Autothrottle Issues

So I’m quite new to infinite flight, and since my piloting skills are not that great, I am quite reliant on the autopilot during approach and landing. However, I always find the autothrottle to go crazy when I try to slow my plane to my VREF and engage APPR. (on an a320, about 130-140kn). It will set the throttle to idle, then slow down far below the set speed, which will cause the plane to pitch up rapidly and near stall. In response to this, the throttle revs up violently and the nose rapidly pitches down, which then results in the plane speeding up far too much. This process just keeps repeating over and over, until eventually it says ‘AUTOPILOT DISENGAGED - CHECK FLIGHT PARAMTERS’.
Am I doing something wrong or is there something I can do to avoid this? I will always set my flaps and gear.

Hello do you use flaps? And at 140 knots what settings of flaps do you use?

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On final I will always use full flaps

Not withstanding the obvious “dont use autopilot and learn to land the aircraft manually”, confirm you’re bang on the glide slope?

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Okay, is this only happening once you get very close to the runway and at those speeds of under 160 knots? If so I suggest you turn the speed off on the autopilot and take manual control to stop it going too low.

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Haha yes I will try to learn to fly manually…but yeah I think I am on the glideslope

I suppose that is one solution, but do you know why the autothrottle misjudged the speed so much?

No it happens a lot to me also, I just started to take manual control as it would drop to 130 knots and nearly make me stall even though the speed was set to 140

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Alright thanks for the help then, guess I’ll just accept that autopilot isn’t perfect and learn to fly manually :)

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Do not despair and read this :-):

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Helllo hope its going welll I fly the A320 alot aswell do you use spoilers to slow the pane down.and when.decending do you use alot of.flaps at a higher altitude.because using flaps on 3 on 6000 ft wil cause the panes nose to.pich upI usually use 1 flap at around 7000 ft 2 flap at 4000 ft and 3 flap at around 3000 ft but at around 7000 ft I disengage.my autopilot to start my decent manualy and to control the final by my own and dont use any spoilers under10 000 ft otherwise you wil lose alsot of speed and end up into a stall so thats how I do it hope it helps💪

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I usually won’t use the spoilers to slow my plane down at this stage…also i don’t know if I’m just inexperienced but flaps 1 at 7000ft seems a little early?

Well guess I can’t do massive crosswind landings then, and boy doing one manually is a quite a nightmare for me at the moment…

When I feel.im coming in to fast I usually put one flap at 7000 ft so.slower me down and gives me time to get a easier decent but every person has theyre own way of setting flaps I usually look at how far I an from the runway remember wheels also creates drag so.make sure that when.yiure wheels come out you have enough engine power for youre.landing and landing manually will help with speed and altitude .but yeahhh cross winds is difficult on.manual I also just started.Landing in them just make sure you keep youre nose if the aircraft pointed at the runway and I use normally full flaps on crosswind landings

Like most functions in the autopilot modes, it is a good idea to do things gradually. You can lower the speed in increments to get it to go down in a more controlled way, which works well. Alternatively, turn off the auto throttle and manually go down to close to your desired speed, then engage it to get the auto-50% throttle before the plane figures the rest out itself.

The autopilot on some aircraft seems to be better at anticipating what it needs to do - the 767, for example, starts to throttle up as the speed drops towards the set level. You just need to learn the characteristics of different aircraft for this function, as you do for other aspects. Examples: (1) E-Jets and A380 habitually overshoot the set heading on a turn, so best to set for 2 degrees before and then double-tap when the plane has leveled out at the heading you actually wanted, and (2) A330 drops on the final flaps setting, so you need to factor that in as you near the runway.

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Thanks for the helpful insight! I haven’t tried the 767 year mainly because it doesn’t have APPR 😆. But year the narrow body jets like the a320 and 737 tend to undershoot the speed a LOT. I’ve just tried a couple flights where I disabled the autothrottle to gradually slow down the plane myself, and then engage it when I near the target speed, and that works wonders. Guess I’ll learn more as I get more experienced!

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