Glide scope capture San Francisco

I did a short flight from LA to San Francisco in the a320, on the flight plan (world map) the last 3 waypoints had an altitude of 5000ft, the very last being at about 2500ft and roughly 7-8nm from runway.

I could not seem to capture the glide scope, should I have been a lot lower, perhaps 3000-4000ft just before the 3rd from last waypoint to be sure I would capture it?

I think the time I was at 2500ft on the last waypoint was a little late to capture maybe??


Check the ILS frequency. Have not checked recently but one of the runways — I think 28R — was not setting the ILS localizer frequency when starting from the World map. I had to look it up and set it manually. Might be fixed now but was an issue early on.

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Thanks I will check what runway I had set up in the plan.

If I disabled the constraints button, would the a320 decend below the constraint set out in the flight plan?

I normally have constraints enabled and when I do a managed decent it will level off at whatever the constraint is, but just wondered if the constraint button is a visual guide or that disabling it would allow me to decend lower.

I believe a visual guide but I don’t use VNAV. Not sure how the FBW model is currently working.

On descent, I manually set the altitude and then use one of the VS modes.

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The constraint button has no effect at all.
It only displays the constraints.
You need to modify the FMC data.

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The contraints button just toggles a visual display of constraints on PFD, it doesn’t force those constraints. Constraints I think are only figures that are followed during certain criteria in Managed ALT mode. You can override them by using selected alt mode to adhere to ATC ALT requests. There are quite a few ILS freq wrong all over the place (that I’ve found by trial and error), best to double check by looking them up online. If they are correct and tuned in then they should display on PFD in purple chevrons when LS is selected. If the GS/LOC are not displaying when close to an airport then chances are you are tuned into the wrong freq. Don’t go by what the flightplan ILS value is, look up online, and double check with value entered into MCDU under RAD/NAV button page. It can often be missing or wrong for your arrival runway.

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I will test next time as have the flight plan saved, I might also just drop to 3000ft then in selected mode to b sure.

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No need for trial and error with regard to your capture altitude. Just look up the respective ILS chart. If you don’t have the paid Navigraph charts, in the US all info is conveniently available for free via the Skyvector website.

If you still have trouble. Post more specific info here ideally including a screenshot of the cockpit. Easier to help this way.

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When you do find the glideslope you should alwyays aim to be under it to intercept it. A ballpark approximation for approach is 10miles out at 3000ft any higher you are too high. Too high means too steep a desent to meet it, so more controlled being under GS and meeting it before descending with it.

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You will find the correct frequency on the map.
No need for any other sources.

You need to enable the navaids in the filter menu.

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So why does the flightplan often adopt the wrong frequency for a given runway? Is it a drop down choice mismatch that gets sucked in to the flightplan?

I had a good example of altitude constraints today while flying around Germany. I have been setting altitude according to ATC but engaging Managed mode to get to that altitude.
I was at 16,000ft and ATC directed me to 12,000ft so I changed altitude dial to read 12,000ft then selected ‘managed mode’ and the aircraft only descended to 14,000ft and levelled off. I checked constraints and the waypoint I was approaching had a constraint of 14,000ft.
To descend lower than 14,000 ft I had to engage ‘selected mode’ then the aircraft descended to 12,000ft.
Hope this helps you understand managed mode / constraints a bit more.
My knowedge of this subject is basic, but it’s slowly coming together a bit the more I use it.

Good question. I have no idea.

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Where about’s do I see the ILS frequency in the a320 cockpit?

Also I notice that with constraints and managed altitude that the a320 will descend to the constraint and level off, if my altitude set is lower than the constraint, but when ascending I can go higher no matter what the constraint is. I guess the constraints are aimed at maintaining a particular altitude and not going below it, ascending is not part of it.

Below is a link for airport chart.

Where about’s do I find the frequency on airport charts?


See my other post on this thread on my constraint encounter yesterday. You’d need an a320 expert to give you an in depth constrait AP function description.

The ILS freq can be entered into the MCDU manually. Hit the RAD/NAV button and the half way down the screen on left is ILS frequency type a value and hit button beside this to enter one manually. This won’t disrupt your flightpath.
Alternatively go to FPLN ->DEST->APPROACH and select the destination runway/ ILS. Downside with this method being that it initiates a change of destination call to ATC which can mess up the original flightplan.

ps. I flew into SFO 28R yesterday and had to enter the ILS manually for the runway.

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Oh interesting then, so looks like a bug still. Thanks for trying that.

So just to be clear I can enter the ILS frequency at start of flight?

Just need to find out where to find the ils frequency on the airport charts.

The ILS Information is found on the respective ILS Charts for each runway not on the Airport chart.

Scroll all the way down on the Skyvector webpage you linked and you find the ILS charts eg. RWY19L, 108.9, capture G/S at 2800ft

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Enter it any time you like. I sometimes enter it 10 miles out when I noticed it’s missing.
Just google ILS SFO 28R and you will find several websites offering the info for free.
I use this one a lot

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IRL you check or reenter or check when ATC gives you the approach which to expect.

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