bubbers44

I have never fllown with a side stick but no Boeing pilot at FL350 would pull back to the stops if he lost his airspeed and autopilot, why would an Airbus guy do it? No monitoring pilot would let the pilot flying do it either. Is this really how Airbus pilots normally fly?

gums

@ bubbers, et al

Yep, beats the hell outta me. Hold what ya got and analyze the situation.

maybe the "boldface" or whatever the commercial folks call it was not a good idea - like pull to 5 degrees of pitch and so forth.

For others, re: elevator versus stick inputs

Good grief, we've been thru this. The position of the control surfaces on a FBW jet do not reflect the pilot inputs via sidestick, wheel or whatever. They move to achieve the commanded gee, AoA or roll rate. The rudder will move to help roll coordination, with no input from the pilot.

In the 'bus, the THS will gradually move one direction or the other to reduce the amount of control input to achieve the "commanded" gee.

Waiting for the final and the immense amount of comments from we in the peanut gallery shortly thereafter.

mm43

The BEA's English translation of the recommendations issued following their report into the Tarom incident is as follows:-As far as I can ascertain, those basic recommendations have been fulfilled, e.g.

• The A/P and A/THR disconnected when a couple of ADR's had a disagreement over speeds.
• The THS trim continued the way it was designed to, though due to a change in the control law, it would appear that the crew had no idea that the Alpha protections had been lost.
  • Except when the Abnormal Attitude Law has been triggered, auto trim is still functioning and a constant stick NU/ND command will cause the THS to follow in an attempt to maintain a load factor of +1g - be aware!
• The Stall Warning operated correctly while the aircraft was within the Normal Flight Envelope, but wasn't heeded.

In short, the visual and audio clues/warnings provided, possibly added to the cognitive overload. Would a pseudo artificial feedback to the SS helped?? Perhaps the centrifuge simulators of tomorrow may help to reinforce what it feels like when the aircraft is maneouvered in abnormal conditions.

DozyWannabe

Bubbers, that's *precisely* what the Birgenair 757 captain did.

infrequentflyer789

Not at FL350 he didn't. which maybe means bubbers wins on a technicality.

The point, however, remains that LOC accidents, and specifically mishandled stalls, are happening across range of types/mfrs/airlines.

If it was just 'buses falling out of the sky I'd be clamouring for investigation of the bus specific sidestick and fbw etc. - but that isn't what is happening.

If the effort were focused on the bus stuff only, then we could only ever fix part of the problem and risk fixing nothing if in fact the causes are elsewhere and common across types. Far better to try and identify common causes, surely ?

RR_NDB

Pariès cited 16 events similar to AF447, all of which showed poor understanding, rare implementation of unreliable airspeed procedures and stall warnings which were "perceived but mostly not believed".

DozyWannabe

Granted, but in that case the Birgenair jet never made it to cruise level. While it doesn't satisfy all of the criteria Bubbers set, it satisfies the important ones - namely doing precisely the wrong thing minus speed indications and with autopilot behaving erratically. It also puts a dent in the "other pilot would see the inappropriate control deflection and take over", because in that case the F/O did not. The Stony Point NWA B727 was at FL 248 when exactly the same thing happened.

Organfreak

Dozy:
You keep on saying that, and I keep on countering that your premise is based on false logic. One or two cases proves nothing at all. One could (I do) also speculate that, if one had a data base of, say, 100 such incidents, equally distributed between SS and yoke aircraft, it might be more appropriate to draw the conclusion that you do IF there was no difference in the associated statistics. I.E., if we're going to make guesses on this issue, I would guess that in 100 cases of LOC-to-stall, MORE pilots would notice the inappropriate input when it was a yoke. But....I have no more proof for that than you do for your opposite conclusion.

True, I can't fly, but I can think!

SeenItAll

But this guy was an Airbus pilot, and under Normal Law, isn't pulling the side stick to the stops quite permitted because Alpha Protect would limit any pitch change to prevent LOC? (Indeed, I thought such such flight protections were one of Airbus' avowed selling points.)

So what about the possibility that the PF simply did not process/comprehend that when the A/P went into Alternate Law, that Alpha Protect was no longer active -- and that he would need to use the side stick more like a Boeing yoke than an Airbus joystick? Thus, it wasn't that he was dumb, just that he had a brain freeze in not fully comprehending that his protections were gone (despite this warning being given on the ECAM).

SRMman

Just catching up on the discussions.
I found the Jean Pariès presentation very interesting. In the conclusion he recommends an "Overall paradigm shift" in design and training. Well, how about giving the crew a synthetic view of the aircraft generated from the sensors, something like the MS Flt Sim outide spot view, say 3/4 rear view. We see this kind of display on visualisations of FDR readouts. It would give the crew (when at their most 'startled') an immediate understanding of the aircraft's pitch/roll attitude relative to the horizon, and also (if it were possible to generate) their FPV in 3D.

Turbine D

Dozy,

The same thing did not happen except for the end result. There was a different reason. The NWA B727 crew forgot to turn on the pitot heaters. So when they iced over, all indications were that they were all of a sudden speeding up, therefore they reduced speed. There was nothing to tell them they were at the right speed in reality. The speeds they were seeing on the instruments were erroneous, they didn't go away and they appeared real to them sadly.

I think caution needs to be applied when comparing accidents of this type, one 3 years ago and one ~ 40 years ago.

RR_NDB

Hi,

SRMman:

Long time ago some of us raised the issue. A very serious one.

Unfortunately i am too busy to do more in this Thread:

http://www.pprune.org/tech-log/48135...anomalies.html

infrequentflyer789

Initial cause of the pitot failure was not the same but after that it's all depressingly similar.

You could write those statements about either accident.

Yes, there is a big difference in aviation between 40yrs ago and 3yrs ago but that doesn't mean history provides nothing to learn from. The problem of crews failing to recognize stall, pulling up into stalls, pulling back through stall warnings, and failing to correct the other guy doing it is not new and didn't start with fbw and sidesticks.

Organfreak

IF789 said:
You're sure right about that, but some of us are suspicious that sidesticks could make this problem harder to suss out under pressure, since the other guy can't see them.

=this has been a pre-recorded announcement=

DozyWannabe

Admittedly that's a good point taken in isolation, but as you so eloquently put it, the amount of evidence available is not sufficient to make a statistically valid conclusion. "Suspicions" based on an assumption that something stands to reason are just that - opinion and conjecture.

The fact is that whether you can see the sidestick or not (and FWIW in the sim I could get a good idea of what the guy in the opposite seat was doing with the stick based on his posture), a combination of monitoring the aircraft's response plus timely and effective communication with your colleague in the opposite seat should nullify that potential problem.

Organfreak

Good! Then I'll stop maintaining that yokes would have helped, if you'll stop saying that they wouldn't. The only thing for sure is that we don't know.

Indeed it should, but back to the real world-- that just didn't happen this time. Even if some pilots shouldn't be fools, the fact remains that some are, so "foolproof is better." If one outta 100 pilots need a situational icon showing attitude, let's just give 'em one! Hang the expense.

=I HAVE SPOKEN=

Flyinheavy

@DW

As far as I remember the Birgen Air accident was mainly caused by failure of shutting off the A/T system, which by design took thrust to idle because of the false overspeed sensed by blocked pitot. The FO very well was aware of the situation, but it seemed to be also a cultural issue that he did not take control.

So IMHO this has very little resemblance with a yoke versus SS issue.

Why do I sense some reluctance throughout all your postings to realize that humans not always react the way that engineers plan and sometimes design the human - machine interface the way that the human has to configure himself to the machine instead the other way around?

safetypee

Re Overall paradigm shift" in design and training.
Pariès expands paradigm shift elsewhere as “the change from safety through conformity, to safety through variation management”. Variation is described by Hollnagel:- http://ipac.ca/documents/The_resilie...ion%5B1%5D.pdf


"… other pilot would see the inappropriate control deflection and take over"
I doubt that there would be a fair range of data to support either view, but anecdotal evidence suggests that pilots don’t ‘see’ a control input as inappropriate, particularly where both have similar but erroneous situation awareness. Aspect of this are discussed in http://www.pprune.org/safety-crm-qa-...ervention.html.

In addition, it would be poor practice to train pilots to use an input as a measure of aircraft control, where the really important aspect is the output - what the aircraft is doing – what has the control input achieved.

DozyWannabe

Not what I read. The blocked pitot tube caused all kinds of problems for the autoflight systems. The autopilot's manouvering limits kept the aircraft from stalling while autoflight (A/P and A/T) were engaged. The automation made no change to the thrust setting - that was set by the Captain when he pulled thrust back in response to the warnings. By pulling it back the autopilot could no longer prevent stall, but regardless, the captain pulled back on the yoke repeatedly throughout the follwoing sequence.

Well now, let's break that down a little. Engineers do not design aircraft in a vacuum and expect the pilots to cope with decisions made in isolation. In any development process there is a constant dialogue going on between all interested parties.

I've said this before, but there seems to be a persistent rumour that the Airbus FBW design was the work of engineers and management alone with no pilot input - which is categorically not true.

The difference between the Airbus and Boeing FBW designs is solely down to the dialogue having different conclusions (because the pool of engineers and pool of pilots was different). As Organfreak says, there is insufficient evidence to prove that one design is any safer or more intituitve than another, so all we have to go on are our own conclusions based on the information to hand.

Remember that the yoke design grew from the requirement to have cables connected to all flight surfaces, and until the late '80s was a de facto standard that reached acceptance over time - it was not designed to be the ultimate piloting interface, nor was it ever so.

I never said it wouldn't - I said that there's a roughly equal probability that a connected yoke or stick would have helped versus the probability that it wouldn't. I've only ever taken exception to posts which state that it categorically would have made a difference when the evidence is not there.

HazelNuts39

A german translation of the accident report is available here.