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Charles posted:https://flightaware.com/live/flight/N772UA Well all of United’s PW 777s were grounded so I guess they had few direct replacement options.
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Feb 22, 2021 19:39
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Charles posted:https://flightaware.com/live/flight/N772UA Yeah, that plane isn't going anywhere for a while, I bet NTSB is having a field day.
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Feb 22, 2021 19:40
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hobbesmaster posted:That means the failure wasn't contained. Is the point to contain the failure, or just to contain the fan blade? Are the containment shields designed so that the engine can lose a couple of blades with absolutely no damage to anything outside the nacelle, or is it anticipated that the debris and vibration will rip panels off as happened in this case? Let's just be clear about the standards.
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Feb 22, 2021 19:40
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Sagebrush posted:Is the point to contain the failure, or just to contain the fan blade? It’s supposed to not damage the rest of the plane which clearly failed here.
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Feb 22, 2021 19:41
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CommieGIR posted:Yeah, that plane isn't going anywhere for a while, I bet NTSB is having a field day. Speaking of which they released a first update yesterday https://www.ntsb.gov/news/press-releases/Pages/MR20210221.aspx quote:Shortly after the NTSB was notified of the event, a senior NTSB investigator who lives in the Denver area began working with local law enforcement officials to coordinate the recovery of the components that separated from the engine, many of which landed in residential areas. Three other investigators from the NTSB's Denver regional office are assisting. I guess you don’t need to activate a go team if you live there already. edit: here’s a news article from today, they’re decommissioning the TWA-800 reconstruction which apparently has been used for training all these years https://www.ntsb.gov/news/press-releases/Pages/NR20210222.aspx hobbesmaster fucked around with this message at 19:48 on Feb 22, 2021 |
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Feb 22, 2021 19:46
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Sagebrush posted:Is the point to contain the failure, or just to contain the fan blade? The testing they normally do for fan failures usually keeps the cowling intact, so I'm assuming, especially as this one caused damage to the airframe, the question is going to come up whether engine panels and nacelle parts are being properly secured.
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Feb 22, 2021 19:47
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a patagonian cavy posted:One small trick to avoid an overweight landing after an uncontained engine failure (pilots HATE him!) I wish this weren’t too long for a new thread title
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Feb 22, 2021 20:10
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From what I remember all of the highly publicized engine failures over the past few years (this one, southwest, at least one other) all had failures where the containment system didn't work
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Feb 22, 2021 21:06
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normally when the containment system didn’t work, it’s a compressor losing a blade or having its disc fracture. nothing’s stopping that amount of energy. examples include: SWA1380 AAL383 QFA32 A fan blade fracturing shouldn’t escape- it’s a design requirement. There are lots of cool videos on YouTube of engine designers basically detonating portions of the fan blades to see if there’s a containment failure when that happens The fact that this United 777 had an uncontained failure means that either a fan blade broke and the containment system failed (very bad) or a compressor disc/blade failed and managed to take out a fan blade or two in the process.
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Feb 22, 2021 21:15
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a patagonian cavy posted:normally when the containment system didn’t work, it’s a compressor losing a blade or having its disc fracture. nothing’s stopping that amount of energy. examples include: Contained engine failures do make the news too occasionally: https://twitter.com/micahlifa/status/1148708669166628869?s=21
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Feb 22, 2021 21:27
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Excerpts from North Atlantic Cat: Here's three short chapters about coming back to North America in the belly of a BOAC Liberator. Our man had a fairly grueling flight to the UK in a Catalina from Bermuda; in the final leg he thought the Germans were spoofing his navigation beacon. STROOD is a radio command ordering all ferry aircraft to turn around and head back to the point of departure. In this case, it was because of unpredictably bad weather. Oh, and apparently the Liberator had a fun design quirk: it had one pneumatic pump operating all its pneumatics, on engine #3, the inboard engine on the port side. So failure on that engine was more serious than the other three.         
Nebakenezzer fucked around with this message at 21:54 on Feb 22, 2021 |
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Feb 22, 2021 21:33
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This seems relevant to the current discussion of contained failures etc. https://www.flightglobal.com/pictur...e/67818.article Through the cowl, packbay and stuck in the engine on the other side.
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Feb 22, 2021 21:55
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Kerosene19 posted:This seems relevant to the current discussion of contained failures etc. Yeah, that's an actual turbine disk, there's no real way to fully contain those like the fan blades, but drat is that an ugly failure and I hope they find out why because that shouldn't happen at all.
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Feb 22, 2021 22:42
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CommieGIR posted:Yeah, that's an actual turbine disk, there's no real way to fully contain those like the fan blades, but drat is that an ugly failure and I hope they find out why because that shouldn't happen at all. It was 15 years ago so I imagine they have a handle on it by now. 
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Feb 22, 2021 22:47
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hobbesmaster posted:It’s supposed to not damage the rest of the plane which clearly failed here. The wing root damage you see in that picture circulating around is almost certainly not a result of a separated fan blade; it's more than likely from a piece of the cowling that separated from the aircraft. It's too far aft to be a fan blade. I should also note that this still appears to have been a contained fan failure; the standard that the engine is held to is that the fan blade does not escape the containment system surrounding it, and nothing else. Another thought on this is, with regard to cowl separation; when the manufacturers are doing blade-off testing on these engines, it's on a static engine, often with some or all of the cowling off. With regard to the engine cowling, it's not really representative of flight conditions, not being in a 250-300 mile per hour breeze when the test is completed.
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Feb 22, 2021 23:11
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Nebakenezzer posted:Excerpts from North Atlantic Cat: Thanks for posting!
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Feb 22, 2021 23:57
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MrChips posted:I should also note that this still appears to have been a contained fan failure; the standard that the engine is held to is that the fan blade does not escape the containment system surrounding it, and nothing else. Thank you, that is what I was curious about.
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Feb 23, 2021 00:54
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Seams sketchy Ls in a Cessna 
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Feb 23, 2021 01:46
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blancolirio (777 pilot) just posted an update with some informed speculation based on past incidents and pictures of the damaged cowling from this one. He's got another angle which shows a long gash in the inlet ring which suggests that after the fan blade fractured and began to move, the aerodynamic forces on it accelerated it forwards and out of the engine. As it departed it sliced through the inlet ring, destroying its structural integrity. That damage would then be the initiator for the cowling breaking up under aerodynamic and vibration load. https://www.youtube.com/watch?v=EwNCCrjMmeg So if this holds up, I guess uncontained, but not due to failure of the containment system - it's just that real incidents are a bit messier than "the blade always tries to leave radially outwards".
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Feb 23, 2021 01:53
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BobHoward posted:blancolirio (777 pilot) just posted an update with some informed speculation based on past incidents and pictures of the damaged cowling from this one. He's got another angle which shows a long gash in the inlet ring which suggests that after the fan blade fractured and began to move, the aerodynamic forces on it accelerated it forwards and out of the engine. As it departed it sliced through the inlet ring, destroying its structural integrity. That damage would then be the initiator for the cowling breaking up under aerodynamic and vibration load. I wonder about there being two events then, the blade failure and then the cowling failure. In the ATC video the first call is relatively calm about an engine failure and needing to turn at 1:07 and you can hear one alarm in the background. Then the slightly more stressed maydays and a different alarm can be heard 15s later. So maybe the blade failed which was contained and the FADEC cut the engine followed 10-15s later by the fan blade causing the rest of the damage? Timestamp from this video https://www.youtube.com/watch?v=G7-zh7Sebr8
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Feb 23, 2021 02:17
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Preoptopus posted:Seams sketchy The key difference between auto engines and aero engines is that the aero engine is designed to run at 70% throttle or more for almost its entire operating life, and 100% for extended periods, while the auto engine is expected to be at like 15-25% most of the time with only short excursions above. Not to say that you can't successfully put car engines in airplanes, but doing so puts weird and unintended demands on the auto engine. Weird things will start to break in unexpected ways.
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Feb 23, 2021 02:31
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Sagebrush posted:The key difference between auto engines and aero engines is that the aero engine is designed to run at 70% throttle or more for almost its entire operating life, and 100% for extended periods, while the auto engine is expected to be at like 15-25% most of the time with only short excursions above. Which makes it even weirder/funnier that historically the most popular ones are the old VW engine. And before that the Model T engine.
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Feb 23, 2021 02:58
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MrChips posted:The wing root damage you see in that picture circulating around is almost certainly not a result of a separated fan blade; it's more than likely from a piece of the cowling that separated from the aircraft. It's too far aft to be a fan blade. I'm guessing that if a fan blade got shot out laterally and hit the fuselage, there would be an exit hole on the opposite side of the plane, too?
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Feb 23, 2021 03:11
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I'm betting that there's pieces of the fan stuck back there at the damaged wing root fairings. I just don't see the other cowling pieces having enough lateral force to get all the way over to the fairing. It will be interesting to follow the changes in testing for this failure mode. BobHoward posted:blancolirio (777 pilot) just posted an update with some informed speculation based on past incidents and pictures of the damaged cowling from this one. He's got another angle which shows a long gash in the inlet ring which suggests that after the fan blade fractured and began to move, the aerodynamic forces on it accelerated it forwards and out of the engine. As it departed it sliced through the inlet ring, destroying its structural integrity. That damage would then be the initiator for the cowling breaking up under aerodynamic and vibration load.
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Feb 23, 2021 03:58
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Kerosene19 posted:I'm betting that there's pieces of the fan stuck back there at the damaged wing root fairings. I just don't see the other cowling pieces having enough lateral force to get all the way over to the fairing. It will be interesting to follow the changes in testing for this failure mode. The fan cowls are giant lightweight prices of composite that are hinged at the top and secured together at the bottom like two big clamshells. If they were opened (or were broken) the relative wind would ABSOLUTELY be enough to do that kind of damage. The things are huge. The fairing between the fuselage and wing root is similarly lightweight, so it’s going to be vulnerable to any kind of impact. I’d be curious to see what the actual pressure vessel looks like under there.
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Feb 23, 2021 04:17
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Plastic_Gargoyle posted:Which makes it even weirder/funnier that historically the most popular ones are the old VW engine. My favorite Cessna swap is the TDI one, obvoously.
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Feb 23, 2021 05:17
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Plastic_Gargoyle posted:Which makes it even weirder/funnier that historically the most popular ones are the old VW engine. VW engines make a certain amount of sense for airplanes, since they're horizontally opposed and are air cooled, which means they're a hell of a lot easier to adapt to an airplane than something that's liquid cooled and inline. I assume the Model T engines were popular simply because they were common, cheap, had lots of aftermarket/spare parts available, and were designed to be reliable and easy to fix.
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Feb 23, 2021 09:09
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Sagebrush posted:The key difference between auto engines and aero engines is that the aero engine is designed to run at 70% throttle or more for almost its entire operating life, and 100% for extended periods, while the auto engine is expected to be at like 15-25% most of the time with only short excursions above. If you wanted to make O-360 power out of an LS engine, you'd really only be running it at 15%-25% throttle.
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Feb 23, 2021 17:22
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Safety Dance posted:If you wanted to make O-360 power out of an LS engine, you'd really only be running it at 15%-25% throttle. It would also let you have a WEP throttle setting!
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Feb 23, 2021 17:26
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hobbesmaster posted:It would also let you have a WEP throttle setting! And you get all the excitement of your propeller tips exceeding mach 1!
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Feb 23, 2021 17:47
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Safety Dance posted:If you wanted to make O-360 power out of an LS engine, you'd really only be running it at 15%-25% throttle. That's true, but I'm pretty sure that the guy putting an LS engine in a 172 is not doing it to make it perform like a 172.
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Feb 23, 2021 17:55
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Sagebrush posted:That's true, but I'm pretty sure that the guy putting an LS engine in a 172 is not doing it to make it perform like a 172. You can throw all the power in the world at a 172 and other than takeoff/climb performance it’ll still be a 110-120kt airplane. source: have tons of time in everything from 150-210hp 172s, they suck
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Feb 23, 2021 18:24
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azflyboy posted:VW engines make a certain amount of sense for airplanes, since they're horizontally opposed and are air cooled, which means they're a hell of a lot easier to adapt to an airplane than something that's liquid cooled and inline. And the VW engine was designed to run flat out at 70%+ rpm for hour after hour. That was part of Hitler's initial brief to Porsche - that the Volkswagen had to be able to cruise on the autobahn at 100kph, continuously, between fuel stops, and with the 40-litre fuel tank and the stipulated fuel economy of 7L/100km, that meant that the engine had to be able to run flat out for about six hours. Porsche deliberately both designed the VW engine to be 'overbuilt' (physically capable of handing way more power than the actual tune of the engine produced) and with deliberately inefficient breathing (restrictive inlet tract, sharp-angled inlet and exhaust ports, very unadventurous camshaft profiles and timing) so that the engine would run out of 'puff' before it was at risk of phyiscally damaging itself - it basically wouldn't be able to generate enough power to reach dangerous speeds or temperatures. That was then coupled to a deliberately tall top gear which was actually beyond the ability of the torque output of the engine to accelerate against once the Volkswagen was up at cruising speed. So on long autobahn trips the VW engine would be running at full throttle at a fixed 75%-ish of its redline RPM, which in turn was way below what the engine could actually stand, while the air-cooling made sure there were no hoses to split, pumps to break, radiators to leak or coolant to evaporate. So long as there was oil in the sump and the belt turning the cooling fan didn't snap it couldn't really go wrong. A lot of the power gains incorporated on later VW engines were just unlocking power that was always there but was restricted out. The later 'twin port' cylinder heads really only junked Porsche's original deliberately restrictive head design. The flat-twin engine in the Citroen 2CV was the same - especially designed to run at wide-open throttle under heavy loads for hours at a time. When you put a 9bhp engine in a car that's basically the only way you can drive it. The Citroen engine was conciously designed along the lines of a small aero-engine and used similar design features and very high-grade materials so it could reliably sit there churning out power as its exhaust manifolds glowed red and it put-put-ed along in top gear on the front of its torque curve at 40mph, foot to the floor. Unsurprising that both the VW and the Citroen engines are the ones favoured for conversion into light aircraft powerplants, really.
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Feb 23, 2021 18:27
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MrYenko posted:The fan cowls are giant lightweight prices of composite that are hinged at the top and secured together at the bottom like two big clamshells. If they were opened (or were broken) the relative wind would ABSOLUTELY be enough to do that kind of damage. The things are huge. The cowling itself is lightweight composite, but the framing is quite a bit heftier than that. We make some of the aft cowling frames for the GE9x engines on the 777x and they're solid titanium forged rings, even after they're machined down to net they weigh 15-20lbs a piece. Something like that flying off would do a ton of damage to the fuselage.
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Feb 23, 2021 18:33
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e.pilot posted:have tons of time in 172s, they suck 
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Feb 23, 2021 18:38
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e.pilot posted:You can throw all the power in the world at a 172 and other than takeoff/climb performance it’ll still be a 110-120kt airplane. turboprop 172
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Feb 23, 2021 18:41
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marumaru posted:turboprop 172 That's what a lot of bush pilots do, but its not about speed, its about the ability to to STOL, they still cruise fairly slow.
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Feb 23, 2021 18:45
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I’ve also flown 150hp 150s, they still cruise at the blistering speed of about 85kt. All the power in the world can’t do anything with poo poo aerodynamics.
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Feb 23, 2021 18:49
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e.pilot posted:You can throw all the power in the world at a 172 and other than takeoff/climb performance it’ll still be a 110-120kt airplane. Throw floats on it and you can fish where other people with less power can't!
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Feb 23, 2021 19:05
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hobbesmaster posted:Throw floats on it and you can fish where other people with less power can't! The future is now!  The future we really wanted: 
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Feb 23, 2021 19:06
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