Glide slope pointer sometimes not working

[gulredrel]

Hello,

there were earlier occasions, when ILS glide slope was not working, but couldn't trace it really.

Now it appeared again and I think it is something with initializing NAV system and VOR. Track attached to see, what was done. From memory I only can describe the symptoms.

• cold ramp start Kobuleti
• engine on
• INS on and aligning
• during alignment tune VOR to ILS and switch NAV mode to VOR

Result:

• Glideslope pointer at the bottom of HSI
• taxiing, switching master modes or whatever, GS pointer stays at bottom of the instrument and shows no reaction. Localizer needle works as intended

I think GS is working, when you only switch NAV master mode to VOR, after INS is fully aligned or something like this.

Please enlarge to better see image markings.

Beginning of RW, far in front of intended touch down point: VOR selected, LOC captured, GS pointer at bottom of ADI

 

TACAN or RNAV selected: GS pointer at bottom of ADI together with off flag:

   

 

Approach far below GS: VOR selected, LOC captured, GS no off flag, GS pointer at bottom of ADI; should be at top of ADI to bring me up to correct glide path:

   

Thanks

Jens

MB-339_20221119_no_glideslope.trk

Edited November 20, 2022 by gulredrel
added info on images and marked images; maybe you need to press ctrl + F5 to reload images in case they were locally cached before

[6S.Duke]

Hi, thanks for reporting, it is not a bug.
You need to switch to VOR mode to have the GS indicator working as the ILS works on the same ILS frequencies.
RNAV mode enables the GPS navigation through the CDU waypoint selection.
Anyway you can find all these information within the flight manual.
Moreover sometimes on some runways the ILS does not work, in this case check if the runway is active by contacting the ATC.

Inviato dal mio ASUS_I005D utilizzando Tapatalk

[gulredrel]

@6S.Duke Please check the last to images on low approach (will add image captions in first post to explain what to look for and insert some markings). The NAV mode is set to VOR but the GS pointer is not moving although the GS off flag is not visible.

Please try the track to see when I'm switching the NAV sources and see how the GS pointer reacts or does not in this case.

Using the same mission with a different sequence of setting up the same frequencies, ILS works. So I haven't figured out, what causes the GS pointer to always being at the bottom of the ADI. When ILS is working with both localizer and glide slope, the GS pointer returns to middle position when losing GS. Not in the example above.

 

Edited November 20, 2022 by gulredrel
fixed typo

[6S.Duke]

Thanks, we will have a check

Inviato dal mio ASUS_I005D utilizzando Tapatalk

[gulredrel]

Happens in 2.9, this time the GS indicator is at the top of the attitude indicator. Will try again and add a trackfile.

 

edit: Regarding the track. I saved one from the flight. But when playing it back, it didn't entered the right ILS frequency, so problem didn't show in the track. I took the controls in the track, dialed in the correct frequency and GS pointer worked ok.

Will see, if I can get it, if it occurs again. Weird thing.

Edited October 24, 2023 by gulredrel
added track info

[gulredrel]

With the addition of FD I tried my first ILS approach.

Tuned ILS Ramat David, Localizer needle was working correctly.

FD bars after capturing GS also worked but the GS pointer left on the ADI remained in the lowest position. Good to have FD bars now for steering commands.

Hopefully this weird GS pointer thing can be found with the track attached. It's not happening all the time.

20241103_RamatDavid_FD_ILS_approach.trk

[6S.Duke]

Thanks, we will have a look

Inviato dal mio SM-F731B utilizzando Tapatalk