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a320 follow FDs in turbulance

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a320 follow FDs in turbulance

Old 17th Feb 2024, 12:03
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Question a320 follow FDs in turbulance

hello everyone
i am an copilot in a320,when i fly an ILS appr in manul,the final has a little gust wind,and make the airplane turbulance,this situation make me very hard to follow FDs which is up and down,and the cap at the left told me "push the stick"while the aircraft encounter an updraft,i am confuse the aircraft always keep 1G in normal law itself,why we still need to push or pull the stick to confront the up/down draft,can we just follow the fd?or how to follow the FDs better in the tubulance days,thx
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Old 17th Feb 2024, 22:41
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Know the reference pitch and power for the flight path you want. Set that. The FD will bounce around and eventually stabilise where you’ve put the airplane. The FD is there for guidance, you don’t have to follow it if it’s giving you nonsense. Turn it off in that case.
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Old 17th Feb 2024, 22:50
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how good is the 1g FBW function? is it true that you don't need to counter up- and downdrafts?

I guess there's small inaccuracies and delays so some minor manual corrections are necessary, right?
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Old 18th Feb 2024, 04:13
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i know pilot have to make action to confront the draft,i am confuse how many inputs of the sitck shoud i do…follow the FDs?or more the center of the FDs ?
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Old 18th Feb 2024, 05:55
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Originally Posted by waito
how good is the 1g FBW function? is it true that you don't need to counter up- and downdrafts?

I guess there's small inaccuracies and delays so some minor manual corrections are necessary, right?
You will have to counter turbulence, as in any other plane.
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Old 18th Feb 2024, 06:05
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Originally Posted by songzheng
i know pilot have to make action to confront the draft,i am confuse how many inputs of the sitck shoud i do…follow the FDs?or more the center of the FDs ?
It seems you're thinking too much about the flight control software. Don't worry about the 1g. Pitch and power, as always. If the nose is going up, and you don't want it to be, push it down.

Just like you did in your last plane- set the pitch and power you want, and it'll go where you want it to go. If the FD is causing a distraction, turn it off and fly.
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Old 18th Feb 2024, 08:49
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The Airbus FBW system will maintain the attitude that you set with the side-stick - the pitch angle and bank angle - but it cannot do that in all turbulence situations, (and there are maximum pitch and bank angle limits that it works within).

In moderate to high turbulence, you will have to correct the attitude to maintain the path you want.

In extreme conditions and deviations you might have to hold full side-stick deflection for a moment to correct the aircraft. But remember, the way with Airbus FBW is to make a correction, then return the side-stick to neutral, correct, neutral, correct, neutral, etc.

In high turbulence, just try to keep the aircraft in approximately the required attitude, don't constantly try to keep the FD centred, just try to correct large deviations. If the turbulence is too severe, you will have to discontinue the approach.
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Old 18th Feb 2024, 09:03
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I would suggest that you stop thinking about what the FBW is doing and just fly the aircraft. The Airbus is trajectory stable, but effectively all this means is that if you're displaced from your original trajectory (eg an updraft) you'll keep flying the same 3 degree slope, but too high. Instinct suggests to me that if you're struggling to follow the flight directors, you might be making inputs that are too large.

Do it right on the Airbus and the flight directors will follow you, not the other way around. Don't forget that you have the ILS available for reference.
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Old 18th Feb 2024, 10:39
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the pf should adjust the attitude to make sure we are on the right slope,but how?after encounter updraft,the system will turn down the pitch automatically to maintain 1G load,the pitch going down,the FDs going down as well, how many push input shoud i use on the stick really confusing me right now if follow the FDs is to large…
Thx
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Old 18th Feb 2024, 12:28
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In manual flight 1g path of the aircraft does not necessarily remain related to GS or any other descent path. If aircraft is on GS and turbulence displaces it, it will follow the new path at 1g. Pilot will have to bring it back to the GS like any other aircraft. The only difference in airbus being after every pitch correction the stick must neutralized otherwise it will keep pitcing in that direction.

Last edited by vilas; 18th Feb 2024 at 14:36.
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Old 18th Feb 2024, 13:16
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If you want to get technical, remember that the Airbus FBW is not maintaining a 1G flight path throughout the entire flight envelope. This only applies to higher than approach speeds.
Below this, the FBW algorithm will blend a pitch hold / G load mode down to a certain speed at which point it will be pitch only.
To put it in simpler terms: the engineers have invested a lot of time to make the aircraft behave naturally so, as others have said, don't overthink it and just make the appropriate inputs gently and see how the a/c reacts.
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Old 19th Feb 2024, 07:16
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Originally Posted by songzheng
the pf should adjust the attitude to make sure we are on the right slope,but how?after encounter updraft,the system will turn down the pitch automatically to maintain 1G load,the pitch going down,the FDs going down as well, how many push input shoud i use on the stick really confusing me right now if follow the FDs is to large…
Thx
Forget about the 1g. Set the nose where you want it, then stop making inputs. When turbulence causes the nose to move, put it back- just like any other plane.
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Old 19th Feb 2024, 07:58
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I believe what the captain is suggesting is for you to alter the pitch (and angle of attack) to minimise the gust induced displacement from the original trajectory.

I would suggest that until you are experienced on the aircraft that you don’t follow this advice for several reasons.

A good place to start is to watch and see how the AP flies in these conditions. When you are PM observe how your colleagues fly in these conditions. If you are manually flying with the flight directors on, make smooth corrections towards the flight directors remembering that the FDs are dynamic and are tuned in anticipation of there being a lag from indication to reaction by the pilot. Smooth, smooth, smooth and no large amplitude inputs unless absolutely necessary.

When I was converting onto the Airbus an instructor gave a very useful demonstration in the simulator of manual flying with extremely rapid corrections to the FD bars at a rate quicker than the FD was able to adjust its command - a stable approach very quickly became high amplitude vertical oscillation. He never flew in an opposite sense to what the FDs commanded yet still managed to make the approach completely unstable. The lesson is that the FDs are only useful when using the correct, smooth flying technique.
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Old 19th Feb 2024, 12:03
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Originally Posted by Check Airman
Forget about the 1g. Set the nose where you want it, then stop making inputs. When turbulence causes the nose to move, put it back- just like any other plane.

That's it. + 1 (but give the FBW a moment to react first).

(where's the Like button?)

It might be helpful for the OP to imagine you are in a small boat on a moderate sea. You keep it pointing in the right general direction but you do not rapidly see-saw the rudder of the boat to prevent every inch of deviation - you just keep gently bringing it back to point in the right direction

If a gust has taken you above the glide-slope, then you will need to pitch down lower than normal to recapture the glide-slope - but I hope that is teaching you to suck eggs !

Last edited by Uplinker; 19th Feb 2024 at 12:21.
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