LH A320 Rough Landing @ Hamburg
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Originally Posted by PBL
The ELAC gets signals from roll-rate sensors somehow and if the stick is neutral it signals the control-surface actuators to counter the roll. How else is decoupling supposed to work?
A 'true' or 'real' yaw-roll decoupling would mean to me a 'model based controller', i.e. A controller which incorporates a numeric model of the aircraft flight mechanics characteristics. That means the controller 'knows' in advance how the A/C 'will' react to a certain rudder deflection and thus commands the appropriate amount of aileron deflection 'simultaneously' and 'instantly' to fully compress the yaw-roll coupling induced roll. Depending on the actual implementation and the actuator rate capacity you wouldn't see any roll then.
But your statement fully complies with my understanding of what actually happens and what I call 'yaw-roll decoupling through the back door'.
This 'version' of yaw-roll coupling is a 'side-effect' of the ELAC roll stabilization. When you deflect the rudder, the A/C will show a yaw-roll coupling induced roll. As you say, the controller records a 'roll rate' with the stick being 'neutral' and thus sees this as an 'uncommanded roll' being a case for the 'roll-stabilization' and accordingly will try to counter that roll.
But this implies already the significant difference: The 'roll-stabilization' of the ELAC does not know what the uncommanded roll is caused by, may it be a rudder deflection or a gust, it just sees it as an 'external' disturbance', as a 'nominal-actual value' discrepancy. And it can only 'react' to such a disturbance. There has to be already some amount of nominal-actual value error, i.e a certain roll angle has already to have passed, before the roll-stabilization takes action.
And the action (amplitude and rate) taken, as in any control loop, will depend on the time constants of the implemented control law, gain factors etc.
.......many words....bottom line: this version of 'yaw roll' decoupling is a 'reactive' system being 'relatively' slow and limited. The reaction will need a finite amount of time. It will not be able to counter a sudden, strong and persistent roll moment as during decrab sufficiently in the available time.
And I guess, this may not even be expected from this system, as it may primarily be designed for 'roll stabilization' during cruise and standard turns and thus may act more 'harmonic' and not overly 'dramatic'...
Thus to compress the yaw-roll coupling induced roll during such a massive rudder deflection as during the decrab-manoeuvre seen here, a aileron input by the crew is necessary and has, at least in my judgement, not taken place sufficiently.
Originally Posted by PBL
I wasn't talking about drift. I was talking about the wing lifting and what caused it. That is what let to the strike.
Regards, ihg
Last edited by ihg; 8th Mar 2008 at 13:13.
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A320 ELAC Bank Angle Stabilisation
Please only answer to this if you are sufficiently qualified, i. e. have the technical/engineering background and/or documentation to prove your answer.
I am still uncertain about the bank angle stabilisation algorithms.
Say, a gust starts rolling the aircraft to the left (with stick neutral), would the FBW system (read in this case: ELAC)
- dampen the roll until the commanded roll rate (i. e. 0 degrees/s) is achieved again, leaving the bank angle wherever it ends up
or
- try to restore the bank angle that was present when the (uncommanded) roll started, by rolling to the right?
My current understanding is that, as the FCOM and other docs say, it really only controls roll-rate, and not at all actual bank angle. (With the exception that it will reduce the bank angle to 33 degrees, if that value is exceeded, with stick neutral.)
This would still leave a residual bank angle from the yaw-roll-coupling induced roll, and would require a stick input to level the wings again.
This also means that any deviation from the desired bank-angle has to be corrected by the PF, although to a lesser degree than in a conventionally-controlled aircraft, because he/she does not have to "fight" the cause of the roll in addition to achieving the desired roll rate.
The phrase from FCOM Bulletin 54/2 "the fly-by-wire system counteracts the effects of gust, even with the sidestsick in the neutral position" is sufficiently vague, and may mean either control law (restoring bank angle, or restoring commanded roll-rate).
Always trying to learn,
Bernd
I am still uncertain about the bank angle stabilisation algorithms.
Say, a gust starts rolling the aircraft to the left (with stick neutral), would the FBW system (read in this case: ELAC)
- dampen the roll until the commanded roll rate (i. e. 0 degrees/s) is achieved again, leaving the bank angle wherever it ends up
or
- try to restore the bank angle that was present when the (uncommanded) roll started, by rolling to the right?
My current understanding is that, as the FCOM and other docs say, it really only controls roll-rate, and not at all actual bank angle. (With the exception that it will reduce the bank angle to 33 degrees, if that value is exceeded, with stick neutral.)
This would still leave a residual bank angle from the yaw-roll-coupling induced roll, and would require a stick input to level the wings again.
This also means that any deviation from the desired bank-angle has to be corrected by the PF, although to a lesser degree than in a conventionally-controlled aircraft, because he/she does not have to "fight" the cause of the roll in addition to achieving the desired roll rate.
The phrase from FCOM Bulletin 54/2 "the fly-by-wire system counteracts the effects of gust, even with the sidestsick in the neutral position" is sufficiently vague, and may mean either control law (restoring bank angle, or restoring commanded roll-rate).
Always trying to learn,
Bernd
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They screwed up
I am not and never have been an airline pilot, though I have on occasion been at the controls of a passenger/freight aircraft. There are published xwind limits for virtually every aircraft, and if you continue an approach knowing that the wind is outside limits, then you are taking a risk. Do this in a single-seater and you are generally endangering yourself only (though perhaps others if it goes really pear-shaped). Similar situation in a military 2-seater, though most of us would allow the GIB to have a veto. But in a civilian airliner with fare-paying passengers?? In my view the captain was justified in allowing his fo to conduct the approach, but made a gross error of judgement bordering on negligence not to order a GA when it was clear (as the YouTube video clearly demonstrates) that the situation was deteriorating. Had the aircraft drifted further downwind before the wing strike occurred, tbe results would have been disastrous.
I have been flying aircraft for some 45 years and have made my fair share of cock-ups. The last mistake I made in the air (yesterday?) will, regrettably, not be my last. However, if I was upwind (in the chain of command) of this Lufthansa captain, I would suspend him wie and return him to line operations only after a thorough review of his decision-making abilities.
I have been flying aircraft for some 45 years and have made my fair share of cock-ups. The last mistake I made in the air (yesterday?) will, regrettably, not be my last. However, if I was upwind (in the chain of command) of this Lufthansa captain, I would suspend him wie and return him to line operations only after a thorough review of his decision-making abilities.
Quote from fireflybob [Mar07/15:09 currently #402]:
I don't like the phrase "kicking" off the drift.
[Unquote]
Mea culpa, on at least one occasion. I agree a snap-movement is inappropriate for any large aeroplane. [As you do it with your foot, could we call it a slow kick?] Don't take too long de-crabbing; it's a time of vulnerability to gust, and you would have to start the process even before the comparatively small flare that is advisable on a crosswind landing. This is difficult to get right, and may lead to the necessity of adopting the FULL sideslip configuration, with (as previously agreed) risk of wing-tip contact.
[Interestingly, the DC10-30 Autoland used to start the de-crab at about 130ft, because of the fairly long body; but I don't think we used it in strong crosswinds.]
Hi, Clandestino [Mar07/14:37, #398],
You have raised some interesting points, and you are in current practice, apparently, to try them out (unlike me). Is "17G29" your highest so far? Keep working on it, and have fun.
It is refreshing to receive support for my contention that the A320 family is not particularly difficult (or different) in crosswinds. Me Myself [Mar07/15:17, #403] evidently agrees.
Not sure about releasing the rudder suddenly on take-off rotation, though. Exactly when would you do it? My first reaction is that it sounds more like a simulator pilot's technique than an airline pilot's. Perhaps you can persuade me otherwise?
I would rather stick with the smooth method of pre-empting wing lift with a little into wind aileron. The pilot should already have been applying this throughout the take-off run. Remember that the FBW has been in Roll-Direct Law for the take-off, so has been no different from a conventional aeroplane.
Thanks, XPMorten [Mar07/14:55, #400], for the Airbus Training-Manual extract. I don't think it is really practicable to avoid using large and/or rapid rudder inputs in a strong, gusty crosswind. So I would take their advice and use pre-emptive aileron, as I have been advocating in all my posts.
"If it had been a gust, the aircraft would have crashed."
[Unquote]
I think in the absence of the data (that, no doubt, LH and the pilots have been scrutinising), we cannot be certain. My money, though, would be on a gust. Have not analysed the footage as painstakingly as you have, but the roll-rate seems to increase quite suddenly half way through de-crab, at about the time the A/C leaves the ground in bounce. prior to that, I can see negative and positive gusts at around 50ft.
"At the point where the wing hit ground, there still was no (or very little) roll input. This picture proves it..."
[Unquote]
I am not sure it does. The left aileron is obscured by spray; the right aileron looks a bit up to me, but it is hard to tell. Remember, the neutral position is drooped when flaps are extended.
Am still catching up on some recent posts. The arguments of the formidable German technocrat-trio – ihg, bsieker and PBL – are going to stretch some of us ordinary mortals to the limit!
Quote from CONF iture [Mar07/23:18, #411]:
As you mentioned, take-off is conducted in Roll Direct Law, once airborne a few conditions apply FCOM 1.27.20 P1 and within 5 seconds Roll and Pitch blend in the flight mode.
I don’t see how a reverse process couldn't occur sometime before the flare ?
Adequate flight test program would tell how and where the switch is more appropriate, my guess would be around 1000 ft …
[Unquote]
If you are arguing that the pilot would need those 90 seconds to adapt to Direct Law, I have to agree with you (!), but I don't think we need Direct Law to cope with crosswinds, whether they are inside or outside the certificated limits (preferably the former)...
You repeat your critique of the non-connected sidesticks, and I'm not going to disagree with the logic of your argument. See my various posts on the subject; not least "Airbus FBW – Background" [Mar06/16:47, currently #364]. Twenty years on, the argument is purely rhetorical for the current crop of Airbuses, whether we like it or not.
I don't like the phrase "kicking" off the drift.
[Unquote]
Mea culpa, on at least one occasion. I agree a snap-movement is inappropriate for any large aeroplane. [As you do it with your foot, could we call it a slow kick?] Don't take too long de-crabbing; it's a time of vulnerability to gust, and you would have to start the process even before the comparatively small flare that is advisable on a crosswind landing. This is difficult to get right, and may lead to the necessity of adopting the FULL sideslip configuration, with (as previously agreed) risk of wing-tip contact.
[Interestingly, the DC10-30 Autoland used to start the de-crab at about 130ft, because of the fairly long body; but I don't think we used it in strong crosswinds.]
Hi, Clandestino [Mar07/14:37, #398],
You have raised some interesting points, and you are in current practice, apparently, to try them out (unlike me). Is "17G29" your highest so far? Keep working on it, and have fun.
It is refreshing to receive support for my contention that the A320 family is not particularly difficult (or different) in crosswinds. Me Myself [Mar07/15:17, #403] evidently agrees.
Not sure about releasing the rudder suddenly on take-off rotation, though. Exactly when would you do it? My first reaction is that it sounds more like a simulator pilot's technique than an airline pilot's. Perhaps you can persuade me otherwise?
I would rather stick with the smooth method of pre-empting wing lift with a little into wind aileron. The pilot should already have been applying this throughout the take-off run. Remember that the FBW has been in Roll-Direct Law for the take-off, so has been no different from a conventional aeroplane.
Thanks, XPMorten [Mar07/14:55, #400], for the Airbus Training-Manual extract. I don't think it is really practicable to avoid using large and/or rapid rudder inputs in a strong, gusty crosswind. So I would take their advice and use pre-emptive aileron, as I have been advocating in all my posts.
"If it had been a gust, the aircraft would have crashed."
[Unquote]
I think in the absence of the data (that, no doubt, LH and the pilots have been scrutinising), we cannot be certain. My money, though, would be on a gust. Have not analysed the footage as painstakingly as you have, but the roll-rate seems to increase quite suddenly half way through de-crab, at about the time the A/C leaves the ground in bounce. prior to that, I can see negative and positive gusts at around 50ft.
"At the point where the wing hit ground, there still was no (or very little) roll input. This picture proves it..."
[Unquote]
I am not sure it does. The left aileron is obscured by spray; the right aileron looks a bit up to me, but it is hard to tell. Remember, the neutral position is drooped when flaps are extended.
Am still catching up on some recent posts. The arguments of the formidable German technocrat-trio – ihg, bsieker and PBL – are going to stretch some of us ordinary mortals to the limit!
Quote from CONF iture [Mar07/23:18, #411]:
As you mentioned, take-off is conducted in Roll Direct Law, once airborne a few conditions apply FCOM 1.27.20 P1 and within 5 seconds Roll and Pitch blend in the flight mode.
I don’t see how a reverse process couldn't occur sometime before the flare ?
Adequate flight test program would tell how and where the switch is more appropriate, my guess would be around 1000 ft …
[Unquote]
If you are arguing that the pilot would need those 90 seconds to adapt to Direct Law, I have to agree with you (!), but I don't think we need Direct Law to cope with crosswinds, whether they are inside or outside the certificated limits (preferably the former)...
You repeat your critique of the non-connected sidesticks, and I'm not going to disagree with the logic of your argument. See my various posts on the subject; not least "Airbus FBW – Background" [Mar06/16:47, currently #364]. Twenty years on, the argument is purely rhetorical for the current crop of Airbuses, whether we like it or not.
Last edited by Chris Scott; 8th Mar 2008 at 23:27. Reason: Paragraph sequencing.
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Chris, I agree the video does not have the resolution to see the aileron position but given the aggresive rudder input to swing the nose before touchdown would require an equally aggresive aileron input to keep the wing from coming up as it did. Anything short of to the stops aileron to control the roll as the wing came up is hard to understand no matter if it was a gust or the yaw factor that caused it. Our friends are saying a gust caused it but it still was avoidable in my opinion on the wingtip strike. My background is only with a yoke or stick in front of me, it might be different with the side stick coordinating with a lot of rudder.
Thanks Chris, G29 is my personal best and I don't have much room for improvement as my company's crosswind limit is 30kt, take-off or landing, gusts included.
For a few years I've spent flying fly-by-cable ATR, take-off technique in crosswind was conventional; maintain centerline with rudder and keep wings level with wheel. In significant crosswind this lead to cross-controlled lift off and when positive rate was established, I'd gently release the rudder and turn into wind. Trying to apply this technique to Airbus sim lead to upwind wing lifting, me increasing stick input and then roll into wind as normal law kicked in. Only then I was briefed on let-the-rudder-go technique. I tried it, and it worked in the sim. However, I was not convinced. I thought that it was the sim quirk and that no real aeroplane can fly like that. On my first serious crosswind take off I was back into using my familiar motions. The plane rolled downwind and "You've kept the rudder on takeoff for too long" remark from my instructor was given as soon as we passed FL100. So next time I've centered it as soon as I've pulled the stick back and I thought it to be mightily premature. It turned out it wasn't - airplane just settled into wind with no bank and exactly the right crab angle to maintain the runway track.
I'm aware that airplane is basically in direct law untill 5 secs after lift-off so this manuever has nothing to do with FBW's flight augmentation (EDIT: NOT TRUE - see further posts for explanation). I really can't explain how it works but it does work - I'll bet my wingtips on it anytime.
In normal roll law, stick to the stop will give you only about 40% of available aileron travel. Please do acquaint yourself with contents of FCOM 3.04.27 and FCOM bulletin No54 to see how A320's roll control works. Anyone wishing to argue that Airbus' roll controll is inadequate is most welcome to explain why Airbi don't feature more often in wingtip/podstrike statistics than other types.
Not sure about releasing the rudder suddenly on take-off rotation, though. Exactly when would you do it? My first reaction is that it sounds more like a simulator pilot's technique than an airline pilot's. Perhaps you can persuade me otherwise?
I'm aware that airplane is basically in direct law untill 5 secs after lift-off so this manuever has nothing to do with FBW's flight augmentation (EDIT: NOT TRUE - see further posts for explanation). I really can't explain how it works but it does work - I'll bet my wingtips on it anytime.
Anything short of to the stops aileron to control the roll as the wing came up is hard to understand
Last edited by Clandestino; 9th Mar 2008 at 22:12.
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No kidding....
Well, I've read many of these threads concerning takeoffs and landings in crosswinds in the A-320 series Airbus. Interesting....
I have to strongly suggest that you all not listen to others' 'techinques'...especially some of the nonsense (feel free to substitute another eight-letter word) that 'instructors' are teaching....AND READ THE BOOK FOR YOURSELF!!!!! The FCOM is good reading...The FCTM is even better reading...And, the 'Getting to Grips' series (along with other Airbus publications) will separate the nonsense (again, feel free to substitute another eight letter word) from truth.
I get so frustrated with so called instructors (i.e. 'experts') who teach nonsense....(again...well, you get the idea). READ THE BOOK FOR YOURSELF!!!!
One of the big caveats is...and you have to read for yourself to find this...is that any crab over 5 degrees risks damaging the landing gear. When Airbus published this...they made no distinction between takeoff or landing. If the main gear are still on the runway...and your crab angle exceeds 5 degrees...you risk damaging the gear.
The Airbus flies like any conventional airplane!!!!
Yes, it's true, almost immediately after liftoff, the roll input changes to roll rate. (I can't remember...I think the roll transfers to 'normal law' something like 1/2 second after liftoff....not 5 seconds.)
The correct way to do a crosswind takeoff is to maintain alignment with the runwy until AFTER LIFTOFF...and KEEP THE WINGS LEVEL WITH ROLL CONTROL. It's not difficult. The airplane flies like a normal airplane. However, with roll after liftoff, you're stopping roll rate...stopping the upwind wing from coming up. Again, let me reiterate: Keep the aircraft aligned with the runway UNTIL AFTER LIFTOFF...and KEEP THE WINGS LEVEL. After liftoff, gently relax the rudder pressure...you'll find the roll rate command (which should be ZERO if you're doing things correctly) continues to keep the wings level. You'll be doing runway track...naturally. It's a beautiful thing.
On landing, you align the aircraft with the runway centerline just before touchdown. If a slight wing-down input is necessary to eliminate drift, then that's what you do. In extrememly strong crosswinds, a combination of crab and wing-down will be necessary....and, if the necessary crab angle exceeds 5 degrees...along with the necessary bank angle being too much bank angle to where you scrape a wing tip....(I can't remember offhand the maximum angle...), then you're trying to land in too much crosswind...you either need to select another runway...or, if that's not possible...divert to another airport. In the limitations section, you'll see the published maximum crosswind....if you don't exceed this...you won't exceed crab angle and/or scrape a wingtip.
It's that simple!!!!
READ THE BOOK FOR YOURSELF!!!!
(Now, if your company's SOP says otherwise...then, that's what you gotta do. You have no choice!)
Fly safe,
Pantload
I have to strongly suggest that you all not listen to others' 'techinques'...especially some of the nonsense (feel free to substitute another eight-letter word) that 'instructors' are teaching....AND READ THE BOOK FOR YOURSELF!!!!! The FCOM is good reading...The FCTM is even better reading...And, the 'Getting to Grips' series (along with other Airbus publications) will separate the nonsense (again, feel free to substitute another eight letter word) from truth.
I get so frustrated with so called instructors (i.e. 'experts') who teach nonsense....(again...well, you get the idea). READ THE BOOK FOR YOURSELF!!!!
One of the big caveats is...and you have to read for yourself to find this...is that any crab over 5 degrees risks damaging the landing gear. When Airbus published this...they made no distinction between takeoff or landing. If the main gear are still on the runway...and your crab angle exceeds 5 degrees...you risk damaging the gear.
The Airbus flies like any conventional airplane!!!!
Yes, it's true, almost immediately after liftoff, the roll input changes to roll rate. (I can't remember...I think the roll transfers to 'normal law' something like 1/2 second after liftoff....not 5 seconds.)
The correct way to do a crosswind takeoff is to maintain alignment with the runwy until AFTER LIFTOFF...and KEEP THE WINGS LEVEL WITH ROLL CONTROL. It's not difficult. The airplane flies like a normal airplane. However, with roll after liftoff, you're stopping roll rate...stopping the upwind wing from coming up. Again, let me reiterate: Keep the aircraft aligned with the runway UNTIL AFTER LIFTOFF...and KEEP THE WINGS LEVEL. After liftoff, gently relax the rudder pressure...you'll find the roll rate command (which should be ZERO if you're doing things correctly) continues to keep the wings level. You'll be doing runway track...naturally. It's a beautiful thing.
On landing, you align the aircraft with the runway centerline just before touchdown. If a slight wing-down input is necessary to eliminate drift, then that's what you do. In extrememly strong crosswinds, a combination of crab and wing-down will be necessary....and, if the necessary crab angle exceeds 5 degrees...along with the necessary bank angle being too much bank angle to where you scrape a wing tip....(I can't remember offhand the maximum angle...), then you're trying to land in too much crosswind...you either need to select another runway...or, if that's not possible...divert to another airport. In the limitations section, you'll see the published maximum crosswind....if you don't exceed this...you won't exceed crab angle and/or scrape a wingtip.
It's that simple!!!!
READ THE BOOK FOR YOURSELF!!!!
(Now, if your company's SOP says otherwise...then, that's what you gotta do. You have no choice!)
Fly safe,
Pantload
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Clandestino
At about how many % stick deflection does roll SPOILERS get
activated on an A32x?
On e.g. the B757, roll spoiler activation starts at about 10% control wheel
deflection.
If we look at the pictures again;
http://img529.imageshack.us/img529/2745/undhp089zu5.jpg
This picture clearly shows roll spoiler deflection on the left wing.
http://www.airliners.net/uf/53688288.../phpOltUWB.jpg
Much less here - if any...
M
In normal roll law, stick to the stop will give you only about 40% of available aileron travel. Please do acquaint yourself with contents of FCOM 3.04.27 and FCOM bulletin No54 to see how A320's roll control works.
activated on an A32x?
On e.g. the B757, roll spoiler activation starts at about 10% control wheel
deflection.
If we look at the pictures again;
http://img529.imageshack.us/img529/2745/undhp089zu5.jpg
This picture clearly shows roll spoiler deflection on the left wing.
http://www.airliners.net/uf/53688288.../phpOltUWB.jpg
Much less here - if any...
M
Last edited by XPMorten; 9th Mar 2008 at 11:48.
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bsieker,
I won’t pretend to be sufficiently qualified but I’d like to add a little something:
A320 FCOM BULLETIN 54/2
Aircraft Handling in Final Approach
"the fly-by-wire system counteracts the effects of gust, even with the sidestsick in the neutral position"
You think “the phrase is sufficiently vague” now try this one:
A330 FCOM BULLETIN 813/1A JUN 04
Aircraft Handling in Final Approach
"The flight control system of Airbus fly-by-wire aircraft partially counteracts roll movements induced by the effects of gust, even with the sidestick in the neutral position"
Airbus could be more confused than we are … or is it that difficult to put it in words even 20 years later ?
On top of Flight Crew Operation Manuals + Flight Crew Training Manual + Standard Operation Procedures, Airbus feels the need for a few Flight Crew Operation Manual Bulletins related to early and late phases of a flight, when pilot manual skills mater!
- Avoiding tailstrikes
- A/C handling in final approach
- Avoiding hard landing
Quite ironic after the following statement pronounced by B.Ziegler himself:
“le 320, même ma concierge pourrait le piloter” (not sure how to translate it)
It does also give an idea how the head of Airbus FBW engineering design was valuing the pilot profession.
Chris,
Thanks for the clarity of your posts and also for your honesty.
You was part of the 320 early operational days, it must have been exciting but also quite challenging … Was it under the British Caledonian Airways colors ?
As you told it here, pilots put pressure for modifications … “but Mr Ziegler prevailed”
I believe Mr Ziegler has been somehow too prominent in the FBW Airbus conception and took some “radical and irrevocable decisions on A320 design” without properly consulting.
A table on long haul flight is nice for sure, but I don’t mind waiting to be at destination for an even proper table with red wine, candle, and nice company, and retain the privilege of fully visible connected flight controls in always possible adverse approach conditions.
I believe Boeing fully understood it … Also, they opted for more simple flight control laws, that could be a reason they’re not part of these rocking wings shows on YouTube:
Lisbon
Hamburg
Bilbao
Regarding Thrust Levers, I’ve heard they were not supposed to have any, just Push Buttons for different settings, and therefore no possibility for Manual Thrust … but it could be just part of the myth, maybe you know more ?
I won’t pretend to be sufficiently qualified but I’d like to add a little something:
A320 FCOM BULLETIN 54/2
Aircraft Handling in Final Approach
"the fly-by-wire system counteracts the effects of gust, even with the sidestsick in the neutral position"
You think “the phrase is sufficiently vague” now try this one:
A330 FCOM BULLETIN 813/1A JUN 04
Aircraft Handling in Final Approach
"The flight control system of Airbus fly-by-wire aircraft partially counteracts roll movements induced by the effects of gust, even with the sidestick in the neutral position"
Airbus could be more confused than we are … or is it that difficult to put it in words even 20 years later ?
On top of Flight Crew Operation Manuals + Flight Crew Training Manual + Standard Operation Procedures, Airbus feels the need for a few Flight Crew Operation Manual Bulletins related to early and late phases of a flight, when pilot manual skills mater!
- Avoiding tailstrikes
- A/C handling in final approach
- Avoiding hard landing
Quite ironic after the following statement pronounced by B.Ziegler himself:
“le 320, même ma concierge pourrait le piloter” (not sure how to translate it)
It does also give an idea how the head of Airbus FBW engineering design was valuing the pilot profession.
Chris,
Thanks for the clarity of your posts and also for your honesty.
You was part of the 320 early operational days, it must have been exciting but also quite challenging … Was it under the British Caledonian Airways colors ?
As you told it here, pilots put pressure for modifications … “but Mr Ziegler prevailed”
I believe Mr Ziegler has been somehow too prominent in the FBW Airbus conception and took some “radical and irrevocable decisions on A320 design” without properly consulting.
A table on long haul flight is nice for sure, but I don’t mind waiting to be at destination for an even proper table with red wine, candle, and nice company, and retain the privilege of fully visible connected flight controls in always possible adverse approach conditions.
I believe Boeing fully understood it … Also, they opted for more simple flight control laws, that could be a reason they’re not part of these rocking wings shows on YouTube:
Lisbon
Hamburg
Bilbao
Regarding Thrust Levers, I’ve heard they were not supposed to have any, just Push Buttons for different settings, and therefore no possibility for Manual Thrust … but it could be just part of the myth, maybe you know more ?
Thank you for your most considerate post mr. PantLoad. It made me review my FCOM and now I see that illustration on page 1.27.20 P1, that showed time for blending in normal law after lift-off as 5 seconds has been changed. The new scheme now splits mode row in two rows - pitch and lateral control. Pitch row still shows 5 secs for flight mode to take over after lift-off, but the newly featured lateral contol row now shows this time to be only 0.5 seconds.
Therefore, I stand corrected, it is indeed FBW that keeps our wings level immediately after lift-off. Mea culpa - I've really should check out the FCOM updates more thoroughly.
but..
A320 FCOM 3.04.27 P4 SEQ 001 REV 36
I absolutely agree that wings have to be kept level during take-off run by using lateral control. From my experience, lightly loaded A320 in 25kt crosswind will take almost... no stick deflection to keep wings level therefore, I agree with FCOM that lateral control may be used but I'd also add that it will be seldom needed.
Thank you for pointing out 5° crab angle on ground generic limit for Airbi, from 300 to 380, but rest assured that I've never approached this limit, even as I eased the pedals during rotation, with significant crosswind, on wet runway (and I ment eased, not kicked them to neutral or beyond). You see, even as rudder goes to neutral during rotation, airplane doesn't immediately weathercock into wind but rather gently crabs so the actual lift-off is achieved with so little drift it's almost imperceptible.
Actually, out of disbelief, I did initially try maintain alignment with the runwy until AFTER LIFTOFF by using rudder. It works fine when winds are light and I assume that ELACs have the capability to fight pilot's rudder input and light winds at the same time. However, with stronger winds rudder goes further and things get a bit more complicated for FBW as you lift off, wing goes up and you're stopping roll rate (with stick, i.e. roll demand)...stopping the upwind wing from coming up.
So I've tried both methods and I know which one gives me lesser roll excursions after liftoff. Hint: I'm still convinced that FBW can compensate roll from 30kt xwind by itself but 30kt wind and opposite rudder is a different story.
Happy contrails
Therefore, I stand corrected, it is indeed FBW that keeps our wings level immediately after lift-off. Mea culpa - I've really should check out the FCOM updates more thoroughly.
but..
A320 FCOM 3.04.27 P4 SEQ 001 REV 36
For crosswind takeoffs, routine use of into wind aileron is not recommended. In strong crosswind conditions, some lateral control may be used, but care should be taken to avoid using large deflections, resulting in excessive spoiler deployment which increases tendency to turn into wind, reduces lift and increases drag. Spoiler deflection starts to become significant with more than one third stick deflection. As the aircraft lifts off, any lateral control applied will result in a roll rate demand.
Thank you for pointing out 5° crab angle on ground generic limit for Airbi, from 300 to 380, but rest assured that I've never approached this limit, even as I eased the pedals during rotation, with significant crosswind, on wet runway (and I ment eased, not kicked them to neutral or beyond). You see, even as rudder goes to neutral during rotation, airplane doesn't immediately weathercock into wind but rather gently crabs so the actual lift-off is achieved with so little drift it's almost imperceptible.
Actually, out of disbelief, I did initially try maintain alignment with the runwy until AFTER LIFTOFF by using rudder. It works fine when winds are light and I assume that ELACs have the capability to fight pilot's rudder input and light winds at the same time. However, with stronger winds rudder goes further and things get a bit more complicated for FBW as you lift off, wing goes up and you're stopping roll rate (with stick, i.e. roll demand)...stopping the upwind wing from coming up.
So I've tried both methods and I know which one gives me lesser roll excursions after liftoff. Hint: I'm still convinced that FBW can compensate roll from 30kt xwind by itself but 30kt wind and opposite rudder is a different story.
Happy contrails
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First post on PP but I had to jump in after following a most interesting thread. It seems that this incident can be broken down into a number of components all of which have been touched on at some point in the thread. What were the winds that tower reported to the LH flight when it was cleared to land? What are LH's (not my carrier or yours, but LH's) X-wind limits for the 320? Did the tower reported winds fall in excess of that limit? What was the time interval between the LH approach and the last measured peak gust? Was the runway reported as wet? Is it grooved? Were there any log items in the mx section of the dispatch that I would need to be aware of? How many hours has each pilot flown in the last 30/60/90?
These are all questions whose answers I still do not know (unless I missed them in the thread - entirely possible) but are questions that are germane to the incident and when realeased, will dispel what heretofore has been a lot of speculation.
I only have a little of 1000 hours in the Bus (although 15 years of airline flying for what that is worth - which may be nothing!) but I remember my intitial instructor's comments that the Bus FBW makes corrections and has the famous protections, but it is not an instantaneous effect. Take it at 250 clean and pull the throttle to idle and pull the stick all the way back and see if the protections can completely keep you out of trouble with the rapid airspeed decay from the zoom. Maybe, maybe not.
With that in mind, I can see when one applies the rudder as rapidly and vigorously as the handling pilot did in this case that I would have to throw my lot in with XPMorten that being a swept wing aircraft you are certainly going to need to control the right winging generating lift and rising irrespective of rolls rates/direct law/design comprises and other fine argumentative points.
I will have to admit that I remain very intrigued about the decision making process and have to be open to what a lot of the unanswered questions would reveal. The captain flew a damaged aircraft away from the ground and landed safely. Yet I read a book recently entitled The Outer Whorl by a guy who flew in the same military reserve unit that I did. No endorsement needed from my humble literary skills as it is an outstanding aviation read and more than stands on its own merits, but I remember he had one chapter about pessimism and expecting the worst. It has made me think a lot about decision making in the jet and to sharpen up a little when it comes to mentally preparing for something bad. Should not, when operating at or above the carrier's limits for X-winds, have been cause to think that a bad gust could be problematic? When at limits (again what were the last reported winds?) was the skipper expecting the worst?
I do not know the answers to those questions but I wish that I did. I guess what I am trying to say in my first post is that any incident/accident has a lot of layers. There are things that we do not know and I will be anxious to not only know them, but also to learn from them. Give me a dollar for every mistake I have made in an airplane and I would be rich beyond my dreams. Goat or hero for the skipper? I will leave the jury out for now.
This is a good thread. Good tech talk. Keep it going.
Basil
These are all questions whose answers I still do not know (unless I missed them in the thread - entirely possible) but are questions that are germane to the incident and when realeased, will dispel what heretofore has been a lot of speculation.
I only have a little of 1000 hours in the Bus (although 15 years of airline flying for what that is worth - which may be nothing!) but I remember my intitial instructor's comments that the Bus FBW makes corrections and has the famous protections, but it is not an instantaneous effect. Take it at 250 clean and pull the throttle to idle and pull the stick all the way back and see if the protections can completely keep you out of trouble with the rapid airspeed decay from the zoom. Maybe, maybe not.
With that in mind, I can see when one applies the rudder as rapidly and vigorously as the handling pilot did in this case that I would have to throw my lot in with XPMorten that being a swept wing aircraft you are certainly going to need to control the right winging generating lift and rising irrespective of rolls rates/direct law/design comprises and other fine argumentative points.
I will have to admit that I remain very intrigued about the decision making process and have to be open to what a lot of the unanswered questions would reveal. The captain flew a damaged aircraft away from the ground and landed safely. Yet I read a book recently entitled The Outer Whorl by a guy who flew in the same military reserve unit that I did. No endorsement needed from my humble literary skills as it is an outstanding aviation read and more than stands on its own merits, but I remember he had one chapter about pessimism and expecting the worst. It has made me think a lot about decision making in the jet and to sharpen up a little when it comes to mentally preparing for something bad. Should not, when operating at or above the carrier's limits for X-winds, have been cause to think that a bad gust could be problematic? When at limits (again what were the last reported winds?) was the skipper expecting the worst?
I do not know the answers to those questions but I wish that I did. I guess what I am trying to say in my first post is that any incident/accident has a lot of layers. There are things that we do not know and I will be anxious to not only know them, but also to learn from them. Give me a dollar for every mistake I have made in an airplane and I would be rich beyond my dreams. Goat or hero for the skipper? I will leave the jury out for now.
This is a good thread. Good tech talk. Keep it going.
Basil
Memory Lane (off-topic...)
Have had a manic weekend, and now see at this late hour (in UK) that this interesting discussion has been continuing apace. Will have to catch up tomorrow, but can try to answer a few questions from CONFI ture:
Quite ironic after the following statement pronounced by B.Ziegler himself: “le 320, même ma concierge pourrait le piloter” (not sure how to translate it)
[Unquote]
Surprised that a bilingual/multilingual Francophone would baulk at translation! "Even my doorman could fly it," will do. We overpaid pilots felt it was a bit of a "put down", but he probably didn't mean it that way.
I believe Mr Ziegler has been somehow too prominent in the FBW Airbus conception and took some “radical and irrevocable decisions on A320 design” without properly consulting.
[Unquote]
If my quoted remark is justified (and I think it is), you should remember the history of many aircraft projects, some of them British, in the post-war years. Sometimes you have to have one very strong, even - bloody-minded - person, who will take a project by the scruff of its neck and push it along. That means it will have his/her stamp all over it; "warts and all". So lesser mortals have to hope the "warts" are not serious.
Regarding Thrust Levers, I’ve heard they were not supposed to have any, just Push Buttons for different settings, and therefore no possibility for Manual Thrust … but it could be just part of the myth, maybe you know more ?
[Unquote]
Yes, had almost forgotten that one. Either it was just a bargaining gambit by BZ, or perhaps we pilots were not entirely ignored. I only mentioned the design changes sought by the pilots' unions, but it goes without saying that the 3 launch-customer airlines (AF, BCAL and Air Inter) were in constant discussion with Airbus. In BCAL's case, the management-pilot input was led by George H, A320 Project and Development Pilot. We ended up with a beautiful manual throttle, which I used on 95% of my manual landings; including limiting crosswinds.
OFF-TOPIC
The one A320 painted with a complete BCAL colour sceme had it on the L/H side only, if memory serves. The R/H side, I think, was in Air France livery (or Air Inter). Can't remember if that one was used for my base training at Blagnac in March 1988. BCAL's AOC was effectively transferred to BA on 1/4/88, which was the day our first A320 (as G-BUSB, a dash-100, with no winglets) was delivered to Gatwick - in BA colours. We operated them out of the newly-opened North Terminal on a mixture of day schedules and night charters for the first 6 months. In October/November, the expanding fleet moved to Heathrow. In due course, we received the total BCAL order of 5 "100"s and 5 "200"s, ending with G-BUSK.
In 1988, we were a very happy and dedicated small team of ex-BCAL pilots, and we all loved the little aeroplane from Day1. Our success eventually persuaded some "real" BA pilots and ground engineers to join us, the former led by Colin W, who became our first proper BA management pilot at the time we moved to Heathrow, and a great ambassador for A320 in Boeing Airways [er, sorry - BA].
We continued to fly a successful operation for many years, hoping BA would buy A340s and/or A330s. Instead, we ordered B767-300s...
It was many years before BA ordered Airbuses for the first time, and then they were IAE-A319/321/320. 20 years after we started, as everyone knows, their narrow-body Airbus fleet is enormous. But no wide-bodies, yet...
Quite ironic after the following statement pronounced by B.Ziegler himself: “le 320, même ma concierge pourrait le piloter” (not sure how to translate it)
[Unquote]
Surprised that a bilingual/multilingual Francophone would baulk at translation! "Even my doorman could fly it," will do. We overpaid pilots felt it was a bit of a "put down", but he probably didn't mean it that way.
I believe Mr Ziegler has been somehow too prominent in the FBW Airbus conception and took some “radical and irrevocable decisions on A320 design” without properly consulting.
[Unquote]
If my quoted remark is justified (and I think it is), you should remember the history of many aircraft projects, some of them British, in the post-war years. Sometimes you have to have one very strong, even - bloody-minded - person, who will take a project by the scruff of its neck and push it along. That means it will have his/her stamp all over it; "warts and all". So lesser mortals have to hope the "warts" are not serious.
Regarding Thrust Levers, I’ve heard they were not supposed to have any, just Push Buttons for different settings, and therefore no possibility for Manual Thrust … but it could be just part of the myth, maybe you know more ?
[Unquote]
Yes, had almost forgotten that one. Either it was just a bargaining gambit by BZ, or perhaps we pilots were not entirely ignored. I only mentioned the design changes sought by the pilots' unions, but it goes without saying that the 3 launch-customer airlines (AF, BCAL and Air Inter) were in constant discussion with Airbus. In BCAL's case, the management-pilot input was led by George H, A320 Project and Development Pilot. We ended up with a beautiful manual throttle, which I used on 95% of my manual landings; including limiting crosswinds.
OFF-TOPIC
The one A320 painted with a complete BCAL colour sceme had it on the L/H side only, if memory serves. The R/H side, I think, was in Air France livery (or Air Inter). Can't remember if that one was used for my base training at Blagnac in March 1988. BCAL's AOC was effectively transferred to BA on 1/4/88, which was the day our first A320 (as G-BUSB, a dash-100, with no winglets) was delivered to Gatwick - in BA colours. We operated them out of the newly-opened North Terminal on a mixture of day schedules and night charters for the first 6 months. In October/November, the expanding fleet moved to Heathrow. In due course, we received the total BCAL order of 5 "100"s and 5 "200"s, ending with G-BUSK.
In 1988, we were a very happy and dedicated small team of ex-BCAL pilots, and we all loved the little aeroplane from Day1. Our success eventually persuaded some "real" BA pilots and ground engineers to join us, the former led by Colin W, who became our first proper BA management pilot at the time we moved to Heathrow, and a great ambassador for A320 in Boeing Airways [er, sorry - BA].
We continued to fly a successful operation for many years, hoping BA would buy A340s and/or A330s. Instead, we ordered B767-300s...
It was many years before BA ordered Airbuses for the first time, and then they were IAE-A319/321/320. 20 years after we started, as everyone knows, their narrow-body Airbus fleet is enormous. But no wide-bodies, yet...
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Lesson learnt?
Fortunately the incident in HAM caused no fatalities.
However, under the assumption that wrong handling in flying the airplane led to the incident, what is the lesson to learn?
I think consequences should be considered both for training requirements and future design of airplanes.
Pilots are increasingly considered as “cockpit managers”. Good flying skills seem more and more to belong to a phase-out model of a pilot. I heard recently about plans to license pilots with zero flight time gaining all their experience in simulator sessions only.
However, events like on LH044 show that excellent handling skills in piloting are not dispensable and have to be developed in training with small aircraft. If pilots get their first seat in an airliner it is too late for training basic handling skills. Side-slip technique is a good example for this. I think the current training setup and requirements particularly for beginner F/Os in legacy carriers contains too little flight experience until being released on airliners. The focus is too much on “cockpit managers”. Managing cockpit systems is increasingly important in modern airplanes though not enough.
Automation in airplanes is a vital tool for our daily work and undoubtedly contributes to flight safety, however cannot substitute good flying skills entirely. There are situations where even the smartest technical features cannot cope with human skills, e.g. pilots know about the lower wind limits for an automatic versus manual landing.
The conclusion that pilots are the weakest part in air safety contributing mostly to accidents by their mistakes is inappropriate and unilateral. The overwhelming majority of occurrences when pilots cover system failures does not show up in any statistics or in the press, yet is our daily work. Engineers should take this into consideration for future generations of airplanes. Flying in unmanned airplanes as a passenger – no thanks with my experience as pilot!
However, under the assumption that wrong handling in flying the airplane led to the incident, what is the lesson to learn?
I think consequences should be considered both for training requirements and future design of airplanes.
Pilots are increasingly considered as “cockpit managers”. Good flying skills seem more and more to belong to a phase-out model of a pilot. I heard recently about plans to license pilots with zero flight time gaining all their experience in simulator sessions only.
However, events like on LH044 show that excellent handling skills in piloting are not dispensable and have to be developed in training with small aircraft. If pilots get their first seat in an airliner it is too late for training basic handling skills. Side-slip technique is a good example for this. I think the current training setup and requirements particularly for beginner F/Os in legacy carriers contains too little flight experience until being released on airliners. The focus is too much on “cockpit managers”. Managing cockpit systems is increasingly important in modern airplanes though not enough.
Automation in airplanes is a vital tool for our daily work and undoubtedly contributes to flight safety, however cannot substitute good flying skills entirely. There are situations where even the smartest technical features cannot cope with human skills, e.g. pilots know about the lower wind limits for an automatic versus manual landing.
The conclusion that pilots are the weakest part in air safety contributing mostly to accidents by their mistakes is inappropriate and unilateral. The overwhelming majority of occurrences when pilots cover system failures does not show up in any statistics or in the press, yet is our daily work. Engineers should take this into consideration for future generations of airplanes. Flying in unmanned airplanes as a passenger – no thanks with my experience as pilot!
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Use as much as is necessary...
Use as much (or as little) roll as is necessary to maintain wings level. If this means no roll input, so be it. Usually, in strong crosswinds, a little ("a little") is needed.
The FCTM goes into more detail on this...as does the "Getting to Grips" series.
I have to emphasize that this airplane really does fly like a regular airplane. I know many disagree, but it's just a damn airplane. You, the pilot, have control of three axis. The fact that you have computers helping you doesn't change the fact that you have three axis of control. Use the controls necessary to acheive the desired flight path. If the computers assist to the point where you need no control input for a particular flight path correction, so be it. If you must add a bit of your own input, then do it. The end result should be the same as with any conventional airplane.
Yes, the blend from ground mode of normal law to flight mode of normal law is split between pitch and roll. So, with that, you have to be aware that immediately after liftoff, your aileron command changes a bit.
I'm not a salesman for Airbus, and I DO prefer a Boeing. But, there are some really nice features of the Bus that I love....The FBW is great.
PantLoad
The FCTM goes into more detail on this...as does the "Getting to Grips" series.
I have to emphasize that this airplane really does fly like a regular airplane. I know many disagree, but it's just a damn airplane. You, the pilot, have control of three axis. The fact that you have computers helping you doesn't change the fact that you have three axis of control. Use the controls necessary to acheive the desired flight path. If the computers assist to the point where you need no control input for a particular flight path correction, so be it. If you must add a bit of your own input, then do it. The end result should be the same as with any conventional airplane.
Yes, the blend from ground mode of normal law to flight mode of normal law is split between pitch and roll. So, with that, you have to be aware that immediately after liftoff, your aileron command changes a bit.
I'm not a salesman for Airbus, and I DO prefer a Boeing. But, there are some really nice features of the Bus that I love....The FBW is great.
PantLoad
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igh,
As I said, I think you're trying to make a distinction without a difference.
1. An ELAC and any FCC in any FBW airplane is run by a bunch of code. I don't know what you want to mean by "incorporate a numerical model" in such a way that other FCCs have it but ELACs don't. They all have numerical calculations built in, and those numerical calculations are obviously based upon the numerical flight characteristics of the airplane, otherwise how could you get those wonderful Bode and Nyquist plots?
2. Controllers don't "know" anything. They run code. No FBW controller I know controls the airplane according to internal parameters alone (thank heavens!). All such systems are feedback control, which means that
* there are target values for parameters
* actual values of those parameters are obtained by sensing
* the controller issues actuation commands to bring the actual values closer to the target values
Now, this all happens at the speed of electrical signals through copper wiring, which some significant fraction of the speed of light, and the signals only have to go a few meters.
3. Nothing happens in advance in a feedback controller. And neither is there any significant latency in the digital control. Sensing, computing and commanding happen to all intents and purposes instantaneously. Sensing in unstable airplanes such as the F-16 happens at about 200Hz; I don't know the sensing rate for roll on the A320. There may be some latency due to the physical characteristics of the actuators, but this has little to do with how the controller is designed (except, of course, that such latency will be accomodated where needed).
4. Nobody is suggesting the decoupling is completely, rigorously effective in all situations. Indeed, posts from Chris Scott and others say most clearly that it isn't. But I don't see that the strength of the decoupling has anything to do with "back door" or "front door". The kit is clearly designed to decouple roll from yaw, as other posts (for example from Clandestino) show, and as you seem to agree.
5. I doubt decoupling is properly describable as a "side effect" of the control SW design in the ELAC, as you suggested. Decoupling is, obviously, designed in and is there quite intentionally. It's in the manuals, as we have seen. As are its limitations.
PBL
As I said, I think you're trying to make a distinction without a difference.
A 'true' or 'real' yaw-roll decoupling would mean to me a 'model based controller', i.e. A controller which incorporates a numeric model of the aircraft flight mechanics characteristics. That means the controller 'knows' in advance how the A/C 'will' react to a certain rudder deflection and thus commands the appropriate amount of aileron deflection 'simultaneously' and 'instantly' to fully compress the yaw-roll coupling induced roll. Depending on the actual implementation and the actuator rate capacity you wouldn't see any roll then.
2. Controllers don't "know" anything. They run code. No FBW controller I know controls the airplane according to internal parameters alone (thank heavens!). All such systems are feedback control, which means that
* there are target values for parameters
* actual values of those parameters are obtained by sensing
* the controller issues actuation commands to bring the actual values closer to the target values
Now, this all happens at the speed of electrical signals through copper wiring, which some significant fraction of the speed of light, and the signals only have to go a few meters.
3. Nothing happens in advance in a feedback controller. And neither is there any significant latency in the digital control. Sensing, computing and commanding happen to all intents and purposes instantaneously. Sensing in unstable airplanes such as the F-16 happens at about 200Hz; I don't know the sensing rate for roll on the A320. There may be some latency due to the physical characteristics of the actuators, but this has little to do with how the controller is designed (except, of course, that such latency will be accomodated where needed).
4. Nobody is suggesting the decoupling is completely, rigorously effective in all situations. Indeed, posts from Chris Scott and others say most clearly that it isn't. But I don't see that the strength of the decoupling has anything to do with "back door" or "front door". The kit is clearly designed to decouple roll from yaw, as other posts (for example from Clandestino) show, and as you seem to agree.
5. I doubt decoupling is properly describable as a "side effect" of the control SW design in the ELAC, as you suggested. Decoupling is, obviously, designed in and is there quite intentionally. It's in the manuals, as we have seen. As are its limitations.
PBL
Last edited by PBL; 10th Mar 2008 at 11:37. Reason: Mods, please delete this version of the duplicated message. I cannot seem to do it myself
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igh,
As I said, I think you're trying to make a distinction without a difference.
1. An ELAC and any FCC in any FBW airplane is run by a bunch of code. I don't know what you want to mean by "incorporate a numerical model" in such a way that other FCCs have it but ELACs don't. They all have numerical calculations built in, and those numerical calculations are obviously based upon the numerical flight characteristics of the airplane, otherwise how could you get those wonderful Bode and Nyquist plots?
2. Controllers don't "know" anything. They run code. No FBW controller I know controls the airplane according to internal parameters alone (thank heavens!). All such systems are feedback control, which means that
* there are target values for parameters
* actual values of those parameters are obtained by sensing
* the controller issues actuation commands to bring the actual values closer to the target values
Now, this all happens at the speed of electrical signals through copper wiring, at some significant fraction of the speed of light, and the signals only have to go a few meters.
3. Nothing happens "in advance" in a feedback controller. And neither is there any significant latency in the digital control. Sensing, computing and commanding happen to all intents and purposes instantaneously. Sensing in unstable airplanes such as the F-16 happens at about 200Hz; I don't know the sensing rate for roll on the A320. There may be some latency due to the physical characteristics of the actuators, but this has little to do with how the controller is designed (except, of course, that such latency will be accomodated where needed).
4. Nobody is suggesting the yaw-roll decoupling is completely, rigorously effective in all situations. Indeed, posts from Chris Scott and others say most clearly that it isn't. But I don't see that the strength of the decoupling has anything to do with "back door" or "front door". The kit is clearly designed to decouple roll from yaw, and does in many normal situations, as other posts (for example from Clandestino) show, and as you seem to agree.
5. I doubt decoupling is properly describable as a "side effect" of the control SW design in the ELAC, as you suggested. Decoupling is, obviously, designed in and is there quite intentionally. It's in the manuals, as we have seen. As are its limitations.
PBL
As I said, I think you're trying to make a distinction without a difference.
A 'true' or 'real' yaw-roll decoupling would mean to me a 'model based controller', i.e. A controller which incorporates a numeric model of the aircraft flight mechanics characteristics. That means the controller 'knows' in advance how the A/C 'will' react to a certain rudder deflection and thus commands the appropriate amount of aileron deflection 'simultaneously' and 'instantly' to fully compress the yaw-roll coupling induced roll. Depending on the actual implementation and the actuator rate capacity you wouldn't see any roll then.
2. Controllers don't "know" anything. They run code. No FBW controller I know controls the airplane according to internal parameters alone (thank heavens!). All such systems are feedback control, which means that
* there are target values for parameters
* actual values of those parameters are obtained by sensing
* the controller issues actuation commands to bring the actual values closer to the target values
Now, this all happens at the speed of electrical signals through copper wiring, at some significant fraction of the speed of light, and the signals only have to go a few meters.
3. Nothing happens "in advance" in a feedback controller. And neither is there any significant latency in the digital control. Sensing, computing and commanding happen to all intents and purposes instantaneously. Sensing in unstable airplanes such as the F-16 happens at about 200Hz; I don't know the sensing rate for roll on the A320. There may be some latency due to the physical characteristics of the actuators, but this has little to do with how the controller is designed (except, of course, that such latency will be accomodated where needed).
4. Nobody is suggesting the yaw-roll decoupling is completely, rigorously effective in all situations. Indeed, posts from Chris Scott and others say most clearly that it isn't. But I don't see that the strength of the decoupling has anything to do with "back door" or "front door". The kit is clearly designed to decouple roll from yaw, and does in many normal situations, as other posts (for example from Clandestino) show, and as you seem to agree.
5. I doubt decoupling is properly describable as a "side effect" of the control SW design in the ELAC, as you suggested. Decoupling is, obviously, designed in and is there quite intentionally. It's in the manuals, as we have seen. As are its limitations.
PBL
Handling skills...
Quote from NOR116,2 [Today, 02:42, currently#429]
Pilots are increasingly considered as “cockpit managers”. Good flying skills seem more and more to belong to a phase-out model of a pilot...
However, events like on LH044 show that excellent handling skills in piloting are not dispensable and have to be developed in training with small aircraft. If pilots get their first seat in an airliner it is too late for training basic handling skills.
[Unquote]
Just one part of an excellent posting.
The introduction of CRM in the 1980s - much of it researched by NASA and owing, no doubt, a lot to Jim Lovell's crew's experience on Apollo 13 – was generally "A GOOD THING". The snag was that the guys who could have most benefited from it were the ones that pooh-poohed it.
Initially, CRM emphasised the inter-personal skills elements. The problem-handling guidelines came later, though, with things like "DODAR".
There did seem to be a period, around the early 1990s, when we had become so politically-correct that it had become acceptable for inexperienced copilots to criticize the captain, but not the other way round. A tiny element of them were encouraged to become overbearing pre-madonnas. [I'm talking mainly about male madonnas, if that's not an oxymoron.]
Irrespective of the fact that I was flying the A320 throughout the 1990s, it became clear that basic handling skills were taking a back seat in ab-initio training. I once flew with a pleasant female copilot, newly converted on the A320 as her first airliner-type, who applied aileron the wrong way on a landing in a (fortunately) light crosswind, and then argued that you could use the roll-control of the sidestick to "steer" the aeroplane on the runway...
Pilots are increasingly considered as “cockpit managers”. Good flying skills seem more and more to belong to a phase-out model of a pilot...
However, events like on LH044 show that excellent handling skills in piloting are not dispensable and have to be developed in training with small aircraft. If pilots get their first seat in an airliner it is too late for training basic handling skills.
[Unquote]
Just one part of an excellent posting.
The introduction of CRM in the 1980s - much of it researched by NASA and owing, no doubt, a lot to Jim Lovell's crew's experience on Apollo 13 – was generally "A GOOD THING". The snag was that the guys who could have most benefited from it were the ones that pooh-poohed it.
Initially, CRM emphasised the inter-personal skills elements. The problem-handling guidelines came later, though, with things like "DODAR".
There did seem to be a period, around the early 1990s, when we had become so politically-correct that it had become acceptable for inexperienced copilots to criticize the captain, but not the other way round. A tiny element of them were encouraged to become overbearing pre-madonnas. [I'm talking mainly about male madonnas, if that's not an oxymoron.]
Irrespective of the fact that I was flying the A320 throughout the 1990s, it became clear that basic handling skills were taking a back seat in ab-initio training. I once flew with a pleasant female copilot, newly converted on the A320 as her first airliner-type, who applied aileron the wrong way on a landing in a (fortunately) light crosswind, and then argued that you could use the roll-control of the sidestick to "steer" the aeroplane on the runway...
Last edited by Chris Scott; 10th Mar 2008 at 15:47. Reason: "ab-initio" added. Further clarification.
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Thanks Chris for sharing your memories on the 320 first years operation.
Your tone is quite similar to what M.Asseline was describing in his book, everybody was enthusiast to transform this Adventure in a Success story.
What has been your view on Habsheim and how did you deal with that event afterward ?
To go back to the topic and your anecdote, how did you notice your FO was trying to steer with the sidestick ?
NOR116,2 I also share your view.
Earlier you mentioned the idea of interlinked sidesticks, so I’d like to refer to another posting from last year, here
PantLoad, I didn’t really get your point when you mention the takeoff phase, with main gear still on the runway ... and crab exceeding 5 degrees ... ?
I don’t think anybody would or even could attempt that without visiting the grass, unless rwy surface is very slippery ... !?
Your tone is quite similar to what M.Asseline was describing in his book, everybody was enthusiast to transform this Adventure in a Success story.
What has been your view on Habsheim and how did you deal with that event afterward ?
To go back to the topic and your anecdote, how did you notice your FO was trying to steer with the sidestick ?
NOR116,2 I also share your view.
Earlier you mentioned the idea of interlinked sidesticks, so I’d like to refer to another posting from last year, here
PantLoad, I didn’t really get your point when you mention the takeoff phase, with main gear still on the runway ... and crab exceeding 5 degrees ... ?
I don’t think anybody would or even could attempt that without visiting the grass, unless rwy surface is very slippery ... !?
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Crab...
I was referring to some 'techniques' taught by some....
The aircraft needs to be aligned with the runway while it's on the runway. Exception is when crosswinds are 'strong' (as stated by Airbus), where crab and wing down may be necessary.
So, I'm saying...you maintain the aircraft on the runway centerline with rudder during the takeoff roll, maintain wings level with roll control. After liftoff (not during) you relax the downwind rudder while continuing to maintain wings level with roll control.
Regardless of takeoff or landing, Airbus claims that if the aircraft is 'crabbing' on the runway in excess of 5 degrees, main landing gear damage may result.
Again, there is nothing special or magic about this aircraft. It flies the same as any other....just a different flight control system. The basics of flying still apply.
PantLoad
The aircraft needs to be aligned with the runway while it's on the runway. Exception is when crosswinds are 'strong' (as stated by Airbus), where crab and wing down may be necessary.
So, I'm saying...you maintain the aircraft on the runway centerline with rudder during the takeoff roll, maintain wings level with roll control. After liftoff (not during) you relax the downwind rudder while continuing to maintain wings level with roll control.
Regardless of takeoff or landing, Airbus claims that if the aircraft is 'crabbing' on the runway in excess of 5 degrees, main landing gear damage may result.
Again, there is nothing special or magic about this aircraft. It flies the same as any other....just a different flight control system. The basics of flying still apply.
PantLoad