The HSI is sent from the 480 independent of the position. We don't need position to display an HSI. The 480 is saying "display a CDI needle that is deflected 1.8 dots to the left" and we're doing that. Since the 480 has a lock, it's willing and able to do this. We'll display an HSI off a NAV radio which can never tell us position.
Your ARINC connection is apparently fine. We're getting CDI deflection over ARINC-429, so we're probably getting almost everything else. We are also getting enough data to know the 480 is a GPS, but not enough to call it a valid position source for SkyView.
Here's the issue: ARINC-429 doesn't support GPS altitude. Weird, but true. SkyView HAS to have GPS altitude, since this is what is used to determine your altitude for Synthetic Vision.
Serial data does support altitude, which is why we need the serial connection. That's literally all we read over serial is the GPS altitude.
So I went and looked at the 480 install guide, and sure enough, the 480 DOES NOT output GPS altitude anywhere. The 430 install manual specifically says this is sent out over aviation, sentence "z". The 480 doesn't list sentence z, so it isn't there.
Unfortunately, this means the 480 won't work as a position source for SkyView. You need a device that can send us altitude if you want SynVis and the moving map. We can fly the AP and HSI off the 480 no problem, but you need another GPS connected to do more.
Sorry we didn't see this earlier. I guess you're the first one to ever try and use just a 480 with your SkyView.
