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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

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Old 6th Jan 2013, 17:16
  #241 (permalink)  
 
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I do not mean to disrespect your walkarounds. Just after 447, i found a 300 and a 330 to stare at for extended periods. After marvelling at the exquisite look of the engines and general fit and finish of these beautiful birds, i focused on the pitot and AoA arrangement.

One conclusion was that the three appeared to be fit arbitrarily....more to accomodate plumbing than interface with airflow....

Were I Thales I would invest serious money in a statistical analysis of the turbulence encountered by AF447, up to and through the 'event'. To include sensory malfunction re: TCAS and W/S.

Cheers

Last edited by Lyman; 6th Jan 2013 at 17:24.
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Old 6th Jan 2013, 18:34
  #242 (permalink)  
 
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Lyman,

I think we are looking at this from different perspectives. You make some interesting points, but you may have read too much into my simplistic observation. I well remember getting very seriously iced-up in strato-cumulus on an (empty) C-47 in my misspent youth. We ended up with ice about an inch thick over the whole of both unheated windshields, and - when that had later melted enough for us to see through a hole in same - there was a stalagmite-like horn sticking forward about 6 inches from the frame between the two. The ice seemed to have propagated gradually backwards along both sides of the nose (I don’t recall noticing any ASI problems). When we eventually landed, there was still a circular area of glaze ice about 3 ft in diameter below the centre of the nose.

Now the characteristics of ice in strato-cumulus at an IAS of 120kts and TAT of just below freezing may be very different from those in cirrus or Cb at, say, IAS 280kts and TAT MS30C. And I don’t know how much research has been done into how much accretion there is on the nose in the latter circumstances. Although the heated windshields usually remain fairly clear (in my experience), except in heavy precipitation, you can see very little of the fuselage skin from the cockpit. It may be that the heated pitots and, usually further back, the AoA vanes can ice up before the unheated nose skin. But I doubt it.

When I ask if it’s a good idea for numbers 1 and 2 in each case to be positioned exactly symmetrically on the left and right sides respectively, I’m assuming that aircraft are normally flown with zero sideslip. Therefore, if both installations are serviceable and identical, they are likely to accumulate any ice in unison (unless the sun is shining from the side). You say that turbulence is required, but I presume that would even out in zero sideslip?

You suggest that the positioning of probes is arbitrary, which I doubt. But I’m sure you have noticed that the positions of numbers 1 and 2 mirror one another? And, when I ask about pre-AF447 accidents related to probes (heated as designed, and not damaged or blocked by any foreign object), I’m not limiting the question to Airbuses.

N.B.
Once again: are we discussing this on the wrong thread?


[EDIT]
Have reposted this on the Rumours & News A330/A340 EAD (AoA PROBES) thread. Thanks Turbine_D.


Last edited by Chris Scott; 7th Jan 2013 at 00:24.
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Old 6th Jan 2013, 18:47
  #243 (permalink)  
 
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Chris Scott,

I am going to repost my latest on the other thread and remove the posting on this thread.
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Old 6th Jan 2013, 19:46
  #244 (permalink)  
 
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The nose does not describe a lateral in sideslip, necessarily. Since relative airstream can emanate from a 360 circle from in front, there are vertical slippages to account for (Probe2?). That 1 and 2 are opposite and co-planar, we can assume the airflow position in stable air is a design consideration. So why a placement of Standby below the 1, 2 plane? 'Anomalous design' imo..

From BA 038, I have pointed out common mode as an enemy of redundant design. This suggests that anomalous design can counter mere "redundancy" design.

I have been discussing micro granular water Ice, not "accreted" water Ice.

I don't say that turbulence is a requisite for ice packing of probes, only that it is statistically more likely to be present in these events.

A working theory is that micro granular water Ice is less responsive to Pitot heat solutions than is accreted water ice, to include supercooled water as the progenitor...

In BA038 thread, I proposed: one engine RRTrent700, and one GE90. Since it turned out that the RR had designed insufficiencies in its ability to melt Ice in fuel, the supposition is available that 038 may have made the runway, and prevented hull loss if utilising a GE90 as one of two engines.

Only a what if. It strikes me that pitot or vane design is not germane to the discussion of Airbus 'system design' problems.

Systems fail, Ice is only one possible bubble in the cheese. What is of critical import is what the systems do when facing a failure.

Apparently, there are bubbles installed at the factory. And flight test continues....With occupants.

Last edited by Lyman; 6th Jan 2013 at 19:54.
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Old 6th Jan 2013, 21:36
  #245 (permalink)  
 
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Originally Posted by flash2002
For those who think that the protections are gentle or gradual and that time is available... Thats especially for you dozywannabe. I just received some more info regarding the incident from my company:
Thanks - I'm going to wait for the report, but at the same time I don't think it's fair to pin this on the protections - there's something screwy with the AoA probes, and despite not being prepared for it - and in the climb phase, where any false Alpha Prot trigger would be most problematic - the crew managed to resolve the situation.
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Old 6th Jan 2013, 23:19
  #246 (permalink)  
 
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Pin it on the protections? What brought the aircraft in a 12 degree nose down pitch with 9400fpm within 10 seconds of the AOA probes becoming faulty?

Wait dont answer that.... the protections.

If this airbus a330 would have been equipped with BUSS, switching off those ADR's would have put the aircraft under manual control with AOA information displayed on the PFD's... What would have happened in that case???

dozy you need to get your pink glasses off, this type of aircraft needs a normal control switch to turn off the protections when they are clearly not controlling the aircraft in an acceptable manner.

12 degrees nosedown is NOT ACCEPTABLE! Havimg to switch of ADR's to regain control over some renegade computers is not acceptable.
Boeing might have problems on their aircraft that need resolving, but this needs to be resolved on airbus!

Last edited by flash2002; 6th Jan 2013 at 23:22.
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Old 6th Jan 2013, 23:52
  #247 (permalink)  
 
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As I said, I want to wait for the report before drawing conclusions - the fact is that this is but one incident, apparently caused primarily by faulty AoA vanes. Mandating a sweeping change of the kind you're describing to a system that has worked more-or-less faultlessly for 24 years and heaven knows how many flight hours is overkill.

This is not about "pink" glasses, this is about wanting all the facts to be known before letting the usual suspects argue for a single incident to settle old vendettas.
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Old 7th Jan 2013, 00:26
  #248 (permalink)  
 
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Originally Posted by flash2002
dozy you need to get your pink glasses off, this type of aircraft needs a normal control switch to turn off the protections when they are clearly not controlling the aircraft in an acceptable manner.
I simply think that's the most reasonable step the manufacturer should take, for the good of all.

Originally Posted by DOZY
Mandating a sweeping change of the kind you're describing to a system that has worked more-or-less faultlessly for 24 years and heaven knows how many flight hours is overkill.
The sweeping change has to be mental more than anything. Airbus simply needs to admit that the protections can make a mess too and a simple tool should be provided to the crew to help them to stop the possible mess to go too far.
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Old 7th Jan 2013, 00:46
  #249 (permalink)  
 
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Originally Posted by flash2002
I just received some more info regarding the incident from my company
Do you have any written document on the event, or is it more informal information, do you think you could get more info soon ... What you report here for sure matches the seriousness of the published EMERGENCY AD + AIRBUS AFM TEMPORARY REVISION but I find it very annoying still no one has publicly stated its intention to investigate the event ...
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Old 7th Jan 2013, 03:28
  #250 (permalink)  
 
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but I find it very annoying still no one has publicly stated its intention to investigate the event ...
Just a reminder ..
http://www.pprune.org/7591225-post91.html

Last edited by jcjeant; 7th Jan 2013 at 03:29.
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Old 7th Jan 2013, 06:16
  #251 (permalink)  
 
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Wink

Not sure what you are asking CONF?

It comes from an explanatory document on the event, what to look for, what to do etc etc. We have got quite a few busses flying around with conical plates.
It comes from our management of that's what you are asking.

Dozy,

Waiting for the research is all fine. But the fact is that the protections will suddenly put you in a dive if some systems fail. This is not limited to any single system, some events cannot be catered for. But switching off ADR's can only be a temporary measure and would be unnecessary if a simple guarded switch would be installed to kill the protections.
Another fact is that applying unwritten procedures, like switching Off 3 ADR's could lead to other unexpected results in the heat of the moment, such as activating BUSS.

What other undiscovered potential issues exist that can lead to unrecoverable spurious protection activation? What other computer controlling flight surfaces can't be switched off, none I believe? Why can't the protections be switched off.

Sure protections are nice but clearly the technology isn't ready yet for unmanned passenger transport.
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Old 7th Jan 2013, 07:37
  #252 (permalink)  
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Again I have to say that while what the 'protections' did to the flight path is worrying enough, the fact that full back stick would have no effect is the real elephant.
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Old 7th Jan 2013, 08:53
  #253 (permalink)  

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"Switching the protections off" may not help all much if crews have little experience of "manual" flying.

(Dropping out of Normal Law in the face of UAS merely gave the crew of AF447 a chance to stuff it up terminally. )

But what do I know?

Mac

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Old 7th Jan 2013, 09:15
  #254 (permalink)  
 
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First of all, if you only have never flown a Boeing, it is almost impossible to enter into this debate with any degree of understanding. The original starter of the thread, 737Jock, is indeed an Airbus pilot who has flown both the 737 and A320 series of aircraft. In my experience he is rare among Airbus pilots in preferring the Boeing to the Airbus, having done more than a year on the aircraft. Nonetheless, he is a sharp guy and is completely entitled to his view, but as I say it is a minority opinion in the Airbus community.

Regarding AF447, the only people to blame there were the pilots in the same way that the pilots of the Turkish Airlines 737 that crashed at Amsterdam were to blame there. Both faced reasonable technical failures that they did not notice, failed to act upon and subsequently stalled the aircraft because they could not recover the situation. I am not a 737 fan, but I recognise that whatever insidious failure those pilots faced, the ultimate cause of the crash was pilot error.

Now onto this latest incident. What 737Jock is absolutely correct in saying is that a situation can arise in the rarest of circumstances (one such known incident in the history of the Airbus, recovered without a single casualty) where you can lose control of the aircraft in the vertical plane despite making correct inputs to attempt recovery. On the surface of things a mad situation - as indeed it is. What I would have to counter that argument with is that a far worse situation arose in the past with 'rudder hardover' in the 737 - icing causing problems with with rudder actuator on a handful of occasions which led to the loss of a number of aircraft with many casualties. No one said that the aircraft was unsafe, when arguably it was. Overall the fly-by-wire system on the Airbus has saved way more lives than it has lost and has been a fantastic addition to airline safety.

For reasons I am at a loss to explain the 737 soldiers on like Grandfather's old axe with 6 new handles and 5 new heads. It was obsolete 20 years ago and yet there is talk of a 737Max which has to have raised undercarriage to fit in the engines - bizarre. Driven by a desire to avoid a new type-rating Boeing have been forced to make do with an old banger which is poshed-up to look like something new. Give me an Airbus any time.
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Old 7th Jan 2013, 10:52
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Quote from Alexander de Meerkat:

“For reasons I am at a loss to explain the 737 soldiers on like Grandfather's old axe with 6 new handles and 5 new heads. It was obsolete 20 years ago and yet there is talk of a 737Max which has to have raised undercarriage to fit in the engines - bizarre. Driven by a desire to avoid a new type-rating Boeing have been forced to make do with an old banger which is poshed-up to look like something new. Give me an Airbus anytime.”

(How rare to see someone with the temerity to slight the sacred cow...)

Do you mean type CERTIFICATION? My understanding (and, no doubt, yours also) is that Boeing has for so long clung to the “3” purely in order to evade the latest certification requirements for all-new types. Now that the A320 has been certificated for 25 years (this February), AI may be starting to benefit from “grand-pappy” rights in a comparable fashion, but the requirements of 1988 were streets ahead of the early-1970s (or was it late-1960s?).

Last edited by Chris Scott; 7th Jan 2013 at 10:54.
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Old 7th Jan 2013, 11:25
  #256 (permalink)  
 
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Merci for the reminder jcjeant.
In the meantime, is it also possible that the State of the Manufacturer has a droit de regard and could investigate on its own ?
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Old 7th Jan 2013, 11:43
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Originally Posted by Alexander de Meerkat
What I would have to counter that argument with is that a far worse situation arose in the past with 'rudder hardover' in the 737 - icing causing problems with with rudder actuator on a handful of occasions which led to the loss of a number of aircraft with many casualties. No one said that the aircraft was unsafe, when arguably it was.
But it was before the Internet time ... the situation would be very different today.
In the meantime, no one is saying the Airbus is 'unsafe' at least not me, the request is to improve the situation based on more than valuable argumentation.
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Old 7th Jan 2013, 11:50
  #258 (permalink)  
 
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Conf_iture and jcjeant,

Based on what little we know, it would be remarkable if the BEA did not ensure there was a formal investigation. It would be interesting to know the minimum vertical-g during the pitch-down, and whether anyone was hurt. IIRC, serious injury or substantial damage = accident, which would mandate an investigation. in the absence of either, it would still be bizarre for them not to publish some kind of bulletin.
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Old 7th Jan 2013, 12:01
  #259 (permalink)  
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Lets not forget that both boeings and airbusses are tools. Tools to get the job done and both will get the job done.

Yes I prefer boeing over airbus, although I would miss the table incredibly. My ideal aircraft would really be a mix of the two. Taking the best from both worlds. But that will never happen...

The 737 rudder hardover problem was rare, but it was identified and countermeasures were taken.

For some reason though people are not willing to accept that there are flaws in the airbus design. It's absolutely bonkers that a rare situation can develop where the pilots are not able to recover from an abnormal attitude with normal control inputs.

Now I don't know if it is technically possible, but why is there no normal law with reduced protections available (so pitch g-load, and roll-rate with autotrim but no other protections except for g-load) on the flick of a guarded switch.

But even then why oh why is it so hard to accept that having to turn off ADR's is not normal!

I really don't care if boeing has had this or that incident, let boeing fix their own aircraft. It's not an excuse for continueing the status quo on airbus aircraft. Not being able to control the aircraft through normal control input is a serious threat however rare it may be.
As an airbus pilot I want to see a proper solution, the main problem here is not icing of AOA probes. Cessna's don't have AOA probes and they fly perfectly without them!
The real problem is that the computers can try to dive the aircraft into the ground if faulty inputs are received, and that these computers cannot be controlled by normal input. Even if the icing of probes is fixed, it still doesn't guarentee that no faulty inputs will exist that can make the situation go out of control.
There needs to be a simple remedy to deactivate these protections, switching off ADR's can only be a temporary measure. We are trusted with engine fire controls, why not with a guarded switch to deactivate protections?

In my mind the guys on that EVA A330 are brilliant guys, they got the aircraft on the ground safely, but had they been lower or not as sharp on the day... It's a very very serious incident.

As ADM said I am a minority in preferring the 73 over the bus. But I also think that is for a great part due to the more spacious flightdeck and the table. All in all its a nicer environment to do a 4-sector day in then the 737, which in layout is a bit cramped. But flying wise I enjoy and prefer the 737.
To be honest I'm a bit sad that boeing is sticking with the same design for the 4th time with the 737MAX. I would have rather seen a new design based on the 787.

But if nobody wants to order that new design and we leave the choice to SWA, what do you expect?

Last edited by 737Jock; 7th Jan 2013 at 12:18.
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Old 7th Jan 2013, 12:36
  #260 (permalink)  
 
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Originally Posted by 737Jock
The 737 rudder hardover problem was rare, but it was identified and countermeasures were taken.
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.

Coincidentally, CONF iture says it would have been different had it happened the time of widespread internet. The 'net wasn't as widespread back in the late '90s and early '00s, but the case certainly was discussed online back then - and very vociferously as I recall!

For some reason though people are not willing to accept that there are flaws in the airbus design.
Not true - no-one's saying the design's perfect, but I don't think it's unreasonable to expect more detailed information before introducing changes to the system that would be expensive, yet unproven in terms ofwhether it would improve safety or not.

It's absolutely bonkers that a rare situation can develop where the pilots are not able to recover from an abnormal attitude with normal control inputs.
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.

That was after two confirmed fatal crashes as a result of the issue, and possible others. Right now with this AoA vane issue we have a single rogue incident which has not as yet been properly reported on, with no fatalities and no word of injuries or damage - and yet calls are coming in for a wholesale change to the design. Why should things be one way for Boeing and another for Airbus?

Last edited by DozyWannabe; 7th Jan 2013 at 12:37.
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