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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Originally Posted by enzino
(Post 11549972)
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. 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. https://cimg3.ibsrv.net/gimg/pprune....d11925268.jpeg |
Thanks!
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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. |
Originally Posted by Gero
(Post 11550117)
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. |
You need exactly 2 seconds to realise the difference on flight controls page.
Very dangerous indeed. |
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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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. 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. |
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 |
Originally Posted by Check Airman
(Post 11550276)
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. 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. |
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! |
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. |
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? |
Originally Posted by Check Airman
(Post 11550656)
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?
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 |
That's why in gusts the aircraft always returns to the last roll angle (as long as you don't make control inputs). 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? |
Originally Posted by FlightDetent
(Post 11550857)
Except it doesn't. Because the FSC follows a simple rule number 0.01 = uncommanded movements are not permissible.
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: |
Originally Posted by Count of Monte Bisto
(Post 11550222)
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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Originally Posted by Gero
(Post 11550117)
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. |
Originally Posted by vilas
(Post 11552053)
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.
Wonder what Air France SOP's are. They are in the factory's backyard. |
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