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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 29th Jan 2015, 13:36
  #2701 (permalink)  
 
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Thanks for your reply NoD.
the pilots should be monitoring it
Yeah,of course..but what if they werent?What if their attention was elsewhere?Like the weather?
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Old 29th Jan 2015, 14:48
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Out of curiosity - what is the 'French Quirk' described by Raanim and NoD?

Been flying the Bus for a couple of year now and never heard of it...
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Old 29th Jan 2015, 15:04
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I read that the FO was flying at the time of the crash, but I also read that the Captain took over, when they started to climb. This mixes things up. Do they mean that the Captain held the stick back until they stalled, or the FO? Maybe it wasn't the FO's fault after all? Maybe the leaked information is no good (who'da thought it?). I'd like to know if they tried using the apparently oft forgotten trim wheel to get their AoA under control.
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Old 29th Jan 2015, 15:05
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It's a few years since I flew the A320 but does the autopilot still have the "Expedite Climb" mode?

Is it possible this was selected (possibly in error)?
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Old 29th Jan 2015, 15:25
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Out of curiosity - what is the 'French Quirk' described by Raanim and NoD?

Been flying the Bus for a couple of year now and never heard of it...
I earlier, somewhat humoursly, just referred to "French Quirks".

The one later referred to it, when you go OP CLB, instead of smartly going to CLB power, and pitching for Climb Speed, it sometimes does nothing with the power, or even takes it off. It seems to be unsure of whether to "enter" the climb by leading with power or pitch? Some P2s fool it by winding the speed up for a bit, I just make some offensive remark about it's abilities and await it sorting it's life out (which it eventually does).
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Old 29th Jan 2015, 16:13
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N O D. I have never heard of the Frenck Quirk, but I have seen it pitch for climb speed before adding power if you are going faster than climb speed. That is how I was taught to fly a light plane although it never made much sense.
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Old 29th Jan 2015, 16:26
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Originally Posted by NOD
The one later referred to it, when you go OP CLB, instead of smartly going to CLB power, and pitching for Climb Speed, it sometimes does nothing with the power, or even takes it off.
What are you talking about ... One function of OP CLB is to maintain maximum climb thrust when A/THR is active.
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Old 29th Jan 2015, 16:31
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One function of OP CLB is to maintain maximum climb thrust when A/THR is active
Exactly So why sometimes does it take power off, or just do nothing, for 5-10s

It wasn't be who brought it up BTW!
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Old 29th Jan 2015, 17:01
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NOD I think what you're referring to is when flying a higher selected speed than cost index climb speed in the FMGC whilst level, then getting a climb clearance and pulling open climb then managing the speed. It's your naughty FOs flying higher than company CI, increasing engine internal drag and wasting fuel. In this case it'll come back to idle. It gets me once every 6 months. Pushing EXPED then straight away pulling OPEN CLB or pushing CLB locks the thrust at CLB thrust and prevents this.
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Old 29th Jan 2015, 17:29
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Originally Posted by Gysbreght
I have been looking in vain for the maximum bank angle the AP uses. I thought it would be either 25 or 33 degrees. Do you know if there is such a limit?
The following I have associated with A330/A340, and most likely is same for A320:-

If the AoB exceeds 45, the AP will disconnect and the FD bars will be removed.
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Old 29th Jan 2015, 17:33
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I have been looking in vain for the maximum bank angle the AP uses. I thought it would be either 25 or 33 degrees. Do you know if there is such a limit?
25deg I think it says?

However it seems quite happy to use up to 35deg to capture a Localizer
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Old 29th Jan 2015, 18:00
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Quote:

The one later referred to it, when you go OP CLB, instead of smartly going to CLB power, and pitching for Climb Speed, it sometimes does nothing with the power, or even takes it off.

What are you talking about ... One function of OP CLB is to maintain maximum climb thrust when A/THR is active.
For A320 reference:

A320 Panels / Displays: A320 Displays and Panels | Panels

FCL: Flight Control Laws | Direct Law - Description

Abnormal Attitude Law: Flight Control Laws | Abnormal Attitude Law - Description

Reconfig FCL: Flight Control Computers | Reconfiguration of Flight Control Laws Diagram

AP/FD Vertical Mode FMAs: AP/FD Vertical Mode FMAs | SRS
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Old 29th Jan 2015, 19:06
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"Veering left and wobbling" before the climb..

"Veering left and wobbling" before the climb..

Investigator: Co-pilot was flying AirAsia Flight 8501

Ertata Lanang Galih, a senior pilot and investigator, said after requesting permission to ascend, the plane was veering left and wobbling, CNN reported. Siswosuwarno said it then ascended to 37,400 feet in about 30 seconds, according to the broadcaster.
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Old 29th Jan 2015, 19:11
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[QUOTE] does the autopilot still have the "Expedite Climb" mode? [/QUOTE}

It does (actually a flight director mode) and it seeks to match climb thrust to green dot speed (roughly l/d max in the clean configuration). The engaged autopilot will grab on to the flight director and ride it up, but I don't think you'd ever see it command more than 4,000 fpm or so, even on the lightest 319.

I think I could rule out 'expedite climb' as a factor in this accident.

I agree that waiting till the investigation is complete before saying you know what happened is a good idea. But I feel pretty comfortable saying that a 6,000 fmp climb was not manually flown and involved some serious failure in the autoflight/reality interface.
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Old 29th Jan 2015, 19:41
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More stuff of uncertain provenance:

AirLive.net: BREAKING Pilots of AirAsia #QZ8501 Disabled Critical Computers Moments Before AirAsia Crash
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Old 29th Jan 2015, 20:05
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Originally Posted by NoD
So why sometimes does it take power off, or just do nothing, for 5-10s
Power off I doubt it, doing nothing could be just a question of perception as selecting OP CLB won't produce instantaneously climb thrust as such altitude especially if thrust has been significantly reduced just before selecting OP CLB.

But if you want to link a video to what you refer as a "French quirk" in the Airbus I'll be interested to watch it.

Originally Posted by Rananim
I read somewhere that when making a cruise climb in an Airbus and speed has been rolled back prior to climb THR set,that ATHR will actually command idle thrust.
It is normal for the A/THR in level flight to reduce the thrust to match a speed reduction request, but once OP CLB is selected, the request is for climb thrust. Selecting a different vertical mode such as V/S could be different ...

I am used to FLCH/LVL CHG where full climb thrust is automatically commanded even if speed selector rolled back.
And this is not different from OP CLB.
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Old 29th Jan 2015, 20:07
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Too bad the Indonesian Investigation Board refuses to indicate whether or not a full initial report on the crash will be released to the public.

Why am I not shocked.
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Old 29th Jan 2015, 20:13
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Trim and feel

When I first learnt to fly it was drummed into me that you used the controls to put the a/c where you wanted it and then trimmed out the stick forces - you did not use the trims to fly the a/c.
With hydraulic controls the manufacturers went to a lot of trouble to devise feel systems that told the pilot what he was doing. If you took the autopilot out and pulled the stick back then you would have to pull harder and harder to keep the nose up as the speed fell - there was a clue there!
Then along came FBW and we have a/c that no longer have feel but, worse still, trim the nose up as the speed falls with the a/p disconnected (sort of). Presumably someone decided that the feedback that feel provided was a waste of money or just impossible with a sidestick.
I flew t-tail jet airliners and we regularly hand-flew them because we enjoyed doing it and we were expected to be competent at it in the sim.
Incidentally I thought that pickle switches were used for dropping bombs.
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Old 29th Jan 2015, 20:22
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Too bad the Indonesian Investigation Board refuses to indicate whether or not a full initial report on the crash will be released to the public.
Maybe these leaks, that not only peak curiosity, but fuel wild speculation, will motivate the Indonesians to release the FDR data and the CVR transcript sooner than they planned.

It's possible, that the investigators just need more time to sort out why the computers were disabled prior to the incident, if that is indeed true. Why they were turned off, might not be evident at a glance.
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Old 29th Jan 2015, 21:01
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FDR - would the investigators please leak - "last recorded altitude"

I said very early on, when we first saw the ruptured pressure bulkhead, that the aircraft probably broke up, in the last few seconds, in the air, from overload, in a desperate pull-up.

I still think so, and I think the latest "information" could support that view.

The latest "information" - is that the "critical" computers were allegedly" switched off in the last few seconds.
That, if true, seems to me, to be consistent with a desperate last ditch attempt to force direct law.

How many seconds ? 5, 10, 15, 20 seconds ? The time is crucial.

Consider this hypothesis.
Out of control descending at around 12,000 feet per minute (to keep the numbers realisticly simple), which is 200 feet per second.
As best I can fathom, from weather reports at the time, local cloud base was probably about (verry rubbery) 1600 feet.

So, pop out of cloud - now visual, (it was just after local dawn) - 8 seconds to impact.

You, me, and every other pilot who has ever flown anything, are of course just going to sit there, fat dumb and happy, and just kiss our arses good-night.

Sure we will.

The other "information" that is out there, is interesting, not from what it said, but most pointedly, from what it did not say.

It is said that the fdr and cvr both stopped.

Two questions.

1. Did they stop simultaneously ?
(they were both mounted on the frames next to the missing ruptured sector of the pressure bulkhead).
(refer to the graphic showing the rupture outline on an installed bulkhead at post 1702 http://www.pprune.org/rumours-news/5...ml#post8819798)

2. What was the last recorded altitude ?
It will of couse be recorded as qnn, but we can convert it to local qnh from the met records.
Was it FL016, FL015, ..14, ..13, ..12, ..11, ..10, ..09, ..08, ....................... 01, ..00 ?

I may still be wrong of course.

Last edited by ventus45; 29th Jan 2015 at 21:16.
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