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Old May 18th 17, 01:47 AM posted to rec.aviation.soaring
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Default Power Flarm with ADS-B out?

On Friday, May 12, 2017 at 1:54:02 AM UTC-7, Darryl Ramm wrote:
On Thursday, May 11, 2017 at 9:06:59 PM UTC-7, wrote:
Where do you fly? The Minden/Reno area? Do you have a transponder today?


Thanks for the thoughtful response. Yes, certified. Yes, Minden. Yes , transponder.

Heavy tin is not the issue. The concern is the lighter GA tin that is not in contact with ATC.


First thanks for equipping with a transponder in the Reno area.

Sorry I should have also asked what transponder you have. If you have say a Trig TT-22 then the remaining cost is largely the suitable GPS receiver (e.g. the Trig TN70 for ~$2k plus install costs).

If you voluntarily install ADS-B out in your *certified* glider you are required to meet the performance requirements of the 2020 Mandate which in practice today means a TSO-C145c GPS like the TN70. And just do whatever the transponder manufacturer says and ideally follow an existing STC documentation as closely as possible.

But its not clear how useful this will actually be for different usage scenarios. There are just so many unknowns here. You might want to do some informal survey of what ADS-B Out and In capabilities local GA aircraft have and try to get a feel for local ADS-R and TIS-B coverage.

Are the GA aircraft equipped with ADS-B Out? (so they have a chance of being a ADS-R and TIS-B client) and are they equipped with ADS-B In and on what link layers? I assume in the high desert/mountainous areas of Nevada many will be equipping with ADS-B Out, and hopefully mostly on 1090ES Out... but it would be intersting to know.

And hopefully GA users have gotten the message and are only buying dual link receivers.

If you are within ADS-B and SSR coverage then other aircraft properly equipped with ADS-B Out *and* ADS-B In will see your transponder equipped glider via TIS-B. Not so useful for close-flying gliders but more useful for GA aircraft to see gliders with. Likely not useful say close to the pattern area at Minden airport because the Reno located SSR radar can't see low down the valley. (And TIS-B requires the ADS-B Out system in the client aircraft to be properly set up to transmit the correct capability codes that describe the aircraft's ADS-B In capabilities. So remind GA pilots using portable ADS-B In systems to check if their ADS-B Out system is properly configured to advertise their correct ADS-B In capability).

If within SSR coverage and the GA aircraft is communicating with ATC then that that helps avoid you with just a transponder.

If you have 1090ES Out and the GA aircraft has a 1090ES or dual-link ADS-B receiver they'll see you directly.

If you have 1090ES Out and the GA aircraft has a UAT receiver and no ADS-B Out then it won't reliably see you. It may see ADS-R messages about your aircraft transmitted for other client aircraft. A potentially confusing/dangerous situation.

If you have 1090ES Out and the GA aircraft has properly configured ADS-B Out (UAT or 1090ES) and UAT-In and is within ADS-B ground coverage then it will see your aircraft via ADS-R.

So maybe lots of things to look at with the GA pilots in the area. With all that complexity and costs and hassles (including installation costs and increased power-consumption) it may be that the marginal gain of installing ADS-B Out is not worth it. OTOH I would not be flying in that area at all without a transponder for the airlines and fast jets and general help it gives via ATC.

There may be some hope about STC based approval for non-TSO GPS sources for ADS-B Out install in certified aircraft, if that happened then maybe the GPS part of the cost of an install might go from the current ~$2k to say ~$500 or so. You'll still have some install costs and hassle of finding an A&P who know what they are doing to do this properly. So while it will be nicer for component costs to keep falling, I also kinda feel that if somebody *really* wants ADS-B Out in a glider today then they should probably not hold out hoping for further large decreases in cost. Just write that check and get going. And as more folks do that we should all get a better feel on real world usefulness. For non-certified gliders they can already use lower-cost GPS sources (like the Trig TN-72). This differential costs between installation in certified and non-certified gliders is just frustratingly stupid bureaucracy helping getting in the way of ADS-B adoption.


As of 1/31/17 there are only 33,099 aircraft equipped with ADS-B, and only 27,431 are good installs. Installs are happening at the rate of less than 1,500 per month. At this rate only about 46,000 aircraft will be equipped with ADS-B by the 1/1/2020 deadline. This means the vast majority of the general aviation fleet will not be equipped. If you are thinking about installing ADS-B to avoid mid-airs with GA aircraft you will be sadly disappointed.

Tom