I find that it does help with traffic awareness and the ability to locate traffic visually, although I don’t expect to see other GA aircraft visually until they are within 2 NM. I like the Garmin relative traffic trend presentation on my GTN750Xi and G500TXi as I find it very helpful to determine if the nearby traffic is a threat or going to possibly be in the future.
Legalese words that I think result from the delay (and associated position inaccuracy) associated with traffic data received from an ADS-B ground station, versus directly from the plane. Also because FAA doesn’t want IFR traffic darting all over the place without ATC direction or control, using ADS-B traffic data as justification.
Otherwise it’s fairly obvious that the use of ADS-B IN is quite useful ‘assistance’ to see-and-avoid, especially when you never actually see the other planes. In my VFR usage I’d estimate that as being over half the time but you can bet that I adjust my track to minimize conflict anyway, without any need for authorization if I’m not talking to ATC.
ADS-B In is not mandated in the US anywhere and is only approved as an aid for visual acquisition of traffic. This is from the AIM 4−5−7. Automatic Dependent Surveillance−Broadcast (ADS−B) Services:
e. ADS−B Limitations.
The ADS−B cockpit display of traffic is NOT intended to be used as a collision avoidance system and does not relieve the pilot’s responsibility to “see and avoid” other aircraft. (See Paragraph 5−5−8, See and Avoid). ADS−B must not be used for avoidance maneuvers during IMC or other times when there is no visual contact with the intruder aircraft. ADS−B is intended only to assist in visual acquisition of other aircraft. No avoidance maneuvers are provided or authorized, as a direct result of an ADS−B target being displayed in the cockpit.
Some recent US statistics as of 4-1-2023. GA aircraft 205,000 of all types. Equipped with compliant ADS-B Out systems: 163,000. About 3/4 are 1090ES and the rest are UAT. Of these, In the GA fixed wing fleet, about 110,000 aircraft are equipped, but a little over 5000 are NPE (Non Performing Emitter) which means they have issues and can’t be used. Portable ADS-B Out is virtually non existent and not allowed, so the NPE aircraft have either bad installations or inputs such as pressure altitude or GPS source is not compliant. I had a failure of a missing pressure altitude in my UAT ADS-B Out system making me NPE. TRACON (Approach and departure control) didn’t notice because they were getting the altitude from my mode S transponder, but ARTCC (Center) did notice the issue as they seemed to be using a Fused (all inputs from secondary radar, primary radar, ADS-B Out, multilateration). TRACON and ARTCC use different computer systems. My issue was resolved by changing the source for the pressure altitude to the UAT system.
With about a quarter of GA aircraft not being equipped and about 10% without a transponder with mode C, the ground station TIS-B product can fill in providing traffic information for most (60%) of the remaining targets in the enroute phase of flight, but not in the traffic pattern where many of the mid-air’s occur. TCAS or TAS can fill in for these in the traffic pattern and anywhere outside a TIS-B SV which requires being inside both a secondary radar SV as well as a ADS-B ground station SV. Also TCAS and TAS don’t require the target to have a working mode C, just mode A, to provide target information.
Not all certified traffic display systems provide target information on the ground, example a GNS430W/530W coupled with a GTX-345. The GTN 650/750 systems coupled with a GTX-345 or GDL88 will show ground traffic of ADS-B Out targets. Although portable systems will show anything they receive, including NPE targets. I am not a fan of portable systems for providing traffic information as they are not required to use the more sophisticated traffic alerting algorithms and often have antenna issues because of metal airframes and therefore can miss the one and only ground station assigned to generate their TIS-B. While FIS-B is highly redundant and missing one ground station will usually not impair receiving weather data, that is not the case with TIS-B.
Peter wrote:
The % of GA emitting SIL=3 is really small. It is basically higher end IFR types which have an ADS-B OUT capable Mode S transponder (in Europe it is not possible to emit certified ADS-B OUT without Mode S) fed from an SBAS (WAAS/EGNOS) GPS.
I’d say most mode S transponders are capable of ADS-B out. Even the most basic Trig TT21 can do that. It is more critical that you have an SBAS GPS source — and of course that everything is wired correctly. But that’s something you find not only in high end IFR aircraft.
Silvaire wrote:
The collisions can happen where inbound and outbound traffic to one or more of the airports is funneled in by terrain, putting a lot of planes in one place and making you track several at the same time, which is difficult.
This is definitely a category missing from LeSving’s list, and I would expand this to include areas where uncontrolled VFR traffic is compressed into a small space or corridor due to complex airspace (big terminal areas, restrictions, VFR corridors, etc). I fly in the region surrounding Amsterdam, and for a large chunk of airspace you have all the VFR traffic flying below 1500, which means everyone is basically at the same altitude. I had a very close call a couple years ago and just yesterday on a 45 min flight back from my shop I had to actively avoid 3 aircraft, one of which I did not see (and did not see me) until Dutch Mil alerted me. This is why I always ask for traffic service.
I think US ATC already do vectoring based on aircraft ADSB data
Possibly, but not SIL=0/1 which the portable boxes do.
The % of GA emitting SIL=3 is really small. It is basically higher end IFR types which have an ADS-B OUT capable Mode S transponder (in Europe it is not possible to emit certified ADS-B OUT without Mode S) fed from an SBAS (WAAS/EGNOS) GPS.
There is one reason why EU/UK never went for ModeC+ADSB instead of ModeS or zillions of toy likes of SkyEcho, FLARM, PAW…, this is because we can make our own solutions (problems), we can encourage our own innovation, we support local firms
That’s all true but also there is the ICAO certification framework which prevents “official” usage of the “velcro stuff”.
In the UK, due to the mad no-prisoners CAS policy, a lot of people are flying non-TXP but using the “velcro boxes” to get traffic warnings while not getting picked up by ATC radar. How effective this is I don’t know, but probably OK within the low flying (<2000ft) community within which most non-TXP stuff exists.
It would be an interesting project to merge SIL=3 (i.e. certified ADS-B) data (from a TAS605A) with SIL=0/1 (uncertified ADS-B) data (from some “velcro box”) and feed that to the panel display. Not possible legally but would be rather good 
It would show the “velcro box flyers” on your panel mount displays. Presently that traffic can be displayed only on a tablet, which is ok if you like that sort of thing, are happy with it shutting down in sunlight, etc. More context.
From here
ADS-B is more complicated; it isn’t doable with cheap aircraft boxes in the context of an ICAO compliant ATC service.
I think US ATC already do vectoring based on aircraft ADSB data (including data radiated from those uncertified IFR Lancairs with PT6 in front)
@NCYankee will know if they can use targets from ADS-B instead of those from ModeC?
I don’t think there is ModeS requirement for IFR in US: pilots operate using ModeC+ADSB and everything works beautifully
My understanding TXP is only required near Bravo or above 10kft, I wonder even if one can fly IFR in say Echo with ADSB alone? the answer from FAR is not obvious and likely at ATC descretion
There is one reason why EU/UK never went for ModeC+ADSB instead of ModeS or zillions of toy likes of SkyEcho, FLARM, PAW…, this is because we can make our own solutions (problems), we can encourage our own innovation, we support local firms…so, we don’t have to use US standard for ADSB, however, this will still come with time as frankly it’s the only reliable & economic solution out there…
Traffic avoidance system is helpful when descending on an instrument approach to an unmanned uncontrolled airport in G airspace. There often can be a few VFR aircraft below the cloud layer around the airport with vague position reports (“west of airport, 5 minutes to pattern” or “over lake Puddly”) which make it hard to understand if these aircraft pose a potential threat to your approach. With TAS system you get a fairly good traffic awareness and usually immediately identify the aircrafts on the frequency on your TAS screen.
I understand that TAS does not completely eliminate risk of collisions in G airspace but I believe it significantly reduces the risk. It is still legal to fly in G airspace without radio / transponder, so in any case there can always be aircrafts around which don’t give position reports by radio or show in TAS system.
I have active traffic from KTA 870 and ADS-B traffic from GTX 345. I would also like to have FLARM traffic as we have a lot of gliders when weather is favourable (also IFR gliders).
My TAS605 works great in the circuit. I used to think it would be like an xmas tree and sometimes it is but it is always useful and I would never decide to ignore what it is telling me.
I am still waiting to swap it for a TAS605A (ADS-B IN) but need to get an exchange box.
