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How safe is (airbus) fly by wire? Airbus A330/340 and A320 family emergency AD

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How safe is (airbus) fly by wire? Airbus A330/340 and A320 family emergency AD

Old 7th Jan 2013, 13:23
  #261 (permalink)  
 
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Thanks flash2002, for providing some more info. Now, does anyone know when and where did the serious incident happen? Just curious who is investigating.

From the scant data available, it seems we are dealing with simultaneous identical failure of three independent sensors. There is extremelly slim chance the simple (no matter how aerodynamically sophisticated is its blade) swiveling AoA vane can be frozen solid by external icing. It might get unbalanced, it might start reading erroneously but to get the bearing frozen solid, significant moisture must be present at the base, below the aeroplane's skin.

If had to place my bet now, I'd put my money on Perpignan-style washing.

Originally Posted by flash2002
Switching off those 3 ADR's could have been a major problem, making things worse.
Oh, sure. If they switched off ADRs following problems with AoA and then followed erroneous AoA information while cheerfully ignoring their attitude then they would be in real trouble.

the BUSS, fly the attitude!

Originally Posted by flash2002
12 degrees nosedown is NOT ACCEPTABLE!
It resulted in how many deaths? Injuries? How much damage to property?

Now I have your attention, I'm not saying it is acceptable (whatever criteria we might use to define it) just that it was recoverable.

Originally Posted by 737Jock
having to turn off ADR's is not normal!
Maybe that's why we call it "Abnormal"?

Last edited by Clandestino; 7th Jan 2013 at 13:25.
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Old 7th Jan 2013, 14:11
  #262 (permalink)  
 
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Smile

Hi,
Clandestino
Thanks flash2002, for providing some more info. Now, does anyone know when and where did the serious incident happen? Just curious who is investigating.
Seems you have missing to read some messages
So far BEA stated that it will be no investigations about this incident
"The decision to open and conduct a safety investigation on this event belongs to the Japanese authorities (state of matter) or Taiwan (state operator). They have decided not to initiate an investigation, it is the reason why you can not find a trace of the event on the BEA website. '
Go .. nothing to see there

Last edited by jcjeant; 7th Jan 2013 at 14:13.
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Old 7th Jan 2013, 14:16
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Dozy,
t took almost ten years, a time during which Boeing submitted their own internal report to the FAA which blamed the pilots of UA535 for the crash. The PCU design was such that it could affect any of the 737s in the air at any time between 1967 and 2002.
and
But that's exactly what happened with the 737 hardovers, and the aircraft was left flying with a known fault for nearly ten years.
If you are going to tell a story and represent it as fact, you need to tell the whole story.
The NTSB investigated the UA 535 accident for nearly 2 years and could not confirm the cause of the crash in their report issued in 1992. In September 1994, USAir 427 crashed in Pittsburgh. The NTSB investigated this accident for 4 1/2 years before concluding a rudder malfunction was to blame. The final report was written by the NTSB in 1999. The NTSB concluded part of the problem and cause was lack of reliable redundancy in the rudder control system. The NTSB also blamed the FAA for dragging its feet on implementing enhanced flight data recording capabilities on Boeing 737s, which hampered the investigations.
Subsequently, the NTSB went back and revised the UA 535 final report in 2001. The three NTSB reports can be found here to refresh your memory:
http://libraryonline.erau.edu/online...s/AAR92-06.pdf
http://www.ntsb.gov/doclib/reports/1999/AAR9901.pdf
http://www.ntsb.gov/doclib/reports/2001/AAR0101.pdf
These are the reports that count. Can you provide a link to Boeing internal report you cited?

Keep in mind, today there is a lot more data recorded, some realtime, than there was 20+ years ago and therefore addressing a problem becomes possible in a shorter time frame.
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Old 7th Jan 2013, 14:19
  #264 (permalink)  
 
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@jcj - The BEA cannot start an investigation if the Japanese and Taiwanese don't want them to, nor can they involve themselves in an ongoing investigation without being invited to do so.

@TD - The NTSB investigators were certain there was a problem with the rudder somewhere, but were stymied by the fact that they couldn't precisely prove what the problem was. As for the Boeing viewpoint (prior to PCU thermal shock discovery):

The Rudder Story

The Boeing View

Charlie Higgins, a Boeing vice president who heads up airplane safety and performance for Boeing, said the rudder control units from the 737s in the Pittsburgh and Colorado Springs crashes were both thoroughly examined as a part of the NTSB's accident investigations.

...

The company points to pilot error in the Pittsburgh crash, suggesting the pilots may have mishandled the plane in reaction to the turbulence, with the first officer inadvertently holding the left rudder pedal to the cockpit floor as he and the Captain pulled back on the control stick to break their plunge. They blame a rogue wind in the United Airlines crash and a mis-rigged yaw damper for the Eastwind incident.

Last edited by DozyWannabe; 7th Jan 2013 at 14:25.
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Old 7th Jan 2013, 14:24
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It took almost ten years, a time during which Boeing submitted their own internal report to the FAA which blamed the pilots of UA535 for the crash. The PCU design was such that it could affect any of the 737s in the air at any time between 1967 and 2002.
So thats the allowable timeframe then dozy? 10 years because boeing didn't fix it earlier.

But that's exactly what happened with the 737 hardovers, and the aircraft was left flying with a known fault for nearly ten years. The workaround there involved maintaining a higher approach speed, but it didn't solve the underlying problem and there was no guarantee that it would save the aircraft if the crew did not correctly diagnose the fault in time.
I agree that it took too long, want to repeat the same thing again?

What is there to investigate, it is known and proven that the alpha prot protection can lead to a complete loss of control due to faulty input. Fixing the aoa won't guarentee a faultless input. Thats a design flaw with respect to thinking that the protections will always be correct with regard to actual flightpath.
Maybe the solution is as easy as allowing the pilots to press the a/p disconnect button to override the protection.

Oh, sure. If they switched off ADRs following problems with AoA and then followed erroneous AoA information while cheerfully ignoring their attitude then they would be in real trouble.

the BUSS, fly the attitude!
That worked very well on AF447 no, it would be kind of hard to ignore what BUSS is telling you since it will be all over the PFD. In any case it won't make things easier since BUSS is all AOA related.

It resulted in how many deaths? Injuries? How much damage to property?

Now I have your attention, I'm not saying it is acceptable (whatever criteria we might use to define it) just that it was recoverable.
Quick thinking made it recoverable, let's not pretend that 12 degrees ND is anywhere in the normal flightregime.
I know that abnormal attitude law will trigger at 30 degrees ND, but would it in this case? And isn't 12 degrees ND already far outside the normal?

Maybe that's why we call it "Abnormal"?
You really believe that turning off 3 ADR's or 2 ADR's because of a stuck AOA vane is a proper solution? Whiping all airspeed data from one of the pilots, while in a dive!

Offcourse its abnormal, but the solution in itself seems to be a complete patch up which is abnormal.

Last edited by 737Jock; 7th Jan 2013 at 14:26.
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Old 7th Jan 2013, 14:30
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Dozy

Protected uncommanded dive, with full aft stick...


Where was AutoTrim when they really needed it?


See a problem?

Note your ref to Boeing blaming any but a/c.. Run in the industry?

To wit:
AF447.....
Imagine that BEA had no report, that only stick position aft and dive data was recorded. Airbus would be so screwed....

Last edited by Lyman; 7th Jan 2013 at 14:42.
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Old 7th Jan 2013, 14:33
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The FAA View

The FAA argues that no one will ever know the cause with any certainty, so it has focused on making the plane safer.
Which is actually the most important thing, the plane was made safer!

The NTSB View

Dennis Crider, chairman of the NTSB’s Aircraft Performance Group, told the board members “A rudder reversal scenario will match all three events,”

The Boeing Co., hotly contests such a finding, saying there is no physical evidence that supports rudder reversal scenarios in the three incidents.
In this case there was only circumstantial evidence, for which they could only found the rudder-hardover as an explanation that fitted all 3 crashes.
Boeing dragged their feet for obvious reasons, since there was no hard evidence. No matter how much they dragged their feet they were forced to change the ruddersystem! It certainly doesn't deserve any compliments! A good example where the fear of hefty fines and lawsuits stopped an aicraft from becoming safer in a timely fashion.
So why use this example exactly guys? I want my airplane to be as safe as possible, without arrogance pride or potential lawsuits getting in the way.

With airbus we all know that alpha prot will override any pilot input if it gets the input signals to do so! It's a known fact!

Last edited by 737Jock; 7th Jan 2013 at 14:37.
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Old 7th Jan 2013, 14:48
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Originally Posted by 737Jock
You really believe that turning off 3 ADR's or 2 ADR's because of a stuck AOA vane is a proper solution? Whiping all airspeed data from one of the pilots, while in a dive!
It's not a solution, it's a short-term workaround while the problem is investigated (albeit internally under EASA supervision) and fixed - just as the increased Vapp was in the 737 case.

Given that Airbus FBW pilots are now being trained to deal with the equivalent of double ADR failure and initial upset in the wake of AF447, could that not be considered to mitigate the risk somewhat?
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Old 7th Jan 2013, 14:48
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Use caution when lumping FAA and NTSB together...

EVA: Why was PF so aggressively pulling?

All he had to do was experiment? He must have forgotton his FCOM:

Abnormal + Abnormal = Normal Sorted


Dozy, you sound like Boeing.

Last edited by Lyman; 7th Jan 2013 at 14:53.
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Old 7th Jan 2013, 16:25
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I don't see how - Boeing "hotly denied" there was a technical fault, I didn't. Neither did Airbus or EASA.

Furthermore, Boeing's denials came in the wake of two fatal crashes and a near-miss. So far in this case we have no fatalities and very few details of the incident itself. I have to wonder that if flash2002's information is correct, why has there been very little in the way of media attention? Normally an incident of the severity he's claiming would cause the press to be awash with reports of screaming passengers, deadly plunges and narrow avoidance of schools and orphanages.
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Old 7th Jan 2013, 17:36
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I am faced with really tough decision; whether to believe PPRuNer who claims there will be no investigation (and has spectacularly demonstrated ignorance of the territorial application of aviation safety investigations by berating BEA) of this very serious occurrence or EASA that claims that investigation is ongoing. Dang.

In any case it won't make things easier since BUSS is all AOA related.
My point exactly. Unlike flying attitude+power BUSS is not universally applicable for any kind of air data mess-up. Sorry for making sarcastic allusions that I considered to be understandable to any line pilot.

You really believe that turning off 3 ADR's or 2 ADR's because of a stuck AOA vane is a proper solution?
Who gives a about my opinion? EASA considers it to be proper patch-up until it is understood how in the world it could happen in the first place, doesn't care about me considering it to be good enough and won't listen to your objections if all you do is post them on PPRuNe. Give 'em a call, you might be right. Or they can spare a minute to explain some things you don't understand or appreciate and they are obliged to.

You have nothing to lose.
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Old 7th Jan 2013, 18:40
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BUSS Saved EVA

The Post-EVA AD is still TR (Temp. Rev.) so have they - Airbus - solved this or will solve this soon?
I agree that this is a most serious incident and I am most certain had this A330-343 not had BUSS (standard on the A330-343) the outcome would have been rather nasty.

Last edited by Kimon; 7th Jan 2013 at 18:43.
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Old 7th Jan 2013, 18:56
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Again - BUSS works from AoA data - how could it have played a positive role when all the AoA data was false?

(It's undeniably useful in circumstances where the pitot-static system is FUBARed though)
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Old 7th Jan 2013, 19:05
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So "Are we BUSS minus?" Or, "Are we BUSS plus?"

Buss is AoA reliant, won't it make things worse? The A/C degrades with BUSS to Alternate Law. Which one? 2b? Roll Direct?

The faster it goes, the faster it goes. What of Autotrim? ND? Override with three pulls per degree?

Bit of a handful.
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Old 7th Jan 2013, 19:24
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BUSS is not useful above FL250
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Old 7th Jan 2013, 19:42
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Dozywannabe, I work for the same company as flash2002 amd AdM. The information he provided is the same as what I received. It comes from management.
Basicly its an extended brief, clearer then the OEB, on what happened, what to expect, what actions to take and what not to do.

I can only assume that they got the info from airbus or EASA. We have quite a few aircraft in our fleet affected. I trust that the information is correct.

BUSS only functions below FL250. But BUSS is completely reliant on AOA information, so if amything was displayed it would be false information.

Last edited by 737Jock; 7th Jan 2013 at 19:45.
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Old 7th Jan 2013, 19:46
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BUSS

The BUSS procedure for UAS are different from non-BUSS.
The BUSS procedure is now the norm for non-BUSS as well should there be any blocked AOAs, Pitots and Static Ports.
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Old 7th Jan 2013, 19:51
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No Kimon, BUSS procedure is to turn ALL ADR's off.

Blocked AOA is to turn 2 ADR's off, in order not to activate BUSS.
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Old 7th Jan 2013, 20:34
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@ Jock737 thanks for that correction.
In the EVA case, all AOAs, Pitots and Stats were blocked.
Which procedure is used in which order?
Which Mem Item has the absolute priority regarding the differing 3 respective procedures which are mutually exclusive i.e. do 1 right, get the other 2 wrong?
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Old 7th Jan 2013, 20:59
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Pitots and static ports blocked?
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