GNC355 (GPS175) Questions

I recently replaced my GNS430 (non WAAS) with a GNC355. After a few flights I have a couple questions.

My GNS430 had a feature that displayed Vertical Speed Required (VSR) which I used to determine when to start my descent. It planned to the last waypoint in a flight plan or a direct to waypoint. The GNC355 has a similar feature using the VCALC utility. But I have not been able to make it work unless I go to the utility and input the waypoint. The Pilot Guide implies that last waypoint in flight plan or direct to is the default setting. Is this normal?

I have GRT EFIS that the GNC355 displays on. A few times I've input a direct to in the GPS and the waypoint data box on the EFIS displays the correct heading, distance and time but displays ALT rather than the waypoint (airport) name. After a few minutes, ALT gets replaced with the proper name. Is this normal?

Thanks for the help.

Jim Butcher

While my post won’t address your concerns I was wondering how difficult was it to swap out your old 430 for the 355? Did you do the wiring changes yourself?

I can't speak to the second question and I have no experience with any GPS navigators before the GPS 175 that I have now. I can tell you what I've found with VCALC, yes it needs to be setup through the Utilities. You can pick any waypoint on your flight plan. I use the PC Trainer app (if you haven't looked at that, it is a great way to get familiar) and have attached a couple of screen shots. I changed a couple of the user fields to show VSR and Time to TOD that way I can monitor the VCALC results as I approach TOD.

I haven't used this feature in flight yet and to be honest, I'm not sure I can justify 2 user fields for this. Maybe one for Time to TOD would be sufficient. It certainly looks like a useful feature.

Jim, the wiring changes are not too difficult. The signals the new box requires and the same as the 430 with the exception of VOR signals. The most difficult aspect was removing the hi density dsub pins from the 430. I tried a green/white tool without much success. I have a Amp tool that works well but the hi density adapter broke. I've since purchased replacements. I actually cut most of the wires and installed new pins. I used an inexpensive crimper but several of the pins didn't crimp properly. So I finally used my old B and C BCT1 to make a final crimp. While struggling with pins there were many times when I thought how much easier it would have been to just slide in a 430W, but now that I'm using it I really like the touch screen interface.

Claude, I've been using the simulator a lot! I also have found a lot of You Tube videos on using GTN boxes very useful.

Jim