Glide slope nose pitch

Hi everyone

I find when I am fixed on to LOC and waiting for GS to engage, when the green curser comes close to my altitude my aircraft pitches quite sharply up to curser then dips down to catch the green dot up for the aircraft to follow the descend on APPR.

Is this normal? Does this really happen in real life flight ?
Or is it me doing something wrong.?

I find the same thing happening, mainly in the A319,320, 321. I doubt it occurs in real life as it would be a noticable surge up and uncomfortable for passengers.

You can anticipated it and help by adding extra power just before GS capture which smooths it a bit.

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It mostly depends on the flaps settings you’re using, and the speed you engage the LOC. Utilizing trim is a great way to keep your plane in good shape, whether it’s at cruise, takeoff, landing, climb, or descent. Adjust the percentage so that the purple bar doesn’t appear anymore. If the purple bar is indicating towards the bottom of the trim tab like in the above picture, you want more positive trim but I’ll really make sure with that I said first. I always make sure to follow the correct speed, etc, and works perfectly!

I find that the pitch up at GS capture that the OP refers to happens even when flaps, speed and trim is all correct.

Its like the AP wants to level off and hold altitude for a bit before starting the descent again. Ideally the transfer from ALT / VS mode to Glideslope would be seamless.

It kind of depends on what ATC ask me to do as well, as generally I get requested to fly at 3000 altitude approach witch is normally well below GS level. Plus now we get asked to go a certain speed as well to maintain space between each aircraft.
So when the GS is dropping to my FL the plane pitches up to climb to curser rather that the aircraft catching GS on the way down.
I have looked at previous peoples comments about this pitch up on GS and tried to do as they/you have said but still not a smooth transition when GS engages

The issue is that when an aircraft is “locked” on the ILS, the reverse of the normal primary flight controls apply …ie pitch controls altitude and power controls speed (normally it is pitch that controls speed and power is altitude).

So the aircraft uses pitch to control the descent on the GS. Because the VS mode is initially set to 0 when you are level, maybe it tries to set a pitch initially to hold level before the VS drops for the descent, and then the nose lowers again (thats why some extra power at that moment can help).

Of course in Approach mode we dont see an indication of what the actual VS is, but maybe it reduces from 0 after capture…

I would hope not. I’d feel bad for those without seatbelts 😁😈

The same things happen to me with those aircraft. I’m a Boeing fan so I don’t really fly any Airbus aircraft. Definitely something to look into to find out what’s going on.

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😄 And I don’t fly the Boeings because I can’t keep them straight on the runway at touchdown or rotation!

I often don’t use Approach mode anyway, and prefer to switch off AP and fly down manually, so I’m not usually too bothered. But I do think the matter should be looked into as the transition to GS capture should be smooth, assuming the aircraft is configured correctly and stable beforehand.

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Based on your description of the issue, it seems to be associated with the way autopilot works in Infinite Flight. It’s not a smooth system, per se.

The topic below is a #features request that may be of interest to you.

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Would this happen in real flight. Or is it just on IF sim ?

Yes usually in the airbus this happens.
But it’s done same when flying 777 family

The reversal of the function of pitch and power when locked on the ILS applies to real aircraft and Infinite Flight. That aspect of the simulation is realistic, its just the transition onto the GS that seems to be an issue.

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Ahh thanks for that info man. 👍🏼
This is what I thought it seems to pick up the APPR quite aggressively in IF.
Not just me 😁

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Not arguing that the AP can sometimes act a bit… funky.
However, catching the glide slope from below (as it should be done) usually minimizes these funky things.

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Wierd, for me, my plane always turns left and right constantly, I assume trying to put itself on the glide slope

The left and right swaying is trying to catch the localiser, and the pitching up is the glideslope capture.

Having things stable, trimmed, the right VS all set before capture will help, but I still get that bump up initially.

The swaying can be minimised by flying the localiser capture manually and getting the centre bar lined up before engaging the Approach mode.

But if you take too long doing this you risk ending up above the GS, then you miss that capture!

I often knock 500ft off my flight plan fixes on the approach in order to be lower at intercept and give that extra time.

No way to avoid it, it’s a limitation of the autopilot logic. I would imagine the simplest coding solution would just be to delay the glide slope intercept until the GS is a bit closer, but who knows.

If you wan’t an actual answer, you can try not using approach mode. Switch the nav source to NAV1 and then LNAV alone will follow the localizer. Then, you can just disengage altitude hold just prior to GS intercept and manually pitch down to intercept.

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I do catch the GS from below. And still aggressive pitch up to then pitch down to catch up GS again.
I’ve tried what other people say to do to stop this and watch the IF tutorials but this still happens. 🤷🏻‍♂️