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

[flash2002]

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.

[BOAC]

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.

[Mac the Knife]

"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

:\

[Alexander de Meerkat]

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.

[Chris Scott]

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?).

[CONF iture]

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 ?

[CONF iture]

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.

[Chris Scott]

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.

[737Jock]

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?

[DozyWannabe]

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?

[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.

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.

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.

:mad: the BUSS, fly the attitude!

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.

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

[jcjeant]

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

[Turbine D]

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-full-text/ntsb/aircraft-accident-reports/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.

[DozyWannabe]

@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 (http://www.b737.org.uk/rudder.htm)

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.

[737Jock]

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.

[Lyman]

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....

[737Jock]

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!

[DozyWannabe]

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?

[Lyman]

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.

[DozyWannabe]

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.

[Clandestino]

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 :mad: 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.

[Kimon]

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.

[DozyWannabe]

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)

[Lyman]

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.

[HazelNuts39]

BUSS is not useful above FL250

[737Jock]

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.

[Kimon]

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.

[737Jock]

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.

[Kimon]

@ 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?

[HazelNuts39]

Pitots and static ports blocked?

[Kimon]

Yes, AOA, Pitots and Stats blocked.

[CONF iture]

Where did you get such information Kimon ... ?

[Cool Guys]

A couple of posters seem to be using 737 rudder hard over issue to lessen the severity of this AB issue. The 737 rudder issue was obviously a very serious issue with lives lost etc but it should not be used as any form of excuse for another safty concern. There is a trace of the A verses B debate in this which should have little relevence when debating serious safty issues.

[Kimon]

Sorry got my wires crossed:
Airspeed was working normally though αlpha PROT was in an unusual place and thus pitot and static not blocked.

[HazelNuts39]

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.Based on what little we know, just to give an idea, my estimate of minimum vertical-g during the pitch-down:

http://i.imgur.com/4Xcwz.gif?1

[Chris Scott]

Thanks (as always) HN39,

Your figure seems to be about +0.35g? Even allowing for the approximate nature of the data you're working with, does it seem probable that no one went ballistic? (No pun intended.)

[HazelNuts39]

@Chris Scott:

Yes, IMHO that would seem probable.

[DozyWannabe]

From the EAD (emphasis mine):

An A330 aeroplane experienced a blockage of all Angle Of Attack (AOA) probes during climb leading to Autopilot (AP) disconnection and activation of the alpha protection (Alpha Prot) when Mach number increased.

If in climb phase, would we not be talking about a significantly different scenario than cruise, given that it would be starting from a higher positive pitch and thrust setting?

[Lyman]

Would it also be likely below 25,000 feet, involving a potential 'BUSSt'?

Does the Alpha prot bounce the A/P? Does BUSS put the a/c in Direct?

IOW, how does the flight logic know the probes are frozen to deselect autopilot?

Doesn't Direct, once active, stay active for the duration of the flight?

Dozy?

[Chris Scott]

Those who are not following the thread on probe icing may nevertheless wish to see this post by A33Zab, quoting David Learmount:

http://www.pprune.org/rumours-news/502079-a330-a340-ead-aoa-probes-8.html#post7618295

[HazelNuts39]

If in climb phase, would we not be talking about a significantly different scenario than cruise, given that it would be starting from a higher positive pitch and thrust setting?
I don't think it would be significantly different. Other information indicates the entry into alpha-prot occurred near top of climb. The flight path angle would then not be so large that it would change the scenario significantly. Furthermore, the V/S of 9400 fpm together with the likely TAS and the pitch of -12 degrees yields an AoA close to the zero-lift AoA of -1 degree, IOW corresponds to close to zero 'gee'.

Does the Alpha prot bounce the A/P? Does BUSS put the a/c in Direct? IOW, how does the flight logic know the probes are frozen to deselect autopilot?
Alpha-prot bounces the A/P. The system does not know that the erroneous AoA is due to blocked sensors.

[737Jock]

Chris Scott, that article on the other thread is incorrect. You wrote:

Those who are not following the thread on probe icing may nevertheless wish to see this post by A33Zab, quoting David Learmount:

I posted the following on the other thread:

Totally agree, the AFM TR should be followed!
But alleged 'total loss of pitch control' is besides the truth.

The article is actually incorrect in that sense. The OEB is structered around recognizing 3 different scenarios, however if you do not recognize these scenarios and alpha prot engages, you WILL loose all pitch control until you turn of 2 ADR's to force alternate law. The proof is in the pudding:

The A320 memory items from the OEB (my bold):
At any time, if the aircraft goes to an unmanageble pitch down attitude despite continuous deflection of the sidestick in the full backward position (in case the flightcrew missed the below symptoms or delayed the application of one of the below procedures):
One ADR........Keep on
Two ADR's......Turn off

So if you recognize the symptoms on time, stabalize the flightpath and keep one adr on.
If you are too late, alpha prot will engage and you will loose all control over pitch which can only be resolved by the memory items.

The A330 crew lost all control, but they regained it by turning ALL adr's off which forced alternate law.


So there you have it, airbus themselves say you can loose all pitch control! It's really not helpful to try to convince people otherwise. David Learmount is unfortunately incorrect.

In order to be in line with the OEB this is what it should read:
The crew turned off all three air data reference (ADR) units. This action took the aircraft out of normal flight law into alternate, which de-activated the stall-protection system. Then the pilots levelled the aircraft and reviewed the situation and decided to divert. During descent, Airbus notes, the angle-of-attack vanes became unstuck once more.

[Lyman]

HazleNuts39 :ok:

Yes, the logic is not there to decide to switch off the AutoPilot...

The paper is disingenuous, for it announces first A/P switched off, then AlphaProt..

It could be a mistake, but it is glaring.

The crew and the airplane must wait for Mach to trigger the Protection.

It is like an "Ambush", a Gotcha..... Not unknown in this aircraft, its talent for the surprise....

A corollary... Bonin applied aft stick, and accomplished a frustrating lack of response (in his mind). We dismiss his actions as silly, but when the aircraft itself mimics Bonin, (though opposite in Pitch direction), we defend the machine, though it is quite obviously hazardous in its performance?

Both aircraft EVA And AF are victim to similar scenario... One lived to tell it in person...

It takes prejudice to dismiss the potential for disaster in the one, and accept with disapproval the actual accident accomplished in the other....

330 -1

Bonin -1

A Tie

[Chris Scott]

Hi 737Jock,

My purpose in providing a link to A33Zab’s post, in which he quoted David Learmount’s Blog, was – as I said - simply to draw attention to it: not to endorse David’s report. Perhaps I’m not the only one who is occasionally finding difficulty in following two PPRuNe discussions running more or less in parallel on the same subject, although this thread has a wider remit than the other one.

David Learmount’s piece is dated December 7th, and would have been written in good faith with the information available at the time. However, as also happens often on PPRuNe, he has put the description of the event in quotation marks without specifying the source. It certainly appears that his source reported the main events in the wrong order.

The news to me is that it seems to confirm the probes unjammed later, presumably during the descent to their alternate airfield.

You say:
“David Learmount is unfortunately incorrect.
In order to be in line with the OEB this is what it should read:
The crew turned off all three air data reference (ADR) units. This action took the aircraft out of normal flight law into alternate, which de-activated the stall-protection system. Then the pilots levelled the aircraft and reviewed the situation and decided to divert. During descent, Airbus notes, the angle-of-attack vanes became unstuck once more.”

Sounds good to me.

[CONF iture]

Learmount is in direct touch with Airbus ... ?

11300ft in the climb
250kt
minus 12C
AOA probes stuck at 5 deg
then FL310

but where are all the other relevant data ... starting with the date of the event ?

As noted by 737Jock, the article is misleading and has IMO a taste of damage control.

"Airbus says this is the only know occurrence of this type, but it is reviewing the design of its heated sensors and their resistance to icing."
That's not what I'm looking for. I want Airbus to develop the most simple procedure to give back control to the crew in the shortest time when the protections do silly things.

[jcjeant]

starting with the date of the event ?
I suggest ... 18 November 2012

[TTex600]

"How safe is (Airbus) fly by wire?"

FBW, apparently quite safe.

Protections, statistically safe.

Could be far safer.

The 320 was and is a techno marvel, but continued development would appear to be lacking.

TTex, not a Boeing fan either. I'd rather sweat in a DC9.

[DozyWannabe]

The 320 was and is a techno marvel, but continued development would appear to be lacking.

That's not strictly true. Development and refinement of the FBW systems has continued significantly in the 24 years since the aircraft went into service, but there are limits to how much can be altered with the A320 itself without breaking type commonality. Hence the A320NEO programme, presumably.

As Chris Scott alluded to earlier, the fact that the original A320 was subject to later and more stringent certification requirements than the original B737 - along with the fact that it was designed around a more modern control and avionics setup - should mean that more significant changes can be applied to the NEO than were possible with the NG.

That said, so much preparatory work went into R&D of the systems that ended up in the original A320 (much of which significantly pre-dated the official project inauguration in 1982) that the groundwork it laid out was correct and proven (in engineering terms) to a degree that was unprecedented at the time. Also, because of the digital nature of the flight systems, a lot of work went on "under the hood" in the years between then and now that would not be obvious to those who weren't inclined to dig deep enough to find out.

TTex, not a Boeing fan either. I'd rather sweat in a DC9.

Interesting how people gravitate to different types. Maybe I'm of the wrong generation, but the DC9 always struck me as a bit flimsy in appearance and backward in engineering terms. This could also be coloured by my soft spot for the BAC 1-11 (which I thought was a lovely design and built like it was hewn from granite but let down by the choice of engine). ;)

[TTex600]

Interesting how people gravitate to different types. Maybe I'm of the wrong generation, but the DC9 always struck me as a bit flimsy in appearance and backward in engineering terms. This could also be coloured by my soft spot for the BAC 1-11 (which I thought was a lovely design and built like it was hewn from granite but let down by the choice of engine).

So any anecdotal comment/opinion regarding Airbus demands an immediate response from you demanding facts to back up the assertion, yet you have no problem offering your own opinion about the DC9.

Can't say that I'm surprised.

[DozyWannabe]

Not at all sir, just offering a light-hearted comment! The birds we prefer (and the reasons we love 'em) are a personal thing for the most part, and I respect your choice even if I don't necessarily agree. :)

I swear I'm not the dour contrarian some take me for...

[Lyman]

Dozy you are so disingenuous, I cannot keep a straight face.

It's gotten so slippery I put tire chains on my keyboard.

[DozyWannabe]

I'd hoped that the winking smiley on the end of the paragraph (not to mention that the paragraph itself was entirely off-topic) would be a clue that I wasn't being entirely serious...

[rogerg]

This could also be coloured by my soft spot for the BAC 1-11 (which I thought was a lovely design and built like it was hewn from granite but let down by the choice of engine).
At the time the only engine available for the 1-11 was the spey as due to exchange regulations. It was not possible to purchase non UK engines.
An attempt to re engine with the Tay later on did not come to fruition.

[DozyWannabe]

At the time the only engine available for the 1-11 was the spey as due to exchange regulations. It was not possible to purchase non UK engines.
An attempt to re engine with the Tay later on did not come to fruition.

At the risk of going too far off-topic, I won't carry on past this post - but I was thinking of the RR Medways that were slated for the original version of the Trident (and sadly stayed on the drawing board when BEA 'Speyed' the Trident)... :8

There was a popular bit of piloting scuttlebutt that said the DC9 had the same "oomph" with an engine out that the 1-11 had with both working...

[wozzo]

Dozy, Lyman, TTex, it's nice to have the old gang back. Please, continue bitching! Where's Clandestino?

[DozyWannabe]

Dozy, Lyman, TTex, it's nice to have the old gang back. Please, continue bitching! Where's Clandestino?

Couple of pages back, but speaking for myself I'm really hoping we can avoid the hamster wheel this time!

[Chris Scott]

Yes, the One-Eleven-500 (the stretch) was ill-suited to operate charters out of Spain to the UK in the summer. Using the Spey’s water injection increased the RTOW by less than 400kg, IIRC, and meant loading about 120kg (?) of de-mineralised water. Overall improvement in available payload: 2or 3 pax. And after my time they even throttled it with a useless hush-kit...

TTex600,
Earlier on this thread we were discussing go-arounds, and the natural pitch-up tendency of aircraft with under-slung jet engines as G/A thrust is applied. (This tendency is, as you know, eliminated on Airbus FBW a/c in pitch-normal and pitch-alternate laws, but not in direct law.)

The 1-11 and its big brother, the VC10, gave little pitch-up because of their tail-mounted engines. Can you comment on the DC9, and if possible compare it with any under-slung jets you’ve flown with conventional flight controls?

[roulishollandais]

Where's Clandestino?
Clandestino clandestinat? :suspect:

[roulishollandais]

Development and refinement of the FBW systems has continued significantly in the 24 years since the aircraft went into service,but therearelimitsto how much can be altered with the A320 itself without breaking type commonality. Not only breaking type commonality : Changing a FBW system seems easier than conventional, but the greater complexity of FBW design increases the risks and number of tasks exponentialy :{ with complexity of systems. Stabilisation of the computerised system is still a greater necessity for Safety.