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United B777 engine failure

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United B777 engine failure

Old 22nd Feb 2021, 19:00
  #141 (permalink)  
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According to CBC news (Canada Broadcasting Corp):

“Boeing said there were 69 777’s with the PW 4000-112 engines in service and another 59 in storage. United is the only U.S. airline with the engine in it’s fleet, according to the FAA, and it had 24 of the planes in service. Two Japanese airlines had another 32 in service.”


Last edited by hr2pilot; 22nd Feb 2021 at 19:16.
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Old 22nd Feb 2021, 19:39
  #142 (permalink)  
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Originally Posted by Una Due Tfc View Post
Okay so if we’re talking semantics, the pressure vessel was left intact (that we know of), but the fuselage was still penetrated.
It worries when people are so determined to downplay, generalize. Safet first? Clearly an uncontained engine failure that could have hit the cabin too.

A quick search showed there were Pratt 777 blade seperations in 2018 and 2020 also. So Japanese authorities pulled the plug and then FAA and Boeing.

Would love to see Boeing/FAA take innitiatives to ensure safety after incidents, instead of denial and only look bold when things became inevitable.
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Old 22nd Feb 2021, 19:51
  #143 (permalink)  
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Old 22nd Feb 2021, 19:56
  #144 (permalink)  
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Jet Engine Explosion Over Denver Rings Alarms About Shielding
By Alan Levin
February 22, 2021, 2:20 PM EST
  • Damage to front of engine was similar to fatal 2018 event
  • NTSB has called for review of engine design in prior failures

The mid-air disintegration of a jet engine over suburban Denver Saturday is the latest in a string of failures that has raised alarm among regulators about debris evading shielding that’s supposed to keep broken parts from hitting aircraft.

The incident aboard the United Airlines flight 328, which showered neighborhoods with metal debris, appears to have been the fifth in five years in which a fan blade broke and destroyed the front section of the engine, according to accident reports and safety experts. That portion of the engine isn’t as protected as the core areas around the jet turbines that are built to contain material in a failure.

“It’s getting more attention with each fan-blade-out event, resulting in these dramatic pictures showing the core of an engine hanging from a wing,” said Jeffrey Guzzetti, the former head of accident investigations for the U.S. Federal Aviation Administration.

No one was hurt in Saturday’s incident and the Boeing Co. 777 safely landed. But a similar episode above Pennsylvania in 2018 killed a woman on a Southwest Airlines Co. jet after a metal chunk from the engine struck the window where she was seated and sucked her partially out of the jet.

On Sunday, regulators in the U.S., Japan and elsewhere said they are concerned that a crack on a fan blade in the Pratt & Whitney PW4077 was allowed to grow to the point that caused it to break off, triggering the failure. They ordered emergency inspections on the hollow titanium blades, which effectively grounded several dozen older 777-200s. Pratt is a division of Raytheon Technologies Corp.

The PW4077 front fan section, which is more than nine feet (2.7 meters) wide, spins at several thousand revolutions per minute, so a broken blade can cause extensive damage to the mechanism and nearby structures.

The failure raises questions about engine designs that are supposed to prevent debris from escaping out the sides of an engine when a fast-spinning fan blade fails. The FAA told the NTSB last year that it planned to order a design change to prevent such incidents, according to a previously unreported letter last year to the NTSB.

“We are working with Boeing to ensure that the corrective action, in the form of a design change, will address the most critical fan blade impact locations,” FAA Administrator Steven Dickson said in a March 9, 2020, letter.

Both FAA and the European Aviation Safety Agency are conducting reviews of their aircraft certification rules to determine whether the standards for engine and aircraft design need to be updated, they have each told the National Transportation Safety Board. The safety board recommended such a review after its earlier investigation of the Southwest fatality.

Engine manufacturers go to great lengths to demonstrate that a broken fan blade won’t shower a jet with dangerous shrapnel. Modern turbine engines are encased in Kevlar to prevent high-velocity debris from escaping to protect vulnerable fuel tanks, equipment and passenger areas.

But the guiding theory in ensuring safety was that blades and other debris wouldn’t bounce too far forward through the onrushing air. As a result, the curved structure at the front of the engine -- known as a nacelle and engine cowl -- aren’t built as strongly.

The five recent events show that debris can, in fact, damage those areas. The result is that the existing engine standards have a gap that may not offer adequate protections during violent fan-blade failures, said a person who has participated in accident investigations. The person wasn’t authorized to speak about the issue and asked not to be named.

The issue has been getting quiet attention in recent years, but Saturday’s highly publicized failure over Denver -- in which videos on social media showed a burning engine beneath the wing and metal chunks thumping to the ground -- means “it’s now reaching a crescendo,” Guzzetti said.

The United plane was headed for Hawaii and was certified to fly long distances on a single engine over the ocean. But heavily damaged engines cause more drag, raising questions about what might have happened if the failure had occurred hours from an airport, he said.

In 2016, a Southwest jet was forced to make an emergency landing in Pensacola, Florida, after suffering a similar failure. Parts of the left engine broke apart, damaging the fuselage, wing and tail, the NTSB found. The plane lost cabin pressure and passengers had to don oxygen masks.

That engine was made by CFM International Inc., a joint venture between General Electric Co. and France’s Safran SA. They power the popular 737 Next Generation family of airliners.

A similar situation occurred on another United 777-200 on Feb. 13, 2018, as it was preparing to descend to Honolulu. Chunks of the front of the engine tore loose after a fan blade failed, the NTSB said. Metal fragments struck the fuselage, wing and tail sections. The jet flew about 120 miles on one engine and landed safely.

On April 17, 2018, another fan blade failed on a Southwest flight, also a 737-700 using CFM56-7B engines. In this case, a latch mechanism near the front of the engine was flung into the side of the jet, causing a window to break open, killing the woman seated next to it. Pilots landed safely and nobody else was seriously hurt.

The NTSB issued five recommendations to the FAA and its European counterpart, EASA, as a result of the 2018 failure. The safety board called on the regulators to require Boeing to redesign the front of the engine to prevent debris from escaping in the future.

Investigators also sought a broader review of how engines and aircraft are designed to ensure future designs aren’t vulnerable.

A Japan Airlines Co. Ltd. 777-200 suffered similar damage on Dec. 4 after a fan blade broke. In this case, a door on the exterior of the engine broke loose and the plane’s fuselage and tail section were hit by debris, according to a preliminary report by Japanese investigators.

All three of the 777s were powered by Pratt & Whitney PW4077 engines.

Pratt said last June that it had taken corrective actions to address the cause of the 2018 failure. After that incident, Pratt re-inspected all 9,600 fan blades and didn’t find any others with potential safety problems, the NTSB said.

The violent failure on the engine above Denver destroyed most of the relatively unprotected areas at the front of the turbine. At least some debris struck the plane itself, causing minor damage, the NTSB said Sunday in a press release.

One fan blade broke off at the root where it was mounted to a spinning rotor, according to a person familiar with the preliminary investigation who wasn’t authorized to speak about it. A second blade broke off, apparently after it was struck by the first, the person said.

While details of the failure haven’t been provided by the investigation, the violent loss of the blades caused the entire structure at the front of the engine to break loose, according to photos of the remains of the engine. Pilots returned to Denver for an emergency landing.

Both Guzzetti and the person who participated in engine investigations cautioned that the planes in each of the incidents were able to land safely, suggesting that other layers of safety had helped protect against a catastrophe.

The inspections of fan blades ordered by FAA and other regulators also will help lower the chances of a similar failure in the future.

GE spokesman Perry Bradley said it was more appropriate for Boeing to answer questions about the design of the front of the engines since it’s the planemaker’s responsibility under FAA regulations, not the engine manufacturer. Boeing and Pratt & Whitney didn’t immediately respond to a request for comment on the issue.

By contrast, the failure of a Pratt & Whitney engine on a Longtail Aviation 747-400 cargo jet on Saturday in the Netherlands didn’t allow debris to fly out and hit the plane, according to Longtail Aviation Chief Executive Officer Martin Amick.

The failure prompted metal shards to fall to the ground, injuring two people, according to local news reports. The metal debris escaped out the rear of the engine, which is how they are designed to fail.

— With assistance by Ryan Beene, and Siddharth Vikram Philip
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Old 22nd Feb 2021, 20:04
  #145 (permalink)  
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Quite. Fire was burning away happily in the airflow and one presumes after fire bottle deployment. Same thing happening 3 hours from nearest alternate? Concerning.
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Old 22nd Feb 2021, 20:13
  #146 (permalink)  
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good photo!. Now at least one can see where the problem is coming from. Looks like a fire shield to cover 30 sec of time would get rid of the reverser ignition source. The upper nacelle parts seemed to stay out of it and even in the air it would probably go out by itself without the need for extinguisment. We'll see what Boeing does other than lean on Pratt
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Old 22nd Feb 2021, 20:21
  #147 (permalink)  
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Right--ETOPS is completely relevant here. An ETOPS aircraft departing on an ETOPS flight with an engine failure...

But then if anyone seriously questions ETOPS, the long-haul aviation world would come to a complete halt.
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Old 22nd Feb 2021, 20:31
  #148 (permalink)  
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What is the on wing periodic inspection interval and method for the fan blades?
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Old 22nd Feb 2021, 20:37
  #149 (permalink)  
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Every 5000 cycles for fan blades I read elsewhere after the 2018 event.

Last edited by Una Due Tfc; 22nd Feb 2021 at 20:58.
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Old 22nd Feb 2021, 21:05
  #150 (permalink)  
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My cynical guess is: Zero.

They will say that P&W designed it and said it was good and that the engines are not the aircraft. We'll get the "We are working closely with our friends and colleagues in P&W and FAA to ..." to ensure where the blame goes. Then you can discuss the, "Who asked for engines that could go further/faster on less fuel and be reliable for ages? Well, ultimately, the passengers!
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Old 22nd Feb 2021, 21:26
  #151 (permalink)  
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The nacelle coming apart is not supposed to happen - design intent is that the nacelle is designed to withstand the forces of a FBO event without failing. Further, large parts departing the aircraft is a no-no - corrective action should be taken whenever it happens.
Well, it all depends upon the actual unbalance load. The normal assumption is one full fan blade, including the retainer portion which fits in the fan disk, a rather big chuck of material. From the pictures it seems the first blade ruptured just above the spinner so this portion of the blade stayed in place. The departing ('liberated') blade probably took away the adjacent one, at mid span. Not sure if it results in unbalance loads are higher or lower than the nominal case. The engine RPM is also an important parameter.

The FBO demonstration during engine certification typically demonstrates only one fan blade will depart. This is a big deal, because it directly drives the sizing of the containment ring and dermines the unbalance loads used to siez the airframe, nacelle included. The data I remember on such engines is that the separation of 3 adjacent fan blades, at 100% RPM, will result in loads well above the front spart capability of the wing, resulting an instant catastrophic failure of the aircraft structure.

Compared with the certification test involving a full fan blade, in service events with partial blade separation often result in multiple blade damage (and eventually rupture), because the cinematic is different, but the certification case is expected to be the envelope. This will be confirmed (or not) by the investigation.

It is interesting this involves a hollow titanium fan blade design. A similar material is used on the Trent and it resulted in various events with ruptures just outboard of the spinner.
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Old 22nd Feb 2021, 21:39
  #152 (permalink)  
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Looks like I was right - the blade-tip went forwards, and sliced through the cowling ring, eventually destroying the entire cowling (and then hitting the wing-root). There was a lot of push-back to this explanation here, but it has been known as a possibility for decades.. Indeed, the only fan-failure I have had, left impact marks all across the front cowling noise suppression ring.

Unlike the whole blade, the tip has much more forward force on it and a lot less weight, and it can easily spin out the front of the engine. And it appears that this is what happened.

Take a look at the Blancolirio channel.
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Old 22nd Feb 2021, 21:49
  #153 (permalink)  
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Amidst many entries here (and other subject areas ongoing) this SLF/atty has noticed some references to the NTSB incident report about the 2018 incident of the same or substantially similar nature appear to base inferences, or innuendo, on the fact that nothing actually was changed after that incident, that is to say, after the pertinent report was published.

While not having read the full docket of items in the 2018 Board record, one item which has been noted is that the inspection process left a number of things to be desired. (To avoid misstating these, I'm not summarizing the findings of the report here.)

What became of those findings, in context of initiatives to dig deeper into the gaps or evident traps for the unwary, in the inspection area? Just one example: attributing apparent findings to the coating or paint used to facilitate the inspection process (if I understood correctly). That gap having been noted by NTSB, what became of any action steps? Or less non-cynically, were there any action steps?

(Somewhat related, as a member of the traveling-by-air public, to be told that Denver to Honolulu doesn't quite definitely fall within ETOPS, I dunno, I'd have to ask some dumb, non-aviator questions.)
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Old 22nd Feb 2021, 22:22
  #154 (permalink)  
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There were no Safety Recommendations made as a result of the above investigation, so I'm not sure what changes could reasonably be expected.
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Old 22nd Feb 2021, 22:34
  #155 (permalink)  
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The report did point to areas of the inspection process which could be improved, specifically areas which were implicated (if not formally found as a factual matter) to have led to the failed blade flaw(s) going unaddressed - is that not correct?

If that is correct, then is it the case that only formal Safety Recommendations can be predicates for re-examination and improvement of processes?

I'm not being formalistic - I'm not relying on the prior post not referring to "Safety Recommendations". Instead, having identified aspects of the inspection process overall which appeared directly involved in the problem blade continuing in service to failure, is that not a sufficient predicate to ask how to close those gaps? or at least to start to address it?
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Old 22nd Feb 2021, 22:38
  #156 (permalink)  
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Assuming you refer to the SWA1380 accident in April 2018, an AD was issued to effect inspection of possible fatigue cracking in CFM56-7B engine fan blades specifically [FR Doc No: 2018-09338]. It is a reasonable question whether much was done towards similar precautions targeted at other engine types or products.
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Old 22nd Feb 2021, 22:44
  #157 (permalink)  
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It does not demonstrate only one blade will depart. It demonstrates a safe shutdown for all the consequences of the intentional release of a single fan blade. So if that single released blade takes out a couple more blades then the engine must still be capable of being safely shutdown. Mostly nobody cares about all the other engine damage as long as it doesn';t catch fire or break its mounts

Of course there will be unbalance loads including even at windmill conditions. However once shutdown most of the rules govern the aircraft .

Some other poster presented a video which opinioned that windmill vibration loads will break things, including the inlet nacelle. It is important to understand that the greatest load condition across al the engine flanges including the inlet are at the instance of about 5 rev of the fan in rundown.. the windmill unbalance loads loads are minor. Of course aero loading to seriously compromised surfaces must be considered
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Old 22nd Feb 2021, 22:50
  #158 (permalink)  
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Sorry Euclideanplane no, it was:
N773UA, BOEING 777 222
Date of Accident: 02/13/2018

Earlier posts (95) had the NTSB docket; 96 had the final report.
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Old 22nd Feb 2021, 23:01
  #159 (permalink)  
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Of course the safe shut down has many more aspects than the single blade. But the unbalance loads are important, because they drive the aircraft structure compliance. If the engine lose say 5 blades and has a safe shut down, it can be certified, but will remain the most expensive fan ever, because nodoby can install it and certify an airplane able to withstand the FBO loads.

With modern, wide chord fan blades, unbalance loads have increased. As pointed out above, in the 90s FAA and JAA became aware of the issue and drafted AC25-24. The airframer have to demonstrate safe 3-hour diversion with a windmilling engine, covering strcuture, system, structure and human factors. The recent USAF E-11 (Global Express) accident report shows that vibrations are such that flight crew can barely read instruments to the point of shutting down the 'good' engine...
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Old 22nd Feb 2021, 23:12
  #160 (permalink)  
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Tango and Cash

The failure occurred on climbout - not in ETOPS - presumably on high power. Does the power state affect the probability of blade separation? In other words, if an engine doesn't fail on climbout, is it likely to fail in cruise?

The engine burned but the fire doesn't seem to have compromised the wing above, so I guess the fuel shutoff was effective and as stated earlier in this thread, what was burning was 'only' engine oil and maybe hydraulic oil, and if this had happened in ETOPS it would have burned itself out in a relatively short time.

OTOH, as shown in the photo in post #142, something punctured the fuselage below the wing root and, in cruise, would presumably have caused decompression.

How many ETOPS flights take place every day? In the many years since ETOPS was introduced, how many engine failures endangering the aircraft have occurred in ETOPS flight? Of course, there's always got to be a first time ...
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