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 ok. 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, empennage or the tail and then we will go to miscellaneous. Now, this miscellaneous word is a very dangerous word, ok. Miscellaneous can mean anything.
So, let us define very soon what do you 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 axis 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's look at each individually. The rotation about lateral axis is called pitch. This movement changes the lateral 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 as a 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.
In this presentation and also in the entire course we are going to use these three axes and these three pitching moment, these three moments pitching, rolling and drawing you have to appreciate what they are and remember this particular video, right. So the first component of the aircraft that I want to touch about is the wing which is the major component, okay. 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 moves and which parts remain stationary and we will see if we have missed something, okay. 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 a 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, the one on the right 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 take off and landing performance but there is also some other purpose of those. So first we will look at the wing and the controlled surfaces on the wing ok.
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 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 screws. 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? Anybody 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? Yes. No, no, no we do not have inboard outboard ailerons for a backup purpose. Please pass on the mic.
Why is it 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 a inboard aileron coupled to the inboard of the other side, each wing has a 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, what is your point of view? Small and large changes 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 loads 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 a 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 edge 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. In a 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 movement to go more than 90 degrees and then you level up and after leveling up you are back, okay. Alright, let us see the next.
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 ok. So what is it? Location is the trailing edge inboard to aileron. Ailerons are always more than outside outboard of 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.
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. are going to deflect it, they are going to need 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 flares. Right now I am going to just show you some pictures, okay. This is a simple hinged flap like my wrist is a simple hinged flap, that is it. The whole thing moves down across a 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, correct.
Where remember one thing in an aerospace 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 flaps, 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 percent of the wing forms it, top surface is stationary, lower surface moves, okay, right.
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.
This is not necessarily 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 too not one piece there is one small piece behind which moves independently. You can have double slotted foul of left, you can have triple slotted foul of left.
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 3 slots, okay. I would really like to hear from you if there is some aircraft which has got quadruple or penta slotted Fowler flaps. I only know of 3, maximum 3. And also identify one aircraft which has got a triple slotted fowler flaps 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 turn to say 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 we will have a nice list. So in my next presentation next year I am going to just put a table saying these are the aircraft. have got a triple slotted Fowler flap. So one requirement is anything more than three slots in the trailing edge only ok.
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 aerofoil 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. Ok. Slotted flaps are flaps where you create a air gap between the two moving parts or the three moving parts. This is an example of double slotted Fowler flaps both inboard as well as outboard ok.
So, what you do is you create a small gap. And we will see later on what happens there right. Moving on so ailerons give you roll control.
Flaps give you lift improvement. What about aileron plus flap? What will you call it? Flap-a-ron. So we have something called as a flap-a-ron 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 pay egg free that is the offer ok that is a flap around. So here is a flap around which you can see and this is the images taken from actual flight for some aircraft. It 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 ok.
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.
So, 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 is already reflected little bit, little bit it 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 moment.
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 flaperon keeps moving because it is meant for minor corrections ok. So this is the function of the flaps.
They are down during takeoff and they are giving you enhanced. Lift ok. 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 put 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 increase.
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, alright, leading as 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? It is round in shape and a flat, it will have a flat bottom. So, you are saying it is round in shape and has 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. NACELE 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 a engine nacelle. The engine nacelle is not circular, okay. 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, okay. 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 flight, okay. 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 percent higher drag can be a real problem and the competition can actually win over you because you have got 1 percent 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 flap in the leading edge is called as a slat, just a name. It has got a similar aerodynamic shape but it's called as a slat. So this is a fixed type slat. Nothing moves here.
It's like this right from the beginning to the end. This is the aircraft configuration. This red colored device is fixed.
The gray 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 This is a fixed flat, okay. There are members which support it, okay. Why do we need this thing?
We will come back later. In some aircraft, we have a retractable flat. That means we have flats which can be retracted, okay.
We do not have the file here. But this flat 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. You can 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. 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. So they are called as a Kruger flap.
All these videos are easily available on YouTube, okay. 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...
Deployed. 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 ok. They are also called as Cuchman carrots in respect of Cuchman who was the person who did the aerodynamic design of the Concorde 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 this 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 us see the whole thing working together again. So now this is on the ground. Notice what happens, this is testing on the ground. These are the flap track fairing.
We will just proceed ahead. I will try to show it some other time. These are your air brakes.
These two on the back. These are the few large 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 BAE 146 landing.
Notice the drag on the back. They open up. There are no spoilers here, okay. 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 the 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 aircrafts just behind the cockpit because that is the place where you have a maximum drag. Total frontal area is exposed to this particular thing.
So, imagine the load which comes on this air brake ok. Let us see a small click. Now, what I would like you to know is this is a 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 metallic air brake on MIG 27. Amit 21 and the composites laboratory of IIT Bombay Aerospace Department was given the task of creating a composite air brake ok.
So the first carbon fiber stressed structure to fly on any military aircraft in India was a steel brake designed by a Professor Lathkar and his team of our department. So when I was working in HAL, I used to associate with Professor Lutgert in installation and testing of this airspeed brake. Before that all composite materials used on aircraft were only some hash door, some covers, may be fin leading edge, non-stressed parts, only aerodynamic covering parts which were not heavily stressed. The first stressed component was the carbon fiber air brake.
I don't 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. Thank