Is this a trick question? :)

The position of the sidestick(s) and its view from seat #3 appears to becoming an issue judging by posts in the last couple of pages. As previously noted many posts ago, the sidestick position is displayed on the PFDs when in the WoW mode.

If displaying the the sidestick position following an AP disconnect is adding too much clutter to the display, then displaying it when loss of airspeed data due to NCD occurs might be a good get me home option.

In the same situation displaying the mean AoA value plus the THS position would save one from making the, "No valid indications" comment.

OK - that's one vote for a 'sort of inertial' system and one that appears to not understand what the question means. - I'll take you up on that - do you perchance have a system diagram showing inputs to the THS system that I might learn from?

- no you may not since you do not understand the significance of the word 'lock'. I'm not sure whether that is a language problem or if you fly the a/c but do not understand it properly (as fantom said in his now 'disappeared' post). In English 'lock' means to secure something so that it CANNOT EASILY BE MOVED - as in the Airbus.

If I could have a definitive answer that will not be challenged two pages later by someone else I can move along.

That may indeed be a language problem being not a native speaker although I generally do understand what 'Locked' means.

However I did not take it literally as 'locked' in that paragraph, more along the lines the THS being at +8° (e.g. due to Auto Trim deactivated, so unless manually moved it will simply stay there but not being mechanically arrested in any way).
Bear in mind Airbus is a Company with a lot of French influence/origin, thus English documents may deviate slightly from the original French ones from time to time. My feeling is you might be over- interpreting something in their Language.
Do we have any indication that there is a possibility to literally lock the THS (in the sense you took it) ?

Hi BOAC,

I think you'd enjoy the course.

The ADC input will modify the elevator movement. The stab will be autotrimmed so the elevators return to their neutral position.

http://www.merrowresidents.org/pprune/Stabtrim.jpg

Thank you rrat - I'll wait a couple of pages and see if anyone else interprets the 'ADIRU' input differently. Are you saying, then, that a low 'detected' IAS will increase effective elevator 'gearing' which will produce a greater THS follow-up movement?

henra - it has been stated that the THS locks in one of the failure modes - ie autotrim ceases to function. Regarding 'translation', I feel that if FCOM Vol 3, Supplementary Techniques, Flight Controls, Flight Mode. (3.04.27 P3) did not mean 'locked' (in English) then it should say so?.

BOAC;

Could I put it this way -

The only known method of locking the THS position is to hold on to the trim wheel. So if the THS is > 8 degrees and held, the elevator may not be effective at more than 180 KTS.

Hi BOAC,

The "gearing" "Q pot" etc. is now done via the ADIRU input. It would probably feel "twitchy" if the real airspeed was greater than sensed. However, the elevator position to hold a given attitude would be the same and hence so would the trim position.

Hmm maybe we still have a different notion of the word 'locked'.

I understand that in Abnormal law as well as in Direct law Auto Trim is lost/disabled and the THS will stay in the last position unless manually manipulated by the Trim wheel.
However, I'm not aware that there is any kind of blockage/hindrance against manual operation of the Trim. Just the system won't do it for you any more automatically. Effectively you change plane from A to B.
Also the schematics which have been posted point in that direction.

You are trying really hard not to fall off the outrage express, aren't you BOAC.

As any other mechanical system a stabilizer can become locked, blocked, jammed, immovable, seized up........Should I continue?

http://img219.imageshack.us/img219/9...abctlfault.jpg

Just remember I did not write the word 'locked' in the FCOM please.

KBP - many expresses do not stop until they reach destination. So, for 'lock' we now read 'jammed'? Nothing to do with the cessation of removal of autotrim function. My goodness me, that took a while, but I think I saw a train approaching the station.

FWIW, wrt the visibility of the THS indication and the F/O's sidestick, two views of the cockpit - Daytime, A330, night-time, A340:

http://www.smugmug.com/photos/i-bJvf...-bJvfTcP-L.jpg


http://www.smugmug.com/photos/i-WJNx...-WJNxHQf-L.jpg

@ BOAC and others:
 

I did try to clarify to prevent discussion:

But I get the impression I failed..........

This remark is given in the mentioned FCOM 3.....when a FCTL STAB CTL FAULT is present. This was for sure NOTthe case here. The THS was free (NOT locked) to move Airplane Nose Down.

What it will say is that full elevator authority alone is not sufficient to counteract the PITCH UP THS position if this is > 8 ANU and if Speed > 180 Knots.
If THS <=8 ANU the elevator deflection alone can counteract a THS 8 (or less) ANU position.

If SS input was FWD the THS would have followed the command as designed.

@ BOAC:

The FCPC gets ADR & IR information to compensate for speed.
The IR part can't be compared to the old INU systems, this is very precise accelerometers and 3 axis ring laser gyros equipment and yes the crew is allowed to have a peek on the same signals through its PFD.

There is an interface with ATA 76 (engine controls) but these are discrete signals only and used for ground spoiler logic(T/L position), for 3rd T/R lock release and for limitation of the green servo control speed in case of a dual engine failure.

@CS:

Maybe you have better eyes then me, I need periscopic glasses to do it without interfering the guys on P1 or P2.

PJ2,
Thanks for your answer. Then, there is perhaps a (remote) possibility that a PNF could suspect inadequate pitch inputs by the PF by noticing from the corner of an eye the trimwheel moving in an unexpected way. This is probably irrelevant, however, in a tight situation.

What factors do the designers consider when setting out how far the THS can travel ? Would it have mattered much in real life if it had been limited to less than 8 degrees NU ?

@ somebody who asked manual pitch trim rate.
 

One stroke on the Trimwheel ~0.65° THS movement. (2 hydr. motors B+Y available)

DJ77;
Re your first statement, in a word, yes, I think it is possible to put together a THS wheel rolling aft out of the corner of one's eye while observing the pitch increase and the inappropriately high vertical speed but it requires a calm eye in the face of the unfamiliar and a habit of not focussing on the same thing as the other crew member. I think there's more than that: Listening to that "sixth sense" would be part of it... the fact that the air noise begins to go a LOT quieter when the pitch is still high, one begins to slowly, gently feel lighter in the seat and one can begin to actually hear the engines, as well as paying attention to whatever it is in one's belly that says things aren't good. But I think your second statement applies as well.

So if trim is sitting at 13 degrees aircraft nose up direction and you need to get it down to around 4 degrees ANU to recover, it would take 13-14 strokes on the trimwheel.

Anyone have an idea how long that might take to execute? Does trim wheel motion keep pace with the THS position on its way down to reduced trim or can it get out in front of it and let the tail catch up?

Control stick, AoA, autothrust in lites
 

Salute!

Thanks to EMIT, thanks.....

- The transition from a big stick or yoke to the "force" transducers was very easy. Like about 3 or 4 seconds on first flight. Put some pressure on the stick and the jet moved ( rolled or pitched). I flew with many fossils and newbies in the family model, and that was my experience when letting them fly.

- The family model sticks "added" the command for roll and pitch, and we could not see the other guy's inputs, nor would it have made any difference. as the stick didn't move more than a few millimeters. So I could 'help" the newbie, but if I let go he would wonder why the jet was trying to climb a bit on final approach.

- I flew three jets with the AoA indicators. The two that counted were the SLUF and the Viper. The SLUF was a Navy variant and had the "indexer" lights up on the glareshield, or on one side of the Head Up Display. This allowed us to fly the optimum AoA on approach without calculating weight versus speed. AoA is AoA, regardless of your weight.... duuuuuh. We still had to do a rough, rule-of-thumb, correlation of our indicator with the airspeed we expected. This was due to leading edge flaps that allowed a higher speed for the same AoA and other factors. Nevertheless, the Navy folks here can tell ya about the AoA "indexer" lights.

- The Hornet has an "autothrust" feature. Only did a few approaches in the sim, but I basically used pitch for AoA , and let the motors handle the vertical velocity part of the function. Not sure how this works for the heavies, and I really didn't find the feature all that neat. I preferred to trim for the AoA and use throttle for descent. I also had the neat HUD flight path doofer to see where I would impact if I didn't change anything. Saw it first in 1971 when checking out in the SLUF, and it was a real treat.

As another contributor has stated, wings provide lift according to AoA and "q". It's the same for a 'bus as for a Cessna or an F-22. I do not advocate yet another indicator in the cockpit, but for approaches an AoA indicator could be very useful. OTOH, when near a stall or actually in a stall, the AoA indicator is of extreme value.

One of these days I can digitize my HUD video of the leading edge failure episode. The flight path marker really helped me, as the bird was yawing quite a bit, reacting funny with roll inputs ( all 1 -2 pounds of available command authority) and you can see my goal - 1,000 feet down the runway!

from the high mountains in Colorado, I comment, read, and learn from my fellow pilots flying vastly different aircraft.......

Hi,

From the Rumours and News:

BEA
http://www.pprune.org/rumours-news/4...ml#post6558788

When PF make nose up stick inputs the THS follow .. and when PF made nose down inputs the THS don't follow
Why :confused:

Hi jcjeant,

Because they didn't keep the ND input in for long enough.

They had not diagnosed their problem correctly, and attempted to arrest their ROD with NU side stick inputs.

- yes, you did. By 'omitting' the vital part "This remark is given in the mentioned FCOM 3.....when a FCTL STAB CTL FAULT is present." which others have now posted you in fact 'raised more questions than you answered'.

Your line "The FCPC gets ADR & IR information to The FCPC gets ADR & IR information to compensate for speed.." makes me again 'board the train' and ask exactly what ADR info the FCPC gets.to 'compensate for speed.'. You see what bothers me is that I don't think anyone here, and I include the software and system designers, can possibly (or do) understand the intricate processes that system failures can inject. There are simply too may variables and too little 'beta testing' time. It would be a breeze for some clever software writer to give the THS access to a IAS/angle/alt/c of g table and have it automatically adjust its datum concept. He/she might then go away thinking, 'Haven't I done well? One less stream of THS follow-up signals associated with speed change. Look - it KNOWS exactly where it should be for 1g at 230kts, 190kts, etc'

Now, once you 'inject' a speed input into the THS setting you begin to open 'maybe' doors onto the behaviour of the mid-Atlantic 340 and possibly 447 and others. I note the evident resistance in the AB community to accept that anything could be wrong but I do not admire it.

To pick up on MR Optimistic's post #968 - indeed, I did suggest that following a spate of BOEING (everyone see that?) and then the AB PGF THS triggered accident/incidents there should be some physical intervention (a 'wake-up call', if you like) required by a crew to permit THS settings beyond a certain value. This could well have saved 447.

I appears that autotrim, whether it be A/P driven in the 737 or in manual flight, has a lot of fatalities to answer for.

Hi BOAC,

Sorry - but you are beginning to confuse me now. Have you started the conversion course already?

No one would design a system like you seem to suggest with How would it know where the C of G was with a full plane load of passengers doing the Conga from the front to the back? (e.g. Last TriStar flight from Dublin)

It might be controlled by FBW - but it's still physically a conventional aircraft obeying the same aerodynamic laws as your Boeing.

- we are talking datums, sir. If it don't know that, you are 'dead in the water' as they say.

Anyway, I'd like to move this thread back to a piloting perspective if you would all be patient?

This is what I understand (*? inserted where I am not sure, ? is a normal query). I refer to the point at which the Captain is roused from his bunk and re-enters the flight deck, and my puzzle lies with the fact that for the next *?3 minutes *? the attitude and flight profile of the a/c remains effectively *?unchanged*?

Let's start with the assumption that he arrives on the f/d with a possible sensory awareness of a climb and speed reduction. He *?sees a low or non-existent airspeed indication across the panels*? He *?sees 3 pitch attitudes of 15 degrees*?. He *? sees altimeters at 350 and a VS of 10,000fpm down*? He sees *?TOGA*?. He is otherwise 'untainted' by the excursion of the a/c in the preceding minutes. Why *?does he not recognise it is stalled*?. Does he? Is he then thrown completely off track by the resumption of the stall warning as 'recovery' begins to take effect (throttles to idle etc)? If so, does the *?rapidly unwinding altimeter and VS reading*? not prompt some further attempts?

There are many puzzles in this accident, this is another. NB I hope you all notice that 'software' and 'AB' are excluded from the above.

@BOAC:
 

Don't think so because the remark has nothing to do with the FCTL STAB CTL FAULT but with elevator authority to counteract a certain THS position.

I failed here:
---
What do you need for speed calculation? These signals are fed into the FCPCs.
Input the accelerometer and rate information from ADIRU, weight and CG from FMGEC, SS input and you will have all ingredients to position the THS.

To little time?........Iron bird... 24-7?

Speed input
 

Long time ago i asked a similar question and got no definite respose, therfore let me jump in again here.

When a pilot operates the stick in an aircraft where flight control deflection is not influenced by computers, he will do it by training and habit dependent on the aerodynamic state (TAS) of the aircraft. Going fast, small inputs and small onset rates, slower speeds greater input and maybe faster onset rates. In the F4 in approach configuration and speed the stick could be jerked around without causing any flightpath change, if you did it fast enough. At high mach we needed to be very sensitive with control input not do over g or even get an accellerated stall. The artificial feel produced by a separate pitot system and some weight (bellows and bobweight) helped us with that.

That said i´m not in the clear, on what data the FBW system is doing its job in that area, changing the output to the flightcontrols in relation to different TAS. As there is no artificial feel on the stick, there must be an implemented computer logic to modulate the input to the system to get the correct amount of deflection onset and total deflection in different TAS regimes. Where does this speed value come from or is the system using a logic not depending on speed?

A33 - I cannot see any point in carrying on this direction since we seem to have a language issue and I do not speak 'anywhere'.

You said
"This remark is given in the mentioned FCOM 3.....when a FCTL STAB CTL FAULT is present."
Now you say
"Don't think so because the remark has nothing to do with the FCTL STAB CTL FAULT"??

As for "What do you need for speed calculation?" my point is I do NOT need a 'speed calculation' and nor should the THS.

rrat "No one would design a system like you seem to suggest with" - your confidence is most impressive. Does it extend to knowing that no-one would design a system to shut off the stall warning in flight whilst the a/c is still stalled?

Hi BOAC,

It doesn't need to know the C of G. We need to prove the C of G is within limits for TO & Landing and to estimate the stab trim setting for take off.

When it's airborne, the FMGC will estimate the VLS using config, fuel distribution and previously entered ZFW C of G. However the FAC will display the real VLS using measured Angle of Attack.

No - it certainly doesn't extend that far and there is no mention in FCOM either. With hindsight, I hope AB change that logic on the stall warning inhibit and include WoW, Radio Alt logic etc. instead.

With "Stall Stall" blaring at them as the Captain entered the Flight Deck at FL 350, I believe we would not be having this dialogue.

Hi,

rudderrudderrat
I'm in complete disagreement with your statement.
This is no need of long ND input fot change the THS deflection.
Any input (up or down) is followed (a response) by a movement of the THS ..up or down (in the flight law they were)
But the BEA note .. tell that the "THS remained in a full up position to the end of the event" ...

So despite nose down inputs ..

BEA again:
So the aircraft was responding to the nose down inputs orders .. but the THS not !
It's something not right there !

Hi jcjeant,

"After the autopilot disengagement:
„„the airplane climbed to 38,000 ft,
„„the stall warning was triggered and the airplane stalled,
„„the inputs made by the PF were mainly nose-up,
„„the descent lasted 3 min 30, during which the airplane remained stalled. The angle of
attack increased and remained above 35 degrees,
„„the engines were operating and always responded to crew commands."

They lowered the nose at some stage but then received the stall warning again. The report doesn't say that they continued to inject nose down inputs after that event. All it says is that they were mostly nose-up.

Do you think they were still pushing down hard at impact? The last recorded values were a pitch attitude of 16.2 degrees nose-up, a roll angle of
5.3 degrees left and a vertical speed of -10,912 ft/min.

@BOAC:
 

A330 apparently requires a speed signal.


Excuse me for not writing 'the perfectly english' which you only understand, next posts - if any - will be adressed to all but you. I can only write 'anywheres'.

Re: Asking what would the the second thing to do after looking at AoA value when hearing STALL STALL.

Nope :). So you have your AoA value, lets say it's Seven.

If that's the first thing you look at it must be key to the subsequent process that you plan to apply. So what do you do next? What is so important about the AoA number that the aircraft is telling you in your subsequent decision process. If you need to question the stall warning then why do you believe the actual AoA, it's coming from the same system....

Me, the first thing I'd look at is a horizon (an AoA indicator of sorts of course, but which also tells me whether my wings are level. Two birds with one stone....)

BOAC's attitude is interesting, a remarkable desire to blame the aircraft with zero evidence to go down that track. One wonders if this is relevant to this accident, the CVR should be key to working out the contributing factors, one wonders what else was said. Perhaps a "What's it doing now" ???

- just a million biased miles off track - avoiding CB's perhaps?

No-one ready to answer my poser with a serious response?

Hi BOAC,
Amongst the 13,630 + posers you've made, which one is the serious one?

Primary and Secondary Pitch=Control
 

In case anyone is getting the wrong impression, let me chip-in an important point to this THS discussion.

BOAC is focussed on discussing the THS as if it is used as a primary flight control. This is not the case on FBW Airbuses, just as it is not the case on an A300 or A310, or on B707 through B777. They are not like Gums's Viper, which uses the whole horizontal stabiliser (tailplane) as an elevator.

On all these jet transports, primary pitch control is provided by the elevator, as per DHC-1 Chipmunk or Cessna 150. On those aircraft, the pilot then adjusts a trim tab on the elevator itself, which provides an aerodynamic load to hold the elevator at the position the pilot wants. This position is reflected by the control stick.

On large jet transports, speeds, CG and high-lift devices are so much more variable that, on the approach, the elevator would be in a very high position. In other words, the primary control of pitch would be already near the limit of its travel. This is plainly unsatisfactory. The solution is to provide a secondary pitch control, in the form of the all-moving horizontal stabiliser, which trims the aircraft in pitch to enable the elevators to return to neutral. The control column will also return to neutral. On Airbuses, FBW or not, this is referred to as the THS.

When hand-flying an A310 or B767, the PF makes pitch commands with the control column. The elevators move. When the PF achieves the pitch effect he/she wants, he trims the THS to enable himself to relax pressure on the column. All jet transports have an autopilot (AP) which uses the same technique as the pilot. When it trims the THS, we call that auto-trim.

On a FBW Airbus, the AP works much the same, using auto-trim. When hand-flying, the PF does not need to trim the THS manually: the auto-trim does it. (Several American jets had a crude version of this 40 years ago, called control-wheel steering [CWS]). This only applies in Pitch-Normal and Pitch-Alternate laws. In Pitch-Direct law, the PF does his own THS-trimming.

AF447 left its cruise altitude in Pitch-Alternate law, and most of us think that this was retained for the rest of the flight (but lacking any high-AoA protections). The EFCS interpreted the PF's stick commands in pitch according to its C* terms of reference, applied the appropriate elevator when necessary, and then trimmed the THS to enable the elevators to return to neutral. The reason it trimmed the THS all the way to minus 13 degrees (13NU), was to avoid reaching full-travel UP on the elevators.

At any stage during that up-trimming process, or even after it, what would have happened if the PF had pushed the stick fully forward? The EFCS would have selected full down-elevator, and started trimming the THS in the nose-down-trim direction.

From the BEA Update:Do you assume the captain did not hear the warning when he entered the Flight Deck?

Hi,

Very nice !
But .. as you I read the BEA note .. and in this note it's :
The THS remained full up deflection to the end of the event
So you don't answer the question...
Why (or how) THS will stay (nothing move even 1°!!) full up to the end of the event ... when we know that nose down inputs were performed ... :confused:
How you explain this this contradiction (for me) in the BEA note ?

Hi HN39,

If he did hear it initially, shortly afterwards it stopped. I would guess that he assumed the crew had "respected" the stall warning and the aircraft was no longer stalled. It would take some time to absorb what he was witnessing and diagnose a continued stall (especially without the stall warning).

It's a pity that the stall warning sounded again after they made the correct (ND) input.

Hi jcjeant, - I can only explain the stab trim remained full NU, if the pilot inputs were mostly NU. If the full report shows they were attempting to unstall the aircraft with nose down inputs - but the stab remained full nose up - then AB have a huge re-design problem. I don't think that's the case.

- "Every picture speaks a thousand words". A little help
"It would take some time to absorb what he was witnessing and diagnose a continued stall" - how long would it take you? I'm pretty sure how long it would take me.

CS - I have flown all those systems. I know how they work (well, the 'crude' ones anyway). I have flown all-flying tails, elevators only, locked and unlockable elevators and follow-up tails.

jcjeant,

I can see why you infer that the BEA is contradicting itself, but that is not necessarily the case. As I explain in my post above. the THS reached 13 NU because the EFCS was trimming out a large amount of up-elevator. My GUESS is that the recorded 13NU represents the most that the auto-trim was capable of. Call it full-travel if you like.

Once the THS reached full-travel, the EFCS was probably having to apply more and more up-elevator to achieve what it wanted (i.e., what it thought the PF wanted). The brief nose-down inputs made by the PF may not have been sufficient to push the elevators into a down position. Unless and until that happened, the THS would remain where it was.