Broken/missing turbine blades

[jolihokistix]

Japan Airlines 777 engine fire. 200 turbine blades broken or missing?
https://www3.nhk.or.jp/nhkworld/en/news/20170908_06/

Video may disappear in due course.
Quote:
"Japan Airlines has been conducting emergency inspections of 12 aircraft equipped with the same model of engine as the one that caught fire on a passenger jet earlier this week.
Fire broke out on the left engine of the Boeing 777 shortly after it took off from Tokyo's Haneda Airport on a flight to New York on Tuesday. The plane made an emergency landing at Haneda. No one was injured.
More than 200 metal turbine blades of the engine were determined to be broken or missing. Japan Airlines began the emergency inspections on Wednesday. Its officials say the focus is on areas near engine turbines.
They add they expect to finish the work by Sunday and that flight operations will not be affected."

[PDR1]

Sounds like an over-fuelling during spool-up from low speed (or when trying to recover a stagnated engine by pushing the power lever to full chat). That will generally take out most of the HP turbine if done roughly.

[SMT Member]

In a FADEC controlled engine?

[DaveReidUK]

Notwithstanding Avherald's report that it was a B773 (JAL's are PW-powered), it was one of their -300ERs (GE90-115B with the FADEC 3).

[jolihokistix]

Of 112 fan blades of the fifth stage in the low-pressure turbine of the No 1 engine, and 110 in the sixth, i.e. 222 in all, the majority were either broken or bent. Also a hole measuring 4.5 cm x 0.5 cm was discovered in the lower part of the turbine gear frame.

[underfire]

another 777 engine issue?

[lomapaseo]

This kind of stuff use to happen weekly somewhere in the world. Walk the edges of any major airport runway and you can find turbine blade pieces still in the grass.

It's like going to any major street intersection and you can eventually build a car from the pieces left behind from fender benders

[India Four Two]

The other day, I was checking JAL’s website for fares and I saw this link, before I had seen the news anywhere else:

https://www.jal.co.jp/en/info/inter/170906.html

Kudos to their PR department.

[avionimc]

Any information if it was a similar problem causing the engine shut down and emergency landing in Iqaluit of the [almost new] Swiss B777?

[Chris Martyr]

I have absolutely no insider information as far as JAL matters are concerned , but it may be interesting to see what ACMS type data shows up in the preceding weeks regarding EGT's , FF and N1/N2 figures for that particular engine.
Crack propagation in the combustion liners have in the past caused the FADEC to schedule more fuel in order to achieve the same N1 as the healthy engine.
It gets to the stage when the combustion liner lets go completely and ends up taking a few turbine blades with it as it all exits out of the jet-pipe , along with a bl**dy great flame.
This of course conjecture , but also a possible and quite likely cause.

[pax2908]

In that case careful monitoring of these parameters may have allowed to detect the failure earlier?

[Chris Martyr]

I cannot offer any sort of opinion upon JAL's engineering policies/procedures and as stated previously , this is only conjecture.
All I will say though is , one of the good things about gas-turbine engines is that when they don't feel well , they normally give a few prior , subtle hints .

[tdracer]

Chris is right, most major engine failures give ample warning - such as step changes in rotor speed or EGT - if someone is paying close attention to the data. The engine manufacturers have proprietary monitoring programs that chart engine health (based on such things as ACMS reports, or in the case of the newest engines on the 787/747-8 use downloaded data from dedicated engine monitoring systems that record data from start up to shutdown). If used, they can alert the operator it's time to get the engine off wing ASAP.
Many, many shutdowns have been prevented by these systems - however they are not perfect, and worse many operators don't bother to pay for their use (often a classic case of penny wise, pound foolish). No idea about JAL...

BTW, shedding a large number of blades is not uncommon when something large lets go upstream - not only do you have whatever let go, it creates debris as it hits blades which then creates more debris as it hits other blades. I once saw a picture of a PW4090 that had completely "corn cobbed" the spool (LP I think, but it was 20 years ago) - there wasn't an intact blade remaining on the turbine...

[Turbine D]

In the olden days of the CF6-6 engines, the HPT blades were paired airfoils, left hand, right hand if you would, each containing half the root fir tree structure. They were then brazed together forming two airfoils per turbine disk slot. Often, if there was a blade failure in the airfoil, it wasn't detected until inspection for metal in the tailpipe after the LPT did a good job grinding the failed airfoil up. There was no detectible vibrations that gave a clue there was a problem in many instances.

[lomapaseo]

Upstream compressor failures may lead to downstream burning of turbine blades but rarely progress debris damage to break blades in the turbines

However something letting loose in the low spool of the turbine may indeed cascade all the way to the back stage and then spit most of the debris out the tailpipe.

I haven't seen anything so far in this event as high energy particles escaping but the repair costs alone make it serious.

[Chris Martyr]

I am certainly not saying that you are wrong lomapaseo , although I don't believe that compressor blade failure in itself to be that likely to have caused all these turbine blades to have been spat out.
Compressor related problems can stem from VBV and IGV linkage failures , or most commonly , a 10lb meat and feather bomb finding its way in and causing a compressor surge , but these wouldn't necessarily cause major damage to the HP/LP turbine blades.
Anyone who has worked good old P&W JT-9D's will know that you can get a compressor surge by just looking at the bloody thing , afterwhich , once the engine has ceased rocking on its pylon and scaring the cr@p out of everyone in the vicinity , they just carry on turning.
I am still putting my money on a "rattly" combustion liner though.
But remain fully mindful of the fact that this is all speculation. Albeit very balanced and professional speculation.
With view to tdracer's location , he may be the guy who gets first dabs at the real cause.
Was out at Everett WA in '01 doing pre-delivery insp. on a B.744 for an English airline with silver fus./red tail and loved the Boeing guys "can do" attitude to everything..:ok:

[tdracer]

With view to tdracer's location , he may be the guy who gets first dabs at the real cause.
Not any more, I retired late last year (and enjoying it :ok:).
Now I'm just an interested spectator with a lot of background information :E

[Vessbot]

Keep in mind that with a translated article from a general media source, it's anybody's guess whether the compressor or turbine blades are what's actually being talked about.

Even native English-speaking pilots far too often think that "turbine" means "round thing with blades that spins."

[Chris Martyr]

You're spot-on there Vessbot.
We've all seen press reports that have absolutely nothing to do with what actually happened. Especially where aviation is concerned.


It is though , interesting to speculate and try to see if we can pre-empt the "experts".


Main thing is that we remain objective , balanced and above all,,,friendly toward each other when proffering forth our own "massively expert" opinions.


There is indeed a load of garbage written on some forums , but I always try to see forums as a platform for good and positive inputs..:)
and look forward to reading the findings of this JAL incident.

[DType]

When I changed the turbine blade design, and consequently over-fuel was required to achieve normal revs, the blades stretched and departed radially, none were bent (single stage turbine).
I've still got the bits!!!

[Buster15]

So the redesigned blades failed due to creep?
From what little you said was the redesigned blade less efficient such that they were required to hotter to achieve the required rotating speed ?

[DType]

Yes, we ran a thick wire through each blade at mid height, all the way round, to damp out vibrations by friction damping. I beefed up the blade to compensate for the loss of cross section at the hole, and for the extra CF load from the wire, but no one realised until after the big bang (on the test bed) that extra fuel/heat would be required because the wire lowered the turbine efficiency. Hindsight is 20/20 vision.