Pic from slideshare.net Ok so whether you want to call it a cowl or nacelle. Time for a bit of useless info. Apparently a nacelle and a cowl/cowling are not the same thing. A cowl is a panel or part of an engine housing that can be removed for inspection. Or that directs airflow into the engine. A nacelle is a structure or housing outside the fuselage that holds engines or other equipment. A cowl just refers to an engine housing structure component. The nacelle is essentially the housing, which is part of the airframe I would think, that contains the engines and mounting structure onto some other part of the airframe other than directly on/in the fuselage. On a turbofan engine, and arguably/sometimes in other types of aero engines as well. The nacelle plays a part in not just containing the engine, attaching it to the fuselage, and transferring thrust loads and what not. But also plays a part in the how the engine produces thrust. The nacelle contains the ducting assembly that helps to decelerate incoming air, and in doing so also raises temperature which increases the speed of sound, before the fan, to avoid funny transonic and compressibility effects that would cause inefficiencies as the air passes thru the fan. The fan casing which is part of the engine closely shrouds the engine, and prevents spillage of air on the outside and also prevent vortexes forming at the tips of the blades and what not. There are then stator vanes aft of the fan, which also serve as structural components attaching the duct the part of the nacelle containing the core. These stator vanes help straighten the flow and turn rotational air motion into straight back motion, which helps improve efficiency. Something like that. Also something to do with static and dynamic pressure relationships. And finally, the duct then converges as it comes to an end. Which accelerates the flow again, compensating for the deceleration that was created at the front of the fan. Slow the air down/raise temp and speed of sound before the fan to avoid transonic/compressibility effects, straighten out the rotational flow, and reaccelerate the air to compensate for the deceleration and increase thrust. In addition to propulsion reasons, the duct and nacelle also have some other important purposes. Helps to some extent prevent FOD damage, helps reduce noise, blade failure containment, keeps fan protected from stuff and stuff (including people) protected from fan, houses systems such as anti-ice, accessories gearbox, starting system, bleed air, ayle & lube, engine indications systems like EGT and EPR, etc. etc. etc., and one other thing it houses the thrust reversers. So theres actually a ton going on in there, and it could weigh a few tons too. Nacelles are usually stuck on the wing in a large commercial airliner, and at the back end in not so large aircraft. Main reason being wing bending relief allowing weight savings to wing structure and what not. Also moment of inertia to prevent wing drop in stall, ease of access for maintenance, and other stuff. 
Pic from b737.org.uk OK so really what do we have inside the inlet / front end of an engine inlet cowl. In a large or medium commercial jet airliner. Anti - ice systems. Which is basically a hot air pipe coming from bleed air from the compressor. 5th stage and 9th stage, or something similar, from the high pressure or intermediate compressor. As you know when air is compressed it heats up. Due to work being done on it, thermodynamics, etc. etc. etc. The exact reason why it heats up I'm not sure, on a molecular level. But from our energy balance, if work is put in then it's internal energy must increase in addition to PV, therefore enthalpy. So PV an U increase, and therefore temperature. In addition to compression there are other irreversibilities, I imagine. Such as friction between the compressor blades and stator blades the air. And friction with the air and piping. And effects of vortexes and eddies within airflow turning into heat as they dissipate. Which also contribute to heat generated in the bleed air from compressor. 
Pic from slideplayer.com Arite so the engine produces enough enthalpy per unit time in the process of producing thrust that its able to take a relatively small portion to de-ice the engine cowl leading edge of the lip, wings, and stabilizers, by taking some of the energy from its engine compressor to divert to these surfaces. Now mind you this is actually a significant amount of power thats being taken to de-ice engine inlet cowl, wing, vertical and horizontal stab surfaces. Its a fairly large area that it adds up to. You've got forced convection from moving relative airflow taking heat away, and so heat has to be produced to compensate. And if at high altitude, although the air is less dense, the plane is (in most cases) moving faster so higher forced convection give or take. Also at higher altitude the air is colder, so that tends to also increase rate of heat removal from edge surfaces, even though air less dense. And when at higher altitude, the power produced by the engines in less overall, due to lower air density. Although the higher speed of the aircraft due to less dense air and less drag, as well as the lower temperature, tend to counteract that effect to some extent. So what does this mean ? The use of anti ice does take power, and a significant amount of power, from the engines. Also keep in mind compression in the engine affects efficiency of fuel energy turning into enthalpy. Compression and pressure ratio and what not. It also means less air flow rate is going thru combustion chamber. So de-icing by means of compressor bleed does indeed affect power and thrust. We only need to look at West Caribbean 708 to see the effect of this. Anti ice, thrust/power, and altitude weight coffin corner curves. Although the DC-9 and MD-80 series aircraft does tend to have a limitation, I noticed, on loading/weight and altitude. Due to thrust drag curves etc. etc. Throw in some anti ice and that imposes more limitations. Theres also friction with air and surfaces, which adds heat to a small degree and increases temperature slightly at high subsonic speeds. But that's probably quite small. But remember West Carribean Airways 708. 
Pic from youtube However, the compressor bleed air, within the piping/lines, has enough space to spread out. Dissipate through the piping and aircraft structure. Even if something were outright blocking the piping. Would there really be enough pressure in the piping to cause an explosion so strong that the whole structure would give way ? Perhaps these incidents had more to do with insecure fastening. But with all the number of bolts around the structure holding it ? Who the hell knows. Now as you know. Theres a high number of small bolts going all the way around the structure of a round "thing" that holds one part to another. 
Pic from aviationstackexchange.com So, an engine nacelle. There's an inlet part and a main body module. There's a large number of small bolts going all the way around fastening that inlet cowl to the main body. Arite so why would this give way when there's so many bolts ? Hmmmmmm thats a good question. The level of redundancy is not in question. There's probably at least 40 bolts or more going around the perimeter or circumference (loosely (not loose bolt) speaking, its not the absolute edge of the circle or close to circle) of the assembly between inlet part and main nacelle body. For lack of better terms. 
An example of a modular or flange section. Not fan case. From RR Avon engine ? Lots of bolts around perimeter. jetartaviationshop.uk.co From examining photos of Southwest 3472. This happened on Aug. 27, 2016. A 737-700 with CFM-56-7 (probably -7B) engines. The plane landed safely with no injuries or fatalities. Probably just a whole bunch of scared but grateful passengers, although inconvenienced by having to take another flight and being delayed. Well the whole assembly with the inner part of the duct is ripped out in an irregular fashion. So clearly this wasn't a clean separation of the inlet and main body of the nacelle. After all, why would it be with all those bolts around ? It was a violent, high pressure perhaps or some other really high force perhaps. Or just plain out metal fatigue. But does metal fatigue really cause a whole circular assembly to come right off ? There must have been some high explosive force that caused this to happen. Again, the irregular pattern of the way it ripped of the inner cowl with irregular shape on the inner cowl. This must have been some sort of an explosion. But where did this pressure come from ? OK so one of the fan blades was partially severed. Meaning the outer portion of the blade went off but the root portion remained in the fan disc. This is still under investigation as far as I can see at this time. Sept. 2018 I said this. The report could come out tomorrow for all we know. What I found so far seems to indicate that the blade separation shows signs of metal fatigue crack growth. Verify. 
Pic from airgways.wordpress.com Now. This is a bit of an odd situation. You have a fan blade separation and a separation of pretty much the whole inlet part of the nacelle. Pretty much the whole outer inlet part. And a piece of the 'inner' part was irregularly separated. So this 'inner' part might actually be the part of the engine, which is the engine casing for the fan duct, not the nacelle duct. If that makes any sense. Look at the photo and see the 'brass' part. Its irregularly ripped out. OK so what is the world can cause this ? Its mind boggling when you really think about it. A portion of a blade, a whole inlet part of a nacelle, and a portion of the fan casing. How ? If the blade separation shows signs of metal fatigue crack, does that really explain why the whole front assembly structurally failed ? This was an uncontained engine failure. There was a hole in the fuselage but the portion of the blade was not found. Verify. The blade mite have (probably) penetrated the fuselage, or partially penetrated the fuselage, vibrated loose (with the relative wind contributing), and the relative wind carried it away. The side of the fuselage and the side of the engine, the pilot's left, matched. Verify. And yes it did cause loss of preesure and oxygen masks to deploy. And emergency descent. This must have been a violent explosion of some sort. Not just the fan blade going loose. 
Pic from commons.wikimedia.org. Delta Airlines flight 1288 Consider the following. Delta Airlines flight 1288. It was an MD-88 with JT8D-219s.t The most likely cause was a compressor rotor structural failure. Which was said to be likely a manufacturing/metallurgy defect. That was failed to be detected by the maintenance crew's inability to detect the problem, with florescent penetrant inspection. Now don't get me wrong, I'm not passing my judgement. They are doing their job trying to make a living, just like myself, I plan to get into that field of aircraft maintenance. But I guess its just a reminder that you do have to go that extra mile and be vigilant and check everything. Now if you look at a picture of the aircraft just after the incident. This was an uncontained engine failure. And it did result in fatalities and injuries. As ejected sections did penetrate the fuselage. There's details of course. Conserve time. It was a mom and her son. And 2 other sons and another passenger. Verify. Condolences and sympathies of course. But there's a message to take away here. These rotating parts inside a turbine engine. Have enough rotation kinetic energy and centrifugal force. And the fact that they are sharp pieces. To penetrate not only the engine casing and nacelle, but still have energy after that to penetrate the fuselage, and cause harm there. Now in this case it looks like the whole forward section of the engine 'gave way'. The whole casing disintegrated by what looks like a catastrophic explosion. Consider also that the engines on such an aircraft are mounted aft, further back than where most passengers are located. Still it managed to kill and injure passengers. 
Pic from reddit.com. Looks like a C-17 compressor stall with reverse thrust. Now also keep in mind that a severe violent compressor stall/surge can potentially trigger a structural failure of a rotating or stationary component of the compressor assembly. Combined with metal fatigue. And a loose compressor blade giving way can throw the whole high speed rotating piece/spool out of balance. It has something to do with the working line of mass flow and the compression and what not. Its raising the pressure at the back end of the compressor assembly so the airflow can reverse abruptly if things are not kept in check. Compressor airfoils can stall just like wings if the flow conditions are disrupted. Apparently those surges combined with metal fatigue or metallurgical defects can cause something to give way. So engines have a mechanism to relieve pressure in this event. Some sort of valve that opens and reduces pressure on the higher pressure side. This being said, I can't find any cases of a compressor stall or surge causing an engine structural failure, contained or uncontained failure. 
Pic from nekropole.info.com Consider United 232. Uncontained engine failure. The fan blade penetrated the fuselage and severed 3 hydraulic lines close together. Or the fan blade hit the duct and chunks from the duct hit the fuselage and penetrated the fuselage. Horizontal stab too. Now in this case it doesn't look like the whole fan case was destroyed. Or some of it was. Not able to get a photo cuz wreckage destroyed by crash maybe. Verify. But the loose blade managed to penetrate not only the duct, but the fuselage, and all 3 hydraulic lines running closely through the same are. Or on the other hand, the blade damaged the casing and the casing fragments penetrated the fuselage and damaged the hydraulic lines. Now, tell me that's not bad luck. It could be more than that. Somebody was doing the jinx, maybe. Again, it shows you how much rotational kinetic energy is in, not a compressor, but a fan, which is the first stage of compression by the way. Remember from physics. Rotational kinetic energy = Iw^2. And I pertains to the center of mass of the blade, radius to the center of rotation. And combined with the fact that a fan blade can also be sharp. Its like a bullet. Its a small piece of dense mass moving at high speed. It will penetrate numerous parts of your body, escape your body, and still potentially do damage to something else. It has low surface area in the direction of travel, is hard so doesn't deform easily, and is moving at high speed. And kinetic energy is proportional to speed squared. So even though it has a relatively low mass. It has low surface area in its direction of travel. And high density, thus momentum. And high speed. Makes it able to penetrate a lot of stuff. And also keep in mind that aircraft skins and structure are meant to be light so as not to add too much weight, which detriments performance and economics. Problem is that these sharp, dense, rotating pieces do have manufacturing defects in metallurgy now and then. Its a business, production and time. Quality control only detects so much. The rest is up to maintenance. But in United 232, the whole duct didn't disintegrate, as far as I know. Verify. The post accident photos, I saw different things. One shows the duct still intact, 2 show the inlet blown off, from what I saw. The bottom line is that a compressor or fan rotor blade that ran away might have completely destroyed the inlet duct or might just have made a relatively clean penetration break. One must always remember the centrifugal loads that these components operate on. Rotational kinetic energy. Density and sharpness. Its been said that there's the force or weight of a locomotive acting on a single fan blade due to centrifugal, trying to tear it out of the dove tail or fir tree root or whatever the hell is holding it. Or maybe that applies to turbine blade. O well u can do the math. Mass x center gravity radius x angular speed in radians / sec. Convert RPM to rad/s. Something like that. And then centrifugal force is not the only force acting on the blade. Theres other mechanical forces. It ends up being quite a bit. Now apparently the maintenance engineer could potentially have spotted the crack in an inspection. I heard from one source that he killed himself but I didn't hear that from anywhere else. Well, I mean these defects are not always easy to spot, and it is the high up middle engine. And its not just one person's job, I suppose. But nonetheless. People maybe take it too hard on themselves. Also the pilots and crew took it hard on themselves, from what I heard. Hey, give yourself a pat on the back. You did ur best, saved more than half the people on board, and did so with an airplane that had no hydraulics. I'd be proud of myself. Other than that there were discrepancies in how the blade disc was inspected and quality-controlled. 
Pic from Confessions Of A Trolley Dolly. Consider British Airtours 28M. A portion of a combustor can managed to escape from the engine. And it ejected through the engine casing, nacelle, and into the wing structure and into the fuel tank. Now how the fuel ignited is a bit of details. But there was a big ass fire and everybody had to be evacuated. The can section must have ignited fuel in the wing or something ignited fuel in the wing. OK so this was a crack in a component that was not previously repaired properly. Heat solution treatment something like that. But the thing we have to keep in mind here is that this was not a rotating component. But it just goes to show the amount of power/energy that is involved in these engines. Also consider that this was a 737-200. Whats the implication with this ? Well, the majority of the engine is under the wing. Which means that the combustor can of the annular combustor was somewhere under the wing or at least close. So when it ejected it went rite under the wing. If u notice more recent designs. Well, even though the engine is mounted on the wing. Mainly for wing bending relief and a few other reasons like resisting a wing dropping in a stall. The engine is mounted pretty much all or mostly ahead of the wing. Despite being possibly larger, in the case of a larger aircraft with a larger thrust engine. Or having a higher bypass ratio, which is also the case. Get it, case. Haha. (laugh). Anyways. The engine is usually mounted in front of the engine mostly or totally, rather than underneath the engine mostly. And there's a reason for this. Other than aerodynamic and aeroelastic reasons. If a component were to escape. Its less likely to get into the wing. Which is important for 3 reasons. 1. Theres fuel in there. 2. It could interfere with the wing structure. i.e. framework, ribs, stringers, spars, etc. etc. 3. It could cause a hydraulic or fuel line, or electrical wire in the wing to rupture. Other reasons perhaps, of course. So despite engines being larger and heavier nowadays. Especially with higher bypass ratios and therefore bigger fan sizes. Geared turbofans too. Well, mounting in front of the wing does give better ground clearance and allows shorter landing gear. But does require extra efforts for the engineers (design engineers not maintenance). Particularly on the 737 MAX. Which is a whole different story now. But it also means a loose fan blade or compressor or turbine blade, that doesn't get contained, along with engine casing fragments, can also hit the fuselage and injure a passenger. 
Pic from pressreader.com / The Philipine Star Now consider Air France flight 66. Which happened around this time in 2017, Sept 30. I am writing this sentence in Oct. 2018. This plane had to make an emergency landing in Goose Bay Airport. Although the aircraft was more than capable of flying on 3/4 of it engines. Keep in mind that Air France doesn't have the best safety record in general. But not to pass judgement, I could make these mistakes on my job. This is very similar to Southwest 3472. In that the front part or the inlet cowl seemed to separate from the rest of the engine. And it looked very much similar to the way the Southwest looked. After all, the similar part separated in an at least somewhat similar way. Whether a fan blade detached, not sure. Now if u recall the Rolls Royce Trent 900 engine failure on Quantas flight 32. This was the other engine option, I think the only other option. But that happened at the back end (turbine area) of the engine so won't get into that too much. But nonetheless it was an uncontained engine failure and shows how much pressures that these engines do operate under. OK well lets make a long story short. An ayle stub pipe that's supposed to feed ayle to lubricate some sort of bearing to the intermediate and high pressure turbine bearing. Broke due to metal fatigue. Due to faulty manufacturing apparently. Not sure why a friggin ayle line that's not under repetitive stresses (as far as I know) would get metal fatigue. But that's more or less what it said, so I won't argue. The Rolls Royce Trent has 3 shafts or spools or whatever. There's one stage of turbine for the IP shaft that drives an 8 stage IP compressor. Verify, something like that. Probably a development of the RB 211. Anyways. This ruptured ayle line leaked ayle, which I guess got into the combustion hot gasses. caught fire. Which caused a turbine disc to give way and fly apart. Something along those lines (get it, lines, ha ha, laugh), I might have a few details mixed up, U can always verify. I also don't understand why an ayle fire in the middle of an area right after combustion, which is probably hotter than the melting temperature of the turbine material (the turbine cooling air bled from the compressor and ceramic coating or whatever prevents the turbine from melting), at high power settings, to begin with, would cause a turbine disc to disintegrate. An ayle fire in my understanding doesn't burn nearly as hot as the temperature of combustion products,and if anything would cause cooling. But hey, that's what the report more or less says, so again I won't argue. At the end of the day they did the investigation and I didn't. They have a Phd in jet engines and I don't. And one more relevant point I will throw in regarding Quantas 32. A modern commercial airliner is basically a computer with wings on it. So when an engine gives way in an uncontained way. And high speed fragments damage the aircraft. Well, its not just hydraulic systems that can get damaged. Electrical and electronics and crucial wires can get severed. And that's exactly what happened here. Which made it even more difficult to fly the plane. The outcome was very good considering what the flight crew was really up against. Safe landing, no injuries or fatalities. But a whole lot of people that probably had a heart attack and crapped their pants, I would of. Looks like Quantas Airlines still doesn't have a fatality but apparently they did. U can look that up. And they did have incidents. But whether its their fault or not. That is a matter too. Looks like this Air France flight 66 is still under investigation. But it looks like a part of the fan or fan hub did give way which must have hit the intake or duct and caused that to give way too. It was an Engine Alliance GP7000 engine. Right outboard. 
British Airways 2276. Taking off from Vegas. It was a 777-200ER. GE90-85 or 85B engine. Which is an earlier variant of the even higher thrust GE-90 -110s and 115s 115B that are floating around today with the exotic curvature on the blades. So this happened in Sept. 8, 015. Around 4pm, local time I think. The aircraft began its takeoff roll. Something must have went bang, indicating something catastrophic, and then a fire. When it reached a speed of roughly 90 mph the decision was made to abort the takeoff. The pilots used the brakes to bring the plane to a stop. Which would make sense since you don't want to apply reverse thrust if the engines have a problem. And you probably don't have time to try to figure out which engine it is, to apply reverse on the good engine. And there might be problems with the hydraulics on the wing, so forget the spoilers. Just hit the brakes. And get everyone off ASAP. After everyone reaches to grab their luggage, on the way out, of course. So ASAPAGL. Which one of the pilots criticized actually. Which is actually a common thing/problem in accidents. Although to some extent I would kinda want to salvage my stuff too, won't lie. Do they mention that in the safety briefing ? Different story for different day. So I did a write up on this a while ago, before an official report came out. OK so the report that was released said something to the effect of there was a metal fatigue crack in the 8th stage disk or disk web high pressure. 
Pic from Wikipedia And one more from a while ago. National Airlines Flight 27. Not to be confused with National Airlines flight 102, it looks like those are different National Airlines. So this was also similar to this Southwest incident. It was a DC-10-10. An uncontained engine failure in the #3 starboard engine. Not sure exactly which side that is, i.e. pilot's right, etc. etc. After the fan assembly gave way. Fragments penetrated the fuselage breaking a window. Fragments also damaged the wing and other parts of plane like nacelles of other engines. One passenger was killed. He was sucked out out the broken window and area around fuselage window which was broken. Passengers tried to pull him in or prevent him from getting pulled out and failed. The cabin depressurized, of course. And their was damage to electrical and hydraulics. The plane landed safely and everyone else survived, although there were injuries. So you can see the similarities. 
Pic from Sam Chui Agent Jay Z (not to be confused with Jay Z the rapper) did a video about interstage turbine seals. However, I think the incident he was referring to was a fairly recent one. Oct. 20,2019. TG970. A Thai Airlines 777-300ER was attempting takeoff from Bangkok when something went bang. BANGkok. (laugh) From the back end of the engine. A GE-90-115B. B for big. Looks like they were able to abort the takeoff and get back to the terminal. Nobody died I know that much. Looks like it happened recently so there's not a whole lot of documentation. But there was an airworthiness directive issued by the FAA shortly after, about interstage turbine seals. Well, an investigation report wasn't released yet to my knowledge. But from watching Agent Jay Z's video and my knowledge of turbine engines. And the FAA's AD about interstage turbine seals. Its looks like. Well, modern commercial turbofans use the technique of showering the turbine. Meaning to take some of the compressor air and direct it somehow through the shaft I'm guessing. Not sure the exact details of how this is done. Ask Agent Jay Z. And Aircraft Powerplants by Thomas Wild and another guy. The some compressor air out, not to be confused with bleed air, run it through the shaft to the turbine disc well maybe not the disc. But somehow it gets directed into the turbine blades of the high pressure turbine blades where the temperatures are the hottest. So by doing that it allows the turbines to operate in an 'environment' well above the titanium alloy's melting temperature, or whatever the turbine blade is made out of. Ceramic coated, nickel steel alloy etc. etc. Since its being cooled from within. By running the temperature of the combustion gasses going into the turbine to be hotter, it allows for higher thermodynamic efficiency and more power from a smaller lighter engine. Fair enough. We push the limits of efficiency and economics and performance. But when something goes wrong with that crucial cooling airflow. Things can go wrong really fast. The power on taxi was moderate compared to takeoff which is one of the most demanding times on the engine. So when the engine powered up / spooled up for takeoff, thats when things started to go wrong. The interstage turbine seal was somehow part of the process of keeping this cooling air going through the turbine blades. If that gets messed up trouble starts. But I don't know all the details, and I don't know what really happened. It looks like some of the damage and fragments went towards the fuselage. There were not too many passengers on board, that helps. Luck was on the their side on this one, could have been much worse. 
Pic from Its About Airplanes / Its About Travelling. Similar or maybe even same aircraft involved in below paragraph. Air Canada. ACA 101. May 28, 2012. A few months before the world was supposed to end. It was a 777-300ER or 777-333ER don't know how these designations work. It took off from Toronto (where I'm from) Pearson (where I once worked) heading to Japan (where I have never been). OK so shortly after takeoff at just under 1600 ft. AGL. There was a contained engine failure in the number 2 engine. Not sure which side that is. Now lets just get a bit of terminology straight. An engine failure is simply the engine deciding it doesn't want to work anymore. For some mechanical issue, or perhaps electronics issue from within the engine like a sensor perhaps. And not due to fuel exhaustion or a problem with the fuel system outside of the engine, in my definition, because that's not a problem with the engine itself. If that makes any sense. A contained engine failure is when there is some sort of structural failure of parts in the engine, but it either stays in the engine, comes out through the front end or the back end of the engine, without really taking too much of a chunk out, in my definition. And an uncontained engine failure is when there is a structural failure of a part, usually a rotating part, in which something punctured the engine, sideways, and broke through the engine casing. Which can happen because the rotation kinetic energy in some of these parts is too much to contain, without some heavy engine construction. And too much weight is not good for an aircraft. Anyways. This was a contained engine failure because nothing went sideways and through the engine casing. It came out the back end. And space junk dropped on to a few cars in parking lot. Yes really. i.e. pieces from the turbine. Not sure how those car owners dealt with that but I think I remember hearing that some cars were damaged. Which is not surprising if there are heavy engine chunks of metal falling from high up. The crew secured the failed engine. Don't think they pulled the fire handle, no need. Flew the plane on one engine, as it was designed to be able to do. Dumped fuel, to reduce weight for landing, at altitude of 7000 feet, and not under 6000 feet and not over a school, unlike Delta airlines flight 89. Just kidding. Get it kidding (school yard). I'm not going to pass my judgement on that matter or get into that here, at least they landed safe in a tough situation. There's lots of stuff a pilot has to deal with, driving a big plane, and I'm not a pilot (not yet), so I won't judge. Get into that business in a later post. Anyways ACA 101 landed safe, no injuries etc. etc. The crew did a good job of a textbook way to deal with an engine catastrophic failure scenario, I know I could have phrased that better. Airborne for approx. 1 hr 26 min. Apparently with the 767, 777, and maybe 787 aircraft you can land overweight. You just got to do an overweight landing inspection afterwards. According to the blancolirio channel with Juan Brown. So that kinda applies to both the ACA 101 and Delta 89 incident. But in both cases the crew chose to dump fuel to be on the safe side. Anyways. Well this incident, ACA 101, just to make sure we don't get mixed up, was a parts structural failure at the back end, the turbine area. This post is more about front end stuff. But anyways. What caused this accident ? I didn't fully understand it myself. OK so it was a GE-90-115B. Which has the highest rated thrust for a production turbofan engine, or at least did at the time. The most powerful engine ? Maybe maybe not. Thrust and power are related, but they are different things. Anyways. It had something to do with cooling holes in the high pressure turbine shroud. The inlet to the high pressure turbine, which is just shortly downstream of the combustor, is one of the hottest places in the engine. There are cooling holes drilled in the HPT shroud. I think the shroud is the duct or ring that surrounds the turbine. I'm sure how this works. So these holes are laser drilled in manufacturing. So apparently during the manufacture of this particular engine, and some others. The manufacturing process was changed to a higher intensity laser. Well of course that is likely to change the fine details of the hole that is drilled. i.e. bore diameter, how the bore diameter goes all the way thru, shape and size of the holes. So cooling of the turbine is a sensitive matter it looks like. The turbines are operating at high temperatures higher than their melting temperature etc. etc. And with lots of mechanical loads, centrifugal loads, thrust loads, bending, torgue, etc. Its designed to make a lot of power for its size and weight, and to be efficient, pushing the limits of things. etc. etc. So these cooling measures are important. The engine is sensitive to things not being precise when it comes to the mechanisms that are supposed to keep the turbines cool. I didn't even know there were cooling holes in the shroud, or how that works. And that's why with the Thai airlines incident TG970, at least what is suspected of what happened there's no official report yet. If what is said is true. The interstage turbine seal had a problem. Then it shows once again that cooling the turbines is critical in these modern engines. And sensitive. If the measures that are in place to keep the turbines cool are not precisely in place, things can start to go bad very quickly, like Agent Jay Z said. So apparently in ACA 101. These cooling holes which have had their manufacturing process changed. I guess the hole was somewhat bigger and it was different. Eroded over time in the high heat environment. Went undetected. Should have been borescoped but I guess it was suspected or required. Verify. Which caused something to do with a hot spot. Fuel rich mixture entering a place where it shouldn't be. And causing heat damage to the turbine stators or nozzles, shroud, turbine rotor disc or blades, or hangers and support structures. Like I say I didn't understand it. Initial stress between shroud 31 and 33. If you can figure this out and explain it that would be great. Anyways, GE did their teardown and inspection and determined these things. Apparently Air France also had a part in the investigation. Air Canada has taken measures to prevent this. Such as more inspections and paring the engines with the newer manufacture with the older ones on the same plane. And taking engines with eroded shrouds out of service. The FAA also issued ADs for inspections and what not. Good thing this didn't happen over the ocean, at least it was able to easily turn back. Instead of having to go ETOPS. The Pacific ocean ain't small, and I think that's the way they were taking. 
Pic from Wikipedia OK so looks like an official NTSB accident report actually did make its way some time in November or December of 2019, for Southwest 1380. I took so long to finish this post that the investigation was completed in that time, and then some. Which is actually good in a way cuz I can stop speculating and put down some hard facts. OK so lets make a long story somewhat short. And verify yourself in case I don't quite have all the details in order, or in case you care. CFM-56-7B engine made by you guessed it, CFM. Which is a consortium or collaboration or partnership with GE aviation of the U.S. and Snecma/Safran/Safran Engines of France. Snecma was turned into or acquired by or merged into Safran or Safran engines in like 05 or 16 depending on how you look at it. OK so the fan, or first stage compressor, or big thing that spins at the front. There should be 22 fan blades in this variant of this type of engine. And they are attached with a dovetail fitting. Which was apparently a fairly new thing when this engine was introduced. Which allows an individual fan blade to be removed for replacing or repairing without having to take out the whole fan. Now apparently the dovetail fitting has some sort of play for certain reasons, vibration or centrifuge gap fitting or something like that. And they actually have to be lubricated. Which they apparently were at the required intervals. So the airline mechanics did something right. Fair enough. OK so the number 13 blade is the culprit or the smoking gun. It detached/separated in flight. As the plane was climbing thru flight level 320. Which means 32000 ft. with reference to sea level standard pressure 29.92 inches Hg but not necessarily the plane's altitude above sea level. 32000 ft. is a typical cruise altitude, so the plane must have been getting closer to its cruise altitude. But the engines were probably at a fairly high power setting if it was still climbing. Which is significant. Because climbing involves more power, higher rpms, more thrust, blade twisting, and centrifugal loads etc. etc. which makes it more likely for a component with a weakness to give way. Not to say it couldn't have given way in cruise, but probably more likely in climb. Also cold air, brittleness factors (such as in Kegworth air disaster, the Titanic, etc.). OK but I'm adding my own speculations on top of investigation material here. Anyways. It looks like this blade hit the inlet cowl of the engine so hard it somehow caused the whole section to detach from the rest of the engine and nacelle. Thats a pretty good smack. But it didn't stop there. Some fragments from the broken cowl hit the wings and fuselage. OK so those fragments knocked out a window and probably punctured other parts of the fuselage. Causing a decompression or depressurization (I think they mean the same thing), of course. A rapid depressurization, the report said. So not an explosive decompression, I presume. Depends on rate of pressure loss. It doesn't stop there. Somehow the fragments, forces, impacts, damage in fuselage caused a passenger to be killed. Due to her injuries. Her name was Jennifer Riordan. Age 43. From New Mexico. Apparently she was a well liked person that did a lot of work in her community. Big turn out at funeral. Well, I don't know all the details of her life, but this seems like it might be a case of something bad that happened to a good person, which seems to happen all too often. Well she did work for Wells Fargo, but that's a different story. We won't go into bad talk here, keep the respect due. R.I.P. And at least may her inadvertent passing make aviation safer in the future. 8 other passengers or occupants got minor injuries as a result of the fragments hitting the fuselage/cabin. OK so it looks like the blade separation was caused by some sort of fatigue crack. Which was originally suspected so no surprise there. It was a low cycle fatigue crack, which means the crack started to happen well before it was supposed to happen. I.e. designed, tested, to last a certain time and cycles before crack. The separation happened at or near the root of the blade. The dovetail fitting remained intact. The crack started or propagated at the convex side of the blade. Near the leading edge. The convex side is more or less the front side of the blade. Convex, curve points outward. The leading edge is on the side pointing to the direction the blade is rotating. Like I said, these blades are under a large amount of loads, centrifugal, thrust, thrust bending, twisting, etc. etc. So if there is some sort of defect in the metallurgy, it will eventually show up. Either in inspection or in the real world, such as this accident. Apparently this engine was maintained, lubricated, inspected and what not. So the maintenance guys and the airline was doing their job in this regard. But shit happens. Manufacturing isn't always perfect either. Inspections on fan blades should be NDT methods. Verify. Visual, eddy current, ultrasonic, fluorescent dye penetrant etc. etc. So apparently some service bulletins came out right after accident saying that the fan blades needed to be inspected for cracks a bit more often. OK so low cycle fatigue might not quite be what I thought it was. I thought it was simply the part failing before it reached the number of cycles it was designed to last. Apparently it has something to do with plastic deformation. Which to make a long story short has something to do with a stress, whether tension, compression, torsion, shear, etc. etc. applied goes beyond the region of elastic deformation of the material so the object doesn't return to original shape after load taken away. It gets permanently deformed. Something like that. So I'm guessing that this fan blade somehow experienced much more load than it was supposed to take somewhere along its operation. Maybe the fan sustained higher than normal RPMs for long time. Or a metallurgical or manufacturing defect. Which caused stresses to be concentrated in one spot. Or perhaps low temperatures at higher altitudes led to some sort of thermal cycle stresses. Hail ingestion, rain, corrosion, bird strikes. Who knows. Shit happens. Inspect parts regularly. Manufacture parts to high quality standards and don't cut corners. etc. etc. etc. The other issue here was that the fan case was supposed to contain the broken blade piece flying off. Isn't that a certification requirement for modern commercial (or otherwise) turbofan engines ? The whole front part of the nacelle just ripped right off. Which is kinda strange. I would think a dislodged blade, striking the fan case really hard. Would penetrate the case in one spot or cause a crack or break in one spot. If that makes sense. But instead, it caused the whole front section to rip off. But I guess the vibration from the engine running on an unbalanced fan disc plays a part too. But still. It doesn't really make sense why the whole thing comes apart. O well. It is what it is. But its not the first time. But it seems like its the first time on a fairly modern engine, if I'm not mistaken. The report did mention that the broken fan blade hit a weak spot in the fan casing. So that needs to be looked at. The design of the fan case. But hey, look what happened with the Air France 66. That was also a modern engine type. Engine Alliance GP7000. There's video released of the Trent 900 engine test successfully containing the blade. I'm sure the GP7000 had to pass similar tests. But it still managed to happen. So that kinda depends on luck. And where the blade hits the case. Its not completely fool proof that the fan case will contain it no matter where it hits, I guess. The test for fan blade containment when the engine was certified might have indeed been a pass. But. In the real world. The fan blade can hit the case anywhere within some sort of predictable zone. But it might not have hit the case in the same spot it did when it was tested. And I don't think we have time and money to test blade containment everywhere. That would be a shit load of testing. To make the fan case/duct completely fool proof would really require some more design work, and perhaps to beef up the structure even more, which means more weight. So other than that good job to the flight crew for their handling of the situation. Ms. Shultz who was a Navy pilot. That military pilot experience probably came in handy that day. Also co-pilot/FO Mr. Ellisor who was an Air Force pilot, so also military pilot experience. Flight attendants, and the passengers also did a good job of handling the situation and trying to save the wounded passenger. Ms. Shultz wrote a book about it. One day I'll check that out. It looks like this accident was similar to Southwest 3472 just under 2 years before. Partial fan blade separation, engine duct gave way. Same airline, same or similar aircraft, same or similar engine. In both cases the plane landed OK. But in this case one person didn't make it, the damage was more severe overall I think, and the flight dynamics involved were a bit more messy. OK so the moral of the story. Not all engines are metallurgically perfect. Even though they cost a pound and a crown. Which you don't pay for directly (unless the government subsides airline), unless ur a passenger which u pay indirectly. Furthermore. In the race to keep up with the increasing demand for air travel, it looks like there are more errors in the whole process by which air travel is carried out. From manufacturing to piloting and even ATC. Newer aircraft are being pushed into service. Aircraft are being rushed into production to keep up with schedules, particularly newer aircraft. The demand is for modern fuel efficient aircraft. Don't get me wrong. I can make these mistakes too. Whether it be I'm a pilot, ATC, Im working at GE, I'm a quality control inspector, I'm an FAA certification dude, or I'm an AME/A&P/aircraft technician apprentice. We just got to all do our best to do our jobs the best we can and detect flaws. And we got to do liquid penetrant dye NDT, phlorescent inspection on engine components as well as visual inspection. U never know what u find. A technician involved in United 232 supposedly killed himself for not spotting the crack in the fan blade. Verify. Not sure if that's true. Well, its a tough pill to swallow. But its not always entirely your fault. But we got to be extra vigilant. Especially now that aviation is as big as it is. More cycles = more wear and more stress. And newer aircraft pushed into production. Also means we got to watch out. You also got to keep in mind that aviation industry sectors are short staffed nowadays. Pilots, maintenance, even ramp guys like me. So that causes people to be overworked and have less time to look at these fine details. For now I'm just a dude that loads baggage at Swissport. But we still got to keep an eye. The A380 incident is still being investigated. Now these more modern airliner's engines are supposed to be able to contain stuff right ? U seen the videos where they detach an engine fan blade in testing ? Hmmmm. Also consider National Airlines flight 27, which involved a DC-10. Similar to Southwest 1380. Uncontained engine failure, cabin damage, passenger sucked out. When shit hits the fan, or when the fan hits something and shit happens. Well, we can reduce risk by beefing up engine structure as much as practical within weight limits. Keeping fluid lines separated and in areas less likely to be hit by uncontained blades. Which was not the case (get it case) in United 232 due to practical constraints. Frequent and regular inspections of blades and discs are important. Since the amount of rotational energy is difficult to contain, without making a tank of a structure, which has a huge weight penalty. If cracks are detected in the first place we can prevent it. But some of these components don't last as long as they were expected to. So we gotta do a bit more frequent inspections. Visual and NDT methods. 
Pic from insights.globalspec.com. Southwest 1380 investigation 
Pic from Medium.com 
Pic from Medium.com Southwest 1380 investigation Sources Avaiation Stack Exchange - Nacelles and Cowlings Aviation Stack Exchange - Why do uncontained engine failures still happen, 5 Incidents Wikipedia - Air France 66, Southwest 3472, British Airtours, National Airlines, Southwest 1380, Quantas 32, Rolls Royce Trent engineering.com - Southwest 1380 Uncontained Wikipedia - Safran Engines CMF International Website NTSB - Southwest 1380 Flying Magazine Online - NTSB report Southwest 1380 CBS News, Southwest 1380, Jennifer Science Direct and Wikipedia - Low Cycle Fatigue CBS Evening News - New Details Southwest Flight News In Flight - Thai 777-300 Uncontained Aviation Safety Network - FAA Emergency AD GE-90 777-300ER Air Maintenance Update Magazine - Raising The Bar, February - March 2017 Algeria Plane Crash 
Pic from dailysabah.com Ya it seems pretty negative. I only seem to be putting up stuff about crashes, incidents, injuries, loss of life, disappearances, bad stuff, etc. etc. But hey, time is limited and bad stuff keeps happening. So I got to keep up, even if I'm somewhat (to put it mildly) lagging. And the 737 MAX, when will I get around to that ? By the time they fix it and put it back in service ? By the time people trust it again ? Anyways. 
Pic from baaa-acro.com So this one I couldn't find a flight number, but it wasn't a civilian airline flight, so maybe that's why. It was Wednesday April 11 2018, just before 8 am. Taking off from Boufarik Airport. Which is near the north coast of Algeria by the Mediterranean Sea. Also close to Algiers, the capital. Not sure where it was headed. It looks like it crashed in a field shortly after takeoff. Witnesses seem to see flames shooting out from one engine. The plane lurching, which I guess means a jerking motion, when the plane reached about 1000 ft, AGL I would imagine, and the plane hitting the ground on one wing first. 
Pic from aviation24.be. IL-76 similar to this one. Maybe same one. So 257 people on board we killed. All occupants ? So apparently this was the worst air accident in Algeria history, in terms of fatalities. Safety record in Algeria ? 
Pic from Air Live Not too much info seems to be available right now. The fact that there was flames shooting out of one engine may be an indication of a compressor stall. Perhaps the lurch could have been caused by a sudden asymmetrical thrust due to a failed, shut down, cut off/flamed out, or stalled engine. Nonetheless an engine out in a 4 engine aircraft like that should not have caused such a catastrophic loss of control, unless the flight crew really didn't handle it right. But still, unless they made some sort of serious mistake, i.e. pressing the rudder to the wrong side or shutting down the wrong engine. The latter which has happened in the past. And failure to use rudder in one case, China Airlines 006. But other than that, I can't see one engine failing causing that whole plane to go down. Perhaps an aerodynamic stall followed some sort of mechanical failure. Which would indicate a possibility that the crew didn't handle it properly, since a stall can be avoided if an engine is lost, or other malfunction. Perhaps something similar to American Airlines 191, where a slat didn't stay extended causing loss of lift on one side. Hey, this Algeria crash seemed to show the plane on its side, or at least the aft section. Ahh, these are all speculations. We will see when the investigation report pops up. And looking at the aircraft, at least on visual inspection, the engines seem spaced fairly close together, and more inboard, compared to other similar modern large turbofan airliners. Which tends to reduce asymmetric effects. Look at a pic of other 4 engine airliners like the A380, 747, A340, IL-96, 707, and DC-8 and the difference in engine spacing and how far outboard can be seen. Which all has to do with engine and wing aerodynamics, mass flow, speed conditions etc. etc. different story for different day. The point here being that an engine out situation mite cause less of a challenge to keep the plane flying compared to other similar size transport aircraft where the engines are more spaced out. 
Pic from Wikipedia 
Pic from youtube Sources Wikipedia - IL-76 crashes and Boufarik Airport. CNN.com - Algerain Kills 257
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