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AF447

Old 10th Jun 2009, 21:35
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http://www.dcs.gla.ac.uk/~johnson/pa...Submission.pdf


The Dangers of Interaction with Modular and Self-Healing Avionics Applications:
Redundancy Considered Harmful
C.W. Johnson, Ph.D.; Department of Computing Science, University of Glasgow, Scotland.
C. Michael Holloway, NASA Langley Research Center, 100 NASA Road, Hampton, VA, USA.
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Old 10th Jun 2009, 21:48
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pth

I understand your advice, do you understand you are seemingly suggesting it to an autopilot? As I understand it, at least until 0210, tha a/c was under control with a/p flying. The involuntary disengage is reported at that point, and for four minutes no conclusive data to prove what was going on. Tha a/p may have disconnected because it couldn't accomplish what you are demanding: nose @ horizon, wings level, turb pen. speed, etc. What exactly do you mean by "what has happened to us as pilots?"

Will
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Old 10th Jun 2009, 21:53
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syseng68k

HF Antenna: The state of this would be reflected in the vswr reading, which essentially says how well the transmitter is matched to the antenna. If the antenna is missing, or cable open circuit or shorted, the transmitter autotune would detect it and either run at reduced power or shutdown completely.
This may depend on the transmitter being keyed to detect it. On receive there is generally not enough power available anywhere to run a VSWR bridge to detect the mismatch from a disconnected antenna.

These days a missing AMU, antenna matching unit, would probably be noticed. The transmitter would probably maintain communications with the AMU as a health check. In the bad old days I've had my fingers upon there was no such knowledge in the transmitter until you tried to use the AMU, as when the transmitter keyed.

{^_^}
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Old 10th Jun 2009, 22:21
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Autopsies

exames médicos legais are autopsies
One could think of it as legal medical exams, where legal means a medical exam that has to be legally done ( as in cases of unusual deaths)
Note autopsies are not legally required in Brazil, although often done
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Old 10th Jun 2009, 22:35
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Will Fraser -
What exactly do you mean by "what has happened to us as pilots?"
I think that what -protectthehornet- means (correct me if I'm wrong PTH), is that you don't want the auto-pilot and/or auto-throttles engaged in those conditions. HAND FLY the aircraft!! BTDT.
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Old 10th Jun 2009, 23:04
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allowing aerodynamic forces to lever the tail backward just enough to allow 500+ MPH air to penetrate into the body of the tail section - this would probably be enough to pry the tail section from the empennage
The airplane could fly with the fairings removed at max q and the dynamic pressure wouldn't remove surfaces. Will try to write a brief tutorial on aerodynamics in the tech section so as not to clutter up this section.

If the airplane was experiencing turbulence severe enough for the crew to phone home a report, then if the Captain was in crew rest, would think he'd make his way back to the seat.
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Old 10th Jun 2009, 23:14
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I would then propose an alternate theory - from the visible damage to the tail section's lower region - the presence of middle and rear mounting boxes that have been torn from the empennage structure - perhaps the front mounting lug failed, (then bad things happen)
Sure, if the front mounting lugs weren't doing their job bad things would likely happen. The question isn't so much how the tail would subsequently unravel in your scenario, but why the front mounting lug would fail in the first place.

You can't say the tail would or wouldn't have fluids on it, especially after being in the waves for a few days. An estimation of 'likely or not' doesn't matter either.
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Old 10th Jun 2009, 23:46
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Eur Sam Client,


Deviation clearance, over the ocean ? if I am approaching an area of severe weather over the ocean and need to deviate before I get 'clearance' I will do so to whatever extent I need while putting out advisory calls to other aircraft
on oceanic and guard VHF frequencies, I have done so and will again as have many of us.


There is not a professional Pilot on this forum that would penetrate convective activity because they are waiting for 'permission' to avoid it.


I would do the same over land for that matter if I was unable to reach the controller in time.
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Old 10th Jun 2009, 23:48
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Why so indeed. You apply the 'Inflight Weather Deviation Contingency Procedure'. In short: if you can't get an ATC clearance in time and have to deviate around weather, you do. Transmit a PAN on guard and if the deviation is more than 10nm, climb 300ft if south of track, descend 300ft if north.
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Old 10th Jun 2009, 23:53
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The VS on 447 didn't part as 587's did. The likeliest explanation is that the Clevis/Pin points were strengthened as a product of 587's failure. Catastrophic failure isn't complex, it occurs at logical weak points. If the pins, web system of the 330 has enhanced structure, what's next? The next mating structure, in this case a combination of box/tower 'blocks', with their insertion into stringers, bulkheads, and decking.

The most probable origin of the energy was airflow impacting one surface of the fin/rudder at an angle that surpassed design load and then failure point. Laterally. Longitudinal failure I think is a far more remote possibility.

If the failure happened at altitude, and the VS/Rudder was resisting a yaw, the lack of controllability in this axis would cause a roll, and it is unlikely to have been recoverable. The a/c would then... well, most likely tumble. imo. sorry
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Old 11th Jun 2009, 00:35
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Tech log's not the place. Will make it compact.

Transport aircraft are demonstrated to an FAA FAR requirement that exceeds Vne at 1g. Flutter is a possibility, but simple structural failure is more likely. The WTC aircraft were flown well beyond Vne without flutter for example.

Mach buffet is not to be confused with flutter. It is merely flow separation on the wing due to stronger than normal shock waves, and is a function of lift and Mach number. It's operational limit is defined by the level of uncomfortable vibrations felt in the cabin, and is not destructive.

The tail is designed to a higher design Mach number than the wing, and is characteristic of thinner airfoil sections, and/or increased sweep so you have unhindered control to back out of buffet. Flutter wise, the tail is stiffer than the wing due to structural aspect ratio/stiffness, and the wing will typically flutter first.




Failure due to flutter could be considered less likely than encountering gusts at beyond Vne speeds. Even then, the wing would have load alleviating fuel in the tanks, so it could withstand more than you might expect. It's entirely possible that the weak point could be the horizontal tail. If it departed in a downward direction, it could peel that section of empennage with it, leaving the vert momentarally attached at the front.

Apologies if this is too long. Bin if desired.

Last edited by ClippedCub; 11th Jun 2009 at 12:31.
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Old 11th Jun 2009, 00:50
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Originally Posted by Ground Brick
Minimum SATCOM link bandwith is 16 kbps - all known ACARS data can be transmitted in 1 sec.
I believe ACARS via satellite uses 1-10kbps (approx) channels. High bit-rate channels don't make much sense for a system where you might have a few hundred aircraft sending a short message every few minutes... if you can't keep the channel full (e.g. 40-60% average load) then you're just wasting satellite bandwidth.

SATCOM modem also can take responsibility to repeat data, if not send propertly, so only 2:14z events data can be incompleted\not fully transmitted.
I suspect an incomplete message will be dropped at the ground station; the protocol will request retransmission a number of times if data gets lost between the aircraft and the ground, but eventually gives up.
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Old 11th Jun 2009, 00:52
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Good Insights AVSPOOK

avspook said:
Its can be programmed for number of retries - This is the VHF ACARS they are talking about, on some AB's will ahve a dedicated provider eg SITA however you may alos have the option to swicth to another provider (Arinc) however it will keep interrogating the SAT until it offload its message.

The company i worked for the VHF had 3 goes at offloading the ACARS before switching to SAT , It figured if it missed 3 offloads it must be out of range of a Line of site VHF station & then switched to the more expensive SAT option.


No HF mesgs - no hf fault same for engines same for Inertial Data from the ADIRU teh ACARS Hit the SAT... It knew where the aircraft was (lat long) it knew where to find the SAT and it beam steered the Antennae to get that hit

at the Maintenance center for both Boeing (Aircraft Health Management option) and airbus (AirMan Option) the messages will pop up allowing access to order parts send repair info to the arrival station while the aircraft is in flight. The LAT/LON of the aircraft also used to show on the screen and on the AirMan option you could view a realtime globe of your fleet
This is very important. So, from your expertise, Behavior of ACARs transmissions is largely customer (airline) specific. Most airlines would avoid exclusive SAT transmissions unless they like big monthly bills. But in the mid-Atlantic, after the MU (or it descendent) gets tired of trying VHF (out of range) and then maybe HF, THEN it would reference it's spacecraft almanac and drive the Sat antenna to the GEOstationary sky coordinates and attempt to blow the whole message up at once. Right? Without a sucessful response from the Satellite, it will start over and attempt repeated interigations of the spacecraft, until it gets a response.

This is important because, if it is true (and I'm taking it on rumour that those coordinates were part of the message at 0214z), this means that the IRU portion of at least one of the ADIRU's was functional.

Why is this important, you ask?

Because if the crew had an IRU platform at 0214z, (and they had to for the ACARs to broadcast it's position to the Satellite), then they likely had Attitude information available to them.

This strongly suggests to me now, that the airplane was wings level at 0214z completely intact and flyable in Alternate Law with attitude information available. (This does not mean, by any means, that any pilot could have kept it right side up in that kind of weather system.)

CC

Last edited by Captain-Crunch; 11th Jun 2009 at 01:06. Reason: poor spelling
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Old 11th Jun 2009, 01:00
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Ladies and Gentlemen . . .

Most of the speculation here -- including many of the "informed" comments of professionals -- is simply "by guess and by golly" based on everything from google to gut feeling to real-life experience. At this stage even most of the best informed and best intentioned of posts should be treated the same as the genre we now call "creative non-fiction". In no case should anyone assume that what we have learned so far points with any degree of accuracy to the "cause" of this tragedy.

The best that we can hope for is that the recorders will be located, the data decoded, an informed report issued, and aviation safety thus further enhanced. I for one have a high degree of optimism that these things will occur in this instance.

Grizzled
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Old 11th Jun 2009, 01:15
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Originally Posted by Captain-Crunch
Without a sucessful response from the Satellite, it will start over and attempt repeated interigations of the spacecraft, until it gets a response.
If I remember correctly, the aircraft isn't supposed to send anything unless it can sync to transmissions from the satellite at the correct frequency: in fact, I don't think it can since it won't know the correct timebase for the channel.

So I agree: the fact that it was transmitting implies that the aircraft had some kind of location and orientation information (I presume the beam steering unit gets that from the same system the crew would) and wasn't so unstable that the antenna couldn't lock to the satellite within the transmission tolerance.
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Old 11th Jun 2009, 02:30
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MG23 points on Sat Trans

MG23:
If I remember correctly, the aircraft isn't supposed to send anything unless it can sync to transmissions from the satellite at the correct frequency: in fact, I don't think it can since it won't know the correct timebase for the channel.

So I agree: the fact that it was transmitting implies that the aircraft had some kind of location and orientation information (I presume the beam steering unit gets that from the same system the crew would) and wasn't so unstable that the antenna couldn't lock to the satellite within the transmission tolerance.
Thanks MG23 for the Sat correction. It must "see" a lock, then before transmission of data. (Man these techs are great.) (thanks also Grdbrk and others)

And apparently the vender is SITA not ACARs from ARINC like we are used to in the states? But it does essencially the same thing. I could only find this 1973 description of the SITA transmission times:

7.3 Response Time

The average response time for Type A messages, i.e. the time lapse between the Instant an operator presses the transmit key of his terminal to send his query and the instant the first character of the reply appears on the screen (see Figure 6) ranges from 1.4 seconds to 3 seconds, depending on the number of links involved in route. A typical response time distribution is shown in figure 9.

7.4 Satellite Processors

The downtime of SPs is around 16 hours per month including scheduled and unscheduled stops (e.g. preventive maintenance, configuration changes, etc.)

Presently, certain SPs switch up to 6 message blocks per second during peak conditions of traffic.

Switching times are in the order of 5 ms per block for both systems.


So the SITA/ACARS transmission is instant, once it gets a lock.

SITA NETWORK by Chretien, Konig & Rech
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Old 11th Jun 2009, 03:00
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vapilot said:
Much earlier in this thread I have with the help of a retired A330 engineer posted the following decoded maintenance computer ACARS messages:

The PFD flag at 210Z was an "airspeed limit" warning (error code 2283)

The PFD flag at 211Z was a "flight path vector" warning (error code 3412)

The above from my post 6 Jun here.

Two more required expert interpretation as they can have multiple meanings:

The Rudder TRV Lim Fault at 210Z (code 2723) is a reported fault by the flight control primary/secondary computers and is probably related to the loss of ADIRU air data. This is not solid, but likely and is also a known and expected fault message as any other failure of the rudder limiter would have been followed by additional failure or warning messages.

I have mentioned this before on this thread and discounted "Daryl's" Honeywell 'expert' interpretation of this message.

The 214Z advisory warning (code 2131) could have been one of the following:

Cabin Vertical Speed, Cabin Altitude, Differential Pressure or cabin pressure controller data loss (lack of pressure info, TAT or mach data from the ADIRUs). When there is a loss of ADIRU air data, the cabin pressure controllers will pass the same code without extensions. The first two advisory messages (vs and Cab Alt) would be accompanied by other faults so this is most likely to have been a warning about the Delta P (descent rate being too high) or a general cabin pressure controller fault. Again not solid, but the last two ACARS received code interpretations are the most likely scenarios.
Great analysis. I'd really like to know if the SITA(acars) system "ADVISORY" is a really a warning. If it is a repeater of info on ECAM, most of these messages would be low-level Amber advisories. This means RED warnings like "CAB Altitude" could be ruled out. We need a SITA French mechanic to answer this for us. Can one of our French speaking guys copy this question to the french forum?

Cheers,

CC

Last edited by Captain-Crunch; 11th Jun 2009 at 06:03. Reason: deleted error about the toilets, vapilot was right
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Old 11th Jun 2009, 03:01
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Grounded101;
In structured problem solving you don't discard data at this earliest step in the process, any theory can be constructed, theories are not discarded at this stage, no matter how improbable, as it is too early to attempt to reach a conclusion
- Specific knowledge and experience of a situation often constrains thinking
There are a lot of highly-experienced, skilled people contributing here including accident investigators, trained human factors people, flight data people, systems engineers & analysts, manufacturers and even a few who actually have designed the systems now under present discussion and who have examined this and all the other ACARS messages. This much is a given.

While at this point much more is possible in terms of explanations than that which may reasonably be ruled out, we know that the VSC (Lav) message bears no import or even a hint at what went wrong. Many of us know this airplane well - the "LAV" acars message is a common maintenance message, occuring on practically every flight for some unknown (to us) reason. It shows up on practically every post-flight ACARS/AIMS Report along with a few other Class II (non-flight crew) messages.

While it applies to this flight, this system and this message indicate nothing untoward with regard to pressure bulkheads, tail-issues, impending failures, etc etc etc. This has been stated a number of times in this and the first thread.

While almost all would agree with the statement regarding improbability, early conclusions and dismissable evidence early on, (because these investigation fundamentals are well understood by many, though clearly not all, here - (not referring to you specifically), let me turn your point around and ask the question, what do you do with items/facts that are both well-understood and known to be irrelevant? At what point does one dismiss factors? I suggest that point was reached with this message a very long time ago, and reasonably so.

The nature and cause of the "lav" message is known as is the system. If we are, after more than a week of thrashing about, to take the position that all is admissable, then we'll be swatting flies for another few thousand posts, while the investigators, even without the recorders, will have ruled out some fundamentals.

I intend this to be respectfully helpful to you and to anyone who may believe that individual threads make an entire suit. I am trying to educate generally; No one is exploring the possibility, given all else before us.

Further....
We don't even know if the ACARS messages are in the correct order. BITE (built in test equipment) within the system controllers may have delayed a fault message while internal system self-testing was going on, only to latch to the fault/failed mode after other, more swiftfly-reporting systems have been captured by the ACARS. This is a maintenance system and not a flight data tool, after all.

It still cannot be said if the ultimate reason(s) will be complex as in the Pitot-TAT/warm air followed by a loss of control theory, or straightforward as in "they flew into a thunderstorm and broke up" theory.

respectfully,

PJ2

CC, vapilot - here are the 24 failure flags which may show up on the PFD:




1. ATT flag (red)
If the PFD loses all attitude data, its entire sphere is cleared to display the ATT flag.
2. CHECK ATT or CHECK PFD or CHECK PFD1 (or 2) flag (amber)
“CHECK ATT” appears when there is a disagreement (of a least 5°) in the attitude information
displayed by the two PFDs. The CHECK ATT flag appears on both PFDs, and a caution appears on
the ECAM.
“CHECK PFD” appears when the DMC detects a disagreement between the two PFDs. The CHECK
PFD flag appears on both PFDs.
“CHECK PFD 1(2)” appears when the DMC detects a disagreement between its own computation and
its displayed information. The CHECK PFD 1(2) flag appears on the relevant PFD.
3. SI flag (red)
If the sideslip information is lost, the index disappears and a red SI flag appears.
4. FPV flag (red)
In TRK FPA mode, when the drift angle or flight path angle is not valid, an FPV flag appears.
5. FD flag (red)
If both FMGCs fail, or if both FDs are disengaged and the FD pushbutton is on and the attitude is valid,
a red FD flag appears.
6. SPD flag (red)
If speed information fails, a SPD flag replaces the speed scale.
7. SPD SEL flag (red)
If selected speed information fails, a SPD SEL flag appears.
8. SPD LIM flag (red)
This flag appears when both FMGCs (flight envelope part) are inoperative, or in case of SFCC dual
flap/slat channel failure.
In this case, the following PFD information is lost : VLS, S, F, Green Dot, Vtrend,
Vmax, VFE next, VSW.
In case only Vmax or VLS is lost, the flag comes up on the PFD but the remaining valid information
still appears.
9. V1 INOP flag (red)
When the V1 signal is not valid, a V1 INOP flag replaces the digital value.
10. ALT flag (red)
If the altitude information fails, the ALT flag replaces the altitude scale.
11. CHECK ALT flag (amber)
The CHECK ALT flag appears, as does an ECAM caution, if the disagree between the two PFDs
altitude indications is greater than 250 feet when QNH is selected, or 500 feet when STD is selected.
The caution and the flag disappear, when the pilot's and the copilot's barometer references disagree.
12. ALT SEL flag (red)
If the selected altitude information fails, an ALT SEL flag appears.
13. V/S flag (red)
If the vertical speed information fails, the V/S flag replaces the vertical speed scale.
14. LOC and G/S flags (red)
If the localizer or glideslope receiver fails, a LOC or G/S flag appears on the deviation scale.
15. V/DEV flag (red)
If the vertical deviation information fails and the LS pushbutton is not pressed, a V/DEV flag replaces
the V/DEV scale.
16. RA flag (red)
If both radio altimeters fail, this flag appears in place of the radio height indication when the aircraft
altitude is below the transition altitude. The ground reference indication (red ribbon) will disappear.
17. DH flag (amber)
A DH flag appears, when the aircraft reaches the selected DH.
18. HDG flag (red)
If the heading information fails, the HDG flag replaces the heading scale.
19. CHECK HDG flag (amber)
The CHECK HDG flag appears, as does an ECAM caution, if there is a discrepancy (5°) between
pilots's and copilot's heading indications.
20. MACH flag (red)
This flag appears, if the Mach data fails.
21. V/DEV (amber)
At the top of the glide scale, this message flashes when in approach phase and, either FINAL mode
is armed/engaged, or a non-LS approach has been selected, and the LS pushbutton is selected.
22. WINDSHEAR (red) or W/S AHEAD (red or amber) warnings
WINDSHEAR : Reactive windshear warning. Displayed, when the FMGC
detects windshear.
Refer to 2.22.40.
W/S AHEAD : Predictive windshear warning. Displayed, when a windshear alert is generated by the predictive windshear system. Refer to 2.34.60.
Note : 1. All flags except SI, V1 INOP, DME 1 (which are steady) flash for 9 seconds then are steady. DH flag flashes for 3 seconds then is steady.2. For TCAS, Refer to 2.34.80.
23. DME 1 flag (red)
When DME distance is not available, a DME 1 (on PFD 1) or DME 2 (on PFD 2) replaces the DME
distance indication.
24. ILS flag (red)
If an ILS frequency is not available, or if either the LOC or G/S signals fail, an ILS flag replaces the
ILS frequency indication.
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Old 11th Jun 2009, 03:25
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Air France hits bad weather

Tonight, French TV TF1 has broadcasted a testimony from a Air France maintenance manager explaining that the pitot tubes issue was well known at Air France and shown internal documents stating that several critical problems has already occurred on AF CDG-NY as well as AF CDG-TOKYO
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Old 11th Jun 2009, 03:31
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Boac, yes, well in that case, only these two:

The PFD flag at 210Z was an "airspeed limit" warning (error code 2283)

The PFD flag at 211Z was a "flight path vector" warning (error code 3412)

fell into the definite bin.

These results were passed along via an exchange of emails so I will try a prearranged phone conversation to see what else can be made more solid in the list.
On the "prototype airliner", the A300, Flight Path Vector, is a PFD presentation that can be selected on the glaresheild to predict on the Attitude Display where the mass of the airplane is going to wind up. You "Fly the Bird" target and it helps you manage energy. I know it would likely be a cascading failure from either the AIDRU, airspeed data loss, or the IRU portion itself. Is the A330 the same?

(A330/340 drivers are amazingly silent today...)
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