Y-component of the force vector in turning flight

[Xorda]

Hello,

I have a question:
Why is the y-component of the force at turning flight equal to the weight force?

Here, Fs is equal to Fg. But why?

I tried to explain it myself but I didn't get it

 

[Ibix]

What happens to a body if there is a net force acting on it?

 

[Xorda]

It will accelerate

 

[Ibix]

Right. So what would happen to the plane if those vertical forces weren't equal and opposite?

Does the pilot have any means to control $F_s$?

 

[Xorda]

There would be a loss of altitude if Fs is lower than Fg and if Fs is greater than Fg the plane would gain height. I think I got it now XD

 

[kuruman]

If the pilot controls the plane so that it is flying in a horizontal plane, it has to be.

 

[Ibix]

There would be a loss of altitude if Fs is lower than Fg and if Fs is greater than Fg the plane would gain height. I think I got it now XD

Right.

There's nothing in the model you've given that will let you determine that $F_s=F_g$. We just note that the pilot can choose to do that, and we assert that she's doing it in order to have the plane conveniently flying level for this example.

 

[Xorda]

Thanks for help :D

 

[sophiecentaur]

The term 'equilibrium seems not to have been used here, yet. If the plane's height is constant then it's in vertical equilibrium. @Xorda I think you were looking for an aerodynamic answer rather than a straight Mechanics approach.

 

[jbriggs444]

The term 'equilibrium seems not to have been used here, yet. If the plane's height is constant then it's in vertical equilibrium. @Xorda I think you were looking for an aerodynamic answer rather than a straight Mechanics approach.

In which case, an answer would be that the magnitude of the required lift force $F_a$ during the turn exceeds the lift force $F_s$ which would be required for ordinary level flight.

In order to increase the lift force one can increase the angle of attack. But to maintain airspeed one will then need to throttle up. Otherwise, increased induced drag and parasitic drag will both reduce airspeed.

I am not a pilot, but my understanding is that one is trained to (counter-intuitively) use the throttle to control altitude and the stick to control air speed.

 

[sophiecentaur]

I am not a pilot, but my understanding is that one is trained to (counter-intuitively) use the throttle to control altitude and the stick to control air speed.

The diagram in the OP assumes that the pilot has done the right thing with the throttle. It doesn't tell the pilot what to do to achieve equilibrium because all planes are different. It's only a small part of the description of the whole situation.