Not following the STAR

[flyingfudge]

I'm sure this is probably due an error on my part being unfamiliar with the aircraft & systems but I've flown this approach twice and it's done exactly the same thing on both occasions.

Descending and tracking perfectly in FMS NAV & VNAV until it passes PR511 and then it changes to LOC1 as it approaches PR512 ( see pic. ) stops tracking and starts to climb.

I'd appreciate it if someone could give me an indication of what's happening as I can't fathom out what I'm doing wrong. With Toto's expertise in programming it has to be my fault!

Many thanks .....

 

Log.txt

Edited January 9, 2022 by flyingfudge

[Jakobb]

While I do not know why it switches to LOC, the reason for climbing is that you are in pitch mode so it will maintain the last pitch. Maybe it's switching because it is detecting the same ILS frequency somewhere in the vicinity? 

[flyingfudge]

I didn't touch anything from the beginning of the FMS guided approach. It was flying perfectly until it passed the centreline of the opposite end of the runway and then the PFD FD annunciators changed to what you see in the picture and it changed to VPTCH, stopped tracking and started to climb. 

[flyingfudge]

Hi. Any update on this?   It appears to have changed over to LOC 1 as it passed through the runway centreline. It was flying the arrival normally up to that point.

[amyinorbit]

Testing this right now, but my suspicion is that you armed APPR while on the star. If that’s the case, the FMS could have initiated a NAV-NAV transfer, thus setting the autopilot to follow the ILS rather than LNAV.

[amyinorbit]

I cannot reproduce this even by arming approach. My only other hunch is that you accidentally hit the NAV SRC a button on the DCP, which would have caused the NAV source to switch to LOC

[flyingfudge]

Hi Amy. Thanks for trying it. I actually flew the route twice and it happened exactly the same on both occasions so it's a bit strange.

If you can't reproduce it then maybe I've got a conflict somewhere with my system. 

[amyinorbit]

If it has happened twice, could you please try and get a video of it? Aside from arming APPR much, much too early, I'm not sure what could cause it

[flyingfudge]

Sure, I'll try it again tomorrow.