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Why did Air France 447 go down?


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Boester, that being said does that mean they did not know how to use wxRadar ?

I would think that seeing tstorms at 35+ thousand feet means they are large (and scary) storms and A significant diversion is needed...yes no?

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There was a program on the CBC last night about "Why Did 447 Crash" While interesting the information now known on the CVR and FDR is missing and some of the inferences seem to be at odds with the interim report. However one thing that seemed plausable for thier entry into the storm was that the weather radar may have been returning hits from a much smaller cell directly in their path towards the 250 mile wide 50k feet high major cell. This would in effect block their "sight" of the larger cell until they had passed through the smaller cell and at that point it would be too late to turn around without entering the cell anyway.

I had never though of this before but the smaller cell would have been like trying to see through a wall since the raday will only return the closest water.

From the satellite photos I remember the aircraft entered a massive area of thunderstorms so I don't really think the crew would have believed there was simply one small storm ahead of them, or they shouldn't have believed that anyway. I think the "RADAR shadow" trap that you are describing tends to only be an issue when you are in the terminal area with the range cranked down and are maneuvering on different headings where you can't mentally track the big picture. When approaching a large area of weather it's unlikely that a pilot would assume there is nothing behind the smallish cell in front of them.

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Hey Don't shoot the messenger. It was what was stated and demonstrated by investigators on the show. I never made any comments that they didnt know how to use it or anything else. simply that there is a possibility that the shadow mislead them into thinking a small diversion (12deg I believe) was all that was necessary when in fact the 250 mile wide storm would have required a significantly larger diversion but they simply did not see it in time.

just restating the opinion of the show.

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Boestar;

Sorry, wasn't clear in my post that I was disagreeing with the conclusion in the show and not that I assumed it was your conclusion.

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From the satellite photos I remember the aircraft entered a massive area of thunderstorms so I don't really think the crew would have believed there was simply one small storm ahead of them, or they shouldn't have believed that anyway. I think the "RADAR shadow" trap that you are describing tends to only be an issue when you are in the terminal area with the range cranked down and are maneuvering on different headings where you can't mentally track the big picture. When approaching a large area of weather it's unlikely that a pilot would assume there is nothing behind the smallish cell in front of them.

Two big assumptions here. One, that the operating F/O's had detailed knowledge and a lot of experience in severe weather, ITCZ weather in particular; and Two, they did in fact use the full capabilities of the onboard weather radar, understood its limitations and had a darkened flight deck in order to get as much a visual picture of the track ahead as possible. Full moon or no moon, when lightning occurs, it outlines cell formations and can help immensely with the big picture.

All of which is a side issue to whether they were made aware, either by listening watch or via queries to the Oceanic control about diversion activities of aircraft ahead.

There is still so much unknown about this horrible event. I still can't bring myself to calling it an accident.

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http://www.flightglobal.com/articles/2011/05/28/357321/revised-stall-procedures-centre-on-angle-of-attack-not.html

Revised stall procedures centre on angle-of-attack not power By David Kaminski-Morrow

Investigators have been left attempting to explain why the crew of Air France flight AF447 failed to recover the Airbus A330 from a high-altitude stall, a predicament which has been the subject of a recent revision of safety procedures.

The revision concentrates on placing greater emphasis on reducing excessive angle of attack - the critical characteristic of a stall - rather than the classical approach of training pilots to power their way out of a near-stall with minimum loss of altitude.

A formal document detailing the rationale for the revision points out: "There have been numerous situations where flight crews did not prioritise [nose-down pitch control] and instead prioritised power and maintaining altitude."

Operational experience has shown that fixating on altitude, rather than the crucial angle of attack, can result in an aircraft stalling.

French investigation agency Bureau d'Enquetes et d'Analyses has disclosed that the crew of AF447 maintained nose-up input despite the onset of a stall, but has yet to determine the reason or reach any conclusions.

After receiving a stall warning AF447's crew set the A330's thrust to take-off/go-around power, in line with Air France's standard operating procedure at the time. The procedure also required the crew to reduce pitch attitude, roll the wings level and ensure the speedbrake was retracted.

The revised recovery procedure was agreed between the major airframers, including Airbus and Boeing, some 12 months after the loss of AF447, although a source familiar with the investigation stresses that the change was "not prompted" by the accident.

At the heart of the revision is an acceptance that classical high-power recovery is not appropriate for every stall condition.

Simply applying maximum thrust could be ineffective in reducing the angle of attack and averting a stall, particularly at cruise altitudes where the available thrust would be limited and the engines would require time to spool up.

There is also a risk that the crew might fail to recognise that the aircraft has crossed the threshold from a near-stall into an actual stall, and continue to apply a recovery technique which is no longer effective.

The new procedure is designed to cover all stall conditions. It recognises that recovering the angle of attack might instead require a reduction of thrust, to regain pitch-down authority, as well as a loss of altitude.

It removes the need to prioritise take-off/go-around thrust in favour of restoring lift to the wing by reducing angle of attack. The procedure also points out that thrust should be re-applied smoothly, particularly because aircraft with under-wing engines have a tendency to pitch up, increasing the angle of attack, when power is applied.

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Good grief....DND has been teaching that method for years....

In some cases, one has to assess the situation and perhaps reduce power, push the nose over, get some airspeed and when "out of the stall", add power and "slowly' increase pitch and climb back to altitude.

Unusual atitudes 101

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Just to comment that Airbus had not issued their Revised Stall Procedure at the time of the accident.

And now that I think of it, they aren't/weren't that big on stall training either were they?

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WOW--you guys are tough crowd!!!

So these guys are are in cloud, turbulance, with no reliable airspeed and various aural and visual warnings going off. They enter a stall--BUT--do they believe they are in a stall? If I remember correctly, on the AB in these situation it was not unusual to get an OVERSPEED and a STALL warning at the same time. Now some posters recommend that the the guy unload the airplane with a 90 roll!!!!!!!! I would have a difficult time in believing that most pilots would follow that course when confronted with no airspeed, multiple warning etc etc without even being sure they were in a stall (though it may be correct and is called for in all the training I have been involved in on both AB and Boeing).

The biggest question, in my mind, is why he had a nose up input! AP and AT off with a 2.5 (approx) nose up pitch would have kept them flying level. To maintain full nose up meant he must have been following something--either an indication in the flight deck or a procedure, since it doesn't seem from the record available so far that there was any panic (the pilots even transfer control at one point).

One other point of interest between Airbus and Boeing: if the pilot maintained full nose up the Airbus autotrims (without my books in front of me I cannot recall if it autotrims in ALT law). The Boeing does not autotrim with speed changes. In this situation the Boeing would have column feedback (pulling the column) and might have made a difference!?

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THe Feedback in the stick is artificial. I think thats where he was going. Where as in a 767 for instance the feedback is "real" in that the column force reflects the actual load on the aircraft. Would it have made a difference? Maybe since that is one more input to the brain.

Could it not be that there was a loss of situational awarness at play here. The pilot flying may well have "Felt" the airplane was ina dive when in fact it was stalled and nosed up. I am sure any of the pilot here have experienced this. I know I have.

So here he is getting tossed like a salad in every direction it is very possible that the little gyros in his ears said "Hey buddy you are in a dive" his response could well have been to ignore the visual cues he was gitting and pulling up. not a stretch at all for someone who has not had unusual attitude training or at least not recently. The mind is a powerful thing and if he truly believed he was nose down you would be hard pressed to change his mind.

And before someone asks YES both pilots could have been affected as they were both subjected to the same inputs and their beliefs would have been reinforced by the other pilot.

And before you get all bent out of shape these are merely possibilities and speculation I am not pointing at anyone.

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The pilot flying may well have "Felt" the airplane was ina dive when in fact it was stalled and nosed up. I am sure any of the pilot here have experienced this. I know I have.

So here he is getting tossed like a salad in every direction it is very possible that the little gyros in his ears said "Hey buddy you are in a dive" his response could well have been to ignore the visual cues he was gitting and pulling up. not a stretch at all for someone who has not had unusual attitude training or at least not recently. The mind is a powerful thing and if he truly believed he was nose down you would be hard pressed to change his mind.

Instrument Flying 101, Lesson 1 (usually about 40 hours into PPL training): NEVER TRUST YOUR PHYSICAL REACTIONS; ALWAYS TRUST YOUR INSTRUMENTS. And not just one instrument.

Basic Flying 101, Lesson 1: Attitude + Power = Performance

These two fundamentals should have been their first resort during any disorientation. Not something left to a discussion board such as this. All which leads back to the question of training and experience and what they were doing there in the first place.

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Instrument Flying 101, Lesson 1 (usually about 40 hours into PPL training): NEVER TRUST YOUR PHYSICAL REACTIONS; ALWAYS TRUST YOUR INSTRUMENTS.

You know, somewhere amidst all of the misinformation and disinformation surrounding this tragedy, I was thinking about that.... But then, those poor sods had their instruments lying to them. ... so I think the PF was trying to feel his way out of it, and obviously it didn't work.... At one point, according to the latest from the BEA, he held the stick to the aft and left stops for 30 seconds! ...So I thought, surely when that failed to produce what should be expected, in terms of G forces, and observable roll, ...surely then he must have realized he was in a stalled condition.... but again, that could have just done more to convince him the ship was misbehaving and his instruments were useless to him...

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You know, somewhere amidst all of the misinformation and disinformation surrounding this tragedy, I was thinking about that.... But then, those poor sods had their instruments lying to them. ... so I think the PF was trying to feel his way out of it, and obviously it didn't work.... At one point, according to the latest from the BEA, he held the stick to the aft and left stops for 30 seconds! ...So I thought, surely when that failed to produce what should be expected, in terms of G forces, and observable roll, ...surely then he must have realized he was in a stalled condition.... but again, that could have just done more to convince him the ship was misbehaving and his instruments were useless to him...

The jury is still out on the other instruments, as far as I know. That's why I highlit (highlighted??) the plural version of instrumentS. Regardless, when used in tandem with Rule #2 (A+P=Performance), this tragedy might have been survivable. Emphasis on "might have been." We still don't know if there were any other structural failures making a recovery impossible.

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The jury is still out on the other instruments, as far as I know. That's why I highlit (highlighted??) the plural version of instrumentS. Regardless, when used in tandem with Rule #2 (A+P=Performance), this tragedy might have been survivable. Emphasis on "might have been." We still don't know if there were any other structural failures making a recovery impossible.

Yessir.... still much we don't know....

I have a strong feeling that once all the dust has settled, at least a part of what we'll "learn", is that a multitude of conflicting and concurrent "senses" and indications, combined with their "knowledge" that they were in some potentially ugly weather, all contributed to a total loss of SA.... I think it was almost the "perfect storm" to allow the events that occurred.

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I'm not convinced that the investigators will be able to get a true sense of what the crew might have been "feeling" in the seat of their pants. This is a very difficult scenario to recreate.

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I'm not convinced that the investigators will be able to get a true sense of what the crew might have been "feeling" in the seat of their pants. This is a very difficult scenario to recreate.

Exactly, especially with so much data not yet reported, or even available. Perhaps it's time to revisit a flight deck camera, although I have traditionally been dead set against such an idea. But what price safety?

Now THAT would make an interesting discussion...again!

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Exactly, especially with so much data not yet reported, or even available. Perhaps it's time to revisit a flight deck camera, although I have traditionally been dead set against such an idea. But what price safety?

Now THAT would make an interesting discussion...again!

Ok... I'll bite.

While a FD camera might give us more insight into exactly what happened from a "story" perspective, I'm not convinced that enough more of the scenario would be solved that won't already be prevented in the future with available data. As many of us have seen with LOFT use of cameras in the simulator, it is mostly a picture of the back of two pilots' heads.

Far be it from me, but from an armchair QB's perspective, there are a few causative factors emerging that have nothing to do with what a camera might help resolve, the first of which 4 other flights that same night resolved ... avoid flying through the middle of severe thunderstorms, something which was accomplished by others with relatively minor course deviations.

(Link requires Firefox)

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Stalled AF447 did not switch to abnormal attitude law

http://www.flightglobal.com/articles/2011/06/01/357394/stalled-af447-did-not-switch-to-abnormal-attitude-law.html

Investigation into the accident sequence of Air France flight AF447 has revealed that the Airbus A330 did not enter the abnormal attitude law after it stalled, despite its excessive angle of attack.

The abnormal attitude law is a subset of alternate law on the aircraft and is triggered when the angle of attack exceeds 30° or when certain other inertial parameters - pitch and roll - become greater than threshold levels.

Alternate law allowed AF447's horizontal stabiliser to trim automatically 13° nose-up as the aircraft initially climbed above its assigned cruising altitude of 35,000ft.

The stabiliser remained in this nose-up trim position for the remainder of the flight, meaning that the aircraft would have had a tendency to pitch up under high engine thrust.

Crucially the abnormal attitude law - if adopted - would have inhibited the auto-trim function, requiring the crew to re-trim the aircraft manually.

After stalling, the A330's angle of attack stayed above 35°. But while this exceeded the threshold for the abnormal attitude law, the flight control computers had already rejected all three air data reference units and all air data parameters owing to discrepancy in the airspeed measurements.

Abnormal law could only have been triggered by an inertial upset, such as a 50° pitch-up or bank angle of more than 125°. "That never occurred," says French accident investigation agency Bureau d'Enquetes et d'Analyses.

The BEA is still attempting to explain why AF447's crew failed to rescue the aircraft after it climbed to 38,000ft and stalled. The pilot's control inputs were primarily nose-up, despite the stall condition.

There has been no indication that the aircraft switched into any other control law, other than alternate, during the accident - suggesting that auto-trim was available throughout the descent.

Failure to realise a need for manual re-trim was central to the loss of an Airbus A320 over the Mediterranean Sea about six months before the AF447 crash.

The auto-trim had adjusted the horizontal stabiliser fully nose-up but, during a flight envelope test involving near-stall, the aircraft switched control laws and inhibited the auto-trim.

Without manual re-trimming, the aircraft pitched up sharply as the crew applied maximum thrust. It stalled and the crew lost control.

In its conclusions over the accident the BEA highlighted the rarity of the need to trim manually, which created a "habit" of having auto-trim available made it "difficult to return to flying with manual trimming".

"One of the only circumstances in which a pilot can be confronted with the manual utilisation of the trim wheel is during simulator training," it said. "However, in this case, the exercises generally start in stabilised situations."

In the wake of the A320 accident, near Perpignan in November 2008, the BEA recommended that safety regulators and manufacturers work to improve training and techniques for approach-to-stall situations, to ensure control of an aircraft in the pitch axis.

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Stalled AF447 did not switch to abnormal attitude law

http://www.flightglobal.com/articles/2011/06/01/357394/stalled-af447-did-not-switch-to-abnormal-attitude-law.html

Investigation into the accident sequence of Air France flight AF447 has revealed that the Airbus A330 did not enter the abnormal attitude law after it stalled, despite its excessive angle of attack.

The abnormal attitude law is a subset of alternate law on the aircraft and is triggered when the angle of attack exceeds 30° or when certain other inertial parameters - pitch and roll - become greater than threshold levels.

Alternate law allowed AF447's horizontal stabiliser to trim automatically 13° nose-up as the aircraft initially climbed above its assigned cruising altitude of 35,000ft.

The stabiliser remained in this nose-up trim position for the remainder of the flight, meaning that the aircraft would have had a tendency to pitch up under high engine thrust.

Crucially the abnormal attitude law - if adopted - would have inhibited the auto-trim function, requiring the crew to re-trim the aircraft manually.

After stalling, the A330's angle of attack stayed above 35°. But while this exceeded the threshold for the abnormal attitude law, the flight control computers had already rejected all three air data reference units and all air data parameters owing to discrepancy in the airspeed measurements.

Abnormal law could only have been triggered by an inertial upset, such as a 50° pitch-up or bank angle of more than 125°. "That never occurred," says French accident investigation agency Bureau d'Enquetes et d'Analyses.

The BEA is still attempting to explain why AF447's crew failed to rescue the aircraft after it climbed to 38,000ft and stalled. The pilot's control inputs were primarily nose-up, despite the stall condition.

There has been no indication that the aircraft switched into any other control law, other than alternate, during the accident - suggesting that auto-trim was available throughout the descent.

Failure to realise a need for manual re-trim was central to the loss of an Airbus A320 over the Mediterranean Sea about six months before the AF447 crash.

The auto-trim had adjusted the horizontal stabiliser fully nose-up but, during a flight envelope test involving near-stall, the aircraft switched control laws and inhibited the auto-trim.

Without manual re-trimming, the aircraft pitched up sharply as the crew applied maximum thrust. It stalled and the crew lost control.

In its conclusions over the accident the BEA highlighted the rarity of the need to trim manually, which created a "habit" of having auto-trim available made it "difficult to return to flying with manual trimming".

"One of the only circumstances in which a pilot can be confronted with the manual utilisation of the trim wheel is during simulator training," it said. "However, in this case, the exercises generally start in stabilised situations."

In the wake of the A320 accident, near Perpignan in November 2008, the BEA recommended that safety regulators and manufacturers work to improve training and techniques for approach-to-stall situations, to ensure control of an aircraft in the pitch axis.

wow

Fundamentals not learned, nor protected against.

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My point regarding autotrim is that on the Airbus the required forcepull back is greatly reduced as the airplane autotrims. You can yank back on the stick (right to the stops) with little effort and the computer trims away the force. The terrain avoidance maneuver demonstrates that well.

On the Boeing, which only autotrims with configuration changes, the required force to pull back to the stops and HOLD it while the airplane decelerates is huge!

Someone above posted the article about the attitude portion of the Airbus laws not functioning correctly.

Moon, while agree with everything you have written, in this situation things may have been very different for the crew. As I said in the dark, in turbulance and they lose airspeed indications. They have the airplane squaking at them. I have only seen this scenario in the sim a few times in my career and it was easily handled because we were level in smooth air. In Tstorm I suspect the required ability would be slightly greater. It also appears that, for some reason, the crew may have not believed some of the other instruments. In any case, I think there is more than meets the eye here. But, you may be correct n the end and it may be a case of badly handled flying!!

I also don't see the case where some believe they flew into bad weather. So 3 other aircraft diverted around weather. Did they miss the turbulence all together? How far did they divert? How many of us use the RADAR to determine the best way through an area of weather and how often do we divert COMPLETELY around it? In all of the material supplied I don't see the crew flying directly into a cell (besides the fact that that the weather shots provided were large scale and do not represent what the crew would have seen on their RADAR).

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Trader, thanks for that. I'm still really not understanding about their loss of indicated airspeed (other than ADR restrictions on minimum displayed IAS) as this article http://www.avherald.com/h?article=41a81ef1/0068&opt=0 states there were valid ADR inputs until just prior to descending through 10,000'. But yeah, I hear you about the probable turbulence and disorientation. By that point, it would seem they had no chance.

Regarding flight into bad weather? Believe it. We've all had our "thunderstorm experience" that demonstrated to never, ever penetrate one that is fully developed. (Mine was over 30 years ago while a green cojo as the pilot of the Navajo flew directly into a developed cell just north of Calgary.)

As recently as 5 years ago on one of my contracts, departing Bangkok, I was the relief captain and was to take control at top of climb. I was watching the flight track of the captain flying, directly towards a cell (with wide anvil) about 150 miles ahead. When I got into the seat I turned the aircraft nearly 45 degrees to avoid and he asked me what I was doing! We entered the remnants of the anvil about 50 miles from the cell. I've never seen a Boeing ice up in cruise flight. There was no turbulence but it was such I required wing anti-ice. It lasted less than a minute but the lesson that foreign crew learned will (hopefully) last them a lifetime.

Over central Africa, I diverted nearly 200 miles one day to avoid ONE cell. One needs to experience the massive nature of weather in these latitudes to develop a healthy respect (read: Fear) against being caught up in it.

You ask "How many of us use the RADAR to determine the best way through an area of weather and how often do we divert COMPLETELY around it?" I would hope we ALL do. When used effectively, it is still the best tool for thunderstorm avoidance.

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I also don't see the case where some believe they flew into bad weather. So 3 other aircraft diverted around weather. Did they miss the turbulence all together? How far did they divert? How many of us use the RADAR to determine the best way through an area of weather and how often do we divert COMPLETELY around it? In all of the material supplied I don't see the crew flying directly into a cell (besides the fact that that the weather shots provided were large scale and do not represent what the crew would have seen on their RADAR).

Here is the link, again. (Need to load it in Firefox)

Yes, they would have had to divert quite a way. But the AF flight immediately behind them seemed to handle diverting ok.

Yes. Everyone else in this sequence of 6 flights, except El Al, diverted around weather that night.

Yes. They flew directly into a massive area of weather.

No. They shouldn't have been there.

Up until now, I had personally absolved the captain of any complicity in getting them into the situation, but the preliminary information indicated that he had left the flight deck only 9 minutes before the start of the incident. Surely, at 80 miles from the weather, at the very least he could have said "Don't fly through that" as he left the flight deck.

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Something from the quoted Flight Global article doesn't ring true for me. The aircraft did achieve one of the required parameters for the change to abnormal attitude law. The article says:

Abnormal law could only have been triggered by an inertial upset, such as a 50° pitch-up or bank angle of more than 125°. "That never occurred," says French accident investigation agency Bureau d'Enquetes et d'Analyses.

This is not correct. According to the A330 FCOM:

An abnormal attitude law in pitch and roll is provided if the aircraft is in flight and in any of these conditions :

  • Pitch attitude > 50° nose up or 30° nose down
  • Bank angle > 125 °
  • Angle of attack > 30° or < − 10°
  • Speed > 440 kt or < 60 kt
  • Mach > 0.96 or < 0.1

Since the angle of attack went above 30° and stayed there, the aircraft should have entered abnormal attitude law. This would result in a "USE MAN PITCH TRIM" annunciation on the primary flight display, which may have triggered the crew's attention to the large nose up trim setting.

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And do we know that that message was not displayd on the ECAM? If the pilots wer otherwise distracted with everything else going on would they have heard the ding and noticed the message?

Reading between the lines in the report quoted above we can see there there were other visual clues given to the crew that the aircraft was in a stalled configuration and those cues were ignored by the crew. For whatever reason they simply could not process what the aircraft was telling them and continued down the path they were already on. This sort of thingis documented through studies in unusual attitude awarness. Even pilots specifically trained in unusual attitudes sometimes fail to listes to the machine. Ask a fighter or aerobatic pilot if they have ever looked at the instruments and said to themselves " NAH THAT AINT RIGHT" It is a hard thing to over come when the feeling is so strong. Heavy turbulence can even make it worse.

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