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AF 447 Search to resume

Old 15th May 2010, 22:33
  #1061 (permalink)  
bearfoil
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henra

Of course it's tiresome to read the same thing again and again. My point all along has been the lack of attention paid to this crucial piece, and further, I believe it to be a patent example of a design that ignores the relative importance of each of the control surfaces. Here in AF447, the Rudder as always remains. You may not recognize the problem, but aerodynamically a Rudder is a trimming device, a Vertical Stabilizer keeps the nose into the wind, without it, an aircraft can not fly.

In AA587, it is claimed the F/O is responsible for ruddering the V/S and Rudder off the aircraft. This "bicycling" of the Rudder pedals seemingly snapped off all directional discretion, the Airbus almost immediately shed an engine due to immense axial stress.

In AF447, the RTLU is proposed to have limited travel of the Rudder to 4 degrees either side of center, an amount calculated not to overstress the assembly at Mach.82. With RTLU FAIL on the list, It is arguable the Rudder was not limited, and may have been subject to full travel as if the a/c was at <250 knots. This too could have allowed the Vertical fin to bite off too much of a Mach.82 airstream failing in much the same way as 587.

I understand the RTLU was removed and tested to 7.9 degrees, a result that to me proves absolutely nothing. If a Rudder blows off its mountings,the VS remains, providing directional integrity. If on the other hand, a Rudder stays with, and the VS is torn off due to Rudder input, we cannot fly, period. It is telling that Airbus includes Rudder limiting; I am saying it could be taken a bit further.

The 330 has massive mounts (six of them) rooted deep into the Tail/Fuselage, but they failed. It is difficult to picture a vertical impact simply causing the VS/Rudder to plow down into the Body, then symmetrically rebounding, having taken the fuselage pieces with it.

Without suggesting the reason for the loss of VS, it would be easier to envision the tail with part of the fuselage attached impacting the Sea inverted, with the tail hitting first.

To say that it was merely momentum that failed the VS begs entertaining a fantastic sequence. It has been difficult to picture this massive aircraft having directional and aerodynamic problems at 37k losing all its forward speed quickly, then recover in some fantastic way to impact "en ligne de Vol" . Let's not forget that the "rotation" to the left at impact seems to have miraculously preserved the V/S structure in all its dimensions. Given the appearance of both fins, a loss at altutude for 447 is the simplest explanation, as there is precedent in 587.

Of far more interest is the chain of faults that caused a unique result from a problem that had happened many times prior. It's in there, it is.

jcjeant

Captain not seated? FA's not seated? No warning from cockpit? No Mayday? These pilots were in the swamp very quickly perhaps wrestling to regain control, g forces could easily have prevented anyone from donning flotation. If no air at altitude, consciousness is lost at 40 seconds tops.

rgds. bear

Last edited by bearfoil; 15th May 2010 at 22:48.
 
Old 15th May 2010, 23:48
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Captain not seated? FA's not seated? No warning from cockpit? No Mayday? These pilots were in the swamp very quickly perhaps wrestling to regain control, g forces could easily have prevented anyone from donning flotation. If no air at altitude, consciousness is lost at 40 seconds tops.
Forgive me, since this makes me rather queasy, but wouldn't the autopsies indicate whether the victims were already unconscious at the point of impact, verses still conscious? If your theory is that the aircraft was compromised in some fashion as to render the pressurization system inop, consequentially incapacitating (everyone) and given it took several minutes to hit the ocean, I'd would have thought that there would be a number of tell-tale symptoms during autopsy? Also wouldn't one or two oxygen masks have been found? Perhaps they were....?

-GY
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Old 16th May 2010, 01:08
  #1063 (permalink)  
 
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This subject has had so many posts, forgive me if this possibility has been discussed.
We talk of the crew losing control, but has "losing the crew" been considered?.
Thinking back to the old BAC111 windshield incident, where they were so lucky it happened at only 16,000ft, consider a total loss of pressurization at FL300+ and its consequences on the two pilots.
I know the way in which a 330 screen is installed is totally different and its possible it may not have been a screen letting go, but I believe the armoured flight deck door would have prevented an instantaneous equalizing of pressure throughout the aircraft if a serious decompression occurred.
Maybe some one could comment on the behaviour of a screen if it received a few thousand degrees from the direct hit of a lightening bolt.
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Old 16th May 2010, 02:10
  #1064 (permalink)  
 
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Hi,

This subject has had so many posts,
Indeed .. and many about the ACARS messages.
Where you see a link to your hypothetical scenario with those messages ?
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Old 16th May 2010, 04:24
  #1065 (permalink)  
 
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Originally Posted by ushumgal
Reverting briefly to the acoustic detection a year ago, I wonder what effect that tall ridge (running northwest) to the north of the new search area would have on a pinger lying on the ocean floor. If the submarine was to the south of it and the pinger north of the ridge, would the ridge tend to block the sound from it, or would the ridge in fact help deflect the sound upwards to where the submarine was? Just an idle thought I had, knowing nothing of underwater acoustics.
That's an interesting question. Sound will hug a surface very nicely. So it might have traveled up-slope as a traveling wave and been launched back off the surface at the ridgeline. The efficiency of this mechanism would depend on wavelength, size of obstacles on the slope, mud on the slope, and a host of other factors. It is, however, a possible way for the location to be very muddied. Hitting a surface with different salinity or temperature might also lead to ducting or reflections that allow the signal to travel great distances. (Although I doubt the signal strength would support very much greater range than simply up to the submarine given auv-ee's good analysis.)

Last edited by JD-EE; 16th May 2010 at 04:43.
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Old 16th May 2010, 05:13
  #1066 (permalink)  
 
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Update: "Seabed Worker" - position

The vessel was last reported at:-

15 May 2010 09:44z Hdg 282.4 Spd 01.4 3°05'10"N 31°03'54"W
15 May 2010 08:01z Hdg 180.4 Spd 00.7 3°05'28"N 31°03'46"W

The graphic below shows these positions as one.



mm43
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Old 16th May 2010, 09:58
  #1067 (permalink)  
 
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It has been difficult to picture this massive aircraft having directional and aerodynamic problems at 37k losing all its forward speed quickly,
Bearfoil, given the more likely locations of the wreckage it doesn't seem extremely likely the plane immediately shed all its forward speed at 37kFt.
In that case it should be much closer to the last known position assuming that things already went pear shaped while ACARS message were being transmitted

The 330 has massive mounts (six of them) rooted deep into the Tail/Fuselage, but they failed. It is difficult to picture a vertical impact simply causing the VS/Rudder to plow down into the Body, then symmetrically rebounding, having taken the fuselage pieces with it.
edit : /deleted see reason for editing

Still: A >40g vertical impact probably puts more load on the structure then aerodynamic forces at 270kts CAS with a RTL set at 7,9°

Last edited by henra; 16th May 2010 at 10:16. Reason: Correction: Trim Tank in A330 is in THS not VS
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Old 16th May 2010, 10:39
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You've hit it on the head! I honestly don't believe these guys knew what they were ab

The weather radar range was about 80-100 nm depending on tilt and gain adjustment. Usually there are 2 radar screens in the cockpit with different gain adjustments for different ranges. At approx 480 kt that is about an 8-10 minute window to become aware of the weather. Often coffee or snacks are brought up to the cockpit and a few minutes of conversation ensues. Not paying attention to the radar screen is possible for a few minutes, but I don't buy this scenario when the ITCZ is just ahead. The lack of mesoscale instability weather detection by the radar is a central question.

In regard to the recent threads on the bodies, I believe the BEA knows a lot more than was made public and should be made public. Consider the families of the deceased souls , the rapid gasification of the floating bodies and body parts, and the presence of sharks in the water and you will conclude that recovering the bodies was not pleasant for the French and Brazilian divers and crew, and this is not a good subject for the press.
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Old 16th May 2010, 17:05
  #1069 (permalink)  
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The report states the RTLU was removed and tested; it was found to be "stopped" at 4 degrees each side of center.

The obvious question, the Rudder is shown to be @ 40 degrees right in at least one photograph, and similarly positioned in another, these taken while in the sea, and after removal from the sea. In the chain of recovery, why is the rudder at such an angle? There is nothing in the report to explain this apparent discrepancy. If the RTLU FAIL was accurate, is it assumed that it would revert to its 'protect' position, though Fail was on the screen? At .82 Mach and an unrestricted Rudder in Alternate Law II, the danger is clear. Why is the vertical pick up arm fractured, but the Rudder hinges seem servicable? With 35 degrees of sweep "available", this arm would be tortured in virtually any plane, but most importantly (here) in the plane it was supposed to protect, (maneuvering).

About the Lateral defensive Rods. These parts, actually resembling straps more than rods, appear to have been subjected to above fail limits, as their mounts and structural integrity have been completely lost. Their position and posture on the mounting rail shows complete failure. This is indicative of Fail Plus loads in the lateral plane, a stress the report ignores in its march toward "Vertical only" stresses.

One last thing. The Female lugs have sheared in the area between structural webbing and uniform build up at the mount hole. Vertical loading would absolutely not shear these structures in this area from translated vertical loads. An extreme "bend" or "radial" resistance would be the only mechanism to cut these parts in two in this region. One would expect a failure at the lug insertion point with sufficient vertical energy. This is replicated at the vertical pick up arm, where the "end" snapped off due to vertical loading, a kind of stress that was designed for, ie Rudder loads in each direction.

Consider. The lateral rod mount, a rail between the lugs, is not shown to be deflected in the vertical. Yet the rods are destroyed. They failed in lateral, a failure consistent only with aerodynamic loading.

Consider. The vertical pick up arm failed in designed for expression. It is meant to keep the Rudder in longitudinal conformity with the VS. It performed. The eight rudder hinges show no damage, as evidenced by the Rudder's free movement at recovery.
 
Old 16th May 2010, 19:38
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cc45, in general, I believe there are very few sharks in the mid-ocean. Almost always, they inhabit coastal waters.
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Old 16th May 2010, 20:43
  #1071 (permalink)  
 
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bearfoil,

Having no structural design knowledge (former A320 and A310 pilot), much of your fascinating argument is going over my head. But I’m also having a syntax problem in your second paragraph. Quote:
“If the RTLU FAIL was accurate, is it assumed that it would revert to its 'protect' position, though Fail was on the screen? At .82 Mach and an unrestricted Rudder in Alternate Law II, the danger is clear.”

I may be misunderstanding your question, but, just in case you (or anyone else) is in any doubt, my understanding is that the system has to cater for a subsequent approach, go-around, and engine-failure. So RTLU failure will permit full rudder-travel. **
ECAM warns the crew that high-speed rudder protection is no longer available, roughly as follows (from memory):
RTLU 1 + 2 FAULT
USE RUDDER WITH CARE ABOVE xxx KNOTS

Chris

** (EDIT) But only after the Slats extension command has been given (cockpit "Flaps" lever selected to Config 1, or greater). Until then, the limter is frozen at the value current at the time of failure. (See HazelNuts39's post #1073 below.)

Last edited by Chris Scott; 17th May 2010 at 09:31. Reason: Corrections in light of #1073.
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Old 16th May 2010, 21:21
  #1072 (permalink)  
 
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originally posted by bearfoil ...
The report states the RTLU was removed and tested; it was found to be "stopped" at 4 degrees each side of center.
The RTLU was tested and found locked at +/- 7.9° which is a value consistent with FL350 and M0.80 (could also be consistent with other altitudes and speeds ). A schematic of the basic rudder control follows:-



The mechanical limit is such that when the feedback angle from the rudder exceeds that set in the RTLU, further application of hydraulic pressure is inhibited to the rudder rams. Failure of the hydraulic system following impact equals loss of hydraulic rigidity, allowing the rudder to swing freely and beyond its normal maximum limit of +/-31.2°.

Now, the above is my understanding of the control system, and as usual I may be wrong.

mm43
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Old 16th May 2010, 21:22
  #1073 (permalink)  
 
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Deep ocean sharks?

RobertS975....The Woods Hole Oceanographic Institution in Massachusetts has an extensive display of open ocean buoys including subsurface flotation buoys, usually 50cm thick glass balls covered with plastic hard hats, that are shredded by shark bites and embedded with shark teeth.
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Old 16th May 2010, 21:44
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mm43,
Thanks for the rudder schematics. Makes perfect sense to me.

bearfoil,
Does that answer your question?
Once hydraulic pressure was gone, the rudder itself will have been free to swing any which way, up to any mechanical limits that still existed. So the photos are useless in that particular respect.

As an ancient ancient... let me remind you of Concorde...



Before engine start, the elevons drooped, and the rudders waved about in the wind.

(Personal photo).

CJ
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Old 16th May 2010, 21:57
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Originally Posted by Chris Scott
... to cater for a subsequent approach, go-around, and engine-failure. So RTLU failure will permit full rudder-travel.
From the 1st Interim Report:
o F/CTL RUD TRV LIM FAULT (2 h 10)
Meaning: This message indicates the unavailability of the rudder deflection limitation calculation function. The limitation value remains frozen at the current value at the time of the failure (until the slats extension command is given).

HN39
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Old 16th May 2010, 21:59
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The obvious question, the Rudder is shown to be @ 40 degrees right in at least one photograph, and similarly positioned in another, these taken while in the sea, and after removal from the sea. In the chain of recovery, why is the rudder at such an angle?
Bearfoil,
mm43 already gave the answer to this: The RTLU stops depend on hydraulics to effectievly limit the travel of the rudder.
Obviously there was no hydraulics left in the drifting rudder.

Re fracture of vertical pick up arm: Difficult to say but depending of the degree of freedom in the hinges in the vertical plane the vertical load might just have concentrated on the pickup arm first.
Lateral defensive rods:
Yes they were torn off their mounts. But this does not necessarily mean the force was excerted laterally. Could also have happened from vertical force. As they are angled ~45° that wouldn't make much difference in the damage pattern of the rods/mounts.
Edit: Also the fact that both aft lateral rods were torn of the spar is an indication for some kind of symmetrical force. Otherwise only one should have been torn off as the aft mounting structure was not completely torn off the VS.
/Edit
Mounting lugs:
A rotation of the VS around a lateral axis i.e. tilting to the back or front could result in the same effect: shearing of the lug. And it only happened to the first lug, not the other ones.
If it would have been lateral force there is a high probability all three sets would have sheared. And the shearing surfaces of the two sides of the female should look differently: One broken more in torsion, the other more in strain.

So for me a longitudinal tiliting of the VS seems to match the damage pattern of the mounting lug(s) much better than the lateral displacement.
I still haven't found any (at least for me) convincing evidence of a lateral break up of the VS.
Have a look at the deformation of the ribs in the VS. They are deformed vertically which would also match a longitudinal tilting of the VS.
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Old 16th May 2010, 22:09
  #1077 (permalink)  
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Nothing more military "smart" than to watch elevators, ailerons, flaps, and rudders wake up and come to attention on deck, eh?

Point being proper Rudder deployment depends on hydraulics being servicable, and any controllers working quickly, and properly. With RTLU FAIL, one pictures a wide range of deflection not in concert with airspeed. Hence the warning. In AL II this a/c has few protections, and without visibility and instruments, how does one meter Rudder input? That Rudder stops failed was a follow on to loss of airspeeds, there may be nothing more to the saga, but the laterally imposed damages to the Rudder's mountings needs to be addressed. These findings of the BEA are in reverse, an unwinding from demonstrables at recovery. My mentioning these areas doesn't explain away anything, but the fact that they exist suggest an expansion may be necessary.

The spoiler is not shown in the BEA report, yet there are several excellent pictures of it in the thread. This panel was beaten to death, I suppose from its extension into an extreme airstream. Looking at the entire view of the 330 and the severed and found pieces suggests the loss was of mostly control surfaces. Nothing unusual about that, however it is suggestive of an out of control a/c at high speed, attempting to slow and regain controllability. My understanding is that at ALII controls are free to deflect to their stops; why would it be impossible for a pilot to attempt recovery, but without feedback make a hash of it?

This aircraft was out of control at maximum altitude, losing its energy to alight in the ocean as described challenges reason.
 
Old 16th May 2010, 22:18
  #1078 (permalink)  
 
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My understanding is that at ALII controls are free to deflect to their stops;
According to the BEA report the stops were at 7,9°.
Only when hydraulic fluid is gone (i.e. drifting on the water), this will not be enforced to the rudder anymore
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Old 16th May 2010, 22:21
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Update: "Seabed Worker" - position

The following four positions are the latest available:-

16 May 2010 05:32z Hdg 067.6 Spd 02.0 3°04'31"N 31°01'57"W
16 May 2010 03:49z Hdg 086.6 Spd 01.5 3°03'53"N 31°03'40"W
15 May 2010 17:10z Hdg 107.2 Spd 01.7 3°03'44"N 31°03'06"W
15 May 2010 15:33z Hdg 254.5 Spd 01.3 3°03'51"N 31°01'32"W

They are all to be found within the 1.5NM radius circle with the cyan border. In fact there are seven positions in that circle, all within the last recorded 24 hours.



mm43
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Old 16th May 2010, 22:37
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Chase888 (Post 1061) has "losing the crew" been considered?.

If that had occurred at altitude the cockpit door wouldn’t have stopped the decompression and the aircraft in all likelihood would have rapidly developed an unusual attitude leading to break up or water entry at high speed.

However, the crew being partially incapacitated is more than possible in a Airbus with side-stick if the crew are not wearing their harness or it’s only loosely fastened, i.e. a control yoke is as good as a zimmer frame, you can grab it and it will normally catch your legs before you hit the overhead panel.
This might be a possible answer to the injuries on the recovered bodies, i.e. they were either moving around the aircraft or had their lap-belts unfastened when they encountered unexpected turbulence, their injuries may have been so severe from this that they never made it back to a seat to strap in.
When the aircraft hit the water it may have broken in 2 or 3 large sections, anything loose in the cabin being ejected through the open end as it sank.
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