Hi, everyone, and welcome to this new class in which we will be discussing high lift devices in aircraft.
As mentioned in previous classes, we need the lift to be roughly equal to the weight in order for the
aircraft to have a balanced flight.
Assuming a constant weight, the lift would also be constant for this equilibrium to be true.
Coming back to the equation of lift and assuming that the lift is roughly equal to the weight, we can
substitute the lift by the weight in this equation.
Now, the left part of the equation, the weight is constant.
This means that the right part of the equation will also be constant, which implies that all of these
variables multiplied will be constant.
So if all of these parameters have to be combined a constant, then this means that if the velocity
is, say, relatively small, one of the other parameters has to be high.
Let us analyze the parameters one by one.
First, the density of the atmosphere of the air surrounding the aircraft is constant.
It only depends on the composition of the app and its conditions.
The surface of the wing can be considered to be fixed constant.
This leaves us only with one variable the coefficient of lift.
So if the airplane is moving at a low speed, then the coefficient of lift must be high so that the
total lift equals to the weight of the aircraft.
This implies that at low speed conditions, we may need to have a very high coefficient of lift so that
the aircraft is effectively in equilibrium.
Due to this reason, high lift devices are required so that the aircraft can be balanced even if flying
at low speeds, or in other words, by putting high leave devices on aircraft.
We can achieve a balanced flight at low speeds, for instance, using highly if devices.
The aircraft can take off at lower speeds.
It can also land at lower speeds so highly if devices are particularly useful during takeoff and landing.
This also implies that runways can be designed to be smaller shorter, since aircraft will be able to
takeoff at lower velocity due to high lift devices, and therefore they won't need as much runway length
to achieve that speed.
The same argument can be made in the case of moving slowly when landing, therefore when touching the
ground.
Since the aircraft will have relatively small speed, it will have to slow down to zero from a relatively
small speed, which implies it can slow down even in smaller runways.
This is clearly the case for aircraft taking off and landing from aircraft carriers.
So in conclusion?
High live devices allow for a balanced flight at low speeds.
To summarize, high level devices allow us to have a higher coefficient of lift right, which in a balanced
flight means that the speed of the aircraft can be relatively low and still the aircraft will be balanced.
So note that we could also just increase the angle of attack to have a higher coefficient of lift and
therefore fly in a balanced way at low speeds, right?
However, at high angles of attack stolen to and we do not want the aircraft to be unstable or to fall
down when taking off or landing.
Increasing the angle of attack is not enough, so this image illustrates how high lift devices will
be able to change the coefficient of lift with respect to the angle of attack.
Two types of highly if devices are indicated flaps and slats.
No.
First of all, we will discuss flaps flaps of high lift devices typically found on the aircraft, which
increase the coefficient of lift over the wing.
So this is the normal curve for of a plane airfoil, as we have discussed previously, and this in green
is the curve.
If we introduce flap, so if we include this additional surface element on the trailing edge of the
airfoil, the effect of the flap is that the curve, of course, is moved upwards or towards the left.
By doing this at the same angle of attack, the airfoil with the flap will be generating more lift.
The second type of high level device is the slat, which is a surface which is added on the leading
edge of the air foil to enhance the flow around the upper surface.
The black curve with dots illustrates the effect of having slats.
Notice that the coefficient of lift is not increased for lower angles of attack yet it does not fall
or stall when the aircraft is flying at higher angles of attack slats aid in avoiding stone.
The combination of both technologies is shown in red, where the coefficients of lift is moved upwards
and high angles of attack are also a possibility.
Increasing the coefficients of lift let's not discuss flaps the technology in more detail.
Flaps are basically additional surfaces which are typically found below the wing and can be moved towards
the back of the wing synthetically right, creating a larger airfoil with a more pronounced kayumba.
There are different sorts of configurations of flaps, including plane flaps, split flaps and particularly
fouler flaps.
Fowler flaps are the most common, and they look like smaller wings attached to the rear of the main
wing.
They are aerodynamically efficient and are widely used in civil, commercial and military aircraft,
so flaps force the wind to move downwards a downward edge of the air.
This, in turn, generates necessarily a lift as a reaction of this change in direction of the wind.
So even at zero angle of attack, like in this case, the air will still be forced downwards.
This pushes the coefficient of lift curve right upwards, meaning that the air for it will generate
more lift.
So if this Air Force did not have a flap right, we would see a lift proportional related to the chamber
of the airfield, as well as the angle of attack, of course.
However, by putting this flap in, the air is forced more downwards, therefore generating more lift.
It's a clever way of changing the geometry of the wing.
Another interesting technology mentioned are the slats.
The slats are located at the front of the wing and aid in keeping the flow to move fluently around the
upper surface of the wing.
The reason why stall appears at high angles of attack is because the flow becomes turbulent.
We will discuss further this a bit more in coming classes, so slats basically keep the flow from becoming
turbulent.
This helps in delaying this stall condition as a function of the angle of attack slots divide the air
located on the leading edge into two.
Therefore, playing with the way in which the flow interacts, which itself the slot is the space located
between the slat and the wing.
This is a clever way of making sure that the flow does not become unstable, but rather converges smoothly
on top of the F1.
So technically a slot.
What it is doing is that it is keeping the flow laminar instead of turbulent, which is optimal for
live generation.
So slats do not push up the coefficient of lift, but help in delaying the stall condition at high angles
of attack.
So this is what flaps typically look like on commercial aircraft.
OK.
You may have noticed them at some stage.
Not that in these images, flaps are activated, meaning that they were mechanically separated from
the wings right of the, you know, by means of the hydraulic system.
So this photo is quite interesting because you can see the flaps on this part over here all along the
surface, but you can also notice that there are holes, right?
Physical holes between the wing and the flap, which is what we saw actually and can be expected in
fouler flaps, right?
The image on the right clearly illustrates the location of the flap, but one can also see the spoilers
in action.
So spoilers literally spoil the flow of air around the wing by cutting its flow.
This will increase the drag because they are interfering with the flow, but they will also reduce or
spoil the lift generation.
It is a way to slow down the aircraft, OK, particularly when landing.
So this would be the spoilers.
The South is flaps, and one can also see the guide flap tracks, which are the tracks that allow for
the flaps to move from below the wing towards the rear of the wing.
OK.
Notice that in the Boeing 747, there are several levels of flaps, right?
They are divided into several sections now.
All flaps are different, right?
However, there are some properties which are common.
This is a design consideration really taking into account the flight conditions and technology required
for them in the case of the 747.
I actually like it because it's, you know, the flaps are very distinctive and you can also see identify
the slats of he actually.
So slats can be seen on the leading edge of the wing.
As we mentioned, they are on the leading edge of the wing and they just provide a puff for the wind
to go from the bottom, from the leading edge, from the bottom right towards the top of the wing.
And in order to increase the laminar flow on top of the wing and to avoid the detachment of the flow,
the appearance of turbulent flow.
Right.
So here you can see, for instance, the difference between slats when they are operating in this part
of the here, right?
And when they are closed.
So this is the slat configuration that can be found on the commercial aircraft.
And I believe that this is quite clear.
OK, we discussed flaps.
We also discussed slats and we mentioned also spoilers and the glider flap tracks.
All right.
OK.
So I believe that we can now move to the next class.