A330/A340 EAD (AoA PROBES)

[BEagle]

An EAD has just been released following an issue experienced by an A330 crew:

The EAD includes the narrative:

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.

The blockage of two or three AOA probes at the same angle may cause the Apha Prot of the normal law to activate.

Alors, qu'est que c'est un 'blockage' of an AOA probe? Does that mean blocked with foreign matter / ice / whatever, or is it some quaint Franglais referring to a stuck probe?

The EAD also states:

Under normal flight conditions (in normal law), if the Alpha Prot activates and Mach number increases, the flight control laws order a pitch down of the aeroplane that the flight crew may not be able to counteract with a sidestick deflection, even in the full backward position.

Followed by the "No Sh*t, Sherlock" statement:

This condition, if not corrected, could result in reduced control of the aeroplane.

You don't say!

Another piece of Froggldegook comes in the actual procedure and states:

CAUTION RISK OF UNDUE STALL WARNING

I've heard of spurious stall warnings and have even experienced spurious stall ident and stick push at 500 ft in a much older 4-jet, I've taught 'incipient' stall recoveries and 'fully developed' stall recoveries, but never in 40 years have I ever heard of an 'undue' stall warning....

Just WTF do they mean?

[safelife]

Once again it becomes clear that every Airbua FBW aircraft pilot should know how to get out of the normal law.
As it seems the only safe way out of such mess.
Regrettably Airbus will continue to refuse to tell us.

[nitpicker330]

Easy, reach up and turn off all 3 PRIMS.

You're now in in direct mode via the 2 remaining SECS. :ok:

However that would be a last ditch effort!!:{

[swh]

An EAD has just been released following an issue experienced by an A330 crew:

This only applies to the newer aircraft with the new AoA probe that is mounted on a raised area away from the skin.

I've heard of spurious stall warnings and have even experienced spurious stall ident and stick push at 500 ft in a much older 4-jet, I've taught 'incipient' stall recoveries and 'fully developed' stall recoveries, but never in 40 years have I ever heard of an 'undue' stall warning....


Considering every aircraft flying is at risk of undue stall warnings, I am surprised that you have not heard of it (sensor issue, radome damage, bird strike, ADC issue etc). An example would be the 777 incident out of Perth https://www.atsb.gov.au/media/24550/aair200503722_001.pdf

[NOLAND3]

Safelife - I sincerely hope you are not a A3xx driver! You have multiple way's of getting the machine into Alt or Direct law easily within a few seconds, all of which you can find in the FCOM.

As stated in the above post - Switch of multiple PRIMS or ELACS, or FAC 1+2

Not ideal in the slightest however not some big AB secret and something you should most definitely already know...

[BEagle]

'Undue' is defined as 'to a level which is more than is necessary, acceptable or reasonable'. As in 'use of undue force'

So, is an 'undue stall warning' something which meets this definition? Or is it yet another froggldegook mangling of English in this context?

I presume they mean a 'spurious' stall warning?

[SLFandProud]

Does anyone seriously not understand what it's saying?

If so, you should probably not be in command of anything more dangerous than a pencil sharpener.

[beardy]

I have been following this shimmering thread that expands and contracts with time, with interest. There seems to be an almost obdurate unwillingness to understand the text of the EAD and of the Airbus concept of design and operation of aircraft. I have no problem with either, but then I operate Airbus aircraft and have done so for many years, and am familiar with the way they do things. It's not difficult, nor is it inherently dangerous, it is comprehensible and is designed to be so worldwide.

[CONF iture]

Considering every aircraft flying is at risk of undue stall warnings, I am surprise that you have not heard of it (sensor issue, radome damage, bird strike, ADC issue etc). An example would be the 777 incident out of Perth
I do agree with your comment, except that, if i read correctly the report, the activation of the stall warning and stick shaker devices was justified in the Perth 777 case.

Safelife - I sincerely hope you are not a A3xx driver! You have multiple way's of getting the machine into Alt or Direct law easily within a few seconds, all of which you can find in the FCOM.
2 things i would like to see then :

A published Memory Item to get rid of undesirable protection activation
A single black guarded switch to trigger DIRECT LAW


Anyone to post the AD please ?

[ASRAAM]

In aviation it is frequently said that an experienced aviator is one that uses his exceptional knowledge in order to avoid having to use his exceptional skill.

The correlation to this thread is that I am able to understand (generally) what the people at airbus write, but I have to work at it sometimes.

The cynic in me suspects that it is not just a poor translation from French into technical English but a deliberate attempt to minimise adverse media coverage at the expense of clarity.

An undue warning seems much less emotive than a spurious warning when read as a newspaper headline!

[Dan Winterland]

''Anyone to post the AD please ? ''



http://www.caa.co.uk/docs/33/20121204EASAAD20120258E.pdf

[Microburst2002]

RISK OF UNDUE STALL WARNING is prompted by the ECAM in several malfunctions

The new bulletin tells us to switch off two ADRs to get in Alternate Law.

We don't want Direct law, direct law is dangerous

[CONF iture]

Amazing stuff, thank you.

Now, curions to read the exact :
"Blocked AOA probes" emergency procedure included in Airbus AFM A330 Temporary Revision (TR) TR293 issue 1 ?

[Squawk7777]

Or is it yet another froggldegook mangling of English in this context?

Exactly what kind of English are you referring to?

spectacles or yoke?
tailplane or stabiliser?
throttle or thrust lever?
VAT or VREF?
coaming or glareshield?
to dump or jettison?

What does it matter whether the AoA probes are blocked or stuck? All the pilot needs to know is that they are not working the way they should.

RISK OF UNDUE STALL WARNING : with a little bit of imagination it is not difficult to figure that one out.

[mm43]

@CONF iture;

Airbus A330/A340 AFM TRs can be found at:-

http://ad.easa.europa.eu/blob/TR293approved.pdf/EAD_2012-0258-E_2
http://ad.easa.europa.eu/blob/TR294approved.pdf/EAD_2012-0258-E_3

[Microburst2002]

OK465

Roll direct is hardly a dangerous thing. Pitch alternate is Ok, no danger at all.

Pitch direct is dangerous, however. Many people thing that reverting to Direct law is like reverting to a conventional flight control system, but pitch direct is nowhere near conventional.

[CONF iture]

Thank you mm43.
I would be curious to hear more about the initial event and how the guys dealt with it ?

That Temporary Revision should also clearly specify how the procedure is meant to give back control to the pilots when protections do activate on unreliable data.
Give back credit to the pilots.

Many people thing that reverting to Direct law is like reverting to a conventional flight control system, but pitch direct is nowhere near conventional.
How is that different !?

[BEagle]

Squawk7777, many of the items to which you refer have specific meanings and are not synonymous.

As for ...with a little bit of imagination it is not difficult to figure that one out.

pilots should never need to do such a thing in response to QRH directions - which must be clear and unambiguous.

[beardy]

pilots should never need to do such a thing in response to QRH directions - which must be clear and unambiguous.

Ah but somewhere in all this the real world intervenes. Which is where common-sense (which in turn is based on experience) intervenes. I agree the QRH ought to be unambiguous, but, being written by mere humans, it occasionally is, no more so than for situations not dreamt of by the compositor. Which is where the Captain, using his experience, skill, judgement, imagination and flare, earns his money. And, should he survive, gets criticised by desk bound pedants.

[Machinbird]

Roll direct is hardly a dangerous thing. Pitch alternate is Ok, no danger at all. True if you make minimal & smooth control inputs and your scan is working.

Not so true if you are ham handed, surprised, tired, and bumping along at night in the weather (particularly if you fly for a certain French airline it seems.):}

[Lonewolf_50]

beardy, it would seem to me that during type rating training, you'd learn the terms and ask questions about what some of them mean, espectially if you were converting from another airframe.

I'll even bet that such discussion goes into training. ;)

[beardy]

Lone wolf, I do believe that you are correct. Some who contribute here, so freely, are so involved in training and are so far away from operations that they seem to have lost sight of reality.

[Right Engine]

RISK OF UNDUE STALL WARNING is prompted by the ECAM in several malfunctions

The new bulletin tells us to switch off two ADRs to get in Alternate Law.

We don't want Direct law, direct law is dangerous

So your comment implies flying an aircraft that needs to be trimmed and with manual thrust is dangerous. Quick - Ground all Boeings!!

[beardy]

So your comment implies flying an aircraft that needs to be trimmed and with manual thrust is dangerous.

No it doesn't, now stop being silly.

[CONF iture]

Why silly ... ?
You should maybe question the initial comment first :
We don't want Direct law, direct law is dangerous

[beardy]

Silly because you confused Direct Law with Boeing; there is no relevance. If you believe there is then you do not know what direct law entails, which, from your rather glib definition, I don't believe you do: you seem to (deliberately) misunderstand and in proposing the grounding of all Boeings you are being rather silly and possibly trying to be provocative. (Did I misunderstand your exclamation mark for an emoticon?)

I don't really have much to add to the technical discussion here since the contributors seems to be people who are unfamiliar with and are antagonistic to the aircraft. However, I don't think that Direct Law is dangerous, just different.

[Phalanger]

So your comment implies flying an aircraft that needs to be trimmed and with manual thrust is dangerous. Quick - Ground all Boeings!!The issue people are trying to get at is that when you drop you're already in a higher than normal pressure situation and now flying a new beast. It can not be helpful considering all the details changes one must now deal with cognitively as opposed to autonomously. Take for example someone who ended up constantly pulling back on a stick which would have different results in each mode.

[Squawk7777]

pilots should never need to do such a thing in response to QRH directions - which must be clear and unambiguous.

BEagle,

if the QRH directions must be clear and unambiguous then there's not really a need for pilots to sit in the cockpit. They can be replaced by software, AI, Otto Pilot etc.

Having said that, I have been involved in incidents where thinking (shock, horror!) and system knowledge were required. Not all incidents and problems can be foreseen by design engineers. Decision making and interpretation are two of many factors that justify humans sitting and piloting airplanes (or aeroplanes if you wish ;) ).

[Cool Guys]

I think what BEagle was referring to when he said

“pilots should never need to do such a thing in response to QRH directions - which must be clear and unambiguous.”

is documentation should be clear and unambiguous as much as possible, sure it is impossible to get things perfectbut a pilot has enough to learn and figure out without making things more difficult than necessary by providing loose documentation. Technical writers really have a big responsibility and they should have a good understanding of the words and be able to convey concepts clearly and unambiguously.

[Microburst2002]

Quote:
Originally Posted by M2002
We don't want Direct law, direct law is dangerous


Imagine O'Leary told airbus to make a cheap airbus 320 version, without normal or alternate law. So they would be much much cheaper.

Well, he would be dissapointed. They cannot certify such aeronautical aberration.

The Airbus in direct law is much different than a 777 in direct law. It doesn't even have a proper pitch trim. We have a THS wheel, but we have no stick forces that we can trim.

In direct law you can fatally and brutally overstress the airframe with inputs that would not seem dangerous in normal or alternate law. In a 777 I believe you would still need to exert very high forces on the yoke to do that, in direc law.

Airbus Direct law is highly undesirable... Because it is dangerous. In the simulator, after a go around with a dual hidraulic... How does it feel? Conventional? No way! Normal and alternate feel conventional. Direct is more like a 767 with the yoke artificial feeling inop. MANOEUVER WITH CARE is not a silly ECAM line. You better manoeuver it with care!

With the trim wheel you don't trim forces, but you have to ease back the sidestick to neutral as you move the wheel, resembling the action of trimming. It is just like the microsoft FS with a joystick? That is NOT conventional. It doesn't feel right for a pilot instinct.

[BEagle]

Cool Guys - precisely!

As for calls to provide an Immediate Direct Law option, that would be extremely undesirable for many flight phases as the sidestick lacks conventional force / displacement artificial feel simulation. However, an Immediate Alternate Law option would perhaps not be unreasonable, rather than a workaround involving the deliberate deselection of air data reference units.

[beardy]

Under what circumstances do you think you would wish to select Alternate Law and which flavour of Alternate Law do you think you would like?
Bearing in mind, of course, all those circumstances when the aircraft will give you Alternate Law automatically.

[BEagle]

Under what circumstances do you think you would wish to select Alternate Law and which flavour of Alternate Law do you think you would like?


Since most of the uncommanded A320/330/340 flight path excursions which have been reported seem to have involved incorrect sensor information being faithfully acted upon by Normal Law protection features, the minimum necessary action to countermand such spurious events before an extreme event is reached would perhaps be appropriate - so probably Immediate Alternate 1 ?

Far better though to eliminate any source of sensor failure in the first place.

[beardy]

So this is what you would like to happen:

Low speed stability
At low speed, a nose down demand is introduced in reference to IAS, instead of angle of attack, and alternate law changes to direct law.
It is available, whatever the slats/flaps configuration, and it is active from about 5 kt up to about 10 kt above the stall warning speed, depending on the aircraft's weight and slats/flaps configuration.
A gentle progressive nose down signal is introduced, which tends to keep the speed from falling below these values. The pilot can override this demand.
Bank angle compensation is provided.
In addition, aural stall alert (“STALL, STALL” synthetic voice then cricket) is triggered at an appropriate margin from the stall condition.
The PFD speed scale is modified to show a black/red barber pole below the stall warning.
Vα prot and Vα max are replaced by Vsw (stall warning speed).
The α floor protection is inoperative.
High speed stability
Above VMO/MMO, a nose up demand is introduced to avoid an excessive increase in speed.
The pilot can override this demand.
The high speed protection symbol (VMO + 4) disappears.
In addition, the overspeed warning (VMO + 4 or MMO + 0.006) remains available.
Pitch attitude protection
Lost.

If I read you correctly you are advocating that with a faulty sensor input leading to the aircraft believing it is going too slowly, you would like it to revert to Direct Law. IMHO that is a not a very good idea. Far better to have angle of attack protections in Normal Law.
Perhaps you have tried your theories out in the sim?

[BEagle]

...a faulty sensor input leading to the aircraft believing it is going too slowly...

Such an event would surely require the 'Unreliable Air Speed' procedure, rather than a deliberate selection of Alt Law.

The situation which raises greater concern is faulty AoA signalling, resulting in spurious pitch excursions. Under such circumstances it might be better to inhibit AoA protection by deliberate crew action, before the aircraft reaches an extreme attitude.

[CONF iture]

Airbus Direct law is highly undesirable... Because it is dangerous.

In direct law, the pilot uses the THS conventionally to fly in trim.
Use small control inputs at high speed, since in direct law the controls are powerful.
MANEUVER WITH CARE
The sidestick is directly coupled to the controls via the computers, but without any of the stabilization feedbacks. In effect, this law turns the aircraft into a conventional aircraft
The flight crew must fly the aircraft carefully at all times. Control is precise, but there are no protections.

Those are comments from the FCOM, hardly synonyms of 'DANGER', but applicable to any aircraft.

When is the last time you flew direct law, in the sim at least ?

[Microburst2002]

I know what the FCOM says, but the airplane in direct law is NOT turned into a conventional airplane. Because conventional airplanes must have stick forces that provide pilots with aerodynamic feedback. Without that, you are in the MIrcrosoft FS, which is not conventional at all.

Nearly every sim I fly direct law, for a while. The difficulty and danger of Direct Law is more apparent in the GO AROUND. Typically we find it in final approach, after L/G DOWN. The airplane is almost in trim and it takes only minor inputs and trim settings to have the job done. However, all that changes in case of go around. Then, it is difficult to switch my mind to direct law, so I find myself releasing the sidestick (springloaded to neutral) after inputs, which equates to make brisk inputs back and forth, like jerks. If more angle the input had, the worse. Imagine a conventional 767 where there is no feedback from the yoke, but it will return to neutral if you release it.

With practice you can fly direct law quite decently, but you have to actively think so that your instinct and habit doesn't put the airplane at risk. And, as I say, you could not certify an airplane with a direct law system without artificial feeling in the stick.

That FCOM reference repeats a lot that you fly with care, that you are not protected, that controls are powerful, that you use small inputs... That sounds like "hey be careful" to me, and therefore there is danger.

Dangerous means that you can get in trouble easily and you have to be careful to stay out of trouble. It doesn't mean you have to panic and pray. I will never revert to direct law on purpose as a reversion to conventional, because it is not a reversion to conventional, in the first place. Normal law is much more conventional than direct law, in my opinion.

The bulletin procedure is just what the situation needs. You get rid of the rogue sensor inputs and keep flying almost normally (alternate law is very much like normal law, except for some protections).

[beardy]

Since most of the uncommanded A320/330/340 flight path excursions which have been reported seem to have involved incorrect sensor information being faithfully acted upon by Normal Law protection features, the minimum necessary action to countermand such spurious events before an extreme event is reac:*hed would perhaps be appropriate - so probably Immediate Alternate 1 ?]

The situation which raises greater concern is faulty AoA signalling, resulting in spurious pitch excursions. Under such circumstances it might be better to inhibit AoA protection by deliberate crew action, before the aircraft reaches an extreme attitude.

This represents a welcome change of tone from your mocking first post. However, it seems that you think that Airbus have not considered, risk assessed nor trialled what you propose. I do not know if they have or not, but I do know that their resources and knowledge and greater than mine or yours and that their investment, both in cash and reputation, is much more than yours or mine. Since I operate the aircraft, I have to trust them and their judgement. This does not stop me questioning, but each time I have questioned Airbus there has been a satisfactory response. If your are an operator or client they are quite willing to help, perhaps that would be a more suitable channel for your scepticism and offers of suggestions.

[BEagle]

I know what the FCOM says, but the airplane in direct law is NOT turned into a conventional airplane.

The significant change is from manoeuvre demand to attitude demand. However, the control system doesn't provide any stick force per G gradient, neither does it provide any Q-dependent feel. So perhaps not all that conventional?

beardy, I note your post. However, I remain somewhat exasperated by the....let's call it 'unusual' English used by Airbus in many of their publications.

[CONF iture]

However, all that changes in case of go around. Then, it is difficult to switch my mind to direct law, so I find myself releasing the sidestick (springloaded to neutral) after inputs, which equates to make brisk inputs back and forth, like jerks. If more angle the input had, the worse. Imagine a conventional 767 where there is no feedback from the yoke, but it will return to neutral if you release it.
But the Question is why would you release it in the first place as long as a pressure on it is necessary to maintain a requested attitude ?

Normal law is much more conventional than direct law, in my opinion.
Which brings me to the next question :
What's your experience really outside that airbus ?

With practice you can fly direct law quite decently, but you have to actively think so that your instinct and habit doesn't put the airplane at risk.
You don't put your airplane at risk if your own way is by adopting brisk inputs back and forth, at most you make people sick in the back.

IMO you clearly need to reevaluate the basic behind piloting but also your notion of DANGER.

[Microburst2002]

Direct law is not an attitude demand, it is an elevator angle demand, so it is more like an AoA demand.

The reason to release the sidestik, erroneously, is because in normal law, what we do all the time, is to trim the airplane in flight path by releasing the sidestick. So when we mistakenly we do that, in direct law, it is very nasty for the airplane, pax and everyone. After many years in the bus that is what happens to many, even if they have thousands on conventional types.

The flight path stable, trimless airplane is very easy and natural to fly, but different to the conventional speed stable, trimmable airplane. When you are used to the A320, direct law is unnatural. It wouldn't be if it had artificial feeling. Being spring loaded to neutral makes it absolutely non natural, non conventional. If you come from 10,000 hour flying the 737 you will get to normal law like a duck to water, but not so with direct law. Direct law sucks. Many think of it as a reversion to conventional and it is not. It is a very degraded control system, and it requires a lot of concentration to fly the thing decently, and most don't fly it decently, I have to say. A conventional airplane out of trim is easier to handle than a direct law 320 out of trim. It is in manoeuvers like the Go Around when you see this more clearly. When the airplane is in trim you can make gentle turns, climbs and descents. When you go out of trim things are much different because you can't feel the airplane properly. Trimming like in the Microsoft FS is not what a pilot conventionally does, even if airbus says it is.

Direct law instead of alternate law is a dangerous and silly thing to do. Direct law is the most degraded control law. It is not something you revert to. It is something you can't help, an abnormal situation with risks, similar to a 767 with faulty artificial feel.

English is not my first language, maybe dangerous is not the adequate word.

[CONF iture]

A conventional airplane out of trim is easier to handle than a direct law 320 out of trim.
What about simply flying them in trim then ... be it A or B.

Direct law is the most degraded control law.
No - Mechnical Backup is - And that one is tricky.

After many years in the bus that is what happens to many, even if they have thousands on conventional types.
Speak for yourself first, again, what is your experience outside of the bus ?

[nitpicker330]

I've flown the Sim in Direct law and..........shock horror it's not that hard to do!!

Or dangerous!!

[Microburst2002]

Mechanical back up is not a control law, it is just a mechanical back up. And even worse than that you have triple hydraulic failure, where the only means of control would be differential engine thrust, and maybe pax seats shifting...

My experience with non airbus is over 1,000 in Citation VII (direct mechanical flight control system) and a few in the B767. I know how a conventional airplane flies. I also have a few hours in the microsoft FS, which happens to be similar to A320 direct law. A joystick spring loaded to neutral and a trim wheel.

It is not that you are going to die because of flying in direct law, but there is risks.

And my point: it is NOT a conventional flight control system. Unless MS FS is... It is a crap of system. That is my point, and I will not willingly "revert" to it if I have a nice, closed loop, flight path stable, simple alternate law.

[CONF iture]

Mechanical back up is not a control law, it is just a mechanical back up.
Still listed as the last level of reconfiguration :
Depending on the type of failures affecting the flight control system, or its peripherals, there are 3 possible reconfiguration levels:

Alternate law (ALT 1 or ALT 2)
Direct law
Mechanical

As you already evaluate Direct Law at risk, how would you feel under Mechanical then ... ?

I find it surprising you widely comment on Direct Law as being dangerous or at risk but don't comment on the very subject of the present thread which is :

"Under normal flight conditions (in normal law), if the Alpha Prot activates and Mach number increases, the flight control laws order a pitch down of the aeroplane that the flight crew may not be able to counteract with a sidestick deflection, even in the full backward position."

Here we have the 'dangerous' one ... IMO of course.

[Microburst2002]

Very true.

When sensors go rogue and the system cannot reject them and the wrong information is used by the system, danger is extremely high.

When that happens it is better to revert to alternate law, by getting rid of the rogue sensors. No need for Direct law. But if it takes to go direct for whatever reason, then don't hesitate, of course...

in mechanical law, I would feel OK if I expect to recover something and go into direct or alternate. But If that is not possible, I will not feel OK anymore, for most likely I am going to die.

[Fly3]

Back in 1991 at Toulouse doing the A320-200 conversion we had to fly an ILS and land in mechanical back-up, albeit in good weather, and it was doable so maybe no need to die.

[TyroPicard]

MB2002
It wouldn't be if it had artificial feeling. Being spring loaded to neutral makes it absolutely non natural, non conventional.The side-stick has artificial spring feel which returns the SS to neutral.
The spring force increases with increasing displacement.
- how is that different to a conventional yoke fitted with artificial feel and hydraulically operated control surfaces? I am not a test pilot but it sounds very similar to me...

Yes, you have to pay attention when flying in Direct law - but that is true of any aircraft in manual flight. But it is not difficult for a well-trained pilot.

[Kimon]

You forgot that the electrically-ruddered A333 Adv/A345/A346/A380/A350/A400M have no more antiquated trim wheels.
Trim wheels and mechanical rudders are disappearing chez Airbus.
The electrically-ruddered Airbuses fly differently,crispier and have the additional Derotation Law.

A333Adv/A345/A345:
RTLU is replaced by PFTU and rudder deflection is increased from 29.6° to 31°.
BYDU is replaced by BCM.

A380:
BYDU is replaced by BPS (no more Mechanical Law).

[DozyWannabe]

@Kimon:

They may be electrically actuated, but the trim wheels are still there on this photo of an A346 flight deck (either side of the thrust levers):

http://i21.photobucket.com/albums/b261/lancebin/a346tour/flightdeck7.jpg

Have I misunderstood?

[morbos]

A Q from the cheap seats. Is it only the MD world that has that aural callout? What would be the thinking to not have it? In an out-of-trim situation isn't it useful? Or if the stabilizer has been in motion for longer than a timeout.

[Kimon]

Thanks, DozyWannabe.
So to rectify:
No trim wheels and only electrically-ruddered: A380/A350/A400M.
Trim wheels and electrically-ruddered: A333Adv/A345/A346.
Trim wheels and mechanically-ruddered: A332/A333/A343
All A320 family w/trim wheels and mechanically-ruddered.
Not sure about A320Neo but I guess will be no trim wheels and only electrically-ruddered.

[DozyWannabe]

@Kimon

The manual trim control on the most recent Airbus types has been moved to a switch on the sidestick, in the manner of the 744.

[jcjeant]

What was the procedure for this type of event before the reported incident on EVA Air ?

[DozyWannabe]

It's reasonable to presume this is the first incident of this type, as the AoA probes referenced are a new fit item. As such no procedure existed prior (nor was there any need for it).

[Kimon]

Fitted to previous FBW Airbuses to give pilots a manual reversion option in the event of a full failure, trim wheels are replaced by a pitch trim switches on the aft of the pedestal.

[DozyWannabe]

It would appear that beefing up redundancy in terms of electrical actuation (and relying more on electrical actuation as a result) is an industry-wide trend.

[CONF iture]

It's reasonable to presume this is the first incident of this type, as the AoA probes referenced are a new fit item. As such no procedure existed prior (nor was there any need for it)
The issue of corrupted data that can mislead the flight control computers is certainly not new. But a new dimension is reached with Airbus as the protections take over, and so, based on those corrupted data.
No need for a procedure Dozy ? Would you still think that way if you were a pax on that 330 ?
I don't know which crew had to deal with that AoA issue and how they did react but privately, they probably have a lot to say now, not everything being necessarily nice to Airbus ...
Did you say EVA air jc ?

[DozyWannabe]

The issue of corrupted data that can mislead the flight control computers is certainly not new. But a new dimension is reached with Airbus as the protections take over, and so, based on those corrupted data.

Bad data messing with autoflight is certainly not Airbus-specific. With Airbus FBW, the protections do not "take over", they limit and constrain attitude.

No need for a procedure Dozy ? Would you still think that way if you were a pax on that 330 ?

Read what I wrote - this incident appears to be related to a new piece of equipment applied to the AoA vanes. Prior to the installation of this equipment this did not happen. If I were SLF on that flight I'd hope something would be done quickly (which it has been), but one can't really ask for more than that!

[atakacs]

Bad data messing with autoflight is certainly not Airbus-specific. With Airbus FBW, the protections do not "take over", they limit and constrain attitude.

Bad data is indeed a problem with any FBW design. It still seems that the AB design is prone to create some very unforgiving conditions when seeded with bogus or unexpected information (Perpignan comes into mind). Not sure if there is really a way around it or if it is the price to pay for advanced flight automation.

[Microburst2002]

Tyro said
The side-stick has artificial spring feel which returns the SS to neutral.
The spring force increases with increasing displacement.
- how is that different to a conventional yoke fitted with artificial feel and hydraulically operated control surfaces? I am not a test pilot but it sounds very similar to me...

There is no artificial spring feel in the Airbus, that I know of. Of course there is feel: that of the spring, and totally unrelated to any aerodynamic variable. In normal law, there is a relationship between load factor and the angle and spring force. That's why it is very natural to fly in normal law. But in direct law, there is absolutely no relation with anything, be it speed, load factor, or whatever. Depending on the circumstances, the same spring force will have very different effects.

Artificial feeling in hydraulically operated airplanes is dependent on speed, one way or another, linearly or square of speed. It does not resemble the feeling of a directly mechanically linked FCS exactly, but enough for a pilot to instinctively feel if they are making too hard an input, and how the airplane should respond to a given input. You don't have that on a sidestick when in direct law.

The B777 went to greater lengths of complexity to achieve a pilot instinctive FCS, being it fully computerized. It is difficult to get the advantages of fbw and still make it feel like a conventional airplane that is very easy to fly. When the B777 reverts to direct law I believe it still retains artificial feeling and then it feels like a conventional airplane, only not so easy to fly, where you can trim stick forces.

[CONF iture]

With Airbus FBW, the protections do not "take over", they limit and constrain attitude.
Why don't you read the thread first ... or is it you're more comfortable in denial mode ... ?

[Microburst2002]

True

It does take over.

[DozyWannabe]

Bad data is indeed a problem with any FBW design. Not sure if there is really a way around it or if it is the price to pay for advanced flight automation.

Firstly, remember that FBW and automation are two different things. Non-FBW aircraft such as the B757 (Birgenair) and B767 (Lauda Air) have been lost when bad data was supplied to the automation.

@CONF - I'm not in denial - the alpha protections follow pilot input up until the point safety boundaries are reached and will maintain that, in much the same manner as the T7 will progressively counter input through the force-feedback. Of course, as the Mach number increases, the pitch down will also increase, but it's not going to suddenly force the aircraft into a significant dive, in fact it won't descend at all if corrective action is taken.

This recent modification seems to have been an attempt to counter the risk of icing of the AoA vanes, and it would appear that a set of circumstances outside of the certification testing have shown the fix to be inappropriate.

[CONF iture]

@CONF - I'm not in denial - the alpha protections follow pilot input up until the point safety boundaries are reached and will maintain that, in much the same manner as the T7 will progressively counter input through the force-feedback. Of course, as the Mach number increases, the pitch down will also increase, but it's not going to suddenly force the aircraft into a significant dive, in fact it won't descend at all if corrective action is taken.
If not denial ... what is it then ?

[jcjeant]

It's reasonable to presume this is the first incident of this type, as the AoA probes referenced are a new fit item. As such no procedure existed prior (nor was there any need for it). So it is reasonable to think that if a serious accident had happened (crash) because of this AOA probes problem ... the "no one could imagine that" .. "completely unpredictable" would certainly be in the investigative report ... (this reminds me of something)
Airbus know how work their automation .. and so they were (are) aware of the consequence on the flight automation if this AOA probes problem happens ...
Is that they thought such an event, however, was unlikely to occur?
No procedure needed ?
Even a prayer for good luck?

[DozyWannabe]

jcj - I think you're reading a different meaning into my words than I intended. This problem is a new one that seems to have arisen with a recent modification to the AoA vanes, intending to solve the issue of the icing up of one vane that occurred on AF447. It appears that the fix passed certification and began to be implemented, but the certification tests were not sufficient to catch this new issue (in other words the fix seems to have made the problem worse - with all three vanes freezing in certain conditions).

As with the Thales AA pitot tube design, this incident shows that the certification process needs to be revised based on the evidence presented. EASA and Airbus seem to have been pretty quick in getting the EAD and workaround published once the problem was known.

[jcjeant]

jcj - I think you're reading a different meaning into my words than I intended. This problem is a new one that seems to have arisen with a recent modification to the AoA vanesI don't think so ...
Older AOA vanes or new AOA vanes can have the problem of this particular incident
It's not unpredictable ... even if certifications are bad or good
All in a aircraft is certified and all can fail one day or another
You can't of course have a procedure for every items who fail in a aircraft .. but it must be procedures when important item fail
AOA vanes are important items necessary for the safe conduct of the flight
The implication of the failure described in this post on the flight automation was predictable by the constructor (like a fail of Pitot for what it was procedure already available .. as it's predictable)
But unfortunately no procedure was available for the pilots at the time of this incident .. and it was a risk that this incident turn in a accident ...
Fortunately .. the pilots not goofed .. Airbus yes IMHO

[DozyWannabe]

jcj - the EAD applies specifically to the modified AoA vanes only. The modified AoA vanes are the only type to have suffered a triple failure. Airbus didn't have procedures for triple failure prior to this EAD and nor did any other manufacturer, so why pick on them?

[SPA83]

Anybody knows where we can get the preliminary report ? Merci

[DozyWannabe]

Being an EAD bulletin, it's likely that the incident report is still in progress. I did have a hunt online, but nothing as yet. There are a couple of stories on Flight, but some are subscriber-only.

[CONF iture]

The modified AoA vanes are the only type to have suffered a triple failure. Airbus didn't have procedures for triple failure prior to this EAD and nor did any other manufacturer, so why pick on them?
Dual failure is all it takes to do that mess ... and by its own philosophy Airbus is the only one to allow such mess to take place.

[Microburst2002]

Dozy

In case of an AoA failed in such a way that erroneously gives a stall output, the normal law would pitch down to reduece the AoA. Because it would remain fixed, erroneously, FCS would keep pitching down... Or so I believe.

The fbw can take over and we need to be able, firstly, to detect that normal law is no longer desirable and secondly to revert to a safe control law.

[Yankee Whisky]

but never in 40 years have I ever heard of an 'undue' stall warning....

BEagle, an "undue"stall warning is indeed a real occurence. I flew a lot of L-19 (Birddog) tows (5000 plus) and the stall warning buzzer would regularily go off in turbulence, such as, for example, 15 kn wind and strong thermal conditions. Maintaining attitude always got us (glider and self) through this.

Similarily, when towing through a rotor in mountain wave conditions would cause the same.:ok:

[BEagle]

I would term that a 'spurious' stall warning. I had a spurious stall warning at about 400 ft on a flapless approach in a VC10 when sticking AoA probes (the jet had been in the desert without a decent wash for too long) jumped, triggering phase advance and a sudden stick push.....

Direct reading AoA gauges should be installed in all airliners. Not some extra thing displayed electronically, just a simple, direct instrument.

The Russians used to have a combined AoA gauge and g-meter in many of their aircraft. What an excellent safety aid that must have been!

[jcjeant]

In the press .....
Des pilotes Air France exigent le retrait de sondes d'Airbus - Le Nouvel Observateur (http://tempsreel.nouvelobs.com/societe/20121220.OBS3220/des-pilotes-air-france-exigent-le-retrait-de-sondes-d-airbus.html)

Google*Traduction (http://translate.google.be/translate?sl=fr&tl=en&js=n&prev=_t&hl=fr&ie=UTF-8&eotf=1&u=http%3A%2F%2Ftempsreel.nouvelobs.com%2Fsociete%2F20121220. OBS3220%2Fdes-pilotes-air-france-exigent-le-retrait-de-sondes-d-airbus.html&act=url)
Air France pilots require the removal of probes Airbus
"We can not meet the manufacturer and the authority just by a simple procedure permanently supplement what appears to be a serious deficiency of an element as vital to the conduct of the flight," said Jean-Louis and Barber, president of the AF SNPL Alpa.

[DozyWannabe]

In case of an AoA failed in such a way that erroneously gives a stall output, the normal law would pitch down to reduece the AoA. Because it would remain fixed, erroneously, FCS would keep pitching down... Or so I believe.

The AoA in Normal Law will be held just short of Alpha Max if Alpha Prot is triggered. An increase in Mach will cause the Alpha Max to decrease - and the pitch angle will follow, but it would be a gradual process - you're unlikely to find yourself in even a shallow descent if corrective action is taken in a timely manner.

The fbw can take over and we need to be able, firstly, to detect that normal law is no longer desirable and secondly to revert to a safe control law.

I'm a little fuzzy on what "taking over" constitutes - Alpha Prot should not command significantly opposite the input it is given as that is not the way it is designed to work.

I'm all for waiting to see the incident report before making sweeping judgements. I find the fact that Alpha Floor is not mentioned interesting, as I would have expected it to have been activated if there was a manual pitch-up command given in that circumstance. Equally intriguing is the fact that the crew managed to correctly troubleshoot the situation and return the aircraft safely to the ground despite having no forewarning of the problem. Someone out to bash Airbus at any opportunity probably won't care about such questions, but if we're being open-minded about things it should definitely give pause for thought.

@jcj - No-one's talking about the Airbus ADR procedure being a permanent solution - it is clearly presented by the EAD bulletin as a temporary workaround while the AD is being implemented on the affected airframes.

[Lyman]

Four years ago, AF pilots threatened strike if AF did not immediately obey the AD requiring pitot probe replacement.

After 228 people were killed in AF447....

Once bitten. Twice shy...

[DozyWannabe]

Four years ago, AF pilots threatened strike if AF did not immediately obey the AD requiring pitot probe replacement.

There were a lot more airframes in the AF fleet alone with the Thales AA probes than there are airframes in the worldwide fleet with these AoA vane modifications. I suspect the AD will be implemented with all due haste.

[Lyman]

Did the pilots get your memo?

[CONF iture]

I'm a little fuzzy on what "taking over" constitutes - Alpha Prot should not command significantly opposite the input it is given as that is not the way it is designed to work.
Which part is that confusing for you in the A330 AIRPLANE FLIGHT MANUAL :

At any time, if the aircraft goes to an unmanageable pitch down attitude despite a continuous deflection of the sidestick in the full backward position : APPLY THE EMERGENCY PROCEDURE

[Greek God]

In a recent memo:

"The trouble shooting efforts of the flight crew ( they had turned off the 3 ADR systems) eventually placed the aircraft into ‘Alternate law’ which allowed the Pilots to override the Alpha protection and recover control although in a degraded state."

Why do airbus insist on regarding alternate and direct law "degraded"

Every aircraft I've flown prior to this airborne Citroen has been flown in "Direct" Law. Flying in Direct law is a non event really & I love the paradox in the above statement. Flying with the controls in a degraded state allowed the recovery of an aircraft flying in a degraded state??? :ugh:

[jcjeant]

Why do airbus insist on regarding alternate and direct law "degraded"For Airbus the way to fly this aircraft is "Normal law"
When the aircraft is no more flying in the "Normal law" .. he is flying in a "degraded" (Airbus phraseology) state (all the other "laws" kindly made available by Airbus ) IMHO
In a word .. for save your soul (and souls of the back cargo) sometime it's better to fly in "degraded" law ... if the pilot know how ... :)

[A33Zab]

"The trouble shooting efforts of the flight crew ( they had turned off the 3 ADR systems) eventually placed the aircraft into ‘Alternate law’ which allowed the Pilots to override the Alpha protection and recover control although in a degraded state."

That is 1 ADR to much....

'Degraded' because one will loose more than the AoA protection only in alternate.

[BOAC]

At any time, if the aircraft goes to an unmanageable pitch down attitude despite a continuous deflection of the sidestick in the full backward position : APPLY THE EMERGENCY PROCEDURE - in the old days it would have been:
At any time, if the aircraft goes to an unmanageable pitch down attitude despite a continuous deflection of the sidestick in the full backward position : EJECT.

[DozyWannabe]

Did the pilots get your memo?

The airframes and mods affected are explicitly listed in the EAD. It only takes a little research to realise that this mod is very recent - being applied from earlier this year. The after-market and custom order Thales AA pitot tube fitting was being done for years before problems were noted.

Which part is that confusing for you in the A330 AIRPLANE FLIGHT MANUAL :

At any time, if the aircraft goes to an unmanageable pitch down attitude despite a continuous deflection of the sidestick in the full backward position : APPLY THE EMERGENCY PROCEDURE

I suspect the translation's a little off there, but that doesn't really matter. The point is that based on the way Alpha Prot works (explained in a lovely concise manner by BPalmer here : http://www.pprune.org/tech-log/503248-how-safe-airbus-fly-wire-airbus-a330-340-a320-family-emergency-ad-3.html#post7590234 ), it will take some time for a significant pitch-down attitude to develop from the normal attitude, which is usually nose-up to some extent.

Why do airbus insist on regarding alternate and direct law "degraded"

Because that's the way it was designed to operate. It was designed to operate that way because technology had progressed to a point where the de facto "traditional" control set up (itself a product of the limits of pre-war technology) was due a revision. With the move to all-hydraulic actuation in the '60s, a lot of effort was put into effectively faking similar behaviour to the old cable-driven designs - so the question was at what point did all this work and the complex machinery involved to implement it become more hassle than it was worth? Airbus decided it was time for a clean-sheet approach and whatever you, I or anyone else may think of it personally, it's been very successful and statistically as safe as anything else.

[DozyWannabe]

"Nomal Law" with all protections, gets a grade of "A". Anything else, missing one or more "protections" is sub standard in quality, iow, unprotected, the dummy flying can now make a blunder that the system will have prevented in "A" mode.

With equal respect, such an opinion can only be advanced if one believes that the design of the system was predicated on limiting human involvement in flying the aircraft. While it seems to be a difficult notion to shift in some quarters, the fact is that it is utterly untrue.

The reason for considering control laws outside Normal "degraded" is for no other reason than they were designed to come into effect in the event of a technical or structural failure in the aircraft and its systems. The concept is no different than older designs in the event of, say, partial hydraulic loss where the working systems provide a degree of control, albeit in a degraded manner.

In this case, the temporary workaround published by Airbus is in effect simulating dual ADR failure, which will cause the flight law to degrade to Alternate.

* - Hmm, seems like Lyman's post disappeared...

[jcjeant]

Being an EAD bulletin, it's likely that the incident report is still in progress. I did have a hunt online, but nothing as yet. There are a couple of stories on Flight, but some are subscriber-only.

BEA answer to a question about the investigation of the Eva Air AOA incident:
« La décision d'ouvrir et de conduire l'enquête de sécurité sur cet évènement appartient aux autorités japonaises (état d'occurrence) ou taïwanaises (éta
de l'opérateur). Celles-ci ont décidé de ne pas ouvrir d'enquête, c'est la raison pour laquelle vous ne trouvez pas trace de l'évènement sur le site Internet du BEA. »


"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. '

[CONF iture]

I suspect the translation's a little off there, but that doesn't really matter. The point is that based on the way Alpha Prot works (explained in a lovely concise manner by BPalmer here : How safe is (airbus) fly by wire? Airbus A330/340 and A320 family emergency AD ), it will take some time for a significant pitch-down attitude to develop from the normal attitude, which is usually nose-up to some extent.
Which translation (?) ... there is none.
LOVE makes you blind DOZY - How hard is it to may have to admit some weaknesses in the Loved one - If you treat your wife the way you treat Airbus, she must be the happiest woman on earth really, but if you don't, she would have every reason to get jealous ...

[DozyWannabe]

CONF iture, I'm simply applying fairness and reason - I'm not the kind to get emotionally invested in aircraft (well - except maybe Concorde and the VC10 ;) ).

Also, as far as I know Airbus documents are well-known for being written in French and translated into English, sometimes making them read slightly unusually to native English speakers.

[CONF iture]

Also, as far as I know Airbus documents are well-known for being written in French and translated into English, sometimes making them read slightly unusually to native English speakers.
Why should they be written in French suddenly ?
Aren't you that very guy who likes to mention how Airbus is multi-national, not just French ?
Do not imagine translation issue where there is none.

CONF iture, I'm simply applying fairness and reason - I'm not the kind to get emotionally invested in aircraft.
DOZY, what you're applying and so with brilliance, is intellectual dishonesty.

[DozyWannabe]

I'm only repeating what I've been told and have read over the years regarding translation of Airbus documents.

As for honesty, intellectual or otherwise, I'm not the one trying to present what is clearly a quickly-remedied problem with a recent modification to AoA vanes as a deep and underlying problem with the FBW design.

[Kimon]

There's a point about this dastardly translation business whereby I remember that the French version says in case of stall to "Afficher 5° d'assiette" whilst the English version says "Reduce...........".
There is a big difference in "Afficher" which means to display as opposed to "Reduce".

[Philemon]

Hello to all of you,

Is there on Pprune any Eva Air pilot who can detail more precisely what happened on the A330 who recently lost its 3 AOA ?
We hear a lot of things about the reasons who led the pilots to disconnect 2 ADR :
1) that the aircraft was AOA indicators equipped and it is one of its related emergency procedures who led them to think about that ; or
2) that it's rather the "Unreliable Airspeed" procedure who...

Is somebody able to answer these question ?

[Lyman]

Let me ask the question another way...

Since no AOA display exists for the pilots, and AoA is critical to the flight path, how is "UnreliableAoA" not a far more problematic abnormal than "UAS"? Further, once somehow established on the flight deck that AoA is corrupt, how does initiating a UAS failure equate to an acceptable solution?

Two abnormals equal a "NORMAL"?

With apologies to Will Fraser: UAI Unreliable Angle of Incidence....

[A33Zab]

We hear a lot of things about the reasons who led the pilots to disconnect 2 ADR :
1) that the aircraft was AOA indicators equipped and it is one of its related emergency procedures who led them to think about that ; or
2) that it's rather the "Unreliable Airspeed" procedure who...

No EVA source however:

From another topic about the subject, it was said they switched off all 3 ADR i.s.o. 2, if equipped with 'BUSS' that will display the BackUp SpeedScale and AoA pointer.

if they re-select any or all ADR it will revert to the 'normal' speed display while alternate law (without AoA protection) remains.

In a reaction (http://www.thalesgroup.com/Press_Releases/Markets/Aerospace/2012/Thales_clarifications_regarding_the_%E2%80%98Angle_Of_Attack %E2%80%99_(AOA)_probes_that_equip_Airbus_A320_and_A330_aircr aft/)Thales submitted the aircraft involved was not Thales AoA vanes equipped and they where not responsible for the conical plate.

So Goodrich 0816ED vanes must have been installed....

Conical plates are physically different (Thales has flat circular cutout while Goodrich has a countersunk and lemon shaped cutout).....

Did they fitted 'thales' plates on goodrich vanes? conical plate on top of original flat plate?

[captplaystation]

All I can say , 5 pages into this thread, is Thank God I still fly a Dinosaur, which, whilst far from perfect, tends to go up at the rate I ask, down in a similar fashion ( with Left & Right similarly easily defined.)

I think, as a teenager , I saw straight through the Bernard Zeigler bullsh1t. . . adulthood & a life flying commercialy (predominantdly Boeing) have reinforced my wet behind the ears beliefs.

Don't, and never will, trust them.

Whenever I am in one, I am just that few (:hmm:) % points less comfortable than I would be in a more "conventional" aircraft &, you know what, I can spend all day arguing my point of view to anyone calling me a luddite, and I think I may on most occasions win the argument.

[DozyWannabe]

I think, as a teenager , I saw straight through the Bernard Zeigler bullsh1t. . .

Don't, and never will, trust them.


It was a major tragedy that Gordon Corps (who was the real engineering pilot behind Airbus FBW) died when he did, not only because he was the public counterbalance to BZ's flights of fancy, but also because he had a knack of explaining and proving the systems in public in a way that pilots could get behind (and as DP Davies' successor at the ARB before he joined Airbus, Corps had the "old-school" clout to make people listen).

Whenever I am in one, I am just that few (:hmm:) % points less comfortable than I would be in a more "conventional" aircraft &, you know what, I can spend all day arguing my point of view to anyone calling me a luddite, and I think I may on most occasions win the argument.

I'd never go so far as to call you or anyone else a Luddite for what you believe - it's a perfectly rational position and unfortunately with the loss of Capt. Corps the Airbus message did get somewhat muddled in the late '80s, so an opportunity to reassure you and others who are of this position was sadly lost.

[SLFandProud]

All I can say , 5 pages into this thread, is Thank God I still fly a Dinosaur, which, whilst far from perfect, tends to go up at the rate I ask, down in a similar fashion ( with Left & Right similarly easily defined.)
Well that's deeply concerning; may I ask who you fly for so I can avoid them?

If you're only qualified for a mythical type that suffers no equipment failures or malfunctions whatsoever, on which you are happy to place total reliance, I would suggest a certain amount of complacency had set in.


I hope you're not representative, in which case I thank God for pilots who know their type well enough to understand what to do when their aircraft doesn't do what it's 'tended to' since Pterodactyls ruled the skies.

[DozyWannabe]

@SLFandProud - Come on, let's not get into another argument on that again - he's said his peace, best leave it be.

[737Jock]

Dozywannabe what is your response regarding post 63 and Post 68 on http://www.pprune.org/tech-log/503248-how-safe-airbus-fly-wire-airbus-a330-340-a320-family-emergency-ad-4.html

[Chris Scott]

According to the EASA EAD, these new-fangled "conic" plates could be either factory fitted or retro-fitted to both the Thales and Goodrich AoA probes. Can anyone explain their purpose? To prevent damage to the existing vanes, perhaps? Or to prevent icing?

Presumably they are comparable to the installation on VC10s in the 1960s, but bigger? Any chance someone might have a photo, or be able to take one while going up the front steps?

Thanks in anticipation...

[Lyman]

From the standard install I see on the 330, does the advantage come from a smaller diameter pivot at the vane mount? This would seem to give the vane more mechanical advantage against accretion at the through hole? Less advantage for any ice accretion at the larger diameter pivot on the standard install? also less ice to melt for the heater?

[A33Zab]

For the Thales AoA sensor to protect from ice accretion to the protruding (non heated) base.

For the Goodrich AoA sensor to protect from water ingression in outer bearing. (Perpignan accident)


http://i474.photobucket.com/albums/rr101/Zab999/AoA_Conical_zps8938baab.jpg

Thales conical plate installation, on top the original flat plate.

below Goodrich AoA sensor (plate not shown) , Conical plate and an image from the Bea final perpignan report.

http://i474.photobucket.com/albums/rr101/Zab999/Goodrich_AoA_zps6366b82e.jpg

http://i474.photobucket.com/albums/rr101/Zab999/Goodrich_Conical_zps2646c634.jpg

http://i474.photobucket.com/albums/rr101/Zab999/AoAPerpigan_zps0f88d094.jpg

[captplaystation]

SLFand Proud,

perhaps better keep it that way :hmm:

I said tends to , and the day it doesn't, my response to any control malfunctions will be a whole lot more instinctive/rational than having to fumble around on the overhead panel switching sh1t off. But, your understanding of this may not be as highly developed of course, if you have never been handed an out of control aircraft, & been expected to sort it out fairly rapidly, you can be excused for that.

It is not massively advanced, nor modern, to have commercial aircraft , in the year 2012, performing potentially lethal manouveres, requiring that you disconnect most of the "raison d' etre " to control them. . . . do you not see a contradiction here ?

[jcjeant]

It is not massively advanced, nor modern, to have commercial aircraft , in the year 2012, performing potentially lethal manouveres, requiring that you disconnect most of the "raison d' etre " to control them. . . . do you not see a contradiction here ?
Location:
A hight technology industry laboratory
Incident:
A pipe carrying water is leaking and water drops on a equipment powered by electricity
Solution DGAC
Suspend a tin below the leak and empty it before it overflows
Repeat as many as requested
This is what the DGAC asked the pilots with their procedure

[SLFandProud]

SLFand Proud,

perhaps better keep it that way I said tends to and the day it doesn't, my response to any control malfunctions will be a whole lot more instinctive/rational than having to fumble around on the overhead panel switching sh1t off. But, your understanding of this may not be as highly developed of course, if you have never been handed an out of control aircraft, & been expected to sort it out fairly rapidly, you can be excused for that.

It is not massively advanced, nor modern, to have commercial aircraft , in the year 2012, performing potentially lethal manouveres, requiring that you disconnect most of the "raison d' etre " to control them. . . . do you not see a contradiction here ?

To be honest, that was so incoherent it's difficult to see what your point is, let alone determine contradictions; I presume English is your second language though, so I shall soldier on regardless with apologies if I've misunderstood you.


You did indeed say 'tends to'. But this discussion is not about what aircraft - of any type - 'tend' to do; it's a discussion about what a particular type does with multiple equipment failures - 'tendency' is irrelevant. You suggested in your post that should the aircraft you are piloting ever cease to do what it 'tends to' you would be out of your depth.

You rather underline it by claiming in the event it does happen, your response will be both instinctive and rational. Which is pretty much by definition impossible. Either you use your instinct - which in most cases of aircraft upset is likely wrong (see pilots stalling planes passim,) or you rationally evaluate the situation. If you are terrified of having to rationally evaluate a situation - "fumble around on the overhead panel switching sh1t off" suggests someone liable to 'intuitive' panic responses rather than rational action - then you should consider whether a career in the arts may be more suitable.

[Lyman]

Aircraft most definitely have tendencies. Ignore them at your great risk.

As in "landing light", another thread, or "Twitchy in roll direct", from 447.

Or, "watch it, lest you roll it into a ball." Maybe, instinct and rational will be wrong, but likely not. Sometimes rote is good: "critical thought is not helpful"
(alcorfr, another thread). Sometimes intuition is all you have.

"behind is not good, but don't get ahead of yourself" etc.

"Incoherent"? Maybe an apology?

edit.... Before Feb 2008 (BEA 038) reside the oldtimers. I have yet to see anyone from the pre "ice fuel" thread demonstrate foolishness. I look for join date, and pause, lest my keyboard get me in trouble.

just sayin...

[SLFandProud]

Aircraft most definitely have tendencies. Ignore them at your great risk.

As in "landing light", another thread, or "Twitchy in roll direct", from 447.
Absolutely; experience of all relatively complex machines is invaluable for an operator to know its own quirks/peculiarities/'tendencies'. But when the tendency you are dependent on is that it "[goes] up at the rate I ask, down in a similar fashion ( with Left & Right similarly easily defined.)" then you are displaying a terrifying level of complacency.

You are paid to know what to do when it does not "go up at the rate I ask, down in a similar fashion ( with Left & Right similarly easily defined.)" I think you'd probably agree, that's what makes skilled pilots relevant - otherwise a very basic computer could do the job.

[Lyman]

My bad. I agree. Experience is beneficial related to ts breadth.

I do not consider "predictability" a "tendency". I can't source it really, but have always associated a 'tendency' with a bad habit or characteristic, be it mechanical or otherwise.....

[DozyWannabe]

Just popping in to clarify that the "twitchy" comment was not made regarding AF447, it was made by a single poster once on one of the early 447 threads and was neither supported nor refuted by anyone else.

[captplaystation]

SLF

I will bow to your obviously superior viewpoint (24 posts AND SLF ) as evidently my 18,000hrs flight experience, including 14,000 in Command of B737, makes me wholly unworthy of contradicting your expert opinion of Airbus FBW, and the qualities required of a professional pilot & aircraft Commander.
As you say, perhaps, 35 years later I should consider whether I may indeed have been more suited to a career in the arts.

Oh BTW you are correct, English is not my first language, I am Scottish, but I am endeavouring, with all my best efforts, to master it, along with French & Spanish, as I live my life/work in 2 different countries, excluding the UK.

Being home to many individuals like you, who insist on displaying this particularly British , and not very endearing trait, nominating themselves "armchair experts" on something they in all likelihood have no qualification in, nor usually participated in ,at least in a professional capacity, may have been at least part of the reason I left it behind 20 years ago.

What a blessing that was.

[Chris Scott]

A33Zab,
Thanks for producing, as usual, such superb pictures (and apologies for my late acknowledgement).

This is a much more subtle mod than I had imagined. The 1960s VC10 AoA probes, which were dedicated to its three-stage stall protection system, enclosed the (much smaller) vanes completely. Slots in the cones admitted the airflow. The VC10s smaller sister, the BAC 1-11, employed a similar stall protection system. However, the (larger) vanes of its AoA probes were not enclosed.

Reviewing the big picture, it does seem strange that Airbus aircraft have latterly been experiencing so many problems resulting from icing of pitot probes, and now AoA probes. After all, these aeroplanes are operating in a similar environment to other types, and (presumably) jet airliners generally since even I was wearing short trousers. Granted, these FBW types are much more reliant on the availability and accuracy of the data concerned than previous types, most of which didn't even have AoA probes. If the heated AoA probes on my VC10 had become frozen, I might have been none the wiser unless I was pushing the buffet margins and waiting for the auto-ignition lights to flicker. But I flew the A320 for the first 14 years of its operation, and probe icing didn't seem to be an issue. Were we simply living in blissful ignorance?

[Lyman]

It is a puzzle. For sixty years, the USAF had been flying to 50,000 feet, and experienced none of the "hitherto unknown characteristics of fuel icing".

Then BA038. Then Airbus is plagued by ice afflicting its mechanical sensors critical to airspeed data displays. Then Angle of Attack vanes.

It takes a cynic to lay off the issue on heating, metallurgy, and other well developed legacies of our aeronautical technologies.

If it is indeed down to sensor design, then shame on the kit and its sponsors who spec it. I don't believe it. Because if it is, we have some gaping holes in our technologies.

The alternative is to look elsewhere. I take note of Captain Scott's troublefree experience in the gen one 320. I have a friend who flew the 320 for ten years, nary a belch or hiccup. What is new that hasn't to do with sensors and heating?

Processing? Mitigating pathways post fail? Because if it is 'Probes', perhaps a return to yarn on the Radome? A Pendulum on the glareshield?

A33 thank you for the exquisite photography. I think I see the improvement in the AD compliant kit. The "base" cone is proud of the fuselage, where the original appears flush. It also appears the pivot is reduced in diameter, making it less susceptible to ice "sticking" its action.

I wonder if adding small "spades" at the vane trailing edge would increase the vanes ability to remain "in stream". Perhaps even making the vanes into a double, a "bi-vane". Anything that ancient that has problems begs a change of some sort.

[DozyWannabe]

Reviewing the big picture, it does seem strange that Airbus aircraft have latterly been experiencing so many problems resulting from icing of pitot probes, and now AoA probes.

The Thales AA pitot tubes at the root of the problems that led up to AF447 were an optional fit that was only available from the end of the '90s. Prior to that the only units fitted were the Goodrich models that the A330 and 340 were originally certified with. Jet airliners have had problems arising from blocked pitot tubes since at least the early '70s and probably earlier (they were central to the Stony Brook NWA 727 disaster, as well as Birgenair 301's B757). What was new about the problems with the Thales AA model was that because they were individually more susceptible to blockage from ice and supercooled water, the risk of a triple failure - previously considered remote - grew considerably.

It appears that the new AoA vane housing (also available from both Thales and Goodrich) is a new design intended to reduce the risk of the kind of blockage that brought down the Perpignan A320 and caused a single vane to freeze in the case of AF447. As yet, we don't know which model was fitted to the aircraft in this incident, but it appears that the EAD is causing a review of this new design and a fix should be in the works.

[Lyman]

NWA accident you refer to was caused by pitot heat selected OFF prior to take off, and not selected ON thereafter. Perhaps a poor example then, here, since the problematic A330 probes were operating heated when they failed.

Rgds.

[jcjeant]

Hi,

DW
As yet, we don't know which model was fitted to the aircraft in this incident, but it appears that the EAD is causing a review of this new design and a fix should be in the works.Long ago (you made ​​yourself note) probes are prone to icing or blocking by ice particles and since that time there has been no suitable solution found and I think it will not change until prohibit aircraft from flying in icing environments or equip each sensor with a flamethrower

[DozyWannabe]

@Lyman - It was a general reference to historical pitot tube blockage-related problems, not a specific comparison to the Thales AA issue.

@jcj - The problems we're talking about are not the traditionally-accepted blockage of one or two sensors, but changes to the design post-certification that raise the risk of a triple failure.

[jcjeant]

@jcj - The problems we're talking about are not the traditionally-accepted blockage of one or two sensors, but changes to the design post-certification that raise the risk of a triple failure. You have two probes .. three probes .. certified or modified (and certified again) .. when they will find it in the right environment (air freezing or ice particles) the greater the chance that they will all be put out of function
So .. 2 probes .. double failure ... 3 probes .. triple failure ....
But if you have 3 probes and one is heated near is melting point .. you will have only a double failure
It's just to find how heat a probe near his melting point .. and able to continue to function normally ...

[Lyman]

Dozy

"DozyWannabe @Lyman - It was a general reference to historical pitot tube blockage-related problems, not a specific comparison to the Thales AA issue."

Thanks for the disclaimer, had you included it prior, electrons would be conserved.

And your post would have been unnecessary, being superfluous to the discussion....

:ok:

[DozyWannabe]

You have two probes .. three probes .. certified or modified (and certified again) .. when they will find it in the right environment (air freezing or ice particles) the greater the chance that they will all be put out of function
So .. 2 probes .. double failure ... 3 probes .. triple failure ....


It's a question of systems safety. The aircraft were originally certified with the Goodrich pitot tubes fitted - there has never been a triple failure with this setup. The Thales option was introduced later and was certified independently - maybe someone can confirm whether this did or did not involve being certified in situ as opposed to just in the lab.

Nevertheless, there turned out to be something inherent in the Thales AA design that made it more susceptible to precipitation blockage than the default Goodrich fit.

A question was asked regarding why these problems seem to be confined to a time period a decade or so after the introduction of the A320 and her sisters - I'm just supplying one potential reason as I've understood things.

[Lyman]

Bonjour jcj...

As I see it. The Thales were a serious problem, hence the AD. Air France was slow rolling the AD, and Thales killed AF 447.

A single Titanium piece killed Concorde, end of story.

But AF slow-rolling compliance with a direct order? The single cause of AF447?


Mais NON..... All of a sudden it's the airplane, the pilots, the weather, the.....

I get it....

[DozyWannabe]

As yet there have been no criminal or civil proceedings regarding AF447, and thus no attempt to distill the contents of the BEA report (which covers all the potential causes including the Thales AA pitot tubes) into a legal narrative. The BEA report into AF4590 was similarly exhaustive - it was the *legal actions and not the report* which isolated the titanium strip as the major causal factor.

Coincidentally, aside from a premature but arguably understandable engine fire drill action, the crew of AF4590 performed in a logical, consistent and understandable manner once the flight became abnormal, despite facing what was later determined to be an unsalvageable situation. The PF of AF447 was faced with a relatively minor systems failure and, for whatever reason, performed in a manner which was contrary not only to established procedure but also to basic airmanship (pulling up consistently and repeatedly in the face of AP disconnect followed by stall warning) and his colleagues failed to check his actions or communicate amongst themselves effectively.

This is why crew action is considered to be a more prominent factor in AF447 than it was with AF4590. That said, and repeating for clarification, the problems with the Thales AA pitot tubes are listed as a contributing factor to the accident in the BEA report.

[jcjeant]

That said, and repeating for clarification, the problems with the Thales AA pitot tubes are listed as a contributing factor to the accident in the BEA report. I think they have a role more than contributing in the accident
In fact they are the trigger of the accident
If the probes were not blocked .. the accident not have occurred .. Bonin and other pilots of AF447 would have continued a quiet career at Air France .. . and the passengers will be there to celebrate the new year 2013

[captplaystation]

Sad to say, ain't that the truth . . . . . . whilst most of us are overwhelmed with incomprehension as to how these guys stalled in the cruise, and remained stalled all the way to the sea. . . it is incumbent upon us to be humble enough to acknowledge that maybe, just maybe, we could've screwed up in exactly the same way.

[Turbine D]

Dozy,
Your quote:
Jet airliners have had problems arising from blocked pitot tubes since at least the early '70s and probably earlier (they were central to the Stony Brook NWA 727 disaster, as well as Birgenair 301's B757).

I believe the subject is about Airbus 330/340 sensors and probes that apparently inadvertently fail due to ice/water accumulation or ice blockage at high altitudes. The examples you cite are failures caused by mistakes: Birgenair 301 - B-757 sphecid wasp pitot tube blockage on the ground - Stony Brook NWA B-727 - pilots forgot to activate pitot tube heaters. Hopefully these were not subtle digs at B, but if so, you forgot one: Aeroperu 603 B-757 - static ports blocked by tape that wasn't removed before T/O.:ugh::ugh::ugh:
So back to the real thread topic:

Chris Scott Quote:
Reviewing the big picture, it does seem strange that Airbus aircraft have latterly been experiencing so many problems resulting from icing of pitot probes, and now AoA probes. After all, these aeroplanes are operating in a similar environment to other types, and (presumably) jet airliners generally since even I was wearing short trousers.
But I flew the A320 for the first 14 years of its operation, and probe icing didn't seem to be an issue. Were we simply living in blissful ignorance?
and,
Lyman Quote:
The alternative is to look elsewhere. I take note of Captain Scott's troublefree experience in the gen one 320. I have a friend who flew the 320 for ten years, nary a belch or hiccup. What is new that hasn't to do with sensors and heating?

It is my opinion, what Chris and Lyman mention is where the probe and sensor problem rests. The commonality shared with the A330/A-340 is the fuselage that it is different compared to the A-320. If one recalls the aftermath of the AF447 incident, the European certification authorities proposed an update to the pitot probe certification requirements. They asked for comments from manufacturers and users for their proposed requirements. Airbus responded by basically saying the proposed certification standards were not stringent enough and did not reflect what was being experienced relative to high altitude icing conditions. They cited various reasons for this, volume of ice, size of ice crystals, etc. Then curiously they mentioned something important in my mind. The location of the sensor or probe relative to the aerodynamics of the area surrounding these devises was important and was not being considered as part of the certification process. Could it be that the location selected for the probes and sensors on the A-330/A-340 be such that it is more sensitive to ice crystals or water being directed into these devises verses the unshared A-320 fuselage shape or other aircraft where the location may not be as sensitive? Did Thales get a raw deal and bad publicity because their probes happened to be slightly more sensitive than Goodrich probes, both meeting the certification requirements in force at the time because of this? Was the change in the AoA sensor base plate an attempt to fix problems without the need to relocate the sensor location? I am not an aerodynamic or a probe/sensor expert, but as an engineer, I wonder about the relationships here. While it is implied the A-320 has not had the experiences of the A-330/A-340, I wonder what the experiences of Boeing aircraft and pilots has been relative to icing of pitot tubes. Also, the original bill of materials for pitot tubes on the A-330 (perhaps the A-340 as well) were Goodrich pitot tubes, replaced by Thales which were believed better at the time.

[Microburst2002]

Dozy

Who knows what the ELAC will command if suddenly it finds its AoA to be well above alpha prot? The system is designed to avoid excursions into high AoAs, but if the AoA happens to be too high without he system being able to avoid it, because it is just a fake input, the system will not question how is that possible. It will just pitch down to regain alpha prot. But if the AoA remains fixed (because of the faulty probe) then it will keep pitching down, at eitherhigh or low mach number until it reaches alpha prot, which will not occur because it is corrupted. The ELAC is silly and will do its job as designed, believing it is in a stall.

In my opinion the system will command constant pitch down, and while in normal law, pilots cannot override it. I don't know, however, the intensity of that pitching down input.

[heavy.airbourne]

I don't know, however, the intensity of that pitching down input.
...until crash - see XL.

[Chris Scott]

Dozy,
Thanks for the useful gen on the Thales probes, and the conic plate mods.

Inconveniently, neither of the accidents you mention were caused by icing of a heated pitot probe, as Lyman and Turbine_D have pointed out.

LIke them, I wonder if the location of the probes needs to be reviewed, and if the slimmer nose of the A320 may be a factor. Also, I sometimes used to ponder, during my walkrounds, on the pros and cons of locating Pitots 1 & 2 at precisely symmetrically-opposite positions on the fuselage (Pitot 3 being the odd one out). Then I would remind myself that the same applied to the AoA probes. It seemed to me that this might be a recipe for (roughly) simultaneous ice accretion of numbers 1 & 2.

Can anyone cite an accident prior to AF447 that was related to the icing of a properly-heated pitot probe or AoA probe? Right now, I can't think of one, nor of a type that regularly experienced UAS problems in any flight-phase.

Happy New Year everyone and, for those who practise, safe landings!

[DozyWannabe]

...until crash - see XL.

I'm pretty sure the XL (Perpignan) A320 went into Direct Law before it crashed.

]Inconveniently, neither of the accidents you mention were caused by icing of a heated pitot probe, as Lyman and Turbine_D have pointed out.

As I said, I wasn't making a direct comparison in terms of the scenario, I was simply enumerating incidents and accidents with blocked pitot probes as a central factor.

LIke them, I wonder if the location of the probes needs to be reviewed, and if the slimmer nose of the A320 may be a factor.
...
It seemed to me that this might be a recipe for (roughly) simultaneous ice accretion of numbers 1 & 2.

Possibly - but nevertheless I don't believe there has been a UAS incident on an A330 or A340 recently - specifically since the Thales model pitot probes were phased out.

[jcjeant]

There is still an important issue about the accident and it is to Airbus to respond
How is that Airbus have not been able to predict what would happen at the level of flight automation when the AOA probes are blocked by icing or other phenomenon?
That is blocking AOA probes has never been considered .. or tested ?
This test would have shown the consequences on the flight automation .. and so be able to provide a procedure before any accident ....
In the EVA Air case .. that's the pilots who have tested ... and found a procedure ..
Weird ..

[Lyman]

jcjeant

That is the issue, not dissembling and lame attempts to minimize rhe hazard.

AB have built an a/c that is virtually completely dependent on processed data, the exclusion of mitigating procedures, or even a plan to anticipate failure.

The recent workaraound for disabled AoA vanes was ad hoc

It became policy only after it succeeded. That is called Flight Test.

Disabling the AirData system by switching off ADRs qualifies as an UAS event.

I have no patience with anyone who tries to smooth over a genuine risk.

Especially if it is transparently partisan to the airframer, rather than objective discussion.

My bias is safety in aviation. Let the feelings and sensibilities pound sand.

[RR_NDB]

Hi,

During the rich discussions in AF447 threads i emphasized the essential characteristics of a good design: Fault Tolerance and Graceful Degradation.

FBW opened the possibility to introduce new features like Protections. We may view that as "sophisticated interlocks" designed to help, to protect.

In AF447 case we found engineering problems like lack of redundancy, Garbage In Garbage Out (GIGO) contamination and in some posts i commented on the perception of "accelerated degradation". Actually made an analogy to the "threshold effect" of FM radio reception (below a given threshold degrades abruptly) compared to AM radio.

My point here is:

Airbus SAS is leading the industry with it´s advanced automated design. Is the design adequately capable to cope with existing sensors limitations that for whatever reason are not providing sometimes reliable data to the System?

It´s reasonable to delegate to PF (and subsequently to PM) complex scenarios that even for a designer could be very difficult to understand timely?

IMHO the basic characteristics of a good design may be under threat with the paraphernalia of features introduced with the argument of easier operation, etc.

Multiple unreliable sensors (simultaneous in F-GZCP) are sometimes promoting "accelerated degradation" of the A/C (System+crew)?

This is being adequately tested? Safety is under an special kind of threat? A more complex one? :confused:

[RR_NDB]

Hi,

jcjeant:

I think they have a role more than contributing in the accident
In fact they are the trigger of the accident (http://www.pprune.org/rumours-news/502079-a330-a340-ead-aoa-probes-7.html#post7604713)

A trigger with involvement of Design, Authorities and Operator (carrier).

That put a complex scenario in the hands of a crew simply not capable to deal with.

Just training is enough? Even a designer could no be able to timely solve some similar (or more complex) issues.

captplaystation:

Sad to say, ain't that the truth . . . . . . whilst most of us are overwhelmed with incomprehension as to how these guys stalled in the cruise, and remained stalled all the way to the sea. . . it is incumbent upon us to be humble enough to acknowledge that maybe, just maybe, we could've screwed up in exactly the same way.
(http://www.pprune.org/rumours-news/502079-a330-a340-ead-aoa-probes-7.html#post7604725)
:ok:

[RR_NDB]

Hi,

Reading again on Thiels NWA 722 (Stony Point) (http://en.wikipedia.org/wiki/Northwest_Airlines_Flight_6231) in that bad day for 727´s (TWA Flight 514) (http://en.wikipedia.org/wiki/TWA_Flight_514) we can remember how difficult can be the diagnosis of certain failures. A simple interface was capable to mislead the Flight 6231 crew probably creating to them a "high speed mental model".

A complex System under multiple failures (bad data, etc.) processing this garbage and presenting it could easily transform a simple and brief failure into an unsolvable problem. This is due HF or a "scare design"?

Obviously HF would be present. :} But, IMHO this is an engineering problem.

We may say the simple 727 interface was not adequately redundant (lacking AoA, important when air data was unreliable).

But when you fed a complex System (with authority of "hard limits", protections, etc) with e.g. unreliable AoA probes, obsolete AS probes, etc. :{

:mad:

[Turbine D]

Hi Lyman,

In regards to the symmetrical located AoA sensors, 1 & 2, if they simultaneously lock up then #3 (the odd man out) is disregarded by the system logic, correct? The same would be true of the pitot probes 1 & 2, again, correct? It seems to me there was a photo of the sensors and probes on the A330 in the AF447 thread that depicted their location near the nose and before the nose blending into the fuselage shape. But, on the A320, the AoA sensors, 1 & 2 are located much farther back, rearward of the forward doors.

If you recall the A320 Perpignan accident, the AoA sensors, 1 & 2 locked up simultaneously at high altitude at a cruise angle. However, the cause was the sensors not being covered during a high pressure water cleaning operation (a procedural error) and they took on water internally (bearing area) prior to the final detail painting step. The plane sat for three days prior to the test flight and during the flight they did simultaneously freeze at altitude unbeknownst to the pilots. The AoA sensors are not designed to be waterproof, neither the Goodrich or the Thales. The certification details are given in the BEA final report.

IMO, the location of the AoA symmetrically located sensors on the A320 would not be subject to as much pounding water as would the A330 AoA sensors because of their location. In other words, the problem with the AOA sensors on the A330/A340 may be associated with water intake based on location and the new conical added plate, not ice crystal formation at altitude.

[Lyman]

I think the probes discussion is very important. However the immediate problem is what the system will do with corrupt, but stable data.

Since we have evidences of problems that are superior to probe failure, i am hanging out on the other thread.....there are safety issues that supersede performance data?

I am at a loss how threads can for so long a time focus on the sizzle, not the steak. The EVA experienced a LOC. not a UAS, a loss of control

I agree the 320 appears to have the superior layout, :ok:

So my conclusion in the interim is, probe failures happen to all aircraft. Some are less capable in this regime than others.

That may not prove out, statistics for en masse and generalised reported failures are not available?

[flash2002]

Dozy wrote in post 67:

@CONF - I'm not in denial - the alpha protections follow pilot input up until the point safety boundaries are reached and will maintain that, in much the same manner as the T7 will progressively counter input through the force-feedback. Of course, as the Mach number increases, the pitch down will also increase, but it's not going to suddenly force the aircraft into a significant dive, in fact it won't descend at all if corrective action is taken.

Well dozy, you are wrong. Some information regarding the incident from my company:

In the recent event, all three probes became frozen and the aircraft erroneously detected an ‘incorrect angle of attack’ scenario which triggers Alpha Prot. As the AOA probes are frozen Alpha Floor will not be activated as the triggering AOA limit is not reached . As designed, the aircraft protection activated and a nose down input was introduced. Unfortunately, as the probes were frozen (and continually sensing the incorrect alpha), the AOA did not reduce and the flight controls continued to demand a pitch nose down. Within 10 seconds, the aircraft had achieved 12 degrees nose down pitch and a rate of descent of 9400 fpm.
Aft sidestick input had no effect and the aircraft continued to pitch nose down.

Turns out it WILL put the aircraft in a sudden and significant dive that will only become worse. 10 seconds is about 1600ft at that rate, a dive!!!

Turning off 3 ADR's might have saved them but it could have made their day significantly worse:

Back Up Speed Scale (BUSS), which is fitted onto newer aircraft relies upon AoA inputs. It must not be used, so DO NOT switch off more than 2 ADR’s.

[flash2002]

Yeah sorry we crossed I missed your post while searching for dozy's and quoting it.

[Chris Scott]

I wrote this here a few days ago, and repeated it yesterday on the “How safe is (airbus) fly by wire? Airbus A330/340 and A320 family emergency AD” thread (on Tech Log):

“...sometimes used to ponder, during my walk-rounds, on the pros and cons of locating Pitots 1 & 2 at precisely symmetrically-opposite positions on the fuselage (Pitot 3 being the odd one out). Then I would remind myself that the same applied to the AoA probes. It seemed to me that this might be a recipe for (roughly) simultaneous ice accretion of numbers 1 & 2."

Later, in answer to Lyman, I wrote:

“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.”

[A33Zab]

“...sometimes used to ponder, during my walk-rounds, on the pros and cons of locating Pitots 1 & 2 at precisely symmetrically-opposite positions on the fuselage (Pitot 3 being the odd one out). Then I would remind myself that the same applied to the AoA probes. It seemed to me that this might be a recipe for (roughly) simultaneous ice accretion of numbers 1 & 2."

Symmetrical position of AoA vanes is very common, the longitudinal position of A33/A34 is much further aft (aft of pax door#1) than e.g. the T7 (just below the flightdeck aft window).
Airbus don't want the surrounding skin to be heattreated so the base of the AoA sensor lacks a heating element this in contradiction to the T7.

....did the AoA sensors really iced up?


An A330 aeroplane, equipped with Angle of Attack (AoA) sensors with conic plates installed, recently experienced blockage of all sensors during climb, leading to autopilot disconnection and activation of the alpha protection (Alpha Prot) when Mach number was increased.
Based on the results of the subsequent analysis, it is suspected that these conic plates may have contributed to the event. Investigations are on-going to determine what caused the blockage of these AoA sensors.
Blockage of two or three AoA sensors at the same angle may cause the Alpha Prot of the normal law to activate. Under normal flight conditions (in normal law), if the Alpha Prot activates and Mach number increases, the flight control laws order a pitch down of the aeroplane that the flight crew may not be able to counteract with a side stick deflection, even in the full backward position.
This condition, if not corrected, could result in reduced control of the aeroplane.
condition on Airbus A330 and A340 aeroplanes.
AoA conic plates of similar design are also installed on A320 family aeroplanes, and installation of these AoA sensor conic plates was required by EASA AD 2012-0236, making reference to Airbus SB A320-34-1521 for in-service modification. This requirement has now been removed with revision 1 of that AD.
To address this condition on A320 family aeroplanes, Airbus developed an “AOA Blocked” emergency procedure, published as a temporary revision (TR) of the Airplane Flight Manual (AFM), to ensure that flight crews, in case of AoA sensors blockage, apply the applicable emergency procedure.
For the reasons described above, this Emergency AD requires insertion into the AFM of the Airbus TR.
This AD is considered to be an interim measure and further AD action may follow.

Here it says AoA blockage due to in-service modification of conical plates. (no mention of icing here).
They removed the requirement of installing conical plates but NOT TO REMOVE the conical plates from factory delivered and in service modified aeroplanes.

Question: Will a max. 4° elevator down - due to activation of Hi AoA protect - command a 12° pitch ND?
Or will the Anti Pitch Up Compensation - blended in from M 0.65 to max 6° elevator down - had more effect on the 12° pitch down?
(New procedure states: DO NOT INCREASE SPEED !!)

@CONF: I have to say it again……..sometimes manual pitch trim can be your best friend!

[Lyman]

A33Zab...

Yes, symmetrical positioning of redundant sensors is common. 'Commonplace' and 'traditional' does not mean such positioning is not arbitrary.

Positioning sensors such that their relative ability to sense is dependent on common condition is not necessarily rational.

It merely makes them susceptible to failure when the ambient condition is unexpected

Why is it always ICE?

In the current condition, the symmetry is flawed....

Predicting (and making dependent) any multiple system on the 'expected' is
not sound.....

At the bottom of all this is the utter lack of a simple test for failure....

"Let's fail AoA, and see the response..."

"Let's fail Airspeeds, and assess autotrim..."

"Let's allow the ASI to drop to zero, and Test STALL WARN..."

"Let's put some knackered crew in the sim, and stuff the A/P...."

"Let's study manual handling in divergent Law/axis..."


What have I missed?

Oh... Isn't THS busy in this case, workin' ND ? Does the new AFM include, "Without Delay"?

[CONF iture]

@CONF: I have to say it again……..sometimes manual pitch trim can be your best friend!
In case of total loss of FBW or ELEV FAULT, but there is nothing easy in it.
Now if you think you can counter a protection with the use of the trim wheel, you have all my respect and I'd better call you Chuck Yeager.
Nevertheless note that the Airbus AFM Temporary Revision has still no mention of the manual pitch trim to counter the elevators ...

[Chris Scott]

Reading between your lines, do I detect a whiff of doubt that the AoA blockage was ice of any kind/origin?

Re the recovery: just a few initial thoughts, with hindsight from my comfy armchair.

It will be interesting to see if the crew used “speedbrakes” (airbrakes), and I wonder if they would have any effect on pitch trim on the A330. (If they were splitable, like on some a/c, you could use only the outers to generate pitch-up.)

Did we agree on the AF447 thread that manual THS is physically possible in Normal Law? Some early jets like the B707 provided (yes!) automatic stabiliser-trim (up) at high Mach,to counter the nose-down effect of Mach “tuck”. So perhaps it might not be such a challenge as you are suggesting, Conf_iture?

The cure must be to reduce Mach by going down and (at least) not allowing the TAS to increase. The latter doesn’t necessitate a reduction in IAS. Selection of idle thrust aggravates the trim, malheureusement, but if the THS is available that effect can be countered. Meanwhile, in case one hasn’t enough to do already, should one consider turning out of the “airway”, as per an emergency descent?

[Lyman]

It was not ICE that crumpled 038 into a ball. At the worst, it was contributory. The problem was a mechanical deficiency (sic) that was modded/remedied in a device not intended to de ice, the FUEL OIL HEAT EXCHANGER. That is the story, and some one is sticking to it.

The 320 is not at risk. It is included in the AD for safety and or red herring' sake. Placement of probes? Possibly, but that means probes are not the problem either, at least potentially.

Simultaneous failure of probes, pitots, Statics.

Three day old fish. Thales is having a rough patch.

[CONF iture]

Some early jets like the B707 provided (yes!) automatic stabiliser-trim (up) at high Mach,to counter the nose-down effect of Mach “tuck”. So perhaps it might not be such a challenge as you are suggesting.
I think the idea behind is somehow different. That 707 auto feature was most probably designed as such ?
To me the use of the trim wheel to counter the unjustified activation of a protection is much more than a challenge, it is pure Experiment.
I believe that if it was the preferable solution, it would be the one mentioned in the Airbus AFM Temporary Revision.
I'm not a big fan of the double ADR OFF selection either but it is IMO a piece of cake compared to what A33Zab is suggesting.
Without any hesitation my recommendation, for what it worth, would be to install a very accessible switch to both pilots to simply cancel any undue activation of a protection.
It would be for sure a Tsunami in regards of the ideological concept as advertised by BZ, but on the technical side it would be nothing.
Am I asking for the unreasonable ... ?

[A33Zab]

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

Learmount link (http://www.flightglobal.com/blogs/learmount/)


The ability to remember, however complex our digital aeroplanes have become, that in the end they are still just aeroplanes, is a priceless asset for pilots.


The following event would have been confusing but, as ever, a couple of cool heads, some systems knowledge, and an ability to revert to basics can save the day. Here goes:


"Since the European Aviation Safety Agency issued an emergency airworthiness directive requiring airlines prepare their Airbus A330 (http://www.flightglobal.com/news/articles/details-of-a330-angle-of-attack-sensor-incident-emerge-379921/) and A340 (http://www.flightglobal.com/landingpage/A340.html) pilots to cope with the effects of stuck angle of attack vanes, more detail has emerged about the nature of the event that sparked the new measures.
"As the A330 (http://www.flightglobal.com/landingpage/Airbus%20A330.html) was climbing through FL113 (11,300ft) at about 250kt indicated airspeed, with the outside air temperature at minus 12C, the angle of attack vanes became stuck at an indication of 5°.
"Airbus (http://www.flightglobal.com/landingpage/Airbus.html) says it is keeping its mind open as to whether this was icing-related or some other fault, but icing appears likely because the unit, manufactured by Goodrich, became unstuck during the descent.
The pilots had no direct indication of the stuck vanes and continued to climb toward cruise altitude. But at FL310, as the Mach number increased, the effect of the stuck vanes showed itself through the activation of the "alpha prot" stall-protection system, which pitched the nose down.
"Effectively, the combination of high Mach number and a falsely-indicated 5° angle of attack misled the A330's flight-control system into concluding the aircraft was approaching a high-altitude stall, so it took automatic action to reduce the angle of attack.
"At all times during the flight, says Airbus, the indicated airspeed was reading correctly, but the stall-protection system depends on angle-of-attack readings.
"The crew levelled the aircraft and 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 reviewed the situation and decided to divert. During descent, Airbus notes, the angle-of-attack vanes became unstuck once more.
"When the event occurred Airbus notified its customers, via an all operators telex, as well as EASA, under the mandatory occurrence reporting system. But there has been no call for a formal incident investigation.
"After consultation with Airbus, EASA issued an emergency airworthiness directive requiring airlines to amend A330 and A340 flight manuals to include a drill for pilots to adopt if this situation occurs. This drill largely reflects the actions of the incident crew: level out, taking account of safety altitude, maintain the same airspeed, then trip out two of the three ADUs to achieve alternate flight control law, which disengages the angle-of-attack protection.
"Airbus has praised the pilots of the A330, commenting that their systems knowledge and airmanship was good. During the remainder of the flight to the diversion airport, which was uneventful, Airbus noted that they kept a close eye on their attitude, power and airspeed relationship, because neither the artificial horizon nor the airspeed indicator was affected by the angle-of-attack sensor problem.
"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.

[Chris Scott]

A33Zab,
Thanks for quoting David Learmount’s piece from a month ago. The rest of us have been a bit slack in missing it, and I didn’t even know he had a website.

Looks like freezing of trapped water again?

Conf_iture,
For what it’s worth, my comments on splitting the spoilers (part of the jammed-stab drill on the B707, but I don’t think it’s possible on Airbus FBW aircraft) and use of THS in opposition to FBW-originating down-elevator were mainly to illustrate the severity of the problem facing this crew, and the lack of options other than that of finding a way out of Normal Law (without making the situation worse). They seem to have done a good job.

[A33Zab]

Thanks for pointing out the date, I completely missed that and thought it was new information.

[Lyman]

As remote as it may sound, with simultaneity comes the occasional surprise.

Conical Plates? I would first look to reject something peculiar to altitude, such as minute deformation of the pressure vessel. At 11.5, the pressure altitude has been reached, and passed, the skin is starting to flex independently of the outside pressure.

Odds? 10,000/1. Worse?

If loss of two ADR creates Alternate, and BUSS takes it to DIRECT, should (can) BUSS be deselected? Or preferred?

[A33Zab]

If loss of two ADR creates Alternate, and BUSS takes it to DIRECT, should (can) BUSS be deselected? Or preferred?

During BUSS operation (3 ADR OFF) the flight continues in ALTERNATE (less Hi speed protection).
BUSS can be deselected by restoring 1 ADR, don't know if the Hi speed protection is also restored.

Odds? 10,000/1. Worse?

Cheers, they're on it....:O

[RR_NDB]

CONF iture:

Without any hesitation my recommendation, for what it worth, would be to install a very accessible switch to both pilots to simply cancel any undue activation of a protection.
(http://www.pprune.org/rumours-news/502079-a330-a340-ead-aoa-probes-8.html#post7616898)

A dangerous mechanism of protection must be "fired" when required.


Am I asking for the unreasonable ... ?

The process of change is a complex one.

It would be for sure a Tsunami in regards of the ideological concept as advertised by BZ, but on the technical side it would be nothing.



:ok:

[737Jock]

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.

[HazelNuts39]

Pursuing the academic point, does alpha-prot have authority to drive the elevator to its AND limit?

From the ATSB (interim) report on QF72:
The aircraft manufacturer advised that the 10-degree elevator command associated with the first in-flight upset, was the result of 4 degrees of alpha prot and the 6 degree authority of the anti pitch-up compensation. The 10-degree command was close to the worst possible scenario that could arise from the design limitation in the AOA processing algorithm.

[DozyWannabe]

(I would just guess that at the point the vanes might become unstuck with full AND elevator and gobs of ANU THS might be problematical.)

Seeing as how the protections are supposed to keep the aircraft within the safe flight envelope, the restoration of the correct values should technically result in a return to straight-and-level, as long as the trim wheel isn't being held in place too long. One advantage of the values being computed before control signals are sent is that the elevators should rapidly return to where they should be.

I'm intrigued by the mention of an "ideological concept", and I'd love to know what it is...

[CONF iture]

I'm intrigued by the mention of an "ideological concept", and I'd love to know what it is...
Protections to protect the airplane from pilots who make mistakes.
But Never was mentioned that pilots could be necessary to protect the airplane from FCS that would make mistakes as well.

[DozyWannabe]

Protections to protect the airplane from pilots who make mistakes.

And to allow pilots to command manoeuvres up to the physical limits of the flight envelope without worrying about falling out of the sky, but that doesn't get brought up as often.

But Never was mentioned that pilots could be necessary to protect the airplane from FCS that would make mistakes as well.

It might not have been heavily publicised, but the procedures enabling a pilot to do so have been in the flight manual for as long as the aircraft has been around.

[jcjeant]

It might not have been heavily publicised, but the procedures enabling a pilot to do so have been in the flight manual for as long as the aircraft has been around.
Well ... it was just a new procedure (that was not in the flight manual from as long a particular airplane has been aroud) released some weeks ago and it has been heavily publicised ....

[CONF iture]

It might not have been heavily publicised, but the procedures enabling a pilot to do so have been in the flight manual for as long as the aircraft has been around.
Must be why Airbus had to publish a Temporary Revision of their Aircraft Flight Manual ... ?
Why didn't they simply remind to all the reference of that procedure as it is already part of their flight manual ?

To kill the protections should be done through a single switch, easily accessible to both crew members.
To have to switch 2 ADRs OFF on the overhead panel in order to "prevent the flight control laws from using two coherent but unreliable ADR data" is a **** procedure when your airplane started to behave on its own against any logic.

[A33Zab]

But when manual trim is used to counter alpha prot, you get the full AND value


The nose was low and couldn't be levelled by SS aft.

Please explain to me why manual trim to full AND is required to counter alpha prot - in this case - when they wanted the nose to go up.

[fran91000]

Somme more informations :

2 ADs edited from EASA on 2012/12/17


http://ad.easa.europa.eu/blob/AFM_TR286... 2-0264-E_1

http://ad.easa.europa.eu/blob/easa_ad_2... 2-0264-E_2

must register for access EASA

in second AD :



Applicability:
Airbus A318-111, A318-112, A318-121, A318-122, A319-111, A319-112, A319-113, A319-114, A319-115, A319-131, A319-132, A319-133, A320-111, A320-211, A320-212, A320-214, A320-215, A320-216, A320-231, A320-232, A320-233, A321-111, A321-112, A321-131, A321-211, A321-212, A321-213, A321-231 and A321-232 aeroplanes, all manufacturer serial numbers, if Airbus modification (mod.) 153213 or 153214 has been embodied in production, or Airbus Service Bulletin (SB) A320-34-1521 has been embodied in service.

Reason:

An A330 aeroplane, equipped with Angle of Attack (AoA) sensors with conic plates installed, recently experienced blockage of all sensors during climb, leading to autopilot disconnection and activation of the alpha protection (Alpha Prot) when Mach number was increased.
Based on the results of the subsequent analysis, it is suspected that these conic plates may have contributed to the event. Investigations are on-going to determine what caused the blockage of these AoA sensors.
Blockage of two or three AoA sensors at the same angle may cause the Alpha Prot of the normal law to activate. Under normal flight conditions (in normal law), if the Alpha Prot activates and Mach number increases, the flight control laws order a pitch down of the aeroplane that the flight crew may not be able to counteract with a side stick deflection, even in the full backward position.
This condition, if not corrected, could result in reduced control of the aeroplane.
EASA issued Emergency AD 2012-0258-E to address this potential unsafe

[Kimon]

Zeitgeschehen - Rio - Paris: Todesflug AF447 - N24 Dokumentationen (http://www.n24.de/mediathek/video_1598292.html)

Vid won't play from my end.
Maybe from yours.

[DozyWannabe]

I don't mean to kvetch, but wouldn't that be more appropriate in the thread about AF447? This thread's about a completely different incident.

Incidentally, it looks like there's a bug in the site's code that's causing the video to not load for now. It's likely to be fixed shortly

[jcjeant]

Unless the video was made with this:
FOQA flight animation and Simulator debriefing station - CEFA Aviation (http://www.cefa-aviation.com)
from the FDR data .. I think it's another useless video (journalist essay) bringing nothing new about AF447 ...

[A33Zab]

and when this is done during an alpha prot pitchdown, you can observe the elevators smoothly go full AND


I doubt that.

From an academic point of view:

When alpha protect is triggered


AP disconnect
Nz law is replaced by Hi AoA Law
Auto pitch trim is limited from entry point AoAprot. to 2° AND
Elevator is 4° ahead AND
In Hi AoA Law AFT stick commands an AoA change from AoA prot (stick free) to AoA max (stick full aft).

In this case sensed AoA = AoA prot and - due to increasing Mach - AoAprot. ~ AoAmax (this is the referred Red over Amber on speed display), hence the lack of ANU control in AFT stick.

Now if the pitch wheels are cranked up (ANU) until level, this still doesn’t change the sensed AoA (remains blocked @ AoAprot) so there will be nothing to correct for by the automatics.


I would still wonder about the aircraft response if and when the vanes unstuck with full AND elevator and some considerable degree of ANU THS trim in place when this occurred.

Now that would be indeed very academic, but if this will be possible at all it would depend on other inputs. (Pitch, SS input, Airspeed)

Definitely it will be not a smooth transition into normal Nz law.

[CONF iture]

Now if the pitch wheels are cranked up (ANU) until level, this still doesn’t change the sensed AoA (remains blocked @ AoAprot) so there will be nothing to correct for by the automatics.
But do we have the information to confirm one of the following :

Elevator will trail by 4 deg
Elevator will not move
Elevator will fight up maybe to the max ND
What else ?

And which other feature (http://www.pprune.org/7620030-post158.html) we're not necessary aware of would play a role ?

Any other data (http://www.flightglobal.com/blogs/learmount/2012/12/airmanship-lives.html) Learmount could be given to share ?

[A33Zab]

From the QF72 (http://www.atsb.gov.au/media/3532398/ao2008070.pdf) (AoA spikes) final report:

Table 19: Characteristics of elevator control mechanisms



High AOA protection
Control law: Normal law only
Speed: Any
Altitude:Any (must exceed threshold for at least 2 seconds when aircraft below 500 ft)
Configuration: Any
Maximum authority: 4° elevator movement (at time of pitch-downs)

Anti pitch-up compensation
Control law: Normal or alternate law
Speed: Mach 0.65 or more
Altitude: Any
Configuration: Landing gear retracted, flaps up
Maximum authority: 6° elevator movement


High angle of attack protection

Aerodynamic stall in large aircraft is a potentially dangerous condition and aircraft manufacturers incorporate design techniques to prevent it.
On the A330/340, the FCPCs continually monitored the AOAFCPC input.
If the master FCPC detected that this value exceeded a predefined threshold (alpha max), then it issued control orders for a nose-down elevator movement to reduce the AOA and prevent a stall.
High AOA protection was only available when the aircraft was in normal law.
If AOAFCPC input was outside the range of -10° to +30°, the control law reverted from normal law to alternate law, and the protection was therefore no longer available.
In addition, when the aircraft was more than 500 ft above ground level, the protection was effective immediately; when the aircraft was below 500 ft, it was only active after AOAFCPC input exceeded the threshold for 2 seconds or more.
The maximum authority or change in elevator movement that could result from the the high AOA protection varied depending on several factors.
The aircraft manufacturer reported that, at the time of the two in-flight upsets, the maximum authority was about 4° of elevator movement.
The protection would be applied until the aircraft’s AOA was reduced below the stall angle.

Anti pitch-up compensation
Anti pitch-up was a mechanism included in the A330’s control laws to compensate for a pitch-up* tendency at high Mach numbers and high AOA.
The compensation was only available above Mach 0.65 and when the aircraft was in a ‘clean’ configuration (that is, with the landing gear and flaps retracted).
Its maximum authority was 6° of elevator movement.

*
On a statically stable aircraft, the centre of lift is situated behind the aircraft’s centre of gravity and an increase in AOA would lead to an increase in lift and a restorative tendency to pitch the aircraft nose down.
However, at higher Mach numbers and AOAs, it is possible to stall the wing tips.
On a swept-wing aircraft, the centre of lift will then move forward, leading to a reduced nose-down reaction to increasing AOA, reduced stability, and a tendency to pitch up.



Might not this constant AOA vane position, as displayed as characteristic speed, indicate an AOA condition at, or even beyond, alpha max?

IMO alpha prot can be @ alpha max (in this case and normal for 5s @TO) but never beyond, with normal operating AoA vanes the alpha protect will kick in before alpha max.

[HazelNuts39]

Further to A33Zab's reply -
At M=0.81 alphamax is 5 degrees, so it is quite possible that alpha max was exceeded.
However, in the QF72 accident alpha max was exceeded by a large amount. From the QF72 Final Report (5.2.2):
The 10° nose-down elevator command was very close to the highest magnitude possible from the EFCS’s two corrective mechanisms. The second AOA spike of 50.6° resulted in the AOA value used by the FCPCs (AOAFCPC input) being 26°. If the AOAFCPC input had been over 30°, the EFCS would have reverted to alternate law, which would have resulted in one of its corrective mechanisms (high AOA protection) not being active.

[CONF iture]

Interesting to note how the ATSB can be much more informative than a BEA report ...

[jcjeant]

Additions (conical plates) were added to the AOA sensors to improve the functioning of these
Occurs some time after the Eva Air incident
An EAD is issued (and nothing better is find in this EAD that what the pilots of Eva Air made) "shortly" after and conical plates are eradicated
Who first decided to add these conical plates?
How (what tests) and by whom they were certified ?
This looks like the same thing to certify a improved life jacket (by adding buoyancy material) and the first who must use it sink like a stone instead of floating

[hetfield]

Interesting to note how the ATSB can be much more informative than a BEA report ...

.......indeed!

[DozyWannabe]

Don't see it myself - what's in one (that was available) that's not in the other?

[CONF iture]

Do you mean a report will be finally published ?
We have so little information on this event, did you actually turn off all three ADRs ? Was the aircraft equipped with the BUSS ?

[DozyWannabe]

Imagining if the involved pilots turned off all three PRIMs to enter Direct Law with sidesticks already at FULL AFT postion: you will enter a high-G (no g protection now) pitch up which will result in structural damage or enter a REAL stall!
How do I know this, because I was sitting on the R/H seat instructing a new capt. Thank almighty we made ALIVE that day :ouch:

More to the point, what in the name of Hades did that Captain think he was doing pulling full aft while trying to turn off the PRIMs?

That said - the lack of proper training for flight crew in terms of how the systems affect the aircraft is nothing new - wasn't a contributing factor to the Adam Air 574 crash down to the Captain not realising that the systems should not be reset without the aircraft being straight and level?

[JammedStab]

Did it happen again?

Incident: Lufthansa A321 near Bilbao on Nov 5th 2014, loss of 4000 feet of altitude (http://avherald.com/h?article=47d74074&opt=0)


Incident: Lufthansa A321 near Bilbao on Nov 5th 2014, loss of 4000 feet of altitude

By Simon Hradecky, created Tuesday, Nov 18th 2014 17:11Z, last updated Sunday, Dec 28th 2014 22:22Z

A Lufthansa Airbus A321-200, registration D-AIDP performing flight LH-1829 from Bilbao,SP (Spain) to Munich (Germany) with 109 people on board, was climbing through FL310 out of Bilbao about 15 minutes into the flight at 07:03Z, when the aircraft on autopilot unexpectedly lowered the nose and entered a descent reaching 4000 fpm rate of descent. The flight crew was able to stop the descent at FL270 and continued the flight at FL270, later climbing to FL280, and landed safely in Munich about 110 minutes after the occurrence.

The French BEA reported in their weekly bulletin that the occurrence was rated a serious incident and is being investigated by Germany's BFU.

The occurrence aircraft remained on the ground in Munich for 75 hours before resuming service on Nov 8th.

The Aviation Herald learned that the loss of altitude had been caused by two angle of attack sensors having frozen in their positions during climb at an angle, that caused the fly by wire protection to assume, the aircraft entered a stall while it climbed through FL310. The Alpha Protection activated forcing the aircraft to pitch down, which could not be corrected even by full back stick input. The crew eventually disconnected the related Air Data Units and was able to recover the aircraft.

Following the occurrence EASA released emergency airworthiness directive 2014-0266-E_1 stating:

An occurrence was reported where an Airbus A321 aeroplane encountered a blockage of two Angle Of Attack (AOA) probes during climb, leading to activation of the Alpha Protection (Alpha Prot) while the Mach number increased. The flight crew managed to regain full control and the flight landed uneventfully.

When Alpha Prot is activated due to blocked AOA probes, the flight control laws order a continuous nose down pitch rate that, in a worst case scenario, cannot be stopped with backward sidestick inputs, even in the full backward position. If the Mach number increases during a nose down order, the AOA value of the Alpha Prot will continue to decrease. As a result, the flight control laws will continue to order a nose down pitch rate, even if the speed is above minimum selectable speed, known as VLS.

This condition, if not corrected, could result in loss of control of the aeroplane.

The EASA requires as immediate emergency action that the flight crew operating manuals must be amended with a procedure to keep only one Air Data Reference Unit operative and turning the other two off in following cases:

- the aircraft goes into a continuous nose down pitch movement that can not be stopped by full backward stick deflection
- the Alpha Max (red) strip completely hides the Alpha Prot strip (black/amber) without increase in load factor
- the Alpha Prot strip rapidly changes by more than 30 knots during flight maneouvers with increase in load factor while autopilot is on and speedbrakes are retracted

[tubby linton]

The latrst OEBs for A320F and A330/340 issued by Airbus are directly related to the Lufty incident. The incident appears to have been caused by two AOA probes producing similar but erroneous data and consequently the architecture disregarding the correct third one.
The answer to the problem is to turn off two ADR and force the aircraft into Alternate Law. The more serious question is why are AOA probes icing up in the first place?There are two types of probe I believe and it will be interesting to see which one was fitted to the Lufty aircraft.

[DeafOldFart]

I'm just a Silver C and NPPL type, with a logical mind.... and reduced hearing.
My car has no AoA instrumentation, probes or whatever, but in the event of speedo failure, a very accurate GPS display tells me what I need to know.
Why have Airbus missed the trick of using GPS data as a correlation reference??!!
Okay, vertical speed is less accurate than horizontal, but the math of deriving a reasonable approximation of airspeed is pretty basic, especially if there is an established figure from a period of previous flight.
Instead of horns blaring, a little note on the HSI or somewhere would tell the pilot that an approximation was being made until the pressure instruments came back on line in a few minutes... and attitude would be kept within sensible boundaries till further notice!! Equal amounts of blue and brown with a groundspeed inside a sensible historical range might be better than joystick wrestling....
I did suggest this at a CRM lecture with CAA reps present, wonder if it has been noted?
Don't tell me that the programming cannot be compromised by unverified input... after all, that's what the sidesticks are for

[tubby linton]

Deaf the aircraft will show GPS altitude under certain failure conditions but the only speed it can compute is groundspeed.

[LEVEL600]

Lufty planes use Goodrich AOA's, same as in XL Airways accident.

[tubby linton]

Level600 for clarity is that the one with a conic plate? I thought that the plates were meant to have been removed following an AD?
EASA orders Airbus angle-of-attack plate swap - 2/5/2013 - Flight Global (http://www.flightglobal.com/news/articles/easa-orders-airbus-angle-of-attack-plate-swap-381905/)

[LEVEL600]

I am sorry,really not sure if its configuration is flat or conical. Expect flat conf. Personally I did not see a conical plate installed on Goodrich type of AOA ever. AI/EASA probably plays with the plates game inspired by Patrick Rayn famous book:
Private Drogue knelt in the wet and beat his head on the
ground."Dig 'em small, dig 'em big, dig 'em small again .... Now
close your eyes and I'll make 'em disappear. "

[A33Zab]

AI/EASA probably plays with the plates game


The history goes like:

original flat plate --> (A320) XL airways accident --> Change to conical plate -->(A330) EVA incident --> Revert to flat plate per EAD--> (A321) LH incident --> ?

The 'new' flat plate isn't allowed to be customized (= painted in company colors) and during A/C washing the AoA sensor should be covered by the normal AoA cover and additional by a sheet of transparent PE taped on 3 sides to the fuselage with colored tape. (leaving the bottom part non-taped) to prevent water ingress.

[tubby linton]

That explains it well A33Zab

[LEVEL600]

Lufthansa probably start change from Goodrich AOA to Thales, I saw this week few planes (A319) with new AOA 1 and 2 made by Thales and old Goodrich on pos. 3…