old 4th Nov 2018, 03:42
  #534 (permalink)  
 
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FAMO;

The bahasa actually says he requested the "speed of the aircraft" (kecapataan pesawat). Not airspeed nor ground speed.
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Old 4th Nov 2018, 03:52
  #535 (permalink)  
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The crew reported 'flight control problems'.

They also asked for a speed from ATC.

Then crashed the aircraft in VMC in what appears to have been a high energy dive.

Looking at the Tech Log, pitot static snag and 'feel diff' snag.

Anyone here ever flown a 737 without the feel diff working? The controls are extremely sensitive, especially at high speed, very easy to overcontrol. 737s tuck easily, and this will get out of the box quick. Gums I agree, we're probably looking at a structural failure, caused by over controlling due to feel diff failure, caused by pitot static problems.
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Old 4th Nov 2018, 03:57
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Which of course begs the questions...100 knots check? V1 Rotate? The crew acknowledged they had red SPEED flags on their PFD.
This is simply ridiculous piloting.
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Old 4th Nov 2018, 04:17
  #537 (permalink)  
 
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Originally Posted by AfricanSkies View Post

Looking at the Tech Log, pitot static snag and 'feel di
Anyone here ever flown a 737 without the feel diff working? The controls are extremely sensitive, especially at high speed, very easy to overcontrol. 737s tuck easily, and this will get out of the box quick. Gums I agree, we're probably looking at a structural failure, caused by over controlling due to feel diff failure, caused by pitot static problems.
There was no recovery at all in the dive which backs up the structural failure theory. They obviously had no control whatsoever in the high energy dive as considering the clear conditions (they would have seen the ocean floor approaching) there would have been some form of correction to avoid impact, but the numbers donít show this.

There is a lot of talk about pitot gives giving incorrect readings but this still does not explain why it dropped like a rock in VMC. There would have been some form of correction on the way down.




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Old 4th Nov 2018, 05:58
  #538 (permalink)  
 
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Originally Posted by AfricanSkies View Post
The crew reported 'flight control problems'.

They also asked for a speed from ATC.

Then crashed the aircraft in VMC in what appears to have been a high energy dive.

Looking at the Tech Log, pitot static snag and 'feel diff' snag.

Anyone here ever flown a 737 without the feel diff working? The controls are extremely sensitive, especially at high speed, very easy to overcontrol. 737s tuck easily, and this will get out of the box quick. Gums I agree, we're probably looking at a structural failure, caused by over controlling due to feel diff failure, caused by pitot static problems.
FEEL DIFF PRESS doesnít necessarily mean no or even diminished elevator feel. It is most likely to mean a loss of dual redundancy due to an Elev Feel pitot blockage or a loss of Sys A or B pressure. In that case, elevator feel will continue to function normally.

Itís a good point though, if they did lose elev feel, it possibly could lead to LOC or structural damage if not managed carefully.

I am surprised, however, that a fault with main air data could also cause a feel diff press problem. I thought they were essentially independent. I only fly NG, not MAX.

So this is an interesting malfunction (the previous flight).

Last edited by Derfred; 4th Nov 2018 at 06:11.
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Old 4th Nov 2018, 06:07
  #539 (permalink)  
 
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Anyone here ever flown a 737 without the feel diff working? The controls are extremely sensitive, especially at high speed, very easy to overcontrol.
I’m not sure exactly what you are getting at here. I would have thought that an amber FEEL DIFF PRESS light indicates that either A or B hydraulics has failed ( clearly there would be other indications), or, the elevator pitot system has failed.
When you say “ without the feel diff working”, do you mean without the elevator feel computer working?
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Old 4th Nov 2018, 07:44
  #540 (permalink)  
 
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Great advice given to me while flying the ERJ-145 many years ago, was to simply put the N1 needles to 12 O'clock if you are unsure of airspeed.
this gave a power setting that was pretty unlikely to induce an overspeed, but was enough to avert a stall as long as you flew roughly level. The thing would bumble along at about 200 knots if I remember correctly.
I think all aircraft could this sort of general advice, but I can also think of a few reasons why I've never seen it written down.
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