Transponder - operational check

[paulrkuntz]

I'm completing my first homebuilt and haven't owned an airplane before. How do I locate an avionics shop that is licensed to check my Dynon SV-XPNDR-26X transponder installation for compliance with the regulations? Do I have to wait for this checkout before I apply power to the transponder?

 

[dynonsupport]

First, the transponder doesn't transmit just because it has power. Just like any other transponder, it has a standby mode, and this is the default mode. If you power it on, you can verify that SkyView talks to it. If you get SBY 1200 in the transponder status area you know the communications are OK.

Any avionics shop that can test a transponder can test our transponder. If you don't have a shop on your field, just look in the phone book for an avionics shop near you You can't operate the transponder until the check is done, but the testers are portable so you can probably find a guy that will come to you, or if you live in an area where they are not required you could fly to another airport without it on.

A strict reading of the rules is that the transponder check must be re-done anytime anything that can affect the transponder altitude has been touched. So it doesn't make any sense to have the check done until you are ready for your first flight. Plus, they expire every few years, so why have it getting used up on a non-flying plane?

 

[jbeaver]

I have the SV-XPNDR-262 installed and I'm trying to verify that it's working properly.  I see "SBY 1200" in the transponder status area, so the SkyView is talking to it, but it always stays in SBY mode even when selecting one of the other modes (ALT, ON, GND, etc.).  Is there something I'm missing?

thanks,

 

[jakej]

Did you use a premade wiring harness for the 262 ? If not, can you show a diagram of what you connected on your website ?

Jake J

 

[jbeaver]

I did not use a pre made wiring harness for the 262, but I wired it per Figure 66 in the SkyView install manual. The SkyView sees the transponder fine and I can update the code, so clearly the power, ground and serial lines are working correctly. The XPNDR GPS IN is connected to one of the serial outputs on my GTN 635, but I don't know how to confirm it is receiving a correct signal. I wouldn't think that would impact the ability to change the mode though.

 

[jakej]

Did you connect the external standby ? If yes then you probably have that 'on' however exactly what pin numbers you've connected to would be good to know. As an aside, some of the numbers and lines don't line up properly so that needs to be checked carefully

Jake J

 

[jbeaver]

I cross checked the diagram with Table 40, so I'm virtually certain that it's wired correctly. I do not have the external standby, mutual suppression, squat switch or ident switch lines connected.

 

[dynonsupport]

You cannot get the transponder out of standby until you set your aircraft hex code. This is a TSO requirement and is almost always the reason for this issue.

Page 11-13 of the install guide mentions this, but there's a lot going on when setting up a new plane so it does get missed now and then.

 

[jbeaver]

Thank you; that was indeed the problem! Everything seems to work perfectly now.

 

[swatson999]

The manual says NOT to connect a GPS line to the XPDR at this time. What would happen if I *did* connect one, so I don't have to crawl back there later and muck with the wires?

 

[dynonsupport]

The only GPS you should ever bother to hook up here is a TSO C154 GPS, aka a Garmin 430W, 530W, 480, or GTN product. Anything else is just wasted effort since they won't meet the 2020 requirements ever.

If you do have one of those, you can hook it up with the resistor as specified in the manual. Nothing bad will happen, but it also won't use this right now.

 

[swatson999]

Thanks, that's what I needed to know. I have a 430W, so will connect the GPS Out from that to the XPDR.