Steep Turns

[nosehair]

Here is a picture of an airplane in straight flight. The dihedral is exaggerated for clarity:

Here is the same airplane in a left bank:

Ding! Your lower picture "in a left bank" made the light go on in respect to the 'rolling moment' you enlightened me with, which I had not considered.

So, the 'rolling moment' occurs by the additional lift obtained as the left wing lowers, thereby obtaining additional AoA, thus lift, thus 'rolling moment', whilst the other wing is 'losing lift', as a result of the decrease in AoA from the raising. This would occur in a perfectly coordinated roll, and would be more so if the initial roll is not coordinated and the wing slips down resulting in an even further increase in AoA. huh?

 

[tgrayson]

So, the 'rolling moment' occurs by the additional lift obtained as the left wing lowers, thereby obtaining additional AoA, thus lift, thus 'rolling moment', whilst the other wing is 'losing lift', as a result of the decrease in AoA from the raising. This would occur in a perfectly coordinated roll, and would be more so if the initial roll is not coordinated and the wing slips down resulting in an even further increase in AoA. huh?

What you're describing is real, but is typically referred to as "damping". When you deflect ailerons, you get the lift differential that produces an acceleration in roll (which I have not depicted), but as the rolling velocity increases, the effect you described occurs and slows the acceleration in roll until it stabilizes as a particular roll rate. Once a roll rate is established, lift on both wings is again the same, which is why there is no acceleration in roll, only a constant roll rate. To stop the roll, you will have to reverse the ailerons.

What I have attempted to depict is an airplane in a steady turn, a constant bank, and to show that the orientation of the wings, by itself, does not produce a rolling moment.

To show how the actual dihedral works in a 2-dimensional diagram is very difficult, which is why it took me years to "get it". A yaw or a skid is a rotation around the vertical axis and basically points one wingtip into the relative wind more so than the other. Since that wingtip is raised relative to the root, this exposes more of the underside of the wing to the relative wind, producing an increase in AOA.

 

[nosehair]

Thanks, tgray; I have been worrying with this explanation for some time now, since they took it out of the FTH. I can see the FTH explanation was too simplified.

 

[exleardriver]

i just love teaching aerodynamics...

c'mon guys...let's get back to regs, procedures, operational considerations...move along..nothing more to see here!

 

[meyers9163]

Ding! Your lower picture "in a left bank" made the light go on in respect to the 'rolling moment' you enlightened me with, which I had not considered.

So, the 'rolling moment' occurs by the additional lift obtained as the left wing lowers, thereby obtaining additional AoA, thus lift, thus 'rolling moment', whilst the other wing is 'losing lift', as a result of the decrease in AoA from the raising. This would occur in a perfectly coordinated roll, and would be more so if the initial roll is not coordinated and the wing slips down resulting in an even further increase in AoA. huh?

WOW! haha too much information on this.... Hell if a student is going to ask you these types of questions and want this much detail best of luck!