Organfreak. From the comments PNF makes during run up to STALL, he is basing his chatter on the a/c attitude from displays only, not any suss of PFSS.

Does a concerned PNF want to see a SS display to confirm/mate input with response? Boy Howdy. If it had been available, he'd be on it white/rice, you betcha. Maybe this fella allergic to mayonnaise?

As an instructor initially and long time flying multicrew aircrafts, fully visible yokes have always tell a lot of the story, and so in silence – In relation to the aircraft behavior, timing amplitude duration and speed of displacement of the flight control command tell so much to a PNF.

Airbus thinks otherwise, therefore such direct information has gone, evaporated.
Just get used to it … Put everything on the aircraft behavior, whatever the reasons are, both internal and external.

As Lyman put it, there is tremendous confusion on AF447 about the commands, attitudes, steps that should or not be applied.
Direct visual information from yokes would have relieved big part of the questioning.

That is all of an acknowledgement for someone who just wrote the ongoing Yoke v SS argument is IHHO not relevant to the loss of AF447.

Touché.;)

A330s have SS, and I doubt very much that Airbus will be looking at adopting "old" technology. More likely they make the pertinent changes to satisfy BEA recommendations - to be revealed in due course.

Situational awareness
 

Are those few bits and pieces really enough indicators, that PNF was aware of the situation and would have been able to act in a correct way from the onset (AP ATHR disconect) of the event?

I don´t think so. PNF was out of the loop from beginning and equally surprised like PF by what exactly was happening and was way behind the events. He grasped some bits and pieces further on into the event, but again without grasping the whole picture.

That´s also the reason why he did not take over control, why he did not give clear and precise commands, why he could not get the attention of the PF, why he was not able to brief the captain in a clear and professional mannor. Poor captain got nothing out of this crew, when he returned to the flight deck.

Wouldn´t that had been some kind of appropriate information from someone who knew what´s happening?

PNF recognised early that something went wrong, but he couldn´t get to the point what exactly was going wrong, why it was going wrong and what to do about it to save the situation.

You think otherwise?
Than sit down in that left hand seat, get yourself into the loop of this flight and then write down how you would have handeled the situation from the beginning and compare it to what we know until now (the HF group may shed aditional information in the final report) what PNF really accomplished.........close to nothing.

And then the question stays, why two pilots missed that bad.

@RetiredF4
 

position relative feed back side sticks
 

Hi DozyWannabe,
The Airbus side stick system lacks the "position of the control surface feed back loop" to the pilot. We have no easy way to sense how much control surface deflection is required to satisfy our side stick input. It is very useful for an experienced crew to know.

Imagine replacing the steering wheel of your car with a side stick.
http://www.auto-ui.org/09/docs/p19-kienle.pdf
On page 21 it shows the results of various side stick control feed back loops. The only negative results are from the "spring centred force reflective" side stick (similar to Airbus s.s.). It's also interesting to note the perceived difference between experienced and non experienced drivers. (your observation in post #396)

Pilots really need to be alerted when their control surface is being deflected by an "unusually" large amount. During asymmetric flying, the deployed roll spoilers on the lower ECAM page attract one’s attention. With the aircraft in trim properly, they remain stowed. Since there is no "position relative side stick" on the Airbus (nor feed back for the side stick demand from the other pilot), we really need something similar to warn us that the elevator (or stab trim) is outside its normal range.

This may be the salient determination of several "knocks" on the SS/aware loop.

If one does not know the position of a deflected control surface, and by extension the "actual" position of the SS, well.... "You climb", "I am climbing?"
"Climb, then..." "No, don't climb...." "Well, then, go down...." "He is climbing...:


"Someone should, we are at 4000 feet....." "Tire, Tire, Tire..." (Pull. Pull, PULL)

If PF, at his initial aft stick, then assumes his input is zeroed, he will think, "fine, oops, I need an aft stick..." Each time assuming his input is an isolated one, instead of "additive" (accumulative)..... This is affirmed due the inexplicable travel of the THS full up....

"The Airbus side stick system lacks the "position of the control surface feed back loop" to the pilot. We have no easy method to see how much control surface deflection is required to satisfy our side stick input. It is very useful for an experienced crew to know."

Dozy
So if a suicidal PF is sitting in the left hand seat in a 'bus it is even easier to be successful - just press override? :rolleyes:

I think that the point that has been made several times is that had the captain of 447 re-entered a cockpit equipped with yokes, he would have seen the PF with the yoke pulled into his lap, TOGA power and the altimeter unwinding at a high rate. Without anyone speaking and without any alarms it would have been immediately apparent that the aircraft was sitting in a stall the wrong side of the drag curve.

True it should not have got to that point - but it did; and the PNF and captain seemed totally unaware of the mayonnaise being stirred by the PF so had no reason to press override.

For all the knowledgeable military guys, a question to help guide my opinion on side-sticks versus yokes. In duel seat trainers for aircraft such as the F-16 or F-18, does the training pilot's stick have a connection with the trainee's stick? In other words, does the training pilot know exactly what the trainee is doing with the stick or is he forced to rely only on the reactions of the plane? Be interesting to know what the military thinks on what information two-pilot airplanes need to convey without a visual reference.

What about UAS events ?
 

I was searching some old data in my computer... and I have seen ...


La base de donnees WebDAS presente les informations relatives aux enquetes conduites par le BEA a la suite des accidents et incidents d'aviation civile.

Dans cette base de donnees :
Il n'y a pas incident AF mai/juin 2008 - sondes Pitot

Il n'y a pas incident AF juillet 2008 - sondes Pitot

Il n'y a pas les 3 incidents aout 2008 - sondes Pitot

Il n'y a pas les 2incidents ACA de septembre 2008 - sondes Pitot
Il n'y a pas incident AF septembre 2008 - sondes Pitot

Il n'y a pas incident AF octobre 2008 - sondes Pitot


Undoutedly, my computer seems to have lost memory

Dozy

The evidence is yelling at you.....No one sussed the PF Stick movements....If they had,,,, etc,.etc,,,,,,

There is another even more troubling possibility....Let's say that the SS performance is "as designed", no problemo.....The Sticks were visible, the actions noted, and.....

There was no response to Recovery solutions? This is the most obvious, had the sticks been merely "one design of two, and I don't have a preference, one way or t'other....",

Something broke, something was wack, and three pilots despite their best efforts, could not recover from STALL, LOC, and jet upset. I need to suggest again that something is missing, inadvertent, or deliberate, from the data.

And the a/c was unrecoverable, as equipped.....

Agree.
And,
What about a software change also, to prevent the aircraft to continue trimming up, below VStall?

"UNMASKING" EVENT
 

I presume these "unmasking events" have something common with unobservability of effective aircraft ? ;)

Good God, you guys are still working this one? :ugh: I'd have thought you would have finished up the report and sent it on to the accident investigation chaps by now. :D Time to move on to more recent events. :zzz:

@ rudderrudderrat,

A graphic of the Airbus SS arrangement was posted by A33Zab in AF447 Thread No.5.

With the addition of Synchro motors on each axis and interconnected to the opposite SS, the movement of each stick would then follow the other. Dual inputs would result in the appropriate feedback. However, realistic control surface feedback would be more complex, but if the FBW existing control surfaces positional feedback had inertial data added to it, a control transformer could be inserted into the Synchro couplings and a more realistic "feel" would be available to the sidesticks.

That's a simplistic example, and sophistication would improve it.

The disadvantage is as usual - extra complexity and weight.

What if the captain returned to the flight deck and observed a yoke held full forward?...

And generating, at best, an agonizing 2 degrees per second of nose down pitch rate?

Or a hands off neutral yoke generating absolutely no nose down pitch rate?

better than full up and hopefully full nose down. They didn't do that so a lot of people died. It shouldn't have happened.

B44:

when you update your experience with true FBW time, not just spoilers, get back to me. :)

spoilers, fbw?????

757.........

757 was my final airplane, I still do not get the question.

scary.......

bye maybe someone knows what you mean

The yoke/sidestick debate is another of those irrelevancies which crops up from time to time. The sheer number of Aibii whizzing around safely using sidesticks proves this. The question as to whether the use of a yoke would have helped is rather moot. Given the captain's possible befuddled state on entering the cockpit he could have possibly overlooked the yoke being pulled back or misinterpreted the angle so discounting the evidence. The only reliable indicator would have been the instruments (minus airspeed). We do seem to have some indication that the PF's scan had broken down and that the PNF was deriving some information from his instruments but not acting on it. A responsible captain would first of all look at the instruments not the position of a yoke - to do so would be otherwise unprofessional. The instruments would give an accurate indication of the state of the aircraft. As Dozy sensibly put it neither method of input is perfect and both have their disadvantages but the substitution of a yoke in this situation would have made no difference. A different more active PNF would have made a difference but once again human factors are the most important here.

Or he could have possibly realized how the picture was wrong with a yoke in the stomach at FL350.

If I had to enter that flight deck at that time, the first obvious clue would have been that full back yoke at 350 ... now call me unprofessional.

Just learned something on another thread:
At first sight, this would seem to be preferable to the BUSS in an UAS situation. What are the disadvantages?

control surface deflection
 

Hi HazelNuts39,
We have that system already. With blocked pitots and your IAS shows say 60 kts, then the superimposed stall speed is uselessly displayed off scale.

control surface deflection:
The crew of A380 VH-OQA were concerned about their roll controllability with a big fuel imbalance. At a lecture I attended, the Captain mentioned that there was no feed back through the side stick as to how much aileron was being applied. They therefore frequently looked at their flight controls system page to see how close to aileron saturation they were getting. (only inboard ailerons were working)

see pages 6-7 of http://www.atsb.gov.au/media/2888854...y%20report.pdf

"Prior to leaving the holding pattern, the crew discussed the controllability of the aircraft and conducted a number of manual handling checks at the holding speed. The crew decided that the aircraft remained controllable...As the crew started to reconfigure the aircraft for the approach by lowering flaps, they conducted further controllability checks at the approach speed and decided that the aircraft remained controllable..."

On Airbus, because the control surfaces are being moved "invisibly" (except on a systems page which may not be displayed) when the ailerons or elevator reach say half deflection, then I think there should be some alert. When the stab trim runs outside its normal range - then there should be a warning.

SS feedback / interconnection.
 

Not as much weight and complexity as this:

787 Controls
http://i474.photobucket.com/albums/r...99/787Yoke.jpg



Maybe IF SS feedback/interconnection was available it would not have happened.

But

IF ADR2 hadn't have been the voted median.....
IF they hadn't switch over to ADR3 (display on RH PFD)...
IF captain had returned to cockpit earlier (or never left)....
IF PF didn't overreact......
IF multiple UAS had lasted longer than 10s in the first fase....
IF they had realized what was going on....
IF training,knowledge, CRM, communication, SOPs would have been sufficient.....
IF AoA indicator was fitted (or BUSS was opted)....
IF inertials had been outside the abnormal attitude values.....

The outcome could have been different too!

Maybe the clues are in the modifications which have been adopted after this tragedy.

For systems:
- Inhibition of AP/FD reconnect after UAS.
- More rigid USE MAN PITCH TRIM PFD msg when autotrim is not available.
- F/CTL ALT LAW (PROT LOST) msg accompanied with reason what caused the transition.

IMO the installation of an AoA indicator will be mandated - in the final report - because it is already optional and provisions are available.

The uncertainty is the issue but on balance the postion of the yoke will not make any difference to an appraisal of a situation. A337ab summed the situation up perfectly. A yoke will not help in this kind of environment.

I don't understand that it would do that. Are you sure? Please explain.

Hi HazelNuts39,

Please see John T's explanation http://www.pprune.org/tech-log/48445...areness-2.html.
If the stall speed is calculated as being X kts and superimposed on the speed display accordingly, but due to iced over pitots at 250kts, your IAS only shows 60 kts, then your stall speed will be off the scale at X kts. All you'll know is that you think you are below the stall speed on the IAS read out - even though you may still be at 250kts. The BUSS system (when displayed) is independent of pitots.

As far as I know, BUSS is only displayed after all 3 ADRs are turned off manually.

Hi A33Zab.

Thanks for diagram of 787 yoke system. It's definitely a lot more complicated, heavy and costly than the Airbus side sticks - but at least the control surface displacement feed back loop to both pilots is complete.

Let's assume that X = 200 kts, i.e. 80% of 250. When IAS then drops to 60 kts, my understanding is the stall speed will be indicated as 48 kts (80% of 60 kts). Am I wrong?

Hi HazelNuts39,

I think you are probably correct.
I hadn't thought through the logic of the dynamic stall margin being presented as a %age of what's displayed.

@RRR:
 

As I recently understand from the 757/767, despite the 'interconnected' yokes, the possibily of splitted RH/LH Elevator surface control doesn't seem to be a good idea either.

May hope that the 787 FBW protects from such a situation.
How would it determine which input to follow?

Hi A33Zab,
I don't know if you are referring to some incident (link?) which I don't know about.
On the TriStar we could split the Capts & FO's load paths to the L & R elevators and L & R ailerons respectively, so it was technically possible to fly each side independently. They were only split if we had a control jam on one side. PFM.
In that case, you'd have to do as Airbus now do - only one pilot at a time flies the plane.

EgyptAir 990 possibly. Full forward in the RHS and full back in the LHS led to split elevators - I think Boeing changed the design after that.

Strictly speaking I think all airliner ops are only supposed to have one pilot at a time flying the plane, are they not? You can usually spot documentaries and programmes that have done their homework versus those who haven't because the latter will have both pilots with hands on the yoke in cruise even when nothing is untoward.

I know you and others perceive the feedback loop as essential, but I'm not sure it is as essential as you believe it is when an airliner's flight surfaces are fully-hydraulic. A lot of people give Airbus a hard time on the KISS principle, but in the case of the control setup, theirs is a lot simpler than the yoke systems of other manufacturers. From an engineering standpoint there's a lot more points of failure in a backdriven feedback system than the spring-driven feel of the Airbus sidestick design.

Not to mention some of the disadvantages of the yoke system that have already been mentioned (e.g. dual input becoming a strength contest between pilots, lack of positive override).

The short version is that for every "might have made things better", there's a "might have made things worse" - *if* you're looking at things dispassionately, and all other things being equal.

Is tactile feedback necessary or is the yoke a crutch? I feel sure I've said this before, but notwithstanding the brilliant job they did saving as many people as thay managed to, the Captain and F/O of UA232 kept forcing their yokes forward and left even when it was having no actual effect on the flight surfaces. I suspect the answer is somewhere inbetween.

Just to point out a few indisputable facts:

• Northwest Airlines Flight 6231 (B727) - PNF had yoke in his lap during stall, did nothing.
• Birgenair Flight 301 (757) - PNF had yoke in his lap during stall, did nothing.
• Air Florida Flight 90 (737) - PNF had yoke in his lap during stall, did nothing.

Hi DozyWannabe,
It doesn't matter that the flight surfaces are powered, it's more about being kept in the loop. e.g.
I can see the total fuel on board constantly, but the individual fuel tank gauges out of view, (they are on a systems page) so I get a warning when one tank is low, or an imbalance is building.

With the flight controls, I don't get any warning that I'm approaching maximum deflection with aileron or elevator, (or that the stab trim has run beyond it's normal range automatically). If I don't get that feed back through the side stick - then it would be nice to receive a warning somehow.

If AF 447 had some such warning, then I bet the Capt. would have been better able to diagnose their problem.

Understood. All that is fairly easily implemented without having to mess with the fundamental systems design and without having to add much complexity in software terms.

Of course in Alternate and Direct Laws, you know that full lateral stick deflection = full aileron deflection. In stall conditions, ailerons are more-or-less useless. What puzzles me is that the Captain tells them to use the "rudder bar" towards the end, but neither explains why nor does he explicitly state he suspects a stall - this leaves a lot of open questions. All that aside, I still don't understand how he could have seen an aircraft out of positive control with a rapidly unwinding altimeter - information that was clearly available to him - and not said "We're stalled". You shouldn't need to confirm yoke or sidestick position to be able to work that out if you understand aircraft.

Over the last few pages, those that consider yokes and feedback to be a panacea regardless of the circumstances are trying to hammer the known facts about this accident to fit a position they've already taken for reasons of their own, and yet they ignore incidents where an aircraft has stalled, the yoke has been back and the PNF did nothing, or (as in the case of the LH A320) they take the assumption that in a pressure situation a PF will automatically relinquish the controls as soon as a superior PNF touches them as hard fact, when there are plenty of incidents where that has not been the case.

Logically your argument also supports removing all aural warnings as there are numerous examples of flight crew disregarding them.

Where your argument is weak is that it misses all the potential incidents that became non-incidents because of the extra information provided.

@RRR:
 

EgyptAir 990 is indeed I did refer to.

I know it was initiated by FO but still the captain was unable to recover the situation.

Maybe summation (Airbii) isn't too bad at all.


All suggestions to improve safety/recovery should be considered.
but since this is a one time occurance NOT all the suggestions needs to be implemented, first of all they need to be effective.

The A330 is late 80 technology, CRT displays at that time were limited in performance and in symbology displayed at the same time.
Large LCDs in A380(and will A350) / 787 are capable to display a lot more information at the same time e.g. flight controls position.

For the AF447 the F/CTL SD page was automatically called and in view when F/CTL RUD TRV LIM FAULT ECAM was triggered.
In the BEA reports they do not mention any CLEAR action or SD page switching. (if recorded), the F/CTL page could still have been in view all the time.