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United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

avherald.com

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Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#441

Post by galangalalgol »

airhead969 wrote: post #437
galangalalgol wrote: post #426

Earlier quoted context omitted.

I'm sure people PW is working on that, but the failure rates on commercial aircraft parts are already ridiculously low. Bad things will always happen.

"Bad things will always happen" is a despicable shrug mentality. Bad things happen when people don't have their acts together in design, engineering, manufacturing, maintenance, and operation. The failure rates should be striving for zero, unlike the stunts Boeing has pulled on 737NG, MAX, and the 787.

Totally agree with you on the recent laxness in design and the regulatory capture that allowed it. But treating zero as a feasible goal is unrealistic. I've done code inspections for safety of flight code and making sure you have 100% coverage and branch coverage not just in the high level code but in assembler still doesn't get everything. You try to make sure that redundancy saves you (seriously boeing!) But common mode errors and just human fallibility to see all the possibilities mean we miss stuff. And all this is so much easier in software than in mechanical designs where redundancy sometimes just isn't doable. We shouldn't give up best practices, but we shouldn't have unreasonable expectations of them either. And not every engineering failure implies a failure in engineering process.

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#442

Post by galangalalgol »

galangalalgol wrote: post #441
airhead969 wrote: post #437

Earlier quoted context omitted.

"Bad things will always happen" is a despicable shrug mentality. Bad things happen when people don't have their acts together in design, engineering, manufacturing, maintenance, and operation. The failure rates should be striving for zero, unlike the stunts Boeing has pulled on 737NG, MAX, and the 787.

Totally agree with you on the recent laxness in design and the regulatory capture that allowed it. But treating zero as a feasible goal is unrealistic. I've done code inspections for safety of flight code and making sure you have 100% coverage and branch coverage not just in the high level code but in assembler still doesn't get everything. You try to make sure that redundancy saves you (seriously boeing!) But common…

I wanted to clarify my last statement. Even when best practices are followed bad stuff happens, and that doesn't necessarily mean best practices need to change.

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#443

Post by ajarmst »

interestica wrote: post #327
kortilla wrote: post #308

Earlier quoted context omitted.

That’s a different type of failure. Uncontained vs contained.

Kinda. While the 2018 incident was "contained", it still resulted in damage to the fuselage. "Two small punctures were found in the right side fuselage just below the window belt with material transfer consistent with impact from pieces of an engine fan blade" (From the link in parent to this thread https://avherald.com/h?article=4b4e8ca7&opt=0 )

Not 'kinda'. Debris exiting the engine housing with sufficient energy and in a direction that leads to damage of other systems is the literal definition of an unconfined engine failure (i.e. it can spit as many parts as it wants to out the exhaust). There is a band of armour around the plane of the fans that should prevent any blades leaving the engine perpendicularly. If there was fuselage or wing damage from debris, that was an unconfined failure and would require investigation as a major fault.

However, loss of the shroud doesn't necessarily imply there was a confinement failure. Damage to the shroud during the event can easily lead to the cowling shedding aerodynamically, which is also part of the design: the last thing you need is more drag on the dead engine side. We can't tell which that was in this case, but it's important that we do---the design criteria specifying that the aircraft can be safely recovered from a catastrophic single engine failure during any stage of flight would assume the failure is confined to the engine.

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#444

Post by halefx »

milankragujevic wrote: post #223
Fogest wrote: post #205

Earlier quoted context omitted.

BREAKING NEWS: More people died of COVID today. I see see often headlines in my Google news feed saying something along those lines. I've stopped clicking on YouTube videos that give me no idea what they are going to be in the thumbnail/title. For example on Linus Tech Tips second channel ShortCiruit a good chunk of their videos do this. Latest one from 3 years ago in my sub box "I almost hurt myself open this...." a…

Offtopic to OP but regarding Linus Tech Tips: I also stopped watching 90% of all LMG (his company) videos (on all their channels) because of the clickbait forcing me to click onto things that I am not interested in, only to quickly leave the video. I am not going to watch what I don't want to watch whether it has a clickbait thumbnail and title or not, so they just annoy me more with this. I have not voiced my opinio…

I watch LMG content because I find it more entertaining than anything else on YouTube, and I'm not even a PC gamer. I rarely look at the poster or video title at all before watching, I just queue the new items immediately.

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#445

Post by airhead969 »

galangalalgol wrote: post #441
airhead969 wrote: post #437

Earlier quoted context omitted.

"Bad things will always happen" is a despicable shrug mentality. Bad things happen when people don't have their acts together in design, engineering, manufacturing, maintenance, and operation. The failure rates should be striving for zero, unlike the stunts Boeing has pulled on 737NG, MAX, and the 787.

Totally agree with you on the recent laxness in design and the regulatory capture that allowed it. But treating zero as a feasible goal is unrealistic. I've done code inspections for safety of flight code and making sure you have 100% coverage and branch coverage not just in the high level code but in assembler still doesn't get everything. You try to make sure that redundancy saves you (seriously boeing!) But common…

I never said it was feasible, you did. It must be strived for, because that's the difference between excellence and crap.

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#446

Post by sxcurry »

ufo wrote: post #100
jrockway wrote: post #28

Earlier quoted context omitted.

By having airports on islands, or by pushing up the number of minutes that the engines/operator are certified for.

For transatlantic flights, two important "backups" are in Iceland and in the Azores. I wonder how often airplanes actually have to detour to these airports...

Years ago I was on a 747 from SFO to LHR that landed in Iceland - oil pressure problem in an engine. A guy drove out with a pickup truck, climbed into the engine using a ladder in the back of the truck, and started hammering away. After a few hours in the terminal we got back on the plane and flew the rest of the way to LHR. I kept wondering just how qualified he was...

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#447

Post by ajarmst »

dognotdog wrote: post #304
ajarmst wrote: post #196

Earlier quoted context omitted.

As well as two demonstrations that the aircraft meets the design specification that even a catastrophic failure in the worst stage of flight is easily recoverable. I'd expect an increased inspection rate, possibly some new mandated ND testing for fractures and discontinuities (the last one was an LP shaft failure, IIRC). One thing that does bug me, though is that we now have two events where the shroud was lost. Were…

It looks it’s the “cowling” that was lost, not the protective shroud / containment around the fan (and the rest of the engine) that keeps the fan/compressor/turbine blades from becoming high speed radial projectiles when they break off at full speed.

Agreed. The last one was pretty clearly a failure of a shaft or turbine, and the damage was much more obvious. This might be something completely different.

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#448

Post by airhead969 »

galangalalgol wrote: post #442
galangalalgol wrote: post #441

Earlier quoted context omitted.

Totally agree with you on the recent laxness in design and the regulatory capture that allowed it. But treating zero as a feasible goal is unrealistic. I've done code inspections for safety of flight code and making sure you have 100% coverage and branch coverage not just in the high level code but in assembler still doesn't get everything. You try to make sure that redundancy saves you (seriously boeing!) But common…

I wanted to clarify my last statement. Even when best practices are followed bad stuff happens, and that doesn't necessarily mean best practices need to change.

Of course not. Make improvements rather than knowingly shove-in bad Ducommun parts on the line or crappy MCAS. Also, hold manufacturers responsible when they take cost-shortcuts, sacrifice safety, and kill people. Boeing routinely gets a slap for doing so since it's also considered a strategic defense contractor, part of the MIC that greases palms in DC.

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#449

Post by hazeii »

dtgriscom wrote: post #417
hazeii wrote: post #406

Earlier quoted context omitted.

Plenty of youtube videos of a blade-off test - here's a short one [0] of an A380 Rolls Royce engine testing. That's about £9,000,000 of engine being destroyed in this (successful) test. [0] https://www.youtube.com/watch?v=5-8_Gnbp2JA

At the beginning of the video the blades seem to be spinning at about 2RPS, but after the explosion they're spinning much faster. I presume the former was an artifact of the camera's frame rate.

They normally have high-speed cameras running; that short video is a mish-mash of super-slow-mo and regular speed footage. There are much longer versions on YT, e.g. this one [0] which covers it in more detail (watch the people in the room jump when it blows - despite being a fair distance away).

[0] https://www.youtube.com/watch?v=j973645y5AA

Re: United B772 at Denver on Feb 20th 2021, engine inlet separates from engine

#450

Post by hazeii »

codingdave wrote: post #169
valuearb wrote: post #143

Earlier quoted context omitted.

The 777 has been flying for 25 years with almost no fatal accidents. Unless your flight will be flying over Russian anti-aircraft missile batteries or through a wormhole above Malaysia, you should be perfectly safe.

Another way of looking at it is that after flying and accumulating 25 years of wear and tear without major incident, we now have seen a repeatable flaw that these aircraft may encounter due to their age.

Engines are separate from the airframe; on big commercial aircraft the engines get swapped/moved around all the time (the engines may well be on lease, separate to the lease on the airframe). Thus, in this sort of situation it's the engine's history that'll be important, rather than the airframes.
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