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Air Asia Indonesia Lost Contact from Surabaya to Singapore

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Air Asia Indonesia Lost Contact from Surabaya to Singapore

Old 21st Jan 2015, 19:43
  #2321 (permalink)  
 
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"my first impression is that the 7000 fpm climb is not necessarily pilot induced but instead it is a 7000 fpm updraft in a CB .

Which in turn will strongly reduce IAS and increase AOA : hence the stall ."'

Joe2
This has been dealt with before. A rising air current (updraft) does not necessarily reduce IAS. It actually adds energy to the aircraft. Gliders do not automatically stall in a thermal just because they go up. The problem is the attitude it may induce, which may be at such a rate that the automatics cannot deal with it and IAS reduces.

People are thinking, but you are not reading before posting.
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Old 21st Jan 2015, 19:47
  #2322 (permalink)  
 
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Originally Posted by nose,cabin
Logic is the computer follows the two inaccurate ASI which over read ie barber pole.
Only if the two frozen pitot statics deliver very similar misreading speed values and also both freezing at pretty much the same time and rate which is quite improbable.
Much, much more likely in such a situation: ADR disagree and Alternate 2.
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Old 21st Jan 2015, 19:54
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Originally Posted by Leightman 957

>Why would you think the ATC authorized course deviation that they had was not enough?

Respectfully, 8501's wreckage.
A course deviation (including up to a 180) should have been enough. At this point it does appear that they made some bad decisions and encountered severe weather.

I still don't believe the pilots made a conscious decision to climb to get themselves out of a bad situation. I suspect the aircraft was out of control due to severe weather that exceeded the capability of both the pilots and the aircraft.

It does look a lot like AAF447 "Part Duex" but the CVR and FDR will soon tell all.
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Old 21st Jan 2015, 20:00
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Joe

my first impression is that the 7000 fpm climb is not necessarily pilot induced but instead it is a 7000 fpm updraft.
Unlikely.

A big cell might have an updraft of 5,000 ft per min, but this aircraft was doing 11,000 ft per min. Now that is the max updraft from the absolute largest of supercells. Were conditions that bad? And if so, why was a cell of this size not avoided? And the engines are not going to contribute much to the climb, as I doubt if you could get 1,000 ft per min from the engines at that altitude, without a zoom climb.

The more likely scenario is a smaller updraft upset, combined with and exacerbated by poor handling of the upset, pitching the aircraft up. We shall see.

As an aside, I have not flown the 'bus. So to the 'bus drivers out there, what would it do, if you deliberately pulled back to 40 degs pitch up, to try and stall it? Would it foresee and cope with the aggressive attitude, or would it go out of envelope and stall?
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Old 21st Jan 2015, 20:15
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So to the 'bus drivers out there, what would it do, if you deliberately pulled back to 40 degs pitch up
In Normal Law you could not, it limits you to 30nu. As IAS falls off, AoA increases and AoA protections kick in.

In essence, if everything is working, and there are not undue external influences (weather) you cannot abuse it.

Systems / sensors U/S, significant weather, or turning things off, you can abuse it like a normal aircraft.
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Old 21st Jan 2015, 20:18
  #2326 (permalink)  
 
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problem is the attitude it may induce, which may be at such a rate that the automatics cannot deal with it and IAS reduces.
RifRaf3, concisely put.

Problem:
If one (the pilot, not the automatics) isn't actively engaged in attitude flying as things begin to go all wrong, then that old fashioned method of aviation that served us so well for so long when flying on instruments -- a working instrument scan and attitude/power flying -- has to be asserted into the control scheme by the meat based system. This will happen with a delay of "x" time by a crew that may have been, up until that point, watching the smart plane fly for them ... and it may not necessarily have been attitude flying while it was so doing.

Result? Flight deck crew begins the game of "catch up" if, as suggested above, the system logic finds itself in the wrong mode and starts to "gracefully degrade" to a less automated mode.

As much as FBW is not my personal cup of tea, this is not an inherently bad design philosophy -- auto degrading to keep the automatics from going utterly haywire -- but it is one that requires the meat based pilot to be "in the game" with the scan going when that degradation occurs. It also requires that the meat based system be very knowledgeable, in depth, about his complex system.
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Old 21st Jan 2015, 22:24
  #2327 (permalink)  
 
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timeline

from post 2303 ref reuters report: the transport minister..At 6:17 a.m. on Dec. 28, three minutes after air traffic control unsuccessfully tried to make contact and asked nearby aircraft to try to locate QZ8501, the A320 turned to the left and it began to climb from its altitude of 32,000 ft (9,750 meters), Jonan told a parliamentary hearing.

Now we have three minutes before the turn and climb, and after ATC unable to contact. This is an intriguing length of time.
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Old 21st Jan 2015, 23:03
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thru all my career, from PPL to Comm to ATP, 17000hrs (retired) Capt B737, I was always taught about weather "AVOIDANCE", but the norm nowadays seems to be for weather "PENETRATION" albeit in the "least return areas" of the WX Radar.
Irrespective of Boeing or Airbus, it is the duty of all airline Captains to deliver his passengers safely at destination, and that means "AVOIDING" the weather, rather than punching into weather, and hope to find the smoothest path thru, then do so.
The passengers didn't sign up for a "test of the pilots skills" or for a ride with the the most brave and daring Captain, and it is thus not our place to give them the ride of their lives, but rather a smooth uneventfull ride, where the only complaints are about the lack of bubbles in the champagne in business class.

Before I retired, in my company there were Captains, who's level of bravery exceeded mine, when it comes to weather penetration vs weather avoidance, and minimum fuel uplift, thus no options but to barge on straight ahead.
I am glad that I made it to the "old pilot" phase beyond the "bold pilot" phase, and now I can sit comfortably at home trying to make sense of this lot.
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Old 21st Jan 2015, 23:18
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Quote:


60% of known ice crystal icing events occur in the tropics. If the rate is beyond the ability of the pitot system then I would infer that the blockage would occur at almost identical times and magnitude because of the homogenous nature over the small frontal area of the aircraft. Thus, resulting in an artificial overspeed due to it climbing. It is very difficult for any pilot to do something when the systems designed to protect you are now putting you in harm's way, against your intentions. I've never had it in the aeroplane but have done it in the sim and its the most uncomfortable feeling having FULL forward stick whilst the aeroplane pitches up opposite to your inputs.


A very unsettling possibility indeed.
I do not know what the polling frequency is for the Airbus flight control computer, but afaik it is more than 20x per second. That then raises the question of how many polling cycles are required to make a determination that the sensors disagree or that they agree on a wrong value, as suggested above.
Could someone please help elucidate the logic and timing constraints involved.
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Old 21st Jan 2015, 23:22
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Screaming Warnings

Just saw "screaming" on CNN. Being bilingual (English and Spanish) I know that translations of exact meaning between two languages, even when you are comfortable with each, is a difficult, maybe even impossible task. This is particularly true when the description in one language is a simple statement of fact, but the only word you can think of in the other connotes emotion.

Just looking at the map of Indonesia leads me to believe there may be many meanings for a word over very short geographic distances. This would not apply to pure facts, e.g. "The stall warning was heard from Time X to Time Y".

"Screaming Alarms, Warnings, Bells, Verbal Communication", whatever, probably just means there was a lot going on. "Persistant, Overwhelming" or in the case of verbal communications, "Highly Concerned", would probably have been better choices. But the best description would avoid any adjectives at all.

Last edited by thcrozier; 22nd Jan 2015 at 00:15.
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Old 21st Jan 2015, 23:34
  #2331 (permalink)  
 
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Pitot static frozen

Twice I have experienced this event.

Flying F/L 370 with sat -45degreesC when temp increases to 0 degrees c.
Boeing have a QRH checklist for this.
No auto throttle, no EPR.
No TAT. Set power and fly attitude. Usually max contin. N1 to hold altitude.

Not sure why, but lasts 10 minutes than back to -45 c.
Perhaps hot air from volcanic activity. Who knows.

This is taught only by experienced pilots.
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Old 21st Jan 2015, 23:37
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I am not a pilot but I have read about runaway rudder trim issues on the Airbus.

Given that we've been told the weather was a contributing factor but apparently not the main factor, could an issue like this cause significant upset?
I recall the rudder hard-overs on 737s years ago and the incidents it caused, though I imagine this is not exactly the same....

Forgive me if I this is a foolish notion! Just trying to learn.

Really enjoy this forum!
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Old 21st Jan 2015, 23:53
  #2333 (permalink)  
 
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From experience flying in the tropics, if you don't like the metsat picture you stay on the ground until a clear corridor is doable upwind of the system. If that fails to appear you default to plan A.
As neatly put previously, buying a ticket for a scheduled flight is an exercise in trust, rather than a test of ability, especially as those abilities are increasingly determined by the CFO as opposed to the DFO.

Last edited by Teddy Robinson; 21st Jan 2015 at 23:55. Reason: Typo
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Old 21st Jan 2015, 23:53
  #2334 (permalink)  
 
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FYI - if ice plugs the pitot tube quick enough to trap the air in there, the speed may not go down. If the airplane gains altitude the "speed" goes UP because the difference between the trapped pitot and static air gets bigger.
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Old 22nd Jan 2015, 00:29
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@silverstrate, eklint,... - on available data

What I have done is: Taken the numbers from the image posted by eKlint on Pprune today (apparently an extract based on official information), add the numbers from the posted video of Indonesian transport minister Jonan (url posted too today), sequence the data, make the numbers consistent.

What you get is a flighttimeline in seconds in column1. Then the flight levels in column2. And subsequently 2 different fpm columns, 3 and 4. And in column5 the short description.

I have used 2 different fpm columns because stated fpm, and fpm calculated from data, give different outcomes. Example – the maxclimb stated is 11,100 fpm, but also stated is 1,500 ft in 6 seconds, which calculates on average as 15,000 fpm.

As A0283 Ihave just crunched the available numbers. Have not included an A0283 or anyone else’s opinion. And leave it to the reader to either use the information with care, or wait for the publication of the final report (which will at least be 1year from now according to KNKT). Please, don’t shoot the cruncher.

sec.....ft....fpm3..fpm4...................description...... ....................

000 32000 0000 0000 ATC unsuccessful in making contact with QZ8501,

180 32000 0000 0000 A320turns left, and begins climb from FL320,

186 32000 1400 0000 after maneuver to left, suddenly pitch up/climb

201 33700 6000 6800 aircraft has climbed 1700 ft from its original level

201 33700 6000 6800 rate of the climb increased rapidly

208 35200 8400 12857 rate of the climb increased further

214 36700 11100 15000 rate of the climb reaches maximum

214 36700 11100 15000 aircraft reaches its maximum altitude

234 36700 0000 0000 aircraft appears to stall

240 36700 -15000 -15000 aircraft begins to fall

246 35200 -15000 -15000 aircraft falls

306 27300 -7900 -7900 aircraft reaches rate of descent of 7,900 ft per minute

306 27300 -7900 -7900 aircraft reaches rate of descent of 7,900 ft per minute

306 27300 -7900 -7900 shortly after touching heights; <*>

331 24000 -7900 -7900 aircraft reaches 24,000 ft, at which point it disappeared from the radar.

Note 1: <*> Not clear to me what “touchingheights” means, is it the theoretical LOS point?>

Note 2: During his presentation in parliament Minister Jonan showed a graph (numbers on video un-readable to me) of the flight path projection. Shows the plane went left, and a small diameter tight spiral at the end. Would be interesting to be able to match this with the changes in climb and descent.

If you have an informed opinion on the numbers it would of course be great if you want to share this. Another option is to send A0283 a PPrune private mail.
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Old 22nd Jan 2015, 00:53
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Teddy Robinson from Bear Island; one of the smartest posts on this subject I have read !
I have taken off, seen a wall of red in front of me, turned around and gone back to land. I, my F/O and my passengers have safely and comfortably sat on the tarmac and waited for the frontal line to pass through - it's not that difficult to do.
And yes you are correct, the CFO's control the show these days. That is, if you have not got the experience, airmanship and courage to tell them to get stuffed !!


Role on.....
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Old 22nd Jan 2015, 00:59
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alien roll:

I have taken off, seen a wall of red in front of me, turned around and gone back to land. I, my F/O and my passengers have safely and comfortably sat on the tarmac and waited for the frontal line to pass through - it's not that difficult to do.
Amen.

But, what about some of today's predatory employers?
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Old 22nd Jan 2015, 01:45
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has anyone heard a reasonable scenario on any major tv network, or is it all a bunch of ...
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Old 22nd Jan 2015, 01:51
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Twice I have experienced this event.

Flying F/L 370 with sat -45degreesC when temp increases to 0 degrees c.
Boeing have a QRH checklist for this.
No auto throttle, no EPR.
No TAT. Set power and fly attitude. Usually max contin. N1 to hold altitude.
Fits the scenario of "Ice Crystal Icing" or ICI. When it's sufficiently severe, it can ice up the TAT probe - the combination of probe heat/melting ice gives the 0 degrees C (and on EPR engines, often the inlet probes, hence bad or no EPR). Supposedly, above 30k it's too cold for super-cooled droplets to exist - instead you get ice crystals. They bounce of cold surfaces but melt and stick to heated surfaces (e.g. probes) - the first crystals melt, but in high concentrations the new crystals re-freeze the melted water and the probes can ice over (also can form ice in the engines which has lead to flameouts when it sheds). TAT probes are particularly susceptible to ICI icing since you can't throw too much heat in without affecting the measured temperature. Pitot probes don't have that problem and have lots of heat. Hence ICI icing of pitot probes is rare, but it has happened (AF 447 being a tragic example).
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Old 22nd Jan 2015, 01:54
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then that old fashioned method of aviation that served us so well for so long when flying on instruments -- a working instrument scan and attitude/power flying
Lonewolf

This is a lost skill.And therein lies the rub.Automation/progress facilitates P2F,200 hour jet pilots and cost saving as it transforms the role of the "pilot" into a button-pushing "flight manager".And thats what they want.The manufacturers(Airbus),the beancounters,the insurance guys and even the management pilots.But if automation and all the wizardry fail, there is no pilot anymore to take over,just a flight manager.
Re-introduce airmanship into the flight deck.Now.Simple airmanship would have told them that you never flirt with bad weather,you never avoid storms vertically,and you never ever wait for an ATC clearance to save the lives of you and your passengers.Speed margin is essential.Todays pilots flying near/in storm cells at FL410 should be shot.Go too close to a storm and you had better be at opt alt minus 4k with speed halfway between barber pole and min maneuver.That will give you a chance.A fighting chance.
I know that the "Airbus factor" will come into this one and it will be interesting to see just how the Airbus design philosophy helped or hindered the pilot and whether or not the investigators will call a spade a shovel even with the French there in force.
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