Thrust to Weight Ratios

[Stoney]

Lift can only equal weight at 1G.

If I understand you you're saying that lift from something like the Bernoulli effect could cause some lift and induced drag at 0 AOA?  Unless you're taking about absolute vs geometric AOA isn't 0 Cl the definition of 0 AOA?

Only if you're talking about the effective AoA (or geometric AoA as you put it).

[Stoney]

Ahh I understand your disconnect Stoney.

G loading by definition is Lift / Weight.  This applies in any attitude. So  there is not any lift (BY DEFINITION) being generated at zero g. If you assume some lift, then we would not be at Zero g.

DISCLAIMER.

The above only is the basic all the minor forces going into the calcs of lift needed such as offset thurst, CG , wing twist ......


HiTech

I think I might be getting tripped up by the whole "gravitational G" vs. "G load".  I tend to forget those aren't the same.

[Midway]

  <leaves the brainy think tank room now> 

[FLS]

Only if you're talking about the effective AoA (or geometric AoA as you put it).

I think I mean the opposite. Geometric AOA is aligned with the chord line. Absolute AOA is 0 AOA = 0 Cl. So wouldn't effective AOA be absolute AOA?

[hitech]

I think I mean the opposite. Geometric AOA is aligned with the chord line. Absolute AOA is 0 AOA = 0 Cl. So wouldn't effective AOA be absolute AOA?

As far as I know AOA is always measured against cord line when plotting CL curves.

Unless the wing is symmetrical, (normally only on planes designed for aerobatics) almost all wings have CL 0 at  a negative AOA.

HiTech

[Stoney]

As far as I know AOA is always measured against cord line when plotting CL curves.

Unless the wing is symmetrical, (normally only on planes designed for aerobatics) almost all wings have CL 0 at  a negative AOA.

HiTech

FLS, I've never seen the term "geometric" AoA before.  Effective AoA is the angle of attack created when incidence and camber are included and compared to the relative wind.  Absolute AoA is the angle of attack when compared to the zero-lift AoA of the wing when incidence and camber are included.

@HiTech, yes, since almost all aircraft use cambered airfoils, the zero-lift AoA will be negative. 

[FLS]

Here's a reference for geometric AOA.

http://www.av8n.com/how/htm/aoa.html#sec-raoa-aaoa

[Stoney]

Got it FLS.

[Baumer]

Ahh I understand your disconnect Stoney.

G loading by definition is Lift / Weight.  This applies in any attitude. So  there is not any lift (BY DEFINITION) being generated at zero g. If you assume some lift, then we would not be at Zero g.

DISCLAIMER.

The above only is the basic all the minor forces going into the calcs of lift needed such as offset thurst, CG , wing twist ......


HiTech

I don't think this statement is technically correct Hitech.

The definition of G loading creates a "divide by zero" mathematical situation at 0g. That doesn't mean that there isn't any lift, just that the denominator is zero.

Think of it this way, if I hold an apple in my hand and ask you to divide it by zero, does that make the apple disappear?

[FLS]

Baumer G loading is the relationship of acceleration to free fall. No acceleration is 0 G is free fall. If you hold an apple in your hand you are accelerating it to 1 G. If you remove that acceleration the apple has no lift and at 0 G it disappears from the spot it occupied.

[Baumer]

FLS Sorry I was talking about load factor as Hitech posted about.



where:
n= Load Factor
L= Lift
W= Weight


BTW a falling apple (on earth in a normal atmosphere) will have lift and aerodynamic drag as it accelerates towards the ground.

[FLS]

FLS Sorry I was talking about load factor as Hitech posted about.

(Image removed from quote.)

where:
n= Load Factor
L= Lift
W= Weight


BTW a falling apple (on earth in a normal atmosphere) will have lift and aerodynamic drag as it accelerates towards the ground.

So was I. I was having fun with the apple. It does disappear.    Load factor exists only when it is more than 0 G. When there is no acceleration there is no relationship.  You're saying there is a problem with the definition of load factor for the case of no load and no load factor. That doesn't seem like a big problem.

[Baumer]

That's fine, but just to be clear, there is lift (and induced drag) on an aircraft in a zero g maneuver.

[FLS]

I think that was Stoney's point too. I don't think anyone is disagreeing with that. It's probably more of a difference of pilot's perspective vs engineer's perspective and understanding which perspective everyone was coming from. There is stuff going on that to the pilot is negligible. I believe that's why Hitech was specifying 0 net lift and basic forces.

[Seanaldinho]

These are the times I enjoy feeling stupid. 

BTW please no one divide by zero... I enjoy this world