Infallible?
 

Hardcore

I have to disagree with your premise that.. "every aviation regulatory body for every country in the world which allows Airbus to fly into it's airspace subscribes to the infallibility and redundancy of the Airbus Alpha floor protection system." I don't believe you will find any agency or credible body to say that ANY mechanical system, let alone a complex engineering system such as an aircraft, is infallible. It has been my experience that the setting of standards for such comes down to acceptable probablilities, acceptable failure rates, statistical analysis and so on and so on. I mean think about it... can anyone say that every component of every aircraft is perfect, right out of the factory? No.

As we all know, accidents are most often the result of the compounded failures of several components (usually small and insignificant in and of themselves) of the system be it mechanical, training, SOP's, ATC, handling etc. So, yes there may be a problem with the Alpha Floor system with respect other failures and if so it will be need to be remedied. But if you're looking for the system to be made infallible, aviation will grind to a halt.

Cheers

For the victorians out there.

The AOA's were not u/s as such. They were forced into a fixed position by yet to be explained actions. So what fault exactly will the comparators pick up hardcore?

For the victorians out there with minds firmly locked closed I will say it again slowly.

The aircraft found itself in a dangerous situation due to a poorly planned test/handover programme. The tests were just like any other tests for any other airplane since the wright flyer.

Additionally and unbeknown to the crew there was a problem with 2 from 3 AOA vanes in as much as they were in a fixed position.

The events that then followed the situation, approaching stall, AOA's fixed by external interference but not faulty would have also happened to any aircraft since the wright flyer.

The only comment you can make about the autotrim is that it did its job just the same as any other autotrim since the wright flyer but there are possibly question marks as to why it wasn't used manually.

The automation played absolutely no role in this and posters like smilin ed and dc8 just highlight their ignorance by asking such ridiculous questions as:

So how exactly ed do you determine which from the 3 serviceable systems are u/s? Furthermore had you listened at school let alone read and understood what has been written here you can deselect any faulty AOA sensor.

This comment of yours ed proves you are no longer living in the real world

The secret of becoming an an excellent effective accident investigator is an emotionless but open minded approach.
You show neither quality

DC 8 and smilin ed, you need to go back to aeropru and birgenair and read and fully understand what happened on those analogue aircraft. Yes they did crash.

Once you have read and understood what took place then come back here and tell me how the excel crew should have known that 2 from 3 AOA sensors were in a fixed position?

Once you have worked that one out, then add the poor planning of a critical test manouvre and you may get nearer to the real cause. Multiple Human error. It started on the ground and tragically terminated in the air.

Same scenario with all sorts of aicraft would have ended in the same way. Its tragic, but the root cause is human error.

When I used to conduct full flight tests on 4-engined aircraft, there was a strict 'Test Schedule' which defined height, speed, weight and requirement for every stage of the test.
http://i14.photobucket.com/albums/a3...rnet/zxzxz.jpg

Tests were only conducted by one of two appointed captains for each variant of the aircraft as the tests were infrequent, but demanding and it was vital that we had to be very experienced on type. New full flight test captains would first practise the entire test schedule in the simulator.

We flew with a crew we'd selected, including a highly experienced test co-ordinator who 'read the script', although I had my own 'cheat sheet' to remind me what the next test would be. We took the aircraft from over M0.9 down to stall warning, but only in accordance with the schedule and in clear airspace with no ATC interruption.

So to conduct the test in the way they did seems to violate all normal rules of flight testing. Time pressure (delayed take-off), commercial pressure and ATC pressure combined with an ad hoc approach to the test and you have a recipe for disaster.

Test points are defined for a reason; flight test pilots may not know the reason, but must stick to the test points. Rigidly. No great 'golden gloves' handling skills should be necessary for engineering flight tests (as opposed to prototype testing), but a disciplined approach to such flying is absolutely essential.

Although I have no experience of the A320 series, the aircraft clearly has a sophisticated flight control system. Forcing the aircraft into any specific law should obviously not be a routine event and if a test specifically requires 'alternate' or 'direct' law, there must surely be a specific procedure to follow?

I can't think of a much worse scenario for the conduct of a high alpha test then the scenario of this accident.

Incidentally 'Manual Trim' is slightly misleading when the tailplane angle is such that it is outside the elevator's authority to control pitch - if the tailplane angle is such that full sidestick cannot correct the aircraft attitude then the 'Manual Trim' becomes the primary pitch control until the tailplane angle is within the range for the associated speed where attitude can be controlled by elevator.

The lack of THS movement in 'direct' law in this accident is highly significant - perhaps more so than the allegedly unserviceable AoA probe(s).

Why can't those who are interested and concerned enough to voice opinions on the A320 systems at least go find an FCOM and read up on how it actually works first? You don't have to be rated to do that; you don't even have to be a pilot. This is the 21st century; the relevant FCOM chapters are easily available on the internet.

That is a misunderstanding that could have been avoided with a brief look in the FCOM. Where older aircraft used 1.3 Vs, the Airbus uses 1.23 Vs1G. Vs1G is the stall speed at 1G, whereas the traditional Vs was measured at less than 1G. The conversion factor used is Vs=0.94Vs1G, which is where the factor of 1.23 comes from.

This has nothing to do with FBW or maneuver limitations; modern non-FBW aircraft, like the ATR, also base their values on Vs1G, and thus have the 1.23 factor in their speed calculations.

The confusion arises when one assumes that "1.23Vs" refers to the old definition of Vs, not the new 1G one, which seems to imply that the new rules give lower maneuver margins. But the new rules give exactly the same maneuver margins as the old ones did.

Good Q, but has nothing to do with FBW now does it?

Where is the data that suggests something didn't work exactly as designed? What appears to have happened here is that the systems were fed poor data from malfunctioning AoA sensors; the systems eventually did realize that, concluded that something must be wrong somewhere, and handed the situation to the pilots.

How else should the systems have reacted with such a malfunction? If the computers start trying to guess which sensor is providing valid but erroneous data you really start getting interesting failure modes...

Another issue entirely is the number of incidents and accidents that have happened after an autotrimming systems puts the aircraft in a grossly out of trim situation, disconnects itself and suddenly dumps a mistrimmed aircraft into the laps of the unsuspecting pilots. But that is not an FBW issue; a 50 year old autopilot is just as capable of doing that.

Maybe what ought be remembered is this: At any time, and totally unexpectedly, a sufficient number of malfunctions could suddenly cause the Airbus FBW systems to revert to a behavior that is identical to an old-fashioned ("conventional") aircraft. It is unlikely, it is exceedingly rare, but it could happen. Thus, don't do anything in an Airbus that you wouldn't do in a B737, 'cuz it could suddenly become a B737.

Which of course everybody already lived by. Except, it would seem, the Habsheim crew and the Perpignan crew.

Good. This fleshes out those that know from those with no idea.

The aircraft was in normal pitch and roll laws (pg34).
In normal law, when approaching the stall correct function is for the auto trim to stop when Vls is reached such that the pilot has to continue to hold the stick back to induce the protections.
The flight check called for the crew to confirm autotrims stops at Vls (pg49)
Vls at 53.7T is 123kts.
The aircraft reached 123kts at 15.44.35. (pg34)
No alerts, no warnings, (pg37) no crew action (pg34)
Autotrim doesn't stop, but continues to trim back for a further 20sec.
Alpha floor as calculated by the FAC's does not activate at Vprot, possibly because it has calculated artificially low, incorrect data based on false AoA inputs.
Where else is this incorrect data reproduced? Through the DMC's as a PFD speed tape depiction of the critical speeds (hockey stick, tiger tail), which the pilots are referencing for their queues to base the test on. Maybe this explains why there’s no crew action?
The autotrim continues to trim back.
Finally, the ELACs (having failed to back up the Alpha floor based on…. you guessed it AoA inputs pg51) but now calculating Vs from the FMGC gross weight issue the STALL STALL warning. 15.45.05
The gear is down, so the roll and pitch default to Direct law, and as P2J rightly observes autotrim is then inhibited and the message “use manual pitch trim” appears on the PFD.
Yes, practiced in the simulator, but not coincidentally with a stall.
FAC1 / FAC2 deducing that the aircraft cannot stall in Normal law, send FAC1 fail FAC2 fail signals to the DMC’s. (Pg39)
When gear is retracted, pitch Alternate law is restored. (pg34).

If an aircraft is designed without control column feedback, with the only indication of impending stall artificially created and represented on the PFD, an aircraft hardly out of the factory but with 20years of service, then the calculation and depiction of that information needs to be infallable.

Can we point the finger at the pilots as the sole cause? Maybe! Do we lose the chance to isolate and identify an inherent systemic flaw. Yes

Alpha floor is part of the autothrust system.
Autothrust is not required for dispatch.
The flight manual performance figures are not dependant on the availability of Alpha floor, which is not available when dispatching without Autothrust.

Thanks,hardcore an accurate summary except for..
As I understand it the STALL STALL warning is produced by the ADIRS (ADR portion) - presumably the standby AOA probe angle via ADR 3 - nothing to do with FMGC GW - the word "stall" does not feature anywhere in FCOM 4 (FMGC). Do you know something we don't?
And as you state elsewhere alpha-floor is done by the FACs, not ELACs. By "back up the Alpha floor" I assume you mean αprot and αmax protections?

Not the sole cause - if the AOA probes had worked as advertised the crew would have done the alpha-floor test and accelerated back to normal speed.
TP

Understood / accepted the systems were not capable of handling the situation that was experienced. However, why would Airbus programme the systems to abandon functions and leave the stabiliser control surfaces in such an extreme setting. OR were they stuck in that position which was what caused the systems to abandon processing.

My concern is that whether through painting, ice or some other things, some sensors may malfunction. Certainly in operational circumstances, rather than test as this is, one would hopefully not be near critical energy situations like this. However a different combination of circumstances could see the situation occur in line ops. I can't believe an amber message is enough feedback for the crew to notice and overcome and anyway isn't the remedial action better conducted without that extreme stabiliser setting?

I hope to see some recommendations for Airbus to improve their automation, in particular the abandonment of function.

Non-pilot here, asking a layman's question.

This was a flight being carried out following maintenance work, where the expectation had to be that there might be covered sensors and other glitches. Wasn't that the point of the flight - to test all the functions of the a/c that might be affected by such oversights?

The fact that there was a problem with the AoA sensors was presumably exactly the kind of thing they were trying to flush out?

So my question is; had they been performing this test at the 'correct' altitude, would they have been able to recover the situation, in your opinion?

I'm getting confused as to whether this was a 'normal' test flight situation, from which the plane would have been expected to recover given enough height, or whether it's a basic problem with Airbus design.

Reading that Airbus Test Manual, written in the customarily weird fractured franglais, I do not understand what (p48)

is supposed to mean. "Disconnect"? How??

Also, the instruction to record the 3 AoA values and to ensure that 'The AoA must not differ by more than 0.5º when compared to the (pitch-fpa) data' is ambiguous. Does this refer to the mean AoA value, or any single AoA value?

It is not a precise flight test document, to my mind.

hardcore,

You've read the report; now go read the FCOM! You're wasting your time trying to understand what happened until you do.

For instance,

is totally wrong. THS freezes while in normal law in some situations, but going below Vls is not one of them. That the pilot needs to hold the stick back to reach an AoA higher than alpha prot has nothing to do with what the THS is doing.

Don't have an opinion on that, but one needs to consider the failure modes that "fixing" such a problem could induce. For the aircraft to end up in such a significant out of trim situation to begin with, something must have gone badly wrong that the computers have not picked up on. We wouldn't want a sick computer, when it finally realizes it has lost situational awareness, start guessing as to what might wrong and take actions based on those guesses.

Another consideration in the mix is the ability of the crew to view FMA annunciations on the PFD at high/low pitch angles.

A contributing factor cited in the 1994 A330 test flight accident was that the PFD "declutters" the a portion of the FMA annunciations at high pitch angles to increase the viewable attitude sphere. In the A330 accident this led to the crew not determining that the aircraft was in ALT*.

I am still prowling through the FCOM to find the references to this and whether this was corrected as a result of the 1994 accident, but haven't found it yet.

If the FMA was "decluttered" then important information about pitch trim etc. may not have been available.

By pressing one/both instinctive disconnect p/bs on the thrust levers

The α Floor function can be disengaged by disconnecting the auto-thrust system, and so is the associated TOGA-lock function.
The idea of that test would be to check that the αFloor function works as required, and after its disengagement, check the α Prot function at Vmin, requiring a descent at that speed.

That comparison can only be done in stable conditions, i.e "green dot" or Vls, depending on the aircraft configuration. The test engineer will have on one of the MCDUs the AIDS page containing all three AoA values. That part hasn't been done in the"Full" configuration, as they were, according to the report in HDG/VS mode.

I think that you mean, human error triying to understand what a very complicated machine that resembled a plane was doing.

I will try to explain some things from my own experience:

1.- The aircraft protections, FWB philosophy working well or not, denied the crew vital inputs to know how the airframe was performing.

2.- The lack of feedback and the 2,5 G limitation denied the crew the hability to recover the plane, they were condemned from the begining of the dive. In that situation you can tell me that the structure is going to crush at 2,5G, you can tell me that this is the maximum performance of the plane for a pull out. But if I´m going in, and I need to pull more Gs to save the plane, I will always prefer to have the option to use more Gs, even if that means destroying the plane.
By "desing" the A320 probably is going to crush at "2,55G", but I think that if you are going to die anyway is better risking a pull out at 2,6G or 2,7G than a 2,5G. Al least you have a chance.

3.- Testing a B727, the STALL warning failed. It indeed Stalled, but because we knew how a stall feeled we recovered the plane without problem.

4.- From my point of viww, a plane that changes 3 times in 40 seconds it´s flight laws in a critical condition like low speed or stall is a very complicated machine. Human error is inherent to complexity. Someone had to mind about that while desining this bird.

Very good question !

There is a possibility here that earlier into the flight, due the AOA discrepancy, one of the ADR was rejected by the ELAC, and so without caution.

Even without automatic ADR rejection, there was numerous opportunities for the system to advise the crew that all AOA readings didn’t agree.
No need to say that a simple hypothetic AOA DISCREPANCY ECAM MSG at this time would have put an early end to the flight test.


Crucial data are missing from the BEA interim report :

• Where is the graph for the third AOA ?
• Where is the graph for the vertical acceleration ?
• Where are the graphs for the FO side stick position ?
• Just too little from the CVR ...

PJ2, I believe SFLY is correct :

25 seconds before the end, the pitch was back in alternate law, but the stabilizer position did not move (?)
There is a possibility that the stabilizer was jammed (?)
There is a possibility that the pilot tried earlier to move it … with no more success than the automatic system (?)

Some elementary accident statistics here:

There have been some 4700 fly-by-wire Airbus aircraft built & operating.

Out of those, there have been 30 crashes which have resulted in a hull loss. That´s 0.6 per cent, which is not a bad percentage at all for FBW.

Probably not an entirely fair comparison, but out of some 5900 B737 aircraft (all models) bulit there have been 131 hull losses (2.2 per cent).

To claim that FBW is somehow "unsafe" and "at fault" due to this accident, which happened during a test flight which was not conducted exactly according to instructions is, in my opinion, streching it rather too far.

From LandIT
The THS setting is not "programmed" to be left at an extreme setting - the autotrim was doing it's job perfectly and the THS setting was the natural result of the low speed, the a/c was in trim.

bjornhall
Spoken like a PPL holder! Your comment
while arguably perfectly accurate denies the fact that the THS autotrim stops when AOA-protection is active, which will also be below VLS.

For those interested the THS setting in this situation cannot be increased (nose-up) by autotrim or trim wheel movement.

CONF
Most of that 25 seconds were spent in Abnormal Attitude law, with no Autotrim.

But the trim wheel should still work,so here's some THS questions for engineers/designers with specific knowledge of A320.
1. How often is the full range of movement checked? (Not required to be done by line crew).
2. What checks are done on the THS in a C check?

Incidentally my FCOM 1 says the nose-up limit of the THS is 13.5° whereas the report says it remained at 11.2° - we (or at least I) have all been banging on about full nose-up trim when it wasn't - quite.

Who told you no auto trim ? The plane was in Alt law and most of these 20s were with forward stick. Why then the ths didn't show any sign of movement toward the -5 setting matching with the 2500ft 120 Kias level-off ?

The plane was trimmed out of pitch control range, and not by the pilots, how can you seriously claim it's the pilot's fault ?

Safety Concerns:
Exactly what I wanted to know when I asked earlier, and never got an answer to, is if there is an AoA readout in the cockpit. Before driving an airplane into a situation where accurate AoA input is essential to control of the aircraft, we should be confident that at least one of the three AoA sensors is providing good data. From your question, I must assume that there is no way to adequately assess that aspect of the congtrol system. I suggest that there should be and it should be part of the preparation for that kind of test.

Hardcore hits a home run when he says:

CONF iture;
No, SFLY is not correct and the situations you cite, while possible, are unlikely but none of us will know until the final report.

Regarding the Pitch Trim Wheels, the FCOM states that:



From the FCOM:
ABNORMAL ATTITUDE LAWS
The system applies an abnormal-attitude law in pitch and roll if the aircraft exceeds any of these limits in flight.
– Pitch attitude > 50° nose up or 30° nose down
– Bank angle > 125°
– Angle of attack > 30° or < − 10° (− 15° for A319 and A321)
– Speed > 440 knots or < 60 knots
– Mach > 0.91 or < 0.1
The law in pitch is the alternate law with no protection except load-factor protection and without auto trim.
In roll it is a full-authority direct law with a yaw mechanical.
When the aircraft has recovered from its abnormal attitude, the flight control laws in effect are :
– in pitch : alternate law without protection with autotrim.
– in roll : full authority direct law with yaw alternate law.
There is no reversion to the direct law when the pilot extends the landing gear.

From the Interim Report:
At 15 h 45 min 29 s, landing gear retraction was ordered.

At 15 h 45 min 36 s, the stall warning sounded again.

At 15 h 45 min 40 s, the control law for pitch passed from direct to alternate. The bank angle reached a maximum of 59° to the left and the normal load factor dropped below 0.5 g. TheCaptain’s lateral input is practically at neutral, the longitudinal input is still forwards but is not constantly at the stop. The yaw damper orders were nil and remained so until the end of the flight.

At 15 h 45 min 44 s, the altitude reached a maximum of about 3,800 ft and pitch reached 57° nose up. The bank angle was about 40° to the left.


Although in alternate law 25 seconds before the end of the flight, autotrim (in pitch) may not have been available due to the 57deg pitch attitude at 15h 45m 44s, and loss of autotrim in Abnormal Attitude Laws. As the FCOM states, manual pitch trim is always available and takes priority over electrical control. Manual intervention on the THS was possible at all times, the possibility of the THS being jammed, notwithstanding.

Regarding being able to either view the FMA well enough to see the messages, (dusk, no sun in eyes at high pitch angle, etc), or the notion that the display is somehow "decluttered", I am not aware of such a process where it concerns either messages associated with manual pitch trim - both the amber and the red manual pitch trim messages on the PFD are clear and unmistakable. It would be of some interest to know whether the recorders actually record this message and if so, whether it was present or not.

SC is correct. This was a human error accident on a number of levels including, as I observed, planning and execution similarities to the Toulouse A330 accident.

DC-ATE;
You said:
Cover-up? That's going a bit far isn't it?

Flight Safety:

No one here is denying that there was pilot/crew error. No one here is denying that faulty sensor (AoA or other) cannot affect the flying qualities of non-FBW aircraft. What I am saying, and I think at least some others agree, is that there was a hardware, software, or training/experience problem which aggravated the situation and inhibited the pilots' ability to recover from it. That problem, or problems, need to be aired and everyone will benefit from that. Sweeping problems under the rug benefits no one.

May I intrude upon the argument with a question?

If the FACs were switched off would the FDR record that event as 'FAC failure' ?

airfoilmod do you actually know what has happened here?
are you sure you have been following events?

I will make it simple as I did in post #682

There is no magic to it. You just need to read understand and quit with your biased outdated opinions. You are out of touch. Sorry but it has to be said

Thank You
 

And that's the point you want to miss. FBW couldn't handle a little poly-urethane in a little hole (s). Like the B-2 that was programmed wet by ground crew and went in with a ridiculous deck angle, because electrons don't think, and when no allowance (training or disconnect) is available to the handling pilot, he's along for the very expensive and life-ending final flight. Got it?

AF

As Finn47 suggested a long time back in this thread, it is not entirely fair to compare accident rate of A320/330/340 with the 737.
In the first place 737 is "all series", so you are including some pretty ratty 1968 200's being operated in Africa & S America. Secondly, A320 has benefited from many other safety enhancement like EGPWS , TCAS etc which didn't exist for the first decade or two of the 737's in service life.
When all is said & done, I doubt if you compared A320/319/318/321 with 737NG ( the fairest comparison as A340/330 are of course making longer sectors hence less T/O & Ldg . . the dodgy bit, & the NG is in more "reputable" hands ) I doubt if the Airbii will be any safer, merely having different types of accidents - or at least for subtly different reasons.
More than one way to skin a cat I know, but I would rather pull 3g if I found myself pointing vertically at the Med at 1500ft & give the airframe to the EAS dinosaur collection after it's unplanned final flight (already they have plenty ) than become fish food.
Sorry but that is my take on it.
Side sticks & thrust levers that don't move ? no thanks , at least Boeing seem to have learned from Airbus's mistakes ( Oh yes mistakes, make no mistake of that ) when deciding what tactile feedback should be offered on the 777, at least some common sense prevailed there.

airfoilmod;
If I may...

Clearly electrons don't "think" but neither do hydraulic fluid or cables/pulleys. The method by which control is executed is less important than the interventions available to the crew. I think most are agreed on this.

The intervention available to this crew was manual pitch through the THS Wheel on the pedestal. While we do not know yet whether the amber message, "Use Manual Pitch Trim" was actually displayed, it is whenever the airplane is in Direct Law. Regardless, the THS manual input is always available in Normal Law/Alternate Law. Clearly, the design concept behind elevator authority could not be expected to extend to 57deg NU pitch attitude. No transport category aircraft does this - the aircraft is out of control at this stage of flight and beyond test-pilot territory, from which recovery may or may not be possible.

I think had the THS wheel been aggressively moved towards ND, there is a possibility that the aircraft may have recovered but that is pure conjecture. The secondary stall may or may not have been prevented.

What is not conjecture is the behaviour of the airplane. In the circumstances and regimes this aircraft was placed in at the altitude it was, without timely and aggressive intervention, no transport category aircraft would have survived.

The suggestion that an approach-to-stall manoeuvre be carried out at low altitude, (3000ft ASL, approx), in Config FULL/gear down, with no prior briefings as to crew actions before/during/post test, indications to be expected, etc including an "in case of...", was made, contrary to the SA CAM (Single Aisle Customer Acceptance Manual) developed by Airbus for this manoeuvre/test.




I do not believe any of the above was heard briefed on the CVR but we haven't heard the entire record yet.

PJ2

I find it difficult to comprehend how anyone can defute 'human error' when this demanding profile was flown:

• By a crew who had received no training for this type of flight.
• Outside the test point for the specific test
• In a distracting ATC environment
• Subject to time and commercial pressures

And who then continued the test beyond the point at which it should have been discontinued (due to a failed test point) and the aircraft rejected for service.

All this "Well heck, the good-ole DC-3 didn't behave like that" comment is utterly irrelevant. When a specific schedule is written, it absolutely must be adhered to - just read how ego destroyed a perfectly serviceable aircraft in the account of 'Big head' Yeager's accident in the NF-104.....
http://i14.photobucket.com/albums/a3...rnet/zxzxz.jpg
Today's flight test pilots should learn from history, but not be totally constrained by it. But they must be very familiar with the aircraft, have sufficient training and skill for the required task and not be afraid to reject commercial influence.

The aeroplane with the most complicated flight control system I've flown was the Folland Gnat; it would happily kill you if you didn't understand the system, stay within the associated limitations and have an instinctive knowledge of system failure drills. Even a pilot as clumsy and hamfisted as I was managed to cope with that! Fortunately, most large aircraft have far greater systems redundancy, but my Gnat training taught me that any flight test pilot MUST be familiar with the aircraft and the flight test procedure and must stick rigidly to the test requirements.

It is already abundantly clear that this crew didn't.

The reasons why have yet to be ascertained though.

BEagle;
Re, Well, precisely. Those were two points which, though again obvious in the Interim Report, I thought too much to bring into the discourse all at once but both are mentioned in the Report as factors at work within the overall command-and-control and planning environment.

No matter what term the overpaid aviation trick-cyclists might invent next for some fluffed-up 'safety programme', such as 'Crew Resource Management' or 'Threat and Error Management', the only thing which will really stop pilots getting themselves into this sort of situation in future is Basic airmanship!!

But that requires experience. Which these days cost a lot of money.

It is quite clear that distraction was a key ingredient in this accident.

S.F.L.Y. you asked
Nobody told me, I worked it out using the FDR readout and FCOM 1. If > 50° NU pitch, or > 30°ND pitch, or below 60kt, Abnormal Attitude law applies, which is Alternate Law in pitch with no autotrim. If you examine the readouts you will see that abnormal Attitude law would have applied for all but 5 or 6 seconds of the last 26.

The 2500ft 120 Kias level-off (your words) occurred at about 15:45:23 with the a/c in Direct law - so any movement of the THS would be done manually by the pilot. I do not know why the THS did not move - perhaps the CVR will tell us.

The HYD system page was displayed on ECAM at 15:45:48 - during the ultra-low-speed period - which may indicate that the crew were checking for HYD problems affecting the THS. Again perhaps the CVR etc...

CONF asked
I think if you compare the Captain's sidestick position in roll(direct) and the aileron deflection the two match perfectly; in pitch Direct phase the sidestick and elevator position match; when back in alternate law in pitch at about 15:45:50 there is a period of full up elevator which does not match... but that will happen in that control law by design.
TP

TyroPicard, would you develop that point for me please.

This is absolutely wrong: it was at 15:45:50 and in alternate law. At that point, the pitch had stopped dropping, wings were horizontal and IAS was 120 at 2500ft. You can even see fully forward stick (which is what Tyropicard probably designated as full up elevator) as the pitch started to increase because of the THS, untill the plane stalls again. At that time there was no unusual attitude, alternate law and full forward stick: in other words the auto trim should have shown a signe of movement. How do you explain that ? How can anybody say the crew didn't try to use manual trim?

What are the JAA certification requirements i.e. is the elevator required to be powerful enough to override the stab when it is in a full travel position?

Hi ,
The following is part of the report for QF72 pitch down event.
I don't know much about Airbus systems and was wondering if one of you folk who are expert in this area could shine some light on why these two events are not related. The similarity I see is the AOA values spiking.
I know they are different machines but are there common parts/equipment in the AOA or FAC systems?
I apologise if the observation is too simplistic.
Framer

S.F.L.Y. wrote
OK I'm with you now...
15:45:50 CAS is 40kt - Abnormal attitude law, no autotrim.
15:45:52 CAS >60kt - back to Alternate law, autotrim enabled.
15:45:55 CAS 120kt pitch zero or slightly less - now blow up the readout and look at the altitude - from the slope of the graph I estimate the V/S at 4,000'/min down... not quite a level-off! And we do not have the flap/slat position readout which is very relevant.
But if you look at the next graph below the sidestick readout you will see both elevators fully up at 15:45:50 - which is what TyroPicard actually saw.:ugh: Please don't put words into my mouth.

I tend to deal in facts - I can't explain it because I don't have all the facts. What I do know is that when a control law change occurs it takes a few seconds for ECAM to inform the crew.
15:45:52 the stall warning occurred again
15:45:58 pitch >30°ND so back to Abnormal attitude law, no autotrim.
A total of 6 seconds approx with autotrim enabled.

I am not aware of anyone posting that. As I said before "perhaps the CVR etc.."


and for CONF
I wrote
I probably should have said "may" not "will". In pitch load factor demand law (Normal,Alternate) the sidestick and elevator positions are not directly connected. If you fly stick neutral the ELAC moves the elevator to maintain 1g. Imagine a jammed THS and change the thrust/speed/config, if stick neutral the elevator will move to maintain 1g - invisible to the pilot unless you display F/CTL system on ECAM.
Without the F/O sidestick readout, the actual load factor demanded and achieved, it is impossible to be certain why the elevator is in that position. Hope that's clearer.
Regards, TP

framer
Are you referring to the Perpignan AOA on Takeoff and initial climb? That looks normal to me though I have not given it careful analysis, and the scale is too small to observe any anomalies.
There is an AOA "hump" at about 15:03:00 which matches a CAS variation exactly - after that the AOA values become fixed.
I don't see any "spikes".
TP

yeah Tyro, good point, they are frozen and not spiking. I guess I was just trying to see if it was something as simple as a bad batch of computer components or similar. Very simplistic I admit.
Framer