EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: SiliconWizard on February 23, 2021, 02:06:19 am
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Sad days for Boeing really.
https://www.nbcnews.com/news/us-news/faa-orders-stepped-inspections-boeing-777s-after-engine-failure-united-n1258477 (https://www.nbcnews.com/news/us-news/faa-orders-stepped-inspections-boeing-777s-after-engine-failure-united-n1258477)
Must have been a special experience for the passengers. Seeing that through the windows:
https://www.youtube.com/watch?v=NMH70vQonA0 (https://www.youtube.com/watch?v=NMH70vQonA0)
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Are you somehow sure it was Boeing's fault?
It's a Pratt & Whitney Dependable Engine fitted on that thing, and serviced by UAL's maintenance team.
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Are you somehow sure it was Boeing's fault?
Yeah, only 777's with the Pratt & Whitney engine are grounded.
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Are you somehow sure it was Boeing's fault?
It's a Pratt & Whitney Dependable Engine fitted on that thing, and serviced by UAL's maintenance team.
It's the optics of it.
Another PW4000 series on a 747 shed its guts over the Netherlands the same day.. and another United flight (a 737 this time, not a P&W engine) had an engine failure, also the same day. Most aren't going to care about what engine it was - three more Boeings went bad all in one day.
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Apparently that's a titanium fire in the video :o
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Boeing has no culpability in engine failures. Zero. With that logic, we’d ground Airbus 320’s when a Boeing 737 has a CFM56 failure. It’s only the 777-200 that is affected with about 60% of them are currently flying, if that. No one died. It’s P & W that has the black eye, no one else. There have been prior issues with fan blades.
Apparently that's a titanium fire in the video :o
Says who? Only the cold, front half of a turbofan uses titanium. The fire was the rear half and that was no titanium fire.
https://www.fire.tc.faa.gov/pdf/fsr-0457.pdf (https://www.fire.tc.faa.gov/pdf/fsr-0457.pdf)
If you’re interested in a opinion on the actual failure of the engine without the hyperbole of the media, have a watch. Keep in mind this was done early on Sunday before any qualified eyes had seen the actual engine, this was done from the available information at that point in time. Still worth a watch to learn a thing or two about jet engines from a very knowledgeable guy.
https://m.youtube.com/watch?v=VQwaqDe3jio (https://m.youtube.com/watch?v=VQwaqDe3jio)
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Boeing has no culpability in engine failures. Zero. With that logic, we’d ground Airbus 320’s when a Boeing 737 has a CFM56 failure. It’s only the 777-200 that is affected with about 60% of them are currently flying, if that. No one died. It’s P & W that has the black eye, no one else. There have been prior issues with fan blades.
The public does not know or care who makes the engine. They see 'Boeing' and 'Airbus'. Thankfully, they're not the direct customers, but it's still not good for them.
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No, of course it’s not good for Boeing but then there isn’t much that makes the media circus these days that is positive.
From a current 777-300 pilot with his take on the engine failure with no :bullshit:
https://m.youtube.com/watch?v=EwNCCrjMmeg (https://m.youtube.com/watch?v=EwNCCrjMmeg)
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Yup, and Juan's original video from right after the incident:
https://www.youtube.com/watch?v=Tkieg1ZFcPE (https://www.youtube.com/watch?v=Tkieg1ZFcPE)
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Apparently that's a titanium fire in the video :o
Says who? Only the cold, front half of a turbofan uses titanium. The fire was the rear half and that was no titanium fire.
https://www.fire.tc.faa.gov/pdf/fsr-0457.pdf (https://www.fire.tc.faa.gov/pdf/fsr-0457.pdf)
Fuel was shutoff, fire was going on for a very long time.
Another engine fire CFM56-7 HPC Titanium Fire Due to VSV Maintenance Assembly Error (United Boeing 737-924 N30401) 21 February 2019 (http://aerossurance.com/safety-management/cfm56-titanium-fire-error/) the housings are titanium so I assumed that was the fuel.
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there might be titanium keeping it burning but thats not titanium burning as I know it, when you put it on a grinding wheel it makes a bright white spark stream (impress the neighbors and light the trash on fire)
That looks like hydrocarbon fire to me. if there is titanium burning in there it would keep the fuel burning like a pilot light on a stove. I never saw non powder titanium burn but I imagine it looks like magnesium, you don't get any kind of bushy plasma from it, its going to glow white hot and emit alot of grey smoke. I don't know how well those engines turn off or how much is left in the line after turn off or if there are lubricants and stuff there that also burn eventually
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Fuel was shutoff, fire was going on for a very long time.
To me, the fire is quite subdued - and is diminishing all during that clip. Could it be there was still fuel in the lines between the shut-off and the engine? Could it be other oil lines or hydraulic lines feeding it?
People really need to stop hypothesising and just wait for those who actually know something have a look and tell us.
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Are you somehow sure it was Boeing's fault?
Yeah, only 777's with the Pratt & Whitney engine are grounded.
So you're saying it is somehow the 777's fault?
You would be totally comfortable getting on an Airbus with PW4000s, or a 747? :o
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Are you somehow sure it was Boeing's fault?
It's a Pratt & Whitney Dependable Engine fitted on that thing, and serviced by UAL's maintenance team.
It's the optics of it.
Well, yeah, especially with the current narrative of "Boeing = Bad."
Another PW4000 series on a 747 shed its guts over the Netherlands the same day.. and another United flight (a 737 this time, not a P&W engine) had an engine failure, also the same day. Most aren't going to care about what engine it was - three more Boeings went bad all in one day.
So you'd also be another person who would be comfortable right now getting on an Airbus with PW4000 engines because it is obviously Boeing's fault that the P&W engine failed catastrophically on a UAL flight? ::)
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Are you somehow sure it was Boeing's fault?
Yeah, only 777's with the Pratt & Whitney engine are grounded.
So you're saying it is somehow the 777's fault?
You would be totally comfortable getting on an Airbus with PW4000s, or a 747? :o
You got that the wrong way around.
777's with the Pratt & Whitney engine are grounded. All 777's with other engines haven't been grounded.
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Are you somehow sure it was Boeing's fault?
Yeah, only 777's with the Pratt & Whitney engine are grounded.
So you're saying it is somehow the 777's fault?
You would be totally comfortable getting on an Airbus with PW4000s, or a 747? :o
You got that the wrong way around.
I think you worded it the wrong way around. It doesn't seem like "Are you somehow sure it was Boeing's fault?", "Yeah" is what you really meant.
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Are you somehow sure it was Boeing's fault?
It's a Pratt & Whitney Dependable Engine fitted on that thing, and serviced by UAL's maintenance team.
I'm not drawing any conclusion at this point. Only full proper investigation will. All we know is, as said above, all 777's with those engines are now grounded. So, sad times for Boeing. It certainly won't help restoring confidence or help Boeing's business.
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Fuel was shutoff, fire was going on for a very long time.
To me, the fire is quite subdued - and is diminishing all during that clip. Could it be there was still fuel in the lines between the shut-off and the engine? Could it be other oil lines or hydraulic lines feeding it?
People really need to stop hypothesising and just wait for those who actually know something have a look and tell us.
At this point, all there can be is speculation and conjecture.
Although amazingly, one blade piece was found in a soccer field in Broomfield and shows signs of metal fatigue.
"Under a microscope, Sumwalt said, "You can actually count the number of (flight) cycles since the initiation of that fatigue."
The fire I think is a second problem, imagine if the plane had to dump fuel.
{NTSB Chair} Robert Sumwalt said "We do have indications that the fuel to the engine was turned off, so we will be looking to see what would have continued to propagate a fire".
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Fuel was shutoff, fire was going on for a very long time.
To me, the fire is quite subdued - and is diminishing all during that clip. Could it be there was still fuel in the lines between the shut-off and the engine? Could it be other oil lines or hydraulic lines feeding it?
People really need to stop hypothesising and just wait for those who actually know something have a look and tell us.
At this point, all there can be is speculation and conjecture.
Although amazingly, one blade piece was found in a soccer field in Broomfield and shows signs of metal fatigue.
"Under a microscope, Sumwalt said, "You can actually count the number of (flight) cycles since the initiation of that fatigue."
The fire I think is a second problem, imagine if the plane had to dump fuel.
{NTSB Chair} Robert Sumwalt said "We do have indications that the fuel to the engine was turned off, so we will be looking to see what would have continued to propagate a fire".
The misconceptions surrounding the dumping of fuel are covered in the Blancolirio video posted above by WattsThat.
A reasonably thorough description of the flight reverser mechanism where the flames from the burning hydraulic or lubrication oil can be seen is in the AgentJayZ video posted even earlier above, also by WattsThat.
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Note they had another engine fire the same day on a 747: https://www.euronews.com/2021/02/22/two-people-injured-by-debris-after-boeing-747-suffers-engine-fire-over-netherlands (https://www.euronews.com/2021/02/22/two-people-injured-by-debris-after-boeing-747-suffers-engine-fire-over-netherlands)
Apparently the same engines. That's very unlucky.
There were previous similar incidents in the past. Investigation will tell if they are at all related.
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Apparently that's a titanium fire in the video :o
A titanium fire is BLINDING white. That was apparently a composite thrust reverser component that was closer to smouldering than burning.
Jon
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There are three main variants of the PW4000, the variant used on the B777 is only used on the B777, and the fan design and diameter is one of the major differences. I'm not sure since public information is a bit scattered and sparse, but I believe the -112 version is the only one with hollow fan blades. Since this was a fan failure, it stands to reason they would only ground engines with similar fan construction.
Bad luck for Boeing, indeed. Not their 'fault' of course, but I wouldn't say they don't deserve it anyway.
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Sad days for Boeing really.
https://www.nbcnews.com/news/us-news/faa-orders-stepped-inspections-boeing-777s-after-engine-failure-united-n1258477 (https://www.nbcnews.com/news/us-news/faa-orders-stepped-inspections-boeing-777s-after-engine-failure-united-n1258477)
Must have been a special experience for the passengers. Seeing that through the windows:
That's a sight that you don't see very often! The fact that the engine stayed together (well mostly) and was still running is a testament to it's ruggedness. Mostly, I would call this event a success.
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Apparently that's a titanium fire in the video :o
A titanium fire is BLINDING white. That was apparently a composite thrust reverser component that was closer to smouldering than burning.
Jon
there might be some titanium burning in there keeping it alive because think about how fast that plane is going and how thin the air is getting and its not going out. Its like keeping a cigarette lighter lit outside the car window on a freeway not the easiest thing I would imagine. It is going 600 miles per hour,.. though I guess it normally does burn while going at 600MPH and I don't know if there are active mechanisms to keep it lit, or if it works when its all exposed on the same principles. If I recall windproof pocket torch lighters are tested to like 60 MPH. I know they have assists that help them reignite when its raining. I think usually though keeping it burning and spinning is better? Though if it burns the wing it can burn the control routing for the flaps or whatever it has on the wing or on other planes with more engines it can burn the fuel going to the engines that are not shut off so its more important for the fire to go out there ? (b52 comes to mind). I wonder if that one can shut off just one engine or if it does the whole wing (i.e. do planes pump fuel to a engine across another engine that is clearly on fire ?).
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It's unnerving to see a wide band of flame for such a long time. With that much airflow, it can creep. I thought it was the housing, but there might be hexagonal-celled insulation on the thrust reverser that was the candle wick. The fuel hose and fittings were found on the ground. As if we know the construction here.
Repairs on the smaller 94"/100": http://training.egyptair.com/Content/Download/CourseMaterials/PW4000%2094-100%20CONFERENCE%202019%20-%20DAY%202.pdf (http://training.egyptair.com/Content/Download/CourseMaterials/PW4000%2094-100%20CONFERENCE%202019%20-%20DAY%202.pdf)
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how does it stay burning at 600mph? it must be either very flammable, very hot or pilot lighted by something
is the engine like still sustaining itself by oil dripping into the middle and igniting and the flame being pushed out to make it look like its on fire on the outside despite the outside not burning? i.e. combustion occurs in the same place as it does with the fuel but instead occurs with residual oils but the amount of fire is excessive so it gets pushed out, operating kinda like a reflux condenser, in terms of liquid being sucked into the middle then fire being pushed out, not in the sense of condensation?
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An explanation I heard was that hydraulic fluid or oil is present in that area. The significant internal failure of the engine may have ruptured some pipes and the engine is consuming those fluids.
However I don't know if the engines have independent hydraulic fluid supplies for the thrust reverser and any other actuators, because I don't recall the pilots reporting a hydraulics failure.
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https://www.youtube.com/watch?v=jh4727krwH4 (https://www.youtube.com/watch?v=jh4727krwH4)
Also of note:
Hey Juan, really enjoy your reporting. I'm a career engineer here at P&W in East Hartford. Dialed in to a zoom call with out President (Chris Calio) today and he stated all Hollow Fan Blade segments have been recovered and are in our lab in East Hartford. Just passing this along, thanks.
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An explanation I heard was that hydraulic fluid or oil is present in that area. The significant internal failure of the engine may have ruptured some pipes and the engine is consuming those fluids.
However I don't know if the engines have independent hydraulic fluid supplies for the thrust reverser and any other actuators, because I don't recall the pilots reporting a hydraulics failure.
do they end up having thrust from the oil being leaked into them?
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how does it stay burning at 600mph? it must be either very flammable, very hot or pilot lighted by something
is the engine like still sustaining itself by oil dripping into the middle and igniting and the flame being pushed out to make it look like its on fire on the outside despite the outside not burning? i.e. combustion occurs in the same place as it does with the fuel but instead occurs with residual oils but the amount of fire is excessive so it gets pushed out, operating kinda like a reflux condenser, in terms of liquid being sucked into the middle then fire being pushed out, not in the sense of condensation?
The aircraft isn't travelling at 600mph, nor is its indicated airspeed (which would represent how much the fire 'feels' the air) 600mph. They would've been at an IAS of about 280kts or 322mph. Ground speed would have been somewhat higher, maybe 320kts. They were fairly low in the climb, not at altitude in cruise.
Where you see the fire emanating from is the thrust reverser 'translating sleeve' with many vanes to redirect the air to the rear. The thrust reverser doors appear to be closed, so no significant airflow from the fan duct (or fuel or anything else from the engine core) can reach this area in this configuration. Since the purpose of these vanes is to direct air rearward, the pockets are 'out of the wind' so to speak, and yeah maybe there is an element of negative pressure helping to suck fuel from whatever the fuel source is. From the reports so far, it doesn't sound like there were any major fuel leaks and the fuel shutoffs worked as designed, so I'd guess this is either residual fuel from ruptured lines or hydraulic oil, possibly from the TR mechanism itself, but could be anything mounted on the outside of the engine. This will be a focus of the investigation for sure.
It's definitely not that you're seeing combustion in the core, the TR doors are closed, and even if they were open, you'd only see inside the fan duct, not the core. Any flame you might observe (extremely unlikely) inside the combustion chambers due to catastrophic damage would be much deeper inside the engine than is observed here which is clearly near the surface. If that were happening, you'd probably see it inside the fan duct as well from the front/rear.
Thrust from this would be negligible, it's clearly not a very significant amount of fire, and it's happening in 'free air'.
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how does it stay burning at 600mph? it must be either very flammable, very hot or pilot lighted by something
is the engine like still sustaining itself by oil dripping into the middle and igniting and the flame being pushed out to make it look like its on fire on the outside despite the outside not burning? i.e. combustion occurs in the same place as it does with the fuel but instead occurs with residual oils but the amount of fire is excessive so it gets pushed out, operating kinda like a reflux condenser, in terms of liquid being sucked into the middle then fire being pushed out, not in the sense of condensation?
The aircraft isn't travelling at 600mph, nor is its indicated airspeed (which would represent how much the fire 'feels' the air) 600mph. They would've been at an IAS of about 280kts or 322mph. Ground speed would have been somewhat higher, maybe 320kts. They were fairly low in the climb, not at altitude in cruise.
Where you see the fire emanating from is the thrust reverser 'translating sleeve' with many vanes to redirect the air to the rear. The thrust reverser doors appear to be closed, so no significant airflow from the fan duct (or fuel or anything else from the engine core) can reach this area in this configuration. Since the purpose of these vanes is to direct air rearward, the pockets are 'out of the wind' so to speak, and yeah maybe there is an element of negative pressure helping to suck fuel from whatever the fuel source is. From the reports so far, it doesn't sound like there were any major fuel leaks and the fuel shutoffs worked as designed, so I'd guess this is either residual fuel from ruptured lines or hydraulic oil, possibly from the TR mechanism itself, but could be anything mounted on the outside of the engine. This will be a focus of the investigation for sure.
It's definitely not that you're seeing combustion in the core, the TR doors are closed, and even if they were open, you'd only see inside the fan duct, not the core. Any flame you might observe (extremely unlikely) inside the combustion chambers due to catastrophic damage would be much deeper inside the engine than is observed here which is clearly near the surface. If that were happening, you'd probably see it inside the fan duct as well from the front/rear.
Thrust from this would be negligible, it's clearly not a very significant amount of fire, and it's happening in 'free air'.
afaiu the thrust reverser part that is on fire is made of carbonfiber
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Further information today regarding this series of engines on 777s from Blancolirio, a trustworthy source...
https://www.youtube.com/watch?v=5hyP07BJAic (https://www.youtube.com/watch?v=5hyP07BJAic)
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It's obviously not Boeing's fault, but it still reflects badly on them simply because most people don't understand that Boeing doesn't build the engines.
On the other hand, engine failure was mostly contained and the plane landed safely with nobody hurt. That's close to the best possible outcome of something like this.
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isent it up to boeing to analyze the engine to make sure its good? They vet the subassembly after all. It will be complicated to figure out whos fault it is
i.e.
lack of maintenance
incorrect maintenance
bad from factory
1) design flaw
2) manufacturing defect (QC fail)
installed incorrectly/damaged during installation
system interfaced incorrectly (the engine has I/O), or its just not compatible with the design for whatever mechanical reason, if its not related to hydraulics or electronics or telemetry
failed to inspect device before/after installation
failed to perform more stringent tests
control safety system fail (did not monitor telemetry or handwaving was involved)
of course its up to the investigators to find out what happened
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isent it up to boeing to analyze the engine to make sure its good? They vet the subassembly after all. It will be complicated to figure out whos fault it is
No, the special sonic + thermal imaging tests are only performed at Pratt & Whitney's manufacturing facility when fan blade inspections are required,
i.e.
lack of maintenance
incorrect maintenance
bad from factory
1) design flaw
2) manufacturing defect (QC fail)
installed incorrectly/damaged during installation
system interfaced incorrectly (the engine has I/O), or its just not compatible with the design for whatever mechanical reason, if its not related to hydraulics or electronics or telemetry
failed to inspect device before/after installation
failed to perform more stringent tests
control safety system fail (did not monitor telemetry or handwaving was involved)
of course its up to the investigators to find out what happened
Did you watch the video? The tests are explained in there. It is quite possibly the same issues as the UAL flight 1175 blade failure, which was basically improper testing during inspection due to multiple factors at Pratt & Whitney.
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isent it up to boeing to analyze the engine to make sure its good? They vet the subassembly after all. It will be complicated to figure out whos fault it is
i.e.
lack of maintenance
incorrect maintenance
bad from factory
1) design flaw
2) manufacturing defect (QC fail)
installed incorrectly/damaged during installation
system interfaced incorrectly (the engine has I/O), or its just not compatible with the design for whatever mechanical reason, if its not related to hydraulics or electronics or telemetry
failed to inspect device before/after installation
failed to perform more stringent tests
control safety system fail (did not monitor telemetry or handwaving was involved)
of course its up to the investigators to find out what happened
Oh, for crying out loud - no, it's NOT Boeing at fault here. Maybe some maintenance procedures - but they would not have originated from Boeing responsible components.
When purchasing a plane, there are two steps: 1. Choose the airframe and 2. Choose the engines. For a Boeing 777, I believe there are 3 choices of engine - Pratt & Whitney, Rolls Royce or GE.
Boeing don't make engines. They make airframes. The engine had a failure. The airframe held up very nicely.
Pratt and Whitney are the ones with egg on their face at the moment.
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Oh, for crying out loud - no, it's NOT Boeing at fault here. Maybe some maintenance procedures - but they would not have originated from Boeing responsible components.
If my TV breaks I wouldn't say "Its not LG's fault. They didn't make the component that broke.". Anyone integrating parts into a product is responsible for the whole product.
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Oh, for crying out loud - no, it's NOT Boeing at fault here. Maybe some maintenance procedures - but they would not have originated from Boeing responsible components.
If my TV breaks I wouldn't say "Its not LG's fault. They didn't make the component that broke.". Anyone integrating parts into a product is responsible for the whole product.
That is not at all the way it works in the aircraft industry.
Boeing doesn't do the fancy inspections necessary to maintain or overhaul the engines. That is entirely the engine manufacturer's domain. Boeing quite literally have nothing to do with it other than having the misfortune of having offered that particular engine as one of the options to the purchaser of the aircraft.
There is absolutely nothing, zero, zip, nada, that Boeing could have done to somehow find this issue.
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Oh, for crying out loud - no, it's NOT Boeing at fault here. Maybe some maintenance procedures - but they would not have originated from Boeing responsible components.
If my TV breaks I wouldn't say "Its not LG's fault. They didn't make the component that broke.". Anyone integrating parts into a product is responsible for the whole product.
so the explanation I read in this thread makes me think the profession I took is way too complicated because it seems easier to pick a plane engine then a damn single resistor. I can't even do that. I can still fuck a resistor choice in a way that they will blame me. I just know unless I do a fair bit of thinking someone is going to come out of the wood work and tell someone 'you needed a more experienced guy to make that part placement decision for you because'... then it will come down to if a company feels like defending me. Not saying its hard or likely to happen but I still need to usually consider some things other then the description on the digikey baggie if its serious.
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If my TV breaks I wouldn't say "Its not LG's fault. They didn't make the component that broke.". Anyone integrating parts into a product is responsible for the whole product.
A TV is not an airliner, not even close. When purchasing a TV you don't get to choose what brand of power supply it includes. The situation with an airliner is more like what you have with outboard powered boats. The outboard motor may be included as part of a package deal, but you will choose the specific motor that you want installed, and if the motor blows up that isn't the fault of the boat builder, you take it up with the manufacture of the motor you selected or the dealer you purchased it from.
Turbine engines are incredibly complex and expensive machines, large ones cost tens of millions of dollars each. The engines and ancillary components are a package deal engineered by the engine manufacture, the airframe manufacture does the integration, providing the mounting brackets and fairings and such. If an engine needs to be serviced, technicians trained to work on that specific engine do the work, not the airframe manufacture, they don't design engines, they don't build engines, they don't service or support engines, they design and build airframes to support the engines the customer selects. If there is a problem with the engine, that is 100% the responsibility of the engine manufacture unless an airframe problem caused the engine to fail.
Unfortunately as has been illustrated here, ignorance of the general public is going to put egg on Boeing's face even though it is not deserved. People assume that a $320M aircraft is anything like a $400 consumer TV set or a family car.
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I remember a documentary a few years ago about Rolls Royce (the aircraft engine make, not the car maker).
They have a monitoring centre that monitors telemetry all the engines they have in service whilst in flight. Presumably other manufacturers have the same (otherwise it would be a compelling reason to buy RR!). They provide constant monitoring data to the airlines about the state of their engines, real time information on any developing problems - vibration profiles, pressure abnormalities etc. together with immediate technical support.
In this respect, the engines are in-flight manufacturer supported entities in their own right - rather unlike a component in a TV.
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so the explanation I read in this thread makes me think the profession I took is way too complicated because it seems easier to pick a plane engine then a damn single resistor. I can't even do that. I can still fuck a resistor choice in a way that they will blame me.
Really?
You want to live in the aerospace world where each specific unit of each model of crimper that you use to make connections to pin terminals, even in some non-vital connector, must be sent out for calibration checks and re-certified every year and you have to track the serial numbers of every batch of every wire and every pin and connector housing you use, every other part and piece you use, so that when someone farther up the supply chain fucks up you know where to go to find out where else that same failure might possibly show up? It is an absolute nightmare when people up above "you" in this kind of highly-documented, high-reliability, traceable-at-every-stage screw up something which is why there is the whole traceability system in there in the first place.
The fact that improperly re-certified parts are apparently repeatedly being put back into service by Pratt & Whitney when they are going to end up sometimes failing catastrophically before their next inspection being blamed on Boeing (not that Boeing is some perfect saint, mind you) is totally disingenuous. This one is not Boeing's fault.
The fact that the clueless mass media narrative doesn't ever even attempt to make a distinction in cases like this so that even technically-minded engineer people are so hopelessly misled is frightening. Tupolev = Tragic, Boeing = Bad, Airbus = Awesome is a shortsighted view of the actual inner workings of the whole, incredibly complex (and astoundingly reliable, highly regulated) industry.
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Airbus = Awesome
AF447.
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The plane had flown under 3,000 cycles which is less than half before blade inspection is due at 6,500 cycles. It seems like a very long time between inspections. That engine has bigger, fewer turbine blades, hollow so maybe they pushed the tech too far and gave unicorn and rainbow inspection frequency to make the engines seem cheaper to maintain.
It could also be a manufacturing issue- nothing to do with engineering.
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Airbus = Awesome
AF447.
|O If ever there were an accident where it was appropriate to say 'it was completely pilot error', this is it. There's always blame to go around, and there were some HMI problems identified with the Airbus flight controls, but you really can't blame the airframe or control systems for a pilot continually doing the opposite of what they were trained to do and the procedures say to do for multiple minutes while they fly the plane into the sea. The pilots still have mostly ultimate authority, and if what they are actively doing is going to crash the plane, with the exception of alpha-prot, the airframe isn't going to stop them.
The plane had flown under 3,000 cycles which is less than half before blade inspection is due at 6,500 cycles. It seems like a very long time between inspections. That engine has bigger, fewer turbine blades, hollow so maybe they pushed the tech too far and gave unicorn and rainbow inspection frequency to make the engines seem cheaper to maintain.
This is my thought now that a bit more has come out. Since it's been so many cycles since the last inspection, it's going to be very interesting whether they decide the crack would have been detectable during the inspection or not. If they can figure it out, how it grew is going to play a major part here, but regardless it looks like the inspection window will probably be shrunk significantly if they can't identify and fix a problem with the inspection process itself.
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Airbus = Awesome
AF447.
|O If ever there were an accident where it was appropriate to say 'it was completely pilot error', this is it. There's always blame to go around, and there were some HMI problems identified with the Airbus flight controls, but you really can't blame the airframe or control systems for a pilot continually doing the opposite of what they were trained to do and the procedures say to do for multiple minutes while they fly the plane into the sea. The pilots still have mostly ultimate authority, and if what they are actively doing is going to crash the plane, with the exception of alpha-prot, the airframe isn't going to stop them.
I attribute a degree of blame to Airbus because the pilots (neither particularly good, clearly) were unable to accept they were in a stall because it's an Airbus, and it won't let you stall. Except when it does.
And yes, it was pilot error. Like most pilot errors, there are contributing factors.
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I attribute a degree of blame to Airbus because the pilots (neither particularly good, clearly) were unable to accept they were in a stall because it's an Airbus, and it won't let you stall. Except when it does.
And yes, it was pilot error. Like most pilot errors, there are contributing factors.
Usually I'm with you on there being multiple critical factors to blame, I just don't really think that was the case in this accident to the degree it usually is. They identified the unreliable airspeed early on, and understood it later in the sequence, yet never completed the associated procedure nor were their control responses appropriate for that condition. They didn't discuss the stall alarms at all, which is pretty strange, but doesn't lead to the conclusion that they thought they could ignore the continuous stall alarm because they were in normal law; they also called out the shift to alternate law, though I agree it could have easily been missed. There's no excuse for not executing the stall recovery procedure (or even earlier, the unreliable airspeed procedure - some of the items were performed but it was not done in the expected challenge/response systematic manner, nor completed), nor for the PNF to continually provide control inputs after giving the controls to the Captain - or this was a CRM failure where they had conflicting interpretations of who was in control, but regardless it is a piloting issue.
Confusion in complex failures is a relatively common cause of accidents, and I'm usually the first to defend the pilots in a situation with conflicting alarms and information, but in this case the only alarm they were getting initially was STALL STALL, and their conditioned response to that should be to execute a stall recovery or if they were actually looking at their PFD, maybe unusual attitude recovery could be justified. And the only unreliable indication they were receiving was airspeed, which recovered shortly after the incident began. It appears they just completely ignored the attitude indicator they should have known they could trust, as well as the repeated stall warnings. Suspecting unreliable airspeed seems to have led them to mistrust the airplane entirely and ignore everything else it was telling them, and that's not defensible, especially in hard IMC.
The only places where the aircraft could arguably have done a better job IMO would be not suppressing the stall alarm below 60KIAS, and kicking the flight directors completely off when the data was invalid, rather than restoring them as the data came back, but by the time the incident evolved that far, they should have already executed the stall recovery procedure. Even after it did get that far, getting out of stall and back to a normal attitude should be overriding anything else in their minds. Regardless of anything else, including airspeed which was suspect, it would have been obvious they were at an extreme nose up attitude that would lead to stall. You could argue the pilots should have visibility of AoA data, but this isn't unique to Airbus, and they certainly didn't need it to tell them they were stalling the plane, the plane did that all on its own, as would have their attitude indicator.
The BEA didn't request any changes to the airplane as a result of the accident, and I think that's pretty clear indication they don't think any part of it was causal here. It's just bad pilot decision making from the Captain's laissez faire attitude about the weather, to not executing the unreliable airspeed procedure, to ignoring the stall warnings, to applying inappropriate control inputs, to continuing to apply those inputs after the Captain ostensibly took control.
Anyway, apologies for dragging this off topic, just get tired of people bringing up AF447 as if it's clearly the fault of Airbus; even with the most generous interpretation, the airplane plays a minor part in this accident.
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I attribute a degree of blame to Airbus because the pilots (neither particularly good, clearly) were unable to accept they were in a stall because it's an Airbus, and it won't let you stall. Except when it does.
And yes, it was pilot error. Like most pilot errors, there are contributing factors.
Usually I'm with you on there being multiple critical factors to blame, I just don't really think that was the case in this accident to the degree it usually is. They identified the unreliable airspeed early on, and understood it later in the sequence, yet never completed the associated procedure nor were their control responses appropriate for that condition. They didn't discuss the stall alarms at all, which is pretty strange, but doesn't lead to the conclusion that they thought they could ignore the continuous stall alarm because they were in normal law; they also called out the shift to alternate law, though I agree it could have easily been missed. There's no excuse for not executing the stall recovery procedure (or even earlier, the unreliable airspeed procedure - some of the items were performed but it was not done in the expected challenge/response systematic manner, nor completed), nor for the PNF to continually provide control inputs after giving the controls to the Captain - or this was a CRM failure where they had conflicting interpretations of who was in control, but regardless it is a piloting issue.
Confusion in complex failures is a relatively common cause of accidents, and I'm usually the first to defend the pilots in a situation with conflicting alarms and information, but in this case the only alarm they were getting initially was STALL STALL, and their conditioned response to that should be to execute a stall recovery or if they were actually looking at their PFD, maybe unusual attitude recovery could be justified. And the only unreliable indication they were receiving was airspeed, which recovered shortly after the incident began. It appears they just completely ignored the attitude indicator they should have known they could trust, as well as the repeated stall warnings. Suspecting unreliable airspeed seems to have led them to mistrust the airplane entirely and ignore everything else it was telling them, and that's not defensible, especially in hard IMC.
The only places where the aircraft could arguably have done a better job IMO would be not suppressing the stall alarm below 60KIAS, and kicking the flight directors completely off when the data was invalid, rather than restoring them as the data came back, but by the time the incident evolved that far, they should have already executed the stall recovery procedure. Even after it did get that far, getting out of stall and back to a normal attitude should be overriding anything else in their minds. Regardless of anything else, including airspeed which was suspect, it would have been obvious they were at an extreme nose up attitude that would lead to stall. You could argue the pilots should have visibility of AoA data, but this isn't unique to Airbus, and they certainly didn't need it to tell them they were stalling the plane, the plane did that all on its own, as would have their attitude indicator.
The BEA didn't request any changes to the airplane as a result of the accident, and I think that's pretty clear indication they don't think any part of it was causal here. It's just bad pilot decision making from the Captain's laissez faire attitude about the weather, to not executing the unreliable airspeed procedure, to ignoring the stall warnings, to applying inappropriate control inputs, to continuing to apply those inputs after the Captain ostensibly took control.
Anyway, apologies for dragging this off topic, just get tired of people bringing up AF447 as if it's clearly the fault of Airbus; even with the most generous interpretation, the airplane plays a minor part in this accident.
The problem I have with the Airbus design with its decoupled side sticks is perfectly illustrated in this incident - the pilot flying is mistaken, and is inputting full nose up on his control stick. The guy on the other side of the cockpit doesn't realize this, because he can push his stick full forward independently. The aural warning says something about the mixed control inputs, but that can be missed in the confusion. Boeing's control columns are coupled together - the guy in the right seat is going to know what the guy in the left seat is doing, because his control wheel moves in unison. From what I've read of that accident, it seems that at times the left seater was trying to lower the nose, but the right seater had control authority and so it stayed up. There'd have been no question how the controls were positioned in a Boeing craft, as BOTH the yokes would have been pulled back, and you can FEEL if the guy next to you is fighting you on the controls. Seems to be a fundamental design flaw in the controls that can rise up under confusing/stressful situations to bite you hard in the ass, permitting erroneous control inputs where one side has no idea what the other is doing, as we saw here.
-Pat
<edit - switched seats>
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Anyway, apologies for dragging this off topic, just get tired of people bringing up AF447 as if it's clearly the fault of Airbus; even with the most generous interpretation, the airplane plays a minor part in this accident.
It's not clearly the fault of Airbus, I just don't hold that "Airbus = awesome". The whole concept of preventing the pilot from making improper control inputs and applying flying skill right up until the moment those skills are necessary is, in my opinion, a mistake, and one I believe contributed to that incident, among others. AF296, perhaps - yes, pilot error, compounded by "the computer will protect us" (the whole point of the demonstration) and "oh crap, the computer won't let me pull up".
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The problem I have with the Airbus design with its decoupled side sticks is perfectly illustrated in this incident - the pilot flying is mistaken, and is inputting full nose up on his control stick. The guy on the other side of the cockpit doesn't realize this, because he can push his stick full forward independently. The aural warning says something about the mixed control inputs, but that can be missed in the confusion. Boeing's control columns are coupled together - the guy in the right seat is going to know what the guy in the left seat is doing, because his control wheel moves in unison. From what I've read of that accident, it seems that at times the left seater was trying to lower the nose, but the right seater had control authority and so it stayed up. There'd have been no question how the controls were positioned in a Boeing craft, as BOTH the yokes would have been pulled back, and you can FEEL if the guy next to you is fighting you on the controls. Seems to be a fundamental design flaw in the controls that can rise up under confusing/stressful situations to bite you hard in the ass, permitting erroneous control inputs where one side has no idea what the other is doing, as we saw here.
I do very much prefer the Boeing cockpit layout. Although I am not a pilot myself, mechanically coupling the controls on both seats is one of those things that just seems like an obviously good idea. I also think a yoke is a much more logical input device for something like an airliner than a stick, but again I'm not a pilot so I have not experienced either one outside of PC simulators.
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Anyway, apologies for dragging this off topic, just get tired of people bringing up AF447 as if it's clearly the fault of Airbus; even with the most generous interpretation, the airplane plays a minor part in this accident.
It's not clearly the fault of Airbus, I just don't hold that "Airbus = awesome". The whole concept of preventing the pilot from making improper control inputs and applying flying skill right up until the moment those skills are necessary is, in my opinion, a mistake, and one I believe contributed to that incident, among others. AF296, perhaps - yes, pilot error, compounded by "the computer will protect us" (the whole point of the demonstration) and "oh crap, the computer won't let me pull up".
Fair enough. Planes still crash occasionally, so none of them are awesome yet :-+.
Pilots definitely need experience hand flying regardless of airframe, but outside of the sim they're not going to and shouldn't have much experience flying on the edge of the envelope or in multiple failure scenarios. A 737 pilot is going to have no more experience riding the stick shaker than an A320 pilot will in alternate or direct law, but both pilots need to know what to do if they end up in those situations. Aside from the 737 and 767, Boeing has at least caught up on their control systems, so I don't think there is much between them on their modern designs (which does not include 737MAX). I think the next major Airbus design will probably have force feedback on the sticks that will at least be used to more clearly communicate DUAL INPUT, but they will probably still rely on the priority switch to deal with that, rather than having pilots fight each other.
AF296 was so irresponsible that I'd call it criminally negligent (and the courts agreed); the Captain's overconfidence is on him, not the plane. Alpha prot and alpha floor are protections, they shouldn't be something you intentionally include in your flight plan, and double especially not when already very low and slow with the engines at idle and with one of those protections disabled. If you wouldn't hand-fly it without any protections at all, you shouldn't fly it. The protections in that incident worked exactly as designed, and protected against the stall he was trying to initiate; the reason they crashed wasn't because he couldn't pull up, it was because he made the call too late for the idle engines to provide enough thrust to climb out with the dangerous low energy state he'd put the aircraft in. The only alternative would have been it letting him stall it, and who knows how that would have turned out. It doesn't matter what type of aircraft you're flying, or whether it prevents you from stalling it or not, low and slow is a dangerous regime.
I do very much prefer the Boeing cockpit layout. Although I am not a pilot myself, mechanically coupling the controls on both seats is one of those things that just seems like an obviously good idea. I also think a yoke is a much more logical input device for something like an airliner than a stick, but again I'm not a pilot so I have not experienced either one outside of PC simulators.
Counterpoint: yokes get in the way of other controls, displays, charts, etc, are more cumbersome to operate one-handed, so they are noticeably less ergonomic, and both sides could be jammed simultaneously by an incapacitated pilot, in which case your only recourse is to un-jam them.
There's a more fundamental difference though, which I think is usually more what people are referring to when they compare the two. The Boeing design (ex. 787) has the controls coupled approximately to the deflection of the control surfaces as in a classical airplane. Want to execute a turn? Hold the yoke over to maintain the desired bank angle, pull back slightly to counter the loss of lift, and return it to centre when you want to roll out. In the Airbus design, the sidestick is instead (roughly speaking) coupled to roll/pitch rate, and the flight computer determines the deflection to achieve it, so you just roll the plane over to the desired bank angle, then release the side stick and the plane will maintain that bank angle and your previous pitch until you roll it back the other way. Likewise to climb you pull back to the desired attitude and then release until you want to level out when you push the nose forward. But even Boeing is getting on board with this as 787 has a similar rate-based model as Airbus, despite still having yokes.
The Boeing protections also work differently in a way that maybe depends a bit on the yoke itself, as the flight control system doesn't simply stop you if you try to command something unreasonable, it will fight you with strong force feedback, but you can override it all the way into stall, overbank, or I think overspeed if you push hard enough. Their philosophy is to inform about the envelope, but not to limit the inputs of the pilots even if they're about to violate it.
Which is better? Both have proponents, it seems to mostly come down to preference. I'm not an airline pilot either, but I can see how the rate-based design could reduce workload slightly during manual flight as you only need to provide input to change attitude, not to maintain it (even when faced with changing speed or wind), and it definitely makes it easier to take notes, deal with paper charts, and eat without a yoke in your lap. Those that prefer the more direct model see the fact that in certain multiple failure scenarios the Airbus controls may degrade to be more direct, and pilots are likely inexperienced with flying that way as a significant risk. Or that in some extremely unlikely scenarios it's possible the computers may be wrong and prevent you from doing something you need to do, and there is no way to override them on Airbus. And as we've discussed here, the lack of coupling between sticks, though force feedback to communicate this is available now in some sidestick aircraft (none from Airbus, AFAIK). I don't think the choice of yoke vs. sidestick itself has much in it, it's just a familiarity thing.
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Blancolirio’s interview with the captain of UAL 1175. Spoiler alert: this earlier fan blade failure was uncontained, unlike the failure over Denver. After watching this video, all I can say is wow, I did not know how close they were to ditching. So many things went the right way. Well worth the time to watch.
https://m.youtube.com/watch?v=J7_lzeY23dI (https://m.youtube.com/watch?v=J7_lzeY23dI)
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Fresh news today, a Rossiya Airlines 777 departed from Hong Kong to Madrid made an emergency engine warning landing in Moscow.
Indeed. Different engines though, those 777 are equipped with GE90 engines. Apparently this would be due to an engine sensor's fault.
Curious epidemic though.
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Can planes catch Covid??
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Can planes catch Covid??
I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
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Blancolirio’s interview with the captain of UAL 1175. Spoiler alert: this earlier fan blade failure was uncontained, unlike the failure over Denver. After watching this video, all I can say is wow, I did not know how close they were to ditching. So many things went the right way. Well worth the time to watch.
afaiu none of them were technically uncontained, the blade didn't go through the shield around the fan
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Can planes catch Covid??
I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
Yes, it is amazing how cars dislike being ignored - they are almost like ladies in that way! :D
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Can planes catch Covid??
I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
As Neil Young so wisely observed, Rust Never Sleeps.
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I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
My understanding is (based on what was said on one of the YouTube channels - I think it was Mentour Pilot) that engines are started every 3 weeks or so and also that commercial planes have to be flown every once in a while, otherwise they would loose their airworthiness certificate and have to be re-certified when they are put back into use.
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I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
My understanding is (based on what was said on one of the YouTube channels - I think it was Mentour Pilot) that engines are started every 3 weeks or so and also that commercial planes have to be flown every once in a while, otherwise they would loose their airworthiness certificate and have to be re-certified when they are put back into use.
Yes. I've heard from a couple specialists that planes sitting "idle" for weeks or even months was not that rare these days, even before the pandemic, due to large differences in trafic depending on the season for some companies. So they are normally used to take care of planes just parked for extended periods of time.
Now it'll still be interesting to know whether the Covid crisis did actually have an influence even on this routine maintenance. It's not at all unlikely. In particular, I'd really be curious to know if maintenance in general didn't significantly drop as air trafic droped... even though idle planes definitely need very regular maintenance. Whereas, as said above, this kind of maintenance was a common thing before Covid, the sheer number of parked planes has obviously increased a lot, so that increased this parked plane maintenance a lot, which companies were probably not ready for - while their revenue plumetted. So yeah. I'm curious if those incidents will at all tell us something about that.
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Yeah there are a lot of unknowns. Previously planes sat idle occasionally for weeks or months, but we have never had such a large number of planes sitting idle for so long. Makes me wonder how well they have all actually been taken care of. Hopefully it will turn out to not be a problem.
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Well, finally these 777s are allowed to fly passengers again: https://www.cnbc.com/2022/05/17/united-airlines-says-faa-cleared-grounded-boeing-777s-to-fly-again.html (https://www.cnbc.com/2022/05/17/united-airlines-says-faa-cleared-grounded-boeing-777s-to-fly-again.html)
I do wonder if failed engine blades of turbofan engines is going to be a more common theme. I also remember reading about another recent incident (Southwest_Airlines_Flight_1380 (https://en.wikipedia.org/wiki/Southwest_Airlines_Flight_1380)) with a 737. Totally different engine mfgr though, but nonetheless, the trend for turbofan is to go big.. get the largest bypass ratio you can make fit and produce reliably. Intuitively those longer fan blades will put more strain at the connection points to the axle. For the Southwest flight, it were mini cracks that caused failure, which has seen increased inspection measures to prevent them..
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I do have some concerns about planes sitting idle due to the pandemic. I had quite a bit of experience working with cars that sat for extended periods, it doesn't do them any favors. Seals dry out, lubricants degrade, metals oxidize, tires get flat spots, all sorts of stuff happens. I don't think I'd want to be on the first few flights on a plane that had been mothballed if I could help it.
My understanding is (based on what was said on one of the YouTube channels - I think it was Mentour Pilot) that engines are started every 3 weeks or so and also that commercial planes have to be flown every once in a while, otherwise they would loose their airworthiness certificate and have to be re-certified when they are put back into use.
Yes. I've heard from a couple specialists that planes sitting "idle" for weeks or even months was not that rare these days, even before the pandemic, due to large differences in trafic depending on the season for some companies. So they are normally used to take care of planes just parked for extended periods of time.
Now it'll still be interesting to know whether the Covid crisis did actually have an influence even on this routine maintenance. It's not at all unlikely. In particular, I'd really be curious to know if maintenance in general didn't significantly drop as air trafic droped... even though idle planes definitely need very regular maintenance. Whereas, as said above, this kind of maintenance was a common thing before Covid, the sheer number of parked planes has obviously increased a lot, so that increased this parked plane maintenance a lot, which companies were probably not ready for - while their revenue plumetted. So yeah. I'm curious if those incidents will at all tell us something about that.
There has to be a business opportunity here... have a courier company fly the parked planes on rotation for light cargo, or something like that...
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Oh, I can smell the business opportunity here... new companies selling plane pooling services.
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Oh, I can smell the business opportunity here... new companies selling plane pooling services.
You've basically described wet leasing.
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I do wonder if failed engine blades of turbofan engines is going to be a more common theme. I also remember reading about another recent incident (Southwest_Airlines_Flight_1380 (https://en.wikipedia.org/wiki/Southwest_Airlines_Flight_1380)) with a 737. Totally different engine mfgr though, but nonetheless, the trend for turbofan is to go big.. get the largest bypass ratio you can make fit and produce reliably. Intuitively those longer fan blades will put more strain at the connection points to the axle. For the Southwest flight, it were mini cracks that caused failure, which has seen increased inspection measures to prevent them..
I'd like to see turboprop make a comeback for large airliners. While not as fast, they're considerably more efficient than turbofans, the controllable blade pitch offers significant advantages. I remember reading that the fuel burn on a Q400-8 is around 25% lower than a comparable turbofan jet. I think they look cooler too.
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I doubt it would ever make economical sense. The "life" of the aircraft is one of the significant costs you pay for when you fly. Would you pay 2x more per flight to get to your destination more slowly? Not to mention ETOPS certification for a twin turboprop is uncommon so it would be restricted to internal flights only - might work for USA but unlikely to work well for European carriers.
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I also don't think they are actually more efficient during the cruise phase. They get used for short-haul flights because their efficiency in the dense air near the ground, and therefore for takeoff and climb, is somewhat better. There is not enough time in cruise on these short haul flights for the high altitude efficiency of turbofans to make up for their poorer efficiency in the climb, and most of the flight time is not affected by the higher speed too (taxi, takeoff, climbout are a significant part of such flights, and more or less fixed-time). So for such flights, they will not take much longer but will use less fuel than with a jet. The longer the flight, the more the cruise advantage matters, and there will be a turning point somewhere where the jet wins. And it's faster too.
There are also a lot of time-based costs that would need to be factored into it too, if you're taking about the nearly 50% slower cruise speed. Fewer destinations accessible with a single crew, crew hours, time on the airframe and engines for maintenance, the need for a larger fleet to service the same routes, and so on.
I also wonder if it's even technically feasible to build a long-range widebody turboprop. You'd probably have to start getting into weird things like contra-rotating props and stuff to put enough thrust on the wing to carry the extra fuel and passengers, which seems like it's inviting mechanical issues. Turboprops are already more mechanically complex than turbofans, and this wouldn't be helping.
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Sad days for Boeing really.
https://www.nbcnews.com/news/us-news/faa-orders-stepped-inspections-boeing-777s-after-engine-failure-united-n1258477 (https://www.nbcnews.com/news/us-news/faa-orders-stepped-inspections-boeing-777s-after-engine-failure-united-n1258477)
Somebody give the pilots a huge bonus and a medal of honor (or whatever they call the local equivalent).
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I think the ETOPS rating is a pretty big deal for airliners, especially the larger ones. Even though the ETOPS rating is minutes, it's about being able to fly safely with 1 engine into an alternate airport with 1 engine (=range, nm). The turboprop engines may be more fuel efficient but they also tend to fly at a lower Mach number while doing so. I'm sure they can get a ETOPS rating on the airplane given the resources, you got to wonder why would you? If a turboprop flies at half the speed, then an ETOPS-370 rating of the A350XWB halves to that of a pretty mainstream jet with ETOPS-180 rating (A320, 737, etc.).
Or in other words, the plane has to divert it's routing to fly over anything but a small puddle of water. The 777 is often used to fly routes over or close to the north pole, and newer planes will only go on more direct routes. The A350XWB has a ETOPS-370 rating and claims to be able to fly 99.7% of earth's surface in 1 trip, e.g. do flights like Sydney-London without any intermediate stops, etc. Taking those shortcuts also saves fuel.
And any of those long haul flight you might do, may now take 36hrs instead of 18hrs, probably requiring close to a dozen pilots onboard (and also some serious safety/health concerns of locking a few hundred people in a big tube for 36hrs)
So I doubt we'll ever see them on large airliners again. Economically it doesn't make sense, unfortunately.
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I don't think it would make sense on something as big as a 777, but something like the 737 or A320 size is certainly feasible and there are loads of those. The speed is also a lot more than half, the Q400-8 which is the only turboprop I've been on cruises at 360 knots, the 737-800 has a cruising speed of 444 knots, it's faster but not THAT much faster. The Russian TU-95 is the fastest and most powerful turboprop I'm aware of and cruises at 510 knots but being a military aircraft and 1950s technology I'm betting it is not particularly efficient and it certainly is not quiet. There are lots of short flights that operate 737s, and there are lots of smaller regional jets in similar sizes to currently operating turboprops but props seem largely to have gone out of fashion. Aesthetically I find them much more pleasing than jets and I like the sound they make better too.