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Lufthansa Hamburg

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Lufthansa Hamburg

Old 18th May 2008, 20:05
  #61 (permalink)  
 
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Here we go again...

Is there anything - literally *anything* that I can do or say not to have this argument all over again?

Just to reiterate:
- The computer does not make inputs the pilot does not ask for (it does not 'override' the pilot in that sense, never has). All it will do is attempt not to exceed a given bank angle

- There is no noticeable delay while the computer 'works out what to do' compared with hydraulic or even mechanical linkage.

- In the latest Boeings the yokes are not physically connected, they are backdriven by the computer.

- In this case the CP (monitoring pilot) did as he was trained and hit the override switch before taking control, so the pilots knew *exactly* who was in control at any given time.
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Old 18th May 2008, 22:20
  #62 (permalink)  
 
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Originally Posted by DozyWannabe
- In this case the CP (monitoring pilot) did as he was trained and hit the override switch before taking control, so the pilots knew *exactly* who was in control at any given time.
So, may I suggest you read again ... ?
Even better, have a good look to the graph ...
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Old 18th May 2008, 22:33
  #63 (permalink)  
 
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- In this case the CP (monitoring pilot) did as he was trained and hit the override switch before taking control, so the pilots knew *exactly* who was in control at any given time.
The FDR
http://www.bfu-web.de/nn_41542/DE/Pu...tin2008-03.pdf
page 26
suggests otherwise. The CP did hit the override switch and announced taking over control only after the F/O called for G/A after the wing made contact with the ground. Before there was dual input from both sticks, as you can see in the graphs of the FDR.
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Old 18th May 2008, 23:12
  #64 (permalink)  
 
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Best now would be to ask LH44 Captain what’s his view on Airbus sidestick philosophy ?
... did Hamburg change anything …?

To BFU credit, very nice to have published raw data. Whatever the language, the few FDR released say it all. Next step will be to have access to the flight animation.
I wish AAIB would be so informative …
I won’t mention BEA !

We could argue at length about the crosswind component, maybe it was slightly above, maybe just below, whatever, it was windy, it was cross side, it was gusty, but not that far off from the demonstrated values.
Can we blame the event on a gust ... or should we look at the inputs ?
At 50 feet AGL the copilot moved the side stick to the left and at the same time applied left rudder up to 28 degrees deflection within the next 5 seconds
… What do you expect from that ???

Clearly a lack of technique, nothing more.
BFU has to remind the basic stuff, probable brief or debrief for lesson #4 or #5 during private pilot training !

Lufthansa or other Majors seem happy to bring green green guys straight to the right seat of their airliners. For these guys it does represent a kind of real gift, but is it really ?

Cross wind handling only request time + practice, effective practice, when under supervision you go and manipulate these flight controls, you control and over control, you test the reactions, you test the limits, or at least your own limits … but can you afford that from the right seat of your Company Airliner in the day to day operation ?

Some like to say watching a good demonstration teach a lot … probably, but did we learn swimming by watching Mark Spitz ?
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Old 19th May 2008, 09:00
  #65 (permalink)  
 
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CONF, I was referring to the English report summary, which doesn't mention dual-input, only that the CP as PNF took control with the override switch. I'll read the BFU report when I get home this evening (my German's a little rusty and I don't want to misunderstand).
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Old 19th May 2008, 14:34
  #66 (permalink)  
 
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CONF, I was referring to the English report summary, which doesn't mention dual-input
??????????????

To me, DozyWannabe, the English report summary could not be more clear ... (translation looks pretty accurate, fluent German speaking will confirm ... ?)
The captain gave a 4.5 degrees right hand input at 15 feet AGL, the copilot reverted now her left side stick input to right as well.

At first touch down the bank angle was 4 degrees to the left, which increased to 23 degrees within the next 2 seconds, when the left main gear touch down again. Both captain and copilot gave a full right side stick input and the rudder was moved 14 degrees to the right.
International graph says even more ...
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Old 19th May 2008, 16:00
  #67 (permalink)  
 
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Before the description of the touches, it states clearly:
After the second touch down the copilot commanded "Go-Around" and increased thrust. The captain confirmed "Go-Around! I have control" and took control of the airplane, pressing the override button, to perform the go-around.
Meaning that at all points it was (or should have been) clear who was in control at any given time, so mechanically-linked yokes would have made very little difference.

I had a quick look at the graph and couldn't find anything relating to roll-rate at first glance. Like I said I'll have a proper look later.
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Old 19th May 2008, 20:49
  #68 (permalink)  
 
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To me it looks like;
- Yaw induced roll
- Combined with insufficient aileron into wind

http://www.xplanefreeware.net/morten/DIV/LH7.jpg

Rollrate increases from 4 to 14 deg/s when the FO
moves stick 5 deg in the "wrong" direction.
Also no sign of any gust on the heading curve which
is straight as an arrow in the same period (8,5 deg/s)

M
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Old 20th May 2008, 00:37
  #69 (permalink)  
 
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This is a nice presentation.
Just a bit surprised you didn't detail CAPT input ... as what you call CMD input in red is actually the sum of FO input in blue + CAPT input in black.
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Old 20th May 2008, 10:20
  #70 (permalink)  
 
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Tower reported winds at 28 knots from 300 degrees gusting 47 knots. The captain now inquired, how many go-around had been done and received the reply, that about 50% of approaches were abandoned in the last 10 minutes. ATC offered an approach to runway 33 at that point. The captain stated, that he wanted to attempt an approach to 23 first.
maybe this has been endlessly discussed before, but why does the tower initially cleares the aircrafts to rwy 23 with a 50%-chance of go arounds while on rwy 33 there were almost perfect nosewind-conditions?

... and why did pilots not request for the 33 when having wind up to 47knots from 300 degrees?
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Old 20th May 2008, 10:23
  #71 (permalink)  
 
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Also no sign of any gust on the heading curve which
is straight as an arrow in the same period (8,5 deg/s)
Question: Couldn't a gust hit in an angle from the side, that would not influence the yaw/heading directly?

What about vertical wind components such as an local upwind or small air eddy that could lift one wing?

Does the A320 FDR also record the indicated wind component such as displayed on the PFD? Would the sampling interval be small enough to allow for the reliable measurement of short strong gusts?
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Old 20th May 2008, 14:21
  #72 (permalink)  
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Interflug;
Does the A320 FDR also record the indicated wind component such as displayed on the PFD? Would the sampling interval be small enough to allow for the reliable measurement of short strong gusts
Almost certainly it does as it is the same information from the databus.

More accurately, with regard to the ND wind (wind isn't displayed on the PFD), the parameter for "what is displayed", (if programmed into the DFDR or QAR dataframe at all), would be a different parameter than the one used to record the actual wind info as sensed by the 3 ADIRS. To be very precise, the digital display is in degrees true while the wind-arrow is in degrees magnetic. In practical terms there would not be a difference between the two but the DMC's create the display, from the ADIRS data.

Wind direction and speed are usually sampled once per second. In response to a question above, this would likely be sufficient to record a sudden gust but not necessarily the gust's peak speed or exact direction at peak windspeed. The FODA QAR will very likely be doing the same as the DFDR but likely records far more parameters.
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Old 20th May 2008, 14:35
  #73 (permalink)  
 
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Looking at my above analysis one might start pointing a finger
at the FO. However, I've been stearing at the FO and CPT
input curves for a while and it seems to me that the CPT
also might be to blame here.

While the FO was supposed to be the pilot flying, it appears to
me that the CPT inputs confused the FO in the critical moments.

Especially the CPT's increasing into wind right aileron starting about 4 sec
before touchdown#1 and removing it about 0,5 sec before TD#1.

I'm no pilot, but to me it seems like a bad idea to undermine the FO
input's so that the FO does not get the feel of the external forces
working on the acf giving him (her) a false impression of what's
going on. Especially in these critical moments during flare and decrab.

What are the guidelines here? Is it ok for the CPT to interfere with the FO inputs. OR, you either let the FO fly or flip the switch if you are
unhappy with whats going on

M
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Old 20th May 2008, 14:39
  #74 (permalink)  
 
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XPMorten,
The Airbus with its FBW system is definitely not a 2 player game. Either you let the f/o get on with it or takeover making sure you hold the takeover button until they have completely relinquished control.
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Old 20th May 2008, 16:06
  #75 (permalink)  
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XPMorten;
I fully concur with Right Way Up's comments. Dual stick inputs is forbidden in Airbus SOPs. Dual input from the sticks is algebraically-summed. That means one stick's input will add to or cancel the other stick's input and no one will know what's going on - very bad work indeed and potentially dangerous as in this case.

"I have control" means "take your hand off the stick" - that's simultaneously backed up by pressing the priority takeover button in situations like these where immediate control is required.
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Old 20th May 2008, 16:20
  #76 (permalink)  
 
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Originally Posted by XPMorten
While the FO was supposed to be the pilot flying, it appears to
me that the CPT inputs confused the FO in the critical moments
That's very probable.

But you look a bit confused with the graphs:
Especially the CPT's increasing into wind right aileron starting about 4 sec
before touchdown#1 and removing it about 0,5 sec before TD#1
Except from 3 earlier interferences ... CAPT put right input only 2 seconds before first touchdown.
ROLL CMD by the Captain is the black line at the Anlage 3 top.
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Old 20th May 2008, 17:16
  #77 (permalink)  
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Anyone who calls that a 'near crash' is talking out of their a** and I'd ignore anything else they said

As a PPL, so lacking in line flying appreciation, I am genuinely interested how scraping the winglet on the runway and damaging it was not a near crash.

Presumably the aircraft was temporarily out of control whilst this happened and extrapolating the thought, its recovery was at least in part due to good fortune?

PS - please don't flame me, any clarification would be most interesting and appreciated
 
Old 20th May 2008, 17:31
  #78 (permalink)  
 
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CAPT put right input only 2 seconds before first touchdown
Right, was glancing at the scale on top of he chart which is another unit than the one
below - my mistake, 2 sec not 4.

M
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Old 20th May 2008, 18:21
  #79 (permalink)  
 
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A mix..

Input from both sidesticks mix and there is an avarage "uotput" to the flight controls. Crew is allerted of "dual input" though..

Wait for the final report before judging anyone, they survived wich is allways no 1, right!?
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Old 20th May 2008, 18:25
  #80 (permalink)  
 
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Cap10lobo,
I may have misunderstood you, but the control inputs are added not mixed. It is not an average output. i.e. Capt 5 deg/s left & FO 5 degs/s left will give a 10 degs/s rate.
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