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## Main Question or Discussion Point

Dear all,

I'm a RC-airplane pilot with basic understanding of physics.

Recently I've been studying basic aerodynamics and I think I understand the basics.

However, I don't entirely understand why an airplane performs a loop and I can't find any references about it. Here's my current breakdown:

- for practical reasons, let's have a glider in a vertical dive

- nil wind

- we'll assume that the glider is flying at terminal velocity, so that weight and drag are neutral

My understanding of the situation:

- resultant of weight and drag is zero

- the wings still produce lift, perpendicular to the relative wind, so the lift vector is parallel to the horizon

- there is no opposite force to the lift

What happens (in a very short time frame, of course):

- the lift starts pulling the airplane

- center of mass moves further down and to the side (due to lift)

- the movement perpendicular to the wings generates drag on the horizontal tail, which in turns generates troque an rotates the plane over pitch axis

- because of this rotation, the airplane doesn't change the angle of af attack

- at the end of the time frame the situation is exactly the same as at the beginning, so here we go again.. and again.. and we perform a loop! (I know, the weight vector changes the direction and it needs to be accounted for)

Are my assumptions correct? Could someone provide accurate information?

TIA

Jernej

I'm a RC-airplane pilot with basic understanding of physics.

Recently I've been studying basic aerodynamics and I think I understand the basics.

However, I don't entirely understand why an airplane performs a loop and I can't find any references about it. Here's my current breakdown:

- for practical reasons, let's have a glider in a vertical dive

- nil wind

- we'll assume that the glider is flying at terminal velocity, so that weight and drag are neutral

My understanding of the situation:

- resultant of weight and drag is zero

- the wings still produce lift, perpendicular to the relative wind, so the lift vector is parallel to the horizon

- there is no opposite force to the lift

What happens (in a very short time frame, of course):

- the lift starts pulling the airplane

- center of mass moves further down and to the side (due to lift)

- the movement perpendicular to the wings generates drag on the horizontal tail, which in turns generates troque an rotates the plane over pitch axis

- because of this rotation, the airplane doesn't change the angle of af attack

- at the end of the time frame the situation is exactly the same as at the beginning, so here we go again.. and again.. and we perform a loop! (I know, the weight vector changes the direction and it needs to be accounted for)

Are my assumptions correct? Could someone provide accurate information?

TIA

Jernej