Catastrophic engine failure on Flight UA328

[Astronuc]

https://www.flightglobal.com/safety/united-777-suffers-engine-failure-over-denver/142519.article

https://www.flightglobal.com/safety...tained-forward-cowling-missing/142520.article

https://www.ifn.news/posts/united-airlines-flight-ua328-suffers-serious-engine-failure/

The 777 nevertheless returned to the airport and landed safely. "Involved was N772UA, a 26 year-old Boeing 777-200. It was forced to return for an immediate emergency landing, which the pilots carried out safely with no further incident."

"Two similar incidents also occurred with United Airlines in 2016 and 2018. Both cases involved a serious failure of a Pratt & Whitney PW4077 engine on Boeing 777-200 aircraft, the first one being caused by a birdstrike, the second by an oversight during engine maintenance." Maintenance of teh aircraft and engine will certainly be scrutinized.

 

[berkeman]

https://www.ifn.news/posts/united-airlines-flight-ua328-suffers-serious-engine-failure/

Yeah, not what you want to see when looking out of the cabin window...

 

[anorlunda]

Losing an engine in flight is not so bad. All airliners can fly fine with one engine out.

The most scary thing is that the debris can penetrate the fuselage and kill passengers. That really happened a few years ago. But if you are alive enough to look out the window and see that scene, you already survived the most dangerous part.

The second most scary thought is that the cause of the engine failure may not be random. It could be an error that could also cause the other engine to fail the same way.

The third level thought (maybe most scary) is that the engine failure damaged the wing and the wing is about to fall off.

My best wager is that most passengers would not think about such things. They would be thinking about turning on their cell phones to phone home.

 

[Klystron]

The OP articles indicate high-speed fan failure in the engine without noting FOD (foreign object damage).

In the second link the pilots mention using the (emergency) checklists following the engine failure. One of my last assignments at NASA Ames involved modeling the Boeing 777 electronic data recording systems including so-called 'black boxes' for pilot training simulators. A colleague modeled the emergency digital checklists based on potential failure modes including catastrophic engine failure.

Boeing 'went the extra mile' designing and testing 777 pilot information interfaces and automated checklists. It would be interesting to learn how Boeing selected the 777 engines.

 

[Astronuc]

The second most scary thought is that the cause of the engine failure may not be random. It could be an error that could also cause the other engine to fail the same way.

Such an event happened to Cathay Pacific flight 780. https://en.wikipedia.org/wiki/Cathay_Pacific_Flight_780

"After another two hours elapsed, the aircraft was on descent to Hong Kong when, at 05:19 UTC, about 203 kilometres (126 mi; 110 nmi) southeast of Hong Kong International Airport , the aircraft's ECAM displayed "ENG 1 CTL SYS FAULT" and "ENG 2 STALL" within a short period."

The cause of the accident was contamination (filter resin beads) of the fuel taken on board at Surabaya, which gradually damaged both engines of the aircraft. The flight made to the destination, but had to land at a high speed because the No 1 engine was stuck at 74% power. They landed at about 230 knts (265 mph, 436 kmph) well above normal landing speed.

A video dramatization of the flight on the Smithsonian Channel.


https://news.aviation-safety.net/20...-problems-and-emergency-landing-at-hong-kong/

 

[DaveE]

Good early coverage of this from Blancolirio

 

[Vanadium 50]

From UA's web site: "UA328: Your flight is canceled because your plane needs repairs. We're sorry for the inconvenience."

They're not wrong.

 

[Astronuc]

"UA328: Your flight is canceled because your plane needs repairs. We're sorry for the inconvenience."

A wee bit of an understatement.

A new engine and right nacelle, and it will be good as new. Probably have to replace the left engine as well.

 

[Vanadium 50]

I'd also want someone to look at the landing gear and tires. It landed overweight and didn't use thrust reversers.

I'm pretty sure I've been on that aircraft (along with many thousands of others). N772UA is a 772. Sticks in your head.

 

[Dr Transport]

First indication is that a fan blade separated, with a possible second. Very troublesome that the engine cowling sheared off ad separated.xx.

 

[Astronuc]

A new engine and right nacelle, and it will be good as new.

I was being sarcastic here. Probably should have added or

 

[Vanadium 50]

Sarcasm aside, you're probably right - it's nowhere near a loss of an airframe. The extra section to get the passengers to HNL was N773UA, which was the aircraft involved in a similar incident in 2018 flying SFO-HNL.

Engines get replaced all the time.

 

[DaveE]

Also AgentJayZ talks about the engine, if you want more. If you want to learn what's inside a jet engine, he has some other good videos.

 

[Astronuc]

https://www.nbcnews.com/news/us-new...ment-united-flight-328-engine-caught-n1258473

United is the only U.S. airline with the Pratt & Whitney PW4000 in its fleet, the FAA said. United says it currently has 24 of the 777s in service.

https://abc7.com/boeing-777-airplane-engine-faa/10359983/

Airlines in Japan and South Korea also operate planes with the Pratt & Whitney engine. Japan Airways and All Nippon Airways have decided to stop operating a combined 32 planes with that engine, according to Nikkei.

Nikkei reported that Japan's Ministry of Land, Infrastructure, Transport and Tourism also ordered the planes out of service, and the ministry said an engine in the same PW4000 family suffered unspecified trouble on a JAL 777 flying to Haneda from Naha on Dec. 4. It ordered stricter inspections in response

AP and other sources reported that United has grounded their 777s.

United statement:
"Starting immediately and out of an abundance of caution, we are voluntarily and temporarily removing 24 Boeing 777 aircraft powered by Pratt & Whitney 4000 series engines from our schedule. Since yesterday, we've been in touch with regulators at the NTSB and FAA and will continue to work closely with them to determine any additional steps that are needed to ensure these aircraft meet our rigorous safety standards and can return to service. . . . ."

Sarcasm aside, you're probably right - it's nowhere near a loss of an airframe. The extra section to get the passengers to HNL was N773UA, which was the aircraft involved in a similar incident in 2018 flying SFO-HNL.

Engines get replaced all the time.

But as one indicated in a previous post, landing gear and other parts need inspection, but also the NTSB and FAA will have to determine if the primary/root cause was the engine, the nacelle, or some combination. I imagine the planes will be grounded for some time.

I heard one report that pieces of two blades (ostensibly fan) were found. The ABC article cites:

• Two fan blades were fractured

-One fan blade was fractured near the root
-An adjacent fan blade was fractured about mid-span
-A portion of one blade was imbedded in the containment ring
-The remainder of the fan blades exhibited damage to the tips and leading edges

I wonder if the pilot dumped the fuel before landing.

 

[Vanadium 50]

I wonder if the pilot dumped the fuel before landing.

Reports are that he did not.

There are reports of blood inside the engine. That would, if confirmed, suggest a bird strike as likely.

 

[DaveE]

I wonder if the pilot dumped the fuel before landing.

He landed too quickly to have dumped fuel.

 

[berkeman]

I wonder if dumping fuel is contraindicated when you have an engine on fire...

 

[Klystron]

If the flight was non-stop from Denver to Honolulu, the Boeing 777 likely carried maximum regulation mandated fuel amount. Aside from the exposed flames, as questioned above, the time and pumping required to jettison fuel coupled with Denver altitude and return distance to airport likely contraindicated dumping fuel.

United Airline quite lucky in that ~3/4 of the route DEN to HNL extends over open ocean. Incredibly lucky that engine debris fell on land, so recoverable, without any known injuries or related damage.

[Edit 20210328: replaced ambiguous "maximum" with intended meaning of 'regulation required fuel for open ocean commercial flights'. Thanks to post #40.]

 

[Astronuc]

He landed too quickly to have dumped fuel.

Delta flight 89 out of LAX dumped fuel within ~20 minutes after takeoff. "On January 14, 2020, the Boeing 777-200ER conducting the flight had engine problems shortly after takeoff; while returning to the origin airport for an emergency landing, it dumped fuel over populated areas adjacent to the city of Los Angeles, . . . "

https://en.wikipedia.org/wiki/Delta_Air_Lines_Flight_89
https://www.latimes.com/california/...before-it-dumped-fuel-on-an-elementary-school

The United pilot may have chosen not to dump because of the Delta 89 experience. According to Flightradar24, UA 328 was in the air about 23 minutes. Denver airport elevation is ~5430 ft (1655 m). Shortly after lift off the flight was at 7100 ft @0805, ~13450 ft @ 0809, then began descent. It was at ~5825 @0827 just before landing at about 0828.

https://www.flightradar24.com/blog/united-ua328-suffers-engine-failure-departing-denver/

 

[Nugatory]

Much discussion, much of it informed, at https://www.pprune.org/rumours-news/638797-united-b777-engine-failure.html inlcuding a link to YouTube video with the communications with air traffic control.

 

[DaveE]

I wonder if dumping fuel is contraindicated when you have an engine on fire...

This would depend on the aircraft design. It's why some designs dump fuel from the wing tips.

However, the priority if there is a "real" fire is to land ASAP, so I think it's a moot question. There are no common commercial aircraft that can't land overweight, provided they don't have a very short or slippery runway (DEN has long runways). Of course they may trash the tires, brakes, and maybe the landing gear, which is why many don't want to land overweight. Indeed there are common aircraft types that can not dump fuel (737, A320 for example). Also, unless the pilot stuffs that landing, a high-speed rejected take off is the worst case.

In the LA case, most knowledgeable commentators said there was no need to dump fuel. For example, this video from a 777 pilot describes fuel dumping and overweight landing issues.

 

[Astronuc]

There are no common commercial aircraft that can't land overweight, provided they don't have a very short or slippery runway (DEN has long runways).

It depends on the pilot and probably elevation and winds. I've experience smooth landings where one does not feel contact with the runway, and I've experience hard landings where bins drop open, things fall, people get jostled and aircraft bounce two or more times.

I've been through Denver a lot the last several years, on United's 777, which are nice, and plenty of 737s.

 

[DaveE]

It depends on the pilot and probably elevation and winds.

Elevation and wind (as well as other stuff) is planned for in the stopping distance calculation and briefed before take off. What the passengers feel is mostly irrelevant unless the landing is awful, you don't have to land on the numbers. OTOH, there is no limit on how badly a plane can be landed, LOL.

 

[DaveE]

The thing to keep in mind is that you should always be able to immediately return and land from the airport you just left in essentially the same configuration. It isn't safe or allowed to take off if you can't get the plane stopped on the runway if you have to abort at high speed (V1). At V1 you have maximum weight, speeds comparable to landing, and you've already used up a bunch of the runway.

 

[Vanadium 50]

Some pictures:

That'll buff right out.

 

[.Scott]

I like @DaveE posts - especially the video.

I would add one thing:

In the case of UA238, the fire was contained to within the engine - although visible from outside of the engine.
For fires that are external to the aircraft, an important consideration is the flame propagation rate. That rate varies by the type of fuel and the initial fuel temperature, but it is always well below the airspeed of a jet. Though smaller planes may need to speed up to extinguish the flames.

What this means for the discussion above is that once fuel has entered the slip stream, it cannot immediately contribute to an aircraft fire. If it wets the aircraft, then it could a problem after landing.

 

[Vanadium 50]

In the case of UA238

It was UA328. But U-238 certainly is pyrophoric.

 

[trainman2001]

What I've read in Aviation Week is that one blade possibly fractured at the root from a fatigue crack and impacted the other breaking at its midpoint. The containment shields seemed to have worked, but there is concern about why the nacelle casings came off as they did. They're not supposed to do that.

An A380 lost the entire fan when the hub failed. That was a more serious event due to the amount of debris that was flung off. All of the parts ended up in the ice in Greenland. It took almost a year to find the critical hub, but find it they did. It was essential to have it to know what happened.

The bigger the fans get the greater the forces acting on them to pull them apart. P&W is now fielding a geared fan engine which puts the fan power turbine through a planetary gear set so the fan runs at a slower and more efficient speed while the rest of the rotating equipment runs at its optimal speed. These are three-shaft engines so the hp compressor is driven by the hp turbine, the lp compressor runs from its lp turbine at a lower rpm, and the fan turbine spins at a still slower speed. Gearing solves one problem, but does add more mechanical stuff that can fail.

Radial piston engine propellors ran through reduction gears for similar reasons; to enable the prop to turn at its optimal rpm while the crankshaft operates at its faster rpm. In other words, engine makers have lots of experience designing high horsepower gear trains. Another example is the gear train and clutch used by the F-35B STOL version to drive the lift fan. That system is designed to handle 45,000 hp. And like other US produced aviation engines, it's designed to run for 2,000 hours between major overhauls.

 

[Astronuc]

AP reports, "Exam finds multiple cracks in part of United jet’s engine"
https://apnews.com/article/us-news-transportation-5e9f9b7dbc1515fe5a058e7ce65315f7

The National Transportation Safety Board said the blade found “multiple fatigue fracture origins” on the inside surface of the hollow fan blade. The board said “multiple” secondary cracks were found, and that the examination is continuing.

The Pratt & Whitney engine had been used on 2,979 flights since its last inspection, the NTSB said. . . . .

 

[berkeman]

The Pratt & Whitney engine had been used on 2,979 flights since its last inspection, the NTSB said. . . . .

Wow, that sounds like a long time between inspections! What is the standard interval in flight hours between engine inspections? Does routine engine inspection include the fan blades? Or is the inspection interval for them longer? Do they use x-rays to inspect the interior of the blades?