ADS-B “IN” at Ballina?

[Awol57]

Ground radar is a combination of ADSB and primary, so tower controllers can see both (usually). I understand that the TCU's are generally primary and secondary only, but I could well be wrong about that.

[Squawk7700]

I had a controller say recently “I can’t see you on ADSB because I can see you on mode C” which I found interesting.

Would be good to hear from an ATC’er as to what actually appears on the screen.

[faction]

Originally Posted by Dick Smith

I understand the RFDS has ADSB out but not in.

The RFDS PC24s have ADSB in.

[MechEngr]

Originally Posted by Lead Balloon

I built one of the Stratux ones. Amazing thing is how many (even high level RPT aircraft) you can spot visually, with the aid of the output of the unit displayed on the EFB screen. None of those high level aircraft is a collision risk - very ‘high’ while us nobodies are very ‘low’ - but it does demonstrate that the unit picks up and provides pretty accurate information about aircraft putting out Mode C data.

But the ‘blindspot’ is that it requires ‘something’ to be interrogating the other aircraft’s transponder….

ADS-B Out position messages are/ought to be transmitted once-per second, no interrogation required. I don't know about message collision avoidance in ADS-B, but I am aware that potential saturation of the time available for messages is supposed to be the reason that it was specifically banned for use from unmanned aircraft, aka drones/remote control aircraft. What happens with other radar/communication systems that also integrate ADS-B data is something else, but all on it's own there is no interrogation required.

This may be better explanation: https://www.icao.int/meetings/amc/ma...sitf4/sp01.pdf

[Lead Balloon]

Thanks ME. If ADS-B out equipped aircraft are ‘automatically’ transmitting position/alt through their Mode C transponder every second or so, I stand corrected in relation to those aircraft. Doesn’t seem to help with aircraft wth Mode C transponders but not ADS-B out, though. Presumably they have to be interrogated by ‘something’, first?

[le Pingouin]

Originally Posted by Squawk7700

I had a controller say recently “I can’t see you on ADSB because I can see you on mode C” which I found interesting.

Would be good to hear from an ATC’er as to what actually appears on the screen.

When we're receiving both SSR and ADS-B returns we see an SSR symbol on the screen (a circle) plus we get a small letter "b" appended to one line of label data indicating ADS-B is also being received, so we know we can continue using surveillance standards when the aircraft enters ADS-B only coverage. If only SSR is being received (either no ADS-B coverage or aircraft not ADS-B equipped) we don't get the "b". For TCU the "b" isn't displayed at all.

In ADS-B only coverage we see a four bladed "propeller" symbol and the "b" disappears. For TCU they still see a circle symbol regardless of whether it's SSR or ADS-B.

We can toggle the display to show what you're squawking but SSR takes priority if both are being received, i.e. we can't see your ADS-B code while you're in SSR coverage.

[Squawk7700]

Thanks LP, most helpful.

One more thing :-) are there changes in colour on the screen icons if the GPS is certified to TSO199 versus 146 / approved but not certified?

[le Pingouin]

No change in colour but I think it will only display a symbol for registered hex codes.

[malroy]

Originally Posted by le Pingouin

For TCU the "b" isn't displayed at all.

In ADS-B only coverage we see a four bladed "propeller" symbol and the "b" disappears. For TCU they still see a circle symbol regardless of whether it's SSR or ADS-B.

Most TCU do not receive adsb. They need an extra processor to convert the adsb returns into a fake radar return. This is available in sydney, melbourne and hobart.