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Airbus trepidation... convince me otherwise!

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Airbus trepidation... convince me otherwise!

Old 13th Jan 2012, 21:15
  #121 (permalink)  
 
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Originally Posted by OK465
I would be interested to know exactly what RA failure mode would produce the single erroneous reading. I've read info about moisture effects but that's all...
Extracts from the Airbus Safety Magazine JAN 20011 :





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Old 13th Jan 2012, 22:24
  #122 (permalink)  
 
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Hi OK465,
I would be interested to know exactly what RA failure mode would produce the single erroneous reading.
Please see page 16 onwards.
www.blackholes.org.uk/PP/20101536_SafetyFirst-11-Toconsult.pdf

Last edited by rudderrudderrat; 13th Jan 2012 at 22:41.
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Old 14th Jan 2012, 22:49
  #123 (permalink)  
 
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OK465,
As you was looking for specific info on the 330 :





Note how the auto-trim function is inhibited ... no difference with a 737 then.
And the non operation of the auto-trim would NOT be announced on the PFD !
Something to watch in case of GA ...
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Old 15th Jan 2012, 02:03
  #124 (permalink)  
 
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@ CONF iture, re: your post #114.
I'm sorry, I can't see why you ask (me?) those questions: Is there a relation with what I wrote previously?
Or are they "just" (valid) questions re:AF447?
In the last case, I suggest we continue this on one or the other of the AF447 dedicated topics.
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Old 15th Jan 2012, 12:58
  #125 (permalink)  
 
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Originally Posted by AZR
I'm sorry, I can't see why you ask (me?) those questions: Is there a relation with what I wrote previously?
It was in the continuity of your post 101
It may not tell you to trim in more than one case ... Abnormal attitude laws was a known case, Erroneous RA height indication is a now known case, AF447 could be another one ... ?
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Old 15th Jan 2012, 16:16
  #126 (permalink)  
 
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RadAlt Distrust

Just a point for historical reference.

When I was flying off the boat in the fabulous Phantom II a long time ago, we had an SOP of requiring an operational RA for night carrier landings. This was a no-go item per SOP.

Radar altimeters of that day worked well when they worked, but had a much higher failure rate than present day ones for the same reasons listed in CONFiture's post #128. About 1/5 of my flights had an inoperative RA on post-start checks. What most of us did was go flying and gripe it on return. At least the RA was not integrated into the rest of the aircraft systems.

With that operational experience behind me, I am extremely distrustful of RA equipment and am amazed that present day system integrators have given RA equipment a position of high trust with so few possibilities for reconfiguration following an obvious failure.
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Old 15th Jan 2012, 19:05
  #127 (permalink)  
 
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CONF iture : OK, got what you meant.
Well, you mention an unproven hypothesis (i.e. : the autotrim was not functional on AF447 after the THS reached the maximum value recorded on the flight). I'll wait for someone to explain me how & why it became not functional before following you there.
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Old 15th Jan 2012, 19:11
  #128 (permalink)  

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This is getting as boring as beating a dead horse :
Between the Bfanboys who are strong on opinions but short on memory and the imbecillic mantra of " if it's not a boring i ain't going ", the discussion only breaks down to side sticks vs yokes.
A rad alt failure on approach, by converging designs will provoke very similar reactions, whether you're on a 'B or an 'A. So much that the differences will be minimal.
The much cited absence of stall warning between o and 60 knots on an 'A330, would also have happened in a 777, in very comparable Vi values.

The THY 1951 accident in Amsterdam , I thought, would have woken up Boeing drivers over the fact that their toys are not exactly perfection itself... and before anyone would say it's because they were Turks, the same situation happened on an Australian 738 in Sydney in APR (?) 2009.

Then the quasi general dishonesty of the Bfanboys about the level of automation reached on the 777, and carried over to the 787 : automatic trim, pitch protection on takeoff,single engine lateral correction (as far as I know,this goes further than the much maligned 319, 320, 321, 330, 340)... as if it was shameful to have a degree of automation comparable to the Airbus prodicts... Sheesh !

I've flown DC-4s, 737s, L-1011s, 741, 2, 3, 4s, the 320 family and the 330/340. Been on the 'Bus range for 16 years, and don't want to go back to old tech.
It will be getting even older as the new generations apparently go the 'Bus way ;: Bombardier, Sukhoi, the Chinese, Dassault... remains the Argentines in the yoke fans...
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Old 15th Jan 2012, 19:36
  #129 (permalink)  
 
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Talking

Lemurian wrote:
This is getting as boring as beating a dead horse :
Between the Bfanboys who are strong on opinions but short on memory and the imbecillic mantra of " if it's not a boring i ain't going ", the discussion only breaks down to side sticks vs yokes.
Ha ha, what a load of poppycock!
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Old 15th Jan 2012, 23:09
  #130 (permalink)  
 
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TTex600. You left out one very important part. They flew into a thunder storm too close to the coffin corner. Also, the RADAR wasn't properly set up at top of climb (which is SOP).
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Old 16th Jan 2012, 01:31
  #131 (permalink)  
 
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Originally Posted by Machinbird
With that operational experience behind me, I am extremely distrustful of RA equipment and am amazed that present day system integrators have given RA equipment a position of high trust with so few possibilities for reconfiguration following an obvious failure.
No doubt, the RAs are an important part of the System. The Airbus documentation mentions how ''they supply information to the AP and A/THR modes, plus inputs to switch flight control laws at various stages.
Although the ECAM procedure for a RA 1 + 2 FAULT is straightforward, the consequences of the failure on the aircraft operation require consideration.''

But still better to face a well identified dual RA FAULT than a nebulous erroneous RA height indication.
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Old 16th Jan 2012, 07:46
  #132 (permalink)  
 
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You can hardly blame the Amsterdam THY crash on the Aircraft.


So the RA failed and the autothrottles did not bring the power up.


Because of this the crew allowed the Aircraft to stall ?


Unbelievable, they couldn't think to push the power up themselves.


If the auto whatever doesn't work, just fly the bl**dy aeroplane.


(I know you can't do this in an AB)
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Old 16th Jan 2012, 08:14
  #133 (permalink)  
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They did push the throttles up. But because the autothrottle was in flare mode (due to the faulty RA) it simply brought them back to idle again.

At least on an Airbus if you push the the thrust leavers forward to TOGA, they stay there....
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Old 16th Jan 2012, 09:57
  #134 (permalink)  
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So they selected full thrust and it went back to idle? Scary, sounds complicated!
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Old 16th Jan 2012, 10:34
  #135 (permalink)  

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You can hardly blame the Amsterdam THY crash on the Aircraft.
No ?
Can't have it both ways : as in many instances, an RA failure will cause similar results on any aircraft, you can't blame A and exonerate B, putting the whole fault on the crew.
So the RA failed and the autothrottles did not bring the power up.
They did push the throttles up. But because the autothrottle was in flare mode (due to the faulty RA) it simply brought them back to idle again.
which gets us to one of the demands of modern equipment : " Know how it works, or else !"
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Old 16th Jan 2012, 12:43
  #136 (permalink)  
 
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Of course the failed RA in the Turkish accident was a contributing factor. If Boeing had a made a comparator between the two RA, the accident may not have happened. Or if that had had the new "Airspeed low" warning that we have now (introduced after that accident), they may have had sufficient time to correct their inattention.

Every aircraft has it's pitfalls and that is why there are pilots in the cockpit. The buttom line is that they did not watch was going on, and that at a completely unacceptable phase of flight.

However, the aircraft did not change it's characteristics. Nothing was working against them. Nothing cluttered the information at hand, one look at the airspeed indicator should have been enough to know what was going on. It's always procedure to disconnect the automatics when taking over manually, they failed to do so as well. Maybe it was lucky, since they performed an incorrect recovery procedure as well. Had the engines stayed at high thrust they may have ended up with nose 45 deg high and airspeed of 30 knots and the crash may have been a lot worse. That they pancaked it on to the ground, is probably the reason that most survived.

The problem with the Airbus is that you have an aircraft that is changing it's behavior depending on which failure you may encounter. Comparing Turkish and AirFrance is utter unfair to the AF crew, who despite acting incorrectly (justified or not, see previous post) were not negligent. They had an aircraft that adapted to- and covered up every false move they made.

All conventional and Boeing FBW aircraft always retains the same flying characteristics.
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Old 16th Jan 2012, 13:14
  #137 (permalink)  
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However, the aircraft did not change it's characteristics. Nothing was working against them.
So when the pilots pushed the throttles forward to increase the thrust and the aircraft automatically did the complete opposite and reduced the thrust to idle.

You don't consider that working against them?
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Old 16th Jan 2012, 13:27
  #138 (permalink)  
 
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You don't consider that working against them?
No. That's called passive acceptance.

If you turn your car indicators on and they self cancel prematurely when you turn the steering wheel - is that called "working against" you? What would you do? Carry straight on and miss your turn?
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Old 16th Jan 2012, 14:19
  #139 (permalink)  
 
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Boeing philosophy: Basically anytime there is severe a problem, the pilot should assume control (the pilot should also monitor airspeed, keep his hands at the controls etc.):

FCTM:
Recovery from an approach to a stall is not the same as recovery from an actual stall. An approach to a stall is a controlled flight maneuver; a stall is an out-of-control, but recoverable, condition.

Note: Anytime the airplane enters a fully developed stall, the autopilot should be disengaged and the autothrottle should be disconnected.
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Old 16th Jan 2012, 14:20
  #140 (permalink)  
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No. That's called passive acceptance.
I'm sorry, I think you must have misunderstood me somehow. Just to be 100% clear: You are trying to say that if an aircraft does the complete opposite of what you just commanded it to do and reduces thrust to idle when you require (and have commanded) full thrust, that is not 'working against you' in your book?

A more appropriate analogy would be:

You are in a car, pulling out of a T-junction. As you pull out you see a car approaching so you step fully on the accelerator pedal. But the car instead applies the brakes.

For the record, I think that the tens of millions of flight hours flown by both manufacturers have proved both Airbus and Boeing products to be remarkably safe and reliable types. I'm just a little gobsmacked at some of the double standards that the anti-bus brigade seem to display.
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