United B777 engine failure
 

Reports on Twitter that a UAL 777-200 has had an uncontained engine failure on the way from DEN (Denver, Colorado, USA) to HNL (Honolulu, Hawai'i, USA) and returned safely to DEN. Local news report: https://thepostmillennial.com/colora...nited-airlines

There's a twitter post by user @stillgray with video of the failed engine from in the aircraft that pprune doesn't seem to want to include here...

https://cimg6.ibsrv.net/gimg/pprune....1bbed57fd.jpeg
UAL 777
https://cimg0.ibsrv.net/gimg/pprune....8e31d1b385.jpg
Ground debris

Whoops fairly dramatic, both the footage and the debris.
Pretty lucky that no-one was hurt.

Looks mostly contained, but perhaps a couple of compressor blades seem missing. There is a gap there when you slow down the video.

The high vibration would support a fan blade issue. See the recent JAL event.

Busy days at PW flight safety department.

Yep, fan blade release, extreme vibration fails the inlet attachment and it detaches, resultant aero loads and vibration fail most of the rest of the nacelle.

It was during the 777 program that Boeing discovered that the fan blade out vibration levels where considerably higher than what had been previously assumed (presumably aided by the much higher bypass ratio that the 777 engines had compared to previous big fan engines).
Given this even and the fore mentioned JAL event - it would seem that even the higher loads that were used during the 777 design/cert program were not high enough :uhoh:

tower audio
 

Local radio station KDVR has the tower audio. About what you would expect.

Evidently I'm not allowed to post URLs. Try this instead:
kdvr dot com slash news/local/listen-mayday-call-from-crew-of-united-flight-328/

Underestimation of the fan blade out loads has been a general trend, apparently. See the 737NG and the Southwest event. Perhaps nobody really wants to carry around that heavy structure to cover a rare event.

A curious question from an amateur
 

It looked like the engine was still receiving fuel and burning away happily after the pilot would no doubt have hit the fuel cutoff switch. Why would that be?

There is also the engine oil, and some hydraulic fluid, out there.

Who was the engine manufacturer ?

It might just be some of the epoxy composite containment got hot enough to burn. Plenty air to feed the combustion.

ETOPS
 

Would of been interesting midway between the west coast and the destination Hawaii.

Pratt & Whitney

Engine oil or maybe hydraulic fluid.

Some similarity with the South West secondary events. The engine itself does a good job of capturing the high energy blade pieces. Unfortunately some of the blade pieces find their way forward of the containment belts and chew into the soft inlet. with a big slashing effect. If the slash gets very long circumferentially then the cowl becomes limited in vibration. looking at the various video feeds on the nws, the shiny front lip of the cowl can be seen after the initial event still attached. Later on in the flight it is now missing.

It is not good that the engine nacelle (reverser) caught fire. The smoke behind the engine does not match a fuel fire and neither does the flame color in the videos. Quite possibly the non-metallic vanes in the reverser are what is burning. The ability to extinguish this in flight is challenging, but at least the slip stream keeps it away from the wing spar. I would be interested to know how the fire fighters addressed this on the ground.

I suspect there will be a few lessons learned here

VAS summary video of incident
 

VAS aviation video

I don’t see any hole in the casing. Don’t see any report of debris hitting the fuselage. Is it really an uncontained failure?

if bits fall off its uncontained!

TD,

Was the vibration levels the same on all engine types?
Thanks.

Technically contained vs uncontained for certification is only concerned with rotor parts inside the engine. So while the severe vibration causes nacelle parts to fail they are not proof of an uncontained failure.

The fan parts are allowed to impact up to +/- 15 degrees forward / aft radially but must not exit the fan other than out the back after they’ve been stopped so to speak.

Don’t have the books here. But last time I read it, uncontained, meant blades coming out at high energy sideways with risk of serious damage to the remaining aircraft.
bits coming through the back or low energy is a successful blade failure containement.

568

No, it's a function of the engine. The GE90 was the worst - not coincidentally it also has the largest diameter fan (~120 inches, vs. ~112 for the PW4084 - the GE90-115B is ~122 inches).

It was the FBO test of the GE90 that was the real eye-opener. The blade debris was completely retained, but the vibration was so great that the inlet fell off, with several bits of the engine accessories. FBO is always tricky due to the uncertainties. It's a hugely expensive test to run (basically destroying a highly instrumented engine in the process), so they only want to run it once (assuming it passes) - so you have the statistical uncertainty of a single data point. It's also run statically, so you don't get the effect of the forward speed aero loads (which must be estimated). As Lomo noted, on the 737NG events, the fan blade debris moved forward beyond the containment ring and got into the inlet - I don't think we've ever seen that during a FBO static test so there are apparently other dynamics at play due to forward speed of the aircraft.
Lomapaseo, IIRC correctly the reverser cascades are carbon composite for all the 777 engine installations - so I presume hydraulic fluid (from the T/R actuators) started burning, which then ignited the resin in the carbon composite cascades.

https://cimg4.ibsrv.net/gimg/pprune....d07cfa7b7.jpeg

The tan covering around the fan casing is acoustic dampening and also intended to capture smaller parts almost like a bulletproof vest. Behind is the accessory case/gearbox which contains or drives (amongst other things) electrical generator, hydraulic pump and engine oil pumps.
So even with the fuel valve shut off there is still plenty of hydraulic oil and engine oil that will burn. Composite materials may have been covered in fuel or oil during the initial failure.
In short, there’s plenty to burn for at least a short period of time.
Engine fire suppression bottles may be less effective with that much cowling missing.
So it may just have to burn itself out.

* This is an exceptionally rare and spectacular failure but it’s not as potentially catastrophic as it looks.
If you’re an ER doctor this is a shallow wound with lots of blood if you will.

No damage to the wing or fuel tanks, no damage to the fuselage, no explosive decompression, no damaged flight controls.
Just really spectacular :}

That's not the definition of an uncontained failure.
The definition of an uncontained failure is high energy debris exiting tangential to the engine (within a few degrees).
Bits coming out the front or back, or the inlet/nacelle falling off, is not considered an uncontained failure. That being said, large bits of the inlet and nacelle coming off is a big no-no since it can do damage to the tail surfaces or to people/structures on the ground.

TD,

Great information as always, sure appreciate that!
Regarding the 737-700, did the Southwest 1380 engine episode also exhibit debris moving forward?

B2N2

The tan covering is the fan containment ring - probably Kevlar. It provides no meaningful acoustic dampening - it's only purpose is to catch and contain fan fragments.
The gearbox is in the core area of the engine (PW4000 and GE90 - Rolls Trent has the gearbox on the fancase), however the oil tank is on the fan case. The fire appears to be in the reverser cascades which as I noted are a carbon composite structure. Likely oil or hydraulic fluid started burning which then ignited the resin the the composite construction.
There is no fire suppression system for the fan case on the PW4000 and GE90 installations - only on the core.

tdracer

27 year old aircraft (though engine may not be), 777 number 5. It even spent its first year flying in the development programme It's taken a good while to show up.

I agree with the comments that the thread title seems inappropriate, as video evidence so far points to a brilliant example of a successful containment.

Following from a few posts above

The engine test is just that, nothing more. The idea is to demonstrate the engine capabilities and provide enough load data to the various installers to use in estimating the loads on their nacelle and their pylon mounts. This goes along way in later analysis to demonstrate to t the FAA that the engine has the capability to be safely installed on multiple aircraft designs. It's then up to the Boeings and Airbus to design their parts to remain safe,

The last thing the engine guy wants is to have some sort of test apparatus that screws up the engine to demonstrate itself and to generate useful load data. Hence interface parts like inlets and nacelles are chosen simply as end-loading attachments. The inlets must operate at zero static speed and max power so they really don't look like flight inlets and then ejected blade pieces just screw themselves forward and out the inlet rather than through the side (just like a turbine exhaust pipe)
The FAA is quite tolerant of the measured load capability in the presence of containment and rundown of the engine debris. Some of us like numbers more than just a one-off test..

On the engine side the worst loads to the mounts and fan bearing supports etc. occur in about 5 rev of the fan, after that it's just run-down loads and changing frequencies to the stuff hung off the engine. This quite often shows up in large oscillations as the plane slows down for landing. Typically nothing to worry about except for passenger comfort

Obviously there are some lessons to be learnt here that will have to wait for the investigation to complete

Well...I just watched an interview with aviation gadfly, Greg Feith, who clearly stated that this event was an "uncontained engine failure," so take that for what it's worth.

More media:

Former National Transportation Safety Board Chairman Jim Hall called the incident another example of “cracks in our culture in aviation safety [that] need to be addressed”.
Hall, who was on the board from 1994 to 2001, has criticised the FAA over the past decade as “drifting toward letting the manufacturers provide the aviation oversight that the public was paying for.” That goes especially for Boeing, he said.

Seems Pprune writers aren't the only ones who have the answers long before the investigators...

That's pretty rich, given this was certified over 25 years ago - when he was the chair of the NTSB...

With the size of the fan blades on modern high bypass jet engines, we are reaching the stage where a failure will have similar consequences to losing a propellor blade on a piston or turbo prop. If the pitch isn't bought into feather immediately then the engine will do its best to shake itself out of the wing.

Lockhart

Are you sure here was a fire light?

It depends on where the pick-ups were installed and where the extinguishing is directed. I don't believe there would be much annunciated for a fire in the reverser

The whole engine was vibrating pretty badly. Was there any danger of the engine attach points failing and the whole engine coming off the wing ?

The area where the visible part of that fire is located is not a fire zone. The fire detectors on that engine are limited to the core compartment.

lomapaseo

For the PW4000 installation, reasonably sure there isn't any fire detection in the fan cowl - and I'm certain there is no fire extinguishing ability (not that it would help with the cowl missing). Fire detection/overheat/extinguishing is all in the engine core - not the fan cowl. For engines where the gearbox is located on the core, the fan cowl is a "flammable leakage zone" (oil and hydraulic fluid) - by design there are no ignition sources, so no fire detection needed.
Edit - I see Dave T beat me to it...

WHBM

Its not like a car where the Engine will most likely stay with the chassis for life. Aircraft Engines get swapped out and replaced during their life cycle. Also now days the Engines are leased by the operator and its separate to the Airframe.

Strictly by definition it seems not to be an uncontained engine failure (I rely on the experts to review engine, ot in speculation). However such size of parts departing aircraft is itself an issue both for risk of damage to aircraft and on ground below. From an operational point of view seems to have been well managed.

nonsense

I really don't understand this logic in relation to this incident. Yes, BOE clearly have had it too easy in recent years and processes needed a significant tightening, but I'm not sure how an engine failure relates to this? The B777 family have proven over 25 years that it's probably the most reliable and safest aircraft in history - the GE90 equally the most reliable engine in history (I know this is the PW option)... we see this in the reliability data - 1 IFSD per 1,000,000 FH. This may be overtaken by the A350 after being in service that long.

For what it's worth, as more aircraft are removed from long term storage, I can forsee more incident rearing their ugly heads, but not on the scale of this.

As for being line #5 - so what? The engines will be serviced every few years (I don't know the typical MTBR on a GE90 / PW4000). but over 25 years, I'd have expected at least 6 SVs.