How much lift is necessary to overcome drag? How can I convert lift & drag to gliding performance?

Question

If I have a lift value and its corresponding drag value how can I convert them to performance in the glide. If the ratio of lift:drag is 1:0.066, how far can the animal travel? Any kind of equation (and preferably some kind of source) would be great, or even just a book or paper I can look it up in! Thanks!

Answer 1

Looks like your animal has a pretty good Glide Ratio. For every km it falls, it is 15 km ahead.

The equation, if you can call it that, is quite simple Glide Ratio = L/D.

Answer 2

You can't really CONVERT lift to drag. Lift is lift and drag is drag. The L/D ratio that you mention is just that, a ratio. I never thought that using lift and drag in a ratio like that was very effective because it seems confusing. Because what it really is is feet lost/feet traveled. In your example, the animal would glide 15 feet forward for every one foot loss in altitude roughly.

Answer 3

you can't compare lift to drag, they are seperate values.  Actually the opposite of life is gravity. The opposite of drag is thrust.  When these 4 forces are in balance, you have steady flight.  

If one force is dominant, that determines what the aircraft is doing....if thrust is greater than drag, the aircraft is accelerating.

Answer 4

The ratio of lift to drag (really of lift coefficient to drag coefficient) is the same as the glide ratio.

The lift coefficient is the ratio of dynamic pressure (the pressure of the moving air) times wing area to lift.  You could think of it as the 'efficiency' of the wing in turning dynamic pressure into lift.

Dynamic pressure is 1/2 times air density times airspeed squared.

Lift is necessary to overcome WEIGHT, not drag.  Thrust is needed to overcome drag in level flight; in gliding flight, potential energy (altitude) is traded to overcome drag.

Answer 5

1:.066  ÃƒÂ¢Ã‚‰Âˆ 15.2: 1.

about 15.2 times the elevation of the animal.

Answer 6

The aerodinamic force applied to a body is actually one, but can be divided into 2 components because easier to consider...

Lift is the component direct Upward, Drag is the component directed backward. they are both forces so both measured in newton(in metric units, or for example pound-force in anglosaxon units) but they are directed in different directions, so lift can't overcome drag.

If you want to know how far can an animal  glide, this problem is almost the same of a glider.

This formulas are approximations because for example you don't consider the initial transient and you consider the parabolic "polar" approximation(drag is composed by parassite and induced drag, parassite is constant, induced is proportional to lift^2),

a further approximation: you consider the air calm, causing probably not big differences for example for flying squirrels, but probably enormous differences for albatros,eagles,hawks etc...

The gliding range is altitude* efficiency.

efficiency is lift/drag(more propely the ratio Cl/Cd, but it's the same), so gliding_range=altitude * lift / drag.

1 / 0.066 = 15.15 this mean that this animal is quite efficient(this efficiency is almost comparable to the efficiency of airliners and probably bigger than most military fighting airplanes, but smaller than modern gliders/sailplanes that can even reach efficiency of about 60).

an efficiency of 15 mean that that animal can glide for a distance of 15 times the altitude . for example can glide for 15km jumping from 1km of altitude.

Answer 7

This may be helpful to you:

http://www.first-to-fly.com/Adventure/Wo...