AP flys straight through ILS Glideslop

[chriscalandro]

Coming in from underneath
I’m in alt hold mode with vnav armed
Glide slope comes in and captures
Airplane flys straight through glideslope.

Works fine on RNAV approaches.

Airplane is a Glasair 3 and the default settings have been fine for me with minimal complaints other than this. I’m coming into the GS somewhere around 150kts indicated.

 

[Rhino]

I'm assuming an ILS approach. What navigation source is selected?

 

[chriscalandro]

It's the IFD 440. The 440 is set to VLOC. I manually made the switch vs allowing it to auto switch

 

[Rhino]

When are you arming VNAV? If I'm not mistaken, VNAV will not accept an arm command until there is an actual glideslope indication. You can't simply arm it beforehand. I could be wrong about that though. I don't fly ILS approaches.

 

[chriscalandro]

You’re correct about that. I’m arming it after the glide slope comes up.

The display also shows that it’s armed. End ready to capture.

 

[skysailor]

Is the HSI depiction magenta or green? If the 440 is in ILS and the Skyview is receiving that analog data, the HSI will be green as ILS is analog. Can you post a screenshot or photo?

 

[chriscalandro]

It’s green. I don’t have a photo.

 

[skysailor]

That confirms your ARINC 429 module is working and getting the correct data. This is an interesting issue. The system worked flawlessly in my Glasair. The only obvious difference for me was I was always fully on speed at glideslope intercept (Navy carrier habits) so my speed was 68 KIAS. Perhaps try something slower (90 KIAS perhaps) to see if there is a difference. Have you contacted Dynon Support directly? They are pretty good.

 

[chriscalandro]

after many more flights the answer to this ended up being a combination of not capturing the glideslope at 200kts and some autopilot tuning.

 

[airguy]

Yeah, a 200-knot glideslope capture might be problematic