Airbus Flight Controls Question:
The roll law is a roll rate law.
As per FCOM DSC-27-20-10-30 :
The roll rate requested by the pilot during flight is proportional to the sidestick deflection, with a maximum rate of 15 °/s when the sidestick is at the stop.
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Again the pilots input is integrated so the aircraft behaves the way it's described...
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See https://arc.aiaa.org/doi/10.2514/6.1989-3594 for reference...
See https://arc.aiaa.org/doi/10.2514/6.1989-3594 for reference...
If the pilot is asking for 0 roll rate, the target is zero roll rate. Not a constant bank angle.
At least, what I'm saying is consistent with the in-flight behavior of the plane. You still have to counter the gusts. Less than a conventional aircraft, but you still have to counter them.
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Of course you have to make inputs in gusty conditions, you want the aircraft to stay on the dsired path (especially while maintaining the center line of the runway when landing). The loop isn't closed in this respect. If you enagage a nav lateral ap mode, it would, but not while hand flying.
Hope this clarifies it
That's interesting. However I'm really not sure it would pass the test of reality. I'm really not sure the wings would stay level in gusty conditions. People fight with the stick in order to keep the wings level, not because they notice their flight path going sideways.
It's very surprising. We can't know for sure except if we're in the design office. I'll try to ask some friends in Toulouse.
It's very surprising. We can't know for sure except if we're in the design office. I'll try to ask some friends in Toulouse.
I'm going to bet it's the guy whose name is written on top of it, who did a PhD in fly by wire for helicopters.
I'd love to read it, however I'm not gonna pay 25 bucks for this paper.
I'd be amazed if it was really unnecessary to use the sidestick to maintain a zero bank angle in gusty conditions.
Did you ever try that yourself in flight ?
I'd love to read it, however I'm not gonna pay 25 bucks for this paper.
I'd be amazed if it was really unnecessary to use the sidestick to maintain a zero bank angle in gusty conditions.
Did you ever try that yourself in flight ?
I manage flying without thinking about any computer equations.
I know the FBW, (and auto-thrust* and GS Mini), are there. I know what they do and how they help me, and I know how to operate the side-stick without creating PIOs. Then I just fly the 'plane by feel, observation and experience, and it all works very well.
*older A330 auto-thrust can be 'lazy' near the ground in certain conditions but you simply deal with it.
I know the FBW, (and auto-thrust* and GS Mini), are there. I know what they do and how they help me, and I know how to operate the side-stick without creating PIOs. Then I just fly the 'plane by feel, observation and experience, and it all works very well.
*older A330 auto-thrust can be 'lazy' near the ground in certain conditions but you simply deal with it.
Fair comment. Don't get me wrong; so do I, but not down to such detail as in post #19 etc. On short finals on a gusty day; that is probably over-thinking it, somewhat !
(A lot of pilots do not understand GS Mini, but I made sure I do, and how it helps us, but I don't need to know any equations to understand it, just what it does. )
The OP asks:
I read that as not asking for a realy deep explanation of the computer programming; but more about how the FBW reacts and the relative authority of the FBW and the side-stick, and whether the side-stick inputs cancel the FBW inputs.
From memory, so please correct me; the FBW can command 25° roll rate, the side-stick 15°.
It's a fantastic system though; I absolutely love it
(A lot of pilots do not understand GS Mini, but I made sure I do, and how it helps us, but I don't need to know any equations to understand it, just what it does. )
The OP asks:
.......So your on final, Normal Law, AP off. Wing tips in a gust. Does the FBW flight control system stop the gust induced bank(because you didn't command it)? And does it actually attempt to return to its previous bank? Now you don't wait for all of this. You correct with sidestick. Are you augmenting the flight controls? Or does the plane sense your input and completely give you back full control? In other words...the plane with full sidestick is a 15 degree/sec roll rate. You correct with half sidestick, so what would be the roll rate command if the system is also responding to a gust?
I read that as not asking for a realy deep explanation of the computer programming; but more about how the FBW reacts and the relative authority of the FBW and the side-stick, and whether the side-stick inputs cancel the FBW inputs.
From memory, so please correct me; the FBW can command 25° roll rate, the side-stick 15°.
It's a fantastic system though; I absolutely love it
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“If your stick is neutral, you're asking for 0 roll rate. So the aircraft will damp any roll rate. But the resulting roll won't be corrected.”
how can the system damp the roll rate and matain level,and the next sentence the resulting roll still exist???
how to understand this,in my mind it is no roll rate=no roll=0 bank
thxxxxx
how can the system damp the roll rate and matain level,and the next sentence the resulting roll still exist???
how to understand this,in my mind it is no roll rate=no roll=0 bank
thxxxxx
“If your stick is neutral, you're asking for 0 roll rate. So the aircraft will damp any roll rate. But the resulting roll won't be corrected.”
how can the system damp the roll rate and matain level,and the next sentence the resulting roll still exist???
how to understand this,in my mind it is no roll rate=no roll=0 bank
thxxxxx
how can the system damp the roll rate and matain level,and the next sentence the resulting roll still exist???
how to understand this,in my mind it is no roll rate=no roll=0 bank
thxxxxx
Ok last take on this: I cite (out of the paper I referenced): "The objectives are thus: To have an absolutely neutral spiral mode for a bank attitude lower than 33° ie: with the sidestick in neutral position, the lateral attitude will be frozen in spite of any lateral gusts." later it is discribed that "On the other hand, as far as gusts are concerned, the aircraft will respond with modes p1 and p2. If the aircraft is subjected to lateral gusts, as the stick remains in the zero position, the PHI_C target is therefore unchanged and the control loop will counter the gust to bring the aircraft back to its initial lateral attitude."
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The gust overpowers the airplane's ability to damp to 0 roll rate, so some bank angle develops. After that, the bank stays there because the control law does not respond to bank angle within 33 degrees.
Seems like this is describing the part that brings the bank to 33 degrees if exceeded, and not the general case within 33 degrees.
Seems like this is describing the part that brings the bank to 33 degrees if exceeded, and not the general case within 33 degrees.
think i am confuse the roll between the roll rate,roll=bank (like 7degrees),and the roll rate is a rate(like 2degrees per sec),so encounter the gust,roll/bank rate or bank angel appear,and computer will damp the rate to 0 and prevent more bank be make,thats it, the a/c still hold bank until move the side stick. that right?
thx!