Hi, everyone, and welcome to these first class in this section of aerodynamics, in this case, we
will be studying forces which are acting on an airplane.
So here we presented are the basic most basic forces that you may encounter on an aircraft.
There is, of course, the lift which is provided by the wings and allows the aircraft to actually move
up.
Then does the weight, which is related to the mass of the whole aircraft.
This is the thrust which is generated when the engines push the air in the opposite direction.
And this is the drag, which is an opposing force related to the viscosity and the conditions of the
flow around the wings and around the aircraft itself.
The drag emerges as a consequence of the relative speed between the aircraft and the surrounding air.
So let's see a bit more of the dependencies of these forces with respect to the flight conditions.
So the lift depends on the velocity.
Actually, it depends on the velocity squared.
OK, and the wing surface, the drug in the same way as the lift depends on the velocity and the wing
surface of the aircraft.
But it also depends on the drug derived from the fuselage and from other components of the aircraft.
The wait is fixed.
OK.
As this is different from with respect to the left and Iraq, since this is a variable what one would
say a constant which is simply fixed.
OK.
And the thrust depends on the intentions of the pilot knows, for instance, that the thrust.
Is actually quite exhaustive to analyze.
Right.
But the idea is that the party has control and you can think of the thrust and the weight as the input
variables of this problem, whereas the lift and the drug emerge as a consequence of the velocity at
which the airplane is flying, OK?
And basically, you can see that these four forces interact with each other in this schematic shown
here.
So one important thing to take into account is, for instance, the case in which we look for equilibrium,
equilibrium, what it means is a cruising condition, right?
So when the aircraft is flying in cruising mode and in other words, what this means is that all forces
acting on the aircraft are balanced.
This would suggest an equilibrium type of flight.
However, as you may know, Newton's second law states that if you have a difference in forces, say
that lift this over here, right?
It's actually bigger than wait, for instance, the result will be that the aircraft will move upwards.
Right?
So the idea here is that if you want an equilibrium, a nominal cruise flight, you need these two forces
to be balanced, but also you need the thrust and the drug to be balanced.
OK.
So take, for instance, on the opposing point of view, right?
The case in which the weight is higher than the lift.
What would happen is that the aircraft would, you know, would.
Experiment, a downwards force, which is the difference between the weight and the lift.
OK.
So really, depending on the operation that you need, the pilot has the capability of increasing the
thrust, therefore increasing the drug and the lift, right?
So pretty much you can sum it up as it really depends on the pilot's intentions.
And by controlling the thrust, which is this variable that we can control as pilots, right then we
can have an impact over the values of lift and drag.
And if we manage to balance all of them, we will have a nominal cruise flight.
And my question to you would be, what do you think would be the case in the case of takeoff?
Right?
The takeoff would probably suggest that the thrust has B has to be higher than the drag, right, so
that it can accelerate.
And also that the lift is higher than the weight because otherwise it wouldn't take.
Right?
What if we want to increase altitude?
Should the lifts be bigger than the weight?
Should it be the other way around?
What about reducing speed?
How would you do that?
And especially taking into account that as pilots, we only control the thrust?
OK, so these are some interesting questions to take into account.
And if you more or less understand all of these topics, then you're probably fine in terms of the the
basics.
Topics that we need to know in terms of aerodynamics, OK?
So with this, I believe that we can move to a next class.
Thank you.