On Sunday, October 1, 2017 at 4:09:40 PM UTC-7, wrote:
On Saturday, September 30, 2017 at 5:39:42 PM UTC-4, Darryl Ramm wrote:
I don't understand why you think existing PowerFLARM devices are related to UAT. The only ADS-B thing a PowerFLARM can do is receive 190ES In, and only that direct from the 1090ES Out aircraft. They come out of Europe were there is no UAT and are completely incompatible with UAT. If UAT never existed PowerFLARM would be *more* useful in the USA because you would see all ADS-B Out traffic. PowerFLARM does not transmit on UAT, can't see UAT, and can't receive ADS-R relay of UAT traffic (even if you have a suitable ADS-B Out system to cause your glider to become an ADS-R client).

- thanks Darryl. So I had the ADS-B frequency that PowerFLARM uses backwards. So is ADS-R one-way only, relaying 1090ES traffic to UAT and not the other way around? Doesn't that limit the usefulness of UAT for GA aircraft, if it does not make them directly visible to the heavies? Or is there some other reason why PF won't receive ADS-R? (This over-complicated system makes my head hurt.)

It might help to remember PowerFLARM does 1090ES In (ie. the 1090 MHz transponder reply frequency) because PowerFLARM also uses that same 1090 MHz receiver to provide PCAS detection. (UAT operates on 978 MHz).

ADS-R goes both ways. The ADS-B Out system in an aircraft has "CC" capability code flags that describe if the Aircraft has ADS-B In on UAT or 1090ES (and obviously if neither flag set then no ADS-B In). The FAA ADS-B Ground systems looks at that "client" aircraft and "target" aircraft nearby it (within 15 naut. mile radius +/- 3,500' "hockey puck") and transmits data from the ADS-B link layer it knows the client can't receive to the one it can. If the client has no or both link layers (as many the systems do now) it won't be an ADS-R client at all. A properly configured dual link layer receiver aircraft may still be a TIS-B client (if the target does not have ADS-B Out at all).

ADS-B In systems may not operate fully/as expected unless the ADS-B Out transmitter for that aircraft has the CC flags set correctly. This incorrect setup is especially likely with portable ADS-B In system. Luckily most portable and fixed (GA focused) ADS-B receivers are now dual-link which makes this less of an issue... but you might still not receive TIS-B. Make sure you understand how your setup in your specific aircraft will work.

The actual retransmission data message via ADS-R, is very slightly different than the message it is retransmitting... the FAA system could not work it it was exactly the same. PowerFLARM coming out of Europe was apparently never developed to handle those slightly different USA focused ADS-R messages..

Remember outside of gliders all UAT Out equipped aircraft that are expected to get near an airliner are also going to have a transponder. That transponder is going to always be seen by the airliners TCAS II system. The ultimate magic of a TCAS II RA (resolution advisory) where TCAS directs the pilot (and the pilot must follow) what to do, only ever happens via transponder interrogation. A TCAS II system will fly into a UAT only equipped target with no RA. Airliners may also have 1090ES In and Out and will be ADS-R clients, that can be used to paint traffic on displays etc. It does not drive a TCAS RA. The needs for transponders in areas of busy airliner and fast jet traffic for TCAS compatibility is a very important issue. That ASG29 vs. Hawker 800 middair... yep the Hawker 800 had full TCAS II, glider had its transponder (recently installed but not yet tested/signed off) turned off.....