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Airbus trepidation... convince me otherwise!

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Airbus trepidation... convince me otherwise!

Old 11th Jan 2012, 16:47
  #81 (permalink)  
 
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Except that Airbus has been and is a big pusher for more automation and expects its crews to rely on it.
Even TCAS maneuvers to be soon flown under full auto ...

Did you notice how the guy is talking about disconnecting auto thrust : click click - Airbus has made it different, it used to be really simple but now you need to think to do it the correct way.
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Old 11th Jan 2012, 18:34
  #82 (permalink)  
 
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where did I hear that before

video @ 21:50,

Commenting on the 757-767-A300 piloting community,
"What's it doing now?"
Specially for those that think this issue only came up first with the advent of FBW in the A320.

Nice video BTW, good advice for all pilots no matter what type they fly.
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Old 11th Jan 2012, 18:44
  #83 (permalink)  
 
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I don't know the design parameters of the latest Airbus's but the 310 had a vicious go around compared to the Boeing. The Boeing will maintain 2000 fpm while the AB goes to full thrust. If the airplane is light the attitude is way high in the Bus and it is necessary to cancel the auto thrust if you want to make it more reasonable (for passenger comfort perhaps).
China Air lost a 310 when the pilot, while doing a go around on auto pilot, pulled back the thrust levers to reduce the rate of climb and climb attitude, which led to a stall. He was slow to turn off the auto pilot and recover and the airplane only just managed to make level flight at less than 100 feet agl. Unfortunately, there was a 150 foot building in front of them. Sad. The pilot was one of their best, too, and he had his wife and kids as passengers.
Other than that, the 310 is a great airplane, pre fbw.
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Old 11th Jan 2012, 21:32
  #84 (permalink)  
 
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Auto thrust would control your speed at the pitch attitude you selected and naturally if the pitch was too great the speed would reduce until flight control laws would kick in.
In my opinion a crazy and dangerous idea to have an aircraft that is not speed stabile.
This is not an Airbus vs. Boeing thing. This is Airbus against anything that has otherwise ever been build. This FBW itself it not a problem, it's the way that they implemented it.

With a conventional aircraft that is in trim, the nose would pitch down to keep the trimmed speed (unless active back pressure on the controls). That the speed just decays until protections (hopefully) kicks in seems like a recipe for disaster.

Like with AF447, the F/O held the stick back the aircraft actually trimmed itself to fly 60 knots or the stop of the stabilizer, because the protections didn't kick in. A back pressure which in itself would have felt highly unnatural in a conventional aircraft, since a significantly pressure would be required (here only the force of a tiny spring or whatever keeps the stick centered when no force is applied).

In a conventional aircraft no one would ever have held full up elevator, simply because it would have felt unnatural and uncomfortable requiring quite a bit of muscular power. Secondly the stabilizer would not have moved and third the aircraft might have recovered on it's own as soon as someone had let go of the controls.

Makes you wonder how it ever got certified!
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Old 11th Jan 2012, 21:51
  #85 (permalink)  
 
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Did you notice how the guy is talking about disconnecting auto thrust : click click - Airbus has made it different, it used to be really simple but now you need to think to do it the correct way.
I did indeed notice that. However back then when I flew the A320 I never felt this was much of a problem; sure, you need to adjust the thrust levers with the 'donuts' prior to disengaging autothrust - otherwise you'd be in for a nice increase to climb thrust - but I never thought of it as another step I would to really have 'think' about. I just did it.

On the other hand I have to admit that I can imagine pilots not having flown Airbus before having some difficulties adjusting to that.

DBate
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Old 12th Jan 2012, 00:44
  #86 (permalink)  
 
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Another one is that TCAS procedure where not one but both FDs need to be switched OFF in order for the autothrust to turn to SPEED mode.
From a straightforward procedure as described in the video : click click - click click it is now click click on the AP only + both FDs OFF + FMA confirmation you really get what you're looking for.

I just question if things are that better ...
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Old 12th Jan 2012, 03:35
  #87 (permalink)  
 
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Except that Airbus has been and is a big pusher for more automation and expects its crews to rely on it.
Even TCAS maneuvers to be soon flown under full auto ...
Where did this come from ? I thought it mandates AP off, both FDs off, then follow TCAS aural commands (at least in the A320 anyway).
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Old 12th Jan 2012, 03:37
  #88 (permalink)  
 
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Its from the A380 and can be retrofitted to other types via a FWC upgrade... This is old news... Was in the Airbus pubs back in 08/09.
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Old 12th Jan 2012, 03:39
  #89 (permalink)  
 
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PT6A, thanks. Now I can just sit back and watch planes fly by ...
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Old 12th Jan 2012, 04:20
  #90 (permalink)  
 
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I know! Pretty neat.... Weird to watch it in the sim the first time
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Old 12th Jan 2012, 05:15
  #91 (permalink)  
 
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That the speed just decays until protections (hopefully) kicks in seems like a recipe for disaster.
Protections don't hopefully kick in on the bus, they do if you're in normal law and they don't otherwise.
That said, in alternate law (what AF447 had) the aircraft will start shouting STALL when you get to vs1g, and the auto trim ceases to function which essentially gives you a speed stable aircraft again.

But I guess it's more fun to bash the "scarebus" than to try and understand it's logic.
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Old 12th Jan 2012, 05:35
  #92 (permalink)  
 
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Cool

Hi,

That said, in alternate law (what AF447 had) the aircraft will start shouting STALL when you get to vs1g, and the auto trim ceases to function which essentially gives you a speed stable aircraft again.
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Old 12th Jan 2012, 05:42
  #93 (permalink)  
 
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But I guess it's more fun to bash the "scarebus" than to try and understand it's logic.
Suggest you understand it. "Houston, we have a problem!"
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Old 12th Jan 2012, 06:24
  #94 (permalink)  
 
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But I guess it's more fun to bash the "scarebus" than to try and understand it's logic.
That's the problem, isn't it - when shit hits the fan over the Atlantic you have to think instead of instinctively react. Apparently even experienced Airbus pilots have problems understanding the "logic" (misnomer?).

The pilot has to adapt to the engineers idea of a good aircraft, instead of a design that is build around what is natural from a pilots point of view. This is a prime example of poor engineering!


I am not saying that it can't be flow like a normal aircraft or that it is not pleasant to fly (can't speak intelligently about either since I never flew it), I am just saying that when things go wrong, it's a bad concept - like numerous accident have proven, most lately AF447 and the Perpignan test flight (incidentally both due to sensor failures and stabilizer trimmed to full pitch up without pilot knowledge as contributing factor). Then there are all the close calls, like zoom climb and subsequent stall due to a simple overspeed, aileron deflection that reduces after touchdown in x-wind without pilot knowledge, aircraft dropping several thousands of feet because a box goes belly up... and what have we not.

Try to convince me once again that we should just "understand it's logic".



All that said I sadly prefer to fly Airbus when flying as a passenger, considering the deteriorating skills of pilots, I have more confidence in the computer not breaking down, then someone up front having to deal with an engine failure while hand flying.
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Old 12th Jan 2012, 06:50
  #95 (permalink)  
 
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That's the problem, isn't it - when shit hits the fan over the Atlantic you have to think instead of instinctively react. Apparently even experienced Airbus pilots have problems understanding the "logic" (misnomer?).
Pulling up is the instinctive reaction to counter a stall? I didn't think so either.

I don't know why the crew reacted the way they did, I can only speculate that in addition to severe disorientation it had to do with the way they were trained, probably to be "children of magenta" a problem which is common to all modern aircraft these days...
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Old 12th Jan 2012, 11:07
  #96 (permalink)  
 
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Cool A320 v 777

I have limited experience on Boeing and Airbus (B737-200,300,400, 747-100,200, B777 - A391,320,321 - 22 years in all) and test flew the airbus for a short time some years ago, and would just like to put your mind at rest.

1. The sidestick and flight control system on the bus can take ages to get used to - sometimes as much as 7 or 8 seconds.

2. You never need to manually take control of pitch trim, as the stick is basically an attitude selector - so forget about trim (excepting when in degraded modes without it, when it will tell you to trim, and this is then easy).

3. If you want something to worry about, worry about the manuals - they are a pain when learning the type, and the new acronyms take some getting used to.

4. If you want something else to worry about, worry about ECAM which also takes some getting used to.

That said, it is the most fantastic, comfortable, enjoyable, able aircraft it has ever been my pleasure to fly, and for the last 6 years on the 777 I've been missing an FMA that works properly, a FMC that can do a descent properly, and a flight deck that isn't cack-brown!
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Old 12th Jan 2012, 14:20
  #97 (permalink)  
 
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Logic?

But I guess it's more fun to bash the "scarebus" than to try and understand it's logic.
If one must work at understanding the logic, maybe there is a problem with the logic.
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Old 12th Jan 2012, 14:22
  #98 (permalink)  
 
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Originally Posted by babotika
Protections don't hopefully kick in on the bus, they do if you're in normal law and they don't otherwise
Except for QF72

That said, in alternate law (what AF447 had) the aircraft will start shouting STALL when you get to vs1g, and the auto trim ceases to function which essentially gives you a speed stable aircraft again
Except for AF447

Originally Posted by Chunky Monkey
You never need to manually take control of pitch trim, as the stick is basically an attitude selector - so forget about trim (excepting when in degraded modes without it, when it will tell you to trim, and this is then easy)
Except for AF447 it did not.

Originally Posted by babotika
But I guess it's more fun to bash the "scarebus" than to try and understand it's logic
No bashing, no scarebus either, just discussing facts.
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Old 12th Jan 2012, 14:49
  #99 (permalink)  
 
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babotika, I have to agree with CONF iture on his second point: It dit not in AF447, and in fact it's not a bug, it was "as designed" that the autotrim (up) was not inhibited at or below vs1g.

CONF iture, re: your 3rd point:
"Except for AF447 it did not."
Wrong exemple, indeed it did not for AF447, because it was not in the proposition:
"excepting when in degraded modes without it, when it will tell you to trim, and this is then easy"
It may not tell you to trim in one case: Abnormal attitude law.

(btw: I do feel that some parts (inhibition at vs1g, telling the crew in abnormal attitude law) of the trim logic may/should be enhanced on A ; but let's keep facts straight, shouldn't we?)
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Old 12th Jan 2012, 15:09
  #100 (permalink)  
 
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Pulling up is the instinctive reaction to counter a stall? I didn't think so either.
My theory:
(and yes it should be obvious by now that I don't like that Airbus philosophy, but at least I believe I have it backed up with arguments as to why)

I would say that in general, it is very natural to pull back when you are going down. You have to remember that not once in the CVR do they discuss the possibility that they are in fact stalled, despite the oral warnings. Hence, it would be quite reasonable to conclude that they were not aware that they had stalled.

With the first problem being unreliable airspeed, it may have caused them to subconsciously dismiss the warning. Further another Airbus "feature" may have enforced their belief that they in fact where not in a stall. As they pulled back and the speed dropped below 60 kts the stall warning seized.
Question: How can you design a stall warning that stops when the airspeed get extremely critical? How can the "logic" dismiss a speed of less that 60 kts as being "invalid" when the air/ground sensor is in flight?
Rhetorical: Oh yes, I forgot, it's not necessary since it's obviously impossible to stall an Airbus!! (my bad, since: "we must try and understand it's logic").

With no tactile feedback from the stick (which would have presented itself as unusually high back pressure in a conventional aircraft, like mentioned in previous post), the only indication that something was terribly wrong would have been the high pitch presented on the PFD.

Another question: Correct me if I am wrong, but is the normal GPWS maneuver for an Airbus full back pressure and full thrust? Oh, they were in another mode where that doesn't apply, you say? ("we must try and understand it's logic").

Conclusion:
With the assumption that the aircraft is flying it is perfectly natural instinctive reaction to pull back to arrest a descend.


Of course It's unfortunate, to say at least, that they didn't recognize the high pitch, but with turbulence, bell and whistles and an aircraft providing no feedback what-so-ever I won't be the judge of that. From reading the transcript it seems like they got really confused and overloaded, and they certainly didn't get any help from the aircraft.

Surely, the situation could have been handled better with pitch and power, but with daily ops with "path stability" and other concept that goes against the laws of nature, is pitch and power even a concept in the Airbus "logic"?

Lack of training... Yes, an inherent Airbus problem, since you can't make up the daily training on the line with simulator sessions twice a year. The problem with the Airbus in my opinion is, that you can't train flying it in alternate or direct law. With a conventional aircraft you can train "direct law" raw data daily, and this is the worst situation the automatics will drop you into. With Airbus on the other hand, when you have a problem on a dark stormy night, the aircraft itself drops another problem on you lap - that you get an aircraft that you are not used to handle and never will be properly trained to handle!
Of course this could be solved by mandating that all Airbus pilots get a simulator session pr. week, where they can practice flying in the lowest level of automation! (they would still get less practice then an eager pilot on a conventional aircraft).

To say that AirFrance managed to pair up the 3 worst pilots in their fleet and their incompetence was the cause of the crash is simply too easy a solution. Im am not buying it, and I feel sorry not only for those onboard but also for those the pilots left behind, who now have to live with the public pressure that their loved ones, who may have been dutiful and decent pilots, killed a lot of people.
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