Transponder TT21 versus TT22 - Considerations

Just send off this question to Trig's North American Support. After having a telcon with him today regarding these issues, he stated that Trig has verbally told him that the TT21 would NOT be compliant for the ADS-B out mandate in 2020. This was based on some recent conversation with the FAA dealing with the ADS-B out program. He recommended that the question be passed on to Trig so they can give their formal reply:


Bruce Grammon
TRIG Support North America
Mid-Continent Instruments and Avionics

Bruce,

I'm a pilot with plans on installing the outstanding Trig transponder in my sailplane for flying in the Western United States where altitudes 15,000 to 18,000 frequently occur. But, I'm uncertain which model I should buy. My considerations:

1) I fly above 15K msl frequently; Is there any regulatory or practical reason to use the higher power TT22?

2) Cost is a consideration. Gliders are not mandated to use transponder below Class A airspace (excepting Class B and C). Nonetheless, I consider it a safety issue and morally correct to avoid mid air collisions with airliners.

3) Power consumption is a factor. What is the average power use increase using the TT22 versus the TT21?

4) Should the FAA change their mind regarding ADS-B out compliance and require it for gliders, can the TT21 be used for ADS-B out in the future?

Please forward these questions to Trig to help me and fellow glider pilots make the right decision on selecting Trig transponders.

Walter Rogers "WX"

By all means get clarification on the point he was making, which to put it clearly is that Trig TT-21 is not TSO-C166b certified, whereas the Trig TT-31 and TT-22 are. Trig are usually remarkably responsive.

However a really hard/most expensive issue you face if intending to meet the 2020 carriage specifications (start at AC 20-165A) has nothing to do with any of the questions asked. It's meeting the requirements for a IFR/WAAS TSO-C145c (or similar) GPS source and finding somebody who can work with a FSDO on field approval (which the FAA would ideally like based on a prior STC, which there were none for gliders... but hopefully you start with the same GPS source and 1090ES data-out capable transponder installed via prior STC in some GA aircraft and check in with the FSDO folks first). That TSO-C145c GPS receiver will currently cost you more than a new Trig TT22.

If your glider is experimental then it may be all moot, if you just want to say "play" with ADS-B data-out then you can likely install a non-compliant system with a COTS GPS. You might get a friendly letter from the FAA pointing out you are flying around with a non-complaint system. And whether you have a fully TSO-166b complaint transponder may not be relevant. Lots of things to discuss there with any vendor before trying to do that.

Now if you ask any avionics manufacturer what power-transponder you should install and state you fly above 15,000' expect to be pointed at regulations that state you are required to use a 250W transponder, especially when its clear you intend to copy the world on the answers... even if in practice it mike make no difference.

If you fly in busy airspace, with airliners and fast jets etc. Please install a transponder. Whether it is a Trig T-21 or TT-22 has really no difference for the usefulness of that transponder. If you intend in future to go though all the money, complexity and hassle (uh why?) of installing ADS-B data-out as well then the question about TT-22 TSO-C166b certification may become relevant.

If "cost is a consideration" then that question likely answers itself -- save your money and forget doing ADS-B anything. And my question for folks who worry too much about ADS-B anything starts with why exactly do you want it/what extra service/capability do you expect to receive from having ADS-B data-out or in....

http://www.aeroshop.eu/en/funkwerk-t...c-monitor.html

Does any one know if the unit in the link above will interface with the Trig transponders for ADSB?

On Tuesday, January 20, 2015 at 3:51:37 PM UTC-8, Ventus2NZ wrote:
http://www.aeroshop.eu/en/funkwerk-t...c-monitor.html

Does any one know if the unit in the link above will interface with the Trig transponders for ADSB?

And here we go. What exactly are you trying to achieve? no
"interface with" tells us nothing. Where are you? To meet what exact regulation/requirement or technical goal (e.g. I want my buddies with PowerFLARM ADS-B 1090ES data-in to see me)?

A string will "interface with" a tin can... the results may or may not be what you want.

Are are in New Zealand? The USA or elsewhere? If in the USA are you flying a certified aircraft? Especially if in the USA... the system you pointed to is *not* a WAAS/IFR complaint GPS and cannot be used to meet USA 2020 ADS-B Out carriage requirements (but we have no clue if that is relevant to what you are trying to do or not...).

It is my understanding that EASA approval exists for connecting non-certified GPS to mode S transponders to generate the ADS-B out data. In particular, the Garrecht VT-01 is approved in this manner and I think the Trig as well.

Since there are reciprocal agreements between EASA and other CAA's, the EASA approval should allow this practice in countries that reciprocate with EASA.

On Tuesday, January 20, 2015 at 4:26:05 PM UTC-8, Dave Springford wrote:
It is my understanding that EASA approval exists for connecting non-certified GPS to mode S transponders to generate the ADS-B out data. In particular, the Garrecht VT-01 is approved in this manner and I think the Trig as well.

Since there are reciprocal agreements between EASA and other CAA's, the EASA approval should allow this practice in countries that reciprocate with EASA.

In a word NO. In two words HELL NO.

The NEMA GPS source used by a VT-01 does not meet any RTCA or EASA specification, and neither is is required to for it's intended (glider/light aircraft VFR) use in Europe.

There is no specific EASA requirement the VT-01 is required to meet for it's intended use, and in general it's worth being aware that EASA does not have an equivalent to the blanket FAA ADS-B mandate that is coming in 2020 (which gliders are exempt from). The relevant starting point is EASA AMC 20-24 (2008) which requires fit in new aircraft starting 2015 and retrofit in existing aircraft by 2017. But this *only* affects aircraft with MTOW greater than 5700kg or maximum cruising TAS greater than 250kts.

So there is no approval this meets, there is no relevant reciprocal agreement (reciprocity of ADS-B requirements for airliners etc. in EASA and the FAA is a long seperate discussion...), there is no nothing, there is no way any NEMA GPS source can meet the current FAA ADS-B Out GPS source requirements. And again, if you want to understand ADS-B Out approval in the USA start at FAA AC 20-165A.

And to be clear the VT-01 does not claim to meet EASA AMC 20-24, and even if the transponder itself did, any system trying to use a NEMA GPS source could not.

Also worth noting that "does it work" is not the same as "is it approved." ADS-B approved installations are by specific equipment for specific certified aircraft. At present, I'm not aware of any approved installations for specific gliders. Please correct me if I am wrong.

On Tuesday, January 20, 2015 at 5:29:06 PM UTC-8, wrote:
Also worth noting that "does it work" is not the same as "is it approved." ADS-B approved installations are by specific equipment for specific certified aircraft. At present, I'm not aware of any approved installations for specific gliders. Please correct me if I am wrong.

And "does it work" required careful definition of what exactly "work" means.. (e.g. would ATC see you at all? Would you receive ground based ADS-R and TIS-B service in the USA, etc.). Connecting two boxes together and transmitting something that is a flavor of ADS-B Out is a very low-bar, likely uselessly low.

And the corollary to "is it approved" is can I as a pilot or A&P get into trouble if I just go ahead and do it if it is not approved... and in the USA in a certified aircraft the answer to that question is very much yes.

USA ADS-B Out approvals are available now via FAA field approval, so in that sense they are based on specific instances of installs, as I already said the FAA wants that to be based on existing STCs, again all covered in AC 20-165A. The STCs that the FAA want to based that on were often AML (approved model list) STCs, so covering more than one specific aircraft type/install situation. No STCs/AML STCs exist for gliders that I am aware of, but solving that problem starts with a call to the friendly staff at your local FSDO, and being willing to write a large check for a suitable GPS and to pay the A&P/IA/shop to do the install and spend time dealing with the field approval. Where folks go into this with their eyes open and have good contacts at their local FSDO and involvement from the vendors I expect this to be quite doable in a certified glider. The willingness to spend $$$ and a reason to bother are all anybody need to get started...

Daryl,

First, I have no intention of equipping with ADS-B out and agree that there is little or no value to gliders. My interest in having a Trig that is compliant for ADS-B out is just in case FAA changes their mind and mandates it for gliders in 2020. Yes, the complexity of certification and cost are prohibitive. I'm just trying to consider whether it's worth it for an extra $300 and slightly higher power usage to be "ready".

My main interest is to protect myself against fast jets and airliners etc in busy airspace.

Thanks for all your explanations and background in this discussion... although it sure makes a decision on which unit to purchase difficult. I agree the TT21 is probably all I need for the time being.

Walt Rogers WX

If you fly in busy airspace, with airliners and fast jets etc. Please install a transponder. Whether it is a Trig T-21 or TT-22 has really no difference for the usefulness of that transponder. If you intend in future to go though all the money, complexity and hassle (uh why?) of installing ADS-B data-out as well then the question about TT-22 TSO-C166b certification may become relevant.