OEB Alpha Prot
 

Does anyone have more info and supplementary info on this OEB and other incidents. via links?

It appears that the Lufhansa pilots had previous info on this, good for them.



¨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 airplane

¨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.¨

DEC 2012 ... 2 years earlier :
http://www.pprune.org/tech-log/50207...oa-probes.html

Jimmy Hoffa Rocks
AOA information is used by FAC to calculate the protection speeds like alpha prot and alpha max( actually it is AOA shown as speed). These are high AOA protections basically meant to take care of pilot induced low speed situation. Since the normal operating AOA is much lower at higher Mach/speed, the threshold at which the alpha prot is triggered is also lowered. It is something like from 13 degrees to 5 degrees. When AOA sensors are stuck at low speed(high AOA) as the speed increases alpha prot gets triggered since AOA as received by FAC is above the high speed threshold. In this case the displayed alpha prot and alpha max will also be unduly high and incorrect. Alpha prot condition is a latching condition and will cause nose down elevator as long as speed is below this false Valpha prot. This protection can only be overridden when out of normal law. Hence the switching of two ADRs to get into alternate law. A simple solution can be not have this protection in cruise where its utility is minimal as it should be possible for a professional pilot to recover from stall without ground contact(or is it?)

Remind me to never get on an Airbus again :eek:


How many accidents / incidents have to happen before they admit you can't 'pilot proof' an aircraft ?

ADR or FAC
 

Just wanted to add something to the discussion...

Turning two ADRs would force the a/c into alternate law, as would turning the two FACs off.

Considering it is the FACs that determine the speed protections surely it would be more sensible to turn these off rather than the ADRs and leave yourself with only one reference for airspeed info.

With the FACs turned off you would only lose your high and low speed protections which is a better place to be in than losing your actual airspeed? Of course you would lose yaw damping etc. but I would still consider this to be better than losing two air data units.

Please correct me if I am wrong :)

Cheers.

Magnus456
With AOA problem your actual speed displays are not affected. That data comes from Pitot static and is correctly displayed from the remaining ADR.

Magnus456,
I believe the idea was to put in place a procedure as simple as possible, finding 2 ADR switches on a single panel is maybe more practical than looking for specific switches on 2 different panels.
Of course the ideal would be to have a well identified single switch to simply kill the protections ... but is Airbus 'ready' to take that path ... !?

Was somebody playing with pressure washer again?

Blocked AoA vanes is extremely rare situation which can nevertheless have severe effect on any FBW Airbus so it makes sense to have single procedure across the fleet, especially for CCQ flyers. True that FACs OFF (by pbs) is one way to degrade minibus into altn but they are not installed on widebodies and 2 ADR OFF will get rid of protections on any FBW Airbus. BTW, there will be two references left, the other being standby.

Come again?

Magnus456
That is what caused water ingress in AOA sensors which froze after take off, setting a chain of events leading to Perpignan crash.

Ah I see. Thanks a lot.

Forgive the ignorance.

I think the FACs compute the protection speeds for display, only. It is the ELAC that computes those for the protection activation. Still, FACs OFF would bring us to ALTN, which indeed would solve the problem.

MB
FAC calculates but does not activate protections ELACs do.

True, the ELAC gets the info from the FACs, then it triggers the activation, thanks

FCOM DSC-22-40-10 When a FAC is disengaged (FAC pushbutton set off) but still valid, the flight envelope function of the FAC remains active.

So I'm not sure if switching FACs off would really solve the problem, as long as the aircraft thinks they provide valid data.

vodmor
You have a valid point. There are twenty two different ways to can get into alternate law. Each may have its own handicap. Switching ADRs may be simpler, less complicated and common to both A320/A330. So that must be the reason AB chose it.

As one of the early Bus Pilots in North America I just cant belive that these totally stupid systems have not been removed from Airbus products by now! When we first put crews through training on this aircraft {320s} it became obvious that there were so many problems caused by the totally flawed design concept that we were convinced that Airbus would wake up and fix things, but no, their only reaction was to mumble about "uneducated Canadians" and the merits of everthing French, now the launch customer for whom I worked at the time has given up on them and is disposing of the total Airbus fleet and switching to Boeing, long overdue Im afraid. In the mean time Mr Ziegler and his cohorts push their heads deeper in the sand, combine this with pilots with no real flying background and we will continue to spend time sonar searching the floors of the worlds oceans! {By the way, in case one blames my rant on any anti French bias, I live in French speaking Canada by choice and educated my kids in the French school system}

clunckdriver
Whether anti French or Airbus you are entitled to your opinion. Only thing is North American opinion is not shared by rest of the world. You can see the order book for yourself. In rest of the world where aviation is expanding Airbus proving quiet popular. Is any airline buying any aircraft in Canada at the moment?

Villas, these are not just an opinion, they are the result of dealing with a flawed design concept from day one, indeed the reaction of the Airbus staff we were dealing with at the time of the Air India "Alpha Floor" crash was simply, and I quote," The Indians are just not able to manage modern machinery", ignoring the fact that India has a huge aviation history along with turning out some of the worlds very best computer geeks and engineers, if Airbus had simply stated in training and manuals that having one F/D of and one on would inhibit Alpha Floor, {it was neither taught or in the manuals at this time} this crash would simply not have taken place.As for orders in Canada, yes, West Jet, Air Canada and a new Start Up have large orders placed with Boeing, as for the C Series, time will tell, but right now its way over budget and late, no doubt the Canadian taxpayer will pick up the tab again! By the way, I fail to see the conection between order books and design flaws, the "Bean Counters" have little or no concept of anything other than counting the beans, but that a whole other subject!

clunckdriver
I have gone through the original inquiry report of then Indian Airlines crash and airbus design has nothing to do with it. Brand new machine, unlimited visibility and comfortable morning flight.It is a mirror reflection of SFO B777 crash. In IA crash pilots switched to open descent without realising it and speed kept dropping finally 27 Kts. below Vapp. One pilot switched off his FD without other pilots knowledge. All the time they thought they are in speed mode but no one checked the FMA, there was not a single call about speed by any of them. Finally alpha floor did kick in and also pilots themselves moved to TOGA but they lost their lives because they did it 15 seconds too late. SFO B777 Auto throttle was in thrust hold both experienced pilots never checked their speed and despite much touted moving thrust levers of Boeing they didn't notice that thrust levers were stuck at idle all along, again no call out about speed, speed went 30 kts below Vapp. They also went round but little too late and were lucky to survive. I am sorry but you don't fly approaches like that. Protections are needed for these pilots only. Most pilots won't even experience them in their life time.

This does not change the fact that at this time there was no warning of the ramifications of only one F/D being on when in this configuration, at the time of this crash those of us on the type were in fact interviewd by the BOE, As for the SFO crash, words fail me,the fundementals of aircraft handling are simply not being taught in many places, no amount of "magic" can solve this, certainly more "gongs and whistles" have not proved to be the answer.

Keyword might be "a".

As mucking with FACs to degrade control law is beyond the scope of line operations, FCOM can't be used as reference to what would happen. If the operator chooses to include handling in degraded laws in post-heavy-maintenance flight tests, which computers to shutoff, how, when and with what precautions will be included in test schedule. Absolutely nothing from it is allowed to be used in line flying.

...that only one FD was active yet alpha floor activated at 135 ft RA, too late to prevent the impact so your statement:

...is quite false. Since you insist you are early bus pilot in America and so should be very well versed in Airbus, could you please explain us your misunderstanding of Airbus autoflight fundamentals? Or for that matter, fundamentals of any modern AFCS at all?

Clandestino, there were many changes to software to rectify this and other problems problems I think you will find, however although an engineer ,I havnt flown the "Skud" for at least twenty six years,[ could be longer, but my training files are not something I keep handy these days!} so forgive me if I dont recall the endless manual updates which made reporting for duty such a new experience every time, as for your out of place comments about my ability to understand "fundementals" I can only presume that you are some joy to fly with! Please try to reign in your ego and lighten up.{PS, I see you state that I am American, actually Canada is not American, well not yet anyway!}

clunckdriver
Your statements below show you are not sure whose side you are on. You wrongly blame deactivated protection(because it wasn't) in one statement while in the other you are against the modern preventive innovations. FDs had nothing to do with alpha floor. FDs when both are off ATHR changes to speed mode and that would have taken care off their inadvertent entry in OP DES . B777 A/throttle is worse in SFO it quietly went to sleep as per design and suppose to wake up but didn't. FAA has asked them to improve it.
if Airbus had simply stated in training and manuals that having one F/D of and one on would inhibit Alpha Floor, {it was neither taught or in the manuals at this time} this crash would simply not have taken place.
the fundementals of aircraft handling are simply not being taught in many places, no amount of "magic" can solve this, certainly more "gongs and whistles" have not proved to be the answer.
Surely you can't remember everything but you could always take a breather before coming out with a howler like that.

We are not discussing you or me around here.

What we are discussing is your statement where nice description of FLCH trap was made and concrete example of accident due to it given.

Problem is; FLCH trap (inhibition of autothrottle wake-up on B777 with one FD off and other in FLCH) is not applicable to Airbi, not just because there is no FLCH on them but there is no OP DES trap either and there was never one! Fundamental part is that as Indian Airlines was OP DESed into ground, any 747 can be FLCHed or 737 LVL CHGed in the same manner.

BTW, speaking about "fundementals", it's not even full 27 years yet since A320 entered the service. Not to fly it Canada for more than 26 years would be quite a feat.

Do you have anything to add or are we closing this case?

Yes, you are correct on the start up dates on the 320 in Canada, however as I stated I no longer keep a diary or training files handy,{ have enough to do with the paper work involved in runing our present company,in fact its 0400 hours here right now and am busy aranging our eAPIS for crossing into the USA today, oh how I miss having all this bumph done by dispatch!} As you semm to delight in personel attacks I have to agree with you, lets both simply can it, its a conversation of the deaf.

Do any of the thread contributors have a reference to show how the protections are processed from detection to the final stage of the aircraft applying a correction. The Fcom doesn't explain this very well.

Airbus transparency
 

Airbus needs to be more transparent, as they have been obliviously stuff that needs to be out there. ( We are not even getting into the Electrical abnormals with all the modifications that have had to be done, consequences where you can lose all your screens or comms,etc. ) Airbus needs to provide more information to pilots on this stuff, whether it is pretty or not. Airbus the truth comes out in the end. ( In normal ops when you are fatigued the 320 remains a decent safe airplane to fly when you are doing a lot of sectors and tired.)


Also ¨Airbus had simply stated in training and manuals that having one F/D of and one on would inhibit Alpha Floor, {it was neither taught or in the manuals at this time} this crash would simply not have taken place¨

Airbus stated never have on FD and on FD off, but yes should told us more about what they knew.

It´s ironic and a contradiction, to train pilots not to think outside the box.

But pilots have had to go outside the box switching off Two ADRs to get too Alternate law. Look at Lufthansa.

Here we are with people questioning wether FACs or ADRs should be switched off.

It appears that the Alpha Prot OEB is not enough, or is it ?

The OEB is quite explicit regarding the requirement to turn off two ADR. I do agree with you that there needs to be more explanation in the manuals. Today is the anniversay of the first flight twenty eight years ago of the A320 and here we are many years later still questioning many aspects of how it works.

Active Airbii pilots know where to get the stuff...their Flight Technical dept. and at AirbusWorld.

I have been trying to access Airbusworld and my airline will not give me access.

@JHR
 

Indeed HERE are those people.
They just switch off 1 ADR (the outlier but [GOOD] ADR#3 already rejected by EFCS), which took them in ALT law.

That's regrettable but NOT Airbus withholding you the 'stuff'.

Access to Airbus Flight Ops Support
 

tubby linton
I have been trying to access Airbusworld and my airline will not give me access.

Tubby, if you have any questions on any aspect of operating the Bus just raise them through your Ops Support Group and keep at them until you get a satisfactory response. It is a sad fact that many line guys don't have access to Airbusworld / Flight Operations (or any other domains on that portal) either because they don't know it exists or don't have an inclination to find out or accept a rebuttal from their company when making a request for access or information. It is also disquieting to know that so many people at the sharp end have insufficient knowledge of the machine they operate and the physical environment in which they operate. Don't stand for it - go get the information ! :D

tubby linton
Previously Airbus had given access to some TRTO instructors to airbussupply but now they have removed that access except their own instructors. All operators have access to airbusworld but it is sad that many are not aware of the wealth of information it has and are simply not interested.

You seem to have more info than we do ... but it would be another case where the System would be better advising the crew of the suspected rogue data instead of keeping them in the dark ...

Information from presentation:

Abnormal Valpha Prot
In-service event ( A321)
• At FL250, speed became managed at 290kt but the Autopilot (AP) was unable to reach the target speed. Airspeed remained around 250kt.
• At FL 310, during a L/H turn, the crew reported PFD showing Valpha-prot rising upward current airspeed (245kt).
The flight crew manually disconnected the AP
• Alpha protection activated with an order of pitch down
• Aft stick input maintained for 55 min to keep level flight at FL270
• ADR 2 switched off, leading to alternate law
• Remaining of flight performed in alternate law

• During climb, the following AOA values were recorded:
• AOA1 = 4.5° constant value
• AOA 2 = 4.5° constant value
• AOA 3 = normal behaviour
• The Flight Controls computers rejected the AOA n°3 (no cockpit effects)
• When the flight crew disconnected the AP, the Mach was 0.675.
Alpha prot =f(Mach= 0.675)=4.2°
Alpha prot activated with an associated pitch down
• The protection remained active until reversion to alternate law

Thanks for the info.
What ... ?

... is my grievance.

They need to modify the fault accommodation logic by giving information to the crew. That will improve the situation.

@CONF iture.
 

Not only this one...I'm awaiting any positive remark on Airbus on your behalf.

(no cockpit effects) is not completely true,
- the crew reported PFD showing Valpha-prot rising upward current airspeed (245kt).
and
- INOP SYS: CAT3 DUAL

(no cockpit effects) is related to the EFCS rejection of ADR 3.

55 min with continued SS deflection makes us wonder what and with whom this may have been discussed?
Home base calling TLS during lunch hour?

But anyway, what to announce? when 2 out of 3 supplies equal but erroneous data, the median being at the same value and the 3rd source deviating from it.

ECAM MSG: NAV SOMETHING WRONG ?

Did materialize during a turn due to G increase - not much time to react.
So much stuff can lead to such STS - not really an indication.

NAV AOA DISCREPANCY could be IMO the most logical and informative option.