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LH A320 Rough Landing @ Hamburg

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LH A320 Rough Landing @ Hamburg

Old 4th Mar 2008, 09:05
  #181 (permalink)  
 
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a hero?
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Old 4th Mar 2008, 09:16
  #182 (permalink)  
 
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"Converted" to the A319 from 737 about 10 mths ago.
I have about 3000 hrs on 733, 734,735,737 & 738, and only around 500 hrs on the bus.
So I am not the most experienced around......
With all the technicalities aside (FBW, roll rate, software etc.) the bottom line is the bus is just harder to land well in gusty conditions.
Most of the time (said with due reference to my thus far limited experience on the bus) it ends up allright, but sometimes leaves you with the sensation that is was'nt all you that did this.

It is not unsafe, I think its just the lack of tactile feedback that leaves you with a feeling, that is very much different to the feeling of landing a conventional aircraft. All the aircraft I have flown from the PA28 up to the Airbus have been conventional - thus basically requiring the same technique, all of a "sudden" comes a beast that IMHO is superior in any other aspect than the last 50 ft on a windy and gusty day.
The experienced guys in my present company says that it takes some time getting used too, but after a while you just do.

All that beeing said, you can allways GO-Around.

Lets wait and see what the BFU comes up with in the end......

OY
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Old 4th Mar 2008, 09:20
  #183 (permalink)  
 
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satos:
I was wondering could it be an airbus inherent problem as boeings seem to handle these conditions much better.
You *could* read that into it, but it wouldn't necessarily be accurate. As many more knowledgeable than me have confirmed, Airbus control logic means that you handle the sidestick in a different way in crosswind conditions than you would a yoke in a Boeing, as the sidestick commands roll *rate* directly, whereas the yoke commands aileron deflection. Therefore cross-control will feel very different between types - the word is "different", not better or worse.

I'm wondering whether some of these incidents are a subconscious reversion to older control methods in moments of stress.
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Old 4th Mar 2008, 09:30
  #184 (permalink)  
 
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Bernd

Everything you said is correct but

Stick centered means, bank angle stays where it is up to 33 degrees, or returns to 33 degrees if it was more.
Is not quite the full story with the stick central if a gust upsets the attitude the bus will hold the new attitude and the pilot must still use the stick to return to wings level. Keeping the stck central does not mean the wings will be leveled for you only that you have asked for not change in roll rate (rate = 0)
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Old 4th Mar 2008, 09:32
  #185 (permalink)  
 
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Not wanting to qualify the pilot and by no means implying of being the better one, this attempted landing is not really a success, much less a heroic act.

The final seems steady, with a distinct drift. On short final the pilot loses the centreline. This happens quite often with the larger aircraft as pilots tend to line up the cockpit and forget to do this with the center gear. If this happens a GA should be flown. Reason being is, if you correct late to continue, the last track is amended, away from the runway track. Perfectly visible here as the aircraft slides towards the upwind edge of the runway. This amendment then coincides with the flare and decrab. Out of this situation a (at least partial) decrab becomes necessary to align with the runway track. Mostly such a decrab will be more than usual and accompanied with a roll input to compensate. At the same time the AB logic kicks in with its own roll command (to keep the latest vector, which was not the one desired, see above). The double input on the roll will be slightly too big, leading to the pilots reaction to unroll. The wing comes up and will get additional lift from the wind. This, with the somewhat bigger rudder input, leads to a unwanted drift to downwind, demonstrated here again, as the aircraft ends up on the downwind edge of the runway.

Lesson: With a Airbus it is even more vital to stay on centreline (the one of the gear). Any deviation on short final is hugely difficult to undo, as the computer tries his part as well and in such brief time frames you end up fighting each other. A decrab technique is nice in steady wind conditions, but very tricky with gusts, thus the AB recommendation not to do so. I know these landings hurt the pride of all pilots, but if the technology does not allow it, go for the uncomfortable landing instead of the dangerous hit and GA.
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Old 4th Mar 2008, 09:39
  #186 (permalink)  
 
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I'm wondering whether some of these incidents are a subconscious reversion to older control methods in moments of stress
That could be if the aircraft was over banking into wind and they touched with the into wind winglet. In this incident, and a very similar one in Bilbao only a couple of months ago
http://www.pprune.org/forums/showthr...=iberia+bilbao
the aircraft banks aggressively to leeward ie not enough into wind aileron, not enough conventional technique. This problem starts when the rudder is used to straighten the aircraft this creates an associated (and predictable) banking moment unfortunately once the windward wing begins to raise the problem quickly gets worse because the wing catches the ever greater exposed surface, the leeward gear touches down and provides the wrong momentum.

The only solution I can see is to pro-actively flick the windward wing down as you squeeze the rudder to straighten the aircraft in the flare. The FBW needs a little helping hand here as it is obviously not quick enough to correct the wing drop associated with the rudder input.

Last edited by calypso; 4th Mar 2008 at 09:49.
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Old 4th Mar 2008, 09:42
  #187 (permalink)  
 
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I bet a helicopter pilot wouldn't consider landing in conditions like that, he'd divert immediately due to good airmanship and judgement hehe
But as a helicopter you dont need a runway, in most cases you land into the wind, especially in high wind conditions you dont have to accept xwind....

skadi
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Old 4th Mar 2008, 09:46
  #188 (permalink)  
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Rudder stress

Have not read all the posts on here but it seems most comments are about cross wind limits, get home itus,Boeing v Airbus and are you a stick and rudder man.

My first thoughts on watching the video are releif after watching it climb away but then turned to thoughts of airframe stresses.

After the AA A300-600 accident where the fin parted company with the aircraft after a boot full of rudder,I do hope Lufthansa will carry out NDT testing of the fin attachment lugs on this A320. The rate of yaw and the speed the aircraft reacted must have put an awful strain on the airframe.

Although the speed in this instance was somewhat less, the violent activity displayed can only have pushed the flight envelope to the limit.

Lastly I would like to say well done to the crew for not losing the plot at the critical moment which could so easily have happened and ended in disaster. The arguments about whether or not an approach should have been made are a seperate issue, but once a committed you have to go with the live situation.

I guess this is a classic demonstation that compared to the power of nature, the difference between a large airliner and a small single is such an insignificant one.

Coop & Bear
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Old 4th Mar 2008, 09:50
  #189 (permalink)  
 
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Come on guys, this is all getting a bit in depth.

We just land the thing. Look outside, squeeze the drift and keep the wings level. Sometimes a little cross control is needed but so what?

All being said about the theory and laws, its still an aircraft, I remember the number one rule - fly the aircraft.
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Old 4th Mar 2008, 10:25
  #190 (permalink)  
 
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F4F - Cool, you don't have to agree with me! I have not killed anyone yet after 10 years of "conventional" aircraft and airbus landings!

When I started flying the airbus I did some line-training with a VERY experienced airbus driver. On one of my first days with this guy we had some quite strong and gusty winds and I asked him for some "airbus" hints. His said "Don't think airbus, think landing an aircraft. You have landed before haven't you??!" with a big grin on his face.

Looks like the worst weather is over for this time anyway.
Happy landings!

CP
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Old 4th Mar 2008, 10:25
  #191 (permalink)  
 
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AB logic

GMDS, you wrote:


At the same time the AB logic kicks in with its own roll command (to keep the latest vector, which was not the one desired, see above).



How does this AB logic work? May you give some more details?


Thanks
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Old 4th Mar 2008, 10:27
  #192 (permalink)  
 
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Georgey - 100% Correct!
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Old 4th Mar 2008, 10:55
  #193 (permalink)  
 
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Angel Any difference?

Much controversy about "direct law" and "roll control".

But think about it ...

Direct law (or direct control linkage) :
Right stick, proportional right aileron up.
Assuming no secondary effect (or secondary effects being properly corrected) : right aileron up => roughly proportional roll rate to the right.=> Roll rate in proportion to stick defection in normal conditions.

Airbus "roll control" law :
Right stick, proportional right roll - whathever secondary effects might happen. Perhaps the electronic processing of the signal would take a few milli seconds?

I see no reason, in theory, for a lack of manoeuvrabilty due to the Airbus "roll law" ...

Stick to the right = roll to the right - looks like a very pleasant feature!

Now, if the same computer can also garantee that "rudder to the right" = yaw to the right ... then the aircraft remains a "stick and rudder" flying machine ...

Actually, the Airbus recomandations for crosswind landings are quite close to the flying technique that is recommanded for a Piper or a Cessna.

But ... are we sure that we remain "stick and rudder" pilots?

Some years ago, I had to check out a F-16 fighter pilot on a C172 ... Obviously, that guy was no longer proficient whith the use of the rudder, and totally unable to properly land a small aircraft in any crosswind.
He was a good pilot and he quickly caught the trick. But the fact is that he was instructed never to cross controls on the F-16, in order "not to confuse the computers" - his own words.

I would suggest, maybe ... that airlines pilots, from time to time, take a refresher course in handling a Piper Cub in some crosswind ... ? Just to make sure they remember that there is a rudder overthere ...

Last edited by Bis47; 4th Mar 2008 at 11:38.
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Old 4th Mar 2008, 10:56
  #194 (permalink)  
 
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AndyGov

I am a simple jockey and no AB freak, so i stand to be corrected or hanged by the lobby, but here is my understanding of the logic:

The AB is flown with the "demand" philosophy. You demand a track/vector/movement with the stick and the computer executes it (you let the stick go after the demand input, the demand is maintained and must be cancelled with a opposite demand). On final the demand law fades out to direct law on the pitch, meaning the stick input gets back to conventionally executing directly what input you give, irrespective of the outcome of the command versus space (you let the stick go, the elevators go back to neutral). However the roll axis remains in the demand mode. If you kick in some rudder, the computer senses a deviation in space contrary to the initial demand, and wants to correct it thus applying some roll.
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Old 4th Mar 2008, 10:59
  #195 (permalink)  
 
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Hero, by definition, is someone who does something heroic or outstanding.
I would suggest that the LH pilot was doing exactly what he is paid to do. Fly the aircraft. As did the Iberia pilot in Bilbao, incidentally.
The fact that the wing-tip touched the runway in one instance and not in the other makes no difference. The correct decision was made, to Go-Around, land and go home for dinner and a glass of wine.
Whatever happened that day is not cause for me or indeed any of you so-called professionals to post judgement the pilot. He was landing within the limits of the aircraft and de facto, his own as he is a LH Captain. The fact that a gust caught him out at the critical point in the landing does NOT mean, most emphatically, that he is anything less than a competent and well qualified pilot.
I would just say this to some of you; were you flying last week in the extreme weather that obtained over large tracts of Europe? If not, then please refrain from posting an opinion about the qualifications of the pilot.
How many years have you been flying as the handling pilot, in all and every weather condition imaginable, and perhaps some unimaginable, since you obtained that coveted license? Enough to be sure that you can land in those conditions that the LH Captain experienced last week?
Enough to be sure that you would have made the decision to divert to another airport much sooner? And where would you have gone? The whole of Europe was suffering the same met conditions last week so the closest, longest runway will always be the preferred choice. (Unless you happen to know of one into wind!)
All this talk of direct law and squeezing crab off at the appropriate time amount to nothing more than a lot of hot air. As has been mentioned, it's an aircraft, fly the airplane and land it as well as you can in the circumstances.
Extreme weather, which it undoubtedly was, make for extreme situations and I, along with a few other enlightened souls on this thread, salute the pilot for his quick reactions and obvious skill in retrieving a critical situation.
If you tell me he shouldn't have got himself into such a critical situation in the first place then all I can say to you is, show me the pilot who never misjudged a situation and I will show you a rank amateur, fair-weather air head who thinks he is superior to his peers. Believe me, if you think that, then God help you and God help us all.
I would rather trust my life with him than some of the so-called 'experts' who frequent these pages.
Well done, that man!
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Old 4th Mar 2008, 11:16
  #196 (permalink)  
 
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Out of interest, it would seem that the secondary effect of applying rudder would tend to increase the bank angle and drop the into-wind wing onto the tarmac. Does the Airbus computer take account of this and do anything to mitigate the effect?
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Old 4th Mar 2008, 11:23
  #197 (permalink)  
 
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I always understood that sidestick in the middle in Normal Law meant zero rate of roll commanded. So in theory once you have levelled the wings and centred the sidestick the wings will remain level. When you start getting close to the ground (50 FT RA) you go into direct law, which means you now have to work at keeping the wings level in the conventional way. Maybe this changeover in Law is where you might get caught out should a wing drop. Up to that point you have been used to not having to make a correction (in roll) to keep the wings level but after you have to correct.
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Old 4th Mar 2008, 11:26
  #198 (permalink)  
PBL
 
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2001 Bilbao hard landing accident in gusty conditions

I just realised that we did not have the 2001 Bilbao accident report in our compendium of Computer-Related Incidents with Commercial Aircraft but it is there now, for anyone who wishes to read it.

PBL

Last edited by PBL; 4th Mar 2008 at 11:38.
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Old 4th Mar 2008, 11:38
  #199 (permalink)  
 
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Rubik,

I watched the video on the TV News. It looked to be an extremely professional recovery with no apparent warning. One moment the aircraft appeared stable, right wing down and on course for a safe touchdown.

Moments after the accident the aircraft was again in a stable and level attitude but to the left of the runway and in the recovery.

It appeared to be well handled, skillfully recovered and flown off safely.
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Old 4th Mar 2008, 11:39
  #200 (permalink)  
 
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Fireflybob,
There is no change in roll control until touchdown. See post 184.
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