MGL Avionics User Forum

For two years this has been doing my head in. I have had no problems in the past with Garmin stuff but somehow MGL is defeating me. I am trying this for real and not on the simulator and really would appreciate a step by step guide (Guess there was one on the old board). At the moment I use a Direct to with the autopilot to an airfield at 2000ft and then arm the ILS. It takes me to the extended centre line but then decides it wants to head for the mountains (literally). Alternatively I have selected a direct to airfield, selected a runway and then selected direct or via an intercept. Autopilot states its has VSI but I fly overhead at 2000ft! Would appreciate if anyone either has a step by step guide or even better photos of each step. I need to get this in my head so it works without thinking so at least I can practice some instrument approaches before I have to renew my rating.

It's largely automated.

You would select the desired runway and go via intercept.
For all of this to work you must ensure that the intercept point is well below the glide slope as the AP will refuse to dive onto the glideslope. So make sure the intercept point is a realistic distance from the threshold.
Also, make sure your glide slope angle is good - for most of our smaller aircraft I recommend a 4 degree angle (rather than the 3 degrees standard angle that is more suitable for your average Boeing).

What happens: You activate GLS via intercept. The Intercept point is just a waypoint and the AP is directed to it. The threshold is the next waypoint after that. If it arrives at the intercept point it does a few checks - one of these is the approach angle - it will not active the GLS if your aircraft is not pointing within +/-40 degrees of the runway or if you are already on top of the glideslope. If it is happy all it well it will then activate the GLS with the aim of intercepting the glide slope and capturing it - you just handle the throttle to control speed.

Now, this has never been intended to fly a circuit - the idea here is not to activate any form of GLS overhead. You would fly the circuit (which you can do on AP just using the heading bug) and once on long finals and well below the glide slope you activate GLS (it would have found the GLS for you by now and show you the GLS as a row of BLUE crosses. If you see that - go to NAV menu and select "Activate GLS" and the AP will know what to do - the crosses turn green to show you that the GLS is activated.

GLS via intercept is similar to a normal STAR approach except you can come from any direction.

Rainier

Rainier,

Thanks for this quick response. So to make sure I have this correct. I first need a FPLAN similar to an RNAV approach where the Intercept is an Approach Fix within 40 degrees of centre line and below a 4 degree glide slope. It would make sense to have an Initial Approach Fix as the first waypoint, the intercept as the Final Approach Fix (second waypoint) and the airfield as the final waypoint.
So I am flying along somewhere or other and then select the appropriate FPLAN the a/p takes me to the IAF at whatever altitude I determine is safe. After reaching the IAF the a/p sets course for the FAF and I select GLS via intercept and after the FAF the a/p will intercept the GS from below. Control power for the GS and wheels down etc.
The alternative is GLS direct which if I am not using a FPLAN then I would activate a Direct To from an extended centre line position (<+/-40deg) below the GS and then select GS direct as before. The reason using a Direct GLS is that it could be a diversion to an unknown airfield. I should add I would be fairly desperate for this choice if the proverbial hit the fan as I would opt for an SRA at the nearest facility.
The Direct is what I have been experimenting with in the air and it seems to start off OK and then all goes wrong. I will make a concerted effort to get this nailed.

Ok, I’m using an Explorer EFIS, and Garmin 175 and Garmin 255 Nav com. It works well. Altitude and heading control is good. I’ve flown some 150 hrs with it and I learn something new every time. What I haven’t figured out is how to get the glide slope to show as well as the localiser. I’m an IT/techno dinosaur and have read the instructions lots of times, I’ve dialled in the ILS frequencies on each device but only see a CDI blue line. I’ve tried approaching from below, above, each side but No glide slope. I once flew into a grass strip and for some unknown reasons it worked both glide slope and localiser. Into another grass strip I saw a line of white crosses. Once. Is there a set of easy to use instructions so I can follow a published approach?

If you are seeing a blue line moving left/right - that's coming from your NAVCOM and is the localizer.
A horizontal blue line that goes up/down is the glide slope - it shows automatically if your NAVCOM sends it. You can't disable it in the EFIS.

The same info is also shown in your NAV status bar where you should see your tuned frequencies. If no glide slope bar shows it is either not sent or flagged.

The white crosses are created by the EFIS based on your database if it has geolocated runway information - based on your glide slope angle setting and desired touch down point along the runway (GLS setup menu) it creates a 3D guidance to that point whenever you are close enough to the centerline and runway. You can even create your own such guidance as a special type of waypoint to your favorite grass strip !
Any such blue/white GLS guidance can be "locked" (see NAV menu which will offer that option if the blue/white is showing). It then turns green and a GLS approach is active - your autopilot can follow the GPS based localizer and glideslope - don't forget to disengage before touchdown.
You can setup a missed approach trigger RPM - if that RPM is exceeded the approach is canceled and the AP remains on runway heading and initiates a climb until you tell it to do something else...

Just to close this from my point of view. Rainier was in the middle of June able to recreate the problem.
"OK forget whatever I wrote. I finally got a chance to do some flying.
It is the missed approach - it's got a problem. The RPM comparison is the wrong way around - it does a missed approach if RPM is below the threshold.
I will be releasing a new version later today."

That was in June 2023