ADS-B to FR24
 

My ADS-B receiver was provided by FR24 and it has both an ADS-B antenna and a separate apparently amplified GPS antenna. My assumption is that the reports that go out are time stamped with time of reception using very accurate time from GPS. I'm located in a very desolate area in Nevada near Death Valley and get quite a few lower level flights that are missed by some FAA resources. And often see aircraft ADS-B signals about 30 miles out over the Pacific near San Francisco and well into Utah.

Heard from a mate who flew in there today that the aircraft had had maintenance all night by local engineers and was signed off early this morning.

One can only speculate but I very much doubt it was shot down.

Debris field
 

BBC reporting debris field spread over 8 Km.

FR24 Data analysis
 

Took the CSV file FR24 published on their site and graphed the altitude as reported by the stations.

The results are below: KGL9268 Altitude data - Album on Imgur

Whatever happened started some 255 seconds from the start of the published log, upto that point the aircraft was climbing normally and all stations were reporting consistent data. After that it gets fuzzy. The album also contains 4 more images - one is all altitude data after the 250. second and the rest is altitude data after the 250. second separated by station ID.

No interpretation from my side, thought it might come handy to someone.

8 km debris field indicates medium to high altitude break-up, so missile strike cannot be ruled out.

OEB 48
 

Hello Chaps,

Over the years Airbus have generally suffered from AoA probe issues. Some more significant than other depending whether it's an SA or LR type.

Perhaps a culprit could be the onset of an incorrect applied procedure for Abnormal v Alpha Prot which led to an UAS, loss of a significant amount of speed whilst misunderstanding OEB48.

An aircraft in alternate law at high altitude isn't as easy to handle as an aircraft at lower altitude.

Food for thought, it's hardly trained and a bit of tough one to simulate. A lot of us have a tendency 'to read the OEB'. But do we understand it?

Integration
 

Without doing all the math, it seems to me that this altitude profile is not necessarily in conflict with the Vertical Speed graphic posted this morning on ASN.

MH17 report had the following to say about the Sinai peninsula:

http://40.media.tumblr.com/aac5293d9...cbco1_1280.jpg

I was thinking somewhat along the same lines regarding the different stations, but what I did was make a new CSV with the data sorted not by time (which we know is not reliable, as the timestamp is not from the aircraft) but by coordinates (which are transmitted by the aircraft) from 30N onwards. Share CSV files online - ShareCSV

For easier visual comparison (to me anyway), I also made a CSV with the same data, only staggered by station, with those lines of data that appear to be duplicates from more than one station overlapping. Share CSV files online - ShareCSV

No deep analysis from me here, but a couple of remarks:
(1) It appears the time difference between receivers is quite small.
(2) There are overlapping packets in the final stage, which to me means that as weird as the numbers look, they are what the aircraft reported, and not receiver errors.
(3) In my experience, the personal/hobbyist ADS-B software will silently carry over data from a previous packet. I often see too few parameters change when I observe an aircraft at the limit of my range.

Notes from the Russian Press: Hammer Already Falling
 

Just looked at the longest article I've yet seen (on any topic) in gazeta.ru: The Largest Catastrophe in Russian Aviation

Some highlights:

• this crash is the largest loss of life in the history of Russian aviation, surpassing the 1985 Tu-154 crash in Uzbekistan which killed 200 (that doomed Soviet era-flight was also intended to land at Pulkovo airport)

• Putin has declared tomorrow (1 November) to be a national day of mourning

• although the flight was nominally chartered by a tour company called "Triomed" operating under the brand "Brisco", both Triomed and Kogalymavia (operating under the brand Metrojet) belong to "Western Aviation-Investment Company" ... ALL of these companies are registered at the same Moscow address

• the Investigative Committee of the Russian Federation has already opened two criminal cases :eek: ... one for "violation of the rules of safety preparedness" («Нарушение правил полетов и подготовки к ним») and another for "provision of unsafe services" («Оказание небезопасных услуг»). Quick work, comrades!

• the Russian web has numerous complaints from previous airline customers complaining about their experiences

• on 1 January 2011, the airline experienced a fire on a taxiway in Surgut which killed 3, and sent 43 more to hospital

• customers with Brisko tour reservations are cancelling their trips

• notwithstanding all the above, Brisko announced that it will loyally continue to charter its flights with its kissing-cousin airline, Metrojet

• the airline apparently insures it passengers, with the payout expected at more than RUB 2,000,000 (over USD 31,000 at today's rates) per person

• Putin has declared tomorrow (1 November) to be a national day of mourning
________________________________

A "non-news" component of the story that got my attention, was (in the context of reassuring readers about the aviation system) a wry acknowledgement of Russia's corner-cutting traditions. It explained that aircraft maintenance is unlike "известного в России способа «быстро сделать»" (the known Russian method of "making quick").

This reference acknowledges the awareness of ordinary Russians that in their "rules are made to be broken" culture, few things are what they're supposed to be. It is normal for Russians to be afraid that restaurant food may send them to a sickbed, or that liquor purchased from a shop will be a cheap counterfeit of its labelled brand. (Not selling "anti-Russian propaganda" here, this is first-hand experience from many visits to the Russian Federation.)

"data sorted not by time (which we know is not reliable, as the timestamp is not from the aircraft)"

It is reported that the stations use GPS to time stamp their data. That means the time stamps should be quite accurate - well under a microsecond error.

Aircraft reported position during an extreme event, on the other hand, could be off, as could altitude and speed. These measurements may be way wrong. Someone here probably knows where the position comes from - is it from an integrating flight computer or from near-instantaneous GPS, for example.

Hopefully the black boxes will lead to a decent reconstruction. Then, it would be quite interesting to see how the FR24 recorded ADSB data looks.

Wrong. S-mode packets are time-stamped on the receiver before they are uploaded to the server.

Partially wrong. Some receivers are GPS time synced and some are not. See RYFQB's explanation.

Added altitude and GS
 

Created a new album with altitude and GS both in the same graphs.

KGL9268 - Altitude and GS - Album on Imgur

The data does seem to be rather consistent, since there are no outliers before the 250th second.

What is interesting is that GS drops to below 100kts on both stations 2132 and 2593 (2614 stops receiving after second 261) drop along with the altitude

D.

Edit 2: You are flat out right. My line of reasoning was ill-founded, as I mixed up the types of receivers.

2614
 

damirc:

Interesting graphics. 2614 looks like an outlier. It will be interesting to learn the true story, but if the rest of the data is remotely correct, I think something catastrophic happened long before impact with the ground.

We can simply plot all the stations together to quickly see how their data relate:

https://s3.amazonaws.com/org.barkah....ebystation.png

A few points to help with interpretation.

* We don't have enough data. The aircraft normally transmits information twice a second. But even the station with most records (2593) only has 8 data points between 04:13:00 and 04:13:21. Clearly, many packets were lost.

* Velocity and heading are transmitted in one packet. Latitude, longitude and altitude are transmitted in a different packet. Which means that, e.g., if a station gets a position packet but not a velocity packet, you'll see a row with current altitude but outdated velocity, and vice versa.

* There's no timestamp in the packet so entries with slightly different times received by different stations may correspond to the same packet.

* Vertical velocity seems to be extremely noisy and seems to be derived from altitude anyway, so I'd disregard it altogether.

I tried to parse the data provided by FR24 with all this in mind, and here's the picture I'm getting.

* Prior to 04:12:58, all is normal.
* Around 04:13:00, there's a couple of erratic altitude readings. (There are three packets within three seconds reporting altitude 29750, 30975 and 33275, and clearly all of them can't be right. The aircraft was at 30750 just prior to this time.) The aircraft begins slowing and turning to the right.
* At some point between 04:12:58 and 04:13:05 (the exact time is hard to pinpoint because of the erratic readings), it begins descending.
* At 04:13:10, it's slowed down below 250 knots, turned 25 degrees to the right, and it's descending at the rate of at least 7000 fpm.
* Last received position packet, at 04:13:19.5, gives its altitude as 27925'.
* Last received velocity packet, at 04:13:22, gives its horizontal airspeed as 62 knots.

So that would be a receiver near Amman from the airport code. That site is active almost 24 hours later, at the moment tracking an Egyptair A330 approaching the Gulf of Aqaba.

Wonder if some more useful data could be harvested off F-OJAI2's computer? FR24 would know the contact information.

By the way, can anyone find locations of those stations?

A check of FR24 map shows several airports within range from the crash site. Sharm El Sheikh is pretty far. Eilat is only 100 km away, but there's a line of hills west of the city which may be blocking the line of sight. But two airports in Tel Aviv are 200 km away, and, if they were already tracking it, they should have been able to see it at least down to 15000' if it were transmitting all the way down.

As others have done, I broke the FR24 data into 3 sets by receiving site, and compared data.
The aircraft data transmissions do not so much resemble discrete pulses of data that are either received or not received by a station, but are more like a steady stream of data packets that are either received or not received. by the individual stations. (This means that you cannot easily cross check stations for synchronicity.)
I did compare unique events reported by the 3 reporting stations and they seem to be within 1 second of each other. The uncertainty revolves upon how time data is rounded. In a few cases, an individual station reported two separate sets of data for the same second.

After examining the data for the first deviation from "Ops Normal" I picked the time 04:12:35Z as the demarcation between Ops Normal and what followed. At that point, the rate of climb began to deviate from expected and afterwards, around 04:12:57, the aircraft experienced some sort of full scale break up event that caused its Ground Speed to decrease rapidly.

The times referenced are the FR24 provided times.