Airbus hand-flying characteristics
Stuck_in_an_ATR, quote:
"I used to criticize this guy's stick handling too. I thought my piloting technique is much better - until I installed a camera in the cockpit..."
Love it...! (English-style modesty will get you nowhere in the dog-eat-dog world of PPRuNe, but I admire your self-deprecation!)
And, as I’ve recently commented on the Airbus FBW thread, the PNF has absolutely no idea what the PF is doing with his stick.
For hikoushi: not only are they not connected, but even looking across is futile. The only viewpoint is from the P3 seat, where I spent a proportion of my years.
"I used to criticize this guy's stick handling too. I thought my piloting technique is much better - until I installed a camera in the cockpit..."
Love it...! (English-style modesty will get you nowhere in the dog-eat-dog world of PPRuNe, but I admire your self-deprecation!)
And, as I’ve recently commented on the Airbus FBW thread, the PNF has absolutely no idea what the PF is doing with his stick.
For hikoushi: not only are they not connected, but even looking across is futile. The only viewpoint is from the P3 seat, where I spent a proportion of my years.
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C*
Below a basic scheme of C* just to get an idea,
In real - pure C* - control is not applied in aviation, gains and filters are added to enhance the control law for certain flight phases.
In real - pure C* - control is not applied in aviation, gains and filters are added to enhance the control law for certain flight phases.
Originally Posted by Chris Scott
So how to fly the Airbus FBW manually?
Based on my limited experience, I can certify everything Chris Scott has written here on the subject of manual Airbus control is sound operational advice.
Mind you, there were two caveats on single-aisle Airbi regarding dual hydraulic system loss. It's been four years since my last flight on the minibus so I cannot remember anymore which was which but in one case you'd be left with elevators only and you had to drop the wheels at exact speed (which was "remembered" as neutral reference by elevators) otherwise approach feels normal but pitch-up at go around would be very hard to contain. The other was loss of one elevator leading to other being reduced to half its travel not to load the tail with too much twist, basically leaving you with just 1/4 of normal elevator authority - sufficient but the aeroplane felt sluggish so landing at airport with minimum crosswind and turbulence was advised.
I'm pretty sure widebodies have different hyd and FC architecture but if among flight patterns in FCOM you find "Approach and landing with xxxxxx inoperative", follow it as precisely as you can, if it is there it is there for a very good reason.
Some good points by both Clan and Chris.
The advice about supporting elbow seems a great thing to do. We also had a "wrist grip", but most folks stowed it and just used the elbow/forearm support. The good thing about supporting the wrist was for smooth inputs, as our stick moved less than 1/8 of an inch ( force versus displacement as in the 'bus).
Back to the "connected sticks/yokes" once again, huh? I must defend the position of some here that it doesn't make a lot of difference. As Clan has said, if the nose ain't going where it's supposed to be going, then the other guy is doing somethin weird or the jet is. Not only were we not be able to see the other stick ( back seat/front seat), but the doggone thing moved so little it would not have helped. If the jet was not going where it was supposed to, we could "add" input. If that didn't help, we could take control with a paddle switch below the handgrip, and I think a similar feature is implemented in the 'bus.
Some good points for a newbie.
The advice about supporting elbow seems a great thing to do. We also had a "wrist grip", but most folks stowed it and just used the elbow/forearm support. The good thing about supporting the wrist was for smooth inputs, as our stick moved less than 1/8 of an inch ( force versus displacement as in the 'bus).
Back to the "connected sticks/yokes" once again, huh? I must defend the position of some here that it doesn't make a lot of difference. As Clan has said, if the nose ain't going where it's supposed to be going, then the other guy is doing somethin weird or the jet is. Not only were we not be able to see the other stick ( back seat/front seat), but the doggone thing moved so little it would not have helped. If the jet was not going where it was supposed to, we could "add" input. If that didn't help, we could take control with a paddle switch below the handgrip, and I think a similar feature is implemented in the 'bus.
Some good points for a newbie.
Last edited by gums; 5th Jan 2013 at 15:17.
Thanks for that, Clandestino, but I've just realised a careless error in my post: re the examples of "long-lasting commands".
I opined that the "landing flare is comparatively brief", which is true in terms of the time taken to rotate the a/c by only about 3 degrees. However, it overlooks the effect of Landing Mode, which - below a certain height (30ft in my FCOM) - requires the PF to deflect the stick progressively backwards: even to maintain a steady pitch-attitude. This feature goes some way to simulate the stick load on landing with traditional controls. Without Landing Mode, it would be easy to over-flare, as all AI FBW pilots know.
Am amending my post.
Gums,
Good to do business with you again, and I take your point on interconnection. The size and position of the stick really doesn't lend itself to either tactile or visual cues - assuming they were boot-strapped manually or electronically. That's not to say it doesn't matter; only that it's probably not practicable in the way it is with old-fashioned yokes. I remain concerned about what seems to be the persistent pot-stirring of some pilots, but you can only observe it from the P3 seat.
I opined that the "landing flare is comparatively brief", which is true in terms of the time taken to rotate the a/c by only about 3 degrees. However, it overlooks the effect of Landing Mode, which - below a certain height (30ft in my FCOM) - requires the PF to deflect the stick progressively backwards: even to maintain a steady pitch-attitude. This feature goes some way to simulate the stick load on landing with traditional controls. Without Landing Mode, it would be easy to over-flare, as all AI FBW pilots know.
Am amending my post.
Gums,
Good to do business with you again, and I take your point on interconnection. The size and position of the stick really doesn't lend itself to either tactile or visual cues - assuming they were boot-strapped manually or electronically. That's not to say it doesn't matter; only that it's probably not practicable in the way it is with old-fashioned yokes. I remain concerned about what seems to be the persistent pot-stirring of some pilots, but you can only observe it from the P3 seat.
Last edited by Chris Scott; 5th Jan 2013 at 15:55.
Salute!
TNX, Chris.
I'll hang around anytime we talk about FBW concepts and implementation, especially after a mishap. And I'll match my starting date in a full FBW operational plane with anyone here. It's my only credential for joining in the robust discussion amongst the august, knowledgeable "heavy" drivers here.
We really need to define "hand flying", as the thread is titled.
I assume it means no auto anything, including the throttles. And for the "conventional" folks here, there's no such thing as "hand flying" a FBW jet as long as there's a computer between you and the control surfaces. The 'bus "direct" mode seems closest, but you still don't get tactile feedback from any of the control surfaces - kinda like flying the old simulators or most military fighters since the late 50's with only hydraulic fluid to the actuators based on your position of the valves the stick controlled. Doze will be quick to point that out, heh heh.
TNX, Chris.
I'll hang around anytime we talk about FBW concepts and implementation, especially after a mishap. And I'll match my starting date in a full FBW operational plane with anyone here. It's my only credential for joining in the robust discussion amongst the august, knowledgeable "heavy" drivers here.
We really need to define "hand flying", as the thread is titled.
I assume it means no auto anything, including the throttles. And for the "conventional" folks here, there's no such thing as "hand flying" a FBW jet as long as there's a computer between you and the control surfaces. The 'bus "direct" mode seems closest, but you still don't get tactile feedback from any of the control surfaces - kinda like flying the old simulators or most military fighters since the late 50's with only hydraulic fluid to the actuators based on your position of the valves the stick controlled. Doze will be quick to point that out, heh heh.
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Originally Posted by gums
As Clan has said, if the nose ain't going where it's supposed to be going, then the other guy is doing something weird OR the jet is.
- The pilot is doing the correct command but the airplane is not following.
- The plane cannot do well as the pilot is obviously not commanding well.
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Originally posted Chris Scott
Love it...! (English-style modesty will get you nowhere in the dog-eat-dog world of PPRuNe, but I admire your self-deprecation!)
Love it...! (English-style modesty will get you nowhere in the dog-eat-dog world of PPRuNe, but I admire your self-deprecation!)
In "stable" flight phases, like climb-out, or approach one can really minimize S-S inputs.
However, when things change fast, eg. the landing flare old habits kick in subconsiously and the sidestick tends to be all over the place, without the pilot even realizing it. Thankfully, the airplane doesn't seem to care either...
@A330Zab
Thanks for the C* diagram. Can you post a link to the original article where you took it from?
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@S_ATR
Sure........linked here, keep in mind it is not Airbus specific. (AFIK airbus don't use the Kff - feedforward - gain in A32/A33/A34).
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Thanks A33Zab! I have something to crunch on for next few days!
Re. feedforward (or lack of in the 'Bus). I noticed the Kff gain on the diagram you posted and wondered what it was for. Is it some kind of "anticipator", to get the elevators moving bedore the "proper" C* signal is generated?
Re. feedforward (or lack of in the 'Bus). I noticed the Kff gain on the diagram you posted and wondered what it was for. Is it some kind of "anticipator", to get the elevators moving bedore the "proper" C* signal is generated?
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Flare mode
I was always wondering, what's the flare mode good for? Why can't the plane just stay in normal law until touchdown or simply go into direct law at some point instead of going into flare mode?
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@S_ATR:
Found this description (Search: FeedForward PID controller) on the net.
In contrast to feedback control, feedforward control acts the moment a disturbance occurs, without having to wait for a deviation in process variable.
This enables a feedforward controller to quickly and directly cancel out the effect of a disturbance.
To do this, a feedforward controller produces its control action based on a measurement of the disturbance.
When used, feedforward control is almost always implemented as an add-on to feedback control.
The feedforward controller takes care of the major disturbance, and the feedback controller takes care of everything else that might cause the process variable to deviate from its set point.
This enables a feedforward controller to quickly and directly cancel out the effect of a disturbance.
To do this, a feedforward controller produces its control action based on a measurement of the disturbance.
When used, feedforward control is almost always implemented as an add-on to feedback control.
The feedforward controller takes care of the major disturbance, and the feedback controller takes care of everything else that might cause the process variable to deviate from its set point.
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The video itself is great; handling of the sidestick poor by both PFs. It's a tribute to the FBW system that stirring the pudding to that extent does not produce PIO.
Last edited by 737Jock; 7th Jan 2013 at 20:03.
flare mode
Guess I didn't read all thru the various laws and such, but found the "flare" mode "upon further review".
Wow! Sucker is basically in "direct" mode with some rate and gee dampening, then requires increasing back stick below 50 feet to maintain or increase pitch. Gotta admit that the mode should make the jet feel just like those of yore.
We didn't have the altitude sensor ( 'bus apparently uses RA), but we had a strong AoA bias with gear down, so you "had to" flare or would just drive onto the rwy at existing pitch attitude.
This should make Lyman and a few others feel all warm, heh heh.
Wow! Sucker is basically in "direct" mode with some rate and gee dampening, then requires increasing back stick below 50 feet to maintain or increase pitch. Gotta admit that the mode should make the jet feel just like those of yore.
We didn't have the altitude sensor ( 'bus apparently uses RA), but we had a strong AoA bias with gear down, so you "had to" flare or would just drive onto the rwy at existing pitch attitude.
This should make Lyman and a few others feel all warm, heh heh.
Dog Tired
I was always wondering, what's the flare mode good for? Why can't the plane just stay in normal law until touchdown or simply go into direct law at some point instead of going into flare mode?
'Flare mode' applies a little nose-down pitch (which the pilot needs to correct) to make it all feel normal.
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Chris Scott,
Thank you for your critique. My point related to the French FMS was that pilots who have made the transition from Boeing to Airbus have TOLD ME that, in many cases, they found the FMS switch/logic confusing. You were not privy to those conversations. Understood? Your opinion might differ from the 5-10 Airbus pilots who have transitioned from Boeing aircraft that I have talked to.
Additionally, I did not provide the "SAIL" Airbus cockpit video as an instructional video. Instead, I, and many others, find it entertaining and interesting - especially for those of us who use traditional yokes. The main pilot in the video clearly does not care about "proper form." And that's fine because the video (especially the descending left turn approach into Rio's Santos Dumont airport) was entertaining.
Cheers
Thank you for your critique. My point related to the French FMS was that pilots who have made the transition from Boeing to Airbus have TOLD ME that, in many cases, they found the FMS switch/logic confusing. You were not privy to those conversations. Understood? Your opinion might differ from the 5-10 Airbus pilots who have transitioned from Boeing aircraft that I have talked to.
Additionally, I did not provide the "SAIL" Airbus cockpit video as an instructional video. Instead, I, and many others, find it entertaining and interesting - especially for those of us who use traditional yokes. The main pilot in the video clearly does not care about "proper form." And that's fine because the video (especially the descending left turn approach into Rio's Santos Dumont airport) was entertaining.
Cheers
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My post was genuine. After watching the aforementioned video I have even made a rant on a different forum about proper 'Bus flying technique, "making mayonnaise" vs "touching your best friend's @##*" etc. Then I really put a GoPro camera behind the seat and made some interesting observations...
Despite what I like to think, the Airbus rides turbulence fairly well on approach and I've adopted a much more "hands off" attitude to flying it, preferring to make just one or two corrections to correct trends in the trajectory instead of stirring porridge the whole way down.
One thing you can do, however, is try to make the inputs smooth. It's not immediately obvious at the front but when someone is putting in rapid "squirts" (even small amplitude) it's very pronounced in the cabin and accentuates motion sickness. In calm conditions the Airbus can be flown with "pressure" on the sidestick only.
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My personal advise as to how to control the sidestick is that you have to be conscious that you are trimming the airplane whrn you release it to neutral. So, when you are reaching your desired pitch and performance, progressively release it until,you reach zero SS angle exactly at the desired performance.
In final approach, to avoid overuse of the sidestick you have to give a second to the system to counteract lateral gusts itself, then bank to regain loc or runway extended centerline. So it is like this: lateral gust that rolls your wings. Let the system zero the roll rate, then use the sidestick to go back to the desired bank angle to keep or regain the loc. If you act simultaneously with thw system you will begin the pudding thing. Just wait a second then make your input. With pitch is similar but not exactly the same. You have more things affecting, gusts, updrafts, downdrafts, a/thr... You may need to act preemptively
For the flare, I don't recommend the widespread use of repetitive pull- release-pull- release that I have observed many times. I favour a single pull, that you can modulate as required. Ah, and never use the flare pitch bar for landing. That's gross!
In final approach, to avoid overuse of the sidestick you have to give a second to the system to counteract lateral gusts itself, then bank to regain loc or runway extended centerline. So it is like this: lateral gust that rolls your wings. Let the system zero the roll rate, then use the sidestick to go back to the desired bank angle to keep or regain the loc. If you act simultaneously with thw system you will begin the pudding thing. Just wait a second then make your input. With pitch is similar but not exactly the same. You have more things affecting, gusts, updrafts, downdrafts, a/thr... You may need to act preemptively
For the flare, I don't recommend the widespread use of repetitive pull- release-pull- release that I have observed many times. I favour a single pull, that you can modulate as required. Ah, and never use the flare pitch bar for landing. That's gross!
Finally..... and attaboys
I have finally been rewarded by Fursty and Micro.
Their techniques and observations have answered many of my questions and confirmed my suspicions.
Either of them would adapt to the Viper stick/control laws in about 4 seconds.
The plane's stability when in turbulence became very obvious to us after a mission or two. Our little jet weighed less at takeoff then the weight of the fuel in the 'bus, heh heh. Nevertheless, the reaction by the jet to keep roll rate and trimmed gee per the laws made the thing feel like a much larger/heavier plane in light to moderate turbulence or when zipping along at 540 knots and 200 feet over a desert with all those thermals. So the techniques described and the aircraft's reactions fit my experience perfectly. Same-o, same-o. Control surfaces were constantly moving to achieve the trimmed/commanded gee or roll rate.
Same for the flare technique. Never reverse the stick beyond neutral unless a severe gust, just don't pull as much or maybe relax back stick ever so slightly, but one long, gentle backstick input until the wheels squeak. If you ain't holding a slight back stick at touchdown, you'll probable bounce.
So I finally got to hear how that sucker flies when you are not letting Otto do everything. Attaboy. And thanks, guys.
Their techniques and observations have answered many of my questions and confirmed my suspicions.
Either of them would adapt to the Viper stick/control laws in about 4 seconds.
The plane's stability when in turbulence became very obvious to us after a mission or two. Our little jet weighed less at takeoff then the weight of the fuel in the 'bus, heh heh. Nevertheless, the reaction by the jet to keep roll rate and trimmed gee per the laws made the thing feel like a much larger/heavier plane in light to moderate turbulence or when zipping along at 540 knots and 200 feet over a desert with all those thermals. So the techniques described and the aircraft's reactions fit my experience perfectly. Same-o, same-o. Control surfaces were constantly moving to achieve the trimmed/commanded gee or roll rate.
Same for the flare technique. Never reverse the stick beyond neutral unless a severe gust, just don't pull as much or maybe relax back stick ever so slightly, but one long, gentle backstick input until the wheels squeak. If you ain't holding a slight back stick at touchdown, you'll probable bounce.
So I finally got to hear how that sucker flies when you are not letting Otto do everything. Attaboy. And thanks, guys.
Last edited by gums; 9th Jan 2013 at 16:46.
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Guess I didn't read all thru the various laws and such, but found the "flare" mode "upon further review".
Wow! Sucker is basically in "direct" mode with some rate and gee dampening, then requires increasing back stick below 50 feet to maintain or increase pitch. Gotta admit that the mode should make the jet feel just like those of yore.
Wow! Sucker is basically in "direct" mode with some rate and gee dampening, then requires increasing back stick below 50 feet to maintain or increase pitch. Gotta admit that the mode should make the jet feel just like those of yore.
Very glad it's clicked for you though!
Last edited by DozyWannabe; 9th Jan 2013 at 21:59.