A320 family rocking

APPR was not engaged.

What part of autopilot was engaged then?

Speed and altitude.

That’s the problem. You can’t decrease to 160kts without descending. You aircraft dips down due to the lower speed (to not stall), pitches back up to correct itself, the speed can’t catch up to this change so the aircraft overshoots the altitude, repeat. Suddenly, your aircraft is rocking up and down violently because the set speed and altitude can’t keep up with each other.

To fix this, you should either be manually descending when on final and lower your speed to 160kts or do this via autopilot (VNAV or APPR). Make sure all corrections are gradual. Try not to go from no flaps to full flaps just like that. Think of it like step-climbing. To achieve the desired outcome, you must take small steps instead of one big leap.

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Hey man!
That happens to me sometimes you just need to fly it gently. What I mean is that don’t extend the flaps to much on approach what I’d recommend you to do is:

  • extend the flaps gradually.
    For example extend them full only at 131 knots.
    Extend them whenever you feel that your plane is going up too much i.e if you slow down to 145 at flaps 2 and see that your craft nose is going up too much extend flaps to 3 etc.

  • Use trim. A tip that I have for the trim is that you see the line in magenta that is in the trim square? When it disappears it means that you’re good/stable so just monitor your trim during the approach. you can do it during cruise and departure too.

  • make sure you were below the glidescop alt while turning on appr.

  • make sure you were stable enough (not to high, lined, at a good speed when engaging appr.)

Hope this will help !

But if i’m not descending how do I slow down?

You should be descending. Check my last post one more time, I made a few tweaks. You shouldn’t be at a set altitude of 3700 AGL when lower your flaps and speed to your landing configuration. 3700 AGL is way too high to be at 160kts and definitely too high for your final approach.

Try to fix the power and change the slope to adjust the speed as in reality.
Because IF’s A/P is a simple speed regulator like in a car. The A/P of Airbus behaves like car speed regulator only at cruise (let’s say, to be simple).
Example for a A320 (57T)
Takeoff (FLEX 56°) N1 89 %
Climb N1 86.5 %
Descent IDLE

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For all the people that think Trim is a sort of magical thing that, if not being used correctly does weird thing with your plane, it doesn’t.

Trim doesn’t change anything about how the plane flies. It only changes the pitch of your horizontal stabilizer. So you don’t have to turn your device that much if you want to descent or climb.

The difference per trim setting:
(_) 100%

(+) 100%

Can you do a video of it rocking? This will prevent a lot of guessing.

Rocking back and forth may indicate you are going too slow for your configuration. I almost always fly the 320 and have not had any issue.

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