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ADSB visibility with non certified GPS



 
 
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  #1  
Old September 21st 17, 07:27 PM posted to rec.aviation.soaring
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Default ADSB visibility with non certified GPS

The following quote comes from the Trig web page for their TN72 GPS.

"Wherever ADS-B technology is used it is worth highlighting that most ADS-B In traffic receivers will only display aircraft traffic that generate a non-zero quality indicator, (also referred to as SIL 1). In contrast a zero quality indicator (referred to as SIL 0) ADS-B Out, is ignored and not displayed on a traffic display – rendering an aircraft invisible."


Does anyone have any first hand experience/information on how common it is for those with ADSB out that report a zero "quality" indicator to be ignored? Is every ATC or airliner actively excluding these targets?


Separately, it's interesting to learn that while the TN72 can provide the higher "quality" GPS information, it appears that some (most?) ADSB-Out Mode S transponders don't have the ability report that they are getting "quality" GPS info. In this case, the TN72 (or equivalent) is a moot point and one would be just as visible (or invisible) with GPS from a Flarm or other generic GPS unit.

So, it would be interesting to know just how prevalent it is that non "quality" units are being ignored.
  #2  
Old September 21st 17, 10:34 PM posted to rec.aviation.soaring
WaltWX[_2_]
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Default ADSB visibility with non certified GPS

You make a very good observation...

So, what's the point of using a TABS TN72 with a Trig system if no one can see it?

Daryl... do you have any insights on this?


  #3  
Old September 21st 17, 11:33 PM posted to rec.aviation.soaring
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Default ADSB visibility with non certified GPS

Clarification...

Trig TN72 with Trig TT22 WILL be seen as having a non-zero quality indicator. (good)

Trig TN72 with Brand X Mode S/ADSB out, almost certainly has a zero quality indicator (not good).



On Thursday, September 21, 2017 at 4:34:34 PM UTC-5, WaltWX wrote:
You make a very good observation...

So, what's the point of using a TABS TN72 with a Trig system if no one can see it?

Daryl... do you have any insights on this?


  #4  
Old September 22nd 17, 12:23 AM posted to rec.aviation.soaring
Andrzej Kobus
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Default ADSB visibility with non certified GPS

On Thursday, September 21, 2017 at 6:34:01 PM UTC-4, wrote:
Clarification...

Trig TN72 with Trig TT22 WILL be seen as having a non-zero quality indicator. (good)

Trig TN72 with Brand X Mode S/ADSB out, almost certainly has a zero quality indicator (not good).



On Thursday, September 21, 2017 at 4:34:34 PM UTC-5, WaltWX wrote:
You make a very good observation...

So, what's the point of using a TABS TN72 with a Trig system if no one can see it?

Daryl... do you have any insights on this?


This has been discussed here many times over. The GPS source alone is not approved. It is the combination of the GPS and the mode S transponder that is approved. Please read up on the FAA website first about approved combinations, then search through this forum for additional information.
  #5  
Old September 22nd 17, 02:20 AM posted to rec.aviation.soaring
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Default ADSB visibility with non certified GPS

What hasn't been discussed is how often non-approved ADSB out sources are actually being ignored.
  #6  
Old September 22nd 17, 02:28 AM posted to rec.aviation.soaring
Darryl Ramm
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Default ADSB visibility with non certified GPS

On Thursday, September 21, 2017 at 4:23:14 PM UTC-7, Andrzej Kobus wrote:
On Thursday, September 21, 2017 at 6:34:01 PM UTC-4, wrote:
Clarification...

Trig TN72 with Trig TT22 WILL be seen as having a non-zero quality indicator. (good)

Trig TN72 with Brand X Mode S/ADSB out, almost certainly has a zero quality indicator (not good).



On Thursday, September 21, 2017 at 4:34:34 PM UTC-5, WaltWX wrote:
You make a very good observation...

So, what's the point of using a TABS TN72 with a Trig system if no one can see it?

Daryl... do you have any insights on this?



Yes discussed many times over. But aw heck lets go over that and some other stuff again. Well because this stuff is better than dietary fiber...

This has been discussed here many times over. The GPS source alone is not approved. It is the combination of the GPS and the mode S transponder that is approved. Please read up on the FAA website first about approved combinations, then search through this forum for additional information.


Well the GPS sources are approved in they may meet say meet TSO-C145 or TSO-C199 or "meets requirements of TSO-C145", or maybe meet none of those of a COTS GPS etc. and that stuff is important to understand.

Trig is correct in what they say. Certified ADS-B In receivers and the ADS-B ground infrastructure will ignore all ADS-B out systems using COTS GPS. Airliners, fast jets, etc. not receiving any of that crap. (that does not stop TCAS seeing the aircraft via transponder interrogation).

The Trig TT22 with 1090ES Out driven by a TN72 GPS source, all properly installed, will be seen by all aircraft with 1090ES In, both portable and certified/fixed install systems. It will also be seen by all aircraft with UAT In if within ADS-R service coverage. However you can only install a TN72 in an experimental aircraft. Certified aircraft, including gliders, requires you use a TN70 as all ADS-B Out installs in certified aircraft must meet 2020 compliance requirements (which effectively require an actual TSO'ed TSO-C145 GPS source in a certified aircraft, including glider).

An ADS-B Out 2020 complaint install (which sticking with Trig, requires a TN70 not a TN72 GPS source) will be seen by all aircraft. Wether that is with a TSO-C145 GPS source (for certified aircraft), or a "meets performance requirements of a TSO-C145 source (an option for experimental aircraft).... as long as they are all properly installed of course. trig foes not have a lower cost "non-TSO but meets performance requirements of TSO-C145 GPS source".

In an experimental aircraft not intended to fly where the 2020 carriage mandate applies (pop quiz: where do gliders need ADS-B out even with the carriage exemption? No it's not above 10.000') can install any GPS source as long as the ADS-B Out sets the correct quality parameters, and any old COTS GPS will require SIL=0 to be set which will guarantee that is ignored by aircraft with certified ADS-B In systems. It will still be seen by many portable ASD-B receivers, and certainly will be seen by PowerFLARM 1090ES In (assuming we are talking 1090ES Out).

The Trig TN72 is a TABS/TSO-C199 device, it is not TSO-C145, you can not install it in any certified aircraft (including gliders) and you can't use it to meet 2020 Carriage mandate requirements, but you can install it in an experimental aircraft for use outside ADS-B Out required carriage areas (including for gliders anywhere the 2020 carriage exemption lets you fly without compliant ADS-B out)...

And if your experimental glider is so equipped with a TN72 GPS source driving a Trig TT22 and it's properly installed then it *will* paint your glider on certified ADS-B In systems, both via direct 1090ES and via ADS-R for UAT In equipped aircraft. The TT22 importantly also ensures TCAS II systems can issue a RA (resolution advisory) against the glider, a pure UAT Out systems with no transponder cannot and will not cause TCAS to issue an RA. UAT Out equipped aircraft are also never visible to PowerFLARM (they can trigger PCAS if also transponder equipped), so for that reason avoid UAT Out use in gliders and towplanes.

A properly configured TT22 and TN72 GPS source will also trigger ADS-B ground services for your aircraft when in range of ADS-B ground stations (which won't help at all with PowerFLARM which can't decode any of those ground based services, to receive ADS-R, or TIS-B, or FIS-B ground services you also need a separate ADS-B In/non-PowerFLARM receiver as well as a suitable ADS-B Out system. And with reception on UAT to receive FIS-B).

---

On mixed installs with other potential ADS-B Out systems I would want to see the details of what exact ADS-B Out transponder is being used, but a TN72 in an experimental aircraft may well work with multiple different transponder options. TSO-C199 was intended to provide interoperability like that. And that will get you ground services and visibility on certified ADS-B In receivers. But be sure to ask the vendor if not Trig that they guarantee all that works... In practice the way to go today for ADS-B Out in gliders in the USA is to start with a Trig TT22 and use the TN-70 or TN72 and follow Trig's install documentation exactly.

---

Unfortunately Trig, who makes great stuff--their TT22 and associated GPS are great products, is saying some stuff that is a little sloppy again, their comment about triggering traffic services for gliders is made without the warning that a PowerFLARM can't receive those services. And they don't qualify TN72 is only for experimental gliders... I wish we had regulations that provided installs of that in certified gliders, as far as I understand we do not. I wish there were regulations (and maybe a STC) that allowed that. I'll talk to Trig and see if they can help be clearer here.
  #7  
Old September 22nd 17, 02:41 AM posted to rec.aviation.soaring
Darryl Ramm
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Default ADSB visibility with non certified GPS

On Thursday, September 21, 2017 at 6:20:54 PM UTC-7, wrote:
What hasn't been discussed is how often non-approved ADSB out sources are actually being ignored.


Ah I think we've been over what matters here many times, but it is a mess.

100% of certified ADS-B in systems will ignore the ADS-B data from 100% of ADS-B Out systems that use a COTS/non-complaint GPS source 100% of the time..

So airliners, fast jets, regional jets, etc. which if they have ADS-B In at all will be a certified In system, definitely won't see some scabby ADS-B Out install using a COTS GPS source. Since many of those aircraft today have TCAS II they will be see the transponder via TCAS and be able to issue TCAS TA and RA fro that target. However the gap in the middle is with many high-end GA aircraft that have certified ADS-B In but no TCAS, they won't see a crappy COTS driven ADS-B Out. But at the low-end GA market non-certified portable ADS-B In systems will see those COTS powered targets. That is kinda brain dead but it's how it is and easy to work around.. don't use a COTS GPS source....

With the relatively low price of theTN72, if owners want to equip an experimental glider with ADS-B Out there is no excuse anymore for using a COTS GPS source. I really don't want to get into how many GA aircraft might or might not be affected, just do it properly and install a TN72 or TN70 system. COTS GPS is just the wrong thing.

  #8  
Old September 22nd 17, 03:31 AM posted to rec.aviation.soaring
Darryl Ramm
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Default ADSB visibility with non certified GPS

Walt, I think you are misunderstanding what Trig wrote. A TN72 GPS Source will be seen by everybody. That is why anybody doing ADS-B Out in an experimental glider with a TT22 should be equipping with at least a TN72 (or TN70, TN70 required for certified gliders).
  #9  
Old September 22nd 17, 01:25 PM posted to rec.aviation.soaring
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Default ADSB visibility with non certified GPS

Darryl,

Thanks for the reply. Very helpful.

Gary
  #10  
Old September 22nd 17, 05:06 PM posted to rec.aviation.soaring
Dan Marotta
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Default ADSB visibility with non certified GPS

Jumping into the middle of this - what's the real reason to ignore an
ADS-B Out aircraft simply because the GPS source is "crappy"?Â* So what
if the position is off by 100 feet or so?Â* My PowerFLARM routinely
reports targets at 200 feet or more altitude difference, e.g., I may get
a report of a target 100 feet high and spot him a hundred feet or so
lower than I am.

It just seems ridiculous to ignore another aircraft which might be on a
collision course simply because his altitude or position may be reported
as a couple of hundred feet different from where he is. That's what
looking outside is for.Â* Following the same logic, of what use is a
non-TSO compliant GPS in an experimental aircraft if it will be ignored
by other aircraft?

Inquiring minds and all...Â* BTW, I plan on installing a TN70 to mate
with my TT22 in my certificated glider.

On 9/21/2017 7:41 PM, Darryl Ramm wrote:
On Thursday, September 21, 2017 at 6:20:54 PM UTC-7, wrote:
What hasn't been discussed is how often non-approved ADSB out sources are actually being ignored.

Ah I think we've been over what matters here many times, but it is a mess.

100% of certified ADS-B in systems will ignore the ADS-B data from 100% of ADS-B Out systems that use a COTS/non-complaint GPS source 100% of the time.

So airliners, fast jets, regional jets, etc. which if they have ADS-B In at all will be a certified In system, definitely won't see some scabby ADS-B Out install using a COTS GPS source. Since many of those aircraft today have TCAS II they will be see the transponder via TCAS and be able to issue TCAS TA and RA fro that target. However the gap in the middle is with many high-end GA aircraft that have certified ADS-B In but no TCAS, they won't see a crappy COTS driven ADS-B Out. But at the low-end GA market non-certified portable ADS-B In systems will see those COTS powered targets. That is kinda brain dead but it's how it is and easy to work around.. don't use a COTS GPS source....

With the relatively low price of theTN72, if owners want to equip an experimental glider with ADS-B Out there is no excuse anymore for using a COTS GPS source. I really don't want to get into how many GA aircraft might or might not be affected, just do it properly and install a TN72 or TN70 system. COTS GPS is just the wrong thing.


--
Dan, 5J
 




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