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nuisance79
13th Nov 2020, 09:08
An AN-124 out of Novosibirsk limped back to the Airfield today due to an uncontained engine failure. The Engine almost completely disintegrated and some spectacular wing and fuselage damage.

Gear failure on touchdown resulting in runway excursion.

Appears all on board ok.

treadigraph
13th Nov 2020, 09:19
https://cimg4.ibsrv.net/gimg/pprune.org-vbulletin/1000x770/20201113_0_c_1_e889311bef55c408d167b6931935fd06f07c40a1.jpg

Less Hair
13th Nov 2020, 10:03
IIRC they have the main avionics bay in the upper deck next to the spar.

Wirbelsturm
13th Nov 2020, 10:51
Makes the bi-annual 'engine failure after take-off' in the sim seem a little mundane!!!

Good job getting it safely back on the deck, I'm sure the dents will buff out and a bit of speed tape over the hole will see it good!

Edited to add: That's a hell of an egress ladder on the starboard side! :eek:

TURIN
13th Nov 2020, 10:58
Wow, One of these diverted into MAN UK the other day, left yesterday. Glad it wasn't that one. Russians build em tough...well, not the engines obviously.

CargoOne
13th Nov 2020, 11:36
Russian forums reporting substantial electrical loss after an uncontained engine #2 failure coupled with a loss of engine #1 control, which remained on 70% thrust all way down including the landing roll, kept running after the aircraft went stand still.

Less Hair
13th Nov 2020, 11:39
Bit like that Qantas A380 it seems. Lucky escape again fortunately.

Mike-Bracknell
13th Nov 2020, 11:39
This is precisely why I never want to sit in that row of seating in any pax jet.

knackered IV
13th Nov 2020, 11:56
Looking forward to those pilotless aeroplanes.

krismiler
13th Nov 2020, 12:02
Worth comparing to Cathay 780 as well where the crew were unable to control engine thrust and had 70 - 80% N1 on engine 1 during landing.

Touchdown speed would have been well in excess of normal and control very difficult with 70% N1 on an outbound engine. Almost certainly tyre failure followed by gear failure, possible hydraulic problems as well given the extent of the damage.

Looks like an excellent job by the crew.

Wycombe
13th Nov 2020, 13:01
I wonder if they did the standard 3 minute engine run-up on the threshold prior to departure?

fox niner
13th Nov 2020, 13:18
From the pictures it seems like the N1 rotor cartwheeled over the top to the other side.

AKO
13th Nov 2020, 13:53
Or maybe it went through the cabin. Great job by the crew. That must have been a handfull.

Machdiamond
13th Nov 2020, 14:27
Good video of the overrun.

https://www.youtube.com/watch?v=zdrGiF8pnxs

treadigraph
13th Nov 2020, 14:43
Take off here plus various clips of landing.

https://www.youtube.com/watch?v=bmc2zeHtNSc

Mechta
13th Nov 2020, 15:10
The pilot's description of the incident, as quoted by Oleksiy Sokolov on 'Mentour Pilot':

The second engine exploded and cut electric wires, so we lost all the electricity. And we returned to the aerodrome of departure on an airplane having a total electric failure. We lost all the communication, both intra-cockpit and with the ATC. We just gained 300m altitude at that point. We were a crew of 6, and other technical crew of 8, they were in the rear cabin. We took a decision to return to the aerodrome of departure, visually, we tried to establish visual communication but that didnít work. We took a decision to land on RWY25, since it was a critical situation and we took a decision to land as soon as possible. Since we didnít have a lot of altitude and excess of thrust too. There was a complete electric failure, brakes didnít work, reverse didnít work either since the wires were cut. The landing was soft, there was no damage during the touchdown, all the damage was due to the runway excursion. The gauges in the cockpit didnít work, from the angle of attack we figured out the speed was about 280, it was a calculated airspeed. We havenít even raised the flaps at that time, just raised the gears and we heard a bang. We still had control, but the electrical system failed completely.

RatherBeFlying
13th Nov 2020, 16:14
I am reminded of ASN Burbank DC-6 1976 (https://aviation-safety.net/database/record.php?id=19760208-0) where a prop blade went through the fuse and took out the opposite engine and hydraulics.

Kudos to the 124 crew:ok:

ATC Watcher
13th Nov 2020, 16:45
we lost all the electricity. And we returned to the aerodrome of departure on an airplane having a total electric failure. We lost all the communication, both intra-cockpit and with the ATC. ..... , brakes didn’t work, reverse didn’t work either since the wires were cut. The landing was soft, there was no damage during the touchdown, all the damage was due to the runway excursion. The gauges in the cockpit didn’t work, from the angle of attack we figured out the speed
Nobody would l like to be in this situation, but the curved APP, possibly even sideslip to counter thrust and keep descending at correct angle, ( if I interpret the videos clips correctly ) a prefect touchdown , then wait until it stops and get everybody out unhurt deserves big respect .. Those guys knows how to fly.

Riskybis
13th Nov 2020, 17:45
Good job it was a VMC day !!!

Atlantic Explorer
13th Nov 2020, 18:25
Ain’t that the truth!!

atakacs
13th Nov 2020, 20:54
And there goes another Progress D-18T... I wonder if the CF6 retrofit will eventually happen...

Very well done by the crew - does anyone know if there was freight in this flight ?

Mechta
13th Nov 2020, 21:01
According to this, 83.5 tons of freight: Mentour AN-124 engine failure description (https://mentourpilot.com/antonov-an-124-suffers-uncontained-engine-failure/)

ZH871
13th Nov 2020, 21:32
Interestingly, posted 23/03/2020:

"Ukrainian authorities have ordered Antonov An-124 operators to inspect engines on the type after an uncontained powerplant failure."
"The directive, which takes effect from 25 March..."

Source: aircargonews.net/airlines/freighter-operator/an-124-disk-inspection-ordered-after-uncontained-failure/

WillowRun 6-3
13th Nov 2020, 23:35
SLF attorney here, but still able to see fabulous piloting performance by crew.
Waiting for report from algorithm writers of fidelity-to-reality rating of test algorithm running onboard the aircraft; I'm sure its truthfulness to what actually was performed by the crew was, what, close to 98.6 percent?

Capn Bloggs
14th Nov 2020, 04:41
Did I see a couple of ejections after it hit the snow?

Hat, coat...

tdracer
14th Nov 2020, 06:45
And there goes another Progress D-18T... I wonder if the CF6 retrofit will eventually happen...


They were working on a new version AN-124 with CF6-80C2 engines, but I don't know if that's on on-going program. Awfully quiet if it is still happening.
I never heard of a planned retrofit, although if it did happen for new production it would make the engineering for a retrofit quite a bit easier.

birdy340
14th Nov 2020, 07:41
Well done Captain, that was not even a sim scenario case.Wife and children will be happy to see you safe and healthy.

dixi188
14th Nov 2020, 07:52
The CF6 has had issues with uncontained engine failures, though I think it may be on the -50 series. HP2 turbine wheel IIRC.

dead_pan
14th Nov 2020, 11:59
ATC Watcher

+1

I bet the guy filming from the apron had an Airplane moment: "OMG he's coming right at me!!"

Two's in
14th Nov 2020, 14:52
Sim Instructor:

"So immediately after take off we're going to lose Number 2 engine, Freeze Number 1 at 70%, fail all electrics and power, take out the instrument panel and all the comms - ready?"

morton
14th Nov 2020, 15:07
So, he takes off, doesn’t get very high and circles back to the Airfield – all in Radio silence. Those in the tower have a terrific view of him coming round, landing and running into the overshoot.
Am I missing something or have they photo-shopped out all the emergency services chasing after this Aircraft during a very non-standard approach and landing?

Pistonprop
14th Nov 2020, 16:43
morton, all ATC knew was that they had lost radio contact. You don't call out the emergency vehicles for comm failure. Could they see any damage on the a/c? I doubt it.

lomapaseo
14th Nov 2020, 17:36
morton

He is going kind of fast for emergency vehicles to catch up and there is some question as to how stable he may remain. The real issue is how long it took to catch him at the end and what conditions did he state to the tower..

I was in one of these emergency vehicles once when a large transport was returning with a structural emergency, undefined, other than the pilots wanted to be on the ground immediately, We shut down all air operations until he rolled out and we chased him down the runway, probably a mile behind intending on catching him when he came to a stop

The Fat Controller
14th Nov 2020, 17:59
Great Save !

Hope the crew got plenty of Vodka and Caviar.

JW411
14th Nov 2020, 17:59
Just to introduce a bit of levity into what is going to be a long "why didn't he do this or that" from people who have mostly never been near an aeroplane but think that they know everything.

When I got near my first Argosy in 1962 I can vividly remember thinking during the external walkaround that if I had ever had to put it on the ground with the gear up then there was a lot of fuselage underneath me to be ground away before the family jewels were in peril.

When I got near my first Belfast in 1972, I came to the immediate conclusion that the future of my family was in even better shape.

How was I to know that Antonov had designed an even better solution?

The crew did well - very well.

atakacs
14th Nov 2020, 18:12
They were working on a new version AN-124 with CF6-80C2 engines, but I don't know if that's on on-going program. Awfully quiet if it is still happening.
I never heard of a planned retrofit, although if it did happen for new production it would make the engineering for a retrofit quite a bit easier.
I know for fact that is was considered for the Volga-Dnepr fleet but I guess it turned out to be too expensive / complex. Yet, they, just as Antonov or the Russian Air Force have to find a way to make those Progress D-18T last (and there is already some serious canibalism going on...). Don't know what will be the eventual outcome but something has to give...

Tech Guy
14th Nov 2020, 18:41
One imagines the seat cushions are no longer servicable.
Epic job be the crew for getting her back on the ground, espercially without injuries. :ok:

tdracer
14th Nov 2020, 19:31
dixi188

Right - the CF6-50 has had a number of issues with uncontained turbine disc failures (with a number of AD's to manage it). The CF6-80A also had a couple pretty spectacular turbine disc failures.
Off hand, I can't think of any uncontained failure issues with the -80C series.

morton
14th Nov 2020, 21:43
Pistonprop - Radio silence was only one aspect. I thought the low circle back after take off and abnormal approach might have been an indicator of things not going too well.

Turbine D
14th Nov 2020, 22:11
tdracer

I can think of one.
Uncontained Engine Failure and Subsequent Fire American Airlines Flight 383 Boeing 767-323, N345AN Chicago, Illinois October 28, 2016
CF6-80C2B6 turbofan engines, with one engine mounted under each wing.
https://reports.aviation-safety.net/2016/20161028-2_B763_N345AN.pdf

Pistonprop
14th Nov 2020, 22:48
lomapaseo, bear in mind they didn't state anything to the tower as they had lost contact.

morton, granted he was low, but other than that there were no other visual clues and the landing itself was perfectly normal.

Capn Bloggs
15th Nov 2020, 02:18
Morton, I agree. Jets like that don't do low-level immediate returns just because the radio has failed.

PEI_3721
15th Nov 2020, 08:16
Bloggs / Morton, et al,

e.g. BAe146 immediate return with total electrical failure at dusk, low cloud, and snow. (Total as in 'total', nil, zip, nothing.)

Also, related to this thread was the 146 which suffered a failure of an engine rear bearing, shaft shear, and uncontained turbine disc - maintenance misunderstanding.
The crew successfully managed the engine failure, adjacent engine failure / fire, with indications that a third engine had failed - no instruments / electrics. The consequential loss of all hydraulics, flaps, spoiler, airbrake, and no pitch trim. And, from extensive shrapnel damage, the loss of cabin pressure, two small fires in the cabin (no injuries), holes in the flaps, fuel tank, and main spar !
Landing on a long military runway which fortunately had a shallow lead-in taxiway providing a paved overrun area. (Mexico)

Celebrate - and learn from the successes.

Less Hair
15th Nov 2020, 08:17
How would a pre-programmed air vehicle, autonomous drone or remotely piloted aircraft have dealt with an electric failure and non normal handling like this?

atakacs
15th Nov 2020, 08:23
Most likely very badly.
But there is the argument that it would have saved many other situations where the pilots have crashed perfectly flyable airframes.

WillowRun 6-3
15th Nov 2020, 12:11
Let's take an example: CFIT, 1995, American Airlines 965, Colombia. That was a "perfectly flyable airframe" - although stated by this SLF/attorney that's not incorrect or controversial. So, the "argument" is that today's algorithm techniques and related processes could have conducted that flight operation without a CFIT accident with many fatalities. But not at that time - the capacity assumed by the "argument" didn't exist yet in 1995. Logically the "argument" addresses most (maybe nearly all) of the accidents involving perfectly flyable airframes via a counter-factual.

What about today, when the capacity is said by some to be at the brink of adequacy? Let's assume it is ready. But what about the other side of the equation advanced by the "argument"? Is it not correct that aviator training, safety management systems, and a variety of related processes have reduced the likelihood of a similar CFIT event to very low levels? Okay, so in some regions or countries, this level of fidelity to training requirements and methods may be less, or woefully less. What makes it true that in a place where a flight crew conducts a flight operation such as the one that resulted in the recent accident in Karachi, that the care and feeding of an autonomous/algorithmic system won't also be inadequate to the task? So the comparison advanced by the "argument" isn't actually valid.

Not least, there certainly still are lots of arguments (no sarcastic quotes this time) about whether the performance and reliability of autonomous/algorithmic systems have or have not reached a sufficient level, in the judgment of professional people with the requisite high level of knowledge and authoritativeness. Or, the jury is still out -- in fact, the court has not even given the jury its instructions yet. (The recent issuance of a position paper by IFALPA on these issues says a lot more than an SLF/atty should try to articulate . . . a thread started on it was moved over to Ground & Other Ops (Safety, CRM etc.)).

It's not just electrical failures. I'm waiting for the algorithmic whiz kids to provide an algorithm that would fly American 191 out of Chicago O'Hare on 25 May 1979, safely. Oh, that's a lousy example, because the faulty engineering of the hydraulic lines, and the maintenance issue with the engine removal and replacement, were unknowns at the time of the flight operation? Right then, and we can therefore be assured that the algorithms and their related processes won't have any errors in their derivation and iteration, or in the upkeep of the overall autonomous system either, I see?

megan
15th Nov 2020, 12:49
American 191 was actually a perfectly flyable airframe, after the engine came off they de-accelerated from 165kn to the stipulated engine out speed of 153kn where upon the left wing stalled, had they not de-accelerated a safe circuit would have been possible. The crew were blameless, they followed the book. Work colleague was on board.

Less Hair, I'd assume a smoking hole rather than the highly successful handling by the crew.

lomapaseo
15th Nov 2020, 13:38
How would a pre-programmed air vehicle, autonomous drone or remotely piloted aircraft have dealt with an electric failure and non normal handling like this?

Pick a flat spot

WillowRun 6-3
15th Nov 2020, 14:27
With regard to 25 May 1979, Chicago, I stand corrected.
Full understanding of discussion of the aircraft systems performance in the NTSB report (middle of p. 51 - 55) is beyond my reach. It nevertheless can be seen that the Board did find the airframe was flyable. I regret the posted error (and meant, positively, no aspersion upon the crew, none whatsoever).
https://www.ntsb.gov/investigations/AccidentReports/Reports/AAR7917.pdf

chevvron
16th Nov 2020, 08:08
morton, all ATC knew was that they had lost radio contact. You don't call out the emergency vehicles for comm failure. Could they see any damage on the a/c? I doubt it.
An AN 124 had a compressor stall on departure from Farnborough once having spent about 10 min on the runway; nothing was said to ATC (I was the tower controller so I should know) and we didn't see or hear anything untoward from the tower (I'm told there was a flash of flame and a bang but it was on the far side of the fuselage from us) but it required an engine change.

ATC Watcher
16th Nov 2020, 08:26
How would a pre-programmed air vehicle, autonomous drone or remotely piloted aircraft have dealt with an electric failure and non normal handling like this?
A total electrical failure on a UAV means the drone is falling off the sky. Happened a few times already .
morton : So, he takes off, doesnít get very high and circles back to the Airfield Ė all in Radio silence. Those in the tower have a terrific view of him coming round, landing and running into the overshoot.
Am I missing something or have they photo-shopped out all the emergency services chasing after this Aircraft during a very non-standard approach and landing?
For ATC , it was a comm failure , nothing else. Happens also sometimes. No big deal in VMC in daylight. . . They did a good job making sure no-one was in the runway and probably send green light signals, and from the APP and the landing touchdown nothing indicated they would overrun in the end. I can see the button pushed only when they saw the snow clouds in the end...

Less Hair
16th Nov 2020, 11:29
The problem is to predict combinations of complex failure scenarios and to have a system ready to cope with it. I see this incident as proof how long we have to go until automated safe commercial flight is possible.
Reality turns out to be different than clean room test scenarios - every time again.

tdracer
16th Nov 2020, 22:54
This is getting silly. If you have a 100% complete electrical on "pre-programmed air vehicle, autonomous drone or remotely piloted aircraft", it's going to crash. Period - end of story.
So, you design the system so that you'll never have a 100% complete electrical failure.
No different than the FBW systems on most new aircraft - if you have a 100% complete electrical failure in your FBW, you're going to have a very bad day because FBW isn't going to work without electrical power of some sort. So you design numerous backups so that it doesn't happen (for certification purposes, that means a probability of occurrence less than once in 10-9 flight hours).

fergusd
16th Nov 2020, 23:38
Finally, someone who knows how to use their brain . . .

Aircraft control systems which are designed around humans USE the human as part of the safety mitigation strategy . . . in the example here lots of stuff fails and the human can still control the aircraft, albeit with reduced performance. This is not a miracle, it's one of the key reasons the human is there is the first place and why the aircraft is designed in the way it is, it's a system, the human is part of it. Increasingly large parts of the non human part of the system are there to stop the human from screwing up . . . in reality . . .

Only a neanderthal would design an automated flight control system without an equally effective mitigation strategy, again possibly with reduced performance. A neanderthal solution would never be permitted to fly and kill people.

Automated control systems are perfectly possible, or very close to it, in the real world, today, The question is . . . is it cheaper to use a human despite their repeated and ongoing failures ?, after all they are cheap, readily available and reasonably good at the job and their failings are relatively well understoof. Are the benefits of fully automated systems justifiable given their likely cost ? Inevitably that cost will reduce, and inevitably the benefits will swing to the side of the machines.

Whether the justification is increased safety or reduced costs (it'll always be the latter despite people claiming it's the former), that change will happen.

lomapaseo
17th Nov 2020, 01:33
This 10-9 stuff doesn't apply to the thread subject event albeit it does apply to some of the preceding expanded subject what-if discussions

tdracer
17th Nov 2020, 18:23
lomapaseo

In a sense it still does - uncontained engine failures are considered to be a 10-7 to 10-8 event. Current airframer guidance for uncontained engine failures is to do what is known as a "one in twenty" analysis - basically showing that the probability that an uncontained failure will do catastrophic aircraft damage is no greater than 1 in 20 or 5%. So that takes an uncontained failure causing catastrophic airframe damage into the 10-9 range.

lomapaseo
17th Nov 2020, 21:11
I believe your 10-7-10-8 is off by a factor of 10.There is no certified standard for anywhere near10-9 as it's impracticable on transport aircraft . As you stated though if you satisfy the regulators idea of good-enough that's then OK..

PAXboy
18th Nov 2020, 19:26
Antonov built that to compete with 1,000 brick ***** houses and it would win. One cannot say that carbon fibre would have swallowed that amount of damage and still be able to make a normal touch down. The overrun due to other equipment failures. Remarkable.

Grunff
19th Nov 2020, 06:46
Fun fact:
Turbine discs always shatter into three 120 degree pie cuts due to geometric/material constrains. So basically, you can calculate statistic probability of one of those piercing trough the something important (and pierce it will, there is a lot of kinetic energy involved). The trick is to move important stuff apart so nothing critical goes offline when severed. DC10 had some issues in that regard.

DaveReidUK
19th Nov 2020, 09:32
It's hard to imagine any material or geometric reason why a turbine disc failure should necessarily involve separation into 3 neat 120į segments. This one certainly didn't:

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/426x316/trent_900_turbine_disc_75799bb68af9ab05763396fe315b90ac6b160 a29.jpg

There may be some confusion with the fact that safety analyses, for certification purposes, around the consequences of an Uncontained Engine Rotor Failure (UERF) are predicated on assessment of the trajectory of a single one-third disc fragment plus (depending on the regulator) a single intermediate fragment and other small fragments.

iranu
19th Nov 2020, 11:07
Just to add to DaveReidUK's comment. The pictures posted of the disc segment with blade roots and 2 damaged blades still attached is a fan disc (LPC) not a turbine disc.

I can't post links, but there are engine schematics for the D-18T online. It's a 3 spool engine with a single stage LPC/Fan. The IPC and HPC use dovetail blade roots, whilst the 3 turbine sections use fir-tree roots. I originally thought the disc segment was the HPT due to those fir-tree roots, but on seeing the remainder of the engine on the wing and a wider shot of the disc segment I concluded that it's part of the LPC/Fan disc. If you look at the 2 damaged blades you can see that the blades lack air cooling (HPT and IPT are cooled on this engine), whilst the blade length and chord are too large to be turbine blades. If you look at the blade nearest the camera you can see that it's fractured along the line of the snubber, again indicating this is part of the fan disc.

We won't know what caused the failure until a full metallurgical analysis is performed, which may be dependent on the missing disc fragment(s) being found.

Turbine disc failure modes are for another topic.

lomapaseo
19th Nov 2020, 14:13
Three equal piece failures are typical only for overstress condition (speed and temperature to a smooth shaped disk. This is due to the conservation of kinematic energy (radial and tangential) before they actually fracture. Little chance of most compressor disks being equally stressed (radial and tangential) or even oversped or overtemperatured. This leave the majority of disk fractures to be split roughly in half with one of the halves splitting over a rough 1/3 section (shock waves in disk after severing the tangential force)

Agree that the assumption of only a single large section of maximum energy (1/3 not 1/2 just do the math) only needs to be considered, The pass fail criteria is then driven by subjective judgements of the FAA against the manufacturers estimates of chance impingements then to be accomodated by shielding (that actually works), separation of critical controls and redundancy (it still flies even though wounded)

The above approximates how one estimates the survivability of military jets to threats

I thought the subject event in this thread did quite well

tdracer
19th Nov 2020, 18:35
To add a bit to what Dave wrote, the 'one in twenty' Advisory Circular guidance (FAA, but EASA also accepts this method of compliance) specifies a 1/3rd disc - with infinite energy. You can't take any credit for shielding for the rotor disc fragments (also known as 'high energy debris'). Smaller bits - such as the blades and blade fragments - are 'low energy debris' and shielding credit can be taken.
There is a defined forward/aft trajectory range for both - IIRC it's +/- 3 deg for 'high energy' debris, and +/- 20 deg for 'low energy' debris (but I stand to be corrected - it's been a while since I worried this).

lomapaseo
19th Nov 2020, 21:27
And I forgot to add that the reason only a single 1/3rd disk section was considered was based on experience both before and after the Concorde program. Naturally if a disk breaks into three equal pieces it leaves a mathematical shortfall.for the other two segments. However the predicted generation of three equal pieces (see above) says that they will leave simultaneously so only one is expected to be aimed at the critical parts of an aircraft (critical is in the eyes of the manufacturer and the FAA)

Lessons learned have now taught us that not every 1/3 section has infinite penetration power. In fan disk failures those 20-30lb fan blade fragments tend to cover a lot more area. Thus don't expect to meet a 1/20 safety rate unless you really can shield against. those fragments. The good news is that most really large engines use Kevlar which has been shown to capture multiple blades from a fan disk fracture.

Somewhere on my hard drive I have all this stuff as it was developed for the FAA to review. In the end they went for the subjective stuff because it gave them something to hide behind

N707ZS
26th Nov 2020, 21:34
The rest of the fleet have been grounded tonight.

tonytales
26th Nov 2020, 22:12
Fan disc that fail are bad enough. Back, I have seen the result of a front bearing internal fire and severing of both the main shaft but also the "fail-safe" shaft releasing the entire fan disc assembly. It was the 22B version (early model) of the RB-211 and the entire assembly marched forward. Being in the Nbr. 2 position of an L-1011 it ate out the S-Duct section, dinged the top of the horizontal stabilizer box below it and came apart just before entering the rear pressure bulkhead. Portside hole in fuselage side was big enough to walk through. Severed three of the four hydraulic systems, fourth had damaged tubing but fortunately was not holed. Eventually, an AD required a system to be installed to detect the first movement of a failing front locator bearing. That essentially, due top cost, ended the 22B engine and sped the retirement of all the L-1011-1 models.
I actually witnessed a disc from a CF6-50 engine roll at very high velocity across JFK airport and end at the then Pan Am ground equipment shop. Came out of an Overseas National DC10-30 on takeoff roll. It aborted, came to a stop and I saw the best evacuation of a burning aiurcraft ever. All aboard were ONA personnel going to support Hah flights. Unfortunately, the fire totally destroyed the aircraft in spite of the efforts of the JFK PONYA firefighters.
Don't believe any protection will prevent whole discs from coming out. Aircraft survival will depend on which way it goes.

atakacs
27th Nov 2020, 01:19
The rest of the fleet have been grounded tonight.

All Volga-Dnepr Airline AN124.

​​​​​

andrasz
27th Nov 2020, 13:15
It's hard to imagine any material or geometric reason why a turbine disc failure should necessarily involve separation into 3 neat 120į segments.

There is some very simple physics why a disc failure will result in three roughly equal fragments, with none substantially larger than 120į (the largest on your example is 130-140į). Failure originates from a single point, with a crack propagating through the entire cross-section. Once the crack is complete, the integrity of the ring is compromised, and centrifugal forces will start to bend it outwards. The maximum stress due to these forces is not at the side opposite to the initial failure, but at the two sides, roughly 1/3 the way, where two more cracks will form. Of course all this happens in less than a millisecond, and things like lost/damaged blades and speed of rotation will determine the exact outcome. Due to interaction with other components the initial pieces may or may not fracture any further, but you will always start out with three roughly similar sized fragments. This also means that only one of the three (or subsequent smaller fragments) will be on a trajectory towards the fuselage. Of course if the bearing fails, and the entire disk goes AWOL, that is a different story.

Less Hair
27th Nov 2020, 15:02
Fascintating science behind it.

lomapaseo
27th Nov 2020, 15:46
and the highest energy piece may be less of a risk to penetrate a critical aircraft structure..There is less worry about 180 degree segment pieces than a 115 degree piece of disk. The smaller the angle section the lower the weight but the higher escape velocity. That works out to a highest penetration range for aircraft structures between about 100-140 degree segments (worst combination of translational velocity and weight) Of course anything really close by is going to suffer from the more numerous smaller fragments

atakacs
27th Nov 2020, 17:09
Any update about Volga-Dnepr ? Concretely what can are they doing about this ? I don't think they have many choices...

krismiler
27th Nov 2020, 21:53
You would need armour comparable to a battle tank to have adequate protection against these failures. The key is to prevent them from happening in the first place and designing the aircraft so that critical components and wiring won’t be damaged if they occur. If this can’t be done, then separate back up systems for the most critical systems need to be looked at.

An emergency means of shutting of the fuel supply at the tank end could be worth having.

kontrolor
28th Nov 2020, 19:10
Just to add to DaveReidUK's comment. The pictures posted of the disc segment with blade roots and 2 damaged blades still attached is a fan disc (LPC) not a turbine disc.

I can't post links, but there are engine schematics for the D-18T online. It's a 3 spool engine with a single stage LPC/Fan. The IPC and HPC use dovetail blade roots, whilst the 3 turbine sections use fir-tree roots. I originally thought the disc segment was the HPT due to those fir-tree roots, but on seeing the remainder of the engine on the wing and a wider shot of the disc segment I concluded that it's part of the LPC/Fan disc. If you look at the 2 damaged blades you can see that the blades lack air cooling (HPT and IPT are cooled on this engine), whilst the blade length and chord are too large to be turbine blades. If you look at the blade nearest the camera you can see that it's fractured along the line of the snubber, again indicating this is part of the fan disc.

We won't know what caused the failure until a full metallurgical analysis is performed, which may be dependent on the missing disc fragment(s) being found.

Turbine disc failure modes are for another topic.

https://cimg5.ibsrv.net/gimg/pprune.org-vbulletin/2000x538/plan_wire_grand_edaeeaf2d1f705a62c5bebc73773a1256e322bf3.jpg


1-Cone leading edge section; 2-Fan wheel; 3-Fan shaft with bearing support; 4-Fan casing; 5-Fan straightener vane; 6-Intermediate pressure compressor; 7-Jet nozzle; 8-Exhaust cone; 9-Rear mount; 10-Rear bearing; 11-Fan turbine; 12-Intermediate pressure turbine rotor; 13-Turbine bearings casing; 14-High pressure turbine rotor; 15-Combustion chamber with hight pressure turbine; 15.1-High pressure turbine nozzle guide vanes; 15.2-Combustion chamber; 16-Thrust reverser; 17-Engine master module; 17.1-Accessory drive gear box; 17.2-Intermediate drive.


source: http://www.buran-energia.com/mriya-antonov/mriya-moteur-engine-consti.php

http://www.buran-energia.com/mriya-antonov/mriya-moteur-engine-desc.php

Gipsy Queen
28th Nov 2020, 23:06
. The smaller the angle section the lower the weight but the higher escape velocity.

But would not the relatively reduced mass of the smaller angle section mitigate the degree of damage promoted by the elevated escape velocity?

lomapaseo
29th Nov 2020, 02:42
Not for penetration, velocities below 1800 ft/s in steel and 1100 ft/s in Alum act about a 3/2 power while mass is only at a power of 1. It's more than energy that gets involved. It also involves shock waves and adiabatic shear. Fortunately Kevlar belts have a whole different mechanism going on at the engine level

N707ZS
29th Nov 2020, 07:42
Have they managed to retrieved the aircraft from the end of the runway.

Chris2303
29th Nov 2020, 20:45
https://simpleflying.com/video-tanks-remove-damaged-an-124-following-crash/

Gipsy Queen
29th Nov 2020, 22:31
Thanks Lom - I imagine that if there were any means of introducing isothermal characteristics to these assemblies, it would have been done years ago.

andrasz
30th Nov 2020, 15:46
Any update about Volga-Dnepr ? Concretely what can are they doing about this ? I don't think they have many choices...

https://youtu.be/-N9JMEOg7Bk?t=107

tdracer
30th Nov 2020, 18:31
Typically uncontained failure issues with existing engines are addressed with a combination of increased inspections and hard time life limits (cycles and/or hours) - usually enforced by AD.
Sometimes there are changes that can be reworked into existing parts (during a shop visit) such as machining an increased radius into a high stress area to improve the crack resistance.

The trick is finding the correct inspection intervals and life limits to prevent future failures. I know this was on ongoing issue with the CF6-50 turbine discs installed on older 747 Freighters. The Feds kept changing (reducing) the inspection intervals and hard time life limits, but they kept failing at the rate of one or two a year right up to the time I retired. Fortunately they never did enough damage to serious threaten continued safe flight and landing, but I suspect if the event aircraft had been carrying hundreds of passengers instead of tons of freight, it would have gotten a lot more attention.

lomapaseo
30th Nov 2020, 19:31
Titanium fan disks separation tend to have material property problems rather than wear out modes. This often can be parsed down by a group within a manufacturing date making it easier on forced inspection to only a few engines in the suspect batch.

Gross material defects tend to fail at half life design cycles and are more often small batch related. Failures at very low cycle counts are extremely rare and unlikely to be manufacturing related.

No idea what this one is, but there are some hints in the photos in post #3 matched with some of the earlier posts in this thread. and you don't need all the disk pieces to confirm where the fracture initiation came from

atakacs
30th Nov 2020, 19:39
tdracer

Thanks. But in this case there is the extra complexity of the D-18T not being produced anymore, not to mention the less than cordial Russia vs Ukraine relations as of late. I know their resourcefulness and I'm sure parts can be sourced but I fear they can not extend the useful life of the current engines indefinitely. I really hope this was a "one off" but somehow doubt it.

lomapaseo
30th Nov 2020, 20:54
Well somebody has to own the airworthiness certificate else the plane can't fly so either an inspection or retrofit is required or the fleet grounded in all countries whether it's a one-off or not

I supposed a more cordial response might be an easy inspection interval since it doesn't carry many passengers

atakacs
30th Nov 2020, 21:05
I'm certainly not the ultimate specialist but I think you will find that things are a bit muddy when it comes to the AN124 & airworthiness certificates...

lomapaseo
1st Dec 2020, 01:20
No doubt, but now that they have rang their bell the countries that permit the flights of this plane may ask for clarification.

atakacs
8th Dec 2020, 08:19
Going for the jugular (https://theloadstar.com/antonov-rolls-out-its-cargo-big-gun-the-an-255-to-fill-in-for-grounded-124s/)

I guess it is fair game.

procede
8th Dec 2020, 09:03
I thought the An-225 uses the exact same engines, but two more. So even more chance of an uncontained failure...

atakacs
8th Dec 2020, 10:03
You are correct. Maybe the Antonov one are "better" maintained (access to parts ?). It is pretty clear that the Ukrainian are trying to make things difficult for VDA (not taking sides here, just stating facts).

Less Hair
8th Dec 2020, 10:27
Does VDA have manufacturer's support?

andrasz
8th Dec 2020, 11:25
It is a paradox situation, because while the design type certificate is held by the (Ukrainian) Antonov Design Bureau, the manufacturing (and heavy maintenance) license is held by the Ulyanovsk Aviation Plant (now Aviastar, Russia), where not surprisingly Volga-Dnepr is based. In the former USSR aircraft design and manufacture was done by distinct entities, the design bureaus had no manufacturing facilities, while factories were only for production, they had no R&D functions. When dealing with operational issues, the customer airlines liased with the manufacturing plant, not the design bureau. It was also the manufacturing plant who issued any Service Bulletins. I'm not privy to what certification regimes apply to the UR and RA registered Antonovs, but I would expect given the 'cordial' relations between the two countries, that completely separate ones.

Less Hair
8th Dec 2020, 11:30
And where would the engine design office and the engine manufacturing plant be legally based at please?

andrasz
8th Dec 2020, 13:03
Caught me there, Ivchenko-Progress is based in Ukraine, and so is the manufacturing plant. Valid OP.

Less Hair
8th Dec 2020, 13:31
Thanks. Very interesting,

atakacs
8th Dec 2020, 16:57
andrasz

But do they still produce complete or partial D-18T ?

andrasz
11th Dec 2020, 14:48
atakacs

According to their website, yes. "In commercial production since 1999"

atakacs
16th Feb 2021, 10:58
Seems Volga-Dnepr is back to limited AN124 operations (https://simpleflying.com/volga-dnepr-four-an-124s-flying/)
Wonder what they actually did / checked on their birds.