Hi,

Is the Century IV autopilot in the Dukes capable of flying a coupled RNAV approach?  I was flying an RNAV 01 into KFRG with GPS mode active on panel, APPR active on AP panel but it didn't seem to fly the approach correctly, especially the glideslope indication on the HSI.

I figure given the age of the Dukes AP that it isn't able to fly this type of approach

Thanks,

Edited May 16, 20242 yr by KevinS137

At least with the GNS units, yes. They are capable of delivering the signals to the HSI that allow it to be coupled, same as an ILS. I've flown a handful of them at a number of airports already.

I'm not sure what the capabilities of the TDS and PMS units are.

It'll fly an RNAV+LPV approach just fine.  I know there are limitations or issues with the GNS GPS, but I don't know what those are.  I use the TDS GTN 750 and it works perfectly. 

39 minutes ago, Orlaam said:

It'll fly an RNAV+LPV approach just fine.  I know there are limitations or issues with the GNS GPS, but I don't know what those are.  I use the TDS GTN 750 and it works perfectly. 

Agreed. I have had no issues with the TDS unit.

Thanks for the replies, I’m using the TDS GTN750 so I’ll go back up and fly a few more approaches and see if I can get it working

10 hours ago, KevinS137 said:

Is the Century IV autopilot in the Dukes capable of flying a coupled RNAV approach?  I was flying an RNAV 01 into KFRG with GPS mode active on panel, APPR active on AP panel but it didn't seem to fly the approach correctly, especially the glideslope indication on the HSI.

Did you activate the N1/RNAV switch at the top of the pilot's side panel?

7 minutes ago, rmeier said:

Did you activate the N1/RNAV switch at the top of the pilot's side panel?

Shouldn't have to as long as the GTN's CDI is set to GPS.

46 minutes ago, rmeier said:

Did you activate the N1/RNAV switch at the top of the pilot's side panel?

This should not be switched unless you're using the old school RNAV unit rather than one of the GPS units.

Thanks for the replies, I did have the GTN CDI set to GPS.  I was flying a vectors to final approach instead of a full procedure (from a specific IAF) so not sure if that impacted anything. I was also using SayIntentions and it was vectoring me towards the FAF.  I had also activated the approach in the GTN after receiving my first vector.  I was above the glide slope intercept altitude by about 500 feet at the FAF due to not getting a timely descent clearance from SI but corrected for that and tried to reengage the AP but no luck

In the sim, intercepting from above doesn't usually work.

3 minutes ago, KevinS137 said:

Thanks for the replies, I did have the GTN CDI set to GPS.  I was flying a vectors to final approach instead of a full procedure (from a specific IAF) so not sure if that impacted anything. I was also using SayIntentions and it was vectoring me towards the FAF.  I had also activated the approach in the GTN after receiving my first vector.  I was above the glide slope intercept altitude by about 500 feet at the FAF due to not getting a timely descent clearance from SI but corrected for that and tried to reengage the AP but no luck

The rule of thumb is to intercept below glideslope. Autopilot in approach mode won't be able to  dive and catch up with glideslope below. You will have to manually descent to altitude below GS but in this case take precaution for CFIT 

4 minutes ago, ryanbatc said:

In the sim, intercepting from above doesn't usually work.

This. It's happened to me many times where I was too high across many aircraft with different nav systems.

If you'd been on the glideslope before the FAF, that might have worked.

In real life, some of the newer AP's tend to grab it if you're a little high... but some won't at least that's been my experience.

I’ll go back up tonight and fly a stabilized approach and see how that goes. This plane is really fun to fly, really liking the systems modeling depth. The other day was flying up into the low flight levels and didn’t realize I had accidentally opened the small side window so the cabin didn’t pressurize and the cabin temp was dropping hard so the cabin heater was working overtime.  Once I got repressurized the temp was not recovering but it turns out the circuit breaker for the heater popped (assuming from working wayyyy to hard). Reset it and the temp started recovering, it’s really nice to have this level of systems depth to keep you on your toes.

Happy flying!