Full sidetick 320 in gusts

[Speedwinner]

hello airbus pilots,

i have a quick question. i flew recently an ils approach in gusty conditions, so in 2000ft agl nearly 50kts with a very high gust rate. So i disconnected the ap and athr and flew at 2000agl manual, fd on. coming from th3 737 ng i realised 2 things:

one or two times i had a full stick deflection which i felt was necessary in the bank. is that a normal experience in gusty winds? In my 737 i never had a full deflection.

second thing was the fd. seemed sometimes to jump aside, so very quick and not smooth

landing was fine, i love the bus in crosswind conditions near the ground.


how do handle that, let the ap do the job till minima? i dont wanna take the fun out but seems the best to be right?

cheers!

[Stuck_in_an_ATR]

Have a look at Airbus FCB024-AIRCRAFT HANDLING IN FINAL APPROACH.


Regarding full sidestick deflections, Mr. Airbus says therein:

The sidestick's ergonomical design is such that the stop at full deflection is easily reached. This may give the pilot the impression that the aircraft is limited in roll authority, because there is a time delay before the pilot feels the result of his/her action. On conventional aircraft, due to the control wheel inertia, the pilot needs considerably more time to reach the flight control stop.

So I guess bumping the stops is bound to happen from time to time by design...

[Slasher]

A320 gamestick lateral input is a roll rate demand not a control surface demand. Hence its easy to have
full stick deflection sometimes in very heavy gust situations - even though these would vary rarely need
it. You'd find in Direct Law your control inputs would be like the 737 - albeit rather more sensitive. Try it
in the sim next recurrent but don't overcontrol by trying to follow the FD. Turning it off helps a lot - the
bird is much more useful.

[rudderrudderrat]

Hi Speedwinner,

I agree with the previous, especially Slasher's comment lateral input is a roll rate demand Sometimes in gusty conditions, a small side stick input may command full ailerons in an attempt to give you the requested roll rate. Any more side stick will have no effect - giving the impression that it is not responding - hence a tendency to over control and hit the stops. Try and keep the roll rate selections small and let the FBW computers decide how much aileron you need.

[fullforward]

I know what you're talking about: when I had to transition from B777 to A320 I found that an horrible shortcoming. As a matter of fact, one of the worst things to get used on the Bus.
It won't kill you, but it's scaring and will sometime prompt 'dual input' from your fellow - remember that LH go around on windy cond in Hamburg couple of years ago.
Fortunately, I'm back and happy on the triple.:ok:

[Bula]

Your playing with it :) remember to treat it like another persons whatsit and you will find you don't need to touch the thing.


Btw... Roll rate

[Uplinker]

In very windy conditions you may well have to hold the sidestick against a left or right stop for a couple of seconds before anything seems to happen. However, remember that there are always two of you flying an Airbus - even with the A/P out - you and the flight control system. Even in manual; the aircraft will already be recovering the roll - maybe already using max control deflection - so your input may have no extra effect for a while until the gust subsides. The aircraft will be recovering as 'fast' as it can in the circumstances - but not overstressing the airframe in the process.

It is a very different technique to using the traditional mechanical yoke, but I find that once you understand the concept that in manual control you are effectively guiding an autopilot all the time, it becomes easier to get the hang of.

I think of it like this: The autopilot disconnect in an Airbus changes where the autopilot gets its navigation commands from. With 'Autopilot in' the navigation commands come from the FMGS/FCU. With 'Autopilot out' the navigation commands come from you and your sidestick, but the flight control system is still helping to fly the plane.

Took me a while to work this out - and of course; no-one ever tells you. :rolleyes:

[TyroPicard]

No-one tells you because it does not work like that..... The AP commands, or the side stick commands, talk directly to SEC and ELAC.... they move the surfaces.

[USMCProbe]

Uplinker

+1

In any normal aircraft, you have three potential inputs (Capt, FO, AP) that move 2 interconnected control yolks.

On an AB, you have the same three, two of which move only their own sidesticks, and one acting in the blind. Actually all three are acting in the blind as you can't see what the other pilot is doing unless you take your eyes off the runway ahead of you.

On AB with the AP off, actually the AP is still on, in mode called attitude hold or control stick steering in other aircraft. Where ever the aircraft is pointed in pitch and roll, the aircraft tries to maintain those positions. If a gust hits you and tries to roll the aircraft, the flight control computers put roll input to try to maintain your angle of bank. Unfortunately AB decided not to communicate this to you. If you input roll command as well, the aircraft might already be at the control stops, hence, no reaction from the aircraft.

The same with your flying partner. If the aircraft hits a roll gust, he will input roll command to the stick, and you can't see it either. Hence the "dual input", and/or "priority left".

AB does great in gusty conditions, you just have to get used to it.

[Uplinker]

Er, Tyro and USMC, if you re-read my post carefully and take note of the punctuation, use of italics and words I used (such as "effectively", and "I think of it like this...."); I think you'll find that's exactly what I was saying! :ok:

However, I have changed a word to hopefully make it clearer.

Tyro misses out the accelerometer feedbacks, which send commands to the flight control computers to keep the aircraft on the path you or the FMGS commanded. This is the part of the system that is always flying the plane with you, and is how the aircraft will try to correct for gusts etc. even when the autopilot is disconnected.

[USMCProbe]

Uplinker.

+1 meant I agree 100 percent with what you said. I just added how it is different than other aircraft.

[Uplinker]

Ah, sorry USMC - I'm not up with the internet lingo !

My apologies. :O

[Microburst2002]

On AB with the AP off, actually the AP is still on, in mode called attitude hold or control stick steering in other aircraft. Where ever the aircraft is pointed in pitch and roll, the aircraft tries to maintain those positions.

Sorry marine, but that is rubbish. Are you type rated in the 320??

If a gust hits you and tries to roll the aircraft, the flight control computers put roll input to try to maintain your angle of bank. Unfortunately AB decided not to communicate this to you

Not correct, but somehow you are right, here, in a sense, in that Airbus says some nonsense about its behaviour in lateral gusts. they just don't explain well

SPEEDWINTER
try this the next time, which is in my opinion better explained than any airbus text: allow a sec to the FCS to counter the gust. Wait just a moment before you make an input in the opposite direction of the roll. The roll will be arrested, or almost, by the ELAC, then you make your input. Easy. If you don't, you will be like mixing mayonnaise.

Airbus says that the airplane can rolll at a 15º per sec rate and blabla, but it cannot avoid bank angle from changing. Actually that would be weird. But it resists. Just let it do the job, or most of it, then do your input. Otherwise your input and the FCS' will be simultaneous and added to each other and here we go mayonnaise...

and that is the secret. Like an augmented lateral stability. Try this and give me feedback if you have gusts one of these days

[Speedwinner]

I will! Thanks!

[stilton]

How is this system an advance ?


Setting aside the non connected sticks, unbackdriven autothrottles and hard limits for a minute..


Seriously, you would think a sidestick control system would / could be very responsive, instead the FBW filtering effectively seems to provide a sluggish, unpredictable response.


Full deflection in a Boeing is almost unthinkable, but more importantly, what you input is what you get, predictable and no second guessing, every time.

[Microburst2002]

The blue angels see no problem with it

[Uplinker]

What is interesting is that several people have described exactly what the Airbus FBW system does, then others come on and say that's rubbish and go on to describe what they think it does.....and their description amounts to the same but with different words!

All that is being argued here is terminology: I say that even with AP out "it's like the AP is still in...but the Navigation commands are coming from different places". Others say no that's rubbish with the AP out the ELAC is still helping, but people: the principle is the same.

For example:
Quote:



On AB with the AP off, actually the AP is still on, in mode called attitude hold or control stick steering in other aircraft. Where ever the aircraft is pointed in pitch and roll, the aircraft tries to maintain those positions.

Sorry marine, but that is rubbish. Are you type rated in the 320??


...is not really rubbish is it? Read it again carefully, Micro, I think it describes what the FBW does very well.


Silton, This is what myself and others are trying to get across. The Airbus FBW system is different to conventional mechanical flight controls. It flies differently - like the autopilot is always in. Yes; a Tornado, for example, has a very responsive FBW system, because it is a fighter jet and may need to execute escape or kill manoeuvers at high 'G'. A passenger jet does not want a fighter like response, it is "sluggish" partly for passenger comfort, and partly never to exceed it's design limit of 2.5G. With mechanical controls, one could overstress the aircraft by commanding full deflection. With the Airbus the FBW will not allow the airframe to be overstressed*, and it will try to maintain whatever attitude you last commanded. This needs a different technique when handflying the FBW Airbus. BUT it's something that no trainer has ever taught (me), I've only ever been told "hold the sidestick only on the top/only on the bottom/don't touch it etc etc, which are completely unhelpful. I've seen senior Captains overcontrolling and getting into PIO's because they too do not understand how the FBW works, and have never had it explained to them. Understanding what the FBW is doing helps one to handfly the aircraft much better.


*PS: Before I get shot down again; most Airbus rudders are mechanically linked to the rudder pedals. Therefore it is possible to overstress the rudder.

[stilton]

Question:


On a FBW airbus with the autopilot engaged do either or both of the control sticks move in conjunction with autopilot commands ?

[Slasher]

Fortunately, I'm back and happy on the triple.

Lucky bugger! :(


remember to treat it like another persons whatsit

Wha?...you mean give it a bloody swift kick while screaming to get out of my sight?

Not exactly Airbus procedure! :\


Stilt - nope. Scary huh.

[USMCProbe]

Attitude hold and control stick steering are not techniques that airbus is using, but the name given to AP on other aircraft that accomplish the same thing.

Take you hand off the stick, feet on the floor. What are you commanding on the 320? No input? No, you are commanding 0 pitch rate, 0 roll rate, and 0 yaw rate. Any external forces (wind) that provide something other than zero, the FBW system will try to counteract. But, if the aircraft ends up in a 10 deg bank, the FBW does not roll the aircraft back to zero. In smooth air, it effectively holds whatever pitch and roll angle that you set.

Side sticks not connected. No problem if your flying partner has 8K hours. Sometimes a problem with low time pilots. If both sticks are moved at the same time you get a "dual input" oral warning, but the command of both sticks are "added" together. Both sticks have a little red button that locks out the other stick. Two uses for the button. If a stick is defective and puts in a bad input, you can take priority ("Priority left") and takeover. Hold the button for 42 seconds and the other stick is locked out for the remainder of the flight.

I wish the sticks were connected, I wish the throttles moved, and I wish Boeing could put a table in the cockpit so I don't have to eat on my thighs

[Microburst2002]

I'm positive airbus manuals fail to make people understand how to handle the stick because way too many airbus pilots mix mayonnaise in gusty winds.

It is simple: wait a moment, let the computer (FCS, not AP, not CWS) to stop the bank angle excursion, then make your input. Airbus texts make people believe that the system will keep ILS till touchdown if you leave the sidestick neutral...

Uplinker

Are you airbus fbw type rated? That is not what the FCS system does...

Airbus fbw airplanes just have a different kind of stability, that's all. They are path stable rather than speed stable. To achieve that you need a feedback loop, much like that of an AP, there is no other way. But handling the sidestick has nothing to do with a CWS system.

In a conventional cessna there are two inputs, as well: airplane stability characteristics and pilot inputs. In the bus these characteristics are different, and heavily affected by the FCS, yes. Same applies to the 777. But it is in no way like an AP or a CWS, and airbus pilots must have very clear the difference between pitch, pitch rate, g load, bank angle and roll rate among others.

A good airline pilot has to know very well his AFS, and also his FCS. Many are rluctant to do thhe latter in airbus because it is "weird" or something. Then they don't trust the airplane which leads them to hate it (cos Yoda was right, fear brings hate, and then you have a lot of airbus pilots in the dark side)

[Uplinker]

Stilton; no, the sidesticks do not move together.

At the risk of thread creep; I personally think that is a design flaw and I think they should move together. If the other pilot has his/her tray table out, you cannot see their sidestick, or what inputs they are making.

Neither does the aircraft autopilot or A/THR backdrive the sidesticks or the thrust levers. I personally am not bothered about the static thrust levers, because my normal flying scan includes the engine instruments. I have been flying the Airbus FBW for many years now, and so I am not bothered about not seeing the other pilots sidestick inputs, because I know how the aircaft is going to react and I can tell if the other pilot is doing something wrong. However, if I was a training Captain or a brand new trainee then I am sure that I would prefer to see the opposite sidestick inputs, or feel them copied on my side. And when I was a trainee, I think I would have got the hang of flying the Airbus FBW much quicker if I could have "followed through" on the controls.

Micro; Yes I am, thanks. The problem here, as I have said, is with terminology. My previous answers are not necessarily accurate in terms of exactly which black box is doing what, or what you want to call it, but are trying to convey what flying the FBW is like for those who have not experienced it or are trying to learn.

NO: the Airbus FBW will NOT hold the exact attitude you left it at, but it will TRY. NO; it will not hold an ILS unless the autopilot is flying it - but I never said it would.

[Agaricus bisporus]

I think the CWS remarks come from a description I was certainly given on the conversion to the "Other Side" which described the manual controls as acting much like CWS on the Boeing, ie you select an attitude with the sidestick and the system holds that until you make another selection. It is a good way of describing what the system does, but bears little resemblance as to how it does it. That's my guess at where this idea has crept in.

As to handling in turbulence I too was surprised at how easy it is to reach the limit on stick deflection (so far only in roll) but as the aircraft clearly remains in control if not - according to one classic definition - under control it seems a relatively normal regime of flight. I thoroughly endorse Micro's remarks about making mayonnaise - ALL the turbulence handling difficulties I've observed in my FOs have been due to gross overcontrolling, whipping the stick around like its a Pitts. All this does is to destabilise the aeroplane and make it more skittish and thus harder to fly. The trick in my opinion - just like then737 - is to consciously slow down control inputs and increase their amplitude, ie bigger and slower movements. This can be surprisingly exaggerated (think stirring treacle instead of whipping mayo) and always results in a more responsive and easier to control flightpath. The idea - I think - is largely to ignore the wiggles and bumps - they tend to self cancel - and just fly out the bigger slower excursions with proportionally bigger, slower inputs. It works for me. The more you let the Airbus fly itself the better it seems to respond which is of course exactly the design philosophy.
Personally in extreme turbulence I'd take the Boing every time but I don't think there's much in it. The Airbus flies just fine in turbulence if you use the right technique and remember it is a big, inertia heavy airliner not a Pitts or F16 and treat it as such.

[USMCProbe]

The best advice I was given, was also the first advice I was given. It is an airplane, just fly it like an airplane and don't worry about the FBW.

The number of times I "notice" that the airplane is not reacting quite like I wanted it to is extremely small. Maybe once or twice a year and only in moderate turbulence. And it is only because the FBW is faster than I am, and is already deflecting the control surfaces in the way they need to be deflected. I just got clued in a fraction of a second later.

[Slasher]

I recall I tended to over-control the side stick during the first two sim sessions of my initial
endorsement. The advice I got was "Stop handling it like a virgin with her first c0ck!"

[Microburst2002]

Yes, it is like PIOs in other airplanes. In the bus maybe we can't term them as PIOs, everything regarding stability and control is non conventional in the bus, but they are very similar, and so is the solution to them.

Sorry for blasting you about the CWS thing, but I hate that concept. I much prefer the special stability point of view.

My idea is that the system stability stops the deviation at some point, and after that, we put the airplane back on its due position. The stick should be neutral or close to neutral most of the time, with occasional or frequent small inputs. No need for full stick. If the gust Induces a large roll rate, the system can and will coup with it very well without our help. After that ther is no need for full stick, just enough to gently put wings level.

I used to do the full stick thing often in the beginnin, as soon as I noticed each gust, and sometimes I managed to keep wings very level, but when the gust frequency increased, then I made the finest mayonnaise...

[stilton]

Amazing that you have to second guess what it's going to do.


Like I said, not an advance, Airbi would be better suited as drones..

[Microburst2002]

B777 and 787 are not airbi, and they also have closed loop electronic flight control control laws

[Uplinker]

I think most of us on this thread are in agreement with each other, but have different ways of trying to express it.

Stilton, you need to fly an Airbus FBW before making such comments. Once you have experience on it, a FBW Airbus is very easy to fly - it just needs a different technique, and an appreciation of what the FBW system is doing for you. This is something that is very poorly trained, in my experience - like most of us I was just told treat the sidestick as a dockers c**k and all those sort of comments, which are extremely unhelpful and give you no information to help you fly it properly.

Here's how I fly it: I let the FBW do the flying, and, if it's not coupled to any Nav source, (FCU,FMGS,ILS), then every so often, if the atmosphere has disturbed the flight path; I gently nudge it back to where I want it to go. I hold the side stick properly and make a series of short duration, short travel 'nudges' and back to neutral each time and look at the result. I don't hold a deflection until the attitude is where I want it because then it will over shoot and I will have to bring it back = PIO. I make a 'nudge' in the direction I want and back to neutral and see what the result is. If it was not enough, I make another 'nudge', etc. If I am flying straight and level and then I want to change the attitude by a greater amount, such as a roll into a turn, I hold the stick at maybe half deflection and release it to neutral as the aircraft approaches the attitude I want, then correct if necessary by small nudges.

Effectively what you are telling the FBW is where to hold the attitude. If it is holding a roll attitude a bit too far right, then nudge left a couple of times to 'step' the attitude across to where you want it. The FBW will reset it's 'datum' and then hold the new attitude, until a strong gust or you move it again. If you are flying through very strong turbulence, don't worry if you need to put in full deflections - you won't break anything - but only hold full deflection for a few seconds* and then go back to neutral. If you find yourself making constant inputs and alternately going from one deflection to it's opposite sense, then you are fighting the FBW. Let it do most of the work and just concentrate on guiding it.

It may still sound weird, but it is much easier to experience than explain.

* NOTE: for Windshear or GPWS - hold the stick back until clear.

[Microburst2002]

In normal law, in roll, the 777 behaves pretty much like the 320, not having flown it... In a conventional airplane you might have to keep some aileron to maintain zero roll rate, depending on several effects, if you are climbing or descending, etc... FBW eliminates that and will tend to keep roll rate zero with neutral stick or yoke.

I regard the airbus as a "trimless" airplane, rather than an autotrim airplane. The reason being that the sidestick has no speed related feeling (it doesn't have to, since it is a path stable system and not speed stable). In the bus, we trim the airplane when we release the stick at the desired flight path. Even when the THS is jammed or unavailable we can still trim the airplane, with the sidestick, when in alternate law. Same applies to roll. It is like a roll autotrim. No need to keep stick deflection to maintain zero roll rate. Release to neutral and that is it.

In very nice to fly conventional airplanes, the pilot will only "intervene" with occasional slight push or pull forces in the stick, if the airplane is properly trimmed. input, trim, relax, slight deviation, small input, retrim if needed, etc... in both pitch and roll. In a not so nice to fly one you have to constantly make inputs, the airplane never seems to be in trim for longer than a few seconds. The airbus, and the 777 and 787 behave like the very nice to fly one.