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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 Jan 2015, 16:49
  #1861 (permalink)  
 
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island_airphoto

Are you sure the super-cell would not be black on a new radar too? Very early on with the monochrome digital radar we had back in the day, we learne the black blobs in the middle of the green returns were the worst areas to fly, not holes in the storms. The physics of extreme rain absorbing the radio waves has not changed.
The old radars were monochrome. So how did you tell the difference between attenuation caused by a super cell and an actual gap? You couldn't. Well, maybe if you were highly skilled in the black arts you might be that kind of genius who just COULD tell the difference. Black holes didn't always appear neatly ensconced in the centre of green blobs. In the event I referred to the guys reported no green contour - just a nice clear (black) gap between the green blobs. A sucker hole.

With a modern contoured radar what would you expect to see in the same scenario?
A green contour, followed by a yellow contour, followed by a red contour, maybe some purple - then, what? A hole? Blackness?
Well it might depend on your radar set, but my suggestion is you don't go near RED or PURPLE, and try your best to avoid YELLOW and GREEN too.
That'll keep you safe.
No guesswork or black art required.

PS Radar attenuation is part and parcel of the system. If a sufficiently strong beam is emitted it could pass through all weather giving no returns. Not much good for WX spotting.
The signal needs to be of just the right strength to be partially reflected thus showing the WX. The snag is the weaker beam also suffers attenuation.
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Old 12th Jan 2015, 16:54
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Stormscope

Island Airphoto:

Yes, I remember flying around with a Stormscope, they detect static electricity from moving air currents, not necessarily lightning, and so are pretty good at telling you where the rough air might be... especially at low level, but I would expect a Stormscope would be overworked in an area of multiple active CBs - just too many dots! They were mostly intended for light - non radar - aircraft. I never flew a heavy aircraft with one.
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Old 12th Jan 2015, 16:59
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Originally Posted by Leightman 957
Tail section carried 3km is believable only if the tail was down current from the FDR. When we see current direction overlaid on a map of FDR and tail section locations it will be clear enough. Or more puzzling if the tail was cross stream or upstream.

I don't know anyone who does not with hindsight regret their choice of words from time to time, especially when in front of a crowd or on camera. I don't yet see anything contradictory in the 'explosive..air pressure' statement'. Sounds may be mis-interpreted, so must be considered separately. But a high volume, high velocity intrusion of seawater midpoint into a mostly horizontal fuselage could be expected to result in some cabin air overpressure. The paper bag analogy remains viable. Do recall also the fuselage frame pic of the skin neatly unzipped from the intact frame. The most likely cause of that is a sudden, very large, very uniform internal pressure. One must come up with an alternate cause for the unzipped skins to be able to disregard a fuselage overpressure. The video of the fuselage in situ which also shows virtually all cabin contents absent suggests a significant force having removed them.
Any fuselage "overpressure" would be caused by the force of water entering the cabin, and nothing to do with air pressure. Air easily compresses, water does not.
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Old 12th Jan 2015, 17:00
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Algol - we used to try and get a ground return on the far side of the storm to see if it was a hole or heavy rain and then tilt up to get an idea how hight the tops were. It was far from foolproof with the small antennas on a piston twin, sometimes you just had to keep away from all of it or heavy rain where you were would blind you to what was coming. I suspect that is still true - heavy enough precip where you are right now won't let you see very well if even worse is in front of you.
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Old 12th Jan 2015, 17:00
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Has this been posted before? Video that shows a rear door on the tail: BBC News - Navy releases new underwater footage of AirAsia plane


Last edited by Lost in Saigon; 12th Jan 2015 at 17:14.
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Old 12th Jan 2015, 17:04
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Lessons from AF447

I don't yet see anything contradictory in the 'explosive..air pressure' statement'. Sounds may be mis-interpreted, so must be considered separately. But a high volume, high velocity intrusion of seawater midpoint into a mostly horizontal fuselage could be expected to result in some cabin air overpressure. The paper bag analogy remains viable. Do recall also the fuselage frame pic of the skin neatly unzipped from the intact frame. The most likely cause of that is a sudden, very large, very uniform internal pressure. One must come up with an alternate cause for the unzipped skins to be able to disregard a fuselage overpressure.
Surely the impact that occurred with AF447 would be a good model for an intact aircraft hitting the ocean at relative high vertical speed? I do not recall there being anything that might have been described as some kind of cabin over-pressure 'explosion' due to water ingress. It seems very unlikely that the aircraft would hit in a sufficiently flat attitude, that would avoid a structural break up at critical stress points - meaning there would be no intact pressure vessel to "over-pressure".
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Old 12th Jan 2015, 17:38
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Impact comparison to AF447

Garage Years: Surely the impact that occurred with AF447 would be a good model for an intact aircraft hitting the ocean at relative high vertical speed?

The comparative issues of 8501 forward and vertical impact speeds are very much current conjecture. Despite the extreme depth of 447 wreckage, drift during descent still resulted in a debris field that was not gigantic. The degree of fragmentation of AF447 both by map and underwater photos compared to what little we know of 8501 debris at this early stage of recovery, and based on much conjecture, suggests relatively similar impacts might result in much different debris characteristics. The large area of 8501 tail section skin is about our only clue at present that suggests impact differences, but its large area is persuasive toward some causes.

AF447: Map of the debris field - Flight International
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Old 12th Jan 2015, 18:24
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I am hoping that the black box manufacture and the Australian ATSB are helping the Indonesia Govt retrieve the data from the boxes & right now they are just behind the scene on the deck of the ship during the news photo ops.

Mr S...that’s what I am worried about too...Airbus will want to place the blame solely on the pilots and not on any potential recalls/redesign/liability claims/potential loss of orders.

Googled “australia ATSB Airasia 8501” and this came up:


"The Australian Transport Safety Bureau (ATSB) has agreed to an Indonesian request to provide a flight recorder specialist when needed."

Last edited by BG47; 12th Jan 2015 at 21:20.
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Old 12th Jan 2015, 18:39
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BG47

Since it is Airbus, and in water, I am sure the French are there already.
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Old 12th Jan 2015, 18:53
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The french are there alright

Airbus and the BEA are both heavily represented. Photos of their people near the wreckage are evident in the press. Let's hope someone will be looking very closely over their shoulders to make sure the full and complete data from both from the FDR the CVR (when it is recovered) is made known and public. Whatever the data/conversations tell us about pitot tubes, FBW, direct vs alternate laws, crew training, P2F, decision making, cockpit resource management, etc, etc.
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Old 12th Jan 2015, 18:54
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Algol: I did not ask for the return to the older radars, what would be the point? You demonstrate that modern pilots would not be able to use it anyway.

If I am coming up on a large area of activity and need to find the best way through (and I don't have the luxury of a super-airliner like you obviously fly so cannot go over it) I could, using the old equipment, find the route I wanted. Since you don't know what I am talking about there is no point my explaining it to you as to how to go about this, but believe me it was possible.

Modern radar makes all those decisions for me and for a modern pilot that is fine and dandy. Quite often though, the modern radar is wrong.
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Old 12th Jan 2015, 19:16
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The french are there alright
I am sure that the Seattle branch of the agency have them permanently in their sights, so do not worry.
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Old 12th Jan 2015, 19:17
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PS Radar attenuation is part and parcel of the system. If a sufficiently strong beam is emitted it could pass through all weather giving no returns. Not much good for WX spotting.
The signal needs to be of just the right strength to be partially reflected thus showing the WX. The snag is the weaker beam also suffers attenuation.
Can you amplify that remark, preferably with a technical reference? I find the physics, as worded, difficult to relate to.
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Old 12th Jan 2015, 19:31
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Angry

Dr. Phillipa wrote:
I am sure that the Seattle branch of the agency have them permanently in their sights, so do not worry.
Would you care to spell that out in so many words, Dr.?
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Old 12th Jan 2015, 19:39
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McCloaked
@Livesinafield: "I think 3km is a lot I'm sure a 6kt current can't move 20kilos of metal that's sat in the sand"
At 6kt that distance represents about 20 minutes - if one of two pieces sinks straight away after surface impact and disruption, and the other floats for 20 minutes before sinking carried by a current flowing at that speed, that does not seem particularly unrealistic?
After it sinks the current will move the wreckage until it becomes anchored to the sea bed e.g. it skidded along the bottom until rotated so the VS lodged into the sea bed.
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Old 12th Jan 2015, 20:04
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Do any airliners fit stormscopes or equivalent technology? One of their selling points was that lightning was found in turbulent air, heavy rain or not. I liked the one I had way back when. Not as accurate as radar, but it worked.
I have one in a piston single, but it was next to useless *before* XM WX or ADS-B In's FIS-B. Now, I wouldn't pay to get it fixed or removed. Nothing replaces the Mk.1, Mod1 eyeball...
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Old 12th Jan 2015, 20:23
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There seems to have quite some time taken to find the wreckage, have their been any statements on whether the sonar transponders worked properly, and if they do why the search was so long ?
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Old 12th Jan 2015, 20:50
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Several other explanations have already been offered:
1. It was not know where the airplane went down
2. The strong currents spread out the wreckage
3. Some of the wreckage was buried in silt
4. There is a lot of other junk on the sea floor, for example wreckage from the battle of the Java Sea in World War II and other wrecks happening on these heavily traveled sea lanes.
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Old 12th Jan 2015, 20:54
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On Phil Gollin ... time to locate the recorders

There seems to have quite some time taken to find the wreckage, have their been any statements on whether the sonar transponders worked properly, and if they do why the search was so long ?
According to my A0283 plot (sorry to label it like this, but I try to keep track of different plots and their updates including my own). On December 29th there was an official statement about searching/listening for pings around a specific coordinate and a 15 miles radius around it. If these were nautical miles then the FDR was a the edge of that radius or just outside. If they were statute miles then the recorders were outside that area.

If they were on the edge then you should have to know the effective range of the listening devices. Ranges mentioned during recent investigations are between 500-2000 meters.

During the MH370 search I read a comment which stated reduced effectiveness in shallow water. Next to the fact that in general in shallow areas there is more traffic and vessel noise. This is quite a busy area. It suprised me that only now they have closed a sector for traffic for better listening. A few days ago a big vessel was sailing right through the area (if you may believe that tracking site). So to better answer your question, we need someone who can say something about effective range in shallow water. The floor here was sand according to an official statement. Depth at the location was 30-32 meters.
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Old 12th Jan 2015, 20:55
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This BBC article on the black box recovery contains a video segment in the middle showing the (presumably) AAIB CVR/FDR analysis room and a short interview with an accident investigator about recorder analysis.
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