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A320 aileron authority in Conf 3 vs Conf Full

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A320 aileron authority in Conf 3 vs Conf Full

Old 2nd Dec 2023, 10:17
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A320 aileron authority in Conf 3 vs Conf Full

A captain told me that in Conf 3 for the same amount of sidestick deflection the pilot commands more roll rate than in Conf Full. This is not written in our FCOM, but investigators found out about this characteristic during an incident investigation. I assumed it was the Lufthansa wing strike in Hamburg some years ago but I can't find incident report.

I've been researching about this since yesterday evening without success. I would appreciate some references.
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Old 2nd Dec 2023, 10:49
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Near-Crash in Hamburg: Investigators Criticize Airbus for Inadequate Pilot Manuals - DER SPIEGEL

Link inside the article.

Incident Airbus A320-211 D-AIQP, (aviation-safety.net)

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Old 2nd Dec 2023, 12:51
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Originally Posted by enzino
A captain told me that in Conf 3 for the same amount of sidestick deflection the pilot commands more roll rate than in Conf Full. This is not written in our FCOM, but investigators found out about this characteristic during an incident investigation. I assumed it was the Lufthansa wing strike in Hamburg some years ago but I can't find incident report.

I've been researching about this since yesterday evening without success. I would appreciate some references.
Hi,

Your captain must be a Pprune reader ;-)

It has been discussed over the last few years over the event of Hong Kong Dragon Airlines A320 in 1994. You can find the full report here.
The link was posted and explained by vilas a few years ago.



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Old 2nd Dec 2023, 13:52
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Thanks!
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Old 2nd Dec 2023, 16:33
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Hi
you dont have to read pprune for that
plan your approach for flaps full.
when on final app before flaps full ask PM to show FltContr page on lower ecam.
disconnect AP.
fly manually and observe flight controls indicators as response to your sidestick movements.
you will see quite a reduction in sensitivity when flaps are at full.
flaps 3 are almost always better in gusty conditions provided good LDA.
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Old 2nd Dec 2023, 16:53
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Originally Posted by Gero
Hi
you dont have to read pprune for that
plan your approach for flaps full.
when on final app before flaps full ask PM to show FltContr page on lower ecam.
disconnect AP.
fly manually and observe flight controls indicators as response to your sidestick movements.
you will see quite a reduction in sensitivity when flaps are at full.
flaps 3 are almost always better in gusty conditions provided good LDA.
It’s definitely a good idea to have 4 eyes looking at the flight controls page while hand flying on final approach 😄
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Old 2nd Dec 2023, 18:25
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You need exactly 2 seconds to realise the difference on flight controls page.
Very dangerous indeed.
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Old 2nd Dec 2023, 21:29
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I have been flying the A320 Series for more than 22 years and am now a reasonably senior training captain in my final year before retirement. PPRuNe is great but you never quite know who is who. There are some very talented and knowledgeable folks here, but also a fair number of people who have spent way more time on Microsoft Flight Sim than is good for them. Go on what the manuals tell you and not Aviation Herald or someone who met a guy, who knew a friend, who definitely had heard from a reliable source that roll rates can be clearly seen on the flight controls page whilst on a visual approach.
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Old 3rd Dec 2023, 01:47
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Interesting graphs included in that document. Thanks. How does this go with what's written in the FCTM though?
CONF FULL provides better handling capability in turbulent conditions, however, CONF 3 provides more energy and less drag.
PR-NP-SP-10-10-3 P 3/4

Wouldn't it seem to be saying that you have better roll control with full flaps?

What exactly does Airbus mean by "handling capability"? To me, the graph and the text are at odds with each other.
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Old 3rd Dec 2023, 11:26
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Just have a look at this document, maybe it clarifies a few things: https://arc.aiaa.org/doi/10.2514/6.1989-3594

The graphs presented in the accident report aren't what the ailerons/spoilers do when you input roll commands to the EFCS. These are (most likely) the "kinematics" blocks presented in the paper (the picture where the overall control loop is shown). You are "flying a control loop".

Simon
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Old 3rd Dec 2023, 13:22
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Originally Posted by Check Airman
Interesting graphs included in that document. Thanks. How does this go with what's written in the FCTM though?
PR-NP-SP-10-10-3 P 3/4

Wouldn't it seem to be saying that you have better roll control with full flaps?

What exactly does Airbus mean by "handling capability"? To me, the graph and the text are at odds with each other.
as Simon described the kinematics do not necessarily describe the input vs output, rather it’s a block inside the flight control loop.

In Conf FULL you will get roll spoiler deflection the moment a roll is ordered, as opposed to Conf 3 where roll spoiler will only extend above a threshold roll order.

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Old 3rd Dec 2023, 17:33
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One reason for the “turbulent conditions” handling difference is to prevent your own overcontrolling inputs. Try flaps 3 and flaps full landings on a multi-sector day sometime when you have a lot of thermals and convective “turbulence” as opposed to shear and gusts / crosswinds. As in try the different configurations in as close to the same weather conditions as possible. Do the same thing on a gusty crosswind day with shear.

Tight roll control and higher energy / less drag in flaps 3 is great in the shear / crosswind.

Less ability to over control is apparent on the day where the air motions are more vertical.

Also the roll rate commanded is always the same for a given stick position. What changes is the “kinematics” which is a fancy way of saying “what deflection does the flight control system START with to try and give you the commanded rate”. That is basically what the Hong Kong charts are discussing.

YMMV!
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Old 3rd Dec 2023, 17:50
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VR-HYU of the incident is MSN 447. From a past where LAF was a thing, etc., today's FCS could be significantly different even on the HW level. (for bystanders, the NEOs exist from around MSN #7000 and the newborns will soon reach unit number 12.000).

If someone said FULL is less responsive and FCTM reads that FULL provides better handling in gusts and turbulence, that's not exclusive to me - quite the contrary. In addition, after all the cases of cases from Bilbao, my bet is Airbus has the books right and software finetuned.

EDIT: hikoushi cross-posted, same thinking. Thank you.
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Old 3rd Dec 2023, 17:54
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Is the “roll order” in those graphs (p110 of the pdf) the sidestick deflection, or the roll rate computed by the FCCs?

If I’m understanding what you guys are saying, these diagrams are just explaining how the roll rate is generated, and not necessarily what the stick/surface relationship is. Is that right?
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Old 3rd Dec 2023, 18:45
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Originally Posted by Check Airman
If I’m understanding what you guys are saying, these diagrams are just explaining how the roll rate is generated, and not necessarily what the stick/surface relationship is. Is that right?
More or less yes. Airbus use a roll rate control law, though that's not what the loop is really controlling:
What you input with the stick is first integrated (rate to angle conversion) and the loop controls the roll angle. That's why in gusts the aircraft always returns to the last roll angle (as long as you don't make control inputs). That's not all: there is also a direct input from stick to the roll angle loop. If you want so a type of Phi pre command. Conversion from dPhi to Phi consequently is realized with a P-I element (in terms of control loop design). There are multiple reasons for the PI combination: Roll angle feedback with Phi>33 (AC returns always to 33 when no input = positive spiral stabillity), a "good feeling" (minimizing PIO risk) for the pilot as the AC directly reacts to stick input and so on....
In the Phi loop you have the coupling between yaw and roll and there a deflection command is generated. This command is fed through the kinematics (which is nothing more than different LUTs for different configuration) and out of them (with rate limiting most likely applied afterwards) you get the commands for the surfaces.

BUT: I have to ask, but I'm pretty sure that there is also a LUT between stick in and stick command used for the law. That's how one could realize a different sensitivity for different configurations.

Simon
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Old 4th Dec 2023, 05:19
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That's why in gusts the aircraft always returns to the last roll angle (as long as you don't make control inputs).
Except it doesn't. Because the FSC follows a simple rule number 0.01 = uncommanded movements are not permissible.

Simon, before you engage any further, answer one question for us, please. Without research or thinking about it at all, just as plain as it sounds, based on your current understanding: In high altitude flight with AP = off and sidesticks released - does the airplane maintain level flight?
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Old 4th Dec 2023, 06:57
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Originally Posted by FlightDetent
Except it doesn't. Because the FSC follows a simple rule number 0.01 = uncommanded movements are not permissible.
To me that doesn't make sense. With this in mind, how could they have implemented the positive stability for higher roll angles, as the aircraft then (uncommanded) returns to 33?

With regards to the level flight question:
Luckily there is a video on the net where a Scandinavian guy already did what you mentioned in a real (not MSFS ) A330:
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Old 4th Dec 2023, 16:40
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Originally Posted by Count of Monte Bisto
I have been flying the A320 Series for more than 22 years and am now a reasonably senior training captain in my final year before retirement. PPRuNe is great but you never quite know who is who. There are some very talented and knowledgeable folks here, but also a fair number of people who have spent way more time on Microsoft Flight Sim than is good for them. Go on what the manuals tell you and not Aviation Herald or someone who met a guy, who knew a friend, who definitely had heard from a reliable source that roll rates can be clearly seen on the flight controls page whilst on a visual approach.
Which of course would be excellent advice if the manufacturers included all of the aircraft's hidden features in the FCOM. Had information that is NOW in the public domain been included in the 737 Max FCOM a number of folks may now still be with us. Over the years much infornation not originally included in the Airbus FCOM has also appeared there as a result of accidents or incidents!
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Old 6th Dec 2023, 00:12
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Originally Posted by Gero
Hi
you dont have to read pprune for that
plan your approach for flaps full.
when on final app before flaps full ask PM to show FltContr page on lower ecam.
disconnect AP.
fly manually and observe flight controls indicators as response to your sidestick movements.
you will see quite a reduction in sensitivity when flaps are at full.
flaps 3 are almost always better in gusty conditions provided good LDA.
No! Flap 3 is very sensitive that's why in gusty conditions flap full is better and that's what the report and FCTM says. Flap3 gives better performance in wind shear due less drag.
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Old 6th Dec 2023, 03:57
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Originally Posted by vilas
No! Flap 3 is very sensitive that's why in gusty conditions flap full is better and that's what the report and FCTM says. Flap3 gives better performance in wind shear due less drag.
Not sure your "thought process" but I always land flaps full. It is what "Airbus designed the plane to do" and I trust Airbus. I grow weary with Captains who "want to save fuel" by using Flaps 3 (but smoke the brakes on landing) etc.

Wonder what Air France SOP's are. They are in the factory's backyard.
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