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AF 447 Thread No. 7

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AF 447 Thread No. 7

Old 31st Mar 2012, 19:34
  #1141 (permalink)  
 
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From PJ2 Describing SIM, 447 profile, STALL

"The overriding impression of these sessions was how quickly things occurred and how fast was the altitude loss."

If RHS could have been debriefed, would he have stated something similar?

Substituting "GAIN" (altitude) for "Loss?"

DOZY, I refer to SELECT, not MANAGED. I have a further question, but probably for an engineer. What is the damping for a 5k fpm ascent/descent? Is the bellcrank, A/Rod protected from sequential deflections, followed by a withdrawal of input? Are the inputs density compensated? I am sure they are. Having seen the deflections of a preflight Stabilator check on F-16, they are emphatic, to say the least.

Another thought. Could the .5 second cycle .1g amplitude "vibration" have been a stammering elevator select? OR THS stutter? Just a mechanical question, nothing more.
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Old 31st Mar 2012, 19:42
  #1142 (permalink)  
 
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Lyman - read what I'm saying. In MANAGED mode, the corrections applied by the autoflight system are displayed in the SELECT window of the FCU panel. I want to make clear at this point that we're not talking about control inputs of a magnitude to effect 5000fpm descent rate immediately, simply that this is the value the software uses in certain configurations. Lower to the ground, you'll see -1500 appear in the window for a split second as corrections are applied, but you don't start descending at 1500fpm.
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Old 31st Mar 2012, 20:04
  #1143 (permalink)  
 
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Not surprised we are not communicating well. You haven't touched on my question. Perhaps let's just give this dialogue a rest. I'll just read. You're the Pilot rep.
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Old 31st Mar 2012, 20:45
  #1144 (permalink)  
 
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Originally Posted by Lyman
Could the .5 second cycle .1g amplitude "vibration" have been a stammering elevator select? OR THS stutter? Just a mechanical question, nothing more.
The buffet onset envelope is determined in flight test before the type is released into service. It is scheduled in the AFM, the FCOM, the QRH and in the FMEGC. Stall warning is set to occur at an AoA 1 degree less than buffet onset. The recorded 'signature' matches that previously obtained in flight tests. Why would the elevator begin to stammer and/or the THS stutter at the precise moment that the airplane enters a regime where buffet is known to occur?
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Old 31st Mar 2012, 21:26
  #1145 (permalink)  
 
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Fault Tolerance, Graceful Degradation, Redundance and SURVIVABILITY

Hi,

Before the day the Systems becomes PERFECT and EVERY possible situation is simulated and TESTED, as a designer i would prefer to deliver planes with "small resources" (like AoA) capable to save POB.

gums:

But when the system starts to revert to backup modes, then the thing might be the best friend you have, especially for a pitot-static problem.







Mac

PS

Is seems something like the AoA indicator (proven in EXTREME conditions) lies in the "Tectonic Fault" dividing who:

1) Think a System (and the crew) is capable to work always as expected.

2) Known (battle hardened) that sometimes you must be able to do the "necessary" to survive.


Airbus SAS or Air France or authorities (or AF447 crew) made what was possible:

1) Maintained hundreds of A/C relying on OBSOLETE AS sensors

2) Didn't replace the WORSE obsolete sensors in time

3) Didn't anticipate possible PROBABLE ("recurrent") scenarios.

4) Didn't act with it's authority capabilities

5) Didn't even understand what "was happening" yet before entering WX

Perception "means" survivability:

Thousands of professionals IMO didn't act proactively.

And Murphy Law again put the toll for that collective failure (merely a probability result).

PS

Well, if AoA gauge has no place in the cockpit at least his data could be used to "inform" the stall type.

Last edited by RR_NDB; 31st Mar 2012 at 21:29. Reason: Text impvmt
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Old 31st Mar 2012, 21:54
  #1146 (permalink)  
 
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@HazelNuts39
"vibrations that might correspond to buffeting"
I agree with that, and I should have written before the wine glass was empty! Possibly the point I was trying to make, was that the onset of the 5Hz 0.6g (p/p) at cockpit vibrations occurred as the 0.2Hz oscillation of the pitch attitude and AoA commenced. The amplitude of this "buffeting" has risen in tandem with the increasing amplitude of the 0.2Hz longitudinal pitch/AoA oscillation.

I wonder if PJ2 noted anything similar in the SIM? Possibly not, as that aspect of the airframe dynamics was then outside the known flight envelope.
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Old 31st Mar 2012, 21:59
  #1147 (permalink)  
 
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Snoop

@PJ2
Originally Posted by PJ2
I'm not sure what you mean by "effective aircraft
This excellent 1997 book that Machinbird advised me, shows 51 references of "Effective aircraft" to explicite the definition: Aviation safety and pilot control: understanding and preventing unfavorable Pilot-Vehicle Interactions isbn=0309056888...National Research Council (U.S.). Committee on the Effects of Aircraft-Pilot Coupling on Flight Safety - 1997 - Transportation - 208 pages
Implications for Design of the Effective Aircraft Dynamics Reduce time lags in the high-frequency effective aircraft dynamics. To reduce tendencies for ...

Originally Posted by PJ2
](no) unusual difficulties which require [...] (particular) skill or knowledge
These characteristics are required for certification, but have nothing to do with system "controllability"
Originally Posted by PJ2
eminently, (éminemment), "observable and controllable"
Observability and controllability don't have to be eminent, they just are mathematic.
Originally Posted by PJ2
Nor do the accident rates indicate a large difference between aircraft types
I assume you refer to A/B ? I have no royalties in any, nor in other manufacturer, nor in any insurance/aircraft financer. I am only involved in flying pleasure, pilot safety, and mathematic accuracy.
Originally Posted by PJ2
However, no aircraft, no design I know of is controllable or observable when it is taken into a full stall.
False :
1. In any pilot school over the world, stall is teached to get private pilot. Would this manoeuver be uncontrollable and the international civil aviation allow that ?
2. AF447's A330 finally seems to stall like many others aircrafts stalled : you just have to push to stop the stall .Gums quoted F-102, Concorde, Viper having analog stalls.Yourself said it is the case also with B777 and A330 D-sim. Is that uncontrollable if the pilot learned that ?
3.The french pilot school where Air France teached his young pilots (perhaps Bonin), IAAG/EPAG uses for VFR and IR learning the Socata TB20 Trinidad. This aircraft stalls in just descending, unstalls just with pushing... Would this manoeuver be uncontrollable and the french civil aviation allow that if it was ?
4. All the aerobatic pilots, including fight pilots regularly stall and spin, controlling perfectly their flights.. We like to look them and we could not imagine one second their flight is not controllable. Are they ? 
Originally Posted by PJ2
AF447 was recoverable even after entry into the stall but it required that the stick be pushed fully forward and held there until the wing began flying again. That would take between 15,000 and 22,000ft (I've flown this in the sim many times). This is Machinbird's "unloading of the wing" to which he referred some pages back.

Originally Posted by Machinbird
And Presto! we have some numbers and they show that

Originally Posted by Machinbird
If you do not mess it up you would do surprisingly well

Originally Posted by HN39
The "on the threshold of stall warning" trajectory with specific excess thrust (T-D)/W = 0.15 results in level off after 15 s (was 18s) at FL76, Mach 0.51, 295 kCAS, az=2,24 g.

The final loss of height is not your 22000 FT, nor FL200, nor 15000 FT,
but 5000 (max) +(FL100-FL76)=7400 FT
Originally Posted by PJ2
Said another way, a B777 pulled up in the same manner and handled the same way as this aircraft was would also crash

Are the B, C, D, etc pilots hammered with "B, C, D, etc. can't stall" ?
Originally Posted by PJ2
sidestick vs control column

Both may be tried, used. if correct. The problem of observability, governabillity, man-machine interface is not which actuator, but how it is connected to the effective system. I have no royalties in any manufacturer, and I choose to put philosophy in library not in aircraft.
Originally Posted by PJ2
This is the part that is very definitely not complicated

Originally Posted by TurbineD
However, it is more complicated when you can't interview a key person in the problem loop. When this happen, you have to make a list and go through the process

Originally Posted by PJ2
In the present system, 99.9% of flights work well with SOPs, CRM, appropriate use of automation (according to enlightened airline policies which permit hand-flying), but the loss of such skills is nevertheless no longer a blip but a trend
.


That is very dangerous ! Every sixty seven hours you have a four minutes crash ! I choose to fly with "these guys [...] (who) knew how to stay alive, (many of them are here, thank you !) and not in your "managed airlines" and their effective aircraft.

roulishollandais

Last edited by roulishollandais; 31st Mar 2012 at 22:10. Reason: BB-code
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Old 31st Mar 2012, 22:11
  #1148 (permalink)  
 
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Originally posted by roulishollandais ...
That is very dangerous ! Every sixty seven hours you have a four minutes crash !

Now, now, now ...

PJ2 forgot to hold the "9" key down after the decimal point, but I doubt he would forget to push the stick forward.
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Old 31st Mar 2012, 22:37
  #1149 (permalink)  
 
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So what I'm looking to eliminate is the zipper as Alpha Prot, considering there was turbulence, UAS, and an actual SW for the Pilot flying. His input did not have time to actually change the AoA, so I'd be looking for some combination of local W/S to duff the AoA vanes. Since STALLWARN is available in ALTLAW2, it wouldn't make any difference whether in autoflight or manual.

just askin'

Whether the Law degrade was due imminent STALL (actual or AoA A/S sensed) or UAS, or computer malfunction, would it be important to know what ND value would obtain given autoflight's need to correct, WARN? Would it be 5000fpm/ND?

Because that would be almost like foul play, eh? "We're about to STALL, Your Aircraft"........."Oh, and LAW CHANGE"........"SeeYa".........
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Old 31st Mar 2012, 22:41
  #1150 (permalink)  
 
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A-330 Instructor Manual

MM43, thank you for providing this valuable link to the manual. Very interesting. I used to have the 320 version but no longer do.
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Old 31st Mar 2012, 22:52
  #1151 (permalink)  
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Hello Lyman;

In re the autopilot disconnect and, "It was difficult. " (post #1124)

No, it was not. And a disconnect is most certainly not like "hovering a Harrier".

An autopilot disconnect is a non-event.

If the airplane is descending/ascending slightly when the disconnect occurs, a gentle nudge on the stick (millimeters in terms of movement of the top of the stick) brings the airplane back within the expected requirement, which here is maintaining a cruise altitude.

A disconnect simply is unimportant to a pilot - and absolutely should be a non-event. One takes over, commands the airplane and makes it do what you want, returns it to what you were doing before the disconnect, and when available, re-engages the autoflight system. It's what we do.

The terms "Select" and "Managed" have specific meaning for Airbus pilots. They refer to an autoflight mode where control of the aircraft is either through the MCP (Mode Control Panel - autopilot panel) or the FMGC.

When the AP disconnects and there is a rate of climb or descent occuring, (including a small deviation such as occurred here), the vertical speed window will display VS (as opposed to other modes such as FPA or just dashes in "managed" mode). In other words, the display defaults to VS and will show what the rate was at disconnection but isn't a "command"...it's just information at that stage.

In terms of response, no pilot is going to slavishly follow an FD command to "descend at 5000fpm" because a flight director says so. He is instead going to "look through" the temporary FD "command" and get his airplane gently back to cruise or whatever it was doing prior to the disconnect and get on with the drills/checklists. No big thing. Really.

Hello, Machinbird;

I do appreciate your comments and the fact that you present such a different view of 'the wing' than I have as a transport pilot - it is very engaging and well worth the discussion, thank you.

Re, "The natural place to be using AOA is on approach."

I like knowing and using AoA. I used to interrogate the ACMS Alpha Parameter functions on the ACARS units all the time and keep the AoA displayed down on the pedestal especially during heavy turbulence. So it can be done (though it isn't taught!), and likely easily with software and pixels (rather, raster scan!).

So I do not argue against an AoA presentation to the pilots...I like it and agree that training on it would be straightforward in terms of the mechanics of learning and applying the information. I am not personally arguing against it but I'm recognizing some of the impediments to making the change and the likelihood of such change in the face of certification regs, training/standards/checking and the like. Airline budgets are thinner than they ever were and "safety as a business case" is not an atypical approach, it is THE way it is done. Agree or not, cost and cost control are enormous factors in daily operations.

The one argument which I think may be convincing is in knowing that one was stalled but the counter-argument is, the blaring "Stall, Stall" and loud warning chirp didn't get their attention...would AoA have? What else does a pilot need to tell them their aircraft is stalled?

The industry has been largely successful without AoA so the argument that AoA would have "saved" AF447 vice other standard handling procedures (not stalling, pushing the nose down once stalled), is not convincing. It wouldn't have saved Colgan, it may have saved the Airborne Express DC8, it may have saved the FedEx ATR72 at Lubbock and (IIRC) a B727 where the pitot heat was turned off, but in the millions and millions of hours flown in all types, lack of AoA has not been an issue until AF447.

So the argument must demonstrate that an AoA indication would have made a difference to the outcome, for this crew and while it may have, we just don't know. The captain may have noticed from his vantage point and called out "push down!"...we don't know. I agree that one accident prevented makes such change highly desirable but again, what shall we argue next? I absolutely know through data that there are some things that can be done right now that would prevent CFIT and overrun accidents in the approach and landing phase but short of exorting the stabilized approach, very little is left up to technology and presented information.

But we could have an electronic "energy-status bar"...showing the potential landing distance, even on contaminated runways as a digital presentation relative to the aircraft's energy level on the approach.

Now that kind of presentation would be used thousands and thousands of times because that is the number of non-stabilized approaches that are occurring in airlines' FOQA data.

The argument for AoA is not "natural" but is nevertheless a good one...the more info the better, but it comes with much more than just putting in the guage and both manufacturers and airlines are going to look at the cost.

It is the way this business is done, much to my (and most others who work in it) frustrations.

My comment about "how quickly things unfold" is an observation on the amount of time it took to lose control. Time is always "relative to perception and familiarity". When a pilot is highly trained, highly experienced and very familiar with his/her airplane, the flow of even huge amounts of information and lots of events flow much more slowly, perceptually, because the mind anticipates much more effectively and easily, (depending upon other factors such as distraction, fatigue) than if one is relatively inexperienced in such circumstances.

In terms of this loss of control, while it unfolded literally over a period of about 40 seconds, oddly that is tons of time to do something, but it is not a lot of time for assessment, discussion, action.

This is a really important point: Most things that happen in an aircraft that cause trouble or an accident take a few seconds and one has a bit longer for response. This is what training (and training and training) is for - to reduce the time needed to assess accurately and respond. The response to the UAS was instantaneous without, in my view, good reason to do so and without the requisite crew coordination. One simply never does that in a transport aircraft, period, unless it is a TCAS, GPWS warning. The SOP is, first establish control of the flight path, (in other words, don't give up a stable flight path for one that is unpredictable, uncertain, unannounced and unplanned); once control is assurred, call for the drills and/or checklists, all the while keeping a very close eye on the aircraft.

By the time the aircraft had stalled, they had backed themselves into such a corner of confusion that there were no breadcrumbs to get back to stable flight because they completely lost situational awareness even though the nose was pointed up, the stick was full back and the altimeter was unwinding at about a thousand feet every three seconds.

PJ2

Last edited by PJ2; 31st Mar 2012 at 23:20.
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Old 31st Mar 2012, 22:59
  #1152 (permalink)  
 
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thermostat

Thanks for reminding me about the A330 Instructors Support Manual link.
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Old 31st Mar 2012, 23:03
  #1153 (permalink)  
 
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Man machine interface

Hi,

DozyWannabe:


the aircraft's systems told them that they were approaching stall
What type of Stall?

and continued to warn them as they went into the stall regime itself.
SW was presented several times erratically, not adequately processed by the System.

It warned them that they were in Alternate Law 2 without protections.
Ok

The ADI told them that they were too nose-high
Ok

the speed indications (when they came back) indicated they were too slow
Faulted at critical moments
and the altimeter was unwinding at an alarming rate
After FUBAR "threshold"

IMO, the A/C (it's man machine interface) could (may be, should):

1) Provide an "immediate"* information (aural, whatever) to inform origin of trigger problem (actually a "frequent" and recurrent problem). It would have helped.

2) Protect* (limiting to REC MAX FL) from zoom climbing to the "corner" entering "the coffin" .It could have helped.

3) Provide* information on "dangerous trend" like AoA increasing at such rate. It could have (redundantly) alerted PM on PF "fatal" persistent NU.

4) Better Stall (characteristics) indication. Technically feasible. It could have "helped".

5) More elaborated Aural and Visual information to help "HF aspects" during "crisis". It could have increased their chances reducing confusion, stress, etc.

In this specific point we may mention: Antoine de Saint Exupéry's "It seems that perfection is reached not when there is nothing left to add, but when there is nothing left to take away"

Probably something that can be applied during extreme conditions in many designs.

Mac

PS

Man machine interface designers would have an opportunity after the results of the HF study of AF447.

(*) Cost: "near zero"

Last edited by RR_NDB; 31st Mar 2012 at 23:37.
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Old 31st Mar 2012, 23:16
  #1154 (permalink)  
 
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Temporary LOC of China 006

Hi,

Just remembering:

The "unprotected" B747SP AVERAGED ROD of 30,000 during 20 seconds.

They experienced as much as 5g. And practically lost left horizontal stabilizer / actuator.



Mac
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Old 31st Mar 2012, 23:24
  #1155 (permalink)  
 
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Dallas to Denver

Hi,

gums:

Why not use your car? Just 800 sm.

Mac

PS

My longest leg (in a Winnebago) was 1000 miles. By car is a lot easier.

Last edited by RR_NDB; 31st Mar 2012 at 23:38.
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Old 31st Mar 2012, 23:50
  #1156 (permalink)  
 
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Snoop 99.9% or 99.99% ?

Originally Posted by PJ2
In the present system, 99.9% of flights work well with SOPs, CRM, appropriate use of automation (according to enlightened airline policies which permit hand-flying), but the loss of such skills is nevertheless no longer a blip but a trend


Originally Posted by roulishollandais
That is very dangerous ! Every sixty seven hours you have a four minutes crash ! I choose to fly with "these guys [...] (who) knew how to stay alive, (many of them are here, thank you !) and not in your "managed airlines" and their effective aircraft.
roulishollandais
Originally Posted by mm43
Originally posted by roulishollandais ...
That is very dangerous ! Every sixty seven hours you have a four minutes crash !
Now, now, now ...

PJ2 forgot to hold the "9" key down after the decimal point, but I doubt he would forget to push the stick forward.

@mm43:
it is still very dangerous if PJ2 did forget a final "9" , and we replace thanks to your intervention, mm43, 99.9% by 99.99% : 1/10 000 means my children would have every 667 hours a 4 minutes crash
Would you accept that mm43 ? no, no, no ...

And PJ2 would need 22 000 FT (or 35 000 ?) to push and recover, instead of 7 400 FT !!! no, no, no ...

roulishollandais

Last edited by roulishollandais; 31st Mar 2012 at 23:55. Reason: add : height of loss
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Old 1st Apr 2012, 00:08
  #1157 (permalink)  
 
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Cool

Hi,

PJ2
The industry has been largely successful without AoA so the argument that AoA would have "saved" AF447 vice other standard handling procedures (not stalling, pushing the nose down once stalled), is not convincing. It wouldn't have saved Colgan, it may have saved the Airborne Express DC8, it may have saved the FedEx ATR72 at Lubbock and (IIRC) a B727 where the pitot heat was turned off, but in the millions and millions of hours flown in all types, lack of AoA has not been an issue until AF447.
but in the millions and millions of hours flown in all types, lack of AoA has not been an issue until AF447
Indeed .. millions of flight hours and not get in trouble ...
This is always the case .. until there is a trouble ...
The cargo door locks of Boeing B747 .. millions of flight hours and not get in trouble .. until a door opened in flight and passengers ejected ...
Same plane type ... explosion .. cause problems in fuel tank
The B737 ... millions of flight hours .. until the rudder jammed ....
And in fact all the improvements of flight safety has always risen from the
similarly
Millions of flight hours with no problems .. and then .. suddenly the "apocalypse" and the eternal question:
Why ?
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Old 1st Apr 2012, 00:14
  #1158 (permalink)  
 
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As an Anthropologist, jcjeant, I say without fear of contradiction, that in my experience, Man is the only sentient being who predictably misses that which is obvious.

and, sadly, sometimes deliberately.
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Old 1st Apr 2012, 00:18
  #1159 (permalink)  
PJ2
 
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roulishollandais;

You say, "And PJ2 would need 22 000 FT (or 35 000 ?) to push and recover, instead of 7 400 FT !!! no, no, no ..."

Sorry, where did you get 7 400ft from?

PJ2
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Old 1st Apr 2012, 00:41
  #1160 (permalink)  
 
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Why?

Hi,

jcjeant:

Why ?

In all 3 cases you mentioned there was "tangible" failures, even on TWA800.

Now, if HF have to explain the crash we may say the causes are getting more "intangible"

Since the beginning BEA told the equipt. worked as designed.

,

Mac
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