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How safe is (airbus) fly by wire? Airbus A330/340 and A320 family emergency AD

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How safe is (airbus) fly by wire? Airbus A330/340 and A320 family emergency AD

Old 1st Jan 2013, 22:06
  #141 (permalink)  
 
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Originally Posted by jcjeant
This discussion has taught me that Airbus had never considered (or tested) that AOA probes (a very important item for collecting data to be used by the flight computers) can be blocked and therefore could not know the impact on automatic flight
Really? I don't see anyone saying that - I think you just made it up.

Absence of evidence != Evidence of absence.
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Old 1st Jan 2013, 22:10
  #142 (permalink)  
 
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Absence of evidence != Evidence of absence.
Absence of procedure = ?
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Old 1st Jan 2013, 22:25
  #143 (permalink)  
 
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Team EVA

These guys are unsung heroes!
They had seconds to find a solution which they did.
They knew A333-343 inside-out beyond any AFM, FCOM, and FTCM.
They had amazing reflexes.
They displayed airmanship of another dimension.
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Old 2nd Jan 2013, 00:18
  #144 (permalink)  
 
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Quotes from Bengerman:

"If the pilot of an airbus FBW does nothing more than push the thrust levers to TOGA then the aircraft will accelerate into the ground."

Yes, but that's a bit like saying that if the pilot of any aircraft fails to level off at the bottom of a normal descent to 2000ft (say) the aircraft will soon crash into the ground. (Thank you for omitting your previous reference to smoking holes this time: uncharacteristically alarmist if you are an airline pilot.)

"Please DO NOT say that this cannot happen..."

I did not, but see above.

"I am relatively inexperienced at this game, still learning after 36 years at it, and I KNOW that if it can be done then it probably will/has been done!"

In which case you must be aware of least one fatal accident following a go-around, in which the pilots and/or autopilot failed to overcome the strong pitch-up tendency caused by under-slung engines at go-around thrust, resulting in a stall.

"I have time on 737, 744 and Airbus FBW along with others and have no particular axe to grind in favour of any manufacturer, there are simply certain aspects of Airbus design that I feel are fundamentally flawed, the above example being just one of them."

You do not mention any jets with tail-mounted engines. I have carefully reminded you that airliners such as the Caravelle, VC10, BAC 1-11, B727, DC9/MD80/B717, F28/F100, etcetera (not to mention numerous business-jets), have little or no thrust-related pitch-up tendency in a normal go-around. If you have never flown one of these aircraft, let me assure you that it is not a problem. Read what TyroPicard says.

You say that this issue is just one of the aspects of Airbus design that are "fundamentally flawed", so I suggest you pursue the others.
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Old 2nd Jan 2013, 08:05
  #145 (permalink)  
 
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Chris, thanks for your thoughts, I will bow out now because, like many threads here, we go around in circles with people shooting off all over the place and not actually addressing the original issue.

FYI I only have rear engined time on DC-10 and B727 from some years ago, they were not fbw and both would pitch up with application of TOGA.

Others here have chuntered on about training, procedures blah blah....yes, they are vital but it has to start with the actual piece of kit in the first place! To my mind poor design is that which exists when training has to be given to negate safety issues caused through that poor design.

You say:

You say that this issue is just one of the aspects of Airbus design that are "fundamentally flawed", so I suggest you pursue the others.
1st Jan 2013 23:25
I will not waste my time doing this because of the parochial and, almost, xenophobic nature of some of the posters here, but I will say that thrust levers that do not move is a negative step and non interconnected sidesticks with no feel are also negative steps. Both remove part of the feedback process and reduce the tools available to the pilot.

I bid you farewell.
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Old 2nd Jan 2013, 08:07
  #146 (permalink)  
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Want some real fun, boys and girls? I spent a little while in the 80's carefully teaching someone how to g/a in one of these......................



Guess how this handled?
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Old 2nd Jan 2013, 08:21
  #147 (permalink)  
 
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BOAC - my guess - beautifully! - I'm presuming a baulked landing at slow speed off a practice PFL in a wacky field somewhere presented little issue!

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Old 2nd Jan 2013, 08:27
  #148 (permalink)  
 
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Oh and...

Originally Posted by bengerman
If the pilot of an airbus FBW does nothing more than push the thrust levers to TOGA then the aircraft will accelerate into the ground
Technically, the speed will get to Vfe (flap 3/full) and then the aircraft will pitch up...

However, what bengerman says about the benefits of a conventional set up I can't disagree with!
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Old 2nd Jan 2013, 08:49
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One for all those FBW doom merchants.

What do you think would happen on a B757 if you went around from an approach, selected TOGA and then pulled back on the yolk?

I can tell you. In about 30 seconds you and 200+ other people would be dead.

So bear in mind what the FBW is trying to do. A mishandled event in any aircraft, FBW or not, has the potential to kill you.

To my mind the FBW is fine, its the training that has to change. We have to get away from the "it will look after you" type of training, and treat it with the respect it deserves.

Last edited by Jonty; 2nd Jan 2013 at 08:50.
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Old 2nd Jan 2013, 08:54
  #150 (permalink)  
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Originally Posted by cough
I'm presuming a baulked landing at slow speed off a practice PFL in a wacky field somewhere presented little issue!
- nice if the field is actually flooded.................
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Old 2nd Jan 2013, 10:23
  #151 (permalink)  
 
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I'll get my seaplane rating out...
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Old 2nd Jan 2013, 14:52
  #152 (permalink)  
 
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BOAC,
Have a feeling I may come unstuck on this one! On the face of it, reminiscent of TyroPicard's VFW 614 jet, but with the prop's slipstream improving elevator authority. Unlike the prop-driven types most of us wrinklies started our careers on, this pusher-prop will have negligible effect on wing lift, so back to the VFW 614 situation again. Is that why the thrust line looks to have an up-vector? Bottom-line is: I reckon you'd have to pull fairly hard initially. (You have control!)

Bengerman,
Sorry you feel like that, but I'm not expecting to devote much more of my retirement to this contentious argument, either. (And I much admire others who have to compose their thoughts in a foreign tongue.) Why does it have to be so polarised? Re non-driven thrust levers and non-interconnected sidesticks, if you have seen my posts on this and other threads, you will see that I have opposed them in principle since the 1980s.

I haven't flown the B727, but your comment surprises me. The DC10s I flew only had a third of their thrust mounted on the tail: the rest was under-slung. I seem to recall that, due to its high thrust-line (unlike the L-1011), a single-engine G/A using that centre engine was quite interesting.

Jonty,
Thanks for endorsing my point. The G/A accident I had in mind was either an A300-600 or an A310 in the Far East: conventional controls and (as some readers may not know) very similar configuration to the B757/767. I remember go-arounds in the A310 only too well.
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Old 2nd Jan 2013, 15:15
  #153 (permalink)  
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Yes, angled thrust-line to 'help' with normal cruise type stuff. The g/a was a 'pull' manouevre but with significantly improved elevator/tailplane response as you say. Overall, as with all a/c, you got used to it.

To digress even further from thread, I was really proud of my 'student' who subsequently had an engine failure with Mrs Stude aboard heading westwards off Islay, dumped it in the ogg and paddled safely ashore with the onboard oar.
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Old 2nd Jan 2013, 15:28
  #154 (permalink)  
 
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Chris Scott
Out of interest are you anti side-stick or just anti-the lack of interconnection? I have been thinking about the difficulties and implications of connecting them and have concluded that if you choose side-sticks for their amazing precision you can't connect them.
I never found non-moving T/L a problem - did wonders for my N1 scan!
TP
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Old 2nd Jan 2013, 15:30
  #155 (permalink)  
 
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Very interesting reading for an SLF, especially the continuing A vs B debate. Personally I do not fly "A" ever as a matter of choice. I firmly believe that the overall level of pilot skill is significantly different.

I recognize that this is not an entirely objective view point...however I do believe that the very name Airbus is telling....the end goal was to create a flying bus service....and the end result has been a drive to the lowest common denominator of pilot "skill" possible.

AF447 epitomizes the inherent issues. The current automation levels created a "qualified" flight crew entirely incapable of dealing with what should have been a relatively minor issue (which had happened dozens of times). From my perspective the entire A culture encourages an almost total dependence on automation for cadet pilots (not sure if that's the correct term).

So when you have a "pilot" who's grown up in a dedicated Airbus culture moving directly into an SO/FO role after 250 hours(?) then flown 800-1000 hours...how much actual hand flying has he done?

While I recognize that current generation planes from both A & B are safer then ever and statistically equivalent I think that those safety improvements now bring pilot skill to the forefront.

Personally the only buses I ride in don't have wings
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Old 2nd Jan 2013, 16:51
  #156 (permalink)  
 
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Chris Scott and SLF

The legacy of rancor is not substantiated by a polar view, from either camp.

Airbus sought to revolutionize the Command and Control of commercial airliners.

They succeeded, and failed. The burden of change is on the novelty, not the status quo. Aviation has historically been conservative in outlook for both good and bad.

Any counterintuitive alteration will get close scrutiny. "Fair" is for the ignorant. Any bold step will attract hostile attention. The knee jerk occurs when the discussion decides on its own to retreat into bunkers, and mortar fire.

The burden of popular acceptance is on the creator.

1. What advantage is there in unconnected control stations? The list of disadvantages is long from the detractors, and the default on the defense is "it is just training"

2. What is the advantage in partially defaulting to a melange of "novel controls" mid-emergency? Intermediate and partial reversion? Again, just "training"?

3. What was the logic and the advantage of leaving AoA display out of the cockpit? Ahh...."training"?

3. The platform is different, by design. With failure comes the responsibility to re-prove the design. This need is natural, and not led by the "enemy".

4. Why remove all sense of "input/response" from the controller? Rely instead wholly on "instruments" to meter the result? Again, with subtraction comes the duty to prove.

Claiming that there exists merely a dearth of "training" is not sufficient to defend the failures. Reality makes that a Lie...The recent loss of AoA vanes without a "trained" procedure makes the builder look sloppy, irresponsible.....

"The other platform is no safer" That is discouraging, because after all the "changes" we see no improvement?

That makes the conclusion for some of us.... "Change for Change' Sake"

If all the goal was to be "notorious" the venture was successful.



That is not enough.
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Old 2nd Jan 2013, 18:59
  #157 (permalink)  
 
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Quote from TyroPicard:
"Out of interest are you anti side-stick or just anti-the lack of interconnection? I have been thinking about the difficulties and implications of connecting them and have concluded that if you choose side-sticks for their amazing precision you can't connect them."

Very tricky question, and perceptive follow-up. You may remember I've stuck my neck out on PPRuNe before on the characteristics of sidesticks, and how some pilots abuse them (physically, not verbally).

Re the first part, I liked the sidestick from the first simulator session at Blagnac. However, certain combinations of roll and pitch commands can become less coordinated than one would like, even in Normal Law. The interface between sidestick and FBW in Roll Normal complicates the handling of the wing-down technique (after de-crab) in crosswind landings, but "bumping" the stick seems to work well. The (AF447) combination of Pitch Alternate with Roll Direct, however, would not be a comfortable one.

Re the second, the lack of interconnection makes it impossible for the PNF to monitor the stick handling of the PF in flight, doesn't it? Can be a real problem, particularly when you are "giving away" a landing in a gusty crosswind. But even in smooth weather I've watched guys from my frequent perch on the P3 seat (line checking), and over-use of the sidestick is all too common. It seems to be a form of occupational therapy for some when the adrenalin is going. Sometimes this leads to PIO, sometimes not. We know that Bernard Ziegler ruled out interconnection at a very early stage in the design process, presumably for weight and reliability, although the latter has been perfected in all other dual-control aircraft.

But now you raise the other problem with interconnection. Due to its size, relatively-small, quick, brief movements are the norm (two exceptions being rotation on take-off, and a roll from full bank one way to full bank the other). I'm no engineer, but if these movements had also to power the complimentary movement of a system of cable and pulleys (or anything else mechanical), the hand force required would be great (and the best way to use the sidestick is with finger-tips and thumb). Is that your point?

Any interconnection, therefore, might have to be via electronics: presumably using servos. The throttle levers work brilliantly in manual thrust, but the command from the transducer is one-dimensional and the signal time to the FADEC may be less critical. Could a sidestick system work in both directions, and would it be accurate enough and quick enough? Could the sticks be allowed to be in different positions, as at present, and would the algebraic sum still apply? How would the PNF assert control as PF?

That brings us to your final point:
"I never found non-moving [non-driven] T/L a problem - did wonders for my N1 scan!"

We know the throttle levers have transducers, but no servos, so could they have both? The reluctance of some fleets and individual pilots to using manual thrust is partly because of the awkwardness of the transition from auto to manual (not to be done at 100ft on the approach, as I’ve seen so often). Also, in my opinion, the pilot desire for extra thrust on the (rare) occasion that the A/THR is too slow to react to a tailwind shear is not adequately catered for by the (retrofitted) feature whereby the pilot briefly advances the levers from the CLB detent. This crude expedient could get you into a lot of trouble on the approach to a short runway like Jersey. That’s why nearly all my “manual” approaches were in manual thrust.
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Old 2nd Jan 2013, 19:06
  #158 (permalink)  
 
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SLFinAZ,
I sympathise with large parts of your post, and am impressed by your grasp of many of the issues. (Sure you haven‘t missed your vocation?)

By the early 1990s, our A320 fleet was taking cadets (yes) straight out of flying school. Even on FBW, it was clear that some had better basic handling skills and hand/eye coordination than others... When they later converted to B747 (to go long-haul, as the airline didn‘t have A330/A340) or the B757/767 (sometimes for commands!) they really had their work cut out. Trimming? What’s that? But, in most cases, they seemed to cope better than we expected.

Where I can’t agree with you is your reluctance to fly in Airbuses. Airbus pilots fly Airbuses as well and as safely as Boeing pilots fly Boeings, IMO; not that I pretend to be an expert on the current skills of either.

Lyman,
I understand your argument (I think!). But you paint a very jaundiced view of what is now a very well-proven system. I’ll leave others to provide the statistics, but the Boeing FBW fleet is still miniscule in comparison with Airbus’s, and it’s all long-haul.


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Old 2nd Jan 2013, 19:59
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Originally Posted by SLFinAZ
however I do believe that the very name Airbus is telling....the end goal was to create a flying bus service....and the end result has been a drive to the lowest common denominator of pilot "skill" possible.
Interesting theory, unfortunately the truth is somewhat more prosaic. The term was first used for a BEA (as in British European Airways) specification in the mid-60s that was designed to augment or replace the HS.121 Trident. HS's next design (from DH's old Hatfield office) was the HS.134 - unfortunately it never made it past the drawing board, but here it is (Note the "AIRBUS" spec in the bottom-right corner) :



Also note how similar it is to what eventually became the B757 - despite being a 1967 design! The full story can be found here:

British Airliners 'Nearly Get It Right' Shock!

Anyway - come the '70s it was clear that the separate European manufacturers could not individually compete with the economies of scale that the big US manufacturers could call upon, and so the UK (who later withdrew), Germany, France and Spain decided to collaborate on a project that would be capable of competing. The consortium decided to use the name "Airbus" - in all likelihood because as it happens, the word "bus" is pronounced the same and means the same thing in all the languages used by those European countries (from "Omnibus" - derived from the Latin "for all").

@Chris Scott - BZ would not have been responsible for implementation details such as whether to interconnect controls or not - that would have fallen to the aeronautical and pilot engineering teams to hash out.
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Old 2nd Jan 2013, 20:16
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Bengerman and C Scott.

The 1 or 2 people polarising this debate are non pilots who do have parochial views and I think most people would prefer if they were given minimal time and the professional pilots here continue with their interesting and informative discussions.
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