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AF 447 Search to resume (part2)

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AF 447 Search to resume (part2)

Old 5th May 2011, 16:18
  #741 (permalink)  
 
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IMHO, Donít expect any quick news as a result of the recorder recoveries. They still have to be examined, and here lies a very big pit fall. So many things can cause this task to be delayed, or totally not possible. Decay, corrupted data, non exsistant data due to power disruption or failure, or some other reasonÖ..and I hesitate to mention what we all know Ė A government investigating itself. One could say, BEA owns a big stake in Air France, their boss, the French Govít, owns a big stake in Air Bus, and I wonder what the connection between the French Govt and Thales might be. Oh well, just piggy backing on earlier posts.

I hope that I am way off base. The industry deserves a true and accurate accounting of all available information. Not another CO airplane part deal. There is still a way to go. This is not over yet.
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Old 5th May 2011, 16:18
  #742 (permalink)  
 
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Originally Posted by takata
I'm 95% sure that there was no direct stall down from 35,000 fts and that she was not crashed at the end of the ACARS sequence.
I can't imagine a scenario where she wasn't doomed at the end of the ACARS sequence, even if she managed to keep airborne for some while. So the primary reasons for the disasters should be recorded, even if recording stopped at the same time as the transmission of ACARS.
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Old 5th May 2011, 16:35
  #743 (permalink)  
 
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takata
Can someone explain how an aircraft may stall during five minutes from altitude without, at some early point, its engine stalling as well?
Iīm not familiar with fan engines and their stall prevention capapilities, however a few thoughts from my side.

On ground testing there is no airflow at all to the engine except the flow caused by the suction of the engine, and it works anyway. So if the engine stayed alive in the beginning of the upset, could it then continue running (even in a kind of reduced performance) during the ongoing stall? Would it make any difference, wether the engines operated in a rather low powersetting at the beginning of the upset?

The engine iīm familiar with from the F-4, the J79 could stall pretty hard and flame out as well in high angle of attack situations near slow-speed or accelerated stall conditions. I expierienced a lot of those. However, that happened almost certainly when changing power setting under such extreme conditions and rarely when the throttles been kept alone, regardless of powersetting.
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Old 5th May 2011, 16:47
  #744 (permalink)  
 
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Engine Stall or Not?

takata & sensor_validation

Relative to your questions regarding engine stalling, an engine in a test cell or on the ground without any forward motion behaves in a normal manner as it is sucking air in through the nacelle inlet in a normal manner. However, an engine in the air at high altitude dropping in a somewhat flat plane at some point will stall due to significant inlet distortion, blocking normal airflow. I would think there is a reasonable probability that some of the descent from 35k feet would be recorded, but the total descent (near the end) may not be. There is a possibility the descent had two vertical velocities, a lesser velocity to begin with and a much higher velocity at some point nearer to the sea.

There has be little information at this point about the engines other than what the BEA stated, "The engines were operating normally." However, there is much more information available, real time transmission of engine data back to the airline and probably GE.

There has been mention of searching for the engine electronic controls, but as they are typically mounted on the side of the fan casing and given the catastrophic damage observed on the one photographed engine, it is doubtful they survived.

I have wondered what the shape of the other engine might be in that the plane apparently hit the water with one wing lower than the other according to the BEA. Have we seen the worst damaged engine or are they both the same?
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Old 5th May 2011, 16:52
  #745 (permalink)  
 
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Originally Posted by wes_wall View Post
IMHO, Donít expect any quick news as a result of the recorder recoveries. They still have to be examined, and here lies a very big pit fall. So many things can cause this task to be delayed, or totally not possible. Decay, corrupted data, non exsistant data due to power disruption or failure, or some other reasonÖ..and I hesitate to mention what we all know Ė A government investigating itself. One could say, BEA owns a big stake in Air France, their boss, the French Govít, owns a big stake in Air Bus, and I wonder what the connection between the French Govt and Thales might be. Oh well, just piggy backing on earlier posts.

I hope that I am way off base. The industry deserves a true and accurate accounting of all available information. Not another CO airplane part deal. There is still a way to go. This is not over yet.
Politics can get in the way in other ways too - Brazil refused to release info earlier in this investigation, and as someone else has already mentioned, there was a big delay in a previous investigation when the recorders had to go to the US for data extraction - a political delay in agreeing judicial custody.

So far in this crash, BEA appear to have been fairly open with what they have got - although there is plenty of disagreement with some of their analysis and conclusion Brazil were more of a problem early on - they took custody of the recovered bodies and then refused to release autopsy details (to the investigation, not just the public).

In contrast, look at recent Airbus crashes at Tripoli and Comoros - boxes recovered, data read (allegedly), reports... not released at all. Nothing. Maybe BEA is more independent than some here are giving it credit for, and Airbus can actually buy more influence in African countries than at home ??
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Old 5th May 2011, 17:21
  #746 (permalink)  
 
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CVR at least powered whether engines or not

The Airbus SD documentation states:

The CVR is automatically supplied with 115VAC when the aircraft is in one of the configurations given below:
- In flight with the engines running or stopped
- On the ground with at least one engine running
- On the ground during the first 5 minutes following energization of the aircraft electrical network
- On the ground up to five minutes after second engine shutdown
I don't have time to dig through the full electrical schematics, but power is certainly more or less directly derived from the battery via an inverter.

So, unless battery power was lost, I would expect the CVR (and by implication SSDFR - I don't have that schematic to hand...) would remain powered.
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Old 5th May 2011, 17:22
  #747 (permalink)  
 
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Originally Posted by takata
I'm 95% sure that there was no direct stall down from 35,000 fts and that she was not crashed at the end of the ACARS sequence.

Can someone explain how an aircraft may stall during five minutes from altitude without, at some early point, its engine stalling as well?
I still think that there is a very high probability that the impact occurred within a minute after the last ACARS transmission. I'm keeping an open mind as to if, when, and for how long the airplane was stalled, and what type of stall developed.

The engines don't normally stall when the airplane stalls. The engines may stall or surge when the intake is exposed to extreme angles of attack or sideslip. The airplane in cruise configuration stalls at an angle of attack that varies between 14 - 15 degrees at low altitude, and 6 - 7 degrees at high altitude. I wouldn't expect the engines to stall at angles below 30 - 35 degrees, depending somewhat on power setting. And if they stall, they don't usually flame out immediately, more likely they will surge and overtemperature.

Last edited by Jetdriver; 5th May 2011 at 21:24.
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Old 5th May 2011, 17:27
  #748 (permalink)  
 
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wouldn't the RAT have deployed with no engines (but of course would have been no use with no airflow) - the picture of it on the seabed suggests to me it was still inside its closed doors.
@ sensor_validation please tell me, at which picture did you see the RAT?
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Old 5th May 2011, 17:34
  #749 (permalink)  
 
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Originally Posted by grity View Post
@ sensor_validation please tell me, at which picture did you see the RAT?
Good question - it was the APU sorry!
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Old 5th May 2011, 17:42
  #750 (permalink)  
 
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That's interesting GY, cannot see that in my documentation which I believe to be up to date ... !?
Would you have the reference please ?
For the in flight case, would it imply the APU is running at least even if engines are not ?
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Old 5th May 2011, 18:20
  #751 (permalink)  
 
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Nothing in ACARS!

Originally Posted by sensor_validation
Takata - wouldn't the RAT have deployed with no engines (but of course would have been no use with no airflow) - the picture of it on the seabed suggests to me it was still inside its closed doors. Engines run on the ground or in testbeds without airspeed, wouldn't a modern FADEC with sensitive surge protection managing fuel flow maintain operation even where there is not enough air massflow/density to attempt re-light? And if engines not stalled at altitude why would they with increasing air density below 6000ft?

Previous posts suggest rate of fall fully stalled would be much greater than 6000ft/min, so a single event would have to have started later/higher, but could still end 2:14:30.
Thank you for your reply but the main issue I'm dealing with is that there was nothing sent, at least, about any engine stalling during the whole ACARS sequence from 02:10 to 02:14:30.

Hence, I'm quite far from being convinced that this airframe could have been for any length of time "fully stalled" (flat/ spin/ spiral/ whatever) during this particular time window without triggering a related ECAM warnings about some power plant issues due to abnormal attitude (outside her flight enveloppe, as it is the definition for an upset)

The full list of the related engine ECAM warnings is too long to be listed but there are some which are quite telling in this particular case:
. ENG THRUST LOSS
. ENG 1 (2) STALL
. ENG 1 (2) FAIL
. ENG ALL ENG FLAME OUT
Only the last one might be retained in the pipe as the ACARS would subsequently become inop due to SATNAV shutdown.

Moreover, A/THR was lost from the start, and the FADEC was also compromised by air data issues (as the ADRs are also playing their part in her runing cruise configuration). Then, any engine management after 02:10 would have been deprived of any automation able to optimise her power plants if there was a simultaneous full loss of control situation.

So, what I'm saying is that it is quite surprising that she could have dropped out of the sky at 02:14:30 while her engines were constantly monitored and given as operating inside a "normal" enveloppe up to this point.
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Old 5th May 2011, 19:15
  #752 (permalink)  
 
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Not seen any real detail about GE real time monitoring of AF447 engines, but by 2006 they received "thousands of data messages from aircraft each day" with >9000 aircraft monitored http://geaviationservicesolutions.co...006/v06i01.pdf

I would be surprised if it was much more than the AF ACARS maintenance reports, with regular 10min status plus increased reporting 'by exception' and full data uploads when in airport (but even there I am not sure WIFI would have enough bandwidth?).

Of course 100s of parameters could be recorded every second and a DVD's worth per flight BUT as per discussion about FDR streaming this is not currently feasible/economical via satellite - and surely even less so when F-GZCP was designed/certified?
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Old 5th May 2011, 20:43
  #753 (permalink)  
 
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khashoggi - A very good point and quite correct. Yes, the irregular surface of the ocean did indeed play a large part in how the airframe and its contents were damaged and to what level.
Given the relative wave frequency vs velocity of impact and aircraft parameters, it is very unlikely that there was a significant different in wave height along the surfaces of the aircraft.
Impact surface of a wave would be virtually the same given the vertical vs horizontal velocity of the airframe, thus the relative weight/surface area of the components would cause the differences...
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Old 5th May 2011, 22:07
  #754 (permalink)  
 
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Originally Posted by 3holelover
... I wonder if the press will ever stop calling them "black boxes"?
I doubt they will ever learn where the term "black box" came from. It is very old in electronics. And I bet it's even older in mechanical engineering.
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Old 5th May 2011, 22:17
  #755 (permalink)  
 
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unmanned transport, regarding the streamers they are a better solution to acts of God.

Now, in engineering there is an ongoing effort to make equipment idiot proof. As I was growing into the field I encountered what was then a common phrase, "No matter how good our idiot proofing; but, God always generates better idiots."

I propose that God will provide better disasters that would strip off the streamer.

(And, of course, this is no reason to give up trying.)
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Old 5th May 2011, 22:20
  #756 (permalink)  
 
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It's a dirty job but somebody has to do it...

Originally Posted by bearfoil
I think what one infers as ambiguity may perhaps be sarcasm. An open mind is a fertile field.
And we ALL know what is the best fertilizer, eh?
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Old 5th May 2011, 22:21
  #757 (permalink)  
 
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I recall that up until the 1960's, manufacturers of electronic enclosures provided their products in only one finish: black crinkle.

Any non-commercial prototype electronics were usually enclosed in one of these products; whence, black boxes.
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Old 5th May 2011, 22:30
  #758 (permalink)  
 
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I recall that up until the 1960's, manufacturers of electronic enclosures provided their products in only one finish: black crinkle.

Any non-commercial prototype electronics were usually enclosed in one of these products; whence, black boxes.
Yes! ...and today, 99% of the electronic boxes on a/c are still of the "black box" sort.... The only two that aren't, are the one's the bloody press continually call the "black boxes".

Sorry... that's a tangent this thread doesn't need.
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Old 5th May 2011, 22:30
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RR_NDB, to get a feel for how the shape of the debris field was created perform a simple experiment. Take a deep glass pan or casserole and fill it nearly to the top with water. Let the water sit long enough to become still.

While the water is settling wander out to your back yard or any other place you can scoop up maybe a tablespoon of dirt. When you get back into the house drop the dirt a very little bit at a time. You'll see that some of it, the finer particles, spread out very widely. Some of it, the sand, settles quickly mostly below where you dropped your sample. Given dirt you'll see roughly three bands with sand in the middle and really fine particles spread out.

This is a variant on the test for soil used when estimating water needs for growing trees or plants. In that case you take a tall jar of water, put in about a 1/2 cup of dirt, shake it vigorously, and let it settle. Heavy stuff settles first etc. It gives a fairly good, cheap, soil quality analysis.

I think this experiment will settle in your mind where most of the distribution of the wreck likely came from.
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Old 5th May 2011, 22:32
  #760 (permalink)  
 
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A first body of a victim of the Air France Rio-Paris flight was recovered Thursday from the bottom of the Atlantic, 24 hours after the start of operations. "The body, still attached to a seat of the aircraft, appears degraded, " said the General Directorate of Gendarmerie (DGGN). DNA samplings will be performed to try to identify the victim.
Wouldn't evolved gasses remain in the tissues until brought to the surface, at which point they would cause damage/destruction to any remaining structure as they are emitted. Probably best to leave the dead where they are as much as possible. Easier on everyone.
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