How are Jet-engines attached to the wings?!

hi everybody very welcome to mentor and yet not a video podcast as always I hope you're doing absolutely fantastic today on the video we're gonna be talking about jet engines specifically how they are fitted onto the wings and why those fittings are actually not as strong as the rest of the structure we're also going to be answering a viewer question about why we don't have the engines incorporated into the wings anymore so stay tuned this video is brought to you in cooperation with brilliant now if you are like me you've been spending the last few weeks trying desperately to come up with good ideas on how to improve yourself with all this extra time that you have in that case I highly recommend you to check out brilliant they have more than 60 different courses in areas like for example problem solving like brain puzzles and mathematical fundamentals and physics and how to you can build your own algorithm the way that they do this is they enter you in on a fairly easy level and then they give you tools for each step to get more and more advanced until you sit there and you solve problems that you never thought you were able to do now those of you are interested in checking this out you can use this link here below which is brilliant dot org slash mentor pilot and that will give you 20% of the annual fee of brilliant but remember you have to be quick it's only the first 1000 people that use this link that will get the discount so check it out [Music] all right my friends so engines how they are fitted to the aircraft why they look like they do why they're fitted where they are I could spend hours talking to you about technical bits of this and in fact I have already made a video about the placement of the engine so if you're interested in that I'm gonna link to it up here you can check out that video after this but the first thing I want to talk about is a question that I got in from one of my patreon so actually and he was wondering why did we stop to incorporate the engines into the wings looks really cool when you do doesn't it now there are several good reasons why this happened and I'm guessing that you guys can probably think of a few but the main ones were if you look back at the first ever kind of purposely built jet passenger aircraft which was the de Havilland comet it had the jet engines incorporated into the wings and it looked really really sleek but the problem what the problems are many so for example if you want the engines to be inside of the wing you need to create a box for those engines to be inside which has to be really really strong and it also has to be giving a little bit of margin so that if you have an engine fire for example it won't be that dangerous to dress of the wing structure that's complicated also if you are going to build that box inside of the of the wing it means that that part of the wing cannot be used for fuel and if you think about it largest amount of fuel that we have on jet aircraft is going to be in kind of the center of the wing close to the body where the wing is thickest so effectively by putting the engines inside there instead you will be reducing the overall range of the aircraft now on top of that you have things like for example accessing the engine for maintenance would be a pain and also as you've seen lately the bigger you build the engines the more efficient they become the more by poverty or they get and that's not really a problem if you're using an engine that is more or less pure turbojet engine but if you want the turbofan engine you can't have it inside of so that's the reason for that but I'm really glad that you guys are sending these questions in now what I want to focus on on this video is how the jet engines are actually held onto the pylons and why that connection is not as strong as the rest of the aircraft structure when I'm finished with this video towards the end we're going to be looking at two different case studies where failure to this system in one way or another led to an accident and why that happened but first of all the engines jet engines the public jet engines as we call them now which are hanging under the wings they are connected to the wing with something called a pylon pylon is a very strong structure it is bolted onto the forward wing spar normally and to watch the back of the wing and that part of the of the engine assembly is very very strong okay the reason that you need the pylon in the first place is because you don't want the actual engine to be so close to the wing for the same reasons that we talked about when it came to having the engines inside of the wing you need to have a bit of distance between the engine and the wing in case there will be an uncontained engine failure or an engine fire to protect the wing structure and the fuel inside right so you want to build a little bit of a distance in between also the fact that the engines are hanging down and a little bit forward is good from a structural point of view for the wings not they're out there hanging means that it stops the wing from bending too much and also the fact that it's a little bit in front of the wing stops some of the torque of the wings from happening so there are structural reasons for this when the engines are done connected to the the pylons it is connected at least on the 737 in two different fittings they're called hanger fittings and you have one that is bolted on to the fan casing of the engine and the second one that is bolted on to the turbine section of the the engine and in between those two fittings you have something called a trust link and that trust link is there in order to to transfer some of the trust for from the forward fitting that normally takes up most of that force onto the back fitting so it equals out the forces so what forces are we talking about this might be interesting all right there are two main forces but basically three that these fittings have to take up you have the trust which is the by far the biggest force that's the thrust of the engine is actually you know producing when we put maximum take of trust on and that's 177 about a hundred kilo Newtons right so you have to have a fitting that takes that up and then you have the weight okay the weight of a 737 engine is about two tons so 2,000 kilos that means 20 kilo Newtons but of course that's not all of the weight that you have to take into account you also have to imagine that at some point the pilots might be doing our hard landing for example so there is a little bit of G loading onto that let's say that you get about 3 G's or worst case scenario 5 G's okay if you get a 5 g landing and you have 20 kilonewtons of weight means another 100 kilo Newtons so that's a hundred kilo Newtons forward and maybe a hundred kilo Newtons down and then you have a little bit of torque on the the engine as well for different reasons because of movements of the engines because the movements of the fan things like that which is smaller than those two forces so what kind of forces can these fittings actually take them now I've already told you that it's less than the overall structure of the aircraft but the fittings are held in place by four bolts in the forward fitting and four bolts in the back so eight bolts in total and in the forward hangar fitting you have two shear pins those are basically pins that are sitting in hold that takes up some of the the trust force and you have one shear pin at the back all right that's because most of the thrust force is sitting on the forward fitting and some of it because of the trustlink is on the back fitting as well alright so these the things that are holding the engines in place now these bolts are made of special nickel alloy called England seven one eight it's a super strong alloy and this alloy has a tensile strength about hundred and eighty Newton's per square millimeter right there about twenty two millimeters thick which means that one bolt will take about 70 kilo Newton right so 70 kilo Newtons per bolt they're eight bolts that's 560 kilo Newtons and as we already talked about the the forces that the engine will normally encounter is a maximum of about 100 kilonewtons forward and 100 kilo Newtons down so the 560 gives a big margin of you know forces to behave that this engine can be able to encounter before it becomes a structural problem however 560 kilo Newtons is not that much if you look at the overall strength of the aircraft for example the amount of strength that the wings can take or some part of the body can take and there's a really really good reason for that if you think about it when we come in and land let's say that we would come in and we would have some kind of problems with our landing gear so we can't extend the landing gear or we would have an unsafe landing gear so it could potentially collapse once we got down on the ground or if something would be wrong with our calculations and we would overrun the runway well what would happen then is that it's likely that what would hit the ground first is going to be the end in the cells when the end in the cells hits the ground there's going to be much more force than 560 kilo Newtons acting on those bolts and that will fear the engines off they will fall off the wings as it impacts now it is much much better that the engine shears off then if they would be so strong that they would actually tear the wing of because if the wing would be torn off then you would have a huge fuel e coming up and even both wings are torn off in the case of for example a faulty landing gear well then you have not things stabilizing the aircraft in the right orientation and you might get the aircraft body to start the roll which could cause a lot of human damage all right so this is why you have this system it's very very closely calculated to make sure that it can take any force that the aircraft might ever you know be subjected to you know heavy turbulence severe turbulence hard landings anything like that but if it comes in contact with the ground then it will share the engines of in order to save the overall structure of the aircraft ingenious isn't it now I promise as well that we were going to talk about some case studies where the systems of pylons and bolts didn't work as expected and the most famous example of that is probably American Airlines flight 191 that took off out of Chicago O'Hare Airport in May of 1979 so what happened on that occasion was that the aircraft took off and during the later part of the take-off roll the left hand engine just completely detached from the aircraft it swung over the wing on the left hand side and while doing so it also ruptured some of the hydraulic lines as it you know roll off the wing the subsequent problem that the pilots faced was obviously did the last the lack of trust from that engine that gives a yaw moment but also because the engine had ruptured those hydraulic lines the hydraulic pressure that held the leading-edge devices on the left-hand wing out disappeared that meant that the leading edge devices retracted which meant less lift from that wing the wing actually stalled and when you have one wing stalled and not the other you will end up in an uncontrolled roll to watch the stalling wing which was what happened the aircraft crashed into a trailer park not far from the airport and 273 people died which made it one of the worst air accident ever on American soil now in subsequent investigations after that it was found that the pylon had been damaged the engine pylon had been part of an engine change that was done several weeks I think eight weeks before the accident and a procedure that that was used was found not to be according to manufacturer instructions so the engine pylon had impacted its fitting which I bent it slightly and when the engine was done refitted this wasn't recognized which led to for each takeoff and landing after this this engine change metal fatigue started building and on this this flight the metal fatigue became too much which basically shared the the engine off and cost the the engine loss now on top of that this was compounded by the construction of the dc-10 and the fact that it didn't have hydraulic fuse that could keep the leading-edge devices out in case of a loss of hydraulic pressure so there were several findings as it always is in these kind of investigations but basically it put a lot more focus on the maintenance procedure surrounding engine changes and specifically the metal fatigue part of the the pylons and the engine fitting now the second one woopsy has parted to do with with metal fatigue it was El Al flight 1862 which took off out of Amsterdam and its Boeing 747 that shortly after takeoff had a very similar thing happening where one of its end engines I think detached from the wing flew of the wing and the pilots lost control of the aircraft and it crashed into an apartment building several killing some people on the ground and the the crew members on board it was a cargo flight and on the subsequent investigation there metal fatigue - one of the shear pins on that engine was found to be the likely course of the engine actually letting also what all this all has led to is is more thorough kind of maintenance procedures and verifications of the components included in holding the engines in place so for each one of these horrible accidents there's always been a positive point coming out of the fact that we learn the industry takes huge pride in doing a thorough investigation into any incident or accident and from whatever is found to cause that accident we can learn and make sure that that doesn't happen in the future and this is what we do as an industry we always pride ourselves in trying to work to improve flight safety overall now if you have more questions about technical things why does not look like that why does it sound like that you want me to explain it then write it in below you know give the thumbs up to the video give a suggestion of what I should be doing a video about in the comments below and make sure that you have subscribed to the channel and that you've highlighted the notification well now I do quite frequent extra videos now when things have happened in the industry that needs an explanation and if you haven't highlighted the you know the notification bell then you might not get notified when I do these videos so subscribe highlight the Bell have an absolutely fantastic day and remember to check out brilliant as well if you want to improve on your math and your physics skills in a fun and interactive way brilliant is the way to go take care of yourself bye bye right guys I really hope that you like that if you want more content like that more aviation content but then check this out I hope that you have subscribed to the channel and that you've highlighted little notification valve see you inside of the mentor radiation app and have an absolutely fantastic day bye-bye you [Applause] [Music]

Channel: Mentour Pilot

Views: 191,431

Keywords: Jet engine, CFM 56, Engine mounting, mentour pilot 737 max, mentour pilot turbulence, mentour pilot reverse thrust, How to become a pilot, fear of flying, nervous flyer tips, nervous flyer turbulence, nervous flyer video, Boeing 737, Boeing 737NG, boeing 737 max, boeing 737 max 8, Aviation incident, Airbus 320, Airbus 321, airbus a380, airbus a380 take off, Airbus 350, Boeing 787, Pilot life, Best aviation youtuber, aviation facts, pilot youtuber, flight school, comet

Id: xnHeRUC4GDY

Length: 17min 9sec (1029 seconds)

Published: Fri May 22 2020