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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 7th Jan 2015, 09:44
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If you click onto the posted link and not look at the posted pictures, its a lot clearer to see that its missing paint.


http://www.news.com.au/travel/travel...-1227177443383
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Old 7th Jan 2015, 09:50
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Originally Posted by Phalanger
Propduffer, you have not got enough significant figures in either the times or coordinates to make the speed assumptions you have given (remember you are calculation movement across the globe from these figures, not straight knots). In addition you have assumed a linear path in two dimensions. There is no way your figures are near correct.
RNP and all trajectory based systems are based on ground speed. The calculations from ADS-B position report time of generation (in each ADS-B position report) can be used to create ground speed. If you want airspeed that is also within the body of the ADS-B report.

Problem is FR24 does not give access to the actual ADS-B reports.
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Old 7th Jan 2015, 09:56
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Flightradar24 data is from plane

The data provided by Flightradar24 here is the actual ADS-B data sent by the plane

https://twitter.com/flightradar24/st...69337023840256

The timestamps are from the aircraft. It does not matter how long it took to be received, or by whom, or in what order.
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Old 7th Jan 2015, 10:00
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Originally Posted by Propduffer
Although I don't know the location or the type of radar that "Tracked" QZ8501 I don't believe it possible for even heavy rain to attenuate the return from either passive or primary radar.
Secondary radar is not normally attenuated by rain but primary radar is always attenuated by rain. The shorter the wavelength the more attenuation. An ATC radar of the order of 10cm can be close on completely useless in heavy rain despite technical mitigations.
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Old 7th Jan 2015, 10:34
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There is some interesting data in the report at http://www.bea.aero/en/enquetes/flig...nal.report.pdf where on pages 12 and 13 it would seem that locating and recovering the CVR and FDR within a few days is the exception rather than the norm. So recovery of these items for the current accident flight in the next few days would be within the normal time range.
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Old 7th Jan 2015, 10:41
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The data provided by Flightradar24 here is the actual ADS-B data sent by the plane

https://twitter.com/flightradar24/st...69337023840256

The timestamps are from the aircraft. It does not matter how long it took to be received, or by whom, or in what order.
ADS-B from the SSR Transponder is not time stamped by the aircraft. The receiving station adds the time stamp. There is a mechanism for allowing the receiving station to compensate for various latencies in the aircraft system (known as the T-bit). However this is seldom implemented in current installations. Consequently velocity calculations from the ADS-B position reports alone should not be considered reliable. HOWEVER ADS-B does transmit the aircraft's own calculated velocity (usually ground speed) at the same rate that it transmits position (twice per second). This velocity should be considered perfectly reliable but I am not sure if Flight Radar carries the velocity component.
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Old 7th Jan 2015, 10:44
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Hopefully the data recorders are preserved in the tail.

Can anyone advise the origin of the altitude recorded on the FDR. Pressure only? Or GPS also?

Maybe I am missing something, but it all seems a bit unsatisfactory. We measure a pressure using ports that are subject to problems such as icing. We then take this pressure and derive a flight level based on 1013. However if ambient temp or pressure was to change as you enter a cell (and the chaotic winds within a cell are due to pressure differentials), this would distort any change in FL that was being measured.

I never quite understood this when we got the data for AF447. Obviously there were significant altitude excursions during the upset. But to what extent were there measured excursions corrupted by sudden pressure (or temp) changes.I recall AF447 pilots noted a dramatic increase in OAT shortly before it all went wrong.

Furthermore, could a perceived change in FL cause the automatics to respond so as to correct this, and could this compound the problems due to pitot tube freezing and loss of valid airspeed.

There seem to be a lot of links in the chain between what we measure and what we derive from it.
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Old 7th Jan 2015, 10:56
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ADS-B messages, for reasons I have never understood, do not carry a timestamp, nor any other unique identifier apart from the sender airframe hex code.

FR24, openatc, or any other ADS-B receiving network therefore does not possess any reliable way to discount duplicated messages received from their remote feeders.
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Old 7th Jan 2015, 11:20
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If what they've found is upside down, does this mean that the main part of the fin has knifed itself into the mud? Could this make it even harder to retrieve?

Can anyone identify which parts we're looking at in the photo of what looks to be internal workings of the tail?
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Old 7th Jan 2015, 11:34
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Timing of ADS-B messages

Physicus

Yes, you are correct and I was wrong. ADS-B messages do not have to contain timestamps and mostly do not. However, it is possible to include them along with any other extra pieces of information in optional parts of broadcasts.

The timestamps are added by the (very accurately timed) receiving stations for FR24 usually.

However, for the purposes of the last minute of the (recorded) broadcasts from QR8051, there are no repeat positions (except for the last two which we are ignoring). Thus it is safe to assume that there is just one ground station responsible for the timestamps.

Given the speed of light (meaning that time received is less than one millisecond from time broadcast), we can use the timestamps given as being perfectly accurate, even down to the millisecond. That is as far as calculating positions is concerned.
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Old 7th Jan 2015, 12:03
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@AirScotia "Can anyone identify which parts we're looking at in the photo of what looks to be internal workings of the tail?"

Does this image help: http://www.flightglobal.com/airspace...il-cutaway.jpg
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Old 7th Jan 2015, 12:09
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'Black box must be read in Indonesia,' says Minister for Maritime Affairs.

QZ8501: Blackbox Must Be Read In Indonesia, Says Minister

Does Indonesia have the technical resources to deal with the FDR/ CVR? I assumed they'd send them to Australia.
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Old 7th Jan 2015, 12:14
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'Black box must be read in Indonesia,' says Minister for Maritime Affairs.
That statement makes me feel uneasy...
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Old 7th Jan 2015, 12:16
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Gen question - What band radar / freq / prf are onboard weather radars using?
Can they be switched from hi to lo gain for eg?
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Old 7th Jan 2015, 12:18
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Originally Posted by multycpl
If you click onto the posted link and not look at the posted pictures, its a lot clearer to see that its missing paint.


AirAsia Flight QZ8501 plane tail confirmed found
Here is another link to a larger sized photo: http://media1.s-nbcnews.com/i/newscm...7106c6972c.JPG


Last edited by Lost in Saigon; 7th Jan 2015 at 15:06.
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Old 7th Jan 2015, 12:35
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Channel News Asia live blog reporting that authorities say tail section identified is 10 metres in length and relatively intact. They are therefore hopeful of the possibility of recovering "black box". Earlier "a signal" had been detected from tail section but could not be re detected later.

SAR efforts continuing as of 2043 (GMT + 7).
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Old 7th Jan 2015, 12:45
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Air Scotia

For what it's worth, Channel News Asia also stated that "authorities" believe that the aircraft hit the water in a left hand roll, and the tail section identified (which represents a reasonable percentage of the hull length) does appear to be upside down. There is a good deal of mud so possible parts are submerged.

I have no SAR expertise however so others may comment.
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Old 7th Jan 2015, 12:46
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Originally Posted by Dont Hang Up
ADS-B from the SSR Transponder is not time stamped by the aircraft. The receiving station adds the time stamp. There is a mechanism for allowing the receiving station to compensate for various latencies in the aircraft system (known as the T-bit). However this is seldom implemented in current installations. Consequently velocity calculations from the ADS-B position reports alone should not be considered reliable. HOWEVER ADS-B does transmit the aircraft's own calculated velocity (usually ground speed) at the same rate that it transmits position (twice per second). This velocity should be considered perfectly reliable but I am not sure if Flight Radar carries the velocity component.
You are being a little pedantic To save space as they are trying to crunch a lot of information into a very small space, a 'time of applicability' is sent that refers to even and odd numbered periods (called epochs) of 0.2secs within a longer time frame. This encoding of the UTC time allows the ground station to recreate the 'time of applicability' of the geographic (surface) position data - the latitude and longitude. This is possibly not a worthwhile exercise for FR24 and others but the information is there in the ADS-B message. (See RTCA DO-260B Appendix A A.1.4.2.3.1)
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Old 7th Jan 2015, 12:48
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The Strait Times reports:

SURABAYA - AirAsia will offer compensation of about US$100,000 (S$133,000) for each passenger of the ill-fated Flight QZ8501, in addition to the initial payment of US$24,000 that was offered earlier to family members, CNN has reported.

Earlier, The Wall Street Journal reported that the airline was conferring with families individually on the initial compensation, meant to help them with their immediate financial hardship.

The Indonesia AirAsia flight went down in bad weather in the Java Sea with 162 people on board, including 155 passengers. No survivors have been found so far.

Some families had declined the initial offer without further information about compensation, citing confusion over the wording of the letter and reservations about the airline's practice of approaching families individually, the Wall Street Journal report said.
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Old 7th Jan 2015, 13:16
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Quote: @AirScotia "Can anyone identify which parts we're looking at in the photo of what looks to be internal workings of the tail?"

As former A-320 rated maintenance engineer (few years experience on the type) and seasoned scuba diver maybe I can help:

The photo of registration marks shows bent metal skin, that shed (I assume thick layer of) paint along the bend, exposing primer coating. The fact it looks like upside down is, by my opinion, irrelevant as we do not know the orientation of camera-could be very difficult to take if reported currents are truly in the area of 4-5 kts. Movement of water is witnessed by short lines on photo, created by fast moving particles, suspended in the water.

The photo of red painted part with letters Ai... (Air Asia) shows probably left side of vertical stabiliser. (entire stabiliser is of composite structure)

The photo of inside : It seems it was taken inside the tail end and considering that light comes from the top of photo, I believe camera was held reasonably level. Therefore, this part of tail section probably rests leaning on vertical stabiliser with its right side on the bottom. Right half of horizontal stabiliser pushed into the mud or is (partially) broken away-fuselage rests half inverted to the right side-approx. 130 deg. from normal. Interior shows (deleted) parts of THS mechanism structure, that moves-trims horizontal stabiliser via jackscrew. (deleted). Am surprised that CVR / DFDR were not found, as they are installed very close to position, from where the photo was taken. I assume that part of the fuselage is not in the same piece with the structure photographed or is buried in mud.

Later comment: rewiving larger photos I had to edit (delete some parts) of my above post - what I thought was part of stabiliser and jackscrew, actually it is not-therefore nothing can be said about THS position (ANU/AND) and location from this photo, as it shows fuselage structure-frame with part of THS mechanism (drive motor, that is installed on top of structure and is partially visible on the photo and probably some part of THS in the background. Amount of light suggests that THS is not in reasonably one piece.
Am trying to add photos of that area, taken inside of an A-320.
Considering the damage and the fact that CVR DFDR are installed on a rack, fitted to the RH side of fuselage behind pressure bulkead, it seems that part is torn off, so black boxes are probably not attached to photographed structure.

Last edited by hoistop; 11th Jan 2015 at 11:15.
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