787 engine failure in Charleston, SC
 

Surprised this hasn't been posted yet.

Boeing 787 Engine Failure Sparks Fire at Charleston Airport | Aviation International News

"Another Boeing 787 engine problem—this time involving a General Electric GEnx turbofan in an airplane destined for Air India—sparked a grass fire at Charleston International Airport during a pre-flight test on Saturday, forcing the airport to close its main runway for more than an hour. The contained engine failure has prompted an investigation by the NTSB, Boeing and GE, maker of the engine now in service with Japan Airlines on four 787s."

It was - about 12 hours ago - tagged onto the end of the 787/Trent 1000 thread.

Right, don't know why I didn't look there. :O

Engine shaft sheared allowing the complete LPT assy to move aft.......and out:E.
IIRC sheared at the end of the thread where the coupling nut is!
Same thing happened to a 744 with CF6-80's recently too......must be a GE thing.:rolleyes:
And the AC 773 GE90-115 was a failure in the HPT section...hence the bang!
That was an HPT stage one shroud departing company taking everything aft with it!:8

Looks like a similar failure, this time on a 747-8.
Second GEnx Failure Under Investigation By GE
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I suppose the usual suspects will appear on pprune soon enough demanding that the entire fleet be grounded due to Rolls Royce being unable to design a reliable engine...........oh wait, this is an American GE engine. No problem. :ouch:

Not an engineer... Sorry for the intrusion
 

NTSB Urgent Recommendation to FAA : Inspect GEnx Fan Mid Shafts Immediately .

See aviation week :

http://www.aviationweek.com/Blogs.as...c-6bb1d09569bc

And :
http://www.ntsb.gov/doclib/recletter...12-052-053.pdf

Highlights :

- The first failure (GEnx-1B) at Charleston was caused by a fractured forward end of the Fan Mid shaft (FMS), that separated at the rear of the threads.

- The fracture was no fatigue cracking.

- Further examination revealed a faceted, quasi-cleavage fracture morphology that is typical of environmentally assisted cracking of certain high strength steel alloys such as that used on the GEnx FMS.

- A second (zero flight hour) GEnx-1B FMS with a fracture was found during engine checks.

- The investigation into the cause of the environmentally assisted cracking that occurred at both fractured FMSs is continuing.

- The damage noted on the photographs of the GEnx-2B (Shanghai) is consistent with that observed on the engine that failed at Charleston.

- The GEnx-1B FMS is slightly longer than that in the -2B engine. However, the threaded end of the FMS; the manner in which it is clamped with the retaining nut and the assembly procedures, material specifications, and operating environment are similar between the two models. Therefore, the FMS in GEnx-2B engines may be susceptible to the same type of failure observed with the GEnX-1B FMS.

- the NTSB recommends that the FAA require operators to accomplish repetitive inspections of the FMS in all (on-wing and spare) GE GEnx-1B and -2B engines at a sufficiently short interval that would permit multiple inspections and the detection of a crack before it could reach critical length and the FMS.

anyone got any pics of the one in SHA?

Repetitive inspections of spare engines? Let me get this straight, you inspect what is a brand new engine and after a period of time you have to reinspect it because it may have developed a serious structural fault sitting in an engine stand? I wonder how GE is going to make this up to their customers.

Nothing new in how they will probably handle it like any other engine within a warranty period. Typically such warraties are very genereous as specified in a contract with their new product customers.

In other words business as usual (on the business side).

I believe that RR went through something similar a couple of years back as did P&W.

MarkerInbound,

." Because of the immediate threat of multiple engine failures on a single aircraft and the availability of an appropriate inspection procedure, there is an urgent need for the FAA to act immediately."

NTSB...

The threat would appear that the crack can progress without load, withut even being on wing. It is "environmental" in nature, the report claims that the steel used in this Fan shaft is susceptible to atmospheric Hydrogen causing an accelerated galvanic corrosive propagation of cracking. They also are cautious that ETOPS is affected, should the shaft fail, and the remaining engine may be subject to 5.5 hours of operation OEI.

This would appear on the face of it to be at least as problematic as the RR TRENT problem with spline wear at the shaft efface.

The link is instructive... and direct, no soft pedalling, as it should be.
regards

[quote
The threat would appear that the crack can progress without load, withut even being on wing. It is "environmental" in nature, the report claims that the steel used in this Fan shaft is susceptible to atmospheric Hydrogen causing an accelerated galvanic corrosive propagation of cracking.][/quote]


Is GE building engines out of chinese pot metal these days? How could the engineers possibly have missed this?

To be clear, the "NTSB" is quoted for the first statement. The second statement, without quotes, is mine. It is a paraphrase. Sorry if it appears as though part of the pdf.

It isn't the single metal, it's the plural of metals and an electolysis link between them. Things like coupling nuts, multiple shaft materials oils, etc. in a small compartment. The rate of corrosion is highly subjective. the fix is typically protect the metal (coating) and/or change the material.

I suspect that there are quite a few other examples in the literature.

"While none of the parties involved are able to confirm this, a statement from GE that it has introduced an “improved coating process to the mid-shaft of new-production GEnx engines” would appear to define this as the most likely cause."

Near new, and yet to be mounted engines are in failure? Not Stress, or fatique?

lomapaseo, can you provide several examples of this in the literature?

Since threads are not ordinarily "coated" but need to efface each other clean,
the fix appears to be impossible as described. Perhaps the nut and threads are encapsulated with an applied coating. Not familiar.

Lomapaseo,

That's what I was implying, if airlines have to ground their brand new planes, GE is going to have to throw tons of money at them to keep the airlines happy. Not good for their bottom line.


Lyman,

I understand the urgency, I've made three legs in a -8. I'm just amazed that GE could create and have certified an engine with such issues.

Howdy...

Which -8? There are two values for urgency, one involves 25% of the available thrust, the other 50%...

Hydrogen embrittlement seems a likely candidate given the described failure mode.
Here is the Wiki on that: Hydrogen embrittlement - Wikipedia, the free encyclopedia

I can remember some large spacer washers on the McDonnell F-4 that kept the stabilator centered on the fuselage. These things were way overdesigned to look at them, but they were failing in service because they didn't have the hydrogen driven out of the metal following plating operations. (Improper process specification) You could tell when one failed because the stabilator would then scar the side of the fuselage as it moved. Those massive washers behaved as if they were made of glass!

I thought the short hand -8 only applied to the 748. The eighth product from Dehavilland of Canada has always been Dash 8.

Hi

From NTSB....

"On July 28, 2012, a Boeing 787-8 airplane experienced a loss of thrust in the right engine—a General Electric (GE) GEnx-1B turbofan, engine serial number (ESN) 956-121—"

First I've seen that id, but whatcha gonna do?

Boeing changed things with the 787 and all subsequent aircraft so far. It is now just -8/-9 whatever. So far that is true for the 787, 747-8 and 737 MAX.

Boeing Marketing changed to -8, -9 etc.
However, once you really buy the aircraft, you get your full 3 digits.
For example ANA is not operating 787-8, but 787-881. Lufthansa is not operating 747-8 but 747-830. Just the same since 50 years, but marketing needs something new now and then to justify their existence...

Machinbird:
It's a known issue going back a few decades before the F-4. After cleaning & replating R-985 pushrod-cover gland nuts (Cadmium plate, no less) we always baked them a couple hours to remove hydrogen entrapped.

I'm not so sure about that. It's certainly true of the 747 - you will find the -830 series designation, for example, on the Type Certificate.

But for the 787, the only certificated variant (as of yesterday's update to the TC) is the -8, with no reference in the TC to individual customer numbers, which suggests that for this aircraft those are purely marketing and/or Boeing internal designations.

barit1

In your experience, can the plating process be reversed, the stock re cooked, and then replated? If Hydrogen is entrapped, the fissures have already started, and there is possibility for continued embrittlement, post re-plate?

In one description of the failure, there was reference to "Facets" in the degraded areas. This suggests a propagation of fractures at the level shy of inspection at .05 inches?

This is eerily similar to the Shaft problems RR had in the TRENT, perhaps....

What I find interesting is that these problems show up in products from main-line manufacturers with decades of experience.
I guess that Boeing and GE can breath a sigh of relief that their overly ambitious production rate has still not happened.
f

The aah, joint is aft of the hotter, faster bits right? Tell me it is....

Lyman -

Sorry, don't know the answers to these. Regarding the baking process, we baked the parts within a few hours of plating - we heard it was time-critical.

I have been a little reluctant to comment on these failures, not knowing for sure what the cause might be. It does appear, however, Hydrogen Embrittlement (HE) may indeed be the cause. In recent newer GE engines (CF6-80C/E or newer), the LPT shaft connects into the Fan Mid Shaft as described by BadgerGrowler. I believe the FMS is made of Maraging steel and the LPT shaft of a different high strength steel. Maraging steel is somewhat sensitive to HE like normal high strength steel and it is only used because of its high shear strength and grain size does play a role in HE. The HE may come from factors in the manufacturing process or raw material (alloy) production, not as a result of operating service. Higher strength is developed by heat treatments but comes at the expense of ductility. Corrosion resistance is also reduced. Typically, high strength steels becomes HE sensitive when heat treated to give tensile strengths above 130,000 psi, perhaps higher for Maraging steel. The part must be subjected to tensile stress as would be the case of a forged shaft. Shafts do not need to be assembled or in service to be under tensile stress. The heat treating process provides most of the residual stresses. Manufacturing processes that utilize acids or electro-plating introduces hydrogen into the part material. I think shafts are electroless plated or vapor deposition coated to prevent corrosion in service.

No matter what, there is a process as barit1 described as "baking". And as he pointed out, parts must be baked within 4 hours of hydrogen exposure, less is better. Parts must be baked at 400℉, and parts must be held at 400℉ for a minimum of 4 hours, longer depending on thickness or size. If the baking process is not done properly, parts can be sitting on the shelf and can begin to show signs of HE. 70% of aerospace components that fail because of HE are related to improper "baking", one or more of the steps outlined above. Since "baking is a batch process, that is more than one component per batch, if one is bad, you can bet the farm that all the components in that batch will be bad. And this takes us to the GE situation.

Boeing essentially put out an original schedule for aircraft build for both the 787 and the 747-800 series. GE, in turn ordered parts to that build schedule, placing orders for long lead time parts first. Then technical issues at Boeing resulted in long delays/postponements for the need of engines. So the engine parts were on hand or partially processed when new delayed schedules for aircraft builds were announced. I am sure they sat on the shelves until needed. Meanwhile, the engine testing and certification programs went on and engines were delivered for flight testing of both aircraft models. IMHO, this is why the problem wasn't discovered during the normal certification process, just an opinion/speculation. Nevertheless, the delay in the program may have hurt rather than helped.

So if the problem is indeed HE, the NTSB AD to GE is to find the rest of the shafts from that "baking" batch or alloy batch ASAP assuming the "baking" process or alloy batch might be the cause. Either way, it would be traceable.

Lyman,
The joint of the LPT shaft to the FMS is not in the hot section of the engine.

TD

Thanks TD, always appreciate your data. A couple questions though, can you be more specific re: the Plating? You mention 'electroless', I am unfamiliar. Also, by vapor, do you mean plasma or powder coat? I like the explanation of the difficulties GE faced due the assumedly schedule busting resin/spinning process.

Also, you mention the "NTSB AD". The NTSB is not a rule making body, but can recommend only. There is an AD? I could not find it in the FAA site. The NTSB does not write drama, and their concern is clear, there would have to be an AD at some stage, lest the "Optional" brigade start to drag their paws on the ground....

My concern for the location of the joint came about when I read that "The shaft migrated aft, and caused clash with the stators, etc."

We have been down that road, my perplexion comes from any possibility of uncontainment of an explosive nature?

thanks again.

So long as the turbine rotor/stator geometry is designed so that a rotor axial shift creates a clash of airfoils, it's a "fail safe" design. The rotor will never get the chance to accelerate to a dangerous RPM. This is apparently what has happened in the GEnx failures; the low-energy airfoil debris exits through the core nozzle.

However, even this "benign" shrapnel can create a flight hazard - for example, if hydraulic lines are routed within the horizontal stab LE. A thorough FMECA is the answer here.

(FMECA = Failure Modes, Effects, Criticality, Analysis)

NTSB press release
 

ala PA A310 Hamburg

September 18, 2012, 2:52 pm


AINonline is reporting that GE will use "additional Lead" in the formula for the coating that's expected to prevent corrosion on the FMS thread area. GE reduced Lead in the formulation post GE90, to "protect" the Environment from the deleterious effects of Lead. Nice thought. Now, not so much.

Let's hope that a new EIR is not required, Pesky EPA...

Still nothing regarding a forthcoming AD, other than some sources are saying inspections are "required" (can't happen w/o AD). A Seattle paper is reporting that the Manufacturer is "requested" to inspect...

The operator, Atlas, is saying they are "looking at" the request... Atlas is the only carrier under the jurisdiction of the FAA, supposedly.... (AINonline)

From a practical standpoint, an OEM mandatory service bulletin (SB) has nearly the same leverage as an AD - in that the manufacturer's warranty may be denied if the operator fails to comply with the SB requirements.

And a strongly worded SB will likely hit the street before FAA can process an AD. :ok:

Hi barit1

I agree, but I also think it is one thing to face the loss of Warranty, and another thing the loss of an aircraft. The willful evasion of an AD is (can be) a criminal offense.

I am concerned at the lackadaisical attitude of the 747-8 operator. Two incidents of brand new engines spitting their guts out into the slipstream. Smoke/fire.

Lyman,

On September 17 the GE spokesman told AIN that all GEnx engines in the field would have undergone inspection by the time the FAA issued its AD this week. The inspection is accomplished on-wing, no need for engine removal unless something is detected.

BTW, electroless plating is a process method of usually applying nickel to a component that has experienced wear, restoring the surface and dimensions to the original limits. Relative to vapor deposition, I am not sure of the exact process used. Since shafts are hollow, the coating is applied to both OD and ID to minimize corrosion from oils, etc., that are vented through the shaft interior.

TD

Once again, TD thanks for the update.

My concern would be that the shafts were cooked in 'batches', and that the cooking is the required step for excluson of atomic Hydrogen. Since the Hydrogen is a result of a galvanic process, (dissimilar metals), what is the assurance that a field negative exonerates the batch? The additional ingredients involve a humid environment (prevalent), and the location at a machined in situs, (thread root). The fix per AIN is Lead formula coating, not plating, so how is the initial plating tested? The ultrasonics, per GE are only resolved to .05 inches. That is a rather large fissure, and less than that threshold leaves rather a lack of confidence, imo. So then we find that the inspections are recurring at short intervals, to protect the client from fracture and failure. Can this engine be field stripped, like the TRENT and its fifteen modules profile? I am having a time of it, picturing how any effective coating can be applied in the field, without strip. Then there are the threads.

Do you know if the threads are coated prior to join with the FFS? The suspect area is the root of the termination of the helical cut made for the thread in the shaft, again, that seems quite the challenge to "view" on wing....

Thanks TD

Lyman,

You are asking questions that can only be answered by seeing the failures first hand, and the failure analysis that would follow, besides knowing in detail the actual complete processing steps. I don't have this information to answer your questions.

TD

Among others, that is a point I am trying to make. This problem is not complex, nor is it worthy of the shadow people are trying to hide it behind. It has to do with the safety that is currently under attack in our industry.

If someone of your professional calibre is in the dark, we all are.

And that is no place to put the people who pay for the equipment, and pay for the agency that is supposed to protect us from the shadows.

A little sunlight would be a good thing.