A380 engine piece found in Groenland after 9 months

[fgrieu]

A 150 kg piece of the A380 engine 4 that experienced an uncontained engine failure over Groenland on 2017-09-30 was recovered under 4m of ice.
flightglobal's article (https://www.flightglobal.com/news/articles/pictures-a380-engine-parts-found-under-greenland-sn-459399/)
BEA's technical report (not yet updated) (https://www.bea.aero/uploads/tx_elyextendttnews/F-HPJE_TECHNICAL_REPORT_05.pdf)
https://cimg3.ibsrv.net/gimg/pprune.org-vbulletin/1600x1200/a380_862dde27df7887eb8af8e139103fe563ee5e376f.jpg

[atakacs]

Now that's really impressive.

I really wonder if it is worth the effort and expense. Is the BEA footing the bill? Sure it would be interesting to understand the circumstances of the failure but I was not expecting so much energy into it.

[BluSdUp]

Fantastic
Any details as to how they found it.
Magnetic anomaly equipment , maybe?

[BluSdUp]

Fair point.
Is this engine installed on any twin?
If so I for one would like a fix!

[golfyankeesierra]

I do hope it is the part they were looking for

[Steepclimb]

4 metres of ice since 2017? I thought it was all melting.

[Joe_K]

I really wonder if it is worth the effort and expense. Is the BEA footing the bill? Sure it would be interesting to understand the circumstances of the failure but I was not expecting so much energy into it.


The clue is in the second sentence of the report: "The BEA represents France, State of Operator, State of Registry and State of Design of the aircraft."
Politics...
EDIT: also striking when reading the report is how much use was made by BEA of Airbus resources and subsidiaries. Satellite imagery, ballistic calculations, even the plane carrying the synthetic aperture radar happened to be operated by an Airbus subsidiary.

[lomapaseo]

Wow, nice looking fan blades

[compressor stall]

For various reason Airbus / BEA / GE really wanted this found.

They were doing magnetometer scans.

[Droop Snoot]

It's closer to 21 months, not 9 months... now that's persistence!

[GordonR_Cape]

The story popped up on my newsfeed late yesterday, so I somehow thought it had already been linked on PPRuNe: https://www.flightglobal.com/news/articles/pictures-a380-engine-parts-found-under-greenland-sn-459399/
BEA had recently disclosed that it was exploring various high-tech methods, including synthetic-aperture radar fitted to a Dassault Falcon 20 jet, in a bid to locate the parts.

[romiglups]

Full story here (add https) eng.geus.dk/about/news/news-archive/2019/jul/missing-airplane-engine-part-found-by-geus-led-expeditions

Onera found magnetic anomalies from flights above the icepack, then danish picked it up.
I suppose the bill will be shared between GE/BEA/Airbus.

[BluSdUp]

Here in Norway we at times have 12 meters of annual snow fall measured on Svartisen and Ålfotbreen glaciers.
All but a few are shrinking , mind you.
Soooo!
Airbus and Engine supplier are using to much cash on finding fault.
Hmmm.
What a tragedy!!

[Paul Lupp]

A 150kg piece of metal....... could they not have used similar technology to find MH370?

[DaveReidUK]

A 150kg piece of metal....... could they not have used similar technology to find MH370?

Not really comparable.

For one thing, the track of AF66 was known. the engine let go over land, and the parts were found under a few metres of snow, not several miles down in the ocean.

[atakacs]

A 150kg piece of metal....... could they not have used similar technology to find MH370?
well in this case they had a very well defined search area over ground... Not even close with MH370.

Still I'm baffled by the scope of the effort.

[pax2908]

why the effort? maybe because this failure mode is not accounted for anywhere (thus perhaps counts as 1E-999) and possibly relevant beyond the A380 engine itself?

[capngrog]

Now that's really impressive.

I really wonder if it is worth the effort and expense. Is the BEA footing the bill? Sure it would be interesting to understand the circumstances of the failure but I was not expecting so much energy into it.

Most of you probably remember the crash of United Airlines Flight 232 in Sioux City, Iowa, USA on 19/07/1989. That crash was caused by the uncontained failure of the tail-mounted No.2 engine. This failure disabled all three hydraulic systems, resulting in the loss of all conventional controls, leaving control only by engine nos. 1 and 3 throttles. Key to determining the cause of the uncontained engine failure was examination of the fan disk, which unfortunately departed the aircraft at 37,000 ft. above the Iowa cornfields. The manufacturer of the engine (CF6-6), General Electric, offered a reward of $50,000 for finding the disk, and it was found in an Iowa cornfield some 3 months after the crash. Examination of the fractured disk revealed a metallurgical flaw which occurred during production; however, it was further determined that the cracks which consequently developed, should have been detected in the course of subsequent operational inspections.

So, in short, the finding of the fan disk of the A380 engine was well worth the effort and may lead to a clear understanding of the cause of the uncontained engine failure.

Cheers,
Grog

[LookingForAJob]

Still I'm baffled by the scope of the effort.There's a reason that so much of the aviation is as safe as it is......

[tdracer]

For various reason Airbus / BEA / GE really wanted this found.

They were doing magnetometer scans.

I would assume that since this was pretty clearly an engine failure, GE would be picking up the tab - if not all, at least the lions share. That's pretty standard procedure - when the cargo door blew out of the United 747 near Hawaii, Boeing spent a boatload of cash to find and recover the door so they could find out what went wrong and make sure it didn't happen again.

For design purposes, we assumed the probability of an uncontained engine failure (typically a rotor burst) at 10-8/hr, the current regulatory guidance requires a "one in twenty" analysis for rotor bursts - meaning the analysis needs to show that the probability of a rotor burst resulting in a catastrophic accident should be 5% or less.
However the engine company designs the rotors - especially the fan disc - to never fail. So, just like Sioux City, it's critically important to find out why it did fail so they can take appropriate action to prevent a future event.
BTW, IIRC, they traced the Sioux City fan disc failure to a flaw in the source material used to make the disc. There were nine other fan discs made from that same batch of material, which were promptly removed from service.

[flight sim boy]

I would assume that since this was pretty clearly an engine failure, GE would be picking up the tab - if not all, at least the lions share. That's pretty standard procedure - when the cargo door blew out of the United 747 near Hawaii, Boeing spent a boatload of cash to find and recover the door so they could find out what went wrong and make sure it didn't happen again.

For design purposes, we assumed the probability of an uncontained engine failure (typically a rotor burst) at 10-8/hr, the current regulatory guidance requires a "one in twenty" analysis for rotor bursts - meaning the analysis needs to show that the probability of a rotor burst resulting in a catastrophic accident should be 5% or less.
However the engine company designs the rotors - especially the fan disc - to never fail. So, just like Sioux City, it's critically important to find out why it did fail so they can take appropriate action to prevent a future event.
BTW, IIRC, they traced the Sioux City fan disc failure to a flaw in the source material used to make the disc. There were nine other fan discs made from that same batch of material, which were promptly removed from service.

The LPC on the Gp7000 is a P&W part so P&W / UTC might be involved in footing the bill!

[Smythe]

That's pretty standard procedure - when the cargo door blew out of the United 747 near Hawaii, Boeing spent a boatload of cash to find and recover the door so they could find out what went wrong and make sure it didn't happen again.


Oh hell yea they did...

First off, that was not the first time a 747 door had failed, ....the incident you cite where the door had failed in 1989 on a Pan Am flight near HI, it was at least the second reported incident. There was a failure reported 2 years earlier...

WHY Boeing spent so much time on finding the door, was they did not correct the door failure after the first failure.

The next time the door failed, 2 years later, on a United Airlines 747 near Honolulu in 1989, the Boeing jet faced an “explosive decompression,” and nine passengers were “ejected from the airplane and lost at sea.

This is why they spent so much time and money, was that their lack of response in correcting the design fault, that has now killed 9 people....trying to determine blame...well...yes, they certainly had an impetus to make sure it did not happen again, they just killed 9 people on a known issue.

From the final report:
Also contributing to the accident was a lack of timely corrective actions by Boeing and the FAA following a 1987 cargo door-opening incident on a Pan Am B-747,” the NTSB said.

How many people did their lack of response to a known issue, put at risk, and kill with the MAX?

Face it, Boeing knew the issues, and failed to disclose to the FAA and the pilots...putting at risk EVERYONE who flew on those aircraft since being certified to fly.

[tdracer]

You know Smythe, your non-stop Boeing bashing has gotten rather old. You might want to find something new to bitch about.

[lomapaseo]

......................................
Face it, Boeing knew the issues, and failed to disclose to the FAA and the pilots...putting at risk EVERYONE who flew on those aircraft since being certified to fly.

That is one hell of a reach from somebody who is not in the business of fixing fleetwide problems.

The industry, including operators does not have the capacity to ground aircraft after every incident while they come up with fixes that actually work and not cause other problems. Sure every manufacturer considers a cargo door failure and the resulting decompression. But just how big a decompression rate is judged based on the opening per unit time and the ability to bleed off pressure waves that can take out other systems. The United event was a wake up or surprise that the decompression wake would eject passenger seats in whole. Thus the magnitude of the system involvement from the passenger standpoint surprised us all. Hence the reaction after the event.

But let's get back to this thread subject. The surprise to me was how little secondary damage to systems actually occurred with such a massive fan disk failure. But that surprise while welcomed.doesn't make us sleep well in light of other historical events like Sioux city etc.. So once again we go to the extra work of getting more information by finding key parts.to better understand what corrective actions are warranted throughout the operators

[AviatorDave]

4 metres of ice since 2017? I thought it was all melting.

That's only what they tell you, to make you feel better paying your carbon tax.

[Maninthebar]

That's only what they tell you, to make you feel better paying your carbon tax.

Whenever I see a statement like this I wonder who "they" are

Or maybe I am missing some obvious sarcasm, in which case apologies

[Zeffy]

https://youtu.be/zPcSU0A1G9w

[Gove N.T.]

4 metres of ice since 2017? I thought it was all melting.

Yes, it melts every year in the "summer" and freezes again in the winter. Strange that.
But this isn't a GW forum -
https://www.telegraph.co.uk/comment/columnists/christopherbooker/5028380/The-Global-Warming-Three-are-on-thin-ice.html

[WillFlyForCheese]

You know Smythe, your non-stop Boeing bashing has gotten rather old. You might want to find something new to bitch about.

He/she is rather fixated . . .

[ThreeThreeMike]

The BEA report provides very interesting information about the methodology and computations made to pinpoint the search area for the missing parts.

[Deep and fast]

WHY Boeing spent so much time on finding the door, was they did not correct the door failure after the first failure.
Seems a Boeing thing to wait for two accidents....

[TURIN]

WHY Boeing spent so much time on finding the door, was they did not correct the door failure after the first failure.
Seems a Boeing thing to wait for two accidents....

Not really.
DH Comet 1.

[Seat4A]

The BEA report provides very interesting information about the methodology and computations made to pinpoint the search area for the missing parts.

Indeed

https://www.bea.aero/uploads/tx_elyextendttnews/F-HPJE_TECHNICAL_REPORT_05.pdf

Published : June 2019

[pax2908]

esp @tdracer (off topic) re. rotor burst. A while ago we saw photos of a large blade fragment stuck in the "containment belt" (proper term = ?) Would you think this could have been the "root cause" (how come it was not dislodged by the rest?) When you say fan disc designed not to fail, does that include when N-1 blades keep hitting a rigid obstacle until the fan stops turning?

[lomapaseo]

esp @tdracer (off topic) re. rotor burst. A while ago we saw photos of a large blade fragment stuck in the "containment belt" (proper term = ?) Would you think this could have been the "root cause" (how come it was not dislodged by the rest?) When you say fan disc designed not to fail, does that include when N-1 blades keep hitting a rigid obstacle until the fan stops turning?

Two ways for the blade w root to get in belt by itself.

Walk out under extreme vibratory loads with disk intact (ala NA CF6 in Albuquerque

Slip out when crack that breaks the disk opens up between OD and ID

The Kevlar belt will give a couple of feet outwards as the rotor pushes outward leaving lots of room for lesser debris to escape being driven through the Kevlar. The rest of the metal case the Kevlar is wrapped around just gives up right away

[tdracer]

To add a bit to what lomapaseo wrote:
Blade out events are extremely dynamic - every one is different and the results are not really repeatable. They run the full blown engine test once (generally after several smaller 'rig tests' to make sure things will work as designed) and hope that it passes - pass/fail being nothing goes out tangentially through the containment system, nothing important 'falls off', and the engine quits 'gracefully'. The blade is released by a small explosive charge in the root with the engine running at redline N1. The blade will hit the next (trailing) blade and containment ring (even the older steel ones would distort very dramatically), then the pieces tend to come back in and cause havoc, damaging the rest of the fan blades (occasionally even breaking off another blade), while the sudden imbalance causes massive vibrations of the whole mess. If you get a chance to watch one of the slow motion videos, do it - the amount of destruction and way everything moves around and distorts is simply amazing. By design, the fan disc shouldn't fail, although it'll likely lose bits of the fan blade attachment dovetails. Way back ~30 years ago when they did the fan blade out for the original PW4000, part of a fan blade made it through the (steel) containment ring and was embedded in the (fan case mounted) FADEC - interestingly that was considered a 'pass' since it didn't escape the engine...

Cause of a fan blade out are varied - oftentimes it's not an entire blade - the blade fails someplace outboard of the root (metal fatigue - possibly caused by FOD induced blade damage), I recall a Trent 800 event which was caused by wear of the blade dovetail due to inadequate lubrication of the dovetail. They do the test releasing an entire blade since that's considered to be worst case.

On the original GE90, when they did the blade out test the containment system worked, and the engine shutdown gracefully, but all sorts of stuff fell off - the inlet, parts of the gearbox, etc. GE argued that they could show by analysis that they'd solved the problem of stuff falling off, but the FAA didn't buy it and made them re-run the test, destroying another expensive engine in the process.

[megan]

A380 blade off test.

https://www.youtube.com/watch?v=KHU7PBIezB0

[Thaihawk]

Oh hell yea they did...

First off, that was not the first time a 747 door had failed, ....the incident you cite where the door had failed in 1989 on a Pan Am flight near HI, it was at least the second reported incident. There was a failure reported 2 years earlier...

WHY Boeing spent so much time on finding the door, was they did not correct the door failure after the first failure.

The next time the door failed, 2 years later, on a United Airlines 747 near Honolulu in 1989, the Boeing jet faced an “explosive decompression,” and nine passengers were “ejected from the airplane and lost at sea.

This is why they spent so much time and money, was that their lack of response in correcting the design fault, that has now killed 9 people....trying to determine blame...well...yes, they certainly had an impetus to make sure it did not happen again, they just killed 9 people on a known issue.

From the final report:
Also contributing to the accident was a lack of timely corrective actions by Boeing and the FAA following a 1987 cargo door-opening incident on a Pan Am B-747,” the NTSB said.

How many people did their lack of response to a known issue, put at risk, and kill with the MAX?

Face it, Boeing knew the issues, and failed to disclose to the FAA and the pilots...putting at risk EVERYONE who flew on those aircraft since being certified to fly.

Would it be feasible for all those who flew in this type in the timeframe Boeing knew there was a fault to launch a class action lawsuit for their lives being put at risk?.

Here in the UK lawyers are grubbing like mad for business over PPI mis-selling, so maybe our lern'd friends are missing a trick?.

[Thaihawk]

Whenever I see a statement like this I wonder who "they" are

Or maybe I am missing some obvious sarcasm, in which case apologies

"They" being tax-grubbing governments in many countries, mainly in Europe.

[pax2908]

re. fan hub design & test ... and successful blade out tests are then fully analyzed .(the hub) ... to gain confidence in the "design to never fail" in the sense would not risk separating as a big piece as in AF66 ?

[Sailvi767]

You know Smythe, your non-stop Boeing bashing has gotten rather old. You might want to find something new to bitch about.

Maybe he could talk about Airbus knowing they were flying aircraft with bad pitot tubes prior to AF447.

[Peter H]

Maybe he could talk about Airbus knowing they were flying aircraft with bad pitot tubes prior to AF447.


Not certain that is entirely justified, wasn't Air France making the decisions?

I've only a vague memory, but certainly some people seem to have thought so.

From https://www.economist.com/comment/1175706Nalliah Thayabharan (https://www.economist.com/user/5451149/comments) Aug 8th 2012 12:10 GMT

Majority of the 1,000 Airbus A330s and A340s are fitted with pitot probes 0851GR, manufactured by GOODRICH Sensors and Integrated Systems, the
standard offering by the airframer. Air France chose to equip its Airbus fleet with pitot probes C16195AA manufactured by THALES - a french manufacturer.
Airbus recommended that THALES pitot probes C16195AA should be replaced by THALES pitot probes C16195BA to prevent the problem of water intrusion
which had been observed. Air France replaced pitot probes on its Airbus A320s where the incidents of water ingress were observed, and decided to do so in
its Airbus A330s & A340s only when failures of pitot probes occurred.

In 2008 Air France experienced incidents involving THALES pitot probe icing for a few minutes, after which the phenomenon disappeared causing loss of airspeed
data in flight in cruise phase on A330s and A340s.In 2009, tests confirmed that the new pitot probe could improve its reliability, prompting Air France to accelerate
the replacement of pitot probes,but this work had not been carried out on the ill fated Airbus A330 - "F-GZCP".

In July 2009, Airbus issued new advice to A330 and A340 operators to replace french made THALES pitot probes with pitot probes from GOODRICH Sensors and
Integrated Systems.

On August 12, 2009, Airbus issued Mandatory Service Bulletins requiring pitot probes C16195AA manufactured by THALES were no longer tobe used. This requirement
was incorporated into Airworthiness Directives issued by the European Aviation Safety Agency - EASA on August 31, 2009 and by the US Federal Aviation Administration
- FAA (an operating mode of the U.S. Department of Transportation) on September 03, 2009.

Air France is owned by the state. THALES is french; Anyone who dares to challenge Air France goes bankrupt as did AOM (previously Air Outre-Mer) and Air Liberté.

[tdracer]

re. fan hub design & test ... and successful blade out tests are then fully analyzed .(the hub) ... to gain confidence in the "design to never fail" in the sense would not risk separating as a big piece as in AF66 ?

The do analyze the various components after the test for 'unexpected' distress of the various components, but I don't know specifics.
The problem that no one likes to talk about is that all these expensive tests and analysis assume the component is made properly. There are margins in the design to account for the expected variations between components, but no one knows how to analyze is it's not per drawing or the material is not per spec. IIRC, the problem with the Sioux City fan disc was some contamination in the titanium alloy that shouldn't have been there.

[atakacs]

Well I really hope that the recovered piece will yield some information about this incident.
Am I correct that the Engine Aliance is the less used 380 engine and not used on any current or future type?

[NiclasB]

4 metres of ice since 2017? I thought it was all melting.
Living at 64N, my seasonal observation of snow is that it falls on the top and melt at the bottom...

[tdracer]

Well I really hope that the recovered piece will yield some information about this incident.
Am I correct that the Engine Aliance is the less used 380 engine and not used on any current or future type?


My memory says the market split between the EA and the Trent was reasonably close to 50/50 - it was about to swing well into Rolls favor when Emirates switched from EA to the Trent but most of those orders were subsequently cancelled.
I'm unaware of any plans of to use it on another aircraft type, and given it's an older generation design, that's unlikely to change.
That being said, EA powered A380s are likely to remain in service for many years, so if there is an issue that extends to any other engines, it would be good to find and correct it soon. Another uncontained failure might not end so happily (remember the uncontained Trent failure on Qantas 32 was a very close call).

[lomapaseo]

The do analyze the various components after the test for 'unexpected' distress of the various components, but I don't know specifics.
The problem that no one likes to talk about is that all these expensive tests and analysis assume the component is made properly. There are margins in the design to account for the expected variations between components, but no one knows how to analyze is it's not per drawing or the material is not per spec. IIRC, the problem with the Sioux City fan disc was some contamination in the titanium alloy that shouldn't have been there.

Just to add

The fan disk enjoys one of the highest overspeed stress margins due to it's primary design function to carry giant blades at low RPM Typically greater than 100% above the typical operating speed and the engine probably can't get it above 10% and still run as a cycle. Then the manufacturer designer considers low cycle fatigue (stop-start cycles) margin of > 20,000 takeoffs based on his reliable ability to detect the smallest metalurgical defect that could get into the material during manufacture/forging etc. The A380 should be oodles away from achieving that amount of cyclic use on a single engine.today.

That leaves us with unique one-offf failure modes rarely seen in service like misassembly, unexpected gross damage (maintenance or manufacture) or even improper material solvents (corrosives) and even rarer today, unexpected operating conditions (speed/temperature).

I'm quite sure the investigation is considering all of these as they proceed.

[DaveReidUK]

My memory says the market split between the EA and the Trent was reasonably close to 50/50 - it was about to swing well into Rolls favor when Emirates switched from EA to the Trent but most of those orders were subsequently cancelled.

There have been 241 A380 built to date (including prototypes). Of those, 110 are RR-powered and the other 131 EA.

[atakacs]

There have been 241 A380 built to date (including prototypes). Of those, 110 are RR-powered and the other 131 EA.
thanks for the data point.

But am I correct that they are not anymore produced (ie the last 380s - and I am pretty sure that all current orders will not be fulfilled - will be RR only)?

[DType]

Iompaseo said
Typically greater than 100% above the typical operating speed
That means the operating speed is running at less than 25% of burst stress.
The margins were nowhere near as generous when I was a boy, in fact they were scarily slim!
Has it really changed that much????

[lomapaseo]

Iompaseo said
Typically greater than 100% above the typical operating speed
That means the operating speed is running at less than 25% of burst stress.
The margins were nowhere near as generous when I was a boy, in fact they were scarily slim!
Has it really changed that much????

Regulatory wise the answer is No. That's because of the reg of minimum margin. Of course one can exceed that all you want at the expense of weight. So you can bet the manufacturer goes for minimum weight to ,meet all design requirements. That's easy to do with a perfect bell cross section (think solid flywheel), but with gas turbines you have to add in all those pesky blades screwing up your stress to weight numbers :)

Historically most overspeed failures are with turbines that snap their couplings (the compressor loadings). But even more common have been overstress combined with excessive temperature (fires). I can't even think of a fan rotor that can/has overspeeded to exceed its strength

[4listair]

Reuters: Dozens of Airbus A380s face urgent checks after cracked part dug from ice
https://www.reuters.com/article/us-airbus-a380-exclusive-idUSKCN1VB1GH

Confirming the focus of the probe after Reuters reported the plans for inspections, France’s BEA air accident agency said it had discovered a “sub-surface fatigue crack” on the recovered part [fan hub] and the engine maker was preparing checks.

BEA Twitter:

https://twitter.com/BEA_Aero/status/1164169933795684352

Accident @Airbus (https://twitter.com/Airbus) #A380 (https://twitter.com/hashtag/A380?src=hashtag_click) F-HPJE @airfrance (https://twitter.com/airfrance) 30/09/2017 - the part from the fan hub recovered on 01/07/19 has been examined by @enginealliance (https://twitter.com/enginealliance) under @BEA_Aero (https://twitter.com/BEA_Aero) supervision - metallurgical examination of the recovered titanium fan hub fragment identified a subsurface fatigue crack origin. -The fracture was initiated in a microtextured area approximately in the middle of the slot bottom. Examination of the fracture is ongoing. - @enginealliance (https://twitter.com/enginealliance) has announced today to the concerned A380 operators that an engine inspection campaign will be launched soon.

[lomapaseo]

Accident @Airbus (https://twitter.com/Airbus) #A380 (https://twitter.com/hashtag/A380?src=hashtag_click) F-HPJE @airfrance (https://twitter.com/airfrance) 30/09/2017 - the part from the fan hub recovered on 01/07/19 has been examined by @enginealliance (https://twitter.com/enginealliance) under @BEA_Aero (https://twitter.com/BEA_Aero)supervision - metallurgical examination of the recovered titanium fan hub fragment identified a subsurface fatigue crack origin. -The fracture was initiated in a microtextured area approximately in the middle of the slot bottom. Examination of the fracture is ongoing. - @enginealliance (https://twitter.com/enginealliance) has announced today to the concerned A380 operators that an engine inspection campaign will be launched soon.

Well if "triple melt" didn't get it, what happened to the manufacturers incoming sonic inspection? surely in this day and age we shouldn't be talking about a defect so small that still resulted in a catastrophic crack progression in so few cycles.
So which is it?.

[tdracer]

Well the good news is that if the potential defect is in/near the dovetail slot, on-wing inspection should be reasonably easy and straight forward - something that could readily be done during an overnight.

[lomapaseo]

Well the good news is that if the potential defect is in/near the dovetail slot, on-wing inspection should be reasonably easy and straight forward - something that could readily be done during an overnight.

Yea, should be fun taking all those blades out at 30-40 lbs per piece, on wing :)

and why should the defect be at one area on the disk rather than just anywhere ? unless of course it's a machining process defect?

[jmmoric]

Living at 64N, my seasonal observation of snow is that it falls on the top and melt at the bottom...

Yes and no.

I think the snow falls on the top of the inland ice, but the huge pressure from the kilometre thick layer of ice, presses it to the sides into the glaciers along the edge, here it melts. So there is a steady flow of ice deep below to the sides.

https://www.youtube.com/watch?v=mlDseTBwUlM

This is one of the old DEW line radar stations still on the icecap, it was abandonned many years ago, and is slowly slipping into the ice.

[etudiant]

Yes and no.

I think the snow falls on the top of the inland ice, but the huge pressure from the kilometre thick layer of ice, presses it to the sides into the glaciers along the edge, here it melts. So there is a steady flow of ice deep below to the sides.

https://www.youtube.com/watch?v=mlDseTBwUlM

This is one of the old DEW line radar stations still on the icecap, it was abandonned many years ago, and is slowly slipping into the ice.

Think this is irresponsible behavior by the military.
To just abandon a facility, warts and all, without restoring the site even minimally is just abusing the environment.
It is also very evident in Alaska, where abandoned military sites at Barrow and Nome are slowly rotting away.
In Greenland, at Camp Century, I believe there was a lot of debris and even nuclear waste just dumped on the ice, which is now resurfacing.

[WHBM]

Seems strange, this incident happened 2 years ago, it's reasonably apparent it's around the front fan, and yet detailed checks of that area on the engine type involved wait for 2 years to be identified. What if it had happened over water ?

[lomapaseo]

Seems strange, this incident happened 2 years ago, it's reasonably apparent it's around the front fan, and yet detailed checks of that area on the engine type involved wait for 2 years to be identified. What if it had happened over water ?

Quite a few over the last 60 years years have been non-recovered. But they still were assessed for probable cause based on remaining evidence as the plane survives. Had a plane not survived much greater effort sometimes taking years, is employed to come up with probable initiating cause and corrective action of some sort.. If we stick to discussing only this one, then the question is just what action could one expect to take that even had a remote chance of preventing a completely unexpected event without an obvious cause.. I'm not saying nothing was done since everybody who operates in the industry was on the lookout for any problems with the fan as well as deep record searches of the pedigree itself. Hence the continued search in Greenland when the environment improved.

[TeachMe]

CBC has a science show where there was an interview with one of the guys who worked on finding it. About half way through the link below. If ti does not work for any reason, it is Quirks and Quarks and was Sept. 14, 2019.

TME

http://cbc.mc.tritondigital.com/CBC_QUIRKSAIO_P/media/quirksaio-HwCZapgL-20190913.mp3

[Turbine D]

Yea, should be fun taking all those blades out at 30-40 lbs per piece, on wing :)

and why should the defect be at one area on the disk rather than just anywhere ? unless of course it's a machining process defect?

Because the defect is contained in the billet. the billet is sliced into what will be multiple disks after forging. The forging process then moves the defect into a particular location of the forged disk. It is not a haphazard event. Fact is, if you were to locate the defect in the billet slice, a computer program can predict after forging where the defect will wind up. Something new in technology comes along everyday, eh?

[sooty655]

Because the defect is contained in the billet. the billet is sliced into what will be multiple disks after forging. The forging process then moves the defect into a particular location of the forged disk. It is not a haphazard event. Fact is, if you were to locate the defect in the billet slice, a computer program can predict after forging where the defect will wind up. Something new in technology comes along everyday, eh?
But the defect wasn't detected in the billet, or at any subsequent manufacturing stage, so a theoretical ability to track it through the process doesn't help. Similar defects might be in similar places in other discs from the same billet, but defects in other discs could be anywhere unless/until the prime defect cause in the billet is known.

[lomapaseo]

Are they now concluding a material defect was present at the origin of the fracture or is the initiating cause still a mystery?.

[MurphyWasRight]

But the defect wasn't detected in the billet, or at any subsequent manufacturing stage, so a theoretical ability to track it through the process doesn't help. Similar defects might be in similar places in other discs from the same billet, but defects in other discs could be anywhere unless/until the prime defect cause in the billet is known.
If the defect was suspected to be linked to a specific billet seems that only a relatively few discs would need to be inspected. Not clear from the items posted here if that is the case.

The inspections will probably be more general and will be looking for defects that either escaped original inspections (or more likely) grown over time so they now can be detected if present.

Either way would be surprised if inspections did not include the entire disc unless some design feature was identified that stressed one position more that others.
I don't have specific knowledge but would seem the discs would have be very symmetrical and balanced parts.