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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 12th Feb 2015, 00:00
  #3201 (permalink)  
 
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One A320 simulator training syllabus included setting up the aircraft for practice stall recovery with ALT LAW.
The high altitude part was conducted clean at 25,000 ft. Hardly "high altitude"I would say.. The next was conducted first at 12,000 ft clean and then in the landing configuration at the same altitude. Nothing in the syllabus about IMC or VMC. To be realistic it should be in IMC where manual instrument flying skills would form part of the practice.

In view of recent loss of control events in Airbus aircraft which happened around 35,000 ft or above, it could be argued that stall recovery practice in the simulator should be conducted at that altitude or higher. After all that is where the accidents started.

Practicing a stall recovery at 12,000 ft in the landing configuration seems a trifle illogical since very few airports taking jet transports are that high. It would be more logical to conduct a landing configuration stall recovery on short final since recovery requires minimum loss of height for obvious reasons. As most pilots are aware, stall recovery technique is entirely different at high cruise altitudes compared to (say) 800 ft agl when the aircraft is in the landing configuration.
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Old 12th Feb 2015, 00:14
  #3202 (permalink)  
 
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Centaurus, trouble is the Sims (in general) are not programed to be representative at 35000 they handle the same as they do at 15000. + the stalls are not representative eg hold full back stick on a 330 sim at 35000 with an aft cofg (38%) and after some buffet the nose will drop. I.e conventional stall. But we know that this is not the case. IMHO this is criminal. Much of the stall teaching on sims is negative training. & no you can't do it for real as the aircraft "might" break if mishandled. So how would the crew really know what to expect of a FBW stall. I certainly don't (I can guess) & I've been flying them for 10 years or so.
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Old 12th Feb 2015, 13:37
  #3203 (permalink)  
 
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Back on topic for a moment..

Stall speculation aside.

When is the actual preliminary report due out? I thought it was late Jan?
Due to the fact they were keen(maybe not he best word) to cancel the majority of the salvage operations, surely the investigation team have a clear picture with the aid of FDR/CVR of what happened?
If so what's with the delay?
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Old 12th Feb 2015, 14:29
  #3204 (permalink)  
 
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An airframe every year or two falling out of the sky from cruise killing hundreds.
Sims not accurately programmed to train for scenarios that can and do happen in extremis.
Is it time to fit an ejector seat in an old 319/320 airframe and possibly also 330 and send a test pilot up to find out what REALLY happens. What the plane really handles like. What the recovery techniques all current pilots on type would lead to if done expeditiously. And not.
I'd prefer a man with an ejector seat to find out on his own that "putting 90 degrees of bank angle on to drop a wing and get the nose down" can be done, retains control authority an structural integrity. Rather than when I'm sat in seat 9A reading my book and planning a nice weekend.
Just saying...
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Old 12th Feb 2015, 15:12
  #3205 (permalink)  
 
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If the aircraft requires an ejector seat for pilot safety if it stalls/spins then I am not sure it should be certified as a commercial airliner.

Test pilots have deliberately test full-stalled various airliners without a bang-seat in the past, so it is something that can be done.
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Old 12th Feb 2015, 15:20
  #3206 (permalink)  
 
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Test stalled sure - but at or close to service ceiling? With a simulated full load, an imperfect trim with rearward CoG and perhaps some loss of situational awareness? (ie in a thunderstorm at night, rather than a clear day).


I fully appreciate the economics and the "tombstone imperative", however there are a growing number of the latter and what is clear from this thread is that there are few if any with any clear idea of what happens when a FBW aircraft enters coffin corner and then finds the corner. The sim is no help if its working with duff data. Passing a sim check or even playing with the sim in some rare free sim time is no bloody good if the real thing is different.
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Old 12th Feb 2015, 15:36
  #3207 (permalink)  
 
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If, in high altitude stall test, for real with a test pilot(s) on board, they cannot get the AOA reduced to recover from the stall there is another option as a very last resort. Just to save the test crew.

Why not have a drone parachute attached to the rear of the fuselage? On deployment, the drag from the chute would certainly lower the nose, by raising the tail to a sufficient degree for recovery and could be cut away when or if it has done it's job.

One would think this has been thought of by much smarter people than I. However upon learning these aircraft haven't been (intentionally) stalled, leave alone deep stalled at high altitude, one can only wonder at the mentality. The uncrashable/unstallable mindset, does give it a way a bit.

Last edited by Sop_Monkey; 13th Feb 2015 at 18:08.
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Old 12th Feb 2015, 15:37
  #3208 (permalink)  
 
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@captains log - reports due

As far as I can read and understand it ...

When is the actual preliminary report due out? I thought it was late Jan?
Yes it is already out at the end of the 1 month period set out by ICAO ... and sent to ICAO and parties involved ... but certainly not made public ... in spite of the expectation of some PPRuNe posters.

KNKT/NTSC have literally stated (look at previous posts - including a translation of the KNKT interview video) that they 'have the key' to the accident.

KNKT suggested that they would have a press conference later divulging more information. Later that changed to - it would be adressed during an already scheduled annual KNKT report presentation - but it was not (as far as I could see - even digging deep in local Indonesian press reporting).

Most public information is from a parliamentary commission presentation of which fragments can be found on-line.

Due to the fact they were keen(maybe not he best word) to cancel the majority of the salvage operations, surely the investigation team have a clear picture with the aid of FDR/CVR of what happened?


The salvage as such already faltered before they had had time to read the flight recorders. So I find that cause-effect highly unlikely.

If so what's with the delay?

I asked that recently. Nobody knows apparently. And most surprising, nobody appears to be upset about that.

Interesting is that originally KNKT stated they expected the final report in 1 year. Recently statements have reduced that to 8 months.

For an innocent bystander it is quite confusing. The state quite fast that they have 'all' the answers. But will publish quite late ... not having a Prelim ... we have to wait at least 8 months for a Final ... which by definition will have a Public version. It would be nice to get some public KNKT explanation of course.

Last edited by A0283; 12th Feb 2015 at 15:51. Reason: Afterthought - final report statements
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Old 12th Feb 2015, 15:47
  #3209 (permalink)  
 
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Sims not accurately programmed to train for scenarios that can and do happen in extremis.
I don’t think that’s as important as people make out. The detailed response of an airframe to “edge of the envelope” events in real life is often highly dependant on things like CG, yaw/roll/pitch angles, asymmetry, entry rate, wing loading, air density and many other factors. Every one is different, sometimes remarkably so.

What needs to be trained is:

1. High-altitude stalls are BAD, don’t go there.
2. If you do end up there, it will most likely need control deflections and pitch angles that you’ve never used/seen before to get out of it.

If the sim is up to replicating that, then it’s good enough. We are trying for a generic recovery procedure, not a specific finessed one.
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Old 12th Feb 2015, 16:10
  #3210 (permalink)  
 
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Test pilots have deliberately test full-stalled various airliners without a bang-seat in the past, so it is something that can be done.
From an interview I saw with an airbus test pilot, he said that they only test a stall close to the edge of the envelope with high energy. The AF447 and air asia stall are far more lethal because the a/c has lost nearly all energy and have the engines at idle. This requires a lot more time to recover the lost energy. Clearly there is a huge difference between a best case stall and a worst case stall. I think it reasonable to want the ejector seat for a Chuck Yeager willing to take an a/c so close to unrecoverable.
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Old 12th Feb 2015, 17:20
  #3211 (permalink)  
 
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Originally Posted by Sop Monkey
Why not have a recovery parachute attached to the rear of the fuselage?
Don't know. Will it rip the rear pressure bulkhead off, or just pull the tail away when it's unfurled?
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Old 12th Feb 2015, 18:12
  #3212 (permalink)  
 
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Originally Posted by feedback View Post
Don't know. Will it rip the rear pressure bulkhead off, or just pull the tail away when it's unfurled?
He was only talking about doing this to allow test flights to be carried out safely, so it wouldn't be a problem - the test aircraft's structure would be reinforced as necessary. This method is routinely used for fast jet spin testing (although obviously you do also have the benefit of an ejection seat if things don't work out in those circumstances). An alternative would be something along the lines that Airbus have already used for A400M stall testing, a downward-firing rocket in the tail.

I make no comment on whether any of this is necessary, merely observing that it's readily available and deployed technology within the flight test community.
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Old 13th Feb 2015, 08:02
  #3213 (permalink)  
 
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Originally Posted by A0283 View Post
From that professional viewpoint you can only be very very happy with the approach taken by the Taiwanese ASC. And at the same time negatively surprised by the approach taken by the Indonesian KNKT/NTSC.
Surprised by ASC releasing DFDR readout quickly - yes. Surprised by NTSC - well, not exactly, bearing in mid the outcome of MI185 investigation. Regarding the country of registration and nationality of the captain, stakes are far higher now but DFDR and CVR are read out so evasion will be more difficult.

Originally Posted by A0283 View Post
In the AirAsia case the (investigation) authorities have published few preliminary facts (radar, FDR and CVR data). But have published some short ‘final opinion’ conclusions( {we know what happened} “ we have the ‘key‘ “ – and – “it was not a suicide”).

(...)

In the Indonesian case no-one, not a single mention on PPRuNe I think, suggested a suicide.
It is possible that recorders' readouts prompted NTSC to jump the gun.
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Old 13th Feb 2015, 13:58
  #3214 (permalink)  
 
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Whut?

xcitation
From an interview I saw with an airbus test pilot, he said that they only test a stall close to the edge of the envelope with high energy.
Exactly what is a "stall close to the edge of the envelope with high energy"? I'm familiar with accelerated stalls, power-on stalls, power-off stalls, PA and CR configuration stalls, etc. but that's a new one to me.
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Old 13th Feb 2015, 14:38
  #3215 (permalink)  
 
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Energy Management

My understanding is that kinetic energy is the work done to accelerate the mass of the a/c. This is increased by engine thrust or trading potential energy (losing altitude and claiming the acceleration from gravity). If you have low PE and low KE then total energy is low which is very dangerous.

Update: Boeing have a good description here...Aerodynamic Principles of Large-Airplane Upsets (Aero Magazine, 1998 Q3 edition)

Last edited by xcitation; 13th Feb 2015 at 20:47.
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Old 13th Feb 2015, 20:35
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My understanding is that kinetic energy is the work done to accelerate the mass of the a/c. This is increased by engine thrust or trading potential energy (losing altitude and claiming the acceleration from gravity). If you have low PE and low KE then total energy is low which is very dangerous.
It's a while since I did A Level Physics but here goes:-

Gravitational potential energy is the energy stored in an object as the result of its vertical position or height. The energy is stored as the result of the gravitational attraction of the Earth for the object.
So the higher you are (above earth) the more the potential energy?

Kinetic energy is the energy of motion. An object that has motion - whether it is vertical or horizontal motion - has kinetic energy.
KE = 0.5 m (V)squared - where m is mass and V is speed. Double the speed and you quadruple the energy.
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Old 13th Feb 2015, 21:42
  #3217 (permalink)  
 
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X citation and others

Essentially what is being inferred here is that stall testing is done with a lot of potential energy. ie at a high altitude and not close to the ground.
In this context the comments (some of which have been allowed to stay) make sense. One does not practise stalls close to the ground even in a c152!

However your later comments re selecting flight idle and equating that with low energy are incorrect. For stall recovery the sequence has to be reduce the AofA then a short while later increase power. Selecting toga or equivalent merely causes a pitch up which makes reducing the AofA almost impossible.
Increasing the power does not increase'the energy state of the aircraft'.
In a stall situation you do not go faster nor do you increase altitude, you merely descend in a stable stall like AF.
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Old 13th Feb 2015, 22:13
  #3218 (permalink)  
 
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Originally Posted by henry crun
Scale effects well known.
Are they? Scale effects are expressed in the Reynolds number, which considers viscosity. Combine that with Mach number, which considers compressibility. Then you'll see the need for full-scale testing.
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Old 14th Feb 2015, 00:47
  #3219 (permalink)  
 
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To clarify my comment about idle detent; N1 take time to spool up when changing from prolonged idle to TOGA. This is another consideration when a/c is falling out of the sky and flight control is urgently needed e.g. Habsheim incident - low total energy, low N1. The impression I got from the airbus test pilot was that stall testing is done in a very controlled manner changing flight controls as little as possible. This protocol allows the a/c to return to the flight envelope very quickly with only small stall excursions. It's not cutting engines, full stick back, see what happens.
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Old 14th Feb 2015, 05:01
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From an image of wreckage, it seems that the screw was snatched during the impact. It remained attached to THS
http://www.mediafire.com/view/1hh6qg.../jackscrew.jpg
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