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AF447

Old 8th Jun 2009, 20:15
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just a thought: assuming you are flying a FBW bus and for some reason (say botched paint job in Perpignan, icing mid-Atlantic, faulty wheel on ground sensor in Warsaw) you get all sort of spurious sensor data confusing the - admittedly redundant and fault tolerant - automation. What can you do to regain basic flight control ? I pretty sure that the A330 will behave just as the 320: it's possible but complicated (no big "red button" to kill the automation) and probably not taught in standard training... Even if it quite literally saved the day in many unreported cases I wonder what will be the public perception if it turns out that automation was a contributing factor here...
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Old 8th Jun 2009, 20:15
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some questions

There are three pitot probes on the A330, according to ACARS. One on each side at the front I know. Where is the third?

Is it possible that the VS breaking away from the fuselage in extreme turbulence beyond certification limits as initial event would cause a chain of events that are consistent with the ACARS messages we know? I doubt it but the picture of the VS in one piece will certainly cause rumors. So it would be better to face them proactively, if possible.

Is the haste and big PR regarding the exchange program for pitot tubes maybe a little too much...?
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Old 8th Jun 2009, 20:18
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from the same source as the previous 2 photos.
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Old 8th Jun 2009, 20:22
  #684 (permalink)  
 
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Dani

The vertical stabilizer broke this way because it is designed that way. It is hold by several titanium bolts on top of the rear fuselage. The fin itself is designed much stronger than the bolts. So either the fin remains on the fuselage or it breaks. If it breaks, it breaks exactly there.
I think I understand the point you are trying to make, but you certainly have it the wrong way around.

The VS is held, as you say, by bolts to the rear fuelage. However, the bolts are far stronger than the VS, and (as in the case of the AA A300), the bolts remain in their mounting brackets, still attached to the fuselage, together with the broken ends of the VS lugs.

Yes, the VS tends to break at this point, but it is not "designed" to do so - it is simply the weakest point / link in the assembly.

HTH

FBW
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Old 8th Jun 2009, 20:22
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Regarding separation of the Vertical Fin on Airbus aircraft:

I find it hard to believe that without the "protection" that is normally provided by computer on these aircraft, that a pilot could exert enough force with his feet on the rudder pedals to cause the separation of the vertical fin no matter what the IAS ?!?! I guess I just remember 'driving' my good old 'truck', the DC-ATE !
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Old 8th Jun 2009, 20:25
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Fly-by-Wife:
A further confirmation that the picture shows the entire VS & rudder assembly is that the start of the change in angle of the leading edge of the VS is clearly visible in the original photo (not so obvious in the extracted picture).
Indeed. It seems to me that people are not taking into account the foreshortened view of the assembly in the original photograph, caused by the angle from which the photos were taken.

If you look at the circle of European stars at the top of the stabiliser in the original photo, the "circle" appears as an ellipse with a major to minor axis ratio of about 2:1. Correct the perspective in Photoshop or similar to render the EU logo circular, and you will find that the assembly quite clearly appears complete with the correct profile for a 330 VS & rudder.
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Old 8th Jun 2009, 20:27
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DC-ATE. You had power assisted cables, 330's have hydraulics, powered by enormous energy controlled by "feet" that could deflect the Rudder a disastrous amount in the wrong "LAW". F/O AA587, "pumping the pedals", or 447 w/o limited travel but plenty of authority? See?

Refer #693, above
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Old 8th Jun 2009, 20:34
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Will Fraser -
DC-ATE. You had power assisted cables, 330's have hydraulics, powered by enormous energy controlled by "feet" that could deflect the Rudder a disastrous amount in the wrong "LAW". F/O AA587, "pumping the pedals", or 447 w/o limited travel but plenty of authority? See?
Well, I guess I understand what you're saying, but I fail to see how that is "progress".
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Old 8th Jun 2009, 20:37
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This is my first post, but I'm a long time reader and I think I can contribute some information. First of all, compare the pictures of the recovered stabilizer with this one: http://www.eads.net/800/en/gallery/a...4/42002549.jpg

If you look closely, you will see that the stabilizer is indeed fairly intact and the part with the mounting points is also still there (though under water). So obviously it must have been that bolts that failed, the stabilizer didn't break apart. Only a small part at the rear is missing.

I guess it's plausible that the stabilizer detached when the plane hit the water. I would like to point out though that the radio antenna is located in the vertical stabilizer, so the crew would have been unable to use the radio if the stabilizer had detached during flight, while the Satlink ACARS messages would still have worked. Not drawing any conclusions, since that's up to the investigators and, also we don't even know where they found the stabilizer, and there could be a thousand other reasins why the crew didn't use the radio, but still an interesting fact.
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Old 8th Jun 2009, 20:49
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It's only progress (it is) until the newer system "fails" catastrophically.
The argument is FBW, a topic I know you are fluent in. As in AA587, the system "allowed" for too much travel, and the PF wasn't in tune with his a/c. The flaw is and will always be interface. Here, the a/c was established in high cruise, something happened. The VS/R assembly parted the fuselage, unknown when. The transition from established cruise to a handful of weasels happened when the a/c "sensed" a parameter excursion, and undid the a/p a/t, etc. reverted to "ALT Law", and as much as said, "your a/c". Since tha a/c could not be hand flown at this point, (demonstrably, with two highly experienced airmen seated in the chairs), one must question the disconnects and the survivability however flown, either by automatics (which "quit"), or by the humans.
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Old 8th Jun 2009, 20:54
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It's only progress (it is) until the newer system "fails" catastrophically.
I rest my case.
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Old 8th Jun 2009, 20:54
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As in AA587, the system "allowed" for too much travel, and the PF wasn't in tune with his a/c.
Pure speculation, there is absolutely no evidence to support this!
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Old 8th Jun 2009, 20:56
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mp, The statement refers to facts in evidence. If you have a parsing disconnect, or vocabulary criticism, that's another thing. It is not intended as a conclusion re: 447
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Old 8th Jun 2009, 21:02
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Will,

Maybe too much going into the v/stab failure, at this time...other issues should precede the structural failure, like on other commercial (transport category) airplanes.

Further, any statements on the "weak point", pre-designed failure location on the structure etc are moot simply because this is not the design process. Sadly, accidents will show you what really is the "weakest point".

For that matter, failure during the certification related ground tests for the structure is not expected/required.

So, for the structure, in order to fail you need a catastrophic event.

Cheers
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Old 8th Jun 2009, 21:02
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It is quite shocking that after 600+ posts here and 1900 on the previous thread that persons claiming to be pilots still cannot grasp the fundamental differences between pitot, static, TAT probes, AOA sensors, attitude references and air data references.

It may be a good idea to lock this thread and start again because last time the mods did that it did make a difference for the first few hundred posts.
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Old 8th Jun 2009, 21:02
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mp, The statement refers to facts in evidence
There is absolutely NO evidence to support the tail breaking away in flight or the pilots over controlling or exceeding the ultimate loads.
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Old 8th Jun 2009, 21:05
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Will Fraser,AA587 showed that even a conventional aircraft such as an A300 cannot be flown without a vertical stabilizer and the only case that I know of a jet aircraft that survived the loss of a VS was a B-52 that lost the majority of its VS in severe CAT in 1964.
The problem with AA587 ws the use of full or nearly full opposite rudder inputs.To quote from A300-600 fcom bulletin 827/1 "Such inputs can lead to loads higher than the limit,or possibly the ultimate loads and can result in structural damage or failure".

Last edited by tubby linton; 8th Jun 2009 at 22:01.
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Old 8th Jun 2009, 21:05
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AA587, I'll reread. tubby, that is my reference.mp, post the rest of my comment please. You are out of context

tubby I thought I made it clear re: AF447, and the rudder. It is as you say.
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Old 8th Jun 2009, 21:05
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Originally Posted by plane-g
I would like to point out though that the radio antenna is located in the vertical stabilizer


Wrong. All VHF Antennas are mounted on the fuselage, VHF 1&3 on top and VHF2 below. Check out smartcockpit.com (page 4 / antennas location) before posting such nonsense.

Regards,

MAX
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Old 8th Jun 2009, 21:07
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Max,
HF antenna is in the fin.
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