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AF447

Old 9th Jun 2009, 12:51
  #841 (permalink)  
 
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Swedish Steve

I have a question.

As a mere engineer, I understand the problems of high altitude flight with the proximity of stall speed and overspeed.

With the known problems of pitot icing (though I have never seen it) why don't you pilots just stop flying so high when there are storms about? Would it not be easy to mandate a descent to a lower FL where the speed range is greater so you have more time to react if something goes wrong?

Yes I know it costs money, but so do crashes.

Steve,
the answer to your question is that the preferred method of CB avoidance is lateral rather than vertical. Best of all one avoids a whole system but when this is not possible (as is frequently the case) the method is to find a route between individual cells, not penetrate any of the cells themselves. Often this is easier when higher because the gaps between the cells
are greater. Also many CBs do not reach cruise altitude. Sometimes lower altitude can involve worse weather.

My own experience is that operating at normal optimum altitudes is satisfactory provided that adequate lateral separation from CB can be achieved. Careful monitoring and readiness to intervene on speed and thrust are part of the process.

The issue of probe icing is one I have not encountered, nor I would guess, have most readers,and it would appear to be type specific to A330/340. It would also appear, judging from the reports from previous contributors, to occur in specific circumstances, notably layer cloud around the CB e.g.the anvil, even though the CB itself has been avoided.

It is of course true to say that if airspeed indications are lost, lower altitude does give a greater range of speed availability, therefore the crew's task is easier. In all cases judgements have to be made according to the circumstances.
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Old 9th Jun 2009, 13:04
  #842 (permalink)  
 
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To swedish steve:


A pilot always try to fly at OPTIMUM altitude, which is the altitude where you have the best kilometric endurance and you have a good margin to the low and high stall speed.

In Europe is always quite easy to fly at that altitude because, even if there are many planes flying around, the separation in height between planes are reduced (1000 feet between converging flights). The longitudinal and lateral separation between planes is also reduced because Air Traffic Controllers use the radar.

Across the Atlantic Ocean the longitudinal separations are very big (planes that follow the same route is 10 minutes of separation, i.e.80 nautical miles) and the vertical separation is double (2000 feet between converging flights).

So, at the start of Atlantic crossing if the pilot take the altitude which is not the optimum but nearly the maximum at that moment, is very happy because if there is bad weather in front of him, he will have more chance to overfly it (anyway the pilot, in the evaluation of the chosen flight level always have to think about ahead forecast turbulence).

If there is bad weather, the pilot has to use the weather radar, scans the sky in order to understand if he is able to overfly it or he has to change route in order to circumnavigate thunderstorm cells.

The job of the pilot is to evaluate and mainly take the decisions which are not the ideal but a compromise.

Anyway if the plane enters in a permissible cloud, pilot knows that the plane has a protection against ice built-up using airworthiness antice devices.


After this accident I know that Airbus had some troubles concerning the anticing of the pitots. If there is ice build-up in the pitot the airspeed indicated to the pilot (the speed that show the margin to the low and high stall speed) is unreliable.
See also this link
http://alphasite.airfrance.com/s01/?L=2

Anyway, there is a procedure called: flying with “UNRELIABLE SPEED INDICATION”.
In this procedure the pilot has to fly the plane with precalculated attitude showed to the PFD’s (primary flight displays through IR1, IR2, IR3 and ISIS) related to the phase of flight and applied the correct power to the engines in order to fly predetermined speed.

This emergency procedure is very difficult but I think that the Air France crew was able and well trained to follow, to manage and apply it.

This is the time to do again the question:BUT DID THE PILOTS HAVE THE ATTITUDE INDICATIONS ON PFD’s?

Answering this question will also answer the other: why the rudder could be detached? Without airspeed they didn’t have the Rudder Travel Limiter.
And without attitude indication, the flight could be so unstabilized that if not using the rudder with care the rudder could be damaged and detached
loosing, may be, the pressurization.


Now Swedish Steve, I ask you again to explain me better what you answer me using simple and comprehensive English (sorry, English is not my native language)


I ask again to other professionist people to clarify the line written in the Acars messages: did the AF447 flight also have IR’s failure?

Thanks
Stef
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Old 9th Jun 2009, 13:10
  #843 (permalink)  
MLT
 
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A couple of questions for an A330 pilot.....

1) With the autopilot disconnected, and flying in the dark, through the ITCZ, with questionable weather conditions (as described by Tim Vasquez), would the rudder be extensively used to help maintain level flight?

2) If the answers to the above is yes, with unreliable airspeed data, and the possibility that the rudder wasn't accurately limited, could it be possible that the crew in trying to control the aircraft in difficult conditions over boosted the rudder which in turn over stressed the vertical stabilizer? From an engineering perspective, I would say yes it is...

MLT

Last edited by MLT; 9th Jun 2009 at 14:22.
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Old 9th Jun 2009, 13:20
  #844 (permalink)  
 
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The pitot tube probably has a bleed hole for water egress, so icing might cause airspeed to decay somewhat gradually, even to zero. Sorry I don't have access to exact info.

GB
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Old 9th Jun 2009, 13:22
  #845 (permalink)  
 
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ACARS data

At the very start of this tragedy it was said in the press that they did not know exactly where this aircraft had ended up. Is the GPS position not part of the ACARS data packet? If not why not? Seems odd that a new aircraft with much sophisticated reporting would not continually transmit its position...
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Old 9th Jun 2009, 13:39
  #846 (permalink)  
 
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Request for background info: The A320/330 are not brand-new aircraft. Why would pitot tubes / probes start acting up "from May 2008"? Why not throughout aircraft life?
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Old 9th Jun 2009, 13:43
  #847 (permalink)  
 
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ACARS Position

ACARS message costs are paid to a service provider, so message length and frequency are kept to a minimum. There is probably one in 100,000 messages where the lat/long would have any value. They have ELT for that.

GB
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Old 9th Jun 2009, 13:55
  #848 (permalink)  
 
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Does anyone have the logical diagram(s) for the Rudder Travel Limiter Fault ?
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Old 9th Jun 2009, 13:59
  #849 (permalink)  
 
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from various Acars messages that I have seen they only report position when requested by the airlines maintenance depot.
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Old 9th Jun 2009, 14:03
  #850 (permalink)  
 
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Dutch Bru

The report mentions explicitly that some French airline companies, in particular those that fly long distance routes, have dedicated departments that communicate via ACARS on updated weather situations en route. Where those departments are then specifically tasked with providing specific updates on weather to flightcrews.
Good find, and thanks. I think that potentially solves and puts to rest the question regarding the crew sent turbulence message.
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Old 9th Jun 2009, 14:04
  #851 (permalink)  
 
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I made a comment about rudder travel limiting last night based upon the fcom for my aircraft but another poster found an alternative description of how it works in a different reference.
The trouble with comparing aircraft is that Airbus are not all the same.My airline flies a mixed bag of 320 family that have some major differences in their systems.The manufacturer are always "Improving" the aircraft so unless you know which mod standard your fbw computersare you cannot know which logic applies.I have also expereinced incidents where the computer mod standard was different to that in the fcom and it can take many months for the fcom to catch up.
Unless we know the mod state of the SECs on this aircraft we will not be certain which logic applies.
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Old 9th Jun 2009, 14:14
  #852 (permalink)  
 
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The position where the first ACARS message was sent is indicated here on the BEA website:

http://www.bea-fr.org/anglaise/actua...light.path.jpg
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Old 9th Jun 2009, 14:17
  #853 (permalink)  
 
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Does the A330 suffer from any dutch roll with the AP disconnected at altitude? If it does then I presume that the rudder would be used quite a bit.
Normally, I wouldn't comment on this type of accident until more facts are known, however...the above statement I suspect is indicitive of a present day general lack of swept-wing aircraft aerodynamic knowledge...IE: if dutch roll conditions should develop (especially, at higher altitudes), the last thing a pilot would want to do, is have pilot applied larger rudder inputs, because....this will make the dutch roll conditions much worse, not better.
A known fact, decades ago, but I now suspect...totally forgotton, or never taught.
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Old 9th Jun 2009, 14:34
  #854 (permalink)  
 
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Originally Posted by Finn47 View Post
The position where the first ACARS message was sent is indicated here on the BEA website:

http://www.bea-fr.org/anglaise/actua...light.path.jpg

That position is only based on a projected track and distance from the actual time of the INTOL position report, and the estimated time of arrival overhead TASIL.

It is probably fairly accurate but could be off by many miles if they were deviating around the thunderstorms.
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Old 9th Jun 2009, 14:34
  #855 (permalink)  
 
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@MLT

1) No.

2) No.

3) Anything is possible, but is it probable, no.

As a general note on this thread, despite having flown the A330 for 11 years and FBW Airbuses for 16 years, there are, for me, too few established facts to make for anything other than completely uninformed speculation so far. Hence, I and many of the other frequent contributors to Airbus related threads have withheld most comment.

Most of what your reading here has been generated by those who don't know the aircraft and has more to do with the pet theories of the uninformed/unaware and the usual cranks riding their favourite hobbyhorses than it does with any practical discussion of the A330's systems or operating procedures. How about, before choosing to post each of us asks whether we have sufficient knowledge of either the aircraft or the circumstances to make a meaningful contribution to the thread? If not, and if it's an idle curiosity question based on what you don't know, then don't post.

If I read another contribution that states that the pilots must have been flying too high into "coffin corner" for their weight, or that the automatics must have all "failed" at the critical moment leaving the pilots incapable of controlling the aircraft, or that the aircraft was incapable of being controlled I swear I'll chuck my cookies. There's no information to support any of these premises (unless coffin corner is now more than 50 kts wide) or most of the other theories that have been suggested. When real facts become available let's discuss them based on knowledge of the aircraft and of the conditions our colleagues faced. Till then let's give the meteor/bomb/over-controlled rudder/all automatics lost rendering aircraft impossible to control posts a rest.

ELAC
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Old 9th Jun 2009, 14:44
  #856 (permalink)  
 
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ELAC ...

I'm glad I'm not the only one that's fed up with all the speculation ranging from the almost delusional people with a vivid imagination to the armchair scientists who think they can analyse metal fatigue from a low resolution digital photograph downloaded over the internet.

Well said ! Remind me to buy you a beer sometime !


EDIT :
Just to clarify in public .... I don't know about ELAC, but I just wanted to confirm that contrary to a PM I have just received, I was not targetting anybody in particular with my post above. I was merely commenting on the general "goings on" in this thread !

Last edited by mixture; 9th Jun 2009 at 15:26.
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Old 9th Jun 2009, 14:51
  #857 (permalink)  
 
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I'm assuming there has to be a preliminary report produced - does anyone know what the time limit is on that? And is likely to contain the (official) ACARS messages?
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Old 9th Jun 2009, 14:56
  #858 (permalink)  
 
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@Stezam65

Across the Atlantic Ocean the longitudinal separations are very big (planes that follow the same route is 10 minutes of separation, i.e.80 nautical miles) and the vertical separation is double (2000 feet between converging flights).

Atlantic (MNPS) was the first zone worldwide with reduced vertical separation of 1000ft as far as I know, or I misunderstand your comment?
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Old 9th Jun 2009, 15:01
  #859 (permalink)  
 
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@overthewing

French authorities said they will have a preliminary report by the end of June.

Investigation will be carried out by French authorities, while Brazil will help with SAR, debris recovery and identification of the bodies.
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Old 9th Jun 2009, 15:07
  #860 (permalink)  
 
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ELAC,



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