777 fan-blade / cowling failure over Denver

[Evan]

Like I said!

I’m not having a blast. Unless that was just a pun.

[BoeingBobby]

I’m not having a blast. Unless that was just a pun.

Just wondering, is this Boeing's fault? Should someone loose their job in management for this?

[Evan]

Just wondering, is this Boeing's fault? Should someone loose their job in management for this?

Stupid but interesting question. The 777 was the last of the old-school Boeings, before Boeing was left in the hands of a cynical capitalist leadership focused blindly on short-term shareholder value. How many 777 incidents have occurred as the result of deficiencies in the airframe or avionics? The 777 was Boeing at its best. So when you want to goad me over my disgust regarding what Boeing has become, keep in mind that aircraft like the 777 are what I came to expect from Boeing.

[Evan]

P&W is another story. This was not the first PW4000 to suffer a fan blade / cowling failure, nor was it the first one to do so when bound for Hawaii. The lessons learned from the prior incident pointed to a training failing on the part of P&W regarding their TAI inspection process.

P&W developed the TAI inspection process in about 2005 to be able to inspect the interior surfaces of the hollow core PW4000 fan blade. P&W in keeping with NDI industry practice when implementing a new inspection process classified the TAI as a new and emerging technology and therefore did not have to develop a formal program for initial and recurrent training, certify the TAI inspectors, or have a Level 3 inspector on staff, as is done in other established NDI techniques. But in 2015, and still in 2018 when the incident occurred, P&W was still categorizing the TAI as a new and emerging technology after having inspected over 9,000 fan blades. At one point, P&W did provide training on the TAI, however, neither of the two inspectors were permitted to attend the training so that they could work to clear out a backlog of blades in the shop.

There was also an AD involved:

On March 22, 2019, the FAA issued Airworthiness Directive 2019-03-01: Airworthiness Directives; Pratt&Whitney Division, Turbofan Engines to require an initial and recurring TAI inspection of PW4000 hollow core fan blades.

So it will be interesting to see about compliance on this a/c.

https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/bb315c3fce9e8c75862583a2005079f0/$FILE/2019-03-01.pdf

[BoeingBobby]

P&W is another story. This was not the first PW4000 to suffer a fan blade / cowling failure, nor was it the first one to do so when bound for Hawaii. The lessons learned from the prior incident pointed to a training failing on the part of P&W regarding their TAI inspection process.



There was also an AD involved:



So it will be interesting to see about compliance on this a/c.

https://rgl.faa.gov/Regulatory_and_Guidance_Library/rgad.nsf/0/bb315c3fce9e8c75862583a2005079f0/$FILE/2019-03-01.pdf

What was the title of this thread again?

[TeeVee]

so the FAA ordered inspections. i guess they learned their ass-kicking lesson with MCAS.


"Since entering revenue service in 1987, Pratt & Whitney has delivered more than 2,500 PW4000-94 engines that have collectively logged more than 120 million dependable flight hours on commercial aircraft around the world."

120,000,000 hours and what, 5 failures? none of which resulted in loss of life or hull? that is pretty damn reliable

[Gabriel]

so the FAA ordered inspections. i guess they learned their ass-kicking lesson with MCAS.

Not only that, but United grounded their 24 777s with PW4000 (which I believe are all the 777s with PW4000 operating in the US) and Japan's aviation authority grounded the 777 operated in the country, of which are 32 between JAL and ANA. Apparently that's most of the 777s with PW4000 in existence world wide. According to a news report I saw in YouTube the remaining ones are all in South Korea.

So the question now is... If 2500 PW400 were delivered and only less than 100 777 with these engines are out there (which would account for 200 engines), where are the remaining 2300 engines and why wouldn't these planes be affected too? Can be this type of failure be airplane-type specific?

[Evan]

So the question now is... If 2500 PW400 were delivered and only less than 100 777 with these engines are out there (which would account for 200 engines), where are the remaining 2300 engines and why wouldn't these planes be affected too? Can be this type of failure be airplane-type specific?

The two issues that I believe are at fault are the inspection process for the hollow core titanium blades used on the PW4000 and weaknesses in the CRFP rear bulkhead and engine cowling structures. Inspectors may not be properly trained on the thermal acoustic imaging technology developed to inspect the new blade design. The engine was also fan blade out certified using an aluminum rear bulkhead instead of the CRFP one used in production.

Because the aluminum versus the CFRP structure has the ability to yield while absorbing the same amount of energy, it can redistribute the FBO loads between the fan case and the inlet without causing failure to the inlet, or the fan case to inlet interface. The inlet and fan cowl structural analyses showed that the CFRP aft bulkhead design was less capable than the aluminum bulkhead that was tested during engine certification test and determined that multiple possible scenarios could have led to their separation; 1) the inlet aft bulkhead load path damage caused by the unanticipated magnitude of the displacements induced by the displacement wave following the FBO combined with the anticipated inner barrel fragment induced damage progressed under rundown loads, resulting in portions of the inlet departing within one second following the FBO, 2) the departure of portions of the inlet including the lower aft bulkhead caused the static and/or dynamic loads to increase beyond the fan cowls capability, that lead to the departure of large portions of the fan cowl, 3) the fan cowl honeycomb core strength was reduced below its capability to react rundown loads due to moisture ingression at the hinge points leading to large portions of the fan cowl departing prior to the inlets departure.

So why would they certify the thing using different materials than the ones to be used in production?

Although it is necessary to install an inlet for proper engine operation during these tests, it is not required that this inlet meet production standards. The test inlet used was of a different design which included an aluminum aft bulkhead instead of the production CFRP aft bulkhead. Additionally, these tests are conducted without the fan cowls attached. The inlet and fan cowls are certified under FAR Part 25 of which Boeing was responsible for.

So dumb bureaucracy strikes again. Is this a 777-specific issue?

Fan Cowl Moisture Ingression Damage
Boeing records indicated that evidence of moisture ingression had been found on multiple other 777 fan cowls, and although varied in extent and location, was on some occasions reported in the area of the latches on the lower fan cowl panel and the area of the hinge attachments. Such moisture ingression would degrade the allowable strength of the cowls. Although the event fan cowls were not recovered to verify the presence of moisture ingression, it is possible that this type of degradation existed and contributed to the fan cowl separation.

Fan Cowl Instability
The analysis indicated that large fan cowl deflections may have been induced following the departure of portions of the inlet. The forward portion of the fan cowl would no longer be capable of remaining engaged after portions of the inlet and the lower aft bulkhead departed the airplane. As a result, the fan cowl to no longer maintain its shape when subjected to the engine imbalance loads and buffeting from air loads. The large panel deflections could have induced internal stresses that were in excess of those observed during certification and exceeded the capability of the fan cowl panels and latches.

These appear to be 777-specific issues. The large -112 variant fan section of the PW4000 is only used on the 777. So maybe....

But the blade inspection issue can't be specific to the 777. It wouldn't surprise me to learn that this issue was also behind the recent Longtail 747 PW-4056 incident.

Remember, these issues were identified in the final report for DCA18IA092l issued in July of 2020.

There was no grounding at that time.

[TeeVee]

So the question now is... If 2500 PW400 were delivered and only less than 100 777 with these engines are out there (which would account for 200 engines), where are the remaining 2300 engines and why wouldn't these planes be affected too? Can be this type of failure be airplane-type specific?

according to PW: A300, 310, 330, 340, MD11, B747, B767.

only the PW4000-112 is used exclusively on the 777

[Evan]

So the question now is... If 2500 PW400 were delivered and only less than 100 777 with these engines are out there (which would account for 200 engines), where are the remaining 2300 engines and why wouldn't these planes be affected too? Can be this type of failure be airplane-type specific?

This from the Seattle Times:

FAA Administrator Steve Dickson...said his agency’s experts “concluded that the inspection interval should be stepped up for the hollow fan blades that are unique to this model of engine, used solely on Boeing 777 airplanes.”

The good news is that prior to both of the previous 777 blade failure incidents, the metal fatigue was detected by the inspectors. The problem was that, lacking proper training in the thermal acoustic imaging process, they both attributed these to paint defects and returned the blades to service. Therefore, inspections by properly trained personnel can quickly get these planes safely back in the air. But then then the FAA must require that the inspectors are properly trained in the future.

The other issue, the CRFP bulkhead and cowling issues, are another story.

And what about that Longtail 747...?

[3WE]

Blah blah blah moisture cowling blah blah blah

What are the odds that cowling stuff broke the blade vs the blade breaking the cowling?

That intake ring sure looks pristine. The new owner better hide it before using it for a raised bed flower garden...officials may want to examine it.

PS: Disappointed at the new thread title.

[Evan]

And what about that Longtail 747...?

Best I can tell, only the -112 designed for the 777 uses hollow-core fan blades that require the TAI inspection process. (The 1000G also uses the TAI inspection process. The GP7200 used on the A380 also uses hollow blades but they are all too new to require the TAI process). Still looking into this...

But this is looking bad for P&W:

To do the TAI, the only training the inspector received on the PW4000 blades was OJT [on the job training]. The company still does not have any formal training for the PW4000 fan blades.

and...

The TAI training that [the inspector] received never provided any reference material on what to look at. He was provided with some photos, but he said that they were very distorted.

Now, we are not talking about training hundreds of personnel here. P&W had only THREE inspectors to train for these blades, and one of them was a backup.

The one involved in the 2018 failure was the second shift inspector. He was VERY experienced and qualified on many processes (he even worked on the space shuttle main engines). But he wasn't properly familiarized with the new TAI process.

The issue was paint. Before the TAI inspection, the blades must be painted. The paint is then removed following the inspection.

The paint they originally used back in 2010 was good, but it would flake off when the humidity was high. They changed paint vendors and the paint was better, but they couldn’t do anything with it. The paint was very fragile and could be removed easily. They would then have to send it out to be repainted. If he saw an indication, he would get his drop light and do a visual inspection to see if there was anything in the paint such a piece of grit that got into the paint or if the paint gun had spit out a droplet.
He thought he could do about six to eight parts a shift. Sometimes he operates both machines and he could do 12 to 14 blades per shift. He had never seen a blade where every image was a pass. Back in the 2015 timeframe, most of the images were marked as fails. Now, they are getting that down to about 10 to 12 fails on a fan blade.

There was pressure. At the time, P&W was trying to clear a backlog of blade inspections.

On the incident fan blade, he could not recall marking the sheet that it was a paint issue. He had marked off the indications as edges, background, and noise. He thought the noise could be paint. Since they didn’t have any guidance, he would list what he thought the indications were.

The report cites everything from the rather shoddy painting process to the lighting issues in the inspection facility.

He could not recall ever seeing an FAA inspector in the shop.

It's a pretty damning report. Perhaps more damning as it was released in 2018. Read it:

https://data.ntsb.gov/Docket/Document/docBLOB?ID=40468232&FileExtension=.PDF&FileName=Powerplants%20Group%20Chairman%27s%20Factual%20Report-Master.PDF

[BoeingBobby]

Disappointed at the new thread title.

I didn't do that! Interesting, who did it and why?

[Nervous_Flyer]

Makes me glad planes do not fly over my house on takeoff. And my insurance company might be equally glad. Wow, those things sure "share" a lot of their parts with unwilling recipients.

[BoeingBobby]

Just got these from a friend that works for United.