On Friday, May 8, 2015 at 1:19:30 AM UTC-4, Andy Blackburn wrote:
On Wednesday, May 6, 2015 at 11:08:27 PM UTC-7, Mike Schumann wrote:

The question is, do you want to end up with an avionics package that doesn't see UAT ADS-B OUT equipped traffic? It's hard to predict how much of the GA or UAV fleet will go down that road, but it could be a pretty significant percentage if there is a significant price difference between UAT and 1090ES ADS-B OUT solutions.

That's not really the right question. The question is how do you trade off total cost versus the probability of potential collision scenarios.

If you can only afford a single device for most glider pilots the right choice is a PowerFlarm, which will get you anticollision for other PF-equipped gliders, plus PCAS for all transponder-equipped aircraft being painted by SSR or TCAS, plus 1090ES In for most (and in 2020 ALL) aircraft that fly in Class A.

Under some less common circumstances your best choice if you can afford only once device is to buy a transponder (preferably Mode S). This will make you visible to most high-performance aircraft equipped with TCAS AND to SSR AND to GA with PCAS. Modern Mode S transponders also have an upgrade path to 1090ES Out which will make you visible to most ADS-B equipped aircraft either directly or via ADS-R. Keep in mind that it is generally better for the higher performance aircraft to detect the lower performance aircraft rather than the other way around as they have more degrees of freedom.

If you can afford two devices you are best off installing a PowerFlarm AND a transponder. This will allow you to see and/or be seen by all transponder, PowerFlarm and 1090ES Out aircraft and will allow you to upgrade to 1090ES Out which will also make you visible to aircraft carrying UAT In/Out but aren't carrying a transponder or talking to ATC - not sure how many of these there will be given the regulations overlap between ADS-B and transponders.

If you want to install three devices you can consider UAT-In - this will additionally give you coverage of aircraft that are not carrying a transponder but are carrying UAT Out. It will also allow you better granularity in seeing UAT-Out aircraft and any UAVs that are flying outside MOAs or wander above the 400' FAA limit ASSUMING they are equipped with UAT instead of 1090ES - not clear that UAVs are going to be a big deal or that UAT would be preferred to 1090ES for them. Based on the statistics, this does not seem like a good return on investment in terms of risk reduction. I am personally skeptical that many GA aircraft will equip with UAT Out over 1090ES Out and am particularly skeptical that they will eschew transponder carriage so you wouldn't see them on PowerFlarm's PCAS.

The idea of picking UAT In before PowerFlarm and/or a Mode S transponder defies all the traffic, equipment and collision statistics. If you want it as a third device knock yourself out, but it is definitely well past the point of diminishing returns.

9B

Everyone is going to have somewhat different priorities depending on what kind of flying they do. Competition pilots are obviously going to be focused on FLARM due to their close proximity to other gliders many of whom are presumably also going to be FLARM equipped.

Those of us who fly recreationally near major metropolitan areas in the midwest have a different threat scenario. Most of the time, the big iron is not a factor, as they are flying higher than we can reach in a thermal. We will encounter sporadic regional or private jet traffic. What is a big factor, particularly when you are close to an airport is other GA traffic. In this environment a fully functional ADS-B IN system (coupled with ADS-B OUT) is very helpful in giving you the big picture of exactly where everyone else is. Virtually all of the ADS-B IN systems sold in the US (except PowerFLARM) support TIS-B and will show you exactly where all transponder equipped aircraft are if you are within range of an ADS-B ground station and you are ADS-B OUT equipped.

Your assumptions about the limited threats posed by UAV traffic may be accurate today, but wildly off the mark in the not too distant future. Once the FAA gets their act together, we are going to see an explosion of UAV applications for pipeline monitoring, agricultural spraying, aerial photography, news gathering, law enforcement, etc.... The economics of this technology is compelling. Many of these applications are going to be in rural areas where you would least expect to encounter another aircraft. All of these UAVs are going to be ADS-B equipped. Whether it will be UAT or 1090ES is anyone's guess at this point. My personal feeling is that there will be a lot of UAT ADS-B OUT equipage, unless there is a dramatic reduction in the price difference between these technologies.

The final question that everyone has to face is the when to equip. This is a very rapidly evolving field with significant price reductions and capability advances happening in a relatively short time horizon. Everyone is going to have to make their own decision on when to pull the trigger, given their willingness to risk technological obsolescence if they buy the wrong product too early.