Radars, business jets and "Unknown" MLAT aircrafts

[Hoggorm]

1 - When clicking on an aircraft on the FR24 website, what determines what "radar" is displayed in the lower left corner of the aircraft information? Often I see "radar 2" when I know "radar 1" is closer. Is this just selected by random?

2 - Why do business jets only show aircraft type and not callsign, when the aircraft callsign is transmitted? I have an ADS-B receiver myself where I can see what aircraft callsign is received by my receiver. I cannot display the aircraft on my own map, since it only has a Mode S transponder; however the callsign is basically always known. On FR24 however the aircraft only shows up with aircraft type.

3 - Why do some MLAT aircrafts show up with "Unknown", "No callsign" or just the transponder HEX code(?) and not callsign. This appears to happen mostly when in poor coverage. Still, since FR24 needs 4 receivers to plot a MLAT aircraft at least one of them should be able to know and display the callsign? Again as mentioned above the callsign is known by my simple ADS-B receiver when it receives a transponder signal.

[Oblivian]

1 - When clicking on an aircraft on the FR24 website, what determines what "radar" is displayed in the lower left corner of the aircraft information? Often I see "radar 2" when I know "radar 1" is closer. Is this just selected by random?

Newest positional data received and decoded by server

2 - Why do business jets only show aircraft type and not callsign, when the aircraft callsign is transmitted? I have an ADS-B receiver myself where I can see what aircraft callsign is received by my receiver. I cannot display the aircraft on my own map, since it only has a Mode S transponder; however the callsign is basically always known. On FR24 however the aircraft only shows up with aircraft type.

Your PC does not show information that is openly public and accessible on the internet by thousands of visitors a day. Whereas FR24 is, and as such needs to follow requests from government agencies and organisations to not display some private information so freely so as not to have take down notices set upon them[/quote]

3 - Why do some MLAT aircrafts show up with "Unknown", "No callsign" or just the transponder HEX code(?) and not callsign. This appears to happen mostly when in poor coverage. Still, since FR24 needs 4 receivers to plot a MLAT aircraft at least one of them should be able to know and display the callsign? Again as mentioned above the callsign is known by my simple ADS-B receiver when it receives a transponder signal.

[/quote]

As you so point out, ADS-B contains the callsign. A lot of lower version Mode-S aircraft which are usually located by MLAT do not. So unless the callsign is known from another source such as FAA data before MLAT takes over, it cannot be shown.

[Hoggorm]

Your PC does not show information that is openly public and accessible on the internet by thousands of visitors a day. Whereas FR24 is, and as such needs to follow requests from government agencies and organisations to not display some private information so freely so as not to have take down notices set upon them

I'm talking about aircrafts from Business Jet companies like Netjets, Sundt Air, etc. They act basically as regular airlines. I cannot imagine such companies have requested not to display such information? Why them and not British Airways, Lufthansa, KLM, SAS etc? Government aircraft, military and so on, yes, but not business jet companies.

As you so point out, ADS-B contains the callsign. A lot of lower version Mode-S aircraft which are usually located by MLAT do not. So unless the callsign is known from another source such as FAA data before MLAT takes over, it cannot be shown.

Still, the exact same aircraft appears with callsign when in what appears to be better MLAT cover. The examples I refer to I've only seen in Europe and FAA has no flight information here.

[Mike]

1- Please follow the links in first post: http://forum.flightradar24.com/threa...oftware-thread!)

2- Please read http://www.flightradar24.com/how-it-works Has also been discussed here: http://forum.flightradar24.com/threa...locked-flights and here: http://forum.flightradar24.com/threa...o-registration

3- Some aircraft/transponders are not transmitting callsign. Not 100% sure about reason but my guess that it's a combination of old transponder and ATC infrastructure. With some older transponders ATC needs to query the transponder about callsign, and this is not done in some areas, as ATC is using squawk and not callsign to identify the aircraft.