 We now start with the presentation on aircraft component nomenclature. So, today our task will be to familiarize you with some of the major components that go on the aircraft. In general, the aircraft can be divided into assemblies, sub-assemblies, parts and then you can go down to very, very small parts. But a component in the aircraft actually means something like an assembly, okay. So, I will not go into rivets and bolts and nuts, but I will go into major parts like wing, fuselage, tail, etc. So, let us see what are the components that we could cover in this presentation. So, we will of course cover the wing which is the main component. We will proceed with the fuselage of the body, empanage or the tail and then we will go to miscellaneous. Now, this miscellaneous word is a very dangerous word, okay. Miscellaneous can mean anything. So, let us define very soon what do we mean by miscellaneous. But before we start, it is important for you to understand that we follow a particular axis when we talk about aircraft. Each of the three axes moves about the center of gravity. The aircraft's principal axes are normal axes, that is the vertical axis, top to bottom, lateral axis, along the wings, parallel to the wings, and longitudinal axis, drawn from tail to nose. Each axis is perpendicular to the other two axes. Let us look at each individually. The rotation about lateral axis is called pitch. This movement changes the vertical direction of the aircraft's nose. The rotation about normal axis is called yaw. This is the movement of the nose of the aircraft from side to side. Side to side movement of the nose is called yaw. The rotation about the longitudinal axis is called roll. This is the movement of the aircraft's wings. One wing goes up, the opposite wing goes down. So, in summary, these are the three principal axes of movement. So, in this presentation and also in the entire course, we are going to use these three axes and these three pitching moments, these three moments, pitching, rolling and yawing. You have to appreciate what they are and remember this particular video. So, the first component of the aircraft that I want to touch about is the wing, which is the major component. Without wing, it is very difficult to have an aircraft. So, here is a photograph of the wing as it looks from a particular window and you can see that the wing is not just one single piece. It contains several sub-assemblies. A few of these assemblies are visible in this photograph through the window. Now, there are two edges. So, we will see which edge, we will see which parts of the wing move and which parts remain stationary and we will see if we have missed something. So, let us see. First, the wing has two edges, the leading edge and the trailing edge. So, the leading edge is the one that hits the air first. It leads. The trailing edge is the one that comes later. Okay? And if you cut the cross-section of the wing, the profile that you get is called as an airfoil. If you are in the US, it is airfoil. If you are in Europe, it is aerofoil. So, it is the same thing actually, whether it is an airfoil or an aerofoil. Once again, remember if there is something not clear, I would request you to please interrupt me. So, let us see the two wings in photographs. We have the leading edge as seen from one of the windows. Why is the leading edge? Because it is in the front. How do I know? Because I can see the engine cowling below, the engine covering below and the one on the trailing, that is the trailing edge, which is the rear portion. And on the trailing edge, there are certain things jutting out, which we will very soon learn about. Okay? Now, the wing is basically the device that produces the maximum lift and these devices are mounted or the wings are mounted on the fuselage normally and there are some flight control surfaces mounted on the wing, which help us in controlling the flight. We also have some high lift devices, which are basically meant to increase the lift. So, if you have better lift, you have better takeoff and landing performance, but there is also some other purpose of those. So, first we will look at the wing and the control surfaces on the wing. Okay? So, we look at this first. The one which is extremely outboard is the aileron. It has a specific function. Then, if you just see what the aileron is, we will see how it works. So, do you understand? Ailerons always work together, but in opposite directions. They are internally linked. So, when one aileron moves up, the other aileron moves down. The one that moves down generates more lift. The one that moves up actually pushes that wing down. So, one wing is going down because of the air acting on it. And you can also assume that the other wing is going up because of the air acting on it. So, together they create a moment which overcomes the roll inertia and turns the aircraft or rolls the aircraft in the direction that is needed. Now, if in large aircraft, we may have aileron split into many components. Usually, we have an inboard aileron and the outboard aileron. So, why do you think we need to have a breakup in the two ailerons? What could be the reason? Anyone can try to answer this question? In case of failure. In case of failure, then there is one aileron available. But in case of failure, you mean to say this is a backup? No, no, no. We do not have inboard outboard ailerons for a backup purpose. Please pass on the mic. What is the different along the length of the wing? No, my question is why do we break the aileron into two parts, inboard aileron and outboard aileron which is there on each wing. Each wing has an inboard aileron coupled to the inboard of the other side. Each wing has an outboard aileron coupled to the outboard of the other side. So, what is the reason why we break it up? Yes, there is one person here. So, what you are saying, you want to add something to that? You try to answer. What is your point of view? Large change in. Small and large changes in? In the pitching. Pitching? No. In rolling. In rolling. Okay. So, basically the division of aileron into two parts is driven by stress considerations that if I actually deflect one piece aileron on a large aircraft, the load can become very high and maybe the turn will be very sharp which may lead to inconvenience to the passengers. So, therefore, we have inboard ailerons which have a smaller moment arm. We have an outboard aileron which have a larger moment arm. When you want to have a split roll, you will deflect both of them. When you want a high speed roll, you can deflect only outboard. When you want to have a low speed board. But then at very high speeds, it may be too much to deflect outboard ailerons even by one small angle. So, you may like to deflect inboard ailerons because the moment arm, because the force is high because of high speed. So, in supersonic flight, you might turn using only the inboard ailerons because the moment arm needed is less. Sorry. The moment distance needed is less. Force is coming from the aerodynamic force itself. So, this is not in every aircraft. Only in some aircraft. Location is in the outer trailing of the aircraft. Function is roll control and the one that goes down gives you more lift. The one that goes up gives you less lift and this gives you a rolling moment. So, let us see one small clip of aileron in action and more so the effect of deflecting ailerons. Very simple video. Pilot deflects the aileron and that is the outcome of that. In this case, the pilot continues to hold the aileron. So, therefore you continue to get the moment to go more than 90 degrees and then we level up and after leveling up you are back. Okay. Alright. Let us see the next thing. Let us look at flaps. Oh, flaps are little bit complicated in some aircraft. As you see in this aircraft, there are so many of them. Okay. So, what is it? Location is the trailing edge inboard to aileron. Ailerons are always more than outside, they are the flaps. So, they are located inboard from the ailerons but there could be many, many of them. So, what is the function of flaps? These are flaps on the trailing edge. So, their function is at low speeds, I would like to provide higher lift. We will study how we get more lift by the flaps. At the moment, I am not going to really start explaining the aerodynamics behind it because that comes later. Today, your task is, oh, where is the flap? What is the purpose? That is all. How is not important right now? Where? What? Where? And some points about its usage. How it works? Let us not worry right now. Okay. Flaps basically are of two kinds. Outboard flaps, inboard flaps. Okay. This division is done normally to alleviate the load only. You will never have a situation where you will deflect maybe only outboard flap. Normally, you will deflect both of them together but the load is distributed so that we do not have any large structure with loading acting on it because the actuators which are going to deflect it, they are going to need a lot of power and that will make the aircraft heavy. Now, we have a special chapter on high lift devices where we will study the various types of flaps. Right now, I am going to just show you some pictures. Okay. This is a simple hinge flap like my wrist is a simple hinge flap. That is it. The whole thing moves down across the hinge. Okay. So, it is also called as a plane flap. The most simplest flap. Where do you see this? In the most simplest aircraft. Where, remember one thing in an aerospace, in an aircraft environment we always want to reduce three things cost, complexity, weight. We do not do more than needed complexity, cost and weight. So, here if you do not need anything more complex than plane flap go for plane flap. If plane flaps are working for you never go for anything more than the plane flap. Okay. So, typically 20% of the wing is simply hinged. It could be slightly more 25% even 30%. But 20% is typically the order. Split flaps are actually less effective. Because what we do here is only the bottom portion something comes down. The top portion remains as it is. So, you have a split. So, just the last 20% of the wing forms it. Top surface is stationary, lower surface moves. Then we have more complicated. There are many, many, many types I am skipping. I want to come straight away to one of the most complicated types. These are the fowler flaps. So, if you notice in this figure these flaps are not only moving down but they are also moving back. So, they are increasing the area also apart from the angle of deflection. Okay. These are highly sophisticated. Their mechanism is really complex. So, let us have a look at a small animation on the deflection and retraction of a fowler flap. It is only an animation but it will give you a clear picture. So, this flap is basically a single slotted fowler flap. That means there is a fowler flap and that to not one piece, there is one small piece behind which moves independently. You can have double slotted fowler flap. You can have triple slotted fowler flaps. But beyond that, the complexity becomes so large that the advantages are not so much. So, I have never seen a quadruple slotted fowler flap. Okay. So, for the Moodle, there is one small assignment for you. Find out any aircraft that has got more than three slots. Okay. I would really like to hear from you if there is some aircraft which has got quadruple or pentaslotted fowler flaps. I only know of three, maximum three and also identify one aircraft which has got a triple slotted fowler flap. And what you do is suppose we will play fastest finger first here. So, the first person who says, okay, Boeing 747, the next person to understand, yes, yes, I agree. That is not the purpose. The next person should say, this also, this also, this also. What will happen very soon will have a nice list. So, in my next presentation, next year, I will just put a table saying these are the aircraft which have got a triple slotted fowler flap. So, one requirement is anything more than three slots in the trailing edge only. Okay, I am looking at triple, more than triple slotted fowler flaps and I am looking at also aircraft which are having a triple slotted or more than three slotted fowler flaps. So, the wing also, the area also goes up, the curvature also goes up which is called as camber. We will study this in the airfoil section. That is the outcome. Unfortunately, it is very difficult to talk about a component and simply say this is the component. We invariably end up telling something about the functioning, but I am going to avoid it. Okay, slotted flaps are flaps where you create an air gap between the two moving parts or the three moving parts. This is an example of double slotted fowler flap both inboard as well as outboard. Okay, so what you do is you create a small gap and we will see later on what happens there. Right, moving on. So, other ones give you roll control. Flaps give you lift improvement. What about aileron plus flap? What will you call it? Flap around. So, we have something called as a flap around which is a aileron plus flap. So, when you want to move it like a flap, both of them move down. When you want to move like an aileron, one goes up, one goes down. So, egg to egg free. That is the offer. Okay, that is the flap around. So, here is a flap around which you can see and this is the images taken from actual flight for some aircraft. There is a small piece between the inboard flaps and the outboard flaps and it can move up and down as I will show you in one video. Okay, so let us see how this is going to help us. So, this is the video from start rolling to take off to some initial climb. Notice flap around has already started moving. It is going up because I do not want to create any deflection right now. It has come down completely. That means it is now working as a flap. Focus only on this part right now please. Now you see it starts dancing because the pilot wants to create small correcting rolling moments to take care. If you put aileron at this time maybe you can see aileron already reflected little bit. Little bit is difficult to see but he is trying to manage he or she trying to manage with just the dancing of the flapperons to get the required movement. So, now the aircraft has gone into a climb that is it. The job is over take them inside so the flaps are now being retracted. They are going to go down they are going to go up sorry and they are going to become flush. But the flapperon keeps moving because it is meant for minor corrections. So, this is the function of the flaps. They are down during takeoff and they are giving you enhanced lift. What are these? Anybody knows? Are they air brake or spoilers? They are spoilers. So, after landing you want to kill the lift you want to spoil the lift. So, what you do is you bring an obstacle in front. So, you just push this flat plate up and give higher resistance. So, it creates more drag which helps in reducing the landing distance. It kills the lift and it allows you to descend very swiftly without speed entry. Otherwise your landing distance may become very large and your impact velocity also may become very high. These are deployed on landing typically automatic as soon as landing gear touches down spoilers will go up. We rarely deploy them in the flight. It is very dangerous. Interesting thing is they are not air brakes. Air brakes are different. I will talk about air brakes also leading us devices. Now, here I also want to show you I also want to discuss with you some very interesting information. Do you observe that the engine intake has a very peculiar shape? Can you describe this particular shape? What you see? Can you describe this shape? Anyone? It is round in shape and a flat. So, you are saying it is round in shape and as a flat bottom. I would not say it is a round in shape. It is actually oval. If you look at the cross section the ring is actually oval. So, what is this part called? The one that is covering the engine is the nacelle. N-A-C-E-L-L-E is the nacelle. It is the engine nacelle. Anything that is provided for a shroud or a covering over a part which is suspended in the airstream is called as a nacelle. This is the engine nacelle. The engine nacelle is not circular. What could be the reason? Why is it not circular? Now, let me tell you one thing. I will give you the background first. It was not like this earlier. It was made like this because we want to maintain some clearance from the ground. For any component of the aircraft there is a unwritten or a written rule that you should be 18 inches away from the ground under all conditions of light. Except for something like tail skid which is going to rub on the ground unless required by function any component should never come less than 18 inches from the ground. Now, if I make this particular intake perfectly circular it will probably become less than 18 inches clearance which can be dangerous. So, this has been done to increase the clearance. But why was it not possible to go for a circular thing which can be 18 inches away? Why this horrible looking shape? Believe me, this shape is aerodynamically worse than a perfect circular intake. So, on an aircraft like this where even 1% higher drag can be a real problem and the competition can actually win over you because you have got 1% more drag. Why would a designer permit something like this? So, this is the next question for the model. What is the reason for such awkward looking nacelle shapes? Nacelle cross section in an aircraft. So, the leading edge of the aircraft also contains certain devices such as slats. So, basically a flap in the leading edge is called as a slat just a name. A similar function it goes down it has got a similar aerodynamic shape but it is called as a slat. So, this is a fixed type slat nothing moves here it is like this right from the beginning to the end this is the aircraft configuration this red colored device is fixed the grey colored wing is fixed nothing moves this is called as a fixed type slat. This is also an example of a fixed type slat where there are these members for structural rarity. This is a fixed slat there are members which support it why do we need this thing we will come back later. In some aircraft we have a retractable slat that means we have slats which can be retracted we do not have the file here but this slats can be retracted so just like the follow flap it can move back and close the gap between the two when not needed it can close the gap these are the retractable type of slats okay. So obviously the purpose of this is to make the aircraft smooth during cruise no gaps and no projecting parts in the fixed slat there will be more drag during cruise but they are simpler and then you have something called as a Kruger flap a Kruger flap is actually a very sharp curvature flap right at the leading edge see here for example this particular thing is like a flat plate which came down but it has a small curvature like this here okay let us see so see how Kruger flaps operate this is the leading edge of the aircraft so these flaps are actually going to come out and cover up so these are the flaps which actually come down like this in the leading edge so they are called as the Kruger flap all these videos are easily available on youtube so there is no problem in finding it okay have you observed these things below the wing we observed it in so many of the wings that we saw so far so what are these these contain the arms which deploy correct very right they contain the tracks along on which they house the tracks so this is also like a covering actually there are flap tracks there they will be horribly aerodynamic so you cover them with something like this so they are called as flap tracks okay or flap track fairings now they come in different shapes some of them have very pointed thing on the back some are rounded generally they are aerodynamically smooth bodies provided to reduce the drag of the flap track fairings if you do not have them it will be difficult to have flaps moving down okay they are also called as kukhman carrots in respect of kukhman who was the person who did the aerodynamic design of the concord aircraft but the purpose there is not just flap track the purpose there is to provide some savings in the drags people also call it anti shock bodies because these can be used to manipulate the shock acting under high speed flight okay and these flap tracks are the ones that house the mechanics you have already seen this okay let us put it all together now and see so this is the figure that I showed you in the beginning the figure on the bottom left which shows the working so now let see the whole thing working together again so now this is on the ground notice what happened this is testing on the ground these are the flap track fairings we will just proceed ahead I will try to show it some other time these are your air brakes okay these two on the back these are the fewer gelage on the rear opens up like this and creates intentional drag so these are load bearing members you can see there are two arms coming here which carry the load and they are going to give you the increase in the drag so I will show you a small clip of BI146 landing notice the drag on the back they open up there are no spoilers here but they use a speed brake or an air brake look at the runway it is not straight okay it is up and down why is that so because it is very difficult and very expensive to flatten a place of 3-4 kilometers so there are certain runway waviness permitted by the regulatory bodies so if you are within that it is acceptable to have a runway with such kind of waviness so you can see an example of spoilers deflected flaps deflected and this is a flap around okay then you can also have them like this which come in a very large way so you can see here for example many fighter aircraft just behind the cockpit because that is the place where you have a maximum drag total frontal area is exposed to this particular so imagine the load which comes on this air brake okay let us see a small click now now what I would like you to know is this is the component which is heavily loaded you will agree with that so for your information when we had MiG-21 aircraft in this country now it is almost obsolete there used to be a hydraulic air brake on MiG-27 on MiG-21 and the composites laboratory of IIT Bombay Aerospace Department was given the task of creating a composite air brake okay so the first carbon fiber stressed structure to fly on any military aircraft in India was a speed brake designed by Professor Luckard and his team Department so when I was working in HAL I used to associate with Professor Luckard in installation and testing of this air speed brake before that all composite materials used on aircraft were only some hash door some covers maybe fin leading edge non-stressed parts only aerodynamic covering parts were not heavily stressed the first stressed component was a carbon fiber air brake I do not remember how much weight was saved it was a massive weight saving just by one component after that the MiG-27 air brake was also converted into a composite air brake