Why does the Cessna 172 on an inbound course suddenly deviate as soon as the approach button is engaged?I’m

Question

I’m flying the Cessna 172. I’ve programmed the “Garmin 530” for the RNV 33 GPS approach to KISM with YONMA as the IAF. On the GPS/Nav switch I choose GPS. On the autopilot panel I engage nav with gpss and altitude hold. With this configuration, the plane follows the course precisely. However, as soon as I engage the approach button, the plane immediately deviates from course. This happens no matter where on the approach I am. If I don’t engage the approach button then the glideslope will not capture, altitude hold will not disengage and the plane will not descend The same thing happens on an ILS approach.

Answer 1

Hi Dmaury

I'm not with Laminar Research, just a fellow simmer in the UK. I am also on vacation trying to reply to you from memory lol!

If your operational flight plan includes and ends with the RNAV (GPS) 33 approach via YONMA, AXMEB & LOJUF to KISM RW33, then it is possible that you will formerly have to activate the approach in the GNS530 Procedures page first, before getting to the YONMA waypoint and before pressing the autopilot approach button to finally lock onto the glideslope.

You certainly would have do this on an ILS approach to a given airport and it may be that you have to do the same thing with an RNAV approach?

I generally fly airliners so I'm wracking my brain trying to remember how things were done when I first started flying GA aircraft.

Hope this helps

Regards

Comments

I’ve tried activating the approach on the 530 but to no avail. Still frustrated.