Lift on dives and climbs

[Ricardo RW]

It's known that a wing flying horizontal to earth will overcome gravity with lift that it exerts, so L-G=0 if L=G, that is, assuming steady flight and everything in equilibrium.

Lift is produced as the wind goes over and under the wing and with some positive angle of attack, right?

OK, so, what happens in a dive (or climb)…? Vertical of course, 90° or -90°

Applying the above stated, as wind passes over and under the wing, there’ll be lift, correct?

But as there isn’t a force opposing lift, and with basic vector sum, the plane, if observed from the side will have the tendency to deviate to the side the lift is pointing (L will not have an opposing vector as flying level) making some sort of parabola, as G starts to affect.

To counteract this effect some opposite elevator (forward stick) should be applied to maintain the dive or climb.

It’s that true aerodynamically or I am missing something?

TIA,

Ricardo.

[Ollie]

"OK, so, what happens in a dive (or climb)…? Vertical of course, 90° or -90°"
In vertical dive or climb, the aircraft changes pitch attitude so that the wing lift is zero. Read about it:
http://www.av8n.com/how/
And
http://www.av8n.com/how/htm/aoa.html
And
http://www.av8n.com/how/htm/aoa.html#sec-def-aoa

[Murocflyer]

There is no end to what can be learned from this Forum. Thanks for posting that link Ollie, it will keep me busy for days reading that.

-Frank

[peterangus]

Ricardo

<Lift is produced as the wind goes over and under the wing and with some positive angle of attack, right?>..............YES

<OK, so, what happens in a dive (or climb)…? Vertical of course, 90° or -90°

Applying the above stated, as wind passes over and under the wing, there’ll be lift, correct? >..............NO
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Let's say you have a stable 'plane with the elevator trim set to give level flight.

Apply down elevator to achieve vertical nose-down attitude, then release stick. Don't alter trim.

Model will commence a pull-out manoeuvre [that's what longitudinal stability does, automatically]. Wing will produce lift which will be balanced by centrifugal force from the pull-out.
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If you want to prolong the vertical dive, you must apply down elevator, however much is required to maintain the vertical trajectory. The elevator deflection will have reduced the wing angle-of-attack to the angle at which lift is zero.

[Ricardo RW]

Apply down elevator to achieve vertical nose-down attitude, then release stick. Don't alter trim....Will this occur even with a symetrical profile?

...If you want to prolong the vertical dive, you must apply down elevator, however much is required to maintain the vertical trajectory. The elevator deflection will have reduced the wing angle-of-attack to the angle at which lift is zero.Do this happen to acrobatic airplanes too?

Anyway, thank you for taking your time answering me.

Ricardo.

[Ollie]

"Will this occur even with a symetrical profile?"

The symmetrical profile is the same lift up or down with plus and minus angle of attack. At zero angle of attack the profile lifts zero ( zilch, nada, nothing).

"Do this happen to acrobatic airplanes too? "

The acrobatic airplanes use symmetrical profiles so that they fly equally inverted or right side up.

It is important to read again:
http://www.av8n.com/how/htm/aoa.html#sec-def-aoa

Reread till you understand that the aircraft flies with it's changing pitch attitude of angle of attack. Your plans don't tell how it flies except indirectly with lots and lots of aerodynamic theory.

[bardolho]

Correct me if I'm wrong, but it seems to me all of the above relates to a plane with positive stability.

The CG is usually positioned slightly forward of the CL, because this gives better stability. This means that you'll need a little up elevator to maintain level flight.

This is not true with a wing with the CG too far aft. In this case you need down elevator to maintain level flight, and the effect of vertical flying would be the opposite of that mentioned above. This plane however is unstable and very hard to fly.

If you could manage to find the perfect balance I suspect you could make the plane absolutely neutral. However I'm not sure a plane would be stable in this condition...

[Ollie]

When the wing produces lift (non-zero) the angle of attack is not zero. The stability can be positive or negative but, the lift depends on angle of attack not stability.

To understand aerodynamics, forget myths.

On the other hand, the birds (and some R/C fliers) fly beautifully and have no idea of aerodynamic theory. The hummingbirds and insect have flown for millions of years but only in a couple of years have the scientists understood that mode of flight.