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AA 587 -- Vertical stabilizer & composites (thread#3)

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AA 587 -- Vertical stabilizer & composites (thread#3)

Old 22nd Nov 2001, 02:27
  #41 (permalink)  
 
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I am impressed by several of the posts re the curing and aging of the composites but I wonder if anyone has any detailed information re how the exterior of the aircraft are "washed". I raise this question because my first reaction to learning that the Tail was made of composite appears to have snapped off was that possibly some member of the maintainence crew could have sprayed the tail with a solvent during a routine inspection. I finally dismissed that as being probably not a practical method and would also be too obvious.

After thinking for a few days I rememberd an occasion when a plane I was about to take off in was being de-iced and they were spraying it with hoses. that led me to wonder how they normally "cleaned" the exteriors of grease, etc..

Anyway, as luck would have it I remembered I knew a guy who was in the Air Force Reserve at Travis and his job was maintainence of the C-13o and other aircraft stationed. When I asked him how they cleaned their planes and what they used he paused for a second and said he wasn't exactly sure because they
...use Outside Contractors. All he could say was that they used solvents of some kind and they had to use different solvents for different components depending upon what the materil was made of, and he had seen them masking off certain areas during the process.
I asked him if these solvents would be classified as Hazordous Materials and he said yes.
Now here's what I am puzzled about:

o Is there anyone out there who is aware of what solvents are used, how many kinds there are, their ingredients, are there any standards as to what can and cannot be used, etc.?

o Could the use of a solvent mixed to clean Aluminum being used on a Composite reduce its strength? Intentionally or un-intentionally.

o Could a specific solvent be mixed that would weaken the specific Composite used in this Tail?

o Do the Civilian Airlines also use Outside Contractors to clean their Aircraft.

o If so, are the solvents delivered in tanker trucks and applied to the aircraft from the trucks or put in holding tanks at the airport.

o When, where and by who was 587 cleaned, washed or de-iced?

o Has there been any effort at all to overhaul the screening, background checks and overall scrutiny of the Maintainence personnel and their associated sub-contractors. I haven't heard of much other than those who clean the interiors and deliver the food. The screeners at the gates have been getting pounded (deservedly so) and will be Federalized but that is, to some degree, locking the barn door after the horse is out. I would be encouraged to learn of a comparable scrutiny of maintainence personnel.

Now, I am not a conspiracy theorist or alarmist but I do recall that among the hundreds of people the FBI have rounded up there were several... 8, 10,or 12, who were Mid-Eastern and had applied for and/or received Hazardous Material drivers licenses.

The consensus of concern appeared to be possible use for truck bombs or biological material.

It's most likely a stretch on my part but could these aircraft cleaning solvents also been a reason? I hope not and I welcome intelligent refutation of my thoughts along these lines. I have actually deliberated posting here as I had , well, still have, a fear of looking ridiculous. But I finally concluded I would have been thought ridiculous if I had feared the scenario of 9/11 on 8/11.

But leaving sabotage out of the equation, what about these various cleaning solvents and their effect on composites?
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Old 22nd Nov 2001, 04:19
  #42 (permalink)  
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Lightbulb

We wash them with detergents, just like your car only in bigger quantities. The bits that are masked off are the various orifices where we don't want water to go - like the static ports, outflow valves, and cooling system intakes etc. After washing is finished, specific parts such as the landing gears are re-lubricated. De-icing fluid is a special non-corrosive mixture developed and certified for the purpose.

While solvents are sometimes used for cleaning specific components, this is done only under controlled conditions. That is, they are cleaned at specific periods as part of the schedule of inspection. Chemicals used on aircraft are strictly controlled, may only be purchased from approved sources and the approved chemicals are listed in the Aircraft Maintenance Manual with the uses for which they are approved. The work is done by or under the supervision of licenced technicians and a release certificate is issued for the work.

I hope this satisfies your curiosity and eases some of your worries.

**********************************
Through difficulties to the cinema

[ 22 November 2001: Message edited by: Blacksheep ]
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Old 22nd Nov 2001, 22:08
  #43 (permalink)  
 
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Having been prompted by todays "Daily Telegraph" I have reread this incident report

The disturbance was accompanied by a loud bang which was noted by both the flight crew and some of the cabin attendants. They all reported the noise as being coincident with the disturbance.
Furthermore, there was nothing from the engineering investigation that could explain the loud noise reported
Could some as yet undetected delamination have occurred?
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Old 22nd Nov 2001, 23:13
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>
The disturbance was accompanied by a loud bang which was noted by both the flight crew and some of the cabin attendants. They
all reported the noise as being coincident with the disturbance.<

Sounds like a recoverable engine surge. Quite often these are so quick that they will not be caught by DFDR sampling rates. Of course the quick ones don't do anything beyond a shake of the aircraft (no time for roll etc.)
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Old 23rd Nov 2001, 06:05
  #45 (permalink)  

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Question

Is there any truth to the rumour that this aircraft had experienced "severe turbulence" some time ago and was, (after return to service) "written up" several times for vibration in the "tail" and that a T/O (with this aircraft) was recently aborted in SanJuan for the same reason?

I hope not!
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Old 23rd Nov 2001, 21:32
  #46 (permalink)  

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lomapaseo

Sounds like a recoverable engine surge. Quite often these are so quick that they will not be caught by DFDR sampling rates. Of course the quick ones don't do anything beyond a shake of the aircraft (no time for roll etc.)
Very good point. How about a wake encounter causing the yaw and the yaw causing the self clearing "pop" surge.
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Old 23rd Nov 2001, 22:36
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Exclamation

When looking at the photos on page One of this thread, one may notice that at least two of the six hinge fittings showed parts of the vert stab composite attach points still attached, whereas the rest had a clean separation from the pins. Therefore it's conceivable that the vert stab may not have totally severed at once, but may have ripped off one side and then fluttered momentarily before tearing completely lose from the opposite attach points. This, in conjunction with a fluttering rudder may account for the "rattle" heard on the CVR. Also, it's interesting to note that the engines were severed at the wing rather than at the pylons, suggesting a severe airframe overload from lateral ocillation.
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Old 24th Nov 2001, 05:49
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> note that the engines were severed at the wing rather than at the pylons, suggesting a severe airframe overload from lateral ocillation. <

I doubt that you should infer anything from the separation point. The airframe manufacturer owns the loads no matter where generated and sizes the relative strengths of the joints.

The engine manufacturer must only show that his side of the joint does not deform under a full blade out test. Typically the airframe manufacturer provides margin way above the engine generated load so as to cover other things like gust loads etc.
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Old 25th Nov 2001, 01:05
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Reading this previous incident report at http://www.aaib.dtlr.gov.uk/bulletin/feb01/n14065.htm , you get the impression that it's almost as if it's the B737 rudder actuator problem in reverse (i.e. instead of seizing "hard-over", suffering instead from an excess of motility)

How much does the A300-600 rudder limiter system restrict rudder travel when enabled (gear and flaps up)?

The DC-8s had about 7 degrees with gear and flaps up...15 degrees with both down.

Perhaps the rudder limiter system faulted (permitting the greater travel at 250 knots - as the autopilot coped with the wake turbulence upset) ??

It's beginning to sound to me like a hydraulic hammer may be induced by the rudder limiter-valve cycling rapidly (much like audio feedback can cause a superheterodyne squeal). When they hit the 747 wake, the Flight Control System would have made a much larger than normal rudder input to correct the yaw and perhaps set up a hydraulic reverberation in the rudder limiter valve line that caused the rudder's large lateral oscillations, thereby setting up a destructive rudder-induced flutter in the vertical fin. We've all heard the very noisy hydraulic hammer that you can get in household water-pipe plumbing. If you didn't turn the tap off quickly, you'd swear the wall was going to fall down. Due to the corrective input being from the autopilot (and not the pilot's rudder pedals) that may be a factor in the destructive hydraulic hammer being aroused between the limiter valve and rudder actuator. The biggest factor in the reinforcing (or damping) harmonic of hydraulic hammer is the distance between the two "chattering" hydraulic line components and the feedback harmonic that can be set up. Some hydraulic systems necessarily have Quincke valves incorporated - coils that are designed to soak up these types of destructive hydraulic chatters. The initiator of this rudder-induced flutter may need to be an external force (such as wake turbulence) requiring a rapid autopilot input (i.e. to say that normal rudder pedal input and pilot reaction times would not create the conditions for hydraulic chatter).
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Old 25th Nov 2001, 02:19
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During climb, unless there's an engine failure, there's no reason for any pilot to have his feet on the pedals.
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Old 25th Nov 2001, 03:45
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Question

To all the engineering types-

Would one expect the design of the vertical stab attach points to be able to withstand the compromise of one of the attach points and retain strucural integrity?

How is the possibility of a lightning strike (not related to the AA accident) designed into a composite structure? I have read previously that some metal bonding is required on composite structures.How would one test to see if a lighting strike compromised the structure?

Thanks.
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Old 25th Nov 2001, 17:31
  #52 (permalink)  

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Beg to differ GlueBall,

Pilot flying should always be ready to take full control, including rudders (eng. failure, turbulence, control problems...)
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Old 25th Nov 2001, 19:33
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light 587 Observations From www.AviationNow.com - Pieces I Cut Out

Aircraft Went Through All of This and Never Came Apart

In May 1997, the crew of an American A300-600 -- not N14053 -- stalled the
aircraft during a right turn to enter a holding pattern while on approach
to Miami. As the plane's nose pitched up 12 degrees and the bank angle exceeded 50 degrees, the first officer applied full left rudder to correct the roll, NTSB determined.

The bank angle hit 56 degrees and the angle of attack topped out at nearly 14 degrees before the A300-600's attitude changed dramatically. "The aircraft then pitched down, and entered a series of pitch, yaw, and roll maneuvers as the flight controls went through a period of oscillations for about 34 seconds," NTSB said in a report on the incident. The crew recovered the aircraft at about 13,00 feet, and landed without further incident. Several dozen people were injured.

Only 30 Degrees for Flight 587

After the three sudden movements, the plane banked sharply left and nosed
over about 30 degrees. The crew could not regain control and the aircraft
broke apart, with its vertical fin, rudder, and both engines separating
from
the fuselage.

NTSB Chairman Marion Blakey remains in contact with U.S. Federal Bureau of
Investigation Director Robert Mueller. But so far, NTSB has no evidence
that
points to foul play as a contributing factor to the accident.

And What About This?
>
> Several witnesses reported seeing fire, smoke, and debris coming from the
> side of the aircraft. Reports conflicted over whether it was the right
side
> or the left side. One witness at JFK reported seeing the aircraft headed
for
> the ground at a severe nose-down angle, followed seconds later by a plume
of
> smoke.
>
> The Associated Press reported that U.S. Federal Bureau of Investigation
> officials were looking into the possibility that there was an explosion
> onboard Flight 587. It was not clear whether they considered the explosion
> to be from a bomb or some other non-aviation source, or if they were
> considering something mechanical, such as an engine failure.
>
> In perhaps the most perplexing development Tuesday, the A300-600's
vertical
> stabilizer and rudder were pulled from Jamaica Bay -- about a half-mile
from
> the main debris site -- and both pieces "appear to be complete," Black
said.
> Television images of the tail showed no marks, holes, or other structural
> damage that would indicate that the tail was knocked off by debris -- such
> as from a disintegrating engine.
>
> And Why Wouldn’t He Talk About It?
>
> While no sounds pointing to explosions have been picked up from the CVR
> analysis sessions, Black said investigators noted "noises" on an air
traffic
> control tower tape of communications between controllers and Flight 587.
The
> noises -- which Black did not describe in detail -- were heard at about
the
> time crew lost control. He did not say what the sounds indicated.
>
> Both Engines Came Off?
>
> The plane's No. 1 engine ended up in a gas station parking lot about 700
> feet from the crater, while the No. 2 engine came down in about 800 feet
> from the main crater. All of the debris is "more or less in a line," Black
> said.
>
> Interesting
>
> All communications with the cockpit were normal prior to the crash," White
> House spokesman Ari Fleischer told reporters. Asked if that meant
officials
> were ruling out terrorism as the cause of crash, Fleischer said not yet.
>
> Ridge then convened a conference call with other cabinet members,
including
> representatives from the U.S. Department of Transportation, Federal
Aviation
> Administration, and FBI to assess potential homeland security threats. New
> York City and state officials were also involved in the talks.
>
> Wake Turbulence
>
> Neither encounter was particularly severe, investigators said, and were
> certainly not violent enough to rip an airworthy A300-600's tail off.
>
> Checking the Tail
>
> Inspections of Airbus A300-600 and A310 tail sections haven't turned up
any
> significant clues that would explain why an American Airlines A300-600's
> tail ripped away shortly before the aircraft crashed into a New York City
> suburb last week.
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Old 1st Dec 2001, 03:04
  #54 (permalink)  
 
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Haven't seen any mention of this in the news but this incident must ask a few questions!
http://www.ntsb.gov/ntsb/brief.asp?e...28X02309&key=1
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Old 1st Dec 2001, 08:42
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FAA has called for visual inspection of plastic A300/A310 tails. NTSB recommended NDT testing of composites after an MD-11 turbulence event in 1995. Fast forward to 2001 -- we kill a bunch of people and the FAA still says visual inspections are adequate.
Queries
a. Does anyone recall the details of that MD-11 incident or have a URL?

b. Anyone any idea how much composite structure is in an MD-11?
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Old 1st Dec 2001, 09:48
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I read in the paper that the tail and rudder have been sent to NASA for them to inspect.
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Old 1st Dec 2001, 09:52
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Rudder problems on another AA A-300 as reported by CNN. (See below) The vertical stab from AA587 has been sent to NASA's Langley Research Center (Norfolk VA area, and a lead NASA Center for aeronautics) for detailed study.

"LOS ANGELES (CNN) -- An American Airlines Airbus jetliner departing Lima, Peru, Wednesday evening experienced severe rudder problems during takeoff, forcing it to return to the airport, CNN learned Friday.

"The aircraft, an Airbus A300-600, is the same model aircraft as American Airlines
Flight 587.

"In Wednesday's incident in Peru, the pilots reported "fish tailing" soon after takeoff.

"An aviation source told CNN the aircraft experienced severe rudder fluctuations. A
preliminary NTSB report said the plane landed safely and its flight recorders have
been pulled for further investigation.

"CNN has previously reported on yet another incident involving an American Airlines
Airbus A300-600. That plane, on a flight from Colombia to Miami, Florida in 1999,
had to abort its final approach after the pilots experienced what they called severe
rudder deflection problems.

"NTSB spokeswoman Lauren Peduzzi, reached late Friday, said she had no information on any incident in Peru and would not know anything until Monday.

"American Airlines told CNN the plane remains in Peru but the flight recorders have been sent to the NTSB in Washington. An airline spokesman said no previous problems with the jet had been reported.

After the crash of Flight 587 the FAA ordered airlines flying the A300-600 to
visually examine the tail sections for signs of possible stress cracks. But critics said
that more sophisticated tests are needed to detect any problems with the vertical fin
and rudder which, on the Airbus, are made of composite plastic materials and not metal."
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Old 1st Dec 2001, 11:40
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This is from the Aviation Week website, regarding the Miami incident in 1999...

In May 1999, another American A300-600 experienced multiple rudder deflections while on final approach to Miami, but landed without incident. A probe revealed that the autopilot's wiring had been cross-connected by American mechanics in Tulsa.
I wonder if a cross-connected autopilot had anything to do with the most recent Peru incident?
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Old 1st Dec 2001, 11:44
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Dagger Dirk wrote " ... after an MD-11 turbulence event in 1995 ... Does anyone recall the details of that MD-11 incident or have a URL?"

Maybe you are thinking of this one: In 1992 China Airlines Flight C1-012, an MD-11 delivered earlier that year, encountered turbulence (described as "moderate") at FL330. Control of the plane was lost and parts of the left and right elevators separated. According to reports, before the captain regained control both roll and pitch exceeded 30 degrees and the plane stalled 4 times. I recall the reported length of time that the plane was out of control but it strains belief. The NTSB report is listed as AAR-94-02 but it came out before they
began web-posting. Not sure but I think that this same MD-11 was destroyed in 1999 after a landing at Hong Kong that was somewhat similar to the 1997 Fedex MD-11 accident in Newark.
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Old 1st Dec 2001, 16:42
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Brian B,
You can find that CI MD11 Turb Report here:
AAR94-02.pdf
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