Originally Posted by
9Aplus
On the other hand that area is have fair coverage with F- kind of FR24 hardware where GPS is ON 7/24/365 and position can not be "written by
hand" and time domain timing is not estimated through network but sourced from GPS timing.
Which is slight difference to T- kind of devices mostly self home-made out of good SDRdongle, RPI2or3, fair 1 GHz range antenna, good net, with or without GPS present.
Let's see official report but expect no surprise, the plank was above
and behind on 7 to 8 diving on poor souls in G2
Edit / this post just confirm that the data for FR24 was enough to have fair estimation of position:
Yes, "F" type receivers are much better than the "T" type SDR devices. Unfortunately FR24 doesn't make it publically available (to the best of my knowledge) what type of receivers and how many receivers are tracking a flight. I would be the first to credit the accuracy of FR24 for correctly equipped aircraft at high level, however the same can not be said for MLAT at low level; especially for suddenly changing data.
Since we've pretty much decided that there is no need for the AAIB based on the FR24 data perhaps you have some thoughts on these questions:
1. Why the sudden dog-leg on the last data received from the aircraft as plotted on the FR24 map? The reported track was 17 degrees which is consistent with the previously received data. Note: If you plot the co-ordinates yourself this will correlate with the map, not with FR24's csv/xml data.
2. The aircraft tracks crossed somewhere between 11:58:28 and 11:59:01 according to the FR24 data. At this time FR24 reports the aircraft was not "diving" and was infact holding an altitude of 3500-3700 feet. The helicopter was consistently between 1,025 and 1,050 feet. Any thoughts on this? Based on the FR24 data they had ~2,500 feet of vertical seperation.
3. Last received data from the helicopter was at 12:00:46 (1000 feet consistent speed and heading with previous data). Last received data from the aircraft was at 11:59:44 (2700 feet (a loss of 700 feet in 24 seconds), with speed and direction remaining consistent with previous data. Generally speaking data from the heli was received every ~10 seconds. Data from the plane was received slightly less often but not by a large amount. Why was data received from the helicopter for another minute than the plane? I can only think of one reason - and if that was the case it msot likely wouldn't be reporting a steady alititude of ~1,000 feet.
4. Do you know what filtering FR24 does on received data in order to provide the end users with positon, heading, speed and alititude data? I would imagine it's fairly accurate when data is relatively consistent but I guess all bets are out the window when incidents like this occur.
5. If reception in this area is so great why is the first received data from the aircraft received at 11:57:27 when it is already at 2,800 feet? I suppose it is possible the pilot didn't have the transponder on until that point but it seems a bit odd to me, especially for a training flight.
Maybe this gives some indication of why I created my original post rather than people throwing around theories such as xxx FPM descent rate, cessna "diving" towards the heli etc etc.
At the end of the day whatever happened 4 people have died. Perhaps its not the circumstances to be drawing conclusions based on limited publically available data.