On Thursday, February 11, 2016 at 7:55:21 AM UTC-8, Dan Marotta wrote:
On 2/10/2016 9:53 PM, Darryl Ramm
wrote:



So hands up who would want a box that can display ADS-B traffic on your current soaring flight computer but will/can not issue any warning at all as you collide with a threat?



I do, I do...!



Seems to me that simply having a picture of the traffic around you
is sufficient without all the whistles and bells yelling about an
imminent collision.* There's another aircraft 5 miles away!* Ho
hum...* Let's see where he is on the next (or one after) update.*
Same relative clock position (azimuth and elevation) only closer?*
Maybe a threat, I'll monitor or deviate a little.* Yes, in a busy
airline cockpit, I can see the need for collision warnings but,
we're flying VFR and are supposed to be looking outside.* Knowing
there's an aircraft at a particular location and closing is all I
need or want.



I'm not talking about gaggles or energy lines here.* You have Flarm
or PCAS for those situations.



What I'd really like to know is why the FAA doesn't want to transmit
all aircraft positions in the blind.* What is to be gained by
denying me information about local (to me) traffic just because I
don't have a particular box in the aircraft?* Is it a bandwidth
thing?

There are likely bandwidth concerns in some situations. Which is why its important to wait and see exactly what proposal the FAA comes up with. The whole dual-link/claimed need for UAT to free more bandwidth on 1090 MHz has not worked out as the FAA had hoped. And blind transmitting TIS-B would effectively be going to use all that complex FAA ground system that was supposed to help reduce 1090 MHz congestion to actually increase 1090 MHz congestion, oh the irony. I was never strongly convinced by some of the 1090ES bandwidth arguments, there did not seem to be much competitive academic research on this and the European's for example took a different approach that relied on decommissioning Mode C transponders (their interrogation by TCAS especially in crowded airspace wastes lots of 1090MHz bandwidth), change 7.1 to TCAS, and over time maybe other tweaks and improvements to TCAS and SSR systems to reduce transponder interrogation rates and allow more bandwidth at 1090MHz for ADS-B.

But there are likely other reasons than just bandwidth, the FAA also has had some pretty weird approaches to what will "encourage" ADS-B Out adoption. And now everything is such a complex mess that there likely is not a single simple answer to your question. And to some extent as we get closer to 2020 and ADS-B carriage will be mandated in many aircraft TIS-B becomes less interesting (and ADS-B direct and ADS-R (to a much smaller extent because many folks seem to be going 1090ES Out than UAT Out and others dual-link ADS-B In) become more important. And right now where this whole system is at it is important that airspace users in general are encouraged to install ADS-B Out. The primary leading factor is likely to be cost, and while the FAA has not always done things to encourage reduced cost things are finally starting to move better there with mainstream manufactures producing more affordable ADS-B Out systems and hopefully TABS regulations and future availability of TABS devices will help reduce ADS-B Out equipage costs for gliders, that might come with the arguable downside of mandatory TABS/ADS-B Out carriage for gliders. All a part of why waiting and seeing what happens with TABS affects so much here.

The looming 2020 ADS-B carriage mandates (that gliders are currently exempt from) and possible (likely?) changes coming with TABS are all reasons why I'm just not that interested in TIS-B and PowerFLARM integration. But the time anything is here and actually working well enough it will be increasingly irrelevant (as most transponder equipped aircraft equip with ADS-B Out). Dual-link ADS-B receive in a PowerFLARM type systems for non-TIS-B use is probably more interesting longer term, maybe as well for FIS-B/weather and TFR data etc. but who will do all that integration work, and why it would be economically justified for a small USA market is unclear.



--

Dan, 5J